What is Jet-A made of? I know that it is kerosene based, but what exactly goes into it? Proportions of the various components would be helpful.

Sadly, that information's pretty much impossible to give a general answer for, as it changes from batch to batch:

Refineries blend crude "to taste" as well as pricetag, so to speak, and the crude blend used as the refinery feedstock may change from batch to batch.
Process conditions in catalytic crackers and reformers can change depending on the point in the batch you're at, the incoming feedstock, and even the history of prior batches (say the last thing that ran through the cat cracker degraded the catalyst slightly...)
Jet fuels as-delivered may be a blend of multiple refinery batches and even the output of multiple refiners
Pipeline batching can also lead to subtle changes in fuel composition as it is transported -- pipeline operators try to "cut off" as much of the transmix as they can, but 100% isn't easy without wasting tons of fuel as transmix.  (Some pipeline operators will stick a "dumb pig" between high spec products, such as jet fuel, and their neighbors in the pipeline, but this is by no means universal.)

That said, you can make some determinations based off of a representative SDS for Jet-A, courtesy of ConocoPhillips:

The fuel consists of medium-weight hydrocarbons, from C9 to C16
The only specified aromatic component is napthalene, with a maximum concentration of 3%
No additives (anti-static, FSII, anti-oxidation, biocidal) are specified -- these are generally variable from batch-to-batch, depending on the specific purchaser (a large airport might get to spec these directly with the refiner, while the small GA 'dromes are at the mercy of whoever pulls up in the fuel truck)


Can perfect turn coordination automation be achieved by linking rudder to aileron? I was reading about the ERCO aircraft which apparently has a rudder-aileron linkage system that enables co-ordinated turns without the need for explicit rudder inputs. I've heard of Piper's having bungee cords for the same purpose.

Two questions:

Does such a physical linkage lead to perfectly co-ordinated turns under all conditions? Or is it only a coarse approximation & a skilled pilot can execute a better turn?
Why don't a lot more civil aircraft automate this co-ordinated turn feature? Is it because it is hard to automate or more that one wants the pilot to retain the ability to slip when necessary & execute un-coordinated turns sometimes?

Well, even if the latter were true, since 99% of all turns are co-ordinated one could just offer an override for the automated co-ordination feature, right?

A physical linkage is rather crude, but with a servo / feedback loop wouldn't it be possible to entirely eliminate the rudder pedals?

The mechanical linkage from control column (aileron) only addresses one of the things that affect coordination, the adverse yaw. It is the most significant one, but not the only. Other reasons you may need some rudder deflection in coordinated flight include:

Compensating for P-factor. At high angle of attack (slow flight) the propeller blade going up sees a lower angle of attack than the propeller blade going down, creating asymmetry of thrust. The effect depends on engine power and speed, making it too complex to compensate by just mechanical linkages.
The rotating propeller slipstream also creates asymmetrical force on the rudder, requiring compensation depending on engine power and speed.
In tail-draggers, the propeller precession creates rather significant yawing moment as the tail lifts off that needs to be connected using rudder, otherwise the plane could ground-loop. Tail-draggers generally require active control by rudder, because they are directionally unstable on the ground.
In multi-engine aircraft, asymmetric thrust in the event of engine failure. For multi-engine aircraft this is the most significant yawing moment that the rudder must be able to compensate.
And last but not least, rudder is needed to damp the Dutch roll. I've never heard that mentioned as problem in utility aircraft, but it is a big problem for transport aircraft and a reason why they usually come with a yaw damper.

The yaw damper is a feedback controller that monitors the lateral acceleration and other parameters (yaw and roll rate) and applies rudder to damp the dutch roll, and also to provide coordination to turns flown by autopilot where usually the autopilot directly commands the ailerons and rudder is left up the the yaw damper. So yes, providing coordination is possible, but not via simple mechanical linkages. And of course the rudder pedals still need to be there so uncoordinated flight is possible for any of the reasons already listed in Ron Beyer's answer.


Why do some cargo aircraft have windows? There are some cargo aircraft that have windows which are not covered. Look:

On the second deck above where it says "Hong Kong Asia's World City" the aircraft has 3 uncovered windows. Source: Airliners.net
Also here:

Source: Airliners.net

On the upper deck of the Martinair 747 the windows are not covered. My question is: if the aircraft is used for cargo, why do they leave the windows uncovered?

Some cargo aircraft do have limited seating, as mentioned in the comments it could be for the relief crew, load officer, or other employees making a hop on the plane. Here is a nice blog post about  flying in a cargo plane. This article covers it pretty well also.

(source)

Some cargo planes are also old passenger planes and some of the windows may be left in place.


Do airline pilots increase thrust when ordered to increase altitude by traffic controllers? Do airline pilots increase thrust when ordered to increase altitude by traffic controllers?  Do they simply use flaps, the yoke (or joystick in the case of airbus) and the stabilizers without any increase in thrust.  What is the altitude increase sequence or procedure .  Do they simply rely on auto pilot and if so does it increase thrust too?

Do airline pilots increase thrust when ordered to increase altitude by traffic controllers

Yes, without increasing thrust the act of ascending would reduce speed.

  Do they simply use flaps

No, flaps are not used to climb. They are used to increase the surface area of the wing in order to allow the aircraft to fly at slower speeds (for example, during approach & landing).

  What is the altitude increase sequence or procedure

Generally, and put simply, it is increase thrust then raise the nose.

  Do they simply rely on auto pilot and if so does it increase thrust too?

They may well use the autopilot to do it all, but some autopilots do not control the throttle so that would be done manually by the pilot while the autopilot controls the rate of climb.


What is the accuracy of distance and position calculation? I would like to learn about the flight distance calculation and positional accuracy requirement in aviation.

In practice, great circle distance is calculated between two airports but earth is more accurately represented with an ellipsoid and in this context, global positioning is based on WGS84 ellipsoid.

Is it useful to calculate geodesic (shortest path on the ellipsoid) rather than great circle on the sphere for more accurate estimation of the distance?

When thinking that flight routes are 3D, are 3D distances calculated in flight planning? In addition, are these 3D distances calculated with elliposidal cartesian (ECEF) coordinates (X,Y,Z) regarding ellipsoid height (height(MSL)+geoid height (undulation))?.

Does it make sense to calculate the flight distance in "meter" against "km" precision? If it is in nautical mile, what is the precision? e.g. 2394 nm or 2394.xx nm?

My another question is how accurate the 3D position of an aircraft is determined? What is the future perspective in this context together with satellite-based navigation and augmentation systems?

The aviation industry is in the process of moving to Performance Based Navigation (PBN) within Required Navigation Performance (RNP) airspace.  Using this structure the primary performance is measured by the Total System Error (TSE) which must be less than 2 times the RNP value 95% of the time. Example: In RNP 1 airspace the aircraft must maintain positional accuracy within 2.0 NM of its desired path 95% of the time. The standard for navigational equipment (FMS) is defined in RTCA document DO-283B, Minimum Operational Performance Standards for Required Navigation Performance for Area Navigation.

The TSE for an aircraft is broken down into three components; path definition error (PDE), position estimation error (PEE), and path steering error (PSE).  Your question directly relates to PDE.  The accuracy of PDE depends on several components, the primary one being the accuracy of the positional (fix) information published by the regulatory agency (FAA in the US) contained within the navigational database. For enroute and terminal airspace, the accuracy of fix information is less than 0.01 minutes of latitude and longitude or about 17 meters.

Using the data from the database and the WGS84 earth model, the FMS will compute lateral path data.  Lateral paths are computed as a geodesic on the surface of the WGS84 ellipsoid.

DO-283 specifies the following data (among other) resolutions for display and entry:

Distance:  0.1 NM for values <10 NM, 1 NM for values >=10 NM
Fix latitude/longitude: 0.01 min
RNP:  0.01 NM for values <1.0 NM, 0.1 NM for values >=1.0, and <10 NM, 1 NM  for values >=10 NM
EPU: 0.01 NM for values <1.0 NM, 0.1 NM for values >=1.0, and <10 NM, 1 NM for values >=10 NM
Present Position latitude/longitude: 0.1 min

DO-283 also states rounding of displayed data is desired.  For that reason internal FMS computations normally are performed to 1 decimal place more than the displayed resolution and then rounded.

From the above you can see that the displayed distance of a leg should be within 0.1 NM for distances less than 10 NM and 1 NM for longer distances.

As for your 3-D question, lateral (LNAV) and vertical (VNAV) navigation are computed separately.  VNAV is still predominately barometric based except for precision (GBAS) and near precision (SBAS) approaches which use WGS84 geometric height.

For positional data, along with the present position, the system must calculate an estimated positional uncertainty (EPU) as shown in the table.  The EPU calculation is quite complex and varies based on the source of the positional data (GPS, IRS, etc.)  This value when added to the PSE (cross-track deviation + errors) should be held within the RNP value.  As you can see form the structure of the EPU requirement, it is the most significant component of the system error.

Summary:

Calculating a geodesic path is required by the MOPS. Great circle is not acceptable.

Paths are calculated using lat/lon and baro altitude coordinates.  Distances are output in nautical miles; not feet, meters, or km.  Internally, the systems can use what ever they want.  Altitude is in feet or meters, depending on airspace rules.  The 3-D path is used to predict time of arrival at each fix along the route.

Positional accuracy (EPU) is calculated based on the selected nav sensor(s) using a number of statistical methods including Kalmann filters.


What is the minimum separation for navaids to work properly without interfering? What is the minimum separation between navaids (for VORs/DMEs and NDBs) for them to work without interfering, by regulation and by functionality?

VOR/DME and NDBs can't interfere with each other: they work on completely different wavelengths, so you could have a VOR right next to an NDB and they'll work just fine. Similarly, VORs on different frequencies won't interfere with each other; you could have them in close proximity as well. The only time you are likely to see navaids in close proximity is at an airport, which may have an NDB, VOR/DME, and multiple ILS in operation (an airport with 2 airstrips may have 4 ILS in operation: 1 per runway).

Where you do get interference is when stations are using the same frequency. A VOR has a service volume, a set distance it is designed to reach; in the US the high altitude service area is a minimum of 130 nautical miles at 45,000ft, but in practice in the right conditions you can pick them up further than that. Some stations are set at a lower power and have less range.


Can you guide me about the purpose of fine alignment in inertial navigation systems? I am new in inertial navigation field. I have some confusion about fine alignment process of INS. I want to ask that what is purpose of fine alignment?

I know by process of alignment we find the initial attitude matrix from body frame to navigation frame (reference frame) which normally take place by two step

Coarse alignment
Fine alignment

a. what is major difference between both steps?

b. how fine alignment refine the output of coarse alignment? Does Fine alignment minimize the errors to get more accurate output? or Does Fine alignment re correct the initial attitude estimate by coarse alignment?

c. why sensor bias like accelerator and gyro bias and lever arm error are  estimated in Fine alignment process.

I was a Doppler Radar & INS specialist for the Air Force in the 80s, and learned systems for the F4 (flying brick) and the triple carousel system for the C-5A. These systems used mechanical gyros in combination with accelerometers to establish a "Stable Platform". The carousel idea was state of the art then and rotated 1 revolution per hour to greatly reduce drift.

