What's the precise meaning of "landing south (north, east, west)" in STARs? "JetBlue six zero two leaving flight level two one zero descending via the Ivane Two arrival landing south."

Does "landing south" here mean the aircraft will be landing on the runways north to south?

"Landing south" means the planes are facing south as they land. Depending on conditions, they could come from the opposite end of the runway, and would be "landing north." This is also referred to as "south flow/operations."

If you look at a chart for the IVANE FIVE shown below, you can see why this is important. The runways at KCLT are primarly oriented north/south. The aircraft will enter the approach at MAJIC from the northeast. If landing south, the arriving airplane will fly IVANE BABZE HEELZ and needs to be at 6000 feet when they reach HEELZ north of the airport. Approach control will then turn them south to land. If landing north, they will fly from IVANE to GIZMO and follow the approach down to the south, and don't have to be at 6000 until they get down to ESENE. After reaching JATAB approach turns them north to land.

Telling the pilots which direction they will be landing lets them know which route to follow on the approach and helps them plan their descent. If approach hasn't provided a runway yet, they can also know which runways they can plan for.

Source. This is the best I could find for the IVANE arrival. The MAJIC ONE isn't RNAV, the CHSLY THREE would seem to be the applicable RNAV procedure from the northeast.


Can military aircraft send out false ADS-B tracking information? Can most military and VIP aircraft out of Andrews AFB transmit false ADS-B signals?
Here is the ADS-B tracking of Navy P-3 Orion that seems to be violating Iranian air space tonight if the ADS-B is correct. An Iranian fighter was launched heading in it's direction but did not approach it. Two nights ago I was watching on globe.adsbexchange and flightaware the tracking of AF1 was transmitting. It was about 2 miles out from the air field for a landing and the ATC tower noted to ground crew VIP traffic is 10 miles out. It showed it landing when in fact it was still in the air. I know they are allowed to turn off their ADS-B anytime they need to for security reasons.

It is certainly possible, and also happens with some regularity. Here is an article discussing a recent USAF RC-135 flight over the South China Sea in which the RC-135 changed it's Mode S identifier to that of some Malaysian-registered plane.

At some point, the plane’s Mode-S number suddenly changed, from AE01CE to 750548. That’s the ICAO number for an unknown Malaysian aircraft. The RC-135W, call sign RAINY51, then flew a racetrack pattern between Hainan Island and the Paracel Islands, an archipelago in the South China Sea that China claims, but whose ownership is in dispute.

https://ph.news.yahoo.com/u-spy-plane-impersonates-malaysian-130000120.html
Relevant twitter thread linked in the article, with ADSB Exchange screenshots
https://twitter.com/steffanwatkins/status/1303776525083381760


Can the back tail of an airplane move the neutral point backwards? I'm currently in the process of designing a prototype aircraft and since I don't have very much experience with this I have the following question: I know that the center of gravity of an airplane should be located in front of the neutral point (aerodynamic center) so it is self stabilizing. The problem with my design is that the main wings have to be in front of the center of gravity. To counteract that, can I design the back wings in a way so that the neutral point is moved behind the CoG?

Yes you can, the tail volume needs to be such that the neutral point shifts aft of the CoG. This answer has some details - positive lift from the tailplane, but it must never stall!

More details about tailplane design in the answers to this question. The absolute safest config at a wide range of CoG is the CoG in front of the Centre of Pressure of the main wing, and a downforce from the horizontal tail.


What is this fighter jet seen at Centennial Airport? This is my first post here! yay! Today I ate at the awesome "Perfect Landing" restaurant at Centennial Airport. My dad said he thought they were FA-18s but I honestly have no idea. It was awesome because we saw the pilots through the window of the flight crew lounge in their military suits. We also saw them go out with some little kids and their families to show them the jets while they were being inspected before takeoff. Really cool to see.

That is a Boeing F/A-18E Super Hornet.  The Super Hornet can be readily identified from legacy F-18s by its larger size, enlarged, hood-like leading edge extensions, larger flaps and flight control surfaces, and the rhombohedral shaped engine intakes to reduce the aircraft’s frontal radar cross section.  It’s tail insignia indicates that it’s a line aircraft with the United States Navy’s VFA-143 “Pukin’ Dogs” strike fighter squadron based out of NAS Oceania, near Norfolk, VA.


Is it possible to have V1 greater then Vr? According to wikipedia, decision speed ($V_1$) is computed taking into account the runway length (and other parameters). If an aircraft uses a long runway (one listed here), there may be enough runway available to stop an aircraft rejecting takeoff at high speed. Thus $V_1$ can be higher than usual, perhaps greater than $V_r$ or $V_2$. Is the situation where $V_1$ is greater than $V_r$ possible?

I think the answer is no.

If you think about V1 as primarily based on runway length, it is certainly possible for an aircraft to easily reach Vr long before reaching the "point of no return" as far as stopping distance is concerned.

However, you must also consider the meaning of Vr. This is when the aircraft is going to rotate. After rotation and leaving the ground, the distance required to still stop on that same runway increases significantly.  For this reason, maximum V1 is generally considered to be Vr (see this discussion).

In large aircraft, rejecting a takeoff after leaving the ground is generally discouraged, unless the pilot feels that the plane could be uncontrollable. It's much safer to continue the takeoff and fly for a normal approach. However, it can happen.

In smaller aircraft, it's more reasonable for the aircraft to take off and then land safely (I'm thinking a C172 on one of the low density altitude runways you linked to).


What does M mean in A400M Atlas? Atlas was the guy in Greek mythology that was literally carrying the world/planet in his shoulders. But was does "M" mean? Military? That's a guess, though...

Without the M, people would simply confuse the military cargo plane with the civil airliners that Airbus builds (e.g. A320, A380, etc).


What profile will a Boeing 737 NG follow after pushing the ALT INTV button? If one uses the ALT INTV button during a Climb or Descent in the Boeing 737 NG on the MCP, what profile (Speed/Path) will the AP follow in such a climb and/or descent? Is it the same as programmed in the CLB and DES pages of the FMC?

What happens when pushing the ALT INTV button depends on the currently selected mode. You can find a full description from the FCOM in this answer.

VNAV Climb: The aircraft will remain in VNAV Climb mode and will follow the profile as programmed in the CLB page on the CDU.
Cruise: The aircraft will start an early descent:

  Early Descent

  To start an early descent, use DES NOW prompt on the DES page. An early descent can also be started by pushing the altitude intervention switch.

  (1) DES NOW (VNAV PTH)

  With a VNAV path descent planned, VNAV starts an early descent at 1000 fpm
  and captures the idle descent path. VNAV uses FMC SPD for the autothrottle
  mode and VNAV PTH for the pitch mode.

  (2) DES NOW (VNAV SPD)

  With a VNAV speed descent planned, VNAV starts an idle thrust early descent.
  VNAV does not attempt to capture the VNAV descent path. VNAV uses VNAV
  SPD for the pitch mode and the autothrottle commands IDLE, followed by ARM.

(Boeing 737 NG FCOM 11.31.36 - Flight Management, Navigation - Flight Management System Operation)

So in this case it depends on the VNAV descent that is planned in the FMC. If you have an altitude constraint selected, the aircraft will start a descent at 1000 feet per minute and intercept the idle descent path. Otherwise it will immediately start the speed descent as programmed in the DES page of the CDU.
VNAV Descent: The aircraft will remain in VNAV Descent mode, but the idle descent path can change due to the deletion of an altitude constraint. Should this result in the aircraft no longer being on the idle descent path, the mode will change from VNAV PATH to VNAV SPD and the aircraft follows the speed programmed in the DES page of the CDU. The same thing happens when all altitude constraints are removed.
Any other mode: Nothing happens. The ALT INTV button has no effect on other modes like V/S for example.


Why do some aircraft have multiple switches for the landing lights? A question just popped into my mind: Why does an A320 overhead panel have 2 landing lights switches? What's the logic behind that? Why isn’t there only a single switch to turn on both landing lights?

On a dark morning preflight check, I can verify that the lights all work by turning each one on, one at a time, without leaving the flight deck. Less lifespan on the bulbs & less disruption to the ramp to have several quick flashes of light within a few seconds, than turning everything on, walking outside to observe everything, and then going back inside.
Plus, it's probably a hold-over from days of minimal automation (think, 727 Flight Engineer panel - now entirely replaced by automation & a few switches on the overhead panel) when each {whatever} had its own switch.
I could get creative & invent another scenario or two when I want "this" but not "that" light on, but the preflight is probably the best example of that.


What is the purpose of the fuel shutoff valve? Most GA planes have a fuel shutoff valve which I don't quite understand the purpose of. Does it cut the fuel flow with the mixture.
My theory is to prevent fuel flow at earlier stage for safety reasons?

It's both a maintenance and safety feature.

You need a way to cut off fuel flow to the engine compartment, either to work on the engine, or because of a fire at the engine, or because you are doing a forced landing and it helps reduce the risk of your entire fuel contents seeping onto your hot engine if you bend things a bit putting it down and a fuel line gets broken.

So you will always have a shutoff valve, and it's always somewhere upstream of the firewall.


Is it possible to power a very small jet using batteries? I have read a lot of answers on batteries powering large commercial jets, and how it won't work. However, for a small jet like the Honda jet, would it be possible for it to be powered completely by batteries?

On some scale, of course this works -- look up "EDF", Electric Ducted Fan R/C models of jet planes.  For something the size of a Honda Jet, you still likely wouldn't get the performance (and certainly not the range) that you might desire.  Go smaller, and something in the size range of a BD-5J/Acrojet, which originally flew on a very small engine, might support being converted to an EDF -- though the flight endurance would likely still be very short.

EDF would be suitable for a motor glider or self-launch sailplane, neither of which depend heavily on long power endurance for normal operation (but neither of which are expected to fly hundreds or thousands of miles at hundreds of miles per hour, like a Honda Jet).


How is/was RFID bag handling introduced in a baggage handling system tailored to barcodes? I have just seen Richard Hammond's Engineering Connections about Hong Kong Chek Lap Kok (built 1998) and afterwards, Big, Bigger, Biggest about London Heathrow Terminal 5 (built 2008).

Quote from Eng. Conn.:

  Hong Kong was one of the first airports to replace bar codes with RFID tags to track bags

Quote from BBB:

  Even such an advanced [baggage handling] system [as the new one in T5] still relies on good old-fashioned Bar Codescanners.

