Do airline companies have a Chief Medical Officer? I was wondering if airline companies have a Chief Medical Officer who is in charge of the well-being of passengers. For example:

in timing the lights on/off moments on intercontinental flights;
timing and type of food served, to support periods of sleep, wake and disembarcation;
airconditioner procedures, to ensure passenges don't get sick from too cold airconditioners (for example when the captain released power from the engines to the airconditioners after take-off, while the cabin crew had set it to min-min on an insufficient EPU at a hot airfield, it happily started blowing 10 degrees C in my neck);
methods and moments of desinfecting the air/passengers when contagious diseases break-out (or a flu epidemic in the US, with all its internal air-traffel);

I'm not sure if every airline is the same. However each major airline I am familiar with does have a medical unit, usually headed by a doctor.

However, most of their efforts are actually dedicated internally - by that I mean looking after their employees. Things like:

Assessing the employees ability to return to work after an injury or illness
Fatigue management policy
Assessing whether a certain condition is acceptable to work with
Overseeing drug and alcohol rehabilitation (in some cases in Australia at least the employee is not automatically fired for being drunk/on drugs, they are allowed to complete a program and continue work)
Occupational health and safety assessments
General 'doctoring' duties for aircrew

Of course they are also involved in passenger health policy development, but as I said - the majority of their work is dealing with their own staff (at least, this is from my viewpoint, but I may not be seeing the whole picture).

In terms of an outbreak like you have mentioned, there is always an action plan ready to be put in place which is developed with the government health department (or CDC in USA).


What requirements are needed to fly an approach that requires you to fly over the US/Mexico border? I was flying North of El Paso Texas listening to El Paso Approach when I heard Approach ask a Falcon Jet if they could fly into Mexico to fly a Runway 4 GPS approach.  At El Paso, the runway 4 approaches require you to fly across the US/Mexico border into Mexico.  What requirements are needed to fly an instrument approach that requires you to fly over Mexico?  Would you require a radio telephone permit to use the radio even though you are talking to an FAA controller?

I had flown my plane (small 4-seater) from Houston to California a few years ago and on the way back, I stopped in El Paso to refuel and sleep for the night.  While in contact with the tower, following whatever vectors they were giving me, I noticed that I was about to cross into Mexico.  It's pretty obvious from the style of buildings and how close they are together that one area is Mexico and the other area is the US, especially at 1000 ft (or less) AGL.  I asked the controller if this was correct since it would put me across the border into Mexico.  I seem to remember him saying something about they had an agreement with Mexico that allowed them to use / control that airspace.


How do you find information about overnight parking at any airport that is not your home airport? As a private pilot, how do you find information and plan an overnight stay at an airport other than your home airport? For example, where to park, how to get out of the airport?

Generally, you call the FBO(s) at the airport. They are often listed in the A/FD or if you want a digital source, airnav has them. If you use Fore Flight, they will also list many of them. They will also provide you with fuel information as well as anything else you may need to know about the airport.

At smaller airports, you may be limited to a single FBO. At larger airports it's usually worth to talk to all of them (depending on your needs) since there can often be large differences in prices. It should be noted that some FBO's may waive ramp fees if you purchase some minimum quantity of fuel. Some airports may also charge landing fees (which you will pay through the FBO). When I flew out of KPNE there was a $5 a day landing fee (as many TO/LD as you wanted).

Pro Tip: the internet is riddled with forums and user groups these days. You may find that a simple "Hey thinking of flying into XXX next weekend" will return you a gaggle of information about the airport and what to do. If you are really lucky, someone may even offer you a spot in their hangar (if they have room).


Identify Aircraft in Petra Album Art Was listening to one of Petra's old songs, when I noted the aircraft in the cover image. I tried searching on the net, but couldn't find anything.
It appears to be a pusher aircraft, with a four blade propeller.. that's all I could gather from the image. There are markings "ANG" (?) but I do not know how helpful that is.
This is from Petra's album titled "Beyond Belief".

It is a C-130 Hercules.  Of the four engines , the only feature prominently visible is the outboard left propeller.
I'm not sure why you thought it might have a "pusher" configuration-- the nose is to the left (off the edge of the photo), and vertical tail (with the "ANG" logo) is showing near the center of the photo.
Other prominent features are the flap attached to the trailing-edge of the (left) wing, and the (lit-up) back end of the fuel tank attached below the left wing between the two engines on that wing.


Who makes the call to start in terrible weather conditions? I once headed to the airport during a huge thunderstorm with winds above 55 knots and massive rain and some small hail. At the airport, I saw that most flights were delayed or even canceled. To my surprise, my flight was still planned to depart on time. At the counter, I got the information that it was up to the pilots to make the decision if they want to delay or if they what to depart during the storm.

My flight was only a short hop of about 50 minutes and given the direction of the storm it was pretty clear that the storm would reach the destination at the time of the scheduled arrival. And this is exactly what happened. It was the most turbulent, terrifying and scary flight I ever had.

In the last two days, there was another windstorm in Europe with winds above 60kts. The news reported that some airports were closed but there are also videos on Youtube about planes landing during that storm.

My question is: Is it really only up to the pilot to make this decision? Who else might make that call? The airline? The airport? Are there official rules about departing in such conditions?

Who else might make that call? The airline?

Yes, if the airline thinks the weather is too bad at a particular airport for safe operations, it can just cancel all flights from that airport without asking the pilots.

  The airport?

If the airport closes completely, then it is closed. No flights can depart any more, even if the pilots consider it safe.

  Is it really only up to the pilot to make this decision?

If neither the airline cancelled the flight nor the airport has closed, it is indeed up to the pilots, or more specifically to the PIC (Pilot In Command, the Captain on an airline flight). They are ultimately responsible for the safe operation of the aircraft and have to make the decision:

  4.5.1 The pilot-in-command shall be responsible for the safety of all crew members, passengers and cargo on board when
  the doors are closed. The pilot-in-command shall also be responsible for the operation and safety of the aeroplane from the
  moment the aeroplane is ready to move for the purpose of taking off until the moment it finally comes to rest at the end of the
  flight and the engine(s) used as primary propulsion units are shut down.

(ICAO Annex 6 Part 1 - 4.5 Duties of pilot-in-command)

The SIC (Second In Command) also gets a say in this because of crew resource management, meaning if they think it is unsafe to depart, they can and should speak up.

  Are there official rules about departing in such conditions?

The respective national aviation authority may have rules on when a departure is permitted, but this will depend on the exact location. The pilots will however have received rules and training from their airline, which should indicate when a departure is allowed. The most important aspect to consider are the aircraft limitations. There is no legal crosswind limit for a takeoff, but e.g. the Boeing 737 FCOM lists a demonstrated value:

  The maximum demonstrated takeoff and landing crosswind is 33 knots.

(Boeing 737 NG FCOMv1 1.10.2 Limitations - Operating Limitations)

It would be considered unsafe to depart with a stronger crosswind.

Note that limitations for landing are typically stricter than for departure and the pilots are legally required to check the expected weather at the destination airport before departing.

In Europe, Eurocontrol can also delay a departure due to expected weather en-route or at the destination airport. See What is the difference between en-route delays and airport delays?.


What kind of helmet is in this A-10 video? Here is a screen capture from a YouTube video. The aircraft is an A-10.

What kind of helmet is that and where can I learn more about it?

Additionally, does the weight of the helmet and it's apparently awkward center of gravity cause issues during high-G maneuvers?

The pilot's helmet in the photo is a standard Gentex HGU-55/P fitted with a Thales Aerospace Scorpion Helmet Mounted Cueing System.  Information on the SHMCS is available on the corporate website

http://www.thalesvisionix.com/overview/

As to weight, the display, cableing, and visor add several ounces of extra weight to the helmet.  It's a little heavier and slightly bulkier than a standard visor on a helmet but not by much.  Aircrews have been flying with HMDs now for about ten or so years without any major impediments to their flying abilities.

There has been a weight issue associated with the F-35 HMD and the aircraft's ejection seat which could cause a fatal whiplash injury during ejection with smaller pilots.  This is being remedied with changes to the seat's pneumatic catapult system, drogue chute deployment timing, both controlled by a selector switch prior to flight, and a newer, lighter version of the helmet under development.


Do Boeing and Airbus learn from each other? Air France Flight 447 crashed into the Atlantic Ocean in June 2009. It was later revealed that the FO was unwittingly pulling the sidestick back, stalling the aircraft. The aircraft was an Airbus 330.

China Airlines Flight 006 almost crashed in February 1985 when the captain failed to step on the rudder after a sudden single engine failure at its cruising altitude and it got into a steep spiral. It recovered from the spiral descent thousands of feet above the Pacific Ocean but it experienced significant structural damages. The aircraft was a Boeing 747.

Some people say that the first accident could have been prevented if the sidesticks of the pilots had been inter-connected such that when one pilot moves his sidestick the other moves the same, just like the yoke system of Boeing aircraft. Also, some people say the second accident could have been prevented if the autopilot system had been programmed to correct excessive roll or pitch maneuvers caused by the pilot's control inputs or their absence.

But it looks like neither of the companies has adopted such suggestions, and that got me curious. Do they learn from each other? Do they correct their systems based on their competitor's accidents?