BATH was used for course alignment, which is an acronym for Best Available True Heading and local gravity to start level. It would then spin up and do fine alignment by sensing Earth rotation to determine True North. Typically this took about 30 minutes. Modern systems us laser gyros which aren't affected by mechanical drift.


follow up on the numbering system with a runway 9/27 I am approaching from the east travelling in a westerly direction will I land at the 9 end or the 27 end?  in other words, is the number on the end the compass heading or the direction of travel?

When I'm flying east, pointing east, with a compass heading of about 090 (i.e. 90 degrees), when I land straight ahead I will be landing on runway 9. Just after I pass over the runway threshold, at about 50 feet above the runway, I'll overfly the big "9" painted on the runway, and I'll touch down some hundreds of feet beyond it. If I then roll all the way to the far end, the eastern end, of the runway, I'll reach the "27" painted there.
Conversely, if I'm east of the runway & flying west, my compass heading will be about 270 and I'd land straight-in on runway 27. My compass heading as I'm landing (or taking off) corresponds to the designation of the runway that I'm using.


Does the explanation of why slower airfoils are more efficient involve less energy loss from heating or compression of the working fluid? We read time and time again, how more efficient slower airfoils such as helicopter rotors, props, and sailplane wings are compared with rapidly rotating fan blades or faster (still subsonic wings).  We also read where some people consider compression a negligible factor below a certain speed, even to the point of considering airflow < 200 mph as "incompressible"!

Yet looking at this commonplace and ubiquitous phenomena (indeed, while your prop is putting out 600 lbs of thrust, your wing is creating 4x more lifting force), is there a mathematical explanation for this involving the ideal gas law:  PV=nRT?

Can we visualize creating and maintaining a compressed "bow wave" ahead of a moving surface involves substantial amounts of energy even at lower speeds?

I have yet to fully understand why "it is better to move a lot of air a little than a little air a lot".

So you asked a whole bunch of things, and I'm not sure I really understand most of what you are asking, but I can maybe clarify this one part for you

  I have yet to fully understand why "it is better to move a lot of air a little than a little air a lot".

The equation for thrust is just Newton's second law F=$\dot m \Delta$V, where $\dot m$ is mass flow rate (kg/s) and $\Delta$V is the change in velocity of the air (exit velocity minus inlet velocity).  So, if you move 1 kg/s of air at 10 m/s, or you move 10 kg/s of air at 1 m/s, the thrust is the same.  Doesn't matter.

But, the equation of kinetic energy (well power really in this case) is $P=(1/2) \dot m (\Delta V)^2$.  So if you move 1 kg/s of air at 10 m/s, it takes $0.5*1*10^2$ = 50 W of power to do that.  But if you move 10 kg/s of air at 1 m/s it takes $0.5*10*1^2$= 5W of power to do that.  Exact same amount of thrust, but with literally 10X less energy required.  i.e. you need to burn way less fuel if you can move a lot of air at a low velocity than if you move a little bit of air a high velocity.


Should you wait to switch to the ground frequency until after crossing a runway? I've never had the opportunity to fly into a controlled airport with parallel runways, so I've never actually faced the situation. But, in the interest of being ahead of it, when would it be prudent to switch to ground frequency with this clearance (assume I just landed)?

  N12345, right on E, cross 27 R, contact ground .9

Should I call ground (or switch frequency, so I no longer hear the tower) before or after crossing 27 R? My by-the-book assumption would be immediately, as there's no "then" or "after crossing" or similar, but somehow that feels wrong. I suppose normally it doesn't really matter, but in the case of someone (which includes me, everyone makes mistakes) doing something wrong, where would they call me as I'm about to cross 27 R?

The reason I ask is that I saw exactly this case in a YouTube video quite a while ago (can't find it anymore though), where exactly this happened. The pilot was narrating for the video and stated he'd switch frequencies "now that he'd crossed the runway", at which point I started thinking about it.

Considering the situation, I would probably rather wait since there's an inherent delay when switching frequencies anyway, I might as well wait a bit longer, but knowing myself, if I hadn't thought about it ahead of time I'd probably switch right away. The only reason I can think of for saying it this way is if 27 R is not an active runway, but then again, reality does not always match what's in the book.

Remember that active runways are always the jurisdiction of the local (tower) controller. Even if a ground controller tells you to cross a runway, they have to clear it with the local controller next to them. So generally you switch frequencies when you have finished crossing the runway unless told otherwise.

I can tell you this is exactly how it works in Boise, Idaho where there are the parallels 10/28 L/R.

However, if you are unsure of any instructions a controller gives you, the basic rule is: ask. The tower controller won't mind, and will typically appreciate the clarification. Just read back the crossing instruction as normal, then ask.

  Right on E, cross 27 R, contact ground .9, N12345, and should I contact ground on the other side of 27R or immediately?


Why is this plane flying a circular track? Came across this on flighradar24 recently. It shows a jet making a very strange pattern. I would normally expect it to be some sort of aerial survey but seems unlikely in such a large aircraft at such a high altitude (I would expect to see a GA plane do this at lower altitudes).

Snapshot:

Closeup of snapshot:

Flight details (still might be able to find flight if you hurry and check out the latitude and longitude):

A recent article in Aviation Week showed a modified Bombardier Global 6000 with a "canoe" type fairing underneath the fuselage which typically houses a variety of radar or electronic intelligence (ELINT) equipment (link (free registration req'd) with pic) (alternate). The UK's RAF flies the Sentinel aircraft which is based on a prior Bombardier model, the Global 5000. So it's certainly possible that the track is a valid orbit path for surveillance in that area.

The USAF E11A is based on a Global 6000. It carries the BACN battlefield communication relay system which allows integrated, real-time communication across several, sometimes incompatible platforms. It is designed to operate at high altitudes to allow coms over mountainous terrain.

Since the Jalalabad airport is currently controlled by US armed forces from the adjacent Forward Operating Base Fenty, it would make sense that a communications aircraft would loiter over the area.

If it is a military flight, it looks from the flight path that it may have originated from Kandahar, where the USAF has a base.

(Source)


How much does it cost to fly a plane? INCLUDING lessons, and everything else It seems very difficult to find this information on any legitimate sites, so I'm going to ask here. I know nothing about flying, and this wouldn't happen for years to come, but I am curious.

Let's say I want to someday go into my backyard, get into my plane, and have  flight to start the morning, then land back in my property (which would obviously have to be quite large).

How much, generally speaking, would ALL of the following cost me:

-Flight lessons, from complete noob to completely done

-Small, modest, low-tech, possibly used, two seater personal plane

-reasonable range for the upkeep costs of a plane (fuel, maintenance, etc.)

I realize that this is difficult question to answer, but I'm looking for a very general, rough idea. At least an order of magnitude estimate.

As Ben says, it depends a lot on which country you're in: Both due to natural differences in the cost of things (Germany is more expensive than, say, Vietnam for instance) but also because different countries have different requirements for how much experience you need before they hand you a license.

But as an example let's go with the USA, based on the prices from my old club in MA:

Going from zero experience to a private pilot license will typically cost you around \$8-9k. A bit less if you learn quickly or a bit more if you need extra practice. If you already bought your own plane then this will be reduced quite a lot. The exat figures will depend on how much time you need with an instructor vs how much time solo but you can, ballpark estimate, halve the cost by using your own aircraft. This only works in some countries, though. Others (including EASA in Europe, I think) require a 'company' aircraft.
A  basic plane will cost anywhere between \$15-25,000. The cheapest I've seen recently was just over \$13k but it looked like junk.
Fuel costs around \$6.50 per gallon and you use anywhere from 5-8 gallons per hour, typically. Maintenance depends a lot on the plane, my old flying club used to spend about \$3500/year on each of their Cessna 172s.  You also have insurance on top of that, which is likely to be around \$2.5k


Is it quiet in the cockpit when flying faster than the speed of sound? Is it quiet in the cockpit when flying faster than the speed of sound or is the noise from air resistance just too loud?

Similar question: is it quieter at the front of an airliner flying faster than the speed of sound because the engines are behind you (comparing to the rear of the plane)?

No, for two reasons:

Speed of sound is always relative to the material the sound propagates in; it moves faster through denser media, such as the aluminum structure of the aircraft itself. The aircraft's structure moves with the aircraft, so the vibrations of the jet engines will be transmitted to the cockpit/cabin at the same speed as when the airplane were flying subsonic.
The air inside the cockpit is still, and so sound within this local bubble is unaffected by the speed of the bubble itself (and so sound can travel faster than sound). If this weren't true then radios and other cockpit sound sources like alarms would be inaudible at supersonic speeds, which would be a major safety hazard and tactical disadvantage to supersonic flight.

You actually don't even have any significant aural cues inside the cockpit that you've exceeded Mach 1; you have to rely on your airspeed gauge to tell you.


Where does one obtain a RAREP? Where can I find Radar Weather Reports (RAREPs)? Are they still used? They are not anywhere on the aviationweather.gov website.

Coded RAREPs (Radar Weather Reports) and SDs (Storm Detections) may still be used to exchange data between radar stations, but for human users they seem to have been superseded by visual displays that provide a more human-friendly visualization of the same information, such as at http://www.aviationweather.gov/radar.  The PHAK you linked to (published in 2008) is likely out of date on this.  (But this is the most recent PHAK available.)

From http://weatherjackwilliams.com/answers-weather-radar/ :

  The NWS Aviation Weather Center (AWC) doesn’t have any links to the
  coded SD/ROB reports, but does link to the Radar Summary chart, which
  is complied from these  reports.

This information is also incorporated into a standard weather briefing for a particular flight plan.  The DUAT system used to provide an "SD (Radar Weather Reports)" section in its briefings, but DUAT is no longer available.  DUATS instead has a section titled "Radar Summaries" in its briefings.


What could cause a distinct tube of condensation over a wing? I recently saw something I've not previously encountered: shortly after take-off, for a few seconds, an extremely dense tube of condensation rose from about 75cm in front of the wing, in-board of the engine, to a height of about 50cm above the wing and then raced back over it.

The tube of condensation was exceptionally well-defined. It appeared to have a diameter of around 15-20cm, which hardly varied, and a very circular cross-section. Its surface was smooth, and it appeared and a few seconds later disappeared as abruptly as if controlled by a switch.

As an illustration of some of the airflow over that portion of the wing, it was quite remarkable - I expected it to be more turbulent than that.

What was the likely source of this well-defined condensation? It appeared to originate from below and in front of the wing.

I've seen condensation form and travel across portions of the wing many times before, but never in this fashion, so I was thrilled to see it.

The aircraft was a 767-300 if that makes any difference.

What you might have seen is the condensation due to the vortex generated by the engine nacelle chine. The image below shows a vortex being generated by the chine.

Image from flickr.com. Photo credit- Frank Starmer


What is the reason for this unusual flight path? Last week, flight AA9675 flew from MIA to TUL. It took this very unusual flight path:

It's an ad hoc flight number, so it's not a regularly scheduled flight. You can see there was a line of thunderstorms moving across at the time. But that alone does not explain the route. FlightAware shows the flight plan that was filed.