Which made me think: Bar codes are, as far as I know, standardized by IATA, so luggage can go end-to-end through a multitude of airports on one bar code ("check-through"), but I guess when the first airport switched over to RFID, there wasn't one for RFID, so there's a bit of a hen-egg problem. How did Hong Kong airport assure that all luggage passing through it had an RFID tag?

By printing them along with bar codes. RFID mode became operational in HK in 2005. Basically, the airport replaced the barcode only baggage tags with RFID embedded tags:

  Hong Kong International Airport (HKIA) today announced that all of its check-in counters can now print integrated radio frequency identification (RFID) baggage tags. The new tags, which combine an embedded RFID chip with a barcode, are replacing barcode-only baggage tags on an airline-by-airline basis.

Basically, the system reads both the RFID tags and barcodes.


What class airspace is depicted in the magenta colored area southeast of the Lake Havasu City, Arizona AIrport? What class airspace is depicted in the picture below within the wide magenta colored bar southeast of the Lake Havasu City, Arizona Airport (on the Phoenix, Arizona Sectional Chart)?  What are the vertical boundaries of this airspace?

By the legend, that should be "Class E Airspace with floor 700 ft. above surface that laterally abuts 1200ft or higher Class E Airspace"


Why don't airlines have in-flight video recordings like buses do? That way we could study plane crashes more closely, or terrorist hijackings, or resolve passenger disputes. Even buses in Ecuador have video cameras.(WARNING: shocking video)

Many airlines do in fact have inflight camera feeds for Cabin surveillance so I do not think the question is relevant to most major airlines anymore.

For a specific example, Emirates Airline employs the Cabin Video Monitoring Systems (CVMS) across its fleet of Airbus A380 aircraft. These Cabin cameras can be accessed by Cockpit crew through the System Display or the Cabin crew through the FAP (Flight Attendant Panel) and for any abnormal situation such as a hijacking/hostage situation on ground, the CVMS can be accessed on a laptop via the GSP (Ground Service Panel). Additionally, as mentioned above, they have landscape cameras installed for an external video feed but that is more of a feature for passengers.

The advantages of a CVMS in a hijacking/hostage situation such as positioning, identity, body language and weapons of the hijackers plus general operational advantages such as issues during boarding/offloading and other emergency situations such as an evacuation are great and not to be discounted.


How does a TACAN signal change with bearing from the station? In the TACAN system , how does a change in bearing , would translate to a change in the time (or frequency) domain.

I'll try to elaborate:

I'm aware , of the TACAN operation in general.

let's say that I'm 270 degrees (referance to north) and 180 degrees (referance to north) , how would this change reflect on a Scope or on a spectrum analyzer if at all (of course I mean in the analog signal).

Change in bearing doesn't change frequency. The ground station always transmits  pulses on a single assigned frequency. The illustrations in the link from @CrossRoads only show what would be seen by a receiver at 000 magnetic. For other bearings the whole envelope shifts while the reference bursts stay still. The antenna illustration shows reflectors on spinning drums that create an envelope whose phase difference from the reference bursts depends on bearing. My markup of the diagrasms in the link (MRBs are blue):


What's an "outrigger" for parking aircraft on a carrier? In this picture of the USS Intrepid (CV-11), there appears to be an aircraft parked with the tail hanging off the deck:

(Source)

The caption gives a clue:

  The U.S. Navy aircraft carrier USS Intrepid (CV-11) operating in the Philippine Sea in November 1944. Note the Grumman F6F Hellcat fighter parked on an outrigger forward of her island.

This "outrigger" appears to be some sort of triangular structure to partially support the aircraft's weight:

Further research, however, turns up no more information about this "outrigger." So:

What exactly was this device?
How was it used?
What's its history?
Who manufactured it?

You can see it a bit better in this picture:

(Source)

  In order to save deck space for operations, the smaller escort
  carriers like HMS Khedive used outriggers. The tail wheel is first
  affixed and locked to the rigger trolley and then the aircraft is
  pushed outwards and the wheels heavily chocked fore and aft of the
  wheels. Here one of Khedive’s Corsairs demonstrates the concept
  perfectly. Note that the Corsair has Type C roundels, indicating it is
  in the European theatre of operations.

They were effectively a simple way to save deck space with out enlarging the deck. There is another decent pic here and some spitfires on outriggers here

Based on the info here they can be found as far back as the late thirties

  It represents an F4B-4 positioned on an experimental outrigger aboard
  the USS Saratoga during the late 1930s. The Saratoga and several other
  aircraft carriers were selected to try out different types of deck
  outriggers for the Navy in the interwar era.


Could a big plane glide significant distances, same a ordinary glider (1000 km or about)? Seems that a usual glider is not limited by its glide descent rate and can fly much more than this. It uses air masses that move upward to gain the altitude.

Are these effects limited by the size of the plane?
Could an airliner gain altitude for free using these "upward blowing winds"?
Could an airliner glide 1,000 km?

No, there's no way an airliner can glide 1000km, this is because its wing is designed for fast cruising speeds, and it's much heavier compared to the lift generated than a glider. Gliders are light and have huge wings for their weight, which means they can get lifted by powerful air currents. An airliner is not going to be able to do that.

The longest glide of an airliner I know of was Air Transat 236, which glided about 98 miles (almost 160km) from cruising altitude to the Azores after it ran out of fuel. The captain was an experience glider pilot. That is really about the limit.

Keep in mind that there's nothing ordinary about 1000km in a glider! 1000km is a very long distance and you'd need a very good glider and a very experienced pilot in just the right conditions.


Linking equivalent airspeed with waypoints, altitude, time and speed Say I want to find out EAS and I'm given a time that a pilot will reach a waypoint that is "X" Nautical Miles away, an altitude & I'm also given a ground speed that is increased by a tailwind. Is it possible to derive equivalent airspeed from these factors.

My current state of research is as follows:
I know the traditional EAS equation is useless in this case as I dont know the air density and other equations I've looked at require the Mach number which I also can't obtain. Basically all the EAS equations I've found require a density or the Mach number and I'm not sure how to proceed.

No, it is not possible to derive EAS from the data provided.

  p=Actual density

  p(o) = standard Sea Level Density

  TAS = True Airspeed.

You can get to actual density from the pressure altitude and temperature (ISA+ or raw).  Without temperature, it is impossible to derive air density from pressure altitude; only estimates are possible.  For a more in depth derivation, this is a good source.


What's the difference between a "flight line" and a "tarmac"? I was at a conference where there was a discussion on ontology for assets.  There were two classification trees, one for assets on the flight line and one for assets on the tarmac.

What is the nuance between these?  Is it active aircraft vs. inactive aircraft?

The nuance is between aircraft that have been / will be flying imminently, and aircraft that are more than a few hours away from doing so.

Apron (U.S., ramp) is where aircraft refuel, load/unload, etc.
Flight line is, in the popular press, where aircraft are parked, maintained, and displayed.  This usage is duplicated by aeromodelling clubs, although their time scale is closer to minutes than hours. (Wikipedia claims, without substantiation, that flight line is the U.S. military term for tarmac, ahem, apron.)
Tarmac (U.S., asphalt) is a paving material, one possible surface for runways and roads.  It's not an aviation term.  Informally, it means apron: we hear about tarmac delays, never about flight line delays.


Where do all the bullets end up? When planes engage with guns, many of the shots are misses... what happens to the bullets? Do they kill people on the ground and damage facilities? Do we have any records of this happening?

Do they kill people on the ground?

Almost certainly a few do.
People struck by falling bullets are more likely to die than people shot directly. The chances of a particular bullet falling onto a person are very small but over the decades, many many bullets have been fired by aircraft.
Handgun bullets

Between the years 1985 and 1992, doctors at the King/Drew Medical Center in Los Angeles, California, treated some 118 people for random falling-bullet injuries. Thirty-eight of them died.
Bullets fired into the air during celebrations return at a speed fast enough to penetrate the skin and cause internal damage to other organs in the path of the migrating bullet. The bullet’s velocity required for skin penetration is between 148 and 197 feet per second. A velocity of less than 200 feet per second, which is easily obtained by a celebratory gunfire, is capable of fracturing bone and even causing intracranial penetration [4]. Spent bullets have the capability of reaching up to 600 feet per second during their downfall, and thus they have the ability to inflict damage to multiple body cavities [4]. The larger caliber bullets (ie, .45-caliber) reach a higher terminal velocity compared with the smaller caliber bullets (ie, .30-caliber), because of the proportion of their weight to their diameter [4].

From http://www.annalsthoracicsurgery.org/article/S0003-4975(06)00831-9/abstract

For those hit by falling bullets, the chance of the wound being fatal was far higher than a typical shooting. The hospital put deaths from regular shootings between 2% and 6%, while for those struck by falling bullets the death rate was close to one third.

From http://www.theguardian.com/world/2011/aug/24/how-dangerous-is-celebratory-gunfire

Aircraft rounds
These falling bullets were from celebratory gunfire, not fired from aircraft.
Aircraft cannon fire projectiles which are often much heavier than handgun rounds. If one falls on you, the likelihood of injury or death must be higher.

.22 Winchester magnum rimfire and .50 Browning MG rounds at same scale. source


How does the radio altimeter reading change with the bank angle? How does the radio altimeter reading change with the bank angle?

Following example:
Let's say, we're flying at 1000' AGL and a bank angle of 0° above a endless flat surface. The radio altimeter shows 1000' as well.
Now if we roll to either side to a bank angle of 10° and maintain 1000' AGL, what does the radio altimeter read now?

Does does the radio alt increase accordingly or is the radio altimeter adjusted to always face down?

I'm especially interrested in the way how Airbus handles this situation.

The Rad Alt will show the same value of 1000'.

The radio altimeter antennas provide a radiation pattern that covers at least +/- 15 deg in pitch and +/- 20 deg in roll, though most cover more - typically +/- 20 deg in pitch and +/- 30 deg in roll.

The transmitted signal fans out equally over the entire pattern area from the transmit antenna and is reflected back where it is received by the receive antenna. The returned signal is spread over a short period of time due to the varying distances the signal must cover. The closest point will be the first received. As the aircraft changes pitch or roll, the location of the closest point will move within the pattern, but the shortest distance will still be the same.

The DSP software also processes the signal to filter out smaller objects such as the approach lighting towers.


Why are airlines so concerned with checked baggage weight? Why is it that commercial airlines are so concerned with checked baggage weight, such that they charge extra just for the privilege of checking in a suitcase with a limited weight (e.g. 15kg), and then if you should go even a couple of kg over the limit, they charge quite a bit per kg?