Yes Airbus and Boeing learn from each other: they compete with each other. Both are implementing successful features of the competitor, and when the A320 came to market it required differentiating features to gain market share. The competing design from Boeing, the 737Classic, was completely re-designed in the 90s because of the lower specific fuel consumption of the A320. The other Boeing product competing in this class, the B757, is out of production. The resulting 737NG has outstanding fuel economy as well, partly achieved by the blended winglet which Boeing pioneered for this class of aircraft.

Where the two companies differ is in the design philosophy for interaction of the pilot with the aircraft. The A320 is actually the oldest design of Airbus that is still produced - the type was certified in 1988, while the 737 and the 747 type certificates were issued two decades earlier. The 737 MAX still has a common type rating with the original B737-100 and this poses a limit on the introduction of new flight crew ergonomics. The A320 could completely re-design all known features in cockpit control and implement new ones from military aircraft, such as the side stick which made the F-16 such a successful air superiority fighter.

The OP focuses on accidents and incidents which happened with the planes, due to incorrect pilot action. This is a subject where everybody learns from everybody, to continue to make air travel safer:

Every accident is thoroughly analysed in order to find the cause and prevent it from happening again in the future. This is done by independent government organisation who only focus on the cause of the accident, nothing else. The NTSB in the USA, the BEA in France.
As a result of this, there may be improvements imposed by the overseeing regulatory aviation organisations: FAA in the USA, EASA in Europe. They may write directives for aircraft manufacturers to implement changes in the design of the aircraft if that is where the incident cause was, or in the training procedures of pilots if pilot error was found to be a factor.

The ultimate proof of the pudding is in safety, and both Boeing and Airbus have excellent and very similar safety records for their aeroplanes. There are many ways that lead to Rome - everybody learns from everybody, and continues to improve their design which will always differ to an extent from the competition.


Are there general accuracy requirements for aircraft power supplies? Let's say I have some LRU device that requires some DC voltage to be powered on. Are there any general requirements in aviation/aerospace that say how accurate that supply voltage must be in order to be allowed on a plane?

Update:

To be more specific, consider an LRU that takes 28V on the input and provides it to a DC-DC converter. I would like to know how accurate that 28V being provided, needs to be.

Short answer:

Operational voltages on the 28 V bus may range from 22 V to 30 V.
Abnormal voltages on the 28 V bus may occur from 0 V to 60 V.

The detailed requirements depend on the manufacturer, the type of plane and the jurisdiction.

USA: MIL-STD-704

US military standard MIL-STD-704(F) Aircraft Electrical Power Characteristics defines electrical properties of military aircraft equipment. For instance the 28 V DC bus is specified as:

A similar standard should exist for commercial aircraft, unless they just apply MIL-STD-704 as well.

Europe: ISO 1540

In Europe there is ISO 1540:2006 Aerospace -- Characteristics of aircraft electrical systems. This standard differentiates by the actual power source:

Category A: TRU (transformer)
Category B: engine driven DC generator
Category R: regulated DC power from active converter

Category A and B are specified identically for their DC characteristics. Category B is the worst case for AC ripples. Category R is the best case, as it is already regulated. Nevertheless, connected equipment needs to cope with the worst case, that is category B (engine driven generator).

ISO 1540 specifies the 28 V DC bus characteristics (summarized) as:

28 V DC bus - Normal operation: 22 V - 30 V
28 V DC bus - abnormal/onset: 0 V - 60 V


Was the colliding object in the Guadalajara accident ever identified? In December, four months ago, a 737 landing in Guadalajara apparently hit an object and damaged its nose. At the time it was suggested that it might have been a small drone.

Has the object been positively identified?

According to Boeing, there was no foreign object involved at all, and the cause of the damage was  an implosion of the radome due to differential pressure, caused by improper installation of a seal:

From AVHerald:

  On May 31st 2019 Boeing reported that a visual inspection of the radome did not show any evidence of a hard or soft body impact, no DNA material was found. Boeing concluded: "The review showed that an interface seal was installed around the entire periphery of the radome with no openings. This configuration lacked the approximately 8 inch opening in the seal along the bottom of the radome interface specified in engineering drawings and the Airplane Maintenance Manual (AMM 53-52-00) radome installation task. This opening in the seal is required to allow the radome area to drain and for equalization of pressure changes across the radome during flight. A review by our engineering team concluded that the lack of this gap likely resulted in differential pressure across the radome during descent which may have contributed to an internal collapse of the radome."


Can the fluid from one hydraulic circuit go to another one (voluntarily or not) in flight? Given the following facts for airliners:

Fuel can be transferred in flight from one tank to another
Hydraulic energy can be transferred without fluid transfer from one circuit to another in flight using a PTU
Many hydraulic components are fed by several hydraulic circuits and thus may use fluid from several hydraulic circuits simultaneously

Can hydraulic fluid go from one circuit to another while in flight?

This depends on how the systems are plumbed, and while this is likely an exception, for some airplanes like the EMB-145, the answer is yes.

The EMB-145 has 2 hydraulic systems.  System #1 serviced the outboard brakes and system #2 serviced the inboard brakes and the parking brake.  The parking brake actuated all of the brakes and this let you transfer fluid between the systems through the outboard brakes.  This isn't a normal procedure, but one maintenance would walk you through if you had low fluid in one system and more than you needed in the other to balance the systems if you were out somewhere without the ability to service the hydraulic fluid.

The procedure was either

Depress and hold toe brakes
Set parking brake
Release toe brakes
Release parking brake

or the opposite, depending on which way you wanted to transfer fluid.

This works in flight or on the ground (don't do this in flight lest you get distracted and end up landing with the parking brake set)


Can a company be both an airplane manufacturer and an airline? It may be advantageous for a company that manufactures its own aircraft to also be an airline. For example, the airline business would likely have reduced maintenance and parts costs relative to other airlines, and there would be a tighter feedback loop between manufacturing and end consumers.

I have read that Boeing, who used to own United Aircraft and Transport (UAT), was forced to dissolve UAT after investigation into the scandalous "spoils conferences" (source):

  In a move clearly aimed at Boeing, new Postmaster General James Farley and, later, Congress banned the award of the new contracts to any companies that also built aircraft.

I managed to find what I believe is the Air Mail Act of 1934 that supposedly bans these vertically integrated companies here, but I don't see where, specifically, the act bans these companies. It's unclear to me whether this was a one-off ban of combined aircraft manufacturers and air mail companies, or whether this ban continues through today with modern airlines. I am specifically interested in the US here, but would also be curious about other countries (e.g. could Airbus do this?)

Is it still illegal for all manufacturers to start their own airlines, or does this law no longer apply today?

Another historical perspective: Junkers helped to found and participated in dozens of airlines in the early 1920s. This helped to boost demand for his products (mainly the F-13, but all started with two converted military two-seaters).

That was everything but unusual: Many aircraft factories, among them Albatros and Sablatnig in Germany, tried to shift their products after the cessation of hostilities by founding airlines.

Generally, when a city wanted to be connected to the new air travel network, it would supply an airfield and some capital and the aircraft company would be happy to contribute aircraft and personnel. This way, dozens of airlines providing mostly local connections were operating in the early Twenties in Europe and competition would drive down prices and increase demand. Therefore, all those airlines were unprofitable and successfully lobbied for government support, which grew from year to year. But also Junkers was not profitable and had to be supported by government loans.

By 1925, 40% of all civil air traffic worldwide was flown on Junkers airplanes and Junkers Luftverkehr AG completely or partially owned many of the airlines operating its aircraft. The failure of Junkers to repay government loans at the end of 1925 meant that ownership of those shares was transferred to the German government which moved swiftly to consolidate the German airlines into Luft Hansa, thus ending the price war and greatly helping to reduce the subsidies.

By resolving to only subsidize one single airline, the national flag carrier, Governments effectively ended the habit of aircraft manufacturers to operate airlines. Specific legislation was not needed.


What is the difference between ICAO Annexes and Documents? I have gone through many ICAO and aviation related sites, but I still can not understand the basic difference between annexes and docs.

What is it?

An Annex to the Chicago Convention on International Civil Aviation (which established the ICAO) is adopted by the ICAO Council according to particular voting procedures laid out in Article 90 of the Convention, and is binding upon the signatory States.

An ICAO document is just something the ICAO organization has chosen to publish in its Doc Series with an identifying number for ease of reference. Being an "ICAO Document" doesn't in itself say anything about who wrote it or its legal force. For example, Doc 7300 is the Chicago Convention itself, which has a lot of force (but not because it has a Doc number), whereas Doc 9562, Airport Economics Manual is more informative in nature and tries to be persuasive rather than authoritative.


Do small civilian aircraft have autopilots? If not, why? Doesn't it make flying safer? It seems to me that automating a small plane should be easier than automating a car (excluding dealing with Air Traffic Control). Is it too expensive?

Many small, light aircraft are equipped with an autopilot today. They can range from very simple autopilots, without altitude selector and so on,

Source, ST SYS 30, $ 12,000

to advanced systems with altitude selector, automatic trim and so on.

Source, Bendix/King KFC 225, $ 15,000 - 42,000

And with this GPS, feeding the autopilot with data, it has the abilities of an airliner.

Source, Garmin® GTN™ 750, $ 17,000

You have to know, the systems in the general aviation industry are getting better and better. Of course they are way below the complexity of the avionics of airliners, but the features are the same if not more.

For example: A captain of an airliner has to review or change the flight plan with the FMC, respectively MCDU on Airbus, a not very straight-forward device to control the plane.