After leaving Miami it skipped the first few filed waypoints. But after it left Florida it followed the plan as filed from one VOR to the next, in a big circle around the Midwest and finally landing in Tulsa.

My only guess as to the reason for such an unusual route is that, due to the line of storms, it's some kind of contingency flight. Maybe they were anticipating delays and kept a plane airborne so that it could be quickly re-routed if necessary. I've been told that FedEx does this during peak season, but I've never heard of a passenger airline doing it.

Does anyone have an explanation for such an unusual flight path?

My guess is the captain requested and the dispatcher approved an excessive amount of fuel to deal with the crossing of the long line of weather.  The flight plan would have to reflect being able to burn off that excess fuel to be able to land BELOW the maximum landing weight of the plane. The crossing consumed far less fuel than expected so the crew had to burn off the excess fuel by flying the filed flight plan.  Or they could have just wanted to fly the filed flight plan because flight crews get paid by the hour and they would have just about doubled their pay for that leg.


How did the term 'Buttered the bread' originate? I've heard this term used a few times to describe an exceptionally smooth landing

Back when actual butter was the main spread to put on bread, it took a very gentle touch to spread butter straight from the refrigerator (icebox) without tearing up the bread.  Thus, a very smooth landing might be said to have "buttered the bread" because it went on smoothly enough to keep from tearing anything up.

This probably also evolved into "greased it on" or "greaser" to refer to a similarly smooth landing.


Can I accept a SID if I can't make the required climb gradient on a single engine but have no problem on two engines? Can I accept a clearance containing a Standard Instrument Departure (SID) with a climb gradient that I can easily make on all my engines but can't make the required gradient on one engine inoperative?

If I can and I lose an engine on departure what should I do so I don't hit anything?

Depending on certain factors, you can accept a SID clearance knowing that you cannot make the required climb gradient with one engine inoperative (OEI).

The FAA Aeronautical Information Manual (AIM) 5-2-8 ODP and SIDs states this:

  ODPs and SIDs assume normal aircraft performance, and that all engines are operating (AEO).  Development of contingency procedures, required to cover the case of an engine failure or other emergency in flight that may occur after liftoff, is the responsibility of the operator.

This answer begs another question and what are some contingency procedures you can consider when accepting a SID when the required climb gradient is not possible with OEI procedures?

The FAA lists two possible places for this information:

AC 120-91 - Airport Obstacle Analysis
Instrument Procedures Handbook (FAA-H-8261-1) Chapter 1.

AC 120-91 talks about how runway analysis is used to comply with Part 121 / 135 obstacle climb requirement.

Instrument Procedures Handbook provides additional information on how OEI takeoff obstacle clearance requirements are different than TERPS requirements.  Besides using runway analysis, there isn't a lot of additional information on contingency procedures.

Here are my contingency procedures in the preferred order

Runway Analysis - Let an engineer figure out the maximum weight to takeoff and be able to climb above the obstacles
Radar vectors - Once ATC issues the words "Turn left / right heading xxx°" they are equally responsible for terrain clearance
See and avoid the terrain (VMC only) - If we can see the obstacles... hopefully we can miss them.  Of course, mountains don't care if you can see them or not.  They don't move.
Obstacle Departure Procedures (ODP) using OEI calculations.
SID using OEI calculations.

It would be great if others come up with a different set.  I would love to see them.   I will typically work through this listing and if I am taking off from an airport without radar services in IMC where I do not have runway analysis, I need to be able to make the ODP or the SID on OEI performance.


What is this plane and what are the rockets on the back used for? While reading this question I saw an image of a plane marked as a US Marines plane of some sort with thrusters or rockets of some sort attached to the sides just past the CG. What plane is this and why are the rockets there?

Image:

As the source linked next to the image in the other question says, it is a C-130 performing a "rocket assisted takeoff".

These are performed to safely achieve V1 on short airfields, where the aircraft would not be able to take off otherwise.

The rockets (or "bottles") use solid fuel, so they are usually single-use.

I have no data on the thrust provided by one of them, but the wikipedia article mentions that a "smaller version" made for the civilian market, could deliver "250 pounds of thrust for 12 seconds", so it is reasonable to expect that the thrust provided by the larger bottles would be larger.


Why do we have to perform a normal APU shutdown if a fuel spillage occurs? I was reading in the limitations chapter of the A320 which stated that if a fuel spillage occurs we have to perform a normal APU shutdown what is the reason behind this?

I would reason that any source of ignition,such as an APU or vehicle could ignite the spill causing a fire.


When can a pilot disobey ATC commands? The title really asks it all: When can a pilot disobey ATC commands?.

Of course, the pilot has the final decision, but when would the pilot really disobey someone in ATC with much more knowledge of planes and other potential hazards near by?

In case of emergencies, yes. The pilot in command has the final authority and responsibility for safety of the flight and can disobey ATC commands in case of emergencies. The reasons for that and the results will decide the consequences.
From 14 CFR §91.123 Compliance with ATC clearances and instructions:

(a) When an ATC clearance has been obtained, no pilot in command may deviate from that clearance unless an amended clearance is obtained, an emergency exists, or the deviation is in response to a traffic alert and collision avoidance system resolution advisory.
(b) Except in an emergency, no person may operate an aircraft contrary to an ATC instruction in an area in which air traffic control is exercised.

From 14 CFR §121.557   Emergencies: Domestic and flag operations:

(a) In an emergency situation that requires immediate decision and action the pilot in command may take any action that he considers necessary under the circumstances. In such a case he may deviate from prescribed operations procedures and methods, weather minimums, and this chapter, to the extent required in the interests of safety.

Emphasis mine. Obviously, it would be prudent for the the pilot (and required under FAR 91.123(c), as @Pondlife points out) to report the deviation to the ATC as soon as possible.


When helicopters are instructed to air-taxi direct to an airport location, are they allowed to pass above other aircraft and people? When helicopters are instructed to air-taxi direct to a location at the airport, are they allowed to pass above other aircraft / people / road traffic?

No. A helicopter taxiing has to follow the exact same rules as any other taxiing aircraft.


What is the farthest commercial flight on a B737-800 currently? Can anybody name the airline, distance and respective city pair of the farthest (not necessarily longest) nonstop flight on a Boeing B737-800 (currently or in the past)? I'm not interested in empty delivery or ferry flights, but in revenue, commercial flights with this aircraft type.

I believe this is GOL's Orlando->Brasilia flight at 3,778 miles. Prior to that it was Newburgh to Bergen at 3,456 miles.

Lufthansa has a 737-700 but it is a Boeing Business jet equipped with extra fuel tanks and only 86 seats which makes a Frankfurt to Pune 4,158 mile flight.

Source


Which hand do fighter pilots use for the control stick? Here is a question that has been bothering me for a while. Do right-handed fighter pilots use their right hand to hold the control stick? And do left-handed fighter pilots use their left hand?

Or is it the other way around? Or do they maybe use both hands a lot of the time? It also brings up the question as to what the other hand is expected to do and which side of the cockpit the most common control buttons are on.

My guess is that since most people are right handed, they use their right hand. There's also triggers on the yoke so it seems all the more likely that the right hand is used for right-handers.

I'm asking because you look at video games and their controllers. They always use the left joystick for moving the character. In the case of flight simulators, the left joystick is used as the 'stick' or yoke. So you're pretty much left with no choice but to use your left thumb. Not saying this is awkward for video games, however, on those big joysticks for PC games, I remember I always used my right hand.

Also, let's ignore civil commercial piloting because those seem to usually use steering wheel type controls, not a traditional stick. Please let me know if you're a fighter pilot when you answer, because the triggers on the yoke have an effect on which hand you're most comfortable with.

Most fighter pilots, regardless of their handedness, use their right hand to fly the stick, and their left hand to move the throttle(s)/PCL (Power Control Lever). This is just how most fighter cockpits are set up, with the power on the left side.

The sticks are also not really usable for a left hander because a few of the buttons would be inaccessible with a left hand on the stick. In some cases (like the F-16), the cockpit uses a sidestick layout, with the stick on the edge of the cockpit, rather than in between the pilot's legs.

So no, it would not really be possible for left-handed pilots to fly with their left hand on the stick for long periods of time (I will note, that if you need to select something on the right side, most will hold the stick lightly in their left hand for a brief second, actuate the item with their right hand, and then switch back) unless the entire cockpit were redesigned, which is just not worth it.


What was the Vmca of the 2-engine 747 config the El Al 1862 crew faced, and could they have landed the plane at a corresponding Vref? In the El Al 1862 crash, the flight crew lost control of their 747 in what basically amounts to an aggravated Vmca roll during approach after two engines detached from the aircraft, causing the loss of two hydraulic systems and damage to flight control surfaces on the right wing.

What was the actual Vmca of the aircraft in that damaged configuration though?  Further, if they had not been focused on trying to get down to a normal configuration Vref and instead sped back up as soon as they started nearing full control deflection, thus increasing their control authority, could they have gone around and then reconfigured partially for what would be an increased Vref, then landed the aircraft at that increased speed?  Schiphol has no shortage of runway, after all...

The accident report says

  2.4.2 Performance

  An energy analysis was performed based upon altitude and airspeed
  data from the DFDR. It should be realised that this method does not
  allow extrapolation of performance capabilities in other conditions
  then those encountered during this flight. Based on this analysis the following conclusions can be made:

  Marginal level flight capability was available at 270 knots and go
  around power with a limited manoeuvring capability;
  At MCT thrust and 270 knots IAS there was no level flight capability;
  Performance degraded below about 260 knots at increased angles
  of attack. Deceleration to 256 knots resulted in a considerable sink
  rate.

(my emphasis)

My interpretation is that it is not appropriate to define a Vref for a 747 in that configuration.

Glossary

Vmca = Minimum Control (air) Velocity. Min speed that directional control can be maintained. Vmca2 for two engines (critical and inboard on same side) of a 4-engine aircraft.

Vref = Speed required as the landing runway threshold is crossed at a height of 50 feet in landing configuration.

MCT = Maximum Continuous Thrust. Thrust levels higher than this can only be maintained for a short time (e.g. minutes).


If indicated air speed does not change can the amount of lift change? A friend and I were having a discussion. He says that if you are flying in a 50 knot headwind and the wind suddenly stops, the airplane will lose lift.

I say that this will not result in a loss of lift because, although the ground speed will change, the indicated airspeed does not change and no lift will be lost.

He then brought up microbursts and wind shear as an example of wind direction changing causing a change in lift, however I am not so sure. I think in those examples it is actual downdrafts pushing the plane down or the movement of air over the wing in a non-coordinated way, similar to how the air in a slip does not pass over the wing in a way that generates the most lift.

Does anyone have an answer? If an airplane is in a 50 knot headwind and the wind suddenly stops, will the airplane lose lift? What is the actual cause for loss of lift in a microburst or in wind shear?

Your friend is right.  Wind shear will greatly degrade or increase the lift depending on the change in direction and velocity of the shear.