My first guess is they see it as a way of making extra money, but is this the only reason?

The reason I'm so puzzled about it is that they don't seem the least bit bothered about the weight of carry-on luggage, not to mention the passenger's weight (e.g. I weigh about 70kg more than my daughter, yet our ticket prices are the same). And then the weight of the aircraft itself - e.g. an Airbus A320 weighs 42.6t, with a max take-off weight of 78t according to Wikipedia. So why are they so concerned about an extra 3-4 kg in the checked-in luggage?

Airlines do care about your carry-on weight and even your weight. Many have carry-on weight limits, which low-cost carriers usually enforce, weighing the carry-on and tagging it as cabin luggage. Full-service airlines rarely bother.

One reason they don't measure your weight is that most people wouldn't feel comfortable getting weighed in front of strangers, then charged for that. Only Air Samoa currently weighs each passenger and tickets them by weight. In the West, weight is a contentious issue, so an assumed average is used for passengers. Such assumptions have crashed small planes, and in special circumstances like sports charters, actual weight is used. Finnair weighed volunteering passengers to get a better sample.

Weight costs money to carry, and not just in fuel burn. Luggage shares its volume with cargo, which airliners from the A320 up are designed to carry in the hold. Lately, cargo tends to get become more profitable than passenger service. Electronics and other high-value items cost more in depreciation and time value to ship by sea and land than by air, creating massive demand for air freight.

The A320 is 42.6 tons empty, but that's not the number that matters. The number that matters is its 78 tons MTOW, and how short of that it comes after adding pax, luggage and fuel to the 42-ton OEW. That spare weight is money in standby cargo.

Giving potential 175 passengers an extra 20 kg each (long-haul FSA vs average LCC allowance) could, if everyone used it all, add up to 3.5 tons total. Freight rates vary widely, but on a 3,000 mile flight that's worth \$7k-\$10k in freight revenue, or \$40-\$60/pax. Admittedly that's on the upper end of the range, but you can see there's money to be made. For an A320 that only costs ~$7k/hr to fly, it's a lot.

Less ethically, moving weight and volume from luggage to carry-on is profitable for a mixed passenger/cargo airline. Checked-in luggage has to be weighed in all cases, to ensure each piece is within safe limits for manual handling. This known weight then eats into the takeoff weight calculation, leaving less for cargo.

As airliners are designed to take off with one failed engine and carry reserve fuel for failures and diversions, this extra power works as weight safety margin when nothing fails. In practice weight margins rarely get pushed - most flights are volume-limited, with enough weight margin to take off at reduced power. Still, less luggage means more cargo means money.


Can you use a mode 3AC interrogator in EU airspace? I'm investigating the possible application of mode 3AC interrogators in EU airspace.

My experience is unfortunately limited to North America, and I'm unfamiliar with Mode S systems / function.

All the information I've managed to find describes mode S trabsponders as "backwards compatible" but fail to go into detail.

Is the backwards compatibility seamless and simultaneous?, Able to reply to both mode S and mode 3 interrogators in real time? Or a toggle switch between modes, in which when mode S is selected mode 3 interrogations will be ignored?

Do European standards allow mode 3A/C interrogators to operate within their airspace? Could this cause interference with local mode S infrastructure?

Are there any other potential concerns with operating a mode 3 interrogator in EU airspace?

To clarify I am speaking from the perspective of a ground station. As in using a mode 3AC SSR on an airport in EU airspace.

Any information would be greatly appreciated, thank you.

Partial answer:

  Is the backwards compatibility seamless and simultaneous?

Yes.

  Able to reply to both mode S and mode 3 interrogators in real time?

Yes.

  Or a toggle switch between modes, in which when mode S is selected mode 3 interrogations will be ignored?

No - a Mode S transponder will respond to interrogations by a "pure" mode 3 interrogator. Mode S interrogators have a special interrogation format that allows them to interrogate "pure" mode 3 transponders without triggering replies from mode S transponders even though those transponders do support mode 3 interrogations.

  Do European standards allow mode 3A/C interrogators to operate within their airspace?

Don't know.

  Could this cause interference with local mode S infrastructure?

Yes, in principle, for the same reason (FRUIT) that mode S was introduced in the first place - "overcrowding" of the airwaves. It won't be catastrophic. There are already plenty of airborne mode 3 interrogators operating (TCAS and AWACS).

  Are there any other potential concerns with operating a mode 3 interrogator in EU airspace?

Consider both radio communication regulations and aviation regulations.


On an average, space of how many economy class seats is taken up by a suite? The suites offered by many airlines for the super rich, are very spacious and convenient. Though, I can only Read about them! One thing I can see is, the A380 is capable of upto 853 economy only passengers, but most of them carry 500 economy, 65 business and 12 suites. So, they must be eating some considerable amount of space. What I am asking is, basically the number of economy class seats that would fit inside a first class cabin and not how much space is available for first class and economy class cabins.

The size of the seat is slightly different in each airline, but according to this table, 32"×18" is the smallest, and most common, economy seat. That is 4 ft².

According to the article you linked, the largest suite is 125 ft². That is 31¼ times more.

Remember, however, that space is not the only consideration. The main consideration for aircraft is weight and obviously first class passenger does not weigh more than economy class one.

Now consider that those 853 passengers, with baggage, will weight around 80 t. Maximum take-off weight is 575 t of which 276 t is empty weight and the tanks can take about 260 t of fuel. But that leaves you only 39 t for payload with full tanks! So on very long routes, the aircraft can't pack 853 passengers anyway. The 500 is about maximum that makes sense (for long range variant, which is most common).

So they don't mind wasting some space for luxurious first class if they can charge premium for it.


What to do if carbon monoxide is present? Most small, single engine aircraft are fitted with non audible carbon monoxide detectors that turn black if it is present.

Carbon monoxide can incapacitate in mere seconds (and kill in minutes) depending on the ppm.

If you are cruising at 12,000 feet, that is not enough time to land.

So what should you do if you see a carbon monoxide warning (and begin to feel the effects of it)?

The first thing you're going to want to do is get fresh air into the cabin, by ensuring the vents/windows are open. This will dilute the amount of CO in the cabin and stop your symptoms getting worse - allowing you to land as soon as practical.

There is also some good information online which contains further advice:

  Turn the cabin heat fully off.
  Select maximum rate of fresh air ventilation to the cabin.
  Open windows if the environment, flight profile and operating manual permit.
  Consider using supplemental oxygen if available and if doing so would not  introduce another safety or fire hazard.
  Land as soon as possible/practicable.
  Inform Air Traffic Control of your concerns and intentions.
  Select a leaner fuel mixture if possible.
  After landing seek medical attention as soon as possible.
  Before continuing the flight, have the aircraft inspected by a certified mechanic

If you're wondering about the first point, the reason is that the cabin heat is the primary way CO enters the cabin of light aircraft.

  Typically most piston powered aircraft obtain their cabin heating by directing fresh (ram) air over the engine muffler (silencer). If there are any cracks, holes or poorly fitting components in the exhaust system, then CO-rich exhaust gases can enter the cabin. Engine exhaust may also enter the cabin through inadequately sealed firewalls and wheel wells etc.


How is an A320 on the ground kept cool inside if the APU fails? What happens to the air conditioner when the APU is not available due to damage or it just fails?
Also adding that the airport does not have an air conditioning unit. Since it is above average sea level, what procedures should be performed?

They can leave one engine running to take the place of the APU. If that's not possible for whatever reason, the interior just gets warm.


What does the "DO NOT USE FOR NAVIGATION" indication mean? Sometimes when I'm browsing IAC charts online I find a "DO NOT USE FOR NAVIGATION" notice printed on the chart. Not always though.

For example, have a look at the chart for Queenstown RNAV (RNP) Y RWY 05.
See the notice there?

I have always wondered why do procedure designers put these notices on their charts. I find it almost contradictory, since I think these charts are the best source of information that an aircrew can have to navigate/maneuver. Isn't it ironic?

I'm sure I must be missing something.

Can anybody shed some light on this?

PS: These are not SIM charts. These are real charts from the AIP.

Unless it's an obsoleted procedure chart, it usually means that it's not complete.  The example you show has only the features pertinent to that approach, and its missing (for clarity) the features needed for any other aviation in that area.

You must use a sufficiently complete chart for navigation; the approach diagram is supplementary to your navigation chart.


Could you help to identify this WW1 fighter? Please help me identify this world war 1 fighter.

Pretty sure it's an Albatros C.I. Look at the access hatch with the double gills directly behind it, the three metal covers on the engine, the horizontal and vertical black marks on them, the upper wing support ending right between the two metal covers, the front support for the undercarriage ending right before the second gill.

Albatros C.I (Picture copied from the link above)

The Albatros C.III has a different tail, but that's invisible in the picture above.

Here is another picture, showing the plane from the other side. Note the flush radiator on the side of the fuselage. (image source)


Can pilots hear a car horn while on the ground? In this question I asked about the pilot's ability to give a signal to others nearby while on the ground. My question here is, if someone else wants to get the pilot's attention on the ground, could the pilot hear someone honking a car horn from the cockpit?

Edit: thanks for all comments. I want to ask about a situation involved large aircraft, engine running, car is near the aircraft. Such as in large airport operation. My question comes from series Ultimate Airport: Dubai when a trainee is driven to different areas of airport as part of his certification. I wonder if he can call attention of pilot in cockpit by honking the horn. I am aware that more standard mode of communication such as radio, flare or ground marshall is preferable.

Airplane engines are loud, so if they are running I would say no, a pilot is not going to hear a car horn. If you want to get a pilot's attention without a radio you'd use light or hand signals.


How can air stability be predicted? After several weeks of being grounded due to low clouds, I was looking forward to the cool air, clear skies, high pressure and light winds that arrived this morning as forecasted. However, there is an AIRMET over the whole region for moderate turbulence, so I’m stuck on the ground yet again staring up at a sky that looks like perfect VFR flying weather but somehow isn’t.
The FAA books tell me that turbulence is due to unstable air, but I can’t piece together why it’s unstable today or, more importantly, how I could have predicted it. Which charts or other data should I be looking at, in particular days ahead of time so I know when is best to schedule a flight?