Of course, the FMS has a lot more capabilities than a GA GPS, but one of it's primary features is the input of the flight plan. And in that, from the usability-view, the Garmin® GPS has the better solution: An all-in-one navigation device with touchscreen input.


What fundamental differences separate low-budget airlines from traditional airlines? Low-budget airlines have made it incredibly easy and cheap to travel far and often, and yet at first glance they seem nearly identical to traditional airlines. Sure, you have to pay for meals, but a few dollars/euros here and there shouldn't make THAT drastic a difference. So what is it that makes a budget airline a budget airline?

Generally speaking:

They operate a limited number of airframes if not a single one (for example Ryanair operates 420 737-800's and only a single 737-700 for chartering). This allows them to buy planes in bulk as well as cut down on spare parts reserves, pilot proficiency training in multiple airframes and overall maintenance costs by only needing to hire mechanics proficient in a single airframe. They can also easily substitute an aircraft on a given route as they are all configured the same.
By having seats that don't recline and sometimes no first class they can really pack people in. Those extra customers make a big difference. There has even been some buzz about packing more people in with "standing" seats but I have not seen anything certified on that front as of yet.
In my experience they tend to have less lenient refund and change policies. For example Spirit charges a $90 cancelation fee and most tickets are around that price.
The meals tend to be pre-packed and may have a longer shelf life than the hot food served on other airplanes. This means they can buy it in bulk (read cheap), in advance and store it, and there is no need to coordinate the delivery like there is with hot food. Cold food can hang out at the gate waiting for the plane.
There has been a big move to use mobile devices for a lot of classic functions like check in and boarding passes. This allows them to not need checking counter employees or curb side employees etc. This labor cost is a huge savings. In many cases the flight attendants may also be the  boarding/gate personnel.
Some of them also avoid major airports and may elect to fly out of smaller regional airports. This helps keep fees down and some satellite airports may be substantially less busy allowing them to get in and out faster.

As per @Jamiec's comments

Shorter turn around times

No seat back pockets so nothing to clear out.
No pillows and blankets to pick up
Cabin crew may do the majority of cleaning

As @757toga notes some of them also may keep pay low or act as a jumping off point for young pilots to get their type certs and build hours.

Related questions:

How can Ryanair offer flights for a penny?
What's the typical cost (and its breakdown) for a long-haul commercial flight?


Why Pitch Trim Up/Down & Roll Left/Right switches on yoke or control stick? My understanding is Pitch Trim should hold current Pitch position, Roll Trim should hold roll position and Rudder Trim should hold Rudder position to relieve pilot of holding the yoke/stick or pedal continuously.

But why there is Up-Down/Left-Right (Pitch/Roll) switches on yoke or stick?

Appreciate, explanation of trim fundamental with respect to this.

I might be mistaken, but it appears to me that you're missing an important piece on how trimming works. It's not a button you press to magically remove the control forces, but rather, you need to adjust the trim tabs (on most smaller aircraft at least, some aircraft, especially new large ones, have other mechanisms, but that's outside the 'basics' scope) to achieve the desired result.

I'll use the elevator as an example, but it applies to ailerons and rudder as well. This is a common image used when showing trim tab movement:

Basically, the trim tab extends into the airflow, pushing the elevator in the other direction. This is key though, as it's using airflow, its effectiveness diminishes when airspeed is reduced and it becomes more effective when airspeed is increased, which is exactly how the elevator itself is affected. This means that, should the airspeed change, both elevator and trim-tab will be affected the same way and the forces, and as a consequence the elevator deflection, will remain in an equilibrium. Maintaining a specific elevator deflection will cause the (aerodynamically stable) aircraft to remain at a selected angle of attack and therefore airspeed. In order to change airspeed, you need to change angle of attack, and so you need select a different elevator deflection, prompting the need to 're-trim' fairly often during a flight, especially during departure and approach. This applies to elevator trim, I've never flown with (in-flight adjustable) aileron or rudder trim, but I assume it is primarily used to counter effects of engine torque and P-factor, so it would be adjusted whenever you're changing the power setting.

You could, theoretically, skip the trimming step and hold it with arm strength, but your arms would eventually go numb and it would be virtually impossible to keep it on airspeed while accomplishing the other tasks in the cockpit during high workload periods. The March/April 2014 issue of FAA Safety Briefing talks a bit about trimming, and mentions that the Weber-Fechner law, which discusses the concept of Just-noticeable difference, states that you need about 14% of difference to the pressure you're manually holding to notice a difference, so trusting the feel of your hand pulling the yoke is not a particularly good idea. I do believe some aircraft, in particular larger ones, would require more force than humanly possible for the needed elevator deflection in certain situations, suggesting the need to use trim, but I might be mistaken on that point.

The movement of the trim tab is sometimes driven by an electric motor (or otherwise powered, hydraulics for example) in which case you have up and down buttons, and sometimes it's manual, in which case you usually have a wheel which can be rotated to pull the tabs up or down.

Up and down, which is often referred to as 'nose up' and 'nose down', signify what kind of control forces you want to remove. If you find yourself constantly pulling the nose up to maintain the desired airspeed and attitude, you'll need to apply nose up (or 'up') trim while simultaneously releasing the back pressure and vice versa. This sounds harder than it is, it just means you hold the yoke in place, and you will notice the amount of pressure needed to hold it there drops until it's completely gone. This is one of those things which is actually harder to do in a home simulator than in real life, as you'll have to move the control while applying trim. Note that the 'up' and 'down' labels do not mean the tab will move up or down, remember the tab travels in the opposite direction of the elevator, and to pull the nose up, the elevator needs to move up into the airflow, meaning the tab will actually move down, as can be seen in the picture.

As a bonus; in aircraft with no autopilot and autothrottles, if you do not apply any control forces the aircraft (aerodynamically stable) will maintain a particular airspeed. This means that for a specific configuration (flaps, landing gear, weight, power, etc) it's possible to trim the aircraft for a specific speed, this is very handy when it's crucial to maintain a specific airspeed such as during departure or approach.

This also means, which might not be obvious for someone not familiar with aircraft, that it's not possible to trim an aircraft to maintain altitude. Sure, there's usually a specific airspeed which will keep the aircraft in level flight, but that's only until you enter the next up- or downdraft, or until you've burned off a bit of fuel and aircraft has become lighter. So you will either need constant speed or power adjustments to keep it on altitude, most aircraft without autothrottles use the former.


Who was the first flight test engineer? The discipline of Flight Test Engineering has existed since at least 1903, but when did engineers identify their work, distinguish their work from other disciplines, under terms that would mark it as Flight Test Engineering?

This may take the form of someone who first used the term flight test engineer or flight test engineering.

Google demonstrates a history of the terms:

Image credit

NATO describes the history of its flight test organization this way:

  Soon after its founding in 1952, the Advisory Group for Aerospace
  Research and Development (AGARD) recognized the need for a
  comprehensive publication on flight test techniques and the associated
  instrumentation. Under the direction of the Flight Test Panel (now the
  Flight Vehicle Integration Panel) a Flight Test Manual was published
  in the years 1954 to 1956. This original Manual was prepared as four
  volumes: 1. Performance, 2. Stability and Control, 3. Instrumentation
  Catalog, and 4. Instrumentation Systems. As a result of the advances
  in the field of flight test instrumentation, the Flight Test
  Instrumentation Group was formed in 1968 to update Volumes 3 and 4 of
  the Flight Test Manual by publication of the Flight Test
  Instrumentation Series, AGARDograph 160. In its published volumes
  AGARDograph 160 has covered recent developments in flight test
  instrumentation.

The Michigan Alumnus written on Aug 13, 1938 refers to Clarence Johnson's experiences as a  Flight Test Engineer. He graduated with a MS in 1933 so presumably became an engineer at that time.


Why do solar planes have many small propellers instead of fewer large ones? Many solar planes, like NASA's Helios (pictured above), NASA's Pathfinder, and to a lesser extent Facebook's Aquila employ the use of many small motor propeller sets instead of one or two engines like most planes. Why is this?

Smaller motors tend to have slightly higher power density, but aren't the relative losses higher on the smaller airfoils of these propellers?

Because they are very lightweight and fragile. Therefore, thrust and propulsion mass must be distributed over span - a single, large propeller and motor would put too much force into the structure locally. Also, it would require a higher landing gear to give the larger propeller the required clearance.

You are right about the higher losses. However, these airplanes were built to reach record altitudes, and wing loading must be as small as possible to make that possible. Also, boundary layer problems on propellers are less severe than on wings because the rotation will cause the slowed boundary layer to be moved outwards from centrifugal forces. There the blade moves faster which will very effectively suppress flow separation.


This concerns the GE90X fanjet engine which generates 130,000 LBS of thrust at takeoff This concerns the GE90X fanjet engine which generates 130,000 LBS of thrust at takeoff.
But for this example the engine is secured to a test mount, and under "full throttle", the thrust generated is still 130,000 lbs.  I believe that 80% of the thrust is from the fan itself.. but let's go ahead and assume 100% of the thrust is generated by the fan only.
If the large 12-foot ducted fan were instead connected by shaft to an external electric motor or gas engine, how much horsepower would be needed, to sufficiently spin the large ducted fan, to generate 130,000 pounds of thrust ?

This is almost a duplicate of another question: What is the GE90-115b turbine power output in horsepower?
With the fan removed, and power used for e.g. ship propulsion or a power plant, the engine core can deliver about 66 MW or 90,000 horsepower continuously.
Takeoff thrust is higher than continuous, and the core does contribute some thrust. So to match 130,000 lbf, a fan this size would require external power in the range of 80-85 MW or about 110,000 hp.