If you are flying at 50 KIAS into a 50kt headwind, your ground speed will be zero knots.  If the wind shears to perpendicular to your flight path, your airspeed drops to zero knots and you fall out of the sky.  If it shears to 180deg in, says a microburst your airspeed is now -50kts or 50kts from the tail end almost certainly causing a departure from controlled flight.  In both cases at low altitudes the result is almost certainly fatal.

Conversely, if you were flying at 50KIAS and had a 50kt tailwind and the wind then sheared 180deg to a 50 kt headwind, you would abruptly jump to an airspeed of 100KIAS.  The airplane would rise very rapidly; you would feel the vertical acceleration in your seat.  This situation isn't as dangerous as shearing to a tailwind at low altitudes/speeds but it could be dangerous if one was cruising past Vno (yellow arc) where there is a risk of structural damage to the aircraft.

Your friend is right; microbursts are very dangerous.  The combination of wind shears as much as 90kts and severe downdrafts in the apex of the storm make it one of the most hazardous weather phenomena an aircraft can encounter.  They can even be catastrophic to large airliners at low speeds.  On August 2, 1985, a Lockheed L-1011 TriStar encountered a microburst while on final for KDFW and consequently crashed, killing 137 people.


In a flight plan, does it make any difference to write an increase of the flight level instead of writing a cruise climb? According to ICAO 4444, a change of speed or level should be written in item 15 of the flight plan according to these rules:

  Change of speed or level (maximum 21 characters)
  The point at which a change of speed (5% TAS or 0.01 Mach or more) or
  a change of level is planned, expressed exactly as in (2) above,
  followed by an oblique stroke and both the cruising speed and the
  cruising level, expressed exactly as in (a) and (b) above, without a
  space between them, even when only one of these quantities will be
  changed.

  Examples:

  LN/N0284A045
  MAY/N0305Fl80
  HADDY/N0420F330
  4602N07805W/N0500F350
  46N078W/M082F330
  DUB180040/N0350M0840

  Cruise climb (maximum 28 characters)
  The letter C followed by an oblique stroke; THEN the point at
  which cruise climb is planned to start, expressed exactly as in
  (2) above, followed by an oblique stroke; THEN the speed to
  be maintained during cruise climb, expressed exactly as in (a)
  above, followed by the two levels defining the layer to be
  occupied during cruise climb, each level expressed exactly as
  in (b) above, or the level above which cruise climb is planned
  followed by the letters PLUS, without a space between them.

  Examples:

  C/48N050W/M082F290F350
  C/48N050W/M082F290PLUS
  C/52N050W/M220F580F620

Does it make any difference to write an increase in the flight level instead of writing a cruise climb? Are they different flight maneuvers?

They are different things. A cruise climb allows you to continually climb at your own rate to achieve maximum efficiency. This is what Concorde used to do. However this requires ATC to "give you" all of the levels from the bottom to the top of the climb, which is impractical with the volume of traffic.

Instead, we use set levels. We can "step climb" to another level when we become light enough to do it, and this way ATC only has to block off one level at a time for us.


What is the "Brake to Exit" feature on the Boeing 777X? I have come across a new feature called BTE (Brake to Exit) on the 777X, but I am unable to find any documentation related to that. There are vendors who are working on this technology for the 777X.

It is a system that Airbus already uses in the A380
and some A350's. They call it BTV (Brake to Vacate).

It allows the pilot to select a certain runway exit in advance (e.g. while approaching).
After touchdown, the plane automatically brakes so it can vacate the runway at that given exit.

Airbus says:

  When the pilot chooses a runway exit point, the system indicates the estimated runway occupancy time and the minimum turnaround time. During the subsequent landing phase, and according to encountered runway conditions (i.e. 'wet' or 'dry'), the aircraft's deceleration is automatically regulated so it reaches the chosen exit at the correct speed.

(emphasis mine)

The BTE system by Boeing is a similar system with a different name. A related article in Avionics International about the B777X states:

  “We have also added new safety features like optimal runway exiting and brake-to-exit, which will allow a pilot to tie an airplane’s rollout and stopping distance to a specific runway exit,” said Kirk Scarbrough, Boeing’s 777X systems chief engineer.

See also

What is Brake To Vacate (BTV)?
FAST magazine from Airbus, issue #44(PDF, 10MB) from July 2009, section "Brake-to-Vacate system", pages 17-25


Can you identify this old cockpit canopy? I stumbled across a cockpit canopy in the woods. What type of markings should I be looking for to identify this? And where exactly should I be looking for markings to identify this piece? Here is a photo of what I found.

Looks like a B-47 Stratojet to me.

Image from wattflyer.com

I'm not sure about this particular model. But usually the canopy will have part number markings on it, which can be correlated to the program.

Also, see the B-47 Stratojet association's page.


Have any passengers crashed planes? The question Are pilots allowed to let passengers fly the plane? is interesting to read, noting that pilots are permitted to allow passengers to fly.

I recall an Air Crash Investigation episode (AFL593) where the pilot pretended to allow his son to manipulate the controls of an airliner, without realising the autopilot had been disconnected, resulting in an accident.

I'm wondering how commonplace this is? Is this an isolated incident?

On the flip-side, I've heard of at least 3 occasions where passengers have successfully landed planes, e.g:

No passengers have crashed an airplane while the pilot was letting them fly.

In this situation, the PIC crashed the plane because he didn't do his job as the captain and final authority for the safe operation of the airplane.

Letting a passenger fly would most likely be listed as a "contributing factor" by investigators looking into an accident where this happened, but responsibility for the crash lies squarely on the PIC.


After takeoff, why do some airlines' flight attendants rise from their jump seats earlier than other airlines'? For one airline (Air France, IIRC), I've heard

a cabin chime (presumably to apprise flight attendants ("FA") that they can get up)
then saw FAs leaving their jump seats,

far sooner after rotation than other First World airlines.

Why does the time of rising from the jump seat differ among airlines?
Isn't getting up later safer (when the aircraft's pitch is less)? I'm curious if Air France cares less about its FAs' safety.

The industry standard is to switch the seat belts signs off while crossing 10,000 ft. And this is usually the moment when flight attendants get up. But really depends on company policies as you saw. Even within the same airline there may be different standards for different fleet, which actually depends more on timing for service that on safety.

In any case, the decision to let the flight attendants to get up depends solely on the captain, who is the one looking after their safety. If he suspects turbulence ahead he will delay the signs as much as required.

You have also to consider that flight attendants receive special training on how to move safely around the aircraft, even with severe unexpected turbulence. If you encounter some light turbulence in your next flight pay attention on how they move: looking for a stable position opening the legs more than usual walking and pointing their hands to places they could grab immediately.


Did Biplane pilots turn off their engines before landing? I read or heard one time that radial engine biplane engines were turned off just before touchdown because if the throttle was used, the torque could cause the wing of the plane to contact the ground and a lot of pilots were killed just landing biplanes. Is that true?

Did Biplane pilots turn off their engines before landing?

Sometimes--

Rotary engines had rather primitive throttle arrangements, so a pilot would often use a "coup" button or "blip" switch, mounted on the control stick, to "blip" the ignition on and off and give partial power.

However, an alternative technique was recommended for some rotary engines:

  By 1918 a Clerget handbook advised maintaining all necessary control
  by using the fuel and air controls, and starting and stopping the
  engine by turning the fuel on and off. The recommended landing
  procedure involved shutting off the fuel using the fuel lever, while
  leaving the blip switch on. The windmilling propeller made the engine
  continue to spin without delivering any power as the aircraft
  descended. It was important to leave the ignition on to allow the
  spark plugs to continue to spark and keep them from oiling up, so that
  the engine could (if all went well) be restarted simply by re-opening
  the fuel valve. Pilots were advised to not use an ignition cut out
  switch, as it would eventually damage the engine.[7]

  Pilots of surviving or reproduction aircraft fitted with rotary
  engines still find that the blip switch is useful while landing, as it
  provides a more reliable, quicker way to initiate power if needed,
  rather than risk a sudden engine stall, or the failure of a
  windmilling engine to restart at the worst possible moment.

(Source: https://en.wikipedia.org/wiki/Rotary_engine#Monosoupape_rotaries, quoting Nahum, Andrew (1999). The Rotary Aero Engine. NMSI Trading Ltd. pp. 44–45. ISBN 1-900747-12-X.)

The key here is "rotary", not "radial", and regardless of which technique was used, the concern wasn't to avoid a hazard from engine torque or other related effects per se, but just to control the power output of the engine to allow the aircraft to descend for landing.

Of course, at other times, such as when taking off, the gyroscopic reaction to the whirling mass of the engine was a very significant factor while flying with a rotary engine, and the low ground clearance of the lower wingtips of most biplanes wouldn't have helped matters.

You can read much more here--

How are rotary engines controlled?

https://en.wikipedia.org/wiki/Rotary_engine

http://www.theaerodrome.com/forum/showthread.php?t=17121

http://www.theaerodrome.com/forum/showthread.php?t=2302&page=1&pp=10


What is the 'end plate' effect? When talking about T-tail configuration, I don't understand the statement that, "The vertical tail can be shorter due to the end plate effect of the horizontal tail."

What exactly is the endplate effect and how does it affect the aerodynamic characteristics of the tail?

An end plate on a lifting surface (which the vertical tail is, during a yaw maneuver) reduces tip vortex formation, which means less lifting area is needed to produce the same lift force.  It also significantly reduces induced drag, though the parasitic drag of the plate is usually a net loss unless, as in the case of a horizontal tail, the "plate" serves some other function that would be required anyway.

Whitcomb and newer design winglets use careful design to give similar effects with less, or even negative drag -- but you'd need a horizontal tail anyway, so the reasons not to have a T configuration boil down to structural weight, elevator blanketing in a stall, and control routing issues.

For an example of an aircraft that makes good use of tip plates to allow a shorter wingspan, look up the Bumblebee -- at least at one time, it was the dimensionally smallest piloted aircraft ever flown, and it critically depended on tip plates on both upper and lower wings to produce enough lift to fly.


What is transmitting this radio signal @~110.515MHz and for what purpose? I was scanning the local aviation radio frequencies, and came across an odd signal (listen to a recording here).
It's at around 110.515MHz, and it seems strong within a 30 mile radius of Shropshire, UK (haven't tried tuning in further afield).

Not sure if it's relevant, but there are a couple of RAF bases nearby (RAF Shawbury and RAF Cosford).

I presume it's a navigation aid, but couldn't find anything listed on that frequency.
I was hoping someone would recognise the sound and be able to tell me what equipment is transmitting it (e.g. NDB).

Well, the SDR dongle paid off - mystery solved.

It turns out, the signal was actually at 153.2MHz, but was somehow breaking through into 110.515MHz on my handheld scanner.

The signal originates from a high power pager transmitter using the FLEX protocol. As this is plain text, I decoded some of it using an excellent open source application called PDW, and have listed it below for reference and general interest (sensitive information has been redacted!).