It depends on how far in the future you are trying to predict air stability and turbulence. I am not an expert. But, I would look for some indicators.
For instance, the historic Program Charts from Friday and Saturday show a cold front moving through the area of KADS from West to East. The winds were drastically shifting as the front moved through. This would be an indicator that it might not be a good day to fly. Combine this prognostic data with the METARs from the previous 24 hours to your flight, there is cause for concern for a light aircraft. The winds and gust factors in these METARs might have given you as much as a 24 hour warning of what was to come. Then, there is the Aviation Area Forecast Discussion which will give you further guidance. Lastly (and least used), right before the fight, you could have even checked out the Skew-T/Log-P Diagram in order to judge the strength and severity of the instability.
METARs for KADS:
KADS 141352Z 19008G15KT 8SM BKN009 21/19 A2990
KADS 141447Z 19008G16KT 8SM BKN014 22/19 A2990
KADS 141547Z 19010G25KT 10SM BKN022 24/18 A2989
KADS 141647Z 20017G32KT 10SM BKN028 BKN070 25/18 A2987
KADS 141747Z 19016G31KT 10SM BKN033 27/18 A2983
KADS 141847Z 19016G31KT 10SM BKN039 27/17 A2978
KADS 141953Z 19016G30KT 10SM BKN046 BKN055 27/17 A2974
KADS 142053Z 19012G26KT 10SM BKN050 28/17 A2971
KADS 142153Z 19011G20KT 10SM SCT044 OVC055 27/17 A2972
KADS 142253Z 19016G30KT 10SM SKC 26/17 A2971
KADS 142353Z 19012G21KT 10SM SCT120 26/17 A2973
KADS 150047Z 20009G20KT 10SM SKC 25/17 A2976
KADS 150147Z 20009G20KT 13SM SKC 25/17 A2977
KADS 150215Z AUTO 20009G17KT 10SM CLR 25/18 A2980 RMK AO2 T02450175
KADS 150247Z 18008G16KT 10SM SKC 25/17 A2978
KADS 150255Z AUTO 20009KT 10SM CLR 24/18 A2981 RMK AO2 T02420175
KADS 150315Z AUTO 20008KT 10SM CLR 24/18 A2981 RMK AO2 T02410175
KADS 150335Z AUTO 20009G15KT 10SM CLR 24/18 A2982 RMK AO2 T02410175
KADS 150355Z AUTO 21007KT 190V250 10SM CLR 24/18 A2983 RMK AO2 T02400175
KADS 150415Z AUTO 22004KT 10SM CLR 24/18 A2984 RMK AO2 T02360175
KADS 150435Z AUTO 22004KT 10SM CLR 24/18 A2985 RMK AO2 T02350175
KADS 150455Z AUTO 23006KT 10SM CLR 23/17 A2986 RMK AO2 T02330173
KADS 150515Z AUTO 23006KT 10SM CLR 24/17 A2986 RMK AO2 T02380170
KADS 150535Z AUTO 25007KT 230V290 10SM CLR 24/17 A2987 RMK AO2 T02360169
KADS 150555Z AUTO 29017G23KT 10SM CLR 23/15 A2990 RMK AO2 T02330150 10254 20232 402730182
KADS 150615Z AUTO 33018G24KT 10SM CLR 22/07 A2994 RMK AO2 T02150072
KADS 150635Z AUTO 34020G30KT 10SM CLR 18/02 A2999 RMK AO2 T01820024
KADS 150655Z AUTO 35020G27KT 10SM CLR 17/02 A3002 RMK AO2 T01710015
KADS 150715Z AUTO 35015G22KT 10SM CLR 17/01 A3004 RMK AO2 T01650013
KADS 150735Z AUTO 35013G28KT 10SM CLR 16/01 A3006 RMK AO2 T01610005
KADS 150755Z AUTO 35019G25KT 10SM CLR 16/M02 A3008 RMK AO2 T01571018
KADS 150815Z AUTO 35013G18KT 10SM CLR 15/M03 A3010 RMK AO2 T01541034
KADS 150835Z AUTO 35013G22KT 10SM CLR 15/M04 A3011 RMK AO2 T01501045
KADS 150855Z AUTO 35013G20KT 10SM CLR 15/M05 A3013 RMK AO2 T01461051
KADS 150915Z AUTO 35015G24KT 10SM CLR 14/M06 A3014 RMK AO2 T01441065
KADS 150935Z AUTO 35012G19KT 10SM CLR 14/M07 A3014 RMK AO2 T01391070
KADS 151147Z 35010KT 10SM SKC 12/M07 A3020
KADS 151247Z 35012G17KT 10SM SKC 10/M07 A3022
KADS 151347Z 33005KT 10SM SKC 11/M05 A3025
KADS 151447Z 35012G16KT 10SM SKC 13/M06 A3029
KADS 151547Z 36013G20KT 10SM SKC 14/M07 A3030
KADS 151647Z 02010G20KT 10SM SKC 16/M07 A3032
KADS 151747Z 03010G20KT 10SM SKC 17/M08 A3031
KADS 151847Z 34008G15KT 10SM SKC 18/M08 A3029


What is the significance of Slip-Skid Indicator in PFD? Slip Skid Indicator as depicted in the picture below;

What's the significance of Slip Skid Indicator?

How Slip Skid Indicator is used in flying the aircraft?

What are other performance/operations needs to be taken care while this exceeds its normal bound?

Primary flight display with Slip Skid Indicator, Source - www.aboutflight.com

The slip/skid indicator is the small bar under the roll pointer. The image below should clarify that.

Image from flightlearnings.com

The Slip/Skid Indicator (sometimes called turn-and-bank indicator) moves left and right relative to the roll pointer in proportion to lateral acceleration and helps the pilot correct for any deviations in a turn.

In a level flight, the indicator is centered. Assume that the pilot is executing a left turn (the roll pointer would've moved left)- if the indicator is in center, it means that the turn is coordinated i.e. the aircraft is not slipping or skidding.

If the indicator (bar) is moving right, it shows that the aircraft is skidding. Movement in the opposite side (i.e. towards the left, same direction of turn) indicates that the aircraft is slipping. This enables the pilot to take corrective action. This is one of the necessary flight instruments.


How realistic is the aviation crisis in the recent Spider-Man movie? In the 2014 film The Amazing Spider-Man 2, there's a sequence in which a villain disables the city's power grid.  All over town, stuff loses power... including the local airport and its air traffic controllers.  This is a problem because there are currently two planes inbound, on courses that will cause them to collide with each other in midair unless the tower can warn them in time!

Luckily, Spider-Man finds a way to defeat the villain and the ATC gets their power back just in time to radio the planes to change course, and they miss each other by an extremely narrow margin.

Putting aside for the moment the question of whether or not a real ATC would have their own independent backup power source, how realistic are the two premises of this crisis?

1) That two airplanes would be inbound towards a major airport on courses that would cause them to both occupy the same position in 3D space at the same time, and

2) That neither pilot would actually notice this until either the tower told them or something suddenly goes CRUNCH!  Do commercial jet liners not have their own radar at the very least?  (Heck, my car has little radar emitters that warn me if something is too close!)

This depends on the aircraft type, the flight rules and weather conditions as contributing factors.

Larger aircraft or medium sized aircraft operating under general aviation or commercial aviation will in many cases be equipped with a technology called Traffic Collision Avoidance System (TCAS) (See: How does TCAS work?), which can instruct both aircraft to take evasive action if a collision is imminent. This is especially important in Instrument Meteorological Conditions, where pilots do not rely on outside visibility, but on instrument flight only operating under Instrument Flight Rules.

In Visual Meteorological Conditions, aircraft would likely be able to see each other and take evasive manueouvers without ATC or TCAS having to warn them, e.g. this is the case for smaller aircraft operating under Visual Flight Rules.

Aircraft receive clearances and instructions to occupy a certain flight level or altitude, sometimes coupled with clearances for approaches or arrival/departure procedures. If pilots do not receive further instructions, they will start to hold over their last clearance limit and commence lost radio/comms procedures, which include holding for a given amount of time and then beginning the descent towards the airport on defined and published approaches. If the power outage is long enough, the airspace is quite busy and all other frequencies are also unavailable, one of the being the distress or guard frequency, there is a probability that two aircraft on the same level will reach their clearance limit at some point and enter a hold at the same flight level, which could result in a collision.

The scenario however assumes that really all failsafes and contingency procedures have failed.

See also ths related question: What happens when an airport shuts down?


Why is extreme cold weather a challenge at airports, since jets operate at extreme cold conditions in flight? Wondering what specifically the issues are. Obviously, taking off and landing have more 'moving parts' but more curious about the actual extreme cold.

I assume the operating temperatures at cruise are much lower than ground temps.

The extreme cold is not an issue so much as the weather that typically accompanies it and the fact that planes are not always designed to be started in extreme cold with out some assistance even if they can run in it. For example so long as the weather is good and the aircraft are equipped, there are plenty of airports in Antarctica

When extreme cold is accompanied by precipitation you can get ice build up on the runway which is quite dangerous. Most airports that are in an area of regular cold weather are equipped in some way to handle this.

Extreme cold temperature that comes with/because of frontal movement may also come with very high winds that can exceed aircraft limits. But high winds can come with warm weather as well so this is not exclusive to the cold.

For piston engines you have an issue of thick oil. When the temperature drops the oil thickens and it becomes hard to start the engine as well as running the risk of engine damage. Piston engines in commercial operations are much less common than they once were so this is less of an issue. However the general aviation fleet is still pretty effected by this issue.

Jet engines do have cold start procedures just like piston engines, there is a good discussion on that here. You can see a neat video of an A320 starting up in -28C conditions here so cold weather starts are not a huge issue.

Most airports have some form of ground crew that operate in the elements. Crew like baggage handlers, aircraft marshaller, and even mechanics may work out on the ramp to get an aircraft loaded and ready to go. This is one instance where sheer cold can be a factor although weather can also make working conditions very tough, even if proper protective gear is available.


How much does it cost to learn to fly in the UK, and what restrictions are there? Flying has been a dream for me since I was a little boy. My absolute dream career was to be a fighter pilot in the RAF. It's obviously a very hard career to get into, however I fell even before the first hurdle when I found out that I'm colour blind.

Finding out I was colour blind actually closed a lot of potentially enjoyable careers. Police, Armed Forces, Electrical all reject colour blind people.

I'd love to be able to fly, freely in a light aircraft - something like a glider or mosquito helicopter, but I just can't figure out where I need to start. Also, I'm not sure if it's financially viable.