What are variable stator vanes? Most turbofans nowadays use "variable stator vanes"; what are these, what is their purpose, and how does it affect a gas turbine's performance?

A fan blade at the front or turbine blade at the back of a jet engine is a small aerofoil surface which is fixed to the main shaft and spins with it. By contrast, a stator vane is a similar aerofoil surface fixed to the outer casing and remains static.
Why do that? The spinning blades of a given stage cause the airflow to start spinning, and that slows the relative speed of the next stage (two things spinning together are at rest with respect to each other). The stator vanes "un-spin" the airflow so that the next stage blades meet it at full speed.
A variable vane pivots about its spanwise axis, allowing you to change its angle of attack to the oncoming airflow. Why do that? A turbojet engine at different stages in the flight will have different demands and conditions on it and will accordingly spin at different speeds. These effects change the airflow pattern through the engine. If a given stator vane is optimised for one stage of flight, it may not work so well in the modified airflow when a different stage is reached. Varying its angle can ensure that it can always be set at the optimum angle for the best performance.
So variable stator vanes ensure that a given jet engine can always operate at maximum efficiency and deliver optimal performance.
A typical way this is done is to fit gear wheels on the outer ends of the vane pivots, and place a single large toothed wheel around the whole engine so that when the large wheel turns, all the vanes in that position turn with it.


What is the difference between "Type Certificate" and "Certificate of Airworthiness" for an aircraft? I want to know what exactly is "Type Certificate" and "Certificate of Airworthiness" means for an aircraft.

A Type Certificate is a certificate that the FAA gives the manufacturer of an aircraft, certifying the design of the aircraft. So for instance, Cessna Aircraft Company of Wichita, KS holds a Type Certificate for the Cessna 172. Notice that the certificate specifies what components make a Cessna 172, what its limitations and performance specifications are, and so on. When Cessna makes a 172, that aircraft has to conform to this specification. Moreover, only aircraft that meet this specification are certified as a 172. Which is why, if you make a major modification to a certified aircraft, it requires an STC-- a "Supplemental Type Certificate," to confirm that with the new equipment, the aircraft design is still airworthy and the limitations are accurate. But there is only one Type Certificate for an unmodified Cessna, and it is issued to Cessna, Inc.

On the other hand, an Airworthiness Certificate is issued for each aircraft individually and certifies that this here particular airplane is airworthy. They can be revoked if the airplane undergoes, for instance, an accidental major airframe modification (or indeed, an uncertified major alteration of any kind or if for some reason the FAA has reason to believe the aircraft is no longer airworthy). Each aircraft has its own Airworthiness Certificate that is displayed in the passenger compartment, and thus there are as many Airworthiness Certificates for Cessna 172's as there are airworthy 172s.


Does a lean mixture result in a higher cylinder temperature for a given power setting? From what I know over rich mixture help cools the engine due to evaporation process and lean mixture do the opposite.
So why this graph showing when reaching around peak EGT the opposite happens:

To oversimplify, you could say it's because when you are rich of peak you are getting temperature reduction from too much fuel.  When lean of peak you are getting temperature reduction from too much air.  Watch this guy's youtube video seminars.  They are a treasure.


How to properly enter a holding pattern? Once ATC have assigned me a holding pattern, how do I determine where to intercept it?

And once that I have determined the intercept point, how do I proceed?

I have heard about the teardrop and the parallel entries, are there others? How do I select the most appropriate entry?

During the intercept maneuver, can I assume[1] that the appropriate airspace is free (since ATC told me to intercept that hold) or there is high risk of coming close to other aircrafts?

[1] this does not mean that I will not look at the radar/out of the window, is just to know the level of attention that I have to pay to this aspect.

to source from wikipedia:

  There are three standard types of entries: direct, parallel, and
  offset (teardrop). The proper entry procedure is determined by the
  angle difference between the direction the aircraft flies to arrive at
  the beacon and the direction of the inbound leg of the holding
  pattern.

  A direct entry is performed exactly as it sounds: the aircraft flies directly to the holding fix, and immediately begins the first turn
  outbound.

  In a parallel entry, the aircraft flies to the holding fix, parallels the inbound course for one minute outbound, and then turns
  back, flies directly to the fix, and continues in the hold from there.

  In an offset or teardrop entry, the aircraft flies to the holding fix, turns into the protected area, flies for one minute, and then
  turns back inbound, proceeds to the fix and continues from there.

As you can see the maneuvers are all inside the area circumscribed by the holding pattern (not counting flying directly to the holding fix) so you can assume the airspace is clear at your altitude.

Important to note is that you should fly directly to the beacon and then reorient yourself as appropriate.

The airport approach charts will indicate where the beacons/landmarks are located, which code they use and which heading the "inbound" leg (when flying towards the beacon) has.


Why would it not be OK to replace a map light bulb with an LED? In the question about if it's OK to change your own map light, why did JScarry say "don't you dare replace [your map light] with an LED"? Or was he kidding?

White LED spectra contains quite a bit of blue range wavelength, which is bad for night vision.  Red light is much better.
The eyes have cone receptors for day time and rod receptors for night vision.  The rods contain rhodopsin, which enables night vision.  It takes about 1/2 hour for enough to build up to have full night vision.
Exposure to shorter wavelengths quickly breaks down rhodopsin, which is why blue light is to be avoided.
Natural sunlight is strong in blue (and UV) spectra.  Incandescent tungsten filaments have much less blue/green spectra, and a lot more orange/red.  So it may be a bit "old school" to shun LEDs.
Newer OLEDs have spectra closer to candles and incandescent.
One interesting measure is how much the light suppresses melatonin, which helps one sleep.  Newer OLEDs were found to be only fractional of blue light, so it would be important to be sure any replacement map light is appropriate for the task.


What is the date of first use of the TAF format? Unlike METAR and NOTAM, I cannot find any history on Terminal Aerodrome Forecast (TAF). Any hint as to the age of the format would be appreciated.

For the current format, it was 1993 when it was standardized.

On July 1, 1993, a new, revised Terminal Aerodrome Forecast (TAF) format and code replaced the existing TAF code. This new code is in effect in most countries. The exceptions are the United States and Canada. These two countries issue Terminal Forecasts for domestic use and TAFs for the military and those airports serving international aviation.
On January 1, 1996 the U.S. and Canada will convert entirely to the new TAF code. After that date, the new code for weather reports (METAR) and TAFs will be used worldwide. The North American code used in the FT (and SAO) will be discontinued. Although the new TAF code is being adopted worldwide, each country is allowed to make modifications or exceptions to the code for use in each particular country. The TAF code, as described here, is the one used in the United States for those airports serving international aviation and will also be used after the January 1, 1996 conversion date. The World Meteorological Organization's (WMO) publication No. 782 "Aerodrome Reports and Forecasts" contains the base METAR and TAF code as adopted by the WMO member countries. (Source)

noaa.gov also confirms the date for the US.
The WMO publication No. 782 can be found here.


Can a part 103 ultralight weigh 400kg fully loaded? I am designing an electric VTOL personal part 103 ultralight.

My question is: I have 114kg for the ultralight, 100kg for the pilot and 30kg for the baggage. About 260kg is enough to be take off safely but I want to design it up to 400kg.

If I do that, will it still be accepted as a part 103 ultralight and what is the weight limit for it?

Part 103 limitations pertain to dry weight in takeoff configuration, maximum stall speed, maximum level flight speed, and maximum fuel capacity.  They do not directly address maximum gross takeoff weight.

However, weight affects stall speed, and I'm not certain how Part 103 defines its stall speed limit -- whether they specify at some minimum operating weight, or at "design weight" or some other value.  The complete regulation is available online, however, so you can read it yourself and determine if you'll be able to design for your maximum 400 kg GTOW.


What percentage of airplanes are involved in a crash in their lifetime? The chances of a commercial flight crash are about 1 in 1,200,000 - pretty low. If each plane makes about 40,000 flights in it's lifetime, about 1 in 30 airplanes will be involved in a crash before it reaches retirement.
Is this an accurate estimate? 1 in 30 seems like quite a large amount of airplanes to crash before they are retired.
I'm also assuming here that after a crash an airplane is written off. This may not be the case - I don't know how much a plane can be repaired.

I just ran some numbers based on Wikipedia statistics. I don't know how they define "incident or accident" but hull loss is pretty straightforward. That means it was written off.

Aircraft type
Total made
Incidents/accidents
Hull losses

DC-10
368
55 (14.2%)
32 (8.3%)

L-1011
250
32 (12.8%)
11 (4.4%)

727
1832
336 (18.3%)
118 (6.4%)

737
8725
368 (4.3%)
184 (2.1%)

747
1514
131 (8.6%)
60 (4%)

All of these were introduced in the late 1960's. As you can see, the DC-10, L-1011, and 727, which are mostly retired, have pretty bad numbers. But the aircraft that are still being made and flown have much better stats. I think this is probably due to the fact that air travel gets safer all the time. The planes that had their heyday in the 70's and 80's fared poorly but the longer they continue to be produced, the less likely they are to crash.


Why does fuel consumption decrease with increasing aircraft altitude? I have a chart where the thrust ($F$) and the thrust-specific fuel consumption (TSFC) are plotted against the aircraft flying speed, for several altitudes (i.e. sea level, 3000 meters and 11000 meters). This is for a generic turbojet.