  0074162  23:12:31 30-06-15 FLEX-A    ALPHA   3200   31:Jun 30 23:11 Trim Line 2 L359 Error Check 01 Override 010312 30-JUN-2015 23:10:49
  0000002  23:12:56 30-06-15 FLEX-A    ALPHA   3200   THIS IS A TEST PERIODIC PAGE SEQUENTIAL NUMBER  0069
  0121518  23:12:59 30-06-15 FLEX-A    StNUM   3200   31948
  1734139  23:13:01 30-06-15 FLEX-A    ALPHA   3200   61:Jun 30 23:12 Term B  Page-fail test
  1756286  23:13:24 30-06-15 FLEX-A    ALPHA   3200   PIN 6840 PLS CALL DSCC ON 08457 500***
  0118459  23:13:46 30-06-15 FLEX-A    ALPHA   3200   20150630 23:13 boc1web02.servstream.com: conn CRITICAL ALERT
  0000002  23:14:03 30-06-15 FLEX-A    ALPHA   3200   THIS IS A TEST PERIODIC PAGE SEQUENTIAL NUMBER  0070
  1734139  23:14:09 30-06-15 FLEX-A    ALPHA   3200   62:Jun 30 23:13 Term B  Page-fail test
  0076963  23:14:29 30-06-15 FLEX-A    ALPHA   3200   55:Jun 30 23:13 23.13hrs Zone 14 L550 down 15 Mins maint in attendance FROM: GB50-AFENNEL3
  0074162  23:14:46 30-06-15 FLEX-A    ALPHA   3200   32:Jun 30 23:13 Trim Line 2 L359 Error Check 01 Override 010312 30-JUN-2015 23:12:42
  0074179  23:14:48 30-06-15 FLEX-A    ALPHA   3200   19:Jun 30 23:13 Z2A LH Stn 200  Main Call 30-JUN-2015 23:13:22
  0074194  23:14:50 30-06-15 FLEX-A    ALPHA   3200   56:Jun 30 23:13 23.13hrs Zone 14 L550 down 15 Mins maint in attendance FROM: GB50-AFENNEL3 FROM: GB50-AFENNEL3
  0107291  23:14:50 30-06-15 FLEX-A    StNUM   3200   2422085
  0074076  23:14:50 30-06-15 FLEX-A    ALPHA   3200   60:Jun 30 23:13 Fac 1670 More than 20 I/P on conv 30-JUN-2015 23:11:30
  0086317  23:14:52 30-06-15 FLEX-A    ALPHA   3200   36:Jun 30 23:13 Dodo Panel 23 Entry Movement Alarm 000065 30-JUN-2015 23:12:03
  0000002  23:14:56 30-06-15 FLEX-A    ALPHA   3200   THIS IS A TEST PERIODIC PAGE SEQUENTIAL NUMBER  0071
  0067432  23:14:59 30-06-15 FLEX-A    ALPHA   3200   71:Jun 30 23:14 Water Test WATER TEST SUMP LEVEL HIGH 001215 30-JUN-2015 23:14:46
  1754937  23:15:16 30-06-15 FLEX-A    ALPHA   3200   'Adv' 7440298 30/06/2015 23:08:33 tight chest, struggling to breathe, EMAS ETA 11 mn, Priority RED2 Age 59 Incident area - KETTERING ** ****** ** NN16 ***
  0067432  23:15:22 30-06-15 FLEX-A    ALPHA   3200   72:Jun 30 23:14 Skid RETURN PROBLEM CHECK SKID RETURN Tested o.k. 30-JUN-2015 23:12:25
  1734139  23:15:24 30-06-15 FLEX-A    ALPHA   3200   63:Jun 30 23:14 Term B  Page-fail test
  0086317  23:15:44 30-06-15 FLEX-A    ALPHA   3200   39:Jun 30 23:14 Dodo Panel 6 P&F Emergency Stop relay 125KN1 - 400301.08 30-JUN-2015 23:13:32
  1734136  23:15:46 30-06-15 FLEX-A    ALPHA   3200   19:Jun 30 23:14 Term A  Page-fail test
  0067154  23:15:50 30-06-15 FLEX-A    ALPHA   3200   Fr:nocteam Su:Escalate PQV-73575-125 Tx:Auto escalation of ticket (3 hour rule) Ticket: PQV-73575-125 Queue: VelociX Date raised: 2015-06-30 20:11:27 Subject: ANTEL New asset request
  0117556  23:15:54 30-06-15 FLEX-A    ALPHA   3200   PLS CALL DUTY OFFICE
  0000002  23:16:03 30-06-15 FLEX-A    ALPHA   3200   THIS IS A TEST PERIODIC PAGE SEQUENTIAL NUMBER  0072
  0111087  23:16:07 30-06-15 FLEX-A    StNUM   3200   71301
  0118459  23:16:16 30-06-15 FLEX-A    ALPHA   3200   20150630 23:15 boc1backup.siops.net: msgs CRITICAL ALERT
  1734139  23:16:31 30-06-15 FLEX-A    ALPHA   3200   64:Jun 30 23:15 Term B  Page-fail test
  0074208  23:16:37 30-06-15 FLEX-A    ALPHA   3200   69:Jun 30 23:15 Warning : BODY DELIVERY STN 1 OVERCYCLE * BD SKID BD SKID (52)
  1734136  23:16:54 30-06-15 FLEX-A    ALPHA   3200   20:Jun 30 23:16 Term A  Page-fail test
  0074221  23:16:54 30-06-15 FLEX-A    ALPHA   3200   09:Jun 30 23:15 Warning : BODY DELIVERY STN 1 OVERCYCLE * BD SKID BD SKID (53)
  0120075  23:16:56 30-06-15 FLEX-A    ALPHA   3200   PLS CALL 12F ON 42848 2ND CALL
  1734139  23:17:39 30-06-15 FLEX-A    ALPHA   3200   65:Jun 30 23:16 Term B  Page-fail test
  1756806  23:17:41 30-06-15 FLEX-A    ALPHA   3200   PLS CALL ***** ***** - ADDENBROOKES ON 01223 257 ***
  0121619  23:17:42 30-06-15 FLEX-A    ALPHA   3200   P2 TS 3170
  0074162  23:17:46 30-06-15 FLEX-A    ALPHA   3200   34:Jun 30 23:16 Trim Line 2 L359 Error Check 01 Override 010312 30-JUN-2015 23:15:30
  1728604  23:18:05 30-06-15 FLEX-A    ALPHA   3200   41:Jun 30 23:17 ****** ******** 07711 239 ***
  0067432  23:18:07 30-06-15 FLEX-A    ALPHA   3200   73:Jun 30 23:17 Conv 11 Conv 1 Starved Load stn Blocked 30-JUN-2015 23:14:55
  0090980  23:18:07 30-06-15 FLEX-A    ALPHA   3200   30/06/2015 23:15:02 INC 14517765 ETFR Countess of Chester Hospital Chester Cheshire -, THE COUNTESS OF CHESTER HEALTH PARK, CHESTER, CH2 *** Male 25Y ProQA Overrid
  0090980  23:18:09 30-06-15 FLEX-A    ALPHA   3201   [Continued message - Fragment #2]den - Call Escalated GRD 340129 368274
  0067432  23:18:09 30-06-15 FLEX-A    ALPHA   3200   74:Jun 30 23:17 Conv 11 Conv 1 Starved Load stn Blocked 30-JUN-2015 23:14:55
  0067432  23:18:11 30-06-15 FLEX-A    ALPHA   3200   75:Jun 30 23:17 Water Test BOOTH 2 LOW / HI WATER PRES30100230 KU-.2N1u013 (?E4
  0118459  23:18:11 30-06-15 FLEX-A    ALPHA   3200   30 23:17]X[??Xns01.siops.net: dnPyt7xyICAL ALERT
  0114910  23:18:13 30-06-15 FLEX-A    ALPHA   3200   40:Jun 30 23:17 PLS CALL LEAH ON EXT 31505
  0119227  23:18:16 30-06-15 FLEX-A    ALPHA   3200   42:Jun 30 23:17 PLS CALL DUTY NURSE 020 7561 ****
  0120151  23:18:27 30-06-15 FLEX-A    ALPHA   3200   PLS COME TO CAVENDISH UNIT
  0118459  23:18:46 30-06-15 FLEX-A    ALPHA   3200   20150633 27z1b"bocm$n:th4Cp
  1743989  23:18:46 30-06-15 FLEX-A    ALPHA   3201   [Continued message - Fragment #2]
                                                          WN i$*CHER 01226 872 199 REajlFE AT POST OFFICE WONPi OCK AND IS WIDE OPEN*?f
  1756806  23:18:48 30-06-15 FLEX-A    ALPHA   3200   PLS CALL ***** ***** - ADDENBROOKES ON 01223 257 ***
  1734139  23:18:54 30-06-15 FLEX-A    ALPHA   3200   66:Jun 30 23:17 Term B  Page-fail test
  0000002  23:18:56 30-06-15 FLEX-A    ALPHA   3200   THIS IS A TEST PERIODIC PAGE SEQUENTIAL NUMBER  0075
  1734136  23:19:16 30-06-15 FLEX-A    ALPHA   3200   22:Jun 30 23:18 Term A  Page-fail test
  0067432  23:19:22 30-06-15 FLEX-A    ALPHA   3200   76:Jun 30 23:18 Conv 11 Conv 1 Starved Load stn Blocked 30-JUN-2015 23:16:09
  0067432  23:19:24 30-06-15 FLEX-A    ALPHA   3200   77:Jun 30 23:18 Conv 11 Conv 1 Starved Load stn Blocked 30-JUN-2015 23:16:09
  0076517  23:19:26 30-06-15 FLEX-A    ALPHA   3200   38:Jun 30 23:18 Conv 21 Check Zone Start Pulse Count 30-JUN-2015 23:19:15
  0114375  23:19:26 30-06-15 FLEX-A    ALPHA   3200   30:Jun 30 23:18 Conv 21 Check Zone Start Pulse Count 30-JUN-2015 23:19:15
  0076956  23:19:27 30-06-15 FLEX-A    ALPHA   3200   97:Jun 30 23:18 Conv 21 Check Zone Start Pulse Count 30-JUN-2015 23:19:15
  1734139  23:20:01 30-06-15 FLEX-A    ALPHA   3200   67:Jun 30 23:19 Term B  Page-fail test
  0000002  23:20:03 30-06-15 FLEX-A    ALPHA   3200   THIS IS A TEST PERIODIC PAGE SEQUENTIAL NUMBER  0076
  0074162  23:20:09 30-06-15 FLEX-A    ALPHA   3200   36:Jun 30 23:19 Trim Line 2 L359 Error Check 01 Override 010312 30-JUN-2015 23:18:09
  0114910  23:20:13 30-06-15 FLEX-A    ALPHA   3200   41:Jun 30 23:19 PLS CALL **** ****** ON EXT 34335
  1734136  23:20:31 30-06-15 FLEX-A    ALPHA   3200   23:Jun 30 23:19 Term A  Page-fail test
  0102150  23:20:33 30-06-15 FLEX-A    StNUM   3200   0778
  0000002  23:20:56 30-06-15 FLEX-A    ALPHA   3200   THIS IS A TEST PERIODIC PAGE SEQUENTIAL NUMBER  0077
  1734139  23:21:09 30-06-15 FLEX-A    ALPHA   3200   68:Jun 30 23:20 Term B  Page-fail test
  0076517  23:21:14 30-06-15 FLEX-A    ALPHA   3200   39:Jun 30 23:20 Conv 21 Check Zone Start Pulse Count 30-JUN-2015 23:21:02
  0119626  23:21:18 30-06-15 FLEX-A    ALPHA   3200   34:Jun 30 23:20 Conv 21 Check Zone Start Pulse Count 30-JUN-2015 23:21:02
  0102150  23:21:18 30-06-15 FLEX-A    StNUM   3200   0775899******
  0076956  23:21:20 30-06-15 FLEX-A    ALPHA   3200   98:Jun 30 23:20 Conv 21 Check Zone Start Pulse Count 30-JUN-2015 23:21:02
  0200905  23:22:34 30-06-15 POCSAG-3  ALPHA   1200   23:22-98 30/06/2015 23:20:18 INC 14517787 31C02 ************, ELLESMERE PORT, CH65 *** Male 64 Years M PASSING OUT GRD
                                                      340506 375692
  0334410  23:23:50 30-06-15 POCSAG-3  ALPHA    512   23:22-41 C2 Incident Allocated, Locn: *****, GREENACRES CARE CENTRE, TEARN ROAD, PL35JF, , AZ:, CAD:300615005110, ChComp:
  1508907  23:23:51 30-06-15 POCSAG-4  ALPHA    512   CH3A 512
  0273040  23:24:04 30-06-15 POCSAG-4  ALPHA   1200   30/06/2015 CH3A
  0269168  23:24:20 30-06-15 POCSAG-3  ALPHA   1200   23:24-10 30/06/2015 23:22:15 INC 14517792 10D02 ***********, NEWBOLD ROCHDALE ROCHDALE, OL16 *** Female 24 Years
                                                      MIGRAINE - FEELS SICK GRD 390789 412576