Could someone give me a breakdown of costs and commitments needed?

Also, I'm assuming that being colour blind doesn't automatically mean I'm not able to fly?

Also, I'm in the UK

My recommendation is: Join a glider club. This limits the expense and puts you into contact with many like-minded people. Make sure the club has several gliding instructors, so you will have enough chance for training lessons.

Did you try the UK gliding club finder yet?

I prefer gliders over powered aircraft because they expose you to the weather and the laws of aerodynamics much more directly. Also, the expenses per hour are much lower. At most clubs, you can expect to pay around £20 per hour to hire a glider, around £30 for an aerotow launch and around £8 for a winch launch.


Why aren't AMA certified radio-control club sites shown on aeronautical charts? All this drone business wound up affecting us R/C fliers that fly only at local verified club sites. I wrote (told) the FAA that our local AMA R/C flying fields are constantly having "our" flight areas intruded on by full-scale aircraft that unknowingly fly over our field.

Why are permanent R/C airfields not shown on aeronautical charts?

In response to comments:

We are not near an airport.
We take note when overflown by 2500' or less
Drones with FPV can easily stay under 400' AGL as suggested by the FAA but they will very likely not be aware of the location of manned aircraft
Other RC aircraft have no way of knowing where the 400' limit is and can easily go much higher, and manned aircraft would not be aware of this

Model aircraft flying areas may be registered with a group such as AMA but there is no requirement to register these areas with the FAA. The current FAA rules expect RC pilots to stay out of airspace in use by manned aircraft, or give way to manned aircraft at all times.
It would require a lot of extra work for the FAA to register every AMA field and mark them all on charts or to enforce restricted areas around them. Also, model aircraft are not limited to AMA fields. This seems to be a reasonable compromise: the FAA lets you use the airspace as long as coordinate with nearby airports and avoid all manned aircraft.
The FAA has provided guidelines for model aircraft flying an an Advisory Circular (AC) as of January 2016:

Model aircraft operators should follow best practices including limiting operations to 400 feet above ground level (AGL).
The aircraft operates in a manner that does not interfere with, and gives way to, any manned aircraft

If you stay under 400 feet as the FAA suggests, you will not be interfering with manned aircraft, which should not fly any lower than 500 feet.
If you choose to fly above 400 feet, it is your responsibility to avoid manned aircraft. You can see them but they probably can't see your model aircraft. Stay aware of your surroundings, use a spotter if you have to.
Remember that the airspace belongs to manned aircraft, and you are only allowed to use it if you don't interfere with them.
See related question: Where is RC aircraft flying allowed in the US?


Whenever I hear a plane throttling down quickly, what is happening visually? I am completely blind and have heard this several times when I was at air shows. Then my friend sent me this recording of a crop duster spraying the fields, and I heard the same type of sound.
It starts out by slowly ascending, and then the plane's engine rapidly decreases its speed.
I know that because of the Doppler effect, sounds can sometimes be deceiving, so I wondered what I would hear if I were inside the plane.
Here's the recording. It's audio, unfortunately, but hopefully someone with experience will be able to provide clarification.

Ok I listened and what you are hearing is a turbine powered ag plane.  Most of the rising and decreasing pitch you are hearing that sounds so dramatic is doppler effect from the propeller.  The propeller speed will be constant all this time as the pilot will set the RPM for his activity and leave it, just changing power with throttle.
So in the cockpit, the noise from the prop will more constant without the rising and falling sound, just a steady OOOMMMM of somewhere around 100 hz (three blades at 2000 rpm say), not as intense as the sound heard from the ground, with a roar/hiss from the air passing that rises and falls somewhat with speed as he dives and zooms.
The intensity of the propeller sound will also increase or decrease a lot with the power, but not the overall pitch; because the propeller is constant speed, that remains constant unless the speed is changed, and that won't happen during this maneuvering.
Then the very high pitch zeeeeeeeeee whining sound under the big booming sound is the turbine engine itself. It's sound will change a little bit from within the cockpit as power is added and removed, with some change in the pitch of the whining sound and its intensity.
This video is from the inside of a plane like the one you heard, but the inside sound is being recorded through an active noise cancelling headset, so 80% of the cockpit sound is being suppressed.  But you can hear faintly the airstream, and a bit of the prop's sound and can tell that it's pretty constant to the pilot the entire time.  Way less dramatic for sure.


Maximum Altitude/Minimum Range limits of ATC PSR I am trying to get an understanding of the ability of an air traffic control primary radar such as an ATCR-33 to track high flying targets (above 40,000 feet) at relatively close ranges (less than 15 nm horizontal distance from the radar).  An alternative way of asking the question is what is the maximum 'beam elevation' (I think that that is the correct term) for a radar like an ATCR-33?

This paper seems to show beam elevation from 0 to 40 degrees, dropping off after that.
See slides 10 and 15.


How much advance notice does the FAA have to give for a TFR? I recently heard a story from a friend about a pilot that broke a TFR which was issued after takeoff. This sounds suspicious to me that the pilot had no advance notice of the TFR. Is the FAA able to issue an immediate TFR with no advance notice? If so, how can a pilot become aware of these?

The FAA can issue TFR's on short notice, and if you are flying a slow plane or a fast plane far they may very well pop up while you are inflight. While things that cause TFR are often planned in advance like the super bowl there are plenty of last minute things like a wildfire or a quick movement of the President that will force a fast TFR to "pop up". Even the FAA admits they can can be unexpected

  TFRs can pop up unexpectedly, so before any flight, be sure to
  research NOTAMs, check the TFR list online at http://tfr.faa.gov, and
  call Flight Services for updates at 1-800-992-7433.

I can not find any regulations sating the FAA has a minimum amount of notice time they must give.

A pilot flying VFR in an airplane not radio equipped is always at risk of busting one of these. But if you are in a radio equipped aircraft taking flight following or monitoring your local FSS is a good way to be aware of these kinds of events.

This AC covering TFR's does not list a minimum amount of time they must be filed before becoming active.


How can I use a magnetic declination chart to calculate true track, magnetic track and magnetic variation? If I am given values such as 30 degrees south and 75 degrees east with a true track value such as 70 degrees, how would I calculate the magnetic track?

I understand that True track = Magnetic + Variation. But I'm not sure how to use the magnetic declination chart.

This is my attempt at such values:

The chart shows you lines of equal declination $D$. You identify your location on the chart (which you have done and marked with an X in your second image). Then you determine on which line you are. It looks like the point is between the -26° line and the -28° line, so let's call it $D=-27^\circ$. That gives you a magnetic track of:

$$ \varphi_\text{mag} = \varphi_\text{true} - D = 70^\circ - (-27^\circ) = 97^\circ $$


Planes returned to base after dumping fuel due toilet issues A colleague of mine experienced this and I was astonished.
Flying KLM from PVG to AMS a couple of hours into take off toilets became full. The pilot dumped fuel and returned to PVG. All passengers were re-booked next day. Funnily, she had the same issue fly from JFK to LHR last year. (Probability that she was on both planes - amusing)

Thinking of aviation fuel, environment, cost of re-flying passengers. I wonder why the aircraft makers not allow dumping 'contents' of 'toilet tank' (on the open sea) instead of dumping gallons of fuel.

I just wonder how often does such issues happen? Would toilet tank emptying not be checked before take off?

An aircraft with full lavatory waste tanks can not continue on it's flight as it is a requirement to have a specified number of serviceable toilets on every flight.  It is usually the responsibility of the Purser or In Charge Flight Attendant to check the waste tank volume when they prepare for each flight. On most aircraft there is a control panel with a display that shows the actual waste volume.

Here are some possible reasons why the waste tanks became full:

They were not checked before the fight
They were not emptied on the ground
They malfunctioned and ran continuously
The display on the waste control panel malfunctioned

In any case these tanks can not be emptied while airborne, and the only course of action is to land and have the tanks emptied or serviced.

On a long haul flight like PVG to AMS the crew would not have been legal to continue their duty day after returning to PVG and the flight would have to be cancelled or delayed until a new rested crew could be found to operate the flight.


Are afterburners required to be engaged during catapult launch? Is it required to engage afterburners during catapult launches from an aircraft carrier?

This answer mentions that afterburners are used for night takeoffs as per regulations, but not required during day takeoffs. Is this true? If yes, why?

The short answer is very much "no" -- afterburners are not at all required to launch from an aircraft carrier.  Longer answer: Fred Larson's comment is correct: it really depends.  Ultimately a given aircraft, at a given weight, with a given wind-over-the-deck, and a few other things, requires a given amount of thrust to get airborne -- whether it comes from dry thrust or afterburner doesn't change the requirement.

There are a large number of carrier-based aircraft (the A-7, A-6, and E-2 leap immediately to mind) and there are certainly others that flew off-deck without afterburners.

Current aircraft like the F/A-18 Hornet can be launched without afterburner in some, but not all, configurations.  For the most part the incremental safety margin and increased take-off weight means that afterburners are used for takeoff, but it's not strictly a requirement.


Is there a "pounds per hour" reading that could have signaled the fuel leak to the pilots of Air Transat 236? Watching a documentary and reading up on the Air Transat 236 incident, I would have thought that even with the tech available in 2001, it would have been simpler to spot a fuel leak, even with the strange warnings going on. Don't aircraft have a "pounds per hour" real-time display that indicates rate of fuel expenditure?

If so, would such a device have been taken to have malfunctioned or showing incorrect information, or would the difference it showed at the time of the leak be unnoticeable? It is said that the pilots were checking fuel balances half hourly or so before the first alarm. Would a "pounds per hour" display be a good up-to-the-second indicator, that even if the last fuel check was ok, there was now a steady problem? Would it remove be necessary to make any other calculations or do any other guesswork? Was this figure/display not available on this flight?

Fuel flow is measured by flow transducers in line with the fuel pipes. And they do a very good job at measuring flow, but unfortunately a fuel leak bypasses them. There is no direct measurement of the leak flow anywhere.

The pilots of Air Transat 236 had two indications of the fuel leak:

Increased fuel flow through the oil/fuel heat exchanger caused a drop in oil temperature and a corresponding increase in oil pressure.
Drained fuel on the leaky side caused a fuel imbalance.

It would only be possible to positively identify increased flow as a leak if the leak occurs in between two flow transducers, both mounted in the same fuel line. If the leak occurs after a single transducer, the increased flow gives an indication. Otherwise, the leak flow would have to be observed from available volume, minus legitimately used engine flow. There are fuel tank probes distributed in airliner fuel tanks that give an indication of fuel volume per tank. Picture below shows the six fuel probes in the 747 centre tank (source).