I don't know the source of the image, I apologize for that.

At the left, we see that the thrust decreases with altitude. At the right, we observe that the TSFC actually decreases with altitude as well.

However, I think this is counter-intuitive. I understand that $F$ decreases with altitude, since density (and therefore mass flow rate) decreases when the airplane goes up.

What I don't understand is that the TSFC, defined as: $$\text{TSFC}\equiv\dfrac{\text{fuel mass flow rate}}{F}$$ decreases with altitude. In other words, the higher we fly, the more thermodynamically-efficient the airplane is. How does that happen?

From a pure mathematical point of view, it doesn't make sense that TSFC decreases with altitude since, following the aforementioned formula, $F$ is decreasing, which leads me to think that the fuel mass flow rate diminishes with altitude faster than thrust.

In a nutshell: why does the TSFC decreases with the flying altitude, having the last equation into consideration?

I can't provide the math, but yes, this is correct. Fuel flow decreases as air density decreases. The engine becomes more efficient because of the greater temperature differential between inlet and exhaust gases combined with the lower fuel flow.


Can flight crew book tickets for themselves, on the same flight? Is it possible that flight crew book a ticket for themselves, for say utilizing their rest time better (like Emirates offers mid air shower to first class passengers, but not to crew)?

Since the pilot won't check-in their flight bag, the booking will be cancelled (no-show).
They won't board with the passengers, so they won't be counted, same end result. Answer is no.
Many airlines now prohibit active duty (including relief) flight-crew from mingling with the passengers. Long gone are the days of the pilot walking up and down the plane.
That would be the most expensive shower in the history of showers. A first-class Emirates long haul flight is easily $24,000 (SFO-DXB).
Crew rest areas are beds for a reason, a shower goes against the idea of sleeping (may not be a universal thing though). But I wouldn't want to see my flight-crew in a robe going to bed after a nice warm shower. Unless the robe comes with epaulets.


Is the commonly assumed UFO (flying saucer) design aerodynamically efficient? Is this design, a circular disc (or flying saucer) slightly humped on the top and bottom aerodynamically efficient? And if, we are able to use it for commercial purposes , would they give a better efficiency than existing aircraft?

This article states that this would be a better design. Is this true?

They use the concept of VTOL thats vertical Take off and Landing. Click here to know more about VTOL

Regarding the efficiency, well I think no one can give a 100% perfect information on this because, we do not know the fuel used, the engineering behind the structure. There are a lot of factors affecting efficiency like :
Materials, Fuel, Type of Engine, Weight etc. So aerodynamics alone cannot judge the efficiency of the aerovehicle.
Thanks!


How does SLATS/FLAPS retraction damage the RTLU mechanical stop if we retract them after the ADIRS are set off? From the A320 After landing FCOM NORMAL PROCEDURES:

  To avoid damage on the RTLU (Rudder Travel Limit Unit) mechanical
  stop, the SLATS/FLAPS should be retracted before all ADIRS are set to
  OFF simultaneously.

What happens if the SLATS/FLAPS are retracted after the ADIRS are set to OFF? How will the RTLU be damaged?

According to this PPRuNe thread, the problem is not the retraction of the slats/flaps but instead turning the ADIRS (air data inertial reference units) off. The RTLU is designed to operate in a feedback loop, where its position is controlled based on input from the FACS (Flight Augmentation Computers, which take input from the ADIRS). If the ADIRS go offline while the slats are extended, the RTLU goes into a "emergency return to low speed" mode. This allows maximum rudder travel by driving the RTLU to mechanical stops. If this happens regularly it can cause damage to the stops.

This appears to be related to the Indonesia AirAsia Flight 8501 crash. Although this issue was not one of the main contrbuting factors, the report lists this as one of the Technical Followups (TFUs) that Airbus issued as a result of the investigation. It improves the reliability of the RLTU, the failure of which was cited by the investigation.

See this related question for more on the function of the RTLU in the flight control system: What are the “channels” on the A320 Rudder Travel Limit Unit?


Do runways need to be repaired after gear up landings? There have been may cases of civilian, commercial, and military flights that have either been forced to or accidentally landed gear up.

When this happens I imagine that it can do serious damage to the runway it's landing on (assuming it's landing on a paved runway).

Does the runway need to be repaired after such a landing, if so, how long does it take, and how extensive are the repairs?

These are some of the different scenarios that come to mind:

Civilian aircraft doing a gear up landing, maybe about 1500-5000lb or so.
Commercial airliner doing a full gear up landing.
Commercial airliner with a single broken wheel.

How would runway repair be conduced in these scenarios?

Runways are usually made of several feet of reinforced concrete. Any damage to them after a wheels-up landing is superficial at best. Details depend on circumstances, but in general light aircraft will cause less damage. A full wheels-up landing is rather easy on the runway: The aircraft's fuselage and wing fairing structure are flexible and malleable, so it will buckle and bend until the local surface pressure is too low to cause more bending. To really damage a concrete surface you would need carbide tools, not sheet aluminum.

An unwheeled landing gear strut of an airliner is probably the worst scenario. The Airbus in the linked video had only a damaged nose gear, which carries a small fraction of the total load, and you will see in the close-up at the end of the video that the runway did not suffer. A similarly damaged main gear, however, will cut a groove.

All what is needed for repair is some fast-curing liquid for filling the nicks and scratches and some paint to repair the runway markings.

If you land a composite aircraft wheels-up, the concrete will act like sandpaper on the structure. The landing zone will be marked by white epoxy dust. A broom is all what is needed to put the strip back to its initial condition.


How can I modify a fuselage to increase the payload? I'm designing a regional turboprop for a university assignment. The design requirements are very similar to the Dash 8 Q400 in terms of passenger capacity (90 pax), speed, range, runway length requirements. The difference is the payload mass required is 35% greater (8,500kg to 11,500kg).
So I've sized my wings and my engines and control surfaces and flaps and they're all bigger. My issue now is the fuselage. Since the passenger capacity is the same I have less motivation to increase the dimensions.
Increasing the diameter for the sake of more internal volume seems inefficient; I don't need more aisle and armrest space. On the other hand, increasing the length (without increasing diameter) would mean a heavier fuselage structure.
Even once the fuselage is lengthened, where do I put the cargo? For the Q400, cargo holds are right at the aft and just before the cockpit. But if this is my solution I'll be shifting the centre of gravity and creating even greater bending moments.
My ideas so far are to create a  near c.g. cargo hold that would likely split seating or to utilise space available under the floor of the cabin. I haven't seen any designs that support these ideas though (for narrow bodies).
I tried to look for twin-engine turboprops with similar payloads, the only one I found was the C-27J Spartan (military transport), but it's practically designed for cargo.
Could someone give me some wisdom on how I should proceed? I've done quite a bit of reading and research but can't resolve this aspect of the design.
Here's the 74 seat cabin layout for the Q400.

You really only have two options; stretch or swell.
The Q400 already has a "combi" configuration option with 50 seats forward and a cargo hold taking up the aft third of the cabin, so if you want to just add another couple of plugs, one (smaller plug) forward of the wings and one aft, to get 74 seats plus a large cargo area, you can do that and just adjust the structural requirements to deal with the even longer flying pencil that results.  You can have a cargo hold aft and pax cabin forward with the appropriate weight and balance requirements and limitations for loading pax vs cargo same as any other split combi layout.
In the case of the Q400 itself, its configuration is already at the extreme limit of what you can do with fuselage stretches on that sort of 4-across tube diameter, having started with 36 seats in the original.  The plane suffers from tail clearance problems because of this, due to limits on how much the gear legs could be extended to account for the long tail (landing with less than full flaps - there are a couple of intermediate landing flap settings - has a high risk of tail strikes and pitch attitude must be very carefully managed in the landing flare).
I think you'd get a better aircraft by going with "swell" and increasing the tube diameter enough to get a 5 across cabin (around 2 feet), with 2 on the left side and 3 on the right. A 74 pax 5-across cabin would only need 15 rows, leaving the rest free for cargo, and this extra width plus shortened passenger area might even allow you to shorten the fuselage a bit, leaving some stretch-ability potential in your initial design (you might even get bonus points for taking this into account).


Is the Brodie landing system still in use somewhere? The Brodie system was a method for taking off and landing without a runway, circa 1945. The landing or taking off aircraft was hung on a wire held at the appropriate height:

From PhotoBucket, Duggy009

It could be used on a ship too:

From Youtube: Brodie Landing System

Two advantages of this system: Easy to conceal and capacity to operate to/from areas unsuitable for an airstrip.

This system seemed promising, especially for armies, but I never heard of subsequent use. Why was it discarded? or if it wasn't, what application do/did exist following this WW2 experimentation?.

I'm not aware of the Brodie landing system used anywhere now. The system was actually a response to the pressing problem of non-availability of escort carriers in required numbers, similar to the British CAM ships, that launched hurricanes on one-way missions. The only difference being that the aircraft could be retrieved here.

The main advantage of the system is its ability to operate from (cargo) ships and LSTs, which became less important as the war progressed and more and more aircraft and escort carriers became available. There were some disadvantages too- it required certain skill from the pilot for landing (especially if installed in a jungle or on the top of a building). Also, a 600' cable between two 65' posts can hardly be called small (and as @ymb1 noted, it is hardly practicable for larger aircraft).