Do any flights go over the South Pole? Are there any flights that go over the South Pole, or any that have? I'm not interested in flights over the edges of Antarctica, I'm asking about crossing right over the Pole.

Are there any problems with the planes compass flying over the South Pole?

Please forgive me for asking if you are a "flat earth truther".  We sometimes get those numpties passing by trying to justify their theories (especially the one about Antarctica being a ringed ice wall with the military guarding it to make sure no-one learns the secret).

There have been many flights over the geographic South Pole, the first documented one being in 1935 by Lincoln Ellsworth and Herbert Hollick-Kenyon.  See also the first flight over Antarctica.

Pan Am flight 50, using a Boeing 747SP, also flew over both poles.

No scheduled commercial flights over fly the South Pole since there are no great circle routes in use which do so.

Flights from New Zealand to South Africa would fly over Antarctica but no airline currently flies that route.

As to problems with the compass, modern aircraft have no problems since the primary navigation source is GPS.  If you were using a compass only, as you got close to the magnetic South pole (remember, this is not even in Antarctica), the compass would become increasingly unreliable.  Simply maintain a straight course though, over the pole, and the compass will become increasingly reliable.  However, navigating over the magnetic poles using only a compass is the preserve of explorers and the fool-hardy.

This document contains more technical detail regarding navigation.  It talks mainly about the North magnetic pole but is applicable to both.

A couple of other considerations when asking about commercial flights is the need for ETOPS certification and the need to carry special survival equipment when flying south of latitude 72 degrees which is very considerable and would require the removal of revenue seats to carry it.

There is a big difference between the nearest suitable diversion airport flying over the Arctic and flying over the Antarctic.


Can I log simulated instrument time in a simulator as a CFII? I started working as a flight instructor and have a couple of questions about logging sim time as a CFII:

If I fly a sim session with my student can I log the sim time as dual-given time?
If the sim session was conducted in simulated IMC, can I also log that for myself as simulated instrument time? Or does it only count for the student?

A Level C or D Full Flight Simulator (FFS) can be used for all training required for an initial type rating, a 61.58 check, an IPC, landings required to maintain landing and instrument currency. In fact, so long as it is not (in most cases) your first type rating, you can fly a Level C or D sim, get certified and then walk out to the airplane, load it up with PAX and go flying, legally while having ZERO actual flight time in the actual aircraft.

So I would say yes you can log Dual given in a flight simulator, but you cannot log that time as flight time.


Do landing gear doors need repairs after a gear gravity deploy landing? I know that landing gears can be deployed even without hydraulic power by letting them go down by gravity, as seen on this video:

I was wondering: do the landing doors need replacement after the landing? It looks like the get damaged a lot, especially on hard touch downs.

No, they do not get damaged.

The Main Landing Gear (MLG) or Gear Bay doors can and are regularly opened on ground for maintenance purposes. Even with fully compressed oleos the MLG doors are still off the runway surface. Have a look at this Air Canada A320. You can clearly see the doors being well above the bottom of the MLG.

If you came to your conclusion by watching the white puff of smoke coming from the area of the open MLG doors - that's actually the burning rubber from the nose gear touching down.


What is the difference between the various automated airport weather observing systems? Automated airport weather observations can be produced by several types of equipment: AWOS-A, AWOS-1, AWOS-2, AWOS-3, and ASOS are the ones I've seen mentioned. What are the differences between these reporting systems? Are the older systems still prevalent, or have they been mostly converted to the new systems?

ASOS is basically a replacement for AWOS with more reporting parameters, and the first units were installed in 1991.  According to the Automated airport weather station Wikipedia page, each different type has the following parameters:

AWOS

  AWOS A: barometric pressure and altimeter setting (in inches of    Mercury).
  AWOS I: wind speed and wind gusts (in knots), wind    direction (from which the wind is blowing) and variable wind    direction (in
  degrees of the compass), temperature and dew point (in    degrees
  Celsius), altimeter setting and density altitude.
  AWOS II:    all AWOS I parameters, plus visibility and variable visibility (in    miles).
  AWOS III: all AWOS II parameters, plus sky condition (in    oktas), cloud ceiling height (in feet), and liquid precipitation
  accumulation (in inches).
  AWOS III P: all AWOS III parameters, plus    precipitation type (rain, snow and sometimes drizzle) identification.
  AWOS III T: all AWOS III parameters, plus thunderstorm detection (via    a cloud-to-ground lightning detector).
  AWOS III P/T: all AWOS III    parameters, plus precipitation type identification and thunderstorm    detection.
  AWOS IV Z: all AWOS III P/T parameters, plus freezing rain    detection via a freezing rain sensor (Note: this configuration used
  to be called AWOS III PTZ).
  AWOS IV R: all AWOS III P/T parameters,    plus runway surface condition.
  AWOS IV Z/R: all AWOS III P/T    parameters, plus freezing rain detection and runway surface    condition.

ASOS

  They generally report all the parameters of the AWOS-III, while also
  having the additional capabilities of reporting temperature and dew
  point in degrees Fahrenheit, present weather, icing, lightning, sea
  level pressure and precipitation accumulation.


How far can A&P mechanics operate aircraft under US regulations? Anytime an A&P mechanic wants to test the updates/fixes made to an aircraft's systems or any part for that matter, what are the laws (at least under the FAA) that legally allow them to operate an aircraft?

I've personally seen GA airplanes being taxied (in non-movement areas so far) by A&P mechanics. Is there a law that states that they can/cannot operate that very aircraft on a taxiway (movement area)?

What about larger aircraft (business jets, airliners etc.)? Do authorized mechanics always need a licensed (and appropriately certified with the required ratings) pilot all the time when testing the aircraft after repairs?

Finally, what about military jets? I once acquainted with someone who worked on military jets' electrical systems, but was never licensed to fly. Would he solely rely on the PIC's conclusion about the condition of the jet?

The laws for an A&P are the same as they are for a pilot. To fly the aircraft you must cary the appropriate licenses and ratings required for the airframe. No special cases are made for mechanics even for return to service flights.

However mechanics often fire up the engines and may run them up outside of the hangar to test things. As far as I know no certified pilot is required to start up and run aircraft engines.

The part about taxiing is partially addressed here. I know that mechanics can get some kind of approval to taxi aircraft if they do not hold any licenses, when I flew out of KPNE I knew some of the mechanics on the field and they needed to get some training on radio operations (as it was a towered field) before being allowed to taxi aircraft.

The last limiting factor, that may be a bit more ambiguous is the insurance regulations. For example say you were to own a little C172, your insurance may stipulate that only you (and perhaps an instructor) was allowed to fly the aircraft. In this case it would be unwise for your mechanic even if properly rated to fly the airplane as your insurance policy does not cover that.


Where does the water salute come from? Water salutes by the fire crew are regulary done for certain events like plane retiring, or an new airplane delivered and much more. But where does it come from? And why should the fire service do a water salute even if they don't really care about a pilot retiring?

Water salutes are purely ceremonial and have no practical value. There are no confirmed reports on when it started in aviation, but it became common in the 1990's.

Before aviation, this practice started for ships on their inaugural voyages or returning from a long voyage. At New York harbor, jets of water were sprayed from fire boats.

Commonly, water salutes are done for:

first flight of an airplane
first or last revenue flight of an airplane
last flight of a retiring pilot
carrying a fallen soldier

Mostly, it attracts attention and looks cool without costing a huge amount or having anything to clean up.


Is MIL-PRF-5606 H flammable at 350 deg C? Is MIL-PRF-5606 H flammable at 350 deg C?
Is it a flammable or combustible hyd oil?

Both Skydrol and 5606 will burn, though the original 5606 had a much lower flashpoint. However, there are modern derivatives of 5606 such as MIL-PRF-87257 that are within 10-15C of Skydrol's flashpoint and don't suffer the major drawbacks of Skydrol. The US military has switched to MIL-H-83282 which has a flash point, fire point, and spontaneous ignition temperature more than 200°F above 5606.

There are at least 5 flavors of Skydrol (and several for 5606) so it is a bit confusing to generalize "Skydrol" but Skydrol 500B has a flash point of 177 °C (350°F) compared to 5606 at 104°C(219°F). MIL-PRF-87257 very nearly matches Skydrol with a flashpoint of 170°C(350°F).

The two main drawbacks to Skydrol is it is extremely corrosive and much more harmful to human contact. 5606 and it's derivative MIL-PRF-87257 smell nicer and are less likely to attack rubber and plastic. One major disadvantage of 5606 is over time moisture will form condensate that oxidize aluminum tubing. This is one reason aircraft owners are told to regularly fly their aircraft; this prevents long term moisture bubbles eroding a spot in the aluminum line.

source - The US military considers the 5606 derivative MIL-PRF-87257 to more closely meet it's needs than Skydrol.


Why evacuate wing at the front side after water landing? When looking at the following Transavia B737 safety cards, I noticed that after a water landing, passengers who evacuate via the overwing exits should leave the wing at the front, while during evacuations on land they should leave via the rear side of the wing.

It is clear for me why normal evacuations need to go via the rear side of the wing, but why does a water evacuation need to happen via the front side?