The difficulty here is that leak flow must be derived from volume measurement: unit of flow is $m^3$/sec, the derivative of volume. The wing tanks are long and flat and the probes measure vertical distance, with an accuracy that suffices for Qty indication but lacks the precision of the fuel flow meters which directly measure impulse of the mass flowing through them. Plus they measure mass directly, a more useful entity than volume. Volume per mass changes with fuel temperature, tank levels change with aircraft pitch and roll, the level needs to be derived over time: all of this can only give an indication over the course of hours, when a large amount of fuel has leaked out already, and with a degree of uncertainty that would leave room for doubt.

You're right though, in wondering why there seemed to be no automated way for monitoring discrepancies in fuel quantity. @Waked mentions the estimation messages of the B737NG, which would also only seem to occur after much fuel has been lost aready. The A330 now has an ECAM caution message: FUEL FU/FOB DISCREPANCY, put in place after the Air Transat incident. Lessons learned from this incident would now be incorporated in the fuel management systems and aircrew procedures. The brilliant glide flight of the pilots demonstrates once again why we need pilots in front of the aeroplane.


Credible Sport Project: Is it possible to revive the idea with modern avionics? Synopsis: On a secret mission to rescue 52 hostages in Iran, Operation Credible Sport was created. The project consisted of a modified Lockheed C-130 Hercules and developed so that it would be able to land on a runway as short as a football field. In order to shorten the landing distance, the engineers retrofit the planes with rockets.
These rockets slow the planes as it lands and provide extra propulsion upon take-off.
During training in October 1980, just days before the surgical operation, "Operation Credible Sport" derailed.As the plane came in for landing, the pilot mistakenly fired the rocket before the wheels touch-down. The plane loses lift and slams in the tarmac.

For illustration purposes, here is a short video summarizing the event: Credible Sport Test YMC 130 H

Now, technology has come a long way since the 80's; avionics have greatly improved and the aviation industry even came up with the fastest transistor ever-created in 2009 thanks to Northrop Grumman.

That being said, would it be possible to revive this project and allow an automatic firing of the rockets by a computer system rather than by a manual control of the pilots(given that it was human factor that doomed it to failure in the beginning)?

It wasn't a lack of technology. The technology to automatically fire the rockets is not actually very complicated: a radar altimeter, airspeed data and maybe input from the landing gear load sensors hooked up to a simple computer. All of that existed back then, and the rocket system was in fact computerized:

  The Lockheed test crew then assessed that the computer used to command
  the firing of the rockets during the landing sequence needed further
  calibration, and elected to manually input commands.

So the plan was to use computer control, but it needed more development than they had time for - as were in a very big hurry they decided to do it by hand.

If they'd had more time to adjust things they no doubt would have succeeded with the technology of the time. The reason that the project was canceled was not a lack of technology but that the hostages were released.

In reality the plan to use rockets to slow down the airplane so quickly was extremely risky, and if it went wrong the US military would have had their best special forces units stuck in the middle of Tehran! I personally don't think this would have gone ahead even if the tests had been successful. The fact that they continued to develop the concept into the MC-130 Combat Talon II without the rockets indicates to me that the military thought the braking rockets part of it wasn't worth it.

So no, modern avionics really would have nothing to do with it.


Does the "west evens / east odds" rule apply when flying without a specific destination (sightseeing, etc)? I understand about the rule about odd / even (+500ft) separation at altitudes above 3,000ft AGL, but what about when you're flying without a definitive destination such as sightseeing where your track might change often? I realize that the solution isn't to continuously change altitudes, but what is the generally accepted rule here?

UPDATE: To be clear, I'm not suggesting sightseeing above 3,000ft or anything like that, but rather what is the rule (if any) to help with safety in regards to collision avoidance when flying with no definitive track. Is it normal / expected to be able to simply just fly-about at any altitude?

14 CFR 91.159 says:

  Except while holding in a holding pattern of 2 minutes or less, or
  while turning, each person operating an aircraft under VFR in level
  cruising flight more than 3,000 feet above the surface shall maintain
  the appropriate altitude or flight level prescribed below, unless
  otherwise authorized by ATC: [etc.]

So if you're above 3000' AGL and not turning or in a hold, then you're required to follow the odd/even rule. Personally, I've never found it to be an issue because if I'm on a sightseeing flight or just following a river or whatever for fun then I'm usually below 3000' AGL anyway (and 91.159 is one of the reasons why).


Where is the pitot static drain located on a Piper PA-28? Some PA-28 airplanes have pitot static drain where the pilot pushes 2 buttons to open the system.

But where does the water drip out from the airplane? Is there a hole underneath the airplane? Where?

I mean when you push the buttons where should you look for water coming out?

This presentation gives a nice overview of various systems on the Piper Cherokee series. The buttons you describe are shown here:

(slide 9)

The full pitot-static tube including the drain is shown here:

(slide 11)

So the drain is incorporated in into the pitot-static tube itself.

The buttons are also acting as a drain themselves, for details see Alexander's answer.

Related:

What is the difference between a pitot tube and a pitot-static tube?


How does F/A-18 autotrack work? This is about the alleged "UFO" video. However, I'm not interested in speculation about what exactly the aircraft being tracked in the video is.

What is "autotrack" in an F/A-18 Super Hornet? Does it involve tracking by the radar, infrared, or digital interpretation of the video stream by a computer?

I've provided a link to the video. This shows the aircraft (the alleged "UFO") being "tracked" by what the pilot claims to be "autotrack":

As a bonus question, what is the other pilot asking about? He asks "Did you box a moving target?", what does it mean to "box" a moving target? Does it refer to radar tracking?

Autotrack means the FLIR (Forward Looking InfraRed) sensor attempts to track whatever object falls inside the tracking area. It means whatever the pilot was trying to keep up with was producing emissions in the infrared (heat) and the system was automatically tracking it.

Boxing a moving target is having the tracking system detect and track a target you have selected. In this case, the other pilot was asking if he had selected the target manually (boxing) or if the system detected and autotracked the target on its own.


What is the relationship between aspect ratio and divergence speed? Why do longer wings with higher aspect ratios have lower divergence speeds?

Because the wing has less torsional stiffness for a given area. This lets lower torsion moments overpower the ability of the wing to resist that torsion.

The torsional stiffness is proportional to the skin thickness and the cross sectional area of the airfoil. For a given wing area and lifting potential, a higher aspect ratio will reduce that cross section, so less stiffness remains.

Divergence occurs when the increase in the aerodynamic torsion moment from the twisting of the wing is bigger than the increase in restoring moment from the wing's torsional stiffness. It does not help that a wider wing has more span to accumulate that twist, so the aerodynamic torsion moment on a high aspect ratio wing is high despite the smaller chord which helps to reduce that torsion moment. However, while chord length is inversely proportional to aspect ratio, the airfoil's cross section is inversely proportional to the square of aspect ratio, so the higher aspect ratio wing has a lower ratio of torsional stiffness to aerodynamic torsion moment.

Theoretically, an aero-isoclinic wing shows no torsion under bending and is supposed to have an infinite divergence speed. However, such a wing must do without ailerons or any other imperfections which might upset the fine balance that is required for its isoclinic nature. The linked report shows that the aero-isoclinic condition is not sufficient to prevent flutter or divergence.


How much, generally speaking, does it cost to learn how to fly? One of my life goals is to learn how to fly a plane. I can't do it now due to time constraints, but I am curious: How much, in general terms, does it cost to learn how to fly? I.e. piloting lessons, license fees, etc. I would be doing it in the US.

Assuming a regular private pilot's license (i.e. not sport/recreation), a part 61 instructor, and a rented aircraft, then you need to budget for the following:

Aircraft rental (this usually includes oil and fuel)
Instructor time (air and ground)
Materials (books, DVDs, charts, fuel tester etc.) as recommended by your instructor
Headset
Third-class medical
Insurance
Written test fee
Examiner's fee for the actual test

If we assume the aircraft costs \$120/hr wet (i.e. including oil and fuel), an instructor costs \$40/hr and you need 50 hours to be ready for the test (40 is the minimum required) then you can do a calculation like this:

35 flying hours with instructor: \$5600
15 flying hours solo: \$1800
15 hours ground school (instructor's time): \$600
Materials: \$500
Headset: \$500
Third-class medical: \$150
Renter's insurance: \$700 (per year)
Written test fee: \$150
DPE test fee: \$400 (plus \$120 rental for the aircraft)
Total: \$10,520

You can play around with these numbers, there's a lot of variation and research is obviously important. But the single largest cost will be the number of flying hours you need, so anything you can do to reduce that time is worthwhile and the simplest - but unfortunately not the easiest - way to do it is to fly as much as possible, i.e. several times a week. Given weather and other factors, you should probably even plan to fly more than you actually can on paper: a bunch of flights will certainly be cancelled.

You can also train in the most 'minimal' aircraft you can find: a two-seater aircraft without a glass panel could be \$50/hr cheaper than a four-seater with a G1000. Unless you have a very clear idea about what sort of flying you'll do in the longer term there's no point in paying for anything that isn't directly required for the private pilot's test.


Is it possible to obtain the lift and drag coefficients of a 3D body in ANSYS Fluent? Is it possible to obtain the lift and drag coefficients of a three dimensional body in ANSYS Fluent? Or, would it be acceptable to take the coefficients of several cross-sections along the wings and body and perform a weighted average calculation to find the lift and drag values for the entire craft?

Yes this is possible, and it is the way lift and drag of aircraft are estimated in the pre-design phase. There is detailed methodology described in Synthesis of Subsonic Airplane Design by E. Torenbeek, Appendix E. for lift and pitching moment, Appendix F. for drag.

For lift and pitching moment, first the wing characteristics are estimated based on known research and on corrections for fuselage length, wing/body interference length etc.

For drag, first the $C_{D_0}$ of all components in the table underneath are determined, and then the lift of the wing, body, tailplane etc as function of angle of attack are added.


How does one reverse direction on a VOR radial? Tracking inbound, say on R-270, how do I track outbound on the same R-270? What intercept heading shall I fly?

Spin the obs 180 so it changes from "To" to "from" then make a 210-220 degree turn(180 plus a 30-40deg intercept) and fly until the VOR radial comes in, then track the VOR.