Helicopters serve the same purposes- operate from anywhere with much heavier payloads and in non-existent airstrips routinely.

However, similar systems are used for retrieval of small UAVs. For example, the Boeing Insitu ScanEagle uses a similar system of retrieval (though the launching system is different). From uavglobal.com:

  ScanEagle needs no airfield for deployment. Instead, it is launched using a pneumatic launcher, patented by Insitu, known as the “SuperWedge” launcher. It is recovered using the “Skyhook” retrieval system, which uses a hook on the end of the wingtip to catch a rope hanging from a 30-to-50-foot (9.1 to 15 m) pole.

Scan Eagle retieval; By United States Navy, Mass Communication Specialist 3rd Class Kenneth R. Hendrix - Navy NewsStand Photo ID: 071114-N-5758H-065Navy NewsStand Home, Public Domain, Link

There are patents for a number of similar systems (eg 1,2 and 3). Interestingly, Insitu calls its skyhook system:

  ... the first capture system to eliminate runways and nets

Apparently, they didn't get the memo.


What makes the loss of a flap track fairing strongly increase fuel consumption on Airbus planes? Inspired from this question about the loss of a flap track fairing.

In the answer by Thunderstrike, a part of the configuration deviation list of an Airbus A320 is linked. In it, it says:

  One fairing may be partly or completely missing.

  Performance

  Fuel consumption is increased by 3.14%

That really is a lot!

I found a post on Airliners.net citing the CDL of a B757:

  Straight out of the MEL/CDL manual for the 757, The item falls under CDL 27-51-1 which states there are 6 installed [Flap Track Fairings, Remark] on the aircraft and up to one per side may be missing. No fuel burn penalty but there are a few small weight penalties, no speed penalty. Our A-300's with the same CDL item does have a 1% fuel burn penalty and only one can be missing out of the 10 installed. I see this item come up 3 or 4 times a year, no biggie.

What causes this very high increase in fuel consumption on Airbus planes?
What are the differences between the fairings of a Boeing and an Airbus (because Boeing has no increased fuel consumption, Airbus has)?

The fairings double as anti-shock bodies (or Küchemann carrots) and help to reduce shocks on the lower side of the wing. Below you see a wind tunnel test from the Vickers VC10 development where flow visualization using oil was used at Mach 0.9:

Wing without (left) and with (right) anti-shock bodies at Mach 0.9 (picture source). The light line on the left side indicates a strong shock which increases drag substantially over the situation pictured on the right where the flap track fairings have been used to smooth out the sudden reduction in cross sectional area from the rear-loaded wing airfoil.

Please read this answer if you are unsure why aircraft experience more drag as they approach the speed of sound. By stretching the aircraft body over a larger length, the gradients in the cross sectional area distribution can be made more shallow such that the air has more opportunity to make way for the aircraft.


Why can't this blended wing body trijet airliner fly? I was told in this other question this aircraft was not real, and that it could not fly in this design.

I'm now interested in knowing what would prevent it to fly, from an engineering point of view. It looks great... why is it so obvious this cannot work?

As the comments point out, the main landing gear is too forward. Delta wings (and blended) typically land (and takeoff) with a high nose-up, should be an easy fix.
Left wing is longer, again easy fix.
Outboard control surfaces (normally would be elevons) are both pointing down on approach (or is it climbing?), tail heavy?
For a blended wing body, the airline still chose a tail-fin logo (backwards mind you)!
Natural pitch stability is required for certification, but the way it looks this design is unstable in pitch. Note that all trailing flaps are deflected down, something which will generate strong pitch instability. There is no obvious means by which a counteracting pitch response could be generated.
It looks as if payload is held mostly in the forward part. While it could be balanced when empty, with any sensible amount of payload it will be hopelessly nose-heavy.

Related: Why is there really only one basic design for passenger airplanes?


Is the A380 ailerons' kinematic modified in alternate law? I was looking at a video of a A380 display that led me to the "valse des ailerons". This strange ailerons behaviour is available in normal law, but what happen when some fly-by-wire features are not available (alternate law and direct law)? Is this kinematic still available or do all the aileron move together acting as if there was only one aileron per wing?

EDIT: As I received no responses but multiple good comments, I add some clarifications:
The "Valse des ailerons"' purpose and operating is documented in many places (see comments) but all those documentations assume the fly-by-wire system (sensors, actuators, computers,...) is healthy enough to stay in normal law. My question is: what happen when in alternate or direct law? Is there multiple cases, some in which the valse des ailerons is still available and some in which it is not?

Valse Des Ailerons (Waltz of Ailerons) or VDA is a nickname for the Load Alleviation Function (LAF) which is part of the flight control system. LAF uses all ailerons and spoiler 6 to 8 to alleviate the fatigue and static loads on the wings by reducing the wing bending moment.

It consist of various sub functions dealing with passive load alleviation (based on commanded load factor from normal law) and active load control based on measured accelerations in pylons under the wing.

From this it already follows that passive load alleviation requires normal law for load factor inputs.

There is a document circulating on the internet which seems to be an official Airbus Pilot Briefing for A380 pilots called "Flight Deck and Systems Briefing for pilots, issue 2". In the section about the Flight Control Systems under auxiliary system the following is said about the LAF:

  Load Alleviation Function (LAF) The objective of the LAF is to reduce structure fatigue and static loads on the wing during maneuvers
  and turbulence. Spoilers 6 to 8 and all the ailerons are involved
  in the LAF.
  The LAF is available in normal law only.

(Emphasis added by me)

So your feeling that Valse des Ailerons is only active in Normal Law is correct.

Update: Based on the A380 flight crew manual, it depends—


What is the resolution of airport ground radars? In largest airport a ground radar is used to handle safely aircrafts on taxiways and on runways, which should be the characteristics of this kind of radar ? What about its range and bearing resolution ?

For surface movement radars (SMR) operating in the 9 - 9,5 GHz band, the pulse length is typically in the order of 40ns. This is equivalent to 12 meters. That would bring the theoretical minimum range to 6 if we ignore transmitter / receiver switching overhead time.

In practice there is no need for such a short range. Instead a pulse train is transmitted before the antenna is switched from the transmitter to the receiver. This allows the radar to increase the accuracy by averaging multiple reflections, at the price of an increase in minimum range. Typical minimal range will be in the order of 100 meters.

Other SMR systems use continuous wave radar and have a transmitter and receiver antenna in the radar head. These systems don't require to switch between transmitting and receiving and don't have a minimum range.

The range resolution is in the order of 3 meters, equivalent to the pulse rise time of about 10ns.

The azimuth resolution of a typical SMR is in the order of 0.25 degrees, which is equivalent to 10 meters at 2 km distance.

Apart from primary radar there are other classes of surveillance systems in use for airport surface detection.

Secondary surveillance radar (SSR) lacks the accuracy of the SMR and
can only see transponders. But combined with the primary radar allows
for identification of aircraft on the airport surface (i.e. putting
identification labels on the aircraft's primary radar reflection).
Multilateration (MLAT) systems also rely on transponders but are more
accurate than SSR for surface monitoring. These systems require a large number of receivers and are susceptible for radio reflections from buildings.
ADS-B relies on the aircraft (or airport vehicle) transmitting its
position, speed and heading.


Under which condition is a forward CG most critical? This question is from CFI written exam. (6824)

“Under which condition is a forward CG most critical?”

The answer is

“Forward CG is most critical during landing. If it is too far forward, the elevators may not have enough power to get the tail down for a proper approach and flare.”

I don’t know why if CG is too forward, the elevators may be less effective. In my mind, if something has longer arm, that one becomes more effective like teeter-totter.

That would be great if someone could help me!

One intuitive way to think about this is that the pitching motion of a rigid body occurs at its CG. At forward CG, the elevator, which pitches the aircraft up, indeed has a longer moment arm. On the other hand, however, the wing lift vector, which tends to pitch the aircraft down, also has a longer moment arm. The proportion of change of the wing lift moment arm is quite a bit more than that of the elevator, for the same change in CG. In the end, the wing lift, which is also quite a bit larger, wins this race. Hence, forward CG is more critical for maneuvering.

Strange that it says landing, which I assume is the flare portion, is the most critical condition. I would've thought takeoff rotation would be equally bad, especially if you have a mistrim.


Why are many jet aircraft designed to cruise around FL350-370? If the flight distance permits, the B737-800 will cruise at FL350, the A320 a little bit higher...

Flying at FL370. Photo: Live from the Flight Deck by GolfCharlie232 (reframed)

Elements such as time to reach cruise altitude, engine and airframe efficiency at this altitude, and acceptable cabin pressure surely influence the choice, but:

What are exactly the important criteria used, and the compromises made by engineers?
Would engineers choose other altitudes if the technology or any other current limits could be improved?

In a word, the tropopause.

Gas turbine engine efficiency improves with colder & denser air. As an airplane climbs through the troposphere, the density & temperature both drop, and the loss of density is more than offset by the lower temperature. Above the tropopause, however, the density continues to drop while the temperature holds (approximately) constant.

In the U.S. Standard Atmosphere model, this occurs at 36,089 feet. This represents a local (possibly global) optimum altitude for efficiency (and if there is a better optimum at a higher altitude, it's inaccessible for other reasons).


How likely could there be a loss of cabin pressure? You often on commercial aircraft (whilst on the ground to the runway) hear on the safety video:

  in the event of a loss of cabin pressure, oxygen marks will be released from the panel ....