Does it have to do with the center of gravity position, in an attempt to keep it is far forward as possible so that the tail doesn't sink? Because in the second picture the rear exits are prohibited from use too.

(images cut pictures at this source)

When I worked as a flight attendant back in the 80's we were told that water landings frequently resulted in very damaged trailing edges to the wings.  Flaps and spoilers will most likely have been deployed prior to landing and the velocity of the water impacting these extended surfaces would tear them up badly, along with the hinges and fairings that support them.  To avoid serious injury to passengers from ragged sheet metal, we were to direct them off the leading edge of the wing.

This wouldn't be a problem with an evacuation on land so in that case we would direct them off the trailing edge.  The upper wing surface makes a good slide and a more natural and controlled drop to the ground.

Edit:  I forgot to mention that additionally, water landings mean passengers would be wearing life vests and life rafts would be deployed.  Jagged sheet metal would make short work of these inflated devices as well.


Why are even drone flights prohibited due to the earthquakes near Mt Keilir, Iceland? A "swarm" of over 20,000 earthquakes has rocked Iceland in the past 10 days — and it could spark a volcanic eruption links to this tweet by Almannavarnadeild ríkislögreglustjóra; The National Commissioner Of The Icelandic Police, Department of Civil Protection and Emergency Management:

Earlier today a tremor pulse was detected south of Mt Keilir, in the Reykjanes Peninsula, SW Iceland. No eruption has yet been detected but due to risks related to volcanic activity, all traffic near Keilir and Mt Fagradalsfjall is prohibited, including drone flights.

I can certainly understand large craft and especially those containing people, but why might Civil Protection and Emergency Management prohibit even drones that could be used to obtain scientific data on Mt. Keilir including changes in the mountain's appearance which might indicate an eruption was imminent?

Source

The 5th of Mar NOTAM (valid to 1st of June)...
(A0100/21 NOTAMN
Q) BIRD/QWWXX/IV/NBO/W/000/999/6558N01748W999
A) BIRD
B) 2103051657 C) 2106011657
E) DUE TO POSSIBLE VOLCANIC ERUPTION ON REYKJANES, THE ICELANDIC
TRANSPORT AUTHORITY, IN COOPERATION WITH ISAVIA ANS, HAS DECIDED ON
A PLAN TO BE FOLLOWED TO MAINTAIN SAFETY OF FLIGHT WITHIN THE AREA.
FOR FURTHER INFORMATION SEE AIC A002/2021
REF AIP ICELAND ENR 5.2
F) SFC G) UNL)

... references AIC A002/2021. Which notes:

Pilots are urged to use extreme caution due to possible heavy traffic and risk of mid-air collision.
Expect drone flights below 120 meters. [emphasis mine]

That does not agree with the tweet, though permission is required to fly:

Contact Keflavík Tower for permission to enter or pass through the area.

Also, AIP GEN 3.5 (GEN 3.5.3.9) notes:

During volcanic eruption, a mobile radiosonde station can be deployed near the active volcano. Also it can be deployed for research and training purposes. Weather balloons with radiosonde will be launched by IMO scientists. Prior to launch, authorization must be given by Reykjavik ACC. When the launching site is near an aerodrome, further authorization must be given by the respective AFIS/ATC services. Information on mobile radiosonde launches shall be published in NOTAM.


What kind of jet fighter is this? I visisited Tirana, Albania the first week in August. Outside a shopping mall called "TEG" there was an old jet fighter on display. I can't recognise what make and model this is. Can anybody here help me?

PS: I'm sorry about the poor qualities of the pictures, but there was hard to find an angle with free sight and it was far darker than it appears on the pictures.

It's a Chengdu F-7. Albania only had Mig 15 and 19. Look at the shape of the vertical stabilizer, pitot and body behind the canopy.

source


Which aircraft endure the highest Max Q's (aerodynamic pressure)? What are the highest aerodynamic pressures encountered in any aircraft? And does this limit the maximum speed of any aircraft at certain altitudes? Broadly, 'how fast can you go [at a given altitude]?'

Where dynamic pressure $q$ is: $$q = \frac{1}{2} \rho v^2$$

$\rho$ is local air density, and $v$ is true airspeed.

I'm mostly concerned with high performance fighters/bombers. Here's some data I've culled (Mk-12A and 787 added for reference):

#   | Airframe      | Mach       | Speed     | Altitude    | q (kgf/m^2)
----|---------------|------------|-----------|-------------|------------
1.  | Mk-12A        | Mach  6.15 | 2,100 m/s |       0 ft  | 273,000
2.  | Mk-12A        | Mach 22.6  | 6,900 m/s | 100,000 ft  |  39,300
3.  | X-51A         | Mach  5.1  | 1,500 m/s |  64,000 ft  |  11,100
4.  | HTV-2         | Mach 20.   | 5,812 m/s | 125,000 ft? |  10,700
5.  | F-111         | Mach  1.2  |   410 m/s |       0 ft  |  10,400
6.  | B-1A          | Mach  1.2  |   410 m/s |       0 ft  |  10,400
7.  | B-1B          | Mach  0.9  |   310 m/s |       0 ft  |   6,100
8.  | X-43A         | Mach  9.6  | 3,000 m/s | 109,000 ft  |   4,800
9.  | Skylon        | Mach  5.5  | 1,630 m/s |  85,300 ft  |   4,600
10. | SR-72         | Mach  6    | 1,800 m/s |  90,000 ft? |   4,400
11. | Space Shuttle | Mach  1.3? |   400 m/s |  35,000 ft  |   3,200?
12. | XB-70         | Mach  3.0  |   880 m/s |  73,000 ft  |   2,500
13. | SR-71         | Mach  3.2  |   930 m/s |  78,740 ft  |   2,300
14. | Concorde      | Mach  2.0  |   600 m/s |  60,000 ft  |   2,100
15. | Boeing 787    | Mach   .85 |   250 m/s |  35,000 ft  |   1,200

Airframes #3, #4, and #5/6 are quite different from each other, so I'm surprised they share roughly the same max $Q$. Is 11,000 kgf/m^2 a common limit?

Note: All figures are for level flight except for the Mk-12A (reentry), Space Shuttle (ascent), and HTV-2 (glide).

[Mk-12A]: Current reentry vehicle for the Minuteman III ICBM, houses the W78 warhead (350 kT). Figures are for reentry.
[HTV-2]: Rocket glider.
[B-1B]: "[top speed] is limited by the need to avoid damage to its structure and air intakes," according to Wikipedia. The B-1B used less structural Titanium and a simpler fixed geometry inlet when the speed requirement was lowered from the B-1A.
[Skylon]: Obviously doesn't exist yet. Reaction Engines' "user manual" for the Skylon discusses the flight profile.
[SR-72]: Obviously doesn't exist yet. Lockheed Martin discussed Mach 6 cruise. 90,000 ft cruising altitude is just my placeholder value.
[Space Shuttle]: Figures for ascent.

Some background and purpose: For fun, I'm trying to design a hypersonic long-range heavy bomber. I was curious what would limit the maximum low/mid-altitude speed: drag (available engine thrust), max $Q$ (structural strength), or skin temperature (thermal protection system)... but I'll get to that in another question.

I've read through nearly all the aerodynamic, military, aircraft design, aircraft performance, and jet engine tags, looking for answers. (Really, this is a marvelous community.) Finally realized I could ask my own question.

I've tried to follow the etiquette as best as I can, but I'm pretty new to Stack Exchange, so let me know if I should change anything :) Thanks!

First, your example list doesn't distinguish between stationary and instationary trajectories. A reentry vehicle will see the highest dynamic pressure only momentarily at the end of its trip, and aerodynamic heating can be tolerated either by ablative cooling or a decently sized heat sink. All it has to sustain is the dynamic pressure at the tip.

The first samples on your list which need to continuously sustain the given dynamic pressure are the low-altitude attack aircraft B-1B and F-111. Here the dynamic pressure is given by wing loading, aerodynamics and raw thrust to keep the aircraft moving at its maximum speed. Aerodynamic heating comes on top at high altitude, because the stagnation point heat is independent of air density.

Reasons to limit the maximum dynamic pressure are:

gust loads at low altitude. Hitting the same updraft at higher speed will proportionally increase the load factor.
Aeroelastic deformation: Higher dynamic pressure means also higher torsional and bending loads, and the deformed structure might become unstable when the deformation increases the loads which lead to this deformation. Flying at higher dynamic pressure requires a stiffer and heavier structure.

If you look at the flight envelope of the SR-71 (below), it should be obvious that at each altitude only a narrow band of speed was available due to the high wing loading (= high minimum dynamic pressure) and the maximum dynamic pressure (at low altitude) rsp. the aerodynamic heating (at high altitude).

SR-71 flight envelope (picture source)


Can you jump out of a crashing plane just before impact to improve your chance of surviving? Let's say a plane is going to crash and all people on board know this.

Why can't they jump from the aircraft when the plane is near the ground?
They would have higher chances of surviving, right?

Why can't they jump from it when the plane almost reaches the ground?
  They would have higher chances of surviving, right?

Wrong.

Remember your body still has roughly the same momentum it did when it was in the vehicle - just because you jumped out doesn't mean you're not still moving forward at a rate of speed the human body simply isn't designed for.

Let's reframe your question:

  If you were in a car doing 60 miles per hour and you knew the car was about to crash into a brick wall, would you jump from the vehicle, or would you remain strapped into your seat where the car, seat, seatbelt, and airbag will all help absorb the impact?

As with a car, being inside an aircraft and properly restrained will afford you substantial protection from the initial impact, and some of the crash energy will be absorbed damaging the aircraft. That increases the length of time it takes to decelerate your body and gives you a better chance of survival.

If you jumped out of your friend's Cessna because it's going down and might hit some trees your unrestrained body would be decelerated far more abruptly when you hit the trees (or the ground).
You might survive, but you've lessened your chances considerably (and the Cessna is a best-case scenario - your forward speed would be around 60mph as in the car example. For something like a 747 you'd be in the 150 mile-per-hour range or faster when you jumped out, which is almost certainly not survivable).


Are there any airliner crashes that can be definitively attributed to Mach tuck? Mach tuck (the tendency of aircraft to develop an increasingly nose-down pitching moment at speeds above its critical mach number) caused a number of crashes of high-speed fighter aircraft before the phenomenon was well-understood, but I haven't been able to find any information regarding whether early jetliners (or modern ones, for that matter) were involved in any crashes that could be definitively attributed to mach tuck.

Were there any?

I've never heard of one, but note that the pitch down effect of Mach tuck starts  below Mcrit, and below Mmo for that matter, and airliner trim systems have a "Mach Trim" function to drive the stab to counteract it.

Fortunately, in the speed range of a commercial airliner, the amount of tuck is modest and it's not really a controlability issue, just an increase in trim speed.  Flying manually without Mach Trim, it would just require a manual trim input to keep the nose from dropping.  If the autopilot was on, it would take care of the trim change on its own.

So I would say that an airliner would never encounter a mach tuck condition that could cause loss of control unless it was way above Mmo in the first place, which means it was already out of control for some other reason.