Is there any way to stop a pilot from crashing an airliner? If a pilot decides to crash an airliner, a la Germanwings or Egyptair, could he be stopped?

In those cases the offending pilot waited until he was alone in the cockpit to act. Thus many airlines have made it mandatory for there to be two crew members in the cockpit at all times, even if it's just a flight attendant to stand in there and wait for a pilot to return.

Although that might give passengers some piece of mind I am doubting that it would do much good. It seems to me that, even if the other pilot is in his seat and strapped in, if a pilot decides to crash the plane he could kill the engines and put the plane in an unrecoverable attitude very quickly.

Is this a correct assumption? Would Airbus envelope protections prevent this? Can the plane be placed in direct mode to override the protections?  What about a 777? Does the yoke feedback system allow one pilot to overpower the other?  The engines could easily be throttled back, but could they be quickly shut down requiring a restart? What could the other pilot do to stop his actions?

COULD you do that?  Sure.  The relevant question, though, is if the tradeoffs involved would be worth it.

How could you do that?  Essentially, a trusted 3rd party could have the ability to disable all controls that the demented pilot has access to and assume all control over the aircraft.  If you're willing for somebody in the network operations center to have the ability to "turn off" every switch & control in the cockpit and remotely pilot the airliner to its landing, then you're set.  The pilot is now every bit as much a passenger in the aircraft as everyone sitting behind him is, and short of taking the crash ax and causing a depressurization, he can't affect things that much.  (And even if he did that, the airplane still won't crash.)

The problem with that plan is obviously that if the remote control function gets taken over by hackers or a demented individual at the operations center, the pilots are helpless to intervene.  After all, for the demented PILOT to be rendered harmless, you have to remove ALL ability to override the remote control, all ability to pull circuit breakers, all ability to affect everything.

So, where is the greatest threat?  A demented pilot that overcomes the other pilot (by force, by locking him out of the cockpit, whatever), or problems at the operations center or in the remote control process?  The track record of airline pilots is unmatched by nearly anything else for reliability and resilience, and we aren't nearly as vulnerable to being hacked as any remote control datalink would be!

The general understanding is that the best solution is to keep the pilots in control of the aircraft, and have measures in place so that if one of them loses it, the other pilot can keep things going.  Things like having a flight attendant in the cockpit to let the other pilot back in (would have changed the course of the Germanwings flight) can go a long way.  Or if there is a struggle for control, a pilot could summon the flight attendants over the PA to get help restraining the madman.

Perfect solutions? No.  But better than allowing the aircraft to be taken over by somebody outside!

After all, while "pilot goes nuts" is a vivid headline, the extent of the actual risk is quite limited.  Millions & millions of commercial flights happen without incident every year, and introducing a slew of new risks in the form of remote control that can't be over-ridden, seems like a severe over-reaction to what is in fact an incredibly remote scenario.  There are better ways to deal with the extremely rare & unlikely "crazy pilot" possibility than that.


Why can’t air traffic control radars determine the altitudes of primary targets? There are two types of returns that show up on an air traffic controller’s radar screen:

Secondary returns are not, strictly-speaking, radar “returns” at all, but, rather, signals automatically broadcast from an aircraft’s transponder, containing encoded location, altitude, airspeed, identification, flightplan, aircraft type, etc., data retrieved from the aircraft’s onboard instruments.  These are highly valuable, but, obviously, can only be used with aircraft equipped with a functional transponder which have said transponder turned on and transmitting non-bogus data.
Primary returns, in contrast, are true radar returns – direct reflections of the radar’s beam from the surface of an aircraft, bird, cloud, piece of debris, missile, tree, UFO, balloon, hailstone, or whatever else happens to be in the air at that moment.  As they merely require that an object be located where the radar beam can reach it, they are of great use in tracking aircraft with nonfunctional transponders (due to, for instance, a general electrical failure or simply a faulty transponder), aircraft in combat zones (for whom broadcasting an identification signal would be a great way to get shot down), pieces of aircraft, flocks of birds, or whatever other non-transponder-equipped objects one has a desire to track.

One common limitation given for primary radar returns is that they provide no altitude information, but only positional information.  But this makes no sense, as determining the position of a target requires knowing its elevation angle, azimuth, and distance relative to the radar installation (without knowing the target’s distance, it could be located anywhere along a line extending from the radar’s location out to infinity; without knowing its elevation angle, it could be located [within the altitude limitations of the object generating the target] anywhere along a circular arc extending from the horizon to the zenith at the specified distance from the radar; without knowing its azimuth, it could be located anywhere along a horizontal circle centered in the sky directly above the radar), and, if the elevation angle, azimuth, and distance of the target are all known, that also pins down the target’s altitude – not just its location.  Besides, military radars can and do provide altitude information for primary targets (they would be useless otherwise, as intercepting an enemy aircraft requires knowing both its position and its altitude, and enemy aircraft are unlikely to oblige a radar’s request to provide a transponder beacon signal that would aid immensely in shooting them down), which has proven valuable numerous times; for instance, the accident investigation that eventually produced the NTSB’s very first AAR used data from a military air-defence radar to determine that a 727 that crashed into Lake Michigan had descended steadily into the water without levelling off, instead of suffering an uncontrolled excursion from level flight, while, more recently, primary returns received at several military radar sites in Massachusetts showed that EgyptAir Flight 990 pulled out of its initial dive before making a second and final plunge.

So what prevents civilian ATC radars from displaying altitude information for primary targets?

without knowing its elevation angle, it could be located anywhere along a circular arc extending from the horizon to the zenith at the specified distance from the radar

Well, not quite.  Aircraft are generally much more restricted in their vertical positioning.  If there's a return from 30 miles away, that aircraft can't be overhead.  (And radars normally have a maximum elevation to the beam, often around 70 degrees).

This document suggests that (at least as of 1989) determining elevation angle was very difficult for ATC primary radar.  It was possible by cross-correlating information from multiple feeds, but that this was not routinely done.  The document focuses on how useful that would be for helping to remove ground clutter.

Even if some elevation information were available, that data might not be presented to controllers unless it were of a useful precision.  If the precision were worse than say 1500 feet, would that be useful?

  Besides, military radars can and do provide altitude information for primary targets

Radartutorial suggests that vertical discrimination (or 3D radar) requires extra equipment and is therefore more expensive.  Since ATC can get this information by secondary radar, the expense of gathering it via a 3D primary system is avoided.

Besides cost, older 3D radar would scan a region more slowly than a 2D radar.


Are there any footwear regulations for private pilots? Just wondering, as I'm working on my PPL during a hot summer, if it's legal (but probably more importantly, a good idea) to wear flip flops to fly a plane? I'm training in a 172, if that's an important factor.

There is no policy on the books that I can find in regards to this. Loosely if flip-flops make it hard for you to operate the rudder it would fall under the catch all:

  § 91.13 Careless or reckless operation.

  (a)Aircraft operations for the
  purpose of air navigation. No person may operate an aircraft in a
  careless or reckless manner so as to endanger the life or property of
  another.

However I was at an FAA WINGS lecture not all to long ago on preparing for accidents. My local FSDO's advice was to "dress for the crash" i.e. if you plan to fly over snowy terrain consider wearing boots etc. With this in mind flip-flops are more than likely not a great choice. The need to walk considerable distances over terrain is not unheard of after an accident.


How would we calculate the load factor on an aerial vehicle while landing due to sudden gust loads? In order to design the landing gear (wheels and suspension) of our model Airship, [say "m" kg -expected mass], I wanted to know, is there any way to calculate the loads which might be experienced by the wheels on impact with the ground (taking into consideration the unexpected gust loads - with gust velocity downwards say "V-gust")•

For simplicity I am Modelling it as a rigid body for now.

Note:- I thought of one way to calculate it, using momentum transfer.

Rate of change of Momentum = Force = density(rho) x projected Area(A) x (V-gust)^2.

Hence,( Gust force + Weight -Buoyant Force) ÷ Mass (m) will give me resultant acceleration.

Q1. Is this a right approach to calculate load?
Q2. Even if it's right, is this the load the wheels will experience during impact?

Please help me clear my confusion.

Edit:- Basically I want my designed landing gear with a normal sink speed upto 3m/s to be able to endure the landing impact even in case of an additional vertical downward gust upto 10m/s at the moment of touching the ground.  This is as specific and clear I could get.

You need at least the stroke of the tire-gear combination to calculate a load. If the airship contacts the ground with a velocity of $w$ and a mass of $m$, the impulse $m\cdot w$ needs to be absorbed by a force $F$ acting along the stroke $s$, as in $m\cdot w = F\cdot s$. Adding airship flexibility will greatly improve the accuracy of the result, because I suspect the hull will deform easily and add to the stroke.

If you need an example of how this is calculated for a Boeing 747, please click here.


Windowless VS windowed aircraft While Emirates was showing off its triple seven's ability to provide crystal-clear viewing from virtual windows, it mentioned: "that could be a step to windowless aircraft", and I felt like it meant to evolve into something better.
So, my question is, what would be better in general, a windowless aircraft or one with windows? Is there any improvement that comes with a windowless Airbus for example?

There are two big advantages to windowless aircraft:

Cost
Design complexity/structure

Cost is a fairly obvious one; the plexiglass used for aeroplane windows is not expensive, but designing around it increases costs all the way from conception to manufacture of an airliner. Plus the airline needs to think about blinds/curtains, seat placement, and the extra processes involved in cleaning all the windows on the aircraft regularly - inside and out.

To the second point: design. Not only do windows complicate the design of an aircraft (thus increasing the cost) but they're also structural weak points. An aerospace engineer would like nothing more than a simple tubular fuselage without these vulnerable stress points (aircraft windows are round rather than rectangular to reduce these).

Here's an interesting example of a windowless concept aircraft: the Reaction Engines A2. This hypersonic aircraft flies so high and so fast that the stresses and heat on the fuselage are simply too much for big windows to handle. Any windows would have to be tiny (like on Concorde) - so they're simply left out.

So to sum up: windowless aircraft certainly an option for future superfast and high-altitude air travel, but for today's commercial airliners the only point would be a slight saving in cost. Whether the idea of a windowless airliner would affect passenger number is unknown, but I imagine a lot of people would be uncomfortable with the idea.


When is this Class D airspace not Class D airspace? The Terminal Area Chart (TAC) shows the Class D airspace for Los Angeles International Airport (KLAX) view the full TAC. I have highlighted in green the north and south portions of the Class D airspace. The surface area directly over KLAX airport is Class B airspace.  The note - "See NOTAMs/Supplement for Class D eff hrs" is highlighted in green on the left side with arrows pointing to the two Class D areas (2700 and 2500).