What could cause a loss of pressure? Is it at all even possible for it to just drop?

Season's greetings :-)

Aircraft incidents are an extremely remote event (they say that you're more likely to be killed in a car accident on your way to the airport than a plane crash). Within all the incidents that engineers foresee, some are more likely than others. These incidents are included in pilot training (and passenger briefing if applicable) to increase the likelihood that it can be handled properly. Loss of cabin pressure is one of them.

Technically air pressure inside the cabin cannot be "lost", but the term is used to describe a significant drop in air pressure. The masks deploy when cabin altitude is around 14,000 feet.

Cabin pressure is provided by two methods:

The engine actively pumping air into the cabin
The fuselage is sufficiently sealed to contain air pressure inside (it is not 100% sealed, but the pump is powerful enough to overcome the small leakage)

Failure of any of these two components would lead to a loss of cabin pressure.

Historically, causes of cabin depressurization has included:

Failure of all engines, whether due to volcanic ash, fuel exhaustion, or any other reasons
Failure of all air conditioning units on the aircraft
Incorrect setting of the air pressurization unit
Rupture of fuselage
Door flew off the aircraft
Cockpit window flew off the aircraft


What is the hole located below the 2nd or 3rd window of Boeing 737? I see there is a hole located below the 2nd or 3rd window. What is its purpose?

(Sources: flickr.com and planespotters.net)

Static ports. (capt & FO).

For sensing static (atmospheric) pressure ultimately used by various flight instruments (such as airspeed indicator, altimeter, etc.)

(Source: b737.org.uk)


How do I calculate top of climb? How can I calculate the distance on the ground during the climb?

Assuming the climb power is 700ft/min, the climb speed is 65 kts, the wind 260/10kts on runway 26.
Start: 700ft
Top of climb: 3500ft

How far is the distance flown on the ground (in e.g. ft) and the GS?

What I understood:
The difference in altitude is 2800ft and therefore 2800ft / 700ft min = 4 minutes. I can say that I fly 4 minutes long 65 knots:
65kts -> 6582 ft * 4 = 26 328 ft but I don't use the wind in this calculation.
Can someone please help me?

Thanks!

That 65kts "climb speed" -- is that ground speed or air speed?

If it's ground speed, then you already have your answer. Since the question is about ground speed and distance travelled, then the wind doesn't factor in to it.

If it's air speed (which is far, far more likely), then you need to figure out your ground speed first. This is where the wind comes in. Now, you didn't specify which direction you're flying, but we can assume from the mention of "runway 26" that you're flying 260 degrees. That means you're flying into a direct headwind, which means in turn that your ground speed is simply your airspeed minus the wind speed. Then use that value in your distance calculation.


Why do military pilots report "gear down" during their traffic calls? I've noticed that military pilots will often say something along the lines of:

  <airport> traffic, Basher 5-2 left base, full stop, gear down.

Why the additional "gear down" call?  Shouldn't it be implied that if you're landing full stop, you'd want the gear down?  And similarly, if the gear isn't down, wouldn't an emergency call be more appropriate?

To be clear, I'm not asking why it's a good idea to check to see if the gear is down, I'm asking why military pilots broadcast the fact that they've checked.

1In the U.S., for Military aircraft, ATC is required to:

  "Remind aircraft to check wheels down on each
  approach unless the pilot has previously reported
  wheels down for that approach". [ref: [FAA Order 7110.65W], para. 2-1-24]

Normally, the phraseology suggested in your question would reflect the pilot's response to this ATC reminder. (For example: "[call sign] Check Wheels Down, Cleared for [whatever]")


Do large Airliners use full thrust when reversers are deployed? Do large and heavy Airliners, Jumbos and Super Jumbos wide bodies included use full thrust for braking when reversers are deployed?  What is the thrust setting?

Flight manual procedures and operators‘ policies notwithstanding, they would typically use full reverse thrust when the stopping performance requires so, and idle reverse thrust when not. The latter setting means less wear on the engines and lower noise. The former setting overrides these considerations when safety demands it.


What is the best procedure for landing at my destination if I have a full electrical failure at night? What is the best procedure for landing VFR at the intended destination airport and I have an electrical failure, in the following scenario?
Let's assume this is a VFR flight and I'm 50 miles from the departure airport in the United States, which is a cross country flight. There is no issue with the weather. I have noted no issues with the Cessna 172's electrical power at run-up prior to takeoff, I have at least an hour of fuel reserve and meet all the 91.205 requirements.
I then experience an electrical failure during the en-route phase to the intended destination airport, and I have done the necessary checklist to try to solve the issue but it doesn't fix the problem. As I approach the vicinity of the airport, I key the mic seven times (high intensity) and no runway lights appear. I expect it is too risky to land on the road because there could be power lines nearby.
I found the following scenarios on the internet but they don't answer my question:

Pilots flying to a towered airport (still open at night) with full electrical failure, squawking 7600, and waiting for ATC's light gun signals to appear.
A pilot has the same issue and is lucky when a plane turns on the runway lights and lands before him, but he doesn't commit an emergency
The pilot is lucky at landing at a towered airport that is closed while the lights are still on, but the lights turn off or dimmer to pitch-dark as he begins to land

I came up with my scenario myself because I can't find information about it on the web. It would help me if you could provide suggestions and tips on what I should do or not do when this happens to me in the future.

Here's an investigation report on this very sort of thing in Canada.  Note that the standard procedure to alert ATC that you have a total electrical/comms failure is to fly a left hand triangle twice with 2 minute legs, every 20 min.  If they can see your non-transponder target they will quickly get the idea, and then make allowances for whatever you do next  As with IFR comm failure procedures, you should be careful to make the "next" thing you do the most logical thing for the controller to expect.
If there was an operational controlled airport with lights that was the only safe place to go to get down in one piece, I would proceed there doing the triangles, then when in visual range of the tower do another triangle until I got the flashing green light from the tower. And if I didn't get the light, and I was running out of fuel, I'd just go ahead and land.
Important thing to remember in aviation is that the regulations aren't a suicide pact, and once it's life or death, you do what ya gotta do, end of story, and while you may have to do a lot of report writing, if you crossed some lines taking reasonable action to save yourself and passengers, you won't get busted for that - hopefully.
If you're stuck with no other airport to go to with lights, and your darkened destination is the only option, well, you kick yourself for being so foolish as to fail to make allowances for that eventuality (which is not really that improbable), take your chances, and hope it turns out.
Of course, it is the early 21st century, so you should have your phone with you no?  So unless you left it behind or the battery is dead, call somebody. The destination airport operator to turn the lights on.  Someone you know there that can light up the runway with a few cars.  An air traffic control unit.  911 even.


Is it possible to balance a tail heavy plane with a vertical prop on its tail? I've put together a model plane in the form of an angel, and the planform is quite tail heavy (please see pic).
I'm trying to balance the plane with a lifting tail prop that makes the "apparent" CG in the place where the CG should be.
I've launched the plane twice. The first time it seemed like there wasn't enough forward thrust. The second time the tail rotor didn't have enough thrust and it pitched upwards. (Please see video links).
Will this concept work if tweaked properly?

Tryin' to cheat the laws of stability, aren't we?

In both videos it is evident that the plane is unstable in pitch. Adding a lifting prop will not change this, because changes in the angle of attack will not affect this prop's lift force much. Stability is achieved by shifting the center of gravity forward, so that changes in the angle of attack will produce additional forces which create a counteracting pitch moment.

In fact, adding the motor will shift the center of gravity even further back. In some cases this helped because the increased pitch inertia made it easier for the pilot to keep the aircraft under control.

If you need to keep the center of gravity so far backward, add artificial stability with a pitch rate sensor and a microcontroller which deflects the elevator appropriately. There are many pages with Arduino-controlled artificial stability solutions - take your pick!


Would an airliner be allowed to take off in snow? Im going to fly to Tucson tommorow. The weather is telling me its going to snow in Denver. So would snow cause a delay or are airliners allowed to take off in this kind of weather?

Don't worry about it
While snow can sometimes cause a delay, airports are really good at snow removal.  (Especially airports like Denver that are used to getting a lot of snow.)
According to flydenver.com DIA has 500 trained snow removal people and 270 pieces of equipment to clear 12.2 million square feet of runway, taxiways, etc.
To put that in perspective, a typical highway (2 lanes each way, with shoulders) is around 38 feet wide each way, or 76 feet for both directions.  If I've done the math correctly, 12.2 million square feet is about 30 miles of road.
The state of Minnesota knows a thing or two about plowing snow.  They use about 1500 drivers and 839 plows to handle 12,000 miles of road.  To plow snow the way the Denver airport does it, they would need 200,000 drivers and 108,000 plows.
Here's a YouTube link that shows off some of Denver's bigger snow removal tools.
Chances are, if you can get to the airport you'll be able to fly (but perhaps not on time)


Are there tricks or training to handle spatial disorientation? For spatial disorientation, are there tricks to block out certain inputs like focusing on what the eyes see and blocking out the ears? I am curious if there are training techniques to practice on the ground to help with spatial disorientation. Do you have any techniques to practice?

The issue with spatial disorientation is that sensory input is insufficient (based primarily on vestibular input) or that the pilot fails to properly process sources of valid orientation.

Generally, when we refer in aviation to spatial disorientation, we really mean attitudinal disorientation.  (Spatial disorientation could also mean not knowing where we are relative to a fix or navaid, as an example. Rather we are really interested in pitch and roll.)