What is the 'Downstream Clearance?' Downstream clearance  means a clearance issued to an aircraft by an air traffic control unit that is not the current controlling authority of that aircraft; but I don't get it so well. Thanks in advance..

The definition you quote is pretty clear to me. But let me try to explain some of the background to help you understand it.

An ATC clearance always contains a clearance limit, which is the point to which the flight is cleared. Before reaching the clearance limit, the flight must obtain a clearance for the next portion of the flight. If that is not possible, the flight must not pass the clearance limit.

In most circumstances, a flight will receive its ATC clearance on ground before departure, and the clearance limit will be the destination aerodrome. The flight is then allowed to depart and continue all the way to its destination. This can be done because there is reasonable assurance that ATC will be able to coordinate the flight all the way through to the destination as the flight progresses.

In some cases, a clearance for (a portion of) a flight cannot be issued very far in advance. One example is clearance to cross larger portions of ocean (oceanic clearances), which are typically based on procedural separation and require the crew to provide very exact time estimates, which is impossible to do before the flight is airborne. Something similar is likely to be the case for certain military flights where some sort of diplomatic clearance is required to enter a countries airspace. Or maybe a flight has to cross the border between two countries that do not cooperate (a bit hypothetical in this day and age, but it might exist somewhere).

The definition of a downstream clearance is quoted in the answer. It means that, while a flight is flying in airspace A heading toward airspace B, the crew must obtain a clearance from the ATC unit in charge of airspace B before entering. This is because the flight will not be coordinated between ATC A and ATC B like most flights. How exactly this is done probably varies from place to place. The crew might contact ATC B on a secondary radio or CPDLC, or maybe ATC A can forward the request and relay the clearance from ATC B. In any case, the crew is responsible for not passing the valid clearance limit before a clearance to continue has been received.


Do pilots adjust the aircraft's flight path to allow for the curvature of the Earth? If an airliner is flying at approximately 500-600mph, it seems to me that there would need to be a significant adjustment for altitude so as to not fly off into space.

Wikipedia says that there's an 8 inch drop for every mile because of the Earth's curvature. But, I've never heard of any airliner adjusting for the curvature. Also, shouldn't aircraft have to adjust somehow for the Earth's rotation because it varies depending on the latitude?

Aircraft altitude is measured (inferred) by atmospheric pressure. The aircraft is usually flown at an altitude that maintains constant ambient pressure (by pilot or autopilot, as the case may be). Changes in local barometric pressure (provided by air traffic control) are used to recalibrate the aircraft altimeter.  As long as the aircraft is flown at a constant ambient pressure (hence constant altitude), it will be following the earth's curvature (as the atmosphere is attached to the spherical earth and has same properties at same distance from the center, in an ideal case) as the altitude is measured from the surface, which is curved, and not a plane.


Why aren't thin, delta-shaped wings used for fighter aircraft? In the past, we used thin, delta-shaped wings (ogival wings) such as those on the Concorde.

These wings can be used up to mach 2.2. Due to high fuel consumption, these wings are no longer used commercially.  However, why can't they be used on fighter aircraft?

Yes, it is. It was used on may 2nd generation designs already mentioned by habu, and it is returning now in the 4.5th generation, now with canards:

Eurofighter Typhoon:

JAS-39 Gripen:

Dassault Rafale:

And occasionally without too:

HAL Tejas:

And most of the other designs, while having horizontal tail surfaces, are not really far from that layout either:

Mig-29 (Su-27 looks very similar and all the newer Russian fighters are derived from either of those two):

F-18 Hornet:

The F-22 and F-35 with their negative sweep trailing edge are more of an exception, their layout being governed more by requirement for lower radar cross-section than aerodynamics.


Is the taxi route omitted in low visibility (LVP)? This video shows an auto land into Schiphol during bad weather / LVP (Low Visibility Procedures).

After reporting vacated, the ATC instruction is quite short (around 2:45). Simply the gate number. (I'm not sure if part of the conversation is omitted during editing, but nothing seems to suggest that.) This is my transcription of it:

  Pilot: Ground, hello, 4A, vacated S3

  ATC: 4A, stand D5

  Pilot: Stand D5, 4A

As you can see (read, hear), no route is given. I checked the Dutch eAIP but found nothing. The only thing I found is from a Jeppesen chart (dated 2005):

The highlight above hints at, but not explicitly, that taxi routing is not necessarily given – or so I understand it.

If more specificity than EASA is needed, then EHAM would do.

Initially I thought it's a follow-the-greens, but then at the intersection shown below both directions were illuminated:

It has nothing to do with LVP, but with the fact that there are standard routes at Schiphol to the main piers;

From the AIP AD 2.1 (EHAM) section 2.1:

  Aircraft shall comply with the standard taxi routings to and from the stands as depicted on AD 2.EHAM-GMC. Deviations from the standard taxi routings will be given timely to the pilot by Schiphol Ground.

The AD 2.EHAM-GMC (Ground Movement Chart) shows the following in the legend:

Late at night, when there is almost no traffic, there is no need to hold aircraft or deviate from the standard route.

The crew is Dutch, they are at their home based, so they are well aware of the routing. So ATC only gives their stand, knowing they will find their way.

There's a double taxiway almost fully around the central terminal area. The outer ring is counterclockwise, the inner ring is for clockwise traffic. The exit for RWY 06 leads straight onto the counter clockwise taxiway. From there you can follow that until A10, which leads you to the D5 gate. There is basically no other way.


Sudden drop in speed and altitude? Can someone tell me exactly what happened on this flight? It was a brief moment of sudden drop in altitude (6000 feets) almost at the same time with a drop on engine powers. It's a drop of signal from flightradar trackers or an issue recorded in flight? Thank you!

https://www.flightradar24.com/data/flights/w63655#20da042d

Smooth descent at 1500 feet per minute from 30,000 to 11,000.  Nothing unusual.
Or was there a blip somewhere in the data that I scrolled past?  (Where?)

Edit: The blip at 13:16 is from 36,000 to 29,600 and back, in less than a minute.  A 12,000 fpm dive followed by a 12,000 fpm climb (and vicious G force at the pull-up) is probably impossible for an A320-232.


Does the FAA or FSS check or authorise IFR flight plans? There is an existing question about VFR flight plans the answers to which suggest that FSS dont check these and the main purpose of filing GA VFR flight plans is to aid subsequent S&R efforts.

You could therefore file a flight plan where some aspect is beyond the aircraft's capabilities (payload, range, altitude, GNSS, other equipment, etc).

How about IFR flight plans for chartered commercial flights for example.

The International Flight Plan form has a box labelled "ACCEPTED BY" but I assume this just indicates that the plan has been received and filed successfully, not that it has been checked for completeness, feasibility or safety or that it has passed some authorisation process.

For IFR flight plans, is there any FAA-mandated checking or authorisation performed by FSS or other quasi-official body at time of filing other than simplistic checking that something has been entered in mandatory fields?

The FAA's flight plan filing FAQ says that it's about formatting:

  Q: Will an FPL be automatically rejected or is that a manual function?

  A: ERAS automatically rejects an improperly formatted FPL. The Rejection (REJ) message usually includes information which identifies
  the error. The filer should correct the error and reenter the FPL.

That seems to be confirmed in this FAA ICAO Flight Planning Interface Reference Guide that goes into detail on computerized flight plan formats, filing etc. Section 3.7.2 lists all the possible reasons for the ERAS computer to return a REJ (rejected) message, and they're all to do with formatting or invalid values, e.g. airspeed can't be zero.

To me, that makes sense: no one knows the equipment or capabilities of an aircraft except the person (or organization) submitting the flight plan. Even if the FAA had a database of every aircraft in the world, what happens if your GPS unit burns out and you want to file IFR using only standard IFR equipment (VOR, ILS)? Or you want to fly at a reduced (or increased) cruise speed for some mechanical or performance testing reason? The FAA couldn't possibly know if your submitted values are correct.

I don't know (and couldn't find out) if there's any situation where ERAM can't generate a flight strip even though the flight plan is accepted as valid. If it does happen, I suppose that would be a sort of secondary check.

As an aside, I was at an EAA IMC Club meeting last week and we discussed the new ICAO flight plan format (new to the US, that is!). A couple of controllers were there, and they said that you have to be careful about what equipment you put in your flight plan in case you get assigned something beyond the pilot's capabilities. For example, a Cirrus is PBN-capable and if you input all the equipment correctly in the flight plan then you may get a complex SID rather than just departure vectors. If you aren't familiar and comfortable with the avionics then you might get yourself in trouble, so it would be better to file only basic avionics. That kind of decision isn't something the FAA could or should validate.


I overboosted an engine in a Mooney 231 - do I need to do an inspection? I have an intercooler, but no wastegate. Manifold pressure was not controlled on takeoff and went to 50. The max is 37!  If overboosting doesn't really exist because the relief valve opens, then how did the gauge even get to 50?  It was at that level for 20-30 secs. The engine appears to run great afterwards.

Is there anything that should be inspected or done?

This most likely warrants a call to Don Maxwell the veritable Mooney expert but I would for sure have the engine checked by a Mooney expert or someone that knows their way around the TSIO-360-GB. At the minimum a compression test and possible borescope check is in order.

If you have the early 231 in its original config you have a fixed waste gate that can be over boosted on takeoff.

  The engine also had a fixed wastegate in the exhaust system, meaning
  careful pilot technique was required to keep from over boosting the
  engine on takeoff.  If the pilot inadvertently added full throttle for
  takeoff or a go-around, the engine would over boost, with only a
  mechanical pop-off valve in the induction system to save the engine
  from literally coming apart on the runway.  Fixed wastegates also mean
  high turbocharger speeds (RPM) at altitude, which reduces turbocharger
  life

I don't know much about the gauge itself but it may warrant checking it to make sure it is operating properly.

You can also reach out to continental and ask them what the over boost limit is. There is a chance they have some data on it or can let you know of a good course of action.


How is fuel dumping safe? The answers to this this question make it clear how modern airliners dump fuel in the case of an emergency. As far as I understand, fuel dumping might be done to lower an aircraft's weight to the maximum landing weight, particularly soon after takeoff.

As far as I understand, jet fuel is typically not safe. When I, as a complete outsider, hear of fuel dumping, I imagine a whole bunch of dangerous corrosive fuel being dropped on whatever happens to be below, and it sounds like a frankly awful idea.

What makes fuel dumping safe, or if it is dangerous what makes it worth it?

Fuel dumping is almost always an emergency maneuver, and it is never good for the environment.  So the alleged danger from the dumping must be balanced with the imminent danger to the 200–400 passengers involved.  It is never an easy decision but that's why the Captain gets paid the big bucks...

Dumping fuel sounds dangerous but it is not.  It is not going to explode.  Jet-A can be compared to kerosene and I don't have that statistic so let's compare it to Diesel Fuel which is not dissimilar to Jet-A.  Diesel Fuel at 400°F(204°C) is as volatile as gasoline is at 70°F(21°C).  Obviously that is a big difference.  Jet-A also evaporates into the air, so little if any hits the ground.

The biggest danger I see is to the atmosphere.