This note suggests that at certain times, these two KLAX Class D areas may not be effective.

The excerpt just below the TAC is from FAA Order 7400.11 - Airspace Designations and Reporting Points and describes the official dimensions of the KLAX Class D airspace and also indicates it (Class D) may not be continuously effective.

The next to last section below is an excerpt from the Chart Supplement Southwest U.S.  (just the pertinent part). The Airspace description shows it is Class B airspace and Class D airspace with "...other times CLASS G"

The final section below is a 2012 FAA Notice (NOTC 3900) announcing the activation of LAX Class D airspace, validating that LAX has Class D airspace north and south of its runways.

My question is: When are these two (2700 msl and 2500 msl) Class D airspace sections (bordered in green) other than Class D?

FAA NOTICE NOTC 3900 - LAX CLASS D Airspace Activation

Great question. The short answer to your question is "Full Time." Ultimately that Class D airspace will be incorporated into the LAX Class B, but there is a lot of red tape involved so step one was to add the Class D extensions, then it will be incorpoated into LAX Class B at a later date. Its a big deal, Title 14 CFR Part 71 had to be amended, here is the Federal Register page that explains the rule change. By the way, you're not alone in being confused about the effective hours, apparently that language was erroneously included in the charts and had to be removed.


Does paragliding count towards total time? Does Paragliding count towards flight hours for "Total Time" in either commercial license 250 or the ATP 1500? If not, what are the cheapest ways to acrue raw "total time" hours? Can one do powered parachutes?

In the U.S., you can count the time as aeronautical experience in your logbook. But, that aeronautical experience can not be used to satisfy the requirements of Title 14 of the Code of Federal Regulations Part 61 unless the paraglide, powered parachute, or other aircraft meets the following stipulations per Part 61.51:

(j) Aircraft requirements for logging flight time. For a person to log flight time, the time must be acquired in an aircraft that is identified as an aircraft under §61.5(b), and is—
(1) An aircraft of U.S. registry with either a standard or special airworthiness certificate;
(2) An aircraft of foreign registry with an airworthiness certificate that is approved by the aviation authority of a foreign country that is a Member State to the Convention on International Civil Aviation Organization;
(3) A military aircraft under the direct operational control of the U.S. Armed Forces; or
(4) A public aircraft under the direct operational control of a Federal, State, county, or municipal law enforcement agency, if the flight time was acquired by the pilot while engaged on an official law enforcement flight for a Federal, State, County, or Municipal law enforcement agency.

This would eliminate the use of any aircraft flown under Parts 103, 105, & 107.
One less expensive way of getting flight time would be to fly as a safety pilot for someone flying simulated IMC using view limiting devices. If you are instrument rated, you can fly as PIC while someone else is the sole manipulator of the controls of the aircraft in real IMC under IFR.


How Centre of Gravity (CG) is adjusted? I've gone through the following questions on Stack Exchange and other few questions too:

Why is managing CG (centre of gravity) important?

How are the limits of the center of gravity chart established?

I still do have 2 questions in mind:

How do they adjust the fuel quantity/weight based on the passengers' weight on the plane? (was there any situation where few fat guys have been asked to move to front or back because I never saw any airliner weighing their passengers before boarding)
As the fuel starts burning, the pilot will fill/empty/exchange it from wing to wing or other storage location to balance CG, Will this cause imbalance (moving out of defined tolerances) in CG based on the passengers' weight?

The main issue is what is referred to as the Weight and Balance of the aircraft. When an aircraft is in flight, its weight and balance needs to be within a controllable range in order to ensure the plane can both recover from a stall condition and rotate on takeoff. This is visualized by the weight and balance "envelope:

As you can see, there are limits where the aircraft is not fit for flight. We must stay inside the drawn lines in the center.

To answer your detailed questions:

On airlines, a "Magic" number was used to approximate all weight for passengers and baggage. This caused at least one  notable accident: Air Midwest Flight 5481. As a result of this accident, policies were changed to get more accurate baggage and passenger weight.

In GA flight, it is not uncommon for pilots to ask for passenger weights. Usually, as a rule, we add a bit to that in case people are embarrassed (10%). It is very common for pilots to assign seating on smaller aircraft with heavier people sitting in a location where the distance to the datum is smallest (near the front).
Weight and balance can be moved out of limits by fuel burn. In fact, a few questions on the private pilot written exam deal with this exact scenario. Most planes have tanks near the CG, so they don't experience problems with fuel burn. In planes with an aft belly tank, the CG can move forward significantly and out of limits. This would cause the aircraft to be unable to pitch up as desired. Swept wing jets that use horizontal stabilizer tanks in the tail of the aircraft have computers and pumps to move the fuel as desired to keep their CG in the desired place.

Pilots of smaller/less traditional airplanes need to be conscious of this, and plan accordingly. Especially those with a-typical fuel tank positions. Pilots of larger commercial style aircraft are less concerned with the exact position of 1 or 2 large people or heavier bags because their aircraft has a much bigger capacity and less "sensitive" envelope. They still are affected by the physics, though, just like everyone else.


Is it the engines or the fuselage that limits service ceiling? Reading this article about the Northrop Grumman E8 it says the the aircraft will be able to fly higher after engine upgrades. Wouldn't the max service ceiling be limited by the fuselage design too?

Service ceiling is defined as the maximum altitude at which the aircraft can maintain a specified rate of climb (typically 500 feet/minute for jets).

The service ceiling is dependent on a number of design factors like,

Engine power
Engine efficiency at high altitudes
Wing design

The service ceiling is usually limited by a number of factors, and engine is important among them.

Thrust (or power) decreases with altitude (density) and at some point the aircraft reaches an altitude where even at the 'maximum rate of climb' speed, the engine will not be able to produce enough (excess) thrust to get the required rate of climb. This will be the service ceiling. Usually this is the limiting factor for GA aircraft.
In case of very powerful engines, the wings may stop producing enough lift, though this is rarely the case.
In case of transport aircraft, the service ceiling may sometimes be limited by the maximum altitude from which they can descend to 14,000 ft in less than a specified time (4 min). Commercial airliners are usually limited by this certification altitude.
In commercial airliners, the cabin pressure altitude is held constant (usually ~8000 ft ISA) and the differential pressure will cause stresses on the fuselage, but this is usually not the primary concern as fuselage design incorporates elements (for e.g. relief valves) to relieve pressure when this differential pressure goes beyond a limit.

In short, usually it is the engine, rather than the fuselage that limits the service ceiling.


Why should the centre of mass be ahead of the centre of pressure? Why is the centre of mass located ahead of the centre of pressure? And what would happen if centre of mass would be too close or too far away from the centre of pressure?

On most airplanes, the horizontal stabilizer provides a downward lift. The center of mass is between the nose gear and the main gears.

If the center of mass is too aft:

Stall (and spin) recovery will be difficult or even impossible
Increases the chance of tail strike
The plane will tip on its tail if the main gears are not moved aft

If center of mass is aft of center of pressure, then the horizontal stabilizer must provide positive (upward) lift; the tail structure must be made stronger to support the higher lift. The wings will be moved forward of the main gears to keep the aircraft balanced on the ground. Such designs are called Tandem wing. See also this question.


Are there any regulations about the distance between destination and alternate airports? I didn’t notice any distance regulations or recommendations regarding how far away an alternate airport may be. However, it is reasonable that,

Too close: The weather between the two is likely to be similar. If you are unable to land in one, you are unlikely to land the other.
Too far away: The fuel reserve is a concern, and we lose the purpose of the trip.

On an IFR flight plan, 14 CFR 135.233 requires

§ 135.223 IFR: Alternate airport requirements.
(a) Except as provided in paragraph (b) of this section, no person may operate an aircraft in IFR conditions unless it carries enough fuel (considering weather reports or forecasts or any combination of them) to—
    (1) Complete the flight to the first airport of intended landing;
    (2) Fly from that airport to the alternate airport; and
    (3) Fly after that for 45 minutes at normal cruising speed or, for helicopters, fly after that for 30 minutes at normal cruising speed.

Constraining from the other side, 14 CFR 91.169 requires

(c) IFR alternate airport weather minima. Unless otherwise authorized by the Administrator, no person may include an alternate airport in an IFR flight plan unless appropriate weather reports or weather forecasts, or a combination of them, indicate that, at the estimated time of arrival at the alternate airport, the ceiling and visibility at that airport will be at or above the following weather minima:
    (1) If an instrument approach procedure has been published inpart 97 of this chapter, or a special instrument approach procedure has been issued by the Administrator to the operator, for that airport, the following minima:
        (i) For aircraft other than helicopters: The alternate airport minima specified in that procedure, or if none are specified the following standard approach minima:
            (A) For a precision approach procedure. Ceiling 600 feet and visibility 2 statute miles.
            (B) For a nonprecision approach procedure. Ceiling 800 feet and visibility 2 statute miles.
        (ii) For helicopters: Ceiling 200 feet above the minimum for the approach to be flown, and visibility at least 1 statute mile but never less than the minimum visibility for the approach to be flown, and

The maximum distance for an alternate airport is limited by your aircraft’s fuel range, but practicality (not losing the purpose of the trip) will tend to be more constraining than math. The minimum distance depends on the weather.
Considering it from this perspective, given that the objective is safety, stipulating “at least X but no more than Y units of distance” would be inappropriate for similar reasons as to why we tend to think of fuel in terms of time rather than length.


Is it true pilots in a smaller aircraft have the option of using the right or left door as rudder, to offset the actual rudder if failed? So if the rudder fails or gets stuck in the “left” position a pilot could open the right door and it would essentially counter the effect?

In reality, in a strongly- deflected stuck-rudder situation, the pilot would be best advised to forget about the doors and just land the plane, selecting a runway with a strong crosswind component if at all possible.  After all, when landing with a strong crosswind, it's not that uncommon to hold the rudder at close to full deflection in the "downwind" direction.  If no crosswind runway is available, the pilot will just have to land the plane going a bit sideways-- no problem if the aircraft happens to have tricycle gear, like most do these days.

Obviously, in a stuck-rudder situation, steering corrections must be accomplished entirely via bank angle changes via the ailerons.  Keeping the rate of change of aileron deflection (and bank angle) low will help smooth things out.