Primary input for attitudinal orientation is an artificial horizon, which emulates a visual horizon providing pitch and roll information. Secondary input can come from a combination of altimeter, turn indicator, and variant instruments (VSI, DG).

With respect to techniques and practice, the standard method is developing a discipline to rely on the AI and associated instruments, and to force a reliance on the instruments, particularly when the pilot senses a conflict. Some people acquire this discipline quickly and others take longer. The general standard for teaching is to continue to provide practice and diverse evaluation opportunities, until the pilot demonstrates consistent correct behavior.

Assuming primary and instrument students are acquainted with the basics, I tend to employ frequent "unusual attitude" opportunities. My experience has been that students who perform well under stress, generally perform well without stress. Unusual attitude opportunities can be instructor induced opportunistically, such as when flying to and from the practice area. When putting on foggles, I customarily will have the student raise their head up after having "reoriented" the aircraft. This may happen 4 to 10 times, sometimes more, in a lesson, and generally students get very proficient.

An alternative technique, which is often done on student cross countries, is to have the student close their eyes, and continue to try to keep the plane straight and level, and then command them to open their eyes once some attitudinal change has presented itself. (There is a secondary benefit to this method, and that is it encourages proper trim maintenance.) If the student has a view limiting device on (foggles) then they get the opportunity to recover using instruments. If they do not have a view limiting device, then they can benefit from both instruments and outside reference.

These things can be practiced with a simulator, however, unless you have a Level D simulator (full motion) there is little opportunity for false vestibular input, and there is little benefit. Besides, nothing beats pulling 1.5Gs and hearing the wind pick up, and sensing the sunshine moving around in the cockpit to get a student's interest up prior to opening their eyes to begin the recovery.

So the best answer to practice is to have your CFI provide frequent, varied, and sometimes stressful opportunities. In my experience, I have never had a student who could not master recoveries, even with nausea inducing preludes.


Why are parking brakes not used for parking jetliners? From the question 'Do I Set the Parking Brake On the Ramp?' it is concluded that you do not set the parking brake when parking the aircraft.

The question concerns small aircraft which can be parked for a longer period of time. However, commercial jets (jetliners) are also parked at the gate without the parking brake engaged and rely on blocks/chocks placed around the wheels.

Then why is it called the "parking brake" as it is not used while parking the aircraft? Other wheeled vehicles like cars, trucks and buses are always parked on the parking brake.

Parking brakes are used by commercial aircraft at the gate if the ground crew can not set the chocks. The most common time for this to happen is during a lightning storm when ground crews are not allowed on the ramp. Large airports like DFW have automatic parking lights that will guide the aircraft to the proper alignment and stopping point. The crew will then set the parking brake before deplaning the passengers. Some crews will also use the parking brake for ramp holds, de-icing, etc.

The reason why chocks are preferred over the parking brake, is due to the way parking brakes work on aircraft. On commercial aircraft, the pilots apply the brake manually, then turn on the parking brake, which closes a hydraulic valve trapping the pressurized fluid in the brakes. Due to internal leakage of the valve, the brake pressure will slowly bleed down over a few hours. Therefore, after a few hours the brakes will no longer hold the aircraft. Further, most aircraft ramps are slightly sloped away from the terminal, so the aircraft would end up rolling backwards. Due to the bleed down issues, most airlines require pilots to stay in the cockpit ready to apply brakes until the wheel are chocked.

I have personally seen cases of large aircraft being parked with a parking brake, that rolled after the brake bleed down. In one case, a 777 rolled backwards and the jet-bridge tore off its door. Link to News Article

Car parking brakes work differently. Parking brakes in cars have a direct mechanical linkage (typically a cable) that is held in place. Therefore, they do not have the bleed down issue and will maintain the same amount of braking force at all times.


What are the layers of a pressurized fuselage (cross-section and construction)? I've looked all over this site, and also Web searches - but I can't seem to find any discussion about, and the construction cross-section of, a commercial airliner's pressurized fuselage wall.  Not the cross-section of the whole cabin, but just the fuselage wall from inside the cabin to outside.

More specifically, I'm curious as to what layer (and where in the cross-section) contains the pressurized compartment.  Do the circular ribs (or whatever they're called) contain this layer, or is the outer skin the pressure vessel?

I've already seen the below questions (and their answers), but they deal primarily with cabin/cockpit window construction.

Why is there a hole in one of the layer of an airplane's windows?
Why do airplanes have curved windows?
What materials are plane windows made of?

The pressure hull is the aluminum tube formed by the outer skin and supporting frames which serve to stiffen it.  Within that is a layer of insulation which is fibreglass in a ripstop plastic material envelope made into custom fitted sections clipped into place, then the facia panels that create the interior surfaces.  At max pressure differential the hull swells a little bit, maybe a quarter inch in a large airliner.  The primary structure is the outer tube.

A big problem with airliners is warm and very humid interior air (from the passengers) is able to circulate between the facia panels and outer hull and some of this air gets between the insulation batts and the outer skin, which at altitude is really cold so the moisture condenses as frost/drops.  Over time water starts to get absorbed into the insulation.  Airliners can have hundreds of pounds of water in the insulation especially down at the bottom, and at heavy checks the insulation has to be removed and dried out.


what is the highest and lowest air pressure induced by an aircraft at supersonic speeds? When an aircraft is supersonic, is the greatest pressure at the wing leading edge, below the wing surface or in front of the shock wave, or another location all together.

Also is the lowest pressure at the upper wing surface or behind the shock wave or another location all together?

Is there a pressure range for these values just to give a point of reference?

When an airplane goes supersonic, it creates a shock wave in front of it. The shock wave slows the air down to subsonic speeds, so the airplane sort of creates it's own cocoon of subsonic air to fly in.

When the air comes through the shock wave, it's speed reduces to below supersonic, and the pressure increases. The highest pressure is found behind the shock wave, in a stagnation point, a point where the speed is reduced to zero, like on the leading edge. The lowest pressure is usually found before the shock wave, this is the normal atmospheric pressure.

There are 3 types of shock waves:
https://en.wikipedia.org/wiki/Shock_wave
- the normal shock wave:
https://en.wikipedia.org/wiki/Normal_shock_tables
They have nice tables where you can see the speed, pressure and density behind the wave.
- Oblique shock waves:
https://en.wikipedia.org/wiki/Oblique_shock
These shock waves are called strong when the mach number after the wave is below 1, and weak when the speed after the wave is still supersonic.

NASA has some nice programs to show how different types of shock waves are formed and how they interact, you can find them here:
https://www.grc.nasa.gov/WWW/K-12/airplane/oblique.html


Why was pitch angle protection not active in the CRJ 200 during the crash of Sweden Air 294? I have read about the CRJ 200 Sweden Air 294 crash. I understood that the main cause of the accident was faulty IRU and wrong declutter PFD design. The human error also lead the aircraft into a catastrophic condition by not having good communication between the pilot and FO about a miscompared reading of PFD. But some questions are still buzzing my mind. The questions are below:

Is there any pitch angle protection in the flight control system of a CRJ 200?
Did the aircraft fly using autopilot when the miscompare happened? If yes, what is the reference attitude for the autopilot?
If the aircraft used autopilot, so when the pilot tried to push the yoke to pitch down the aircraft, did the aural alert of disconnecting the autopilot alarm the crew that the aircraft is in level off condition (not pitching up steeply). Also, did the CRJ 200 also use breakout force of yoke to disconnect the autopilot?

I am intimately familiar with that incident.  The airplane only had FDR recording the left PFD so they don't really know what was showing on the right one based on FDR.

The only pitch angle protection is the shaker/pusher. They didn't get that slow.
The AP runs off the Flight Director it's selected to.  This is normally the FD of the pilot flying.The  autopilot kicks off when the pitch attitude exceeds a certain angle (I forget what it is).  The capt was PF so the AP would have been coupled to the left flight director.
There is no yoke force mechanism for disconnecting the AP.  If the autopilot was in Pitch Mode and the PFD suddenly goes nose up it'll drive the elevator and follow up with trim inputs to keep the A/P servo loads in limits.  But in any case the AP will be in ALT Mode, the mode you are in once you capture and are holding an altitude.  It pitches to hold the altitude.  If the pitch indication goes nose up, but the altitude is not changing, it won't kick off until the pitch attitude exceeds the auto-disconnect attitude. Until then the AP will be holding whatever pitch attitude keeps the selected altitude.

The scenario was, the capt was sitting there, it's black outside, like black black, up and down, no lights anywhere.  He noticed his own PFD going "blue" (all sky).  Either he kicked the AP off or it would have kicked itself off when that PFD exceeded the auto kickoff attitude.  The airplane is just sitting there minding its own business in level cruise still.

Read the report here.  Capt panics and goes into tunnel-vision mode, and thinks they are in a zoom climb so he shoves the stick forward, putting them into a "bunt" (negative G pushover) in the pitch-black-in-every-direction sky.  The FO, (it was assumed his PFD was functioning normally but there was no FDR for it) would meanwhile have seen all brown on his PFD by this time (and on the Standby Attitude Indicator, but I don't think they ever looked at it).

So there you are as copilot: capt is all confused and has you both hanging in your straps with speed building and crazy roll attitudes to boot.  Your PFD shows all brown - diving.  It's black outside, everything that was on the floor is on the ceiling, and neither of you has a horizon; left side is all blue with the high pitch chevrons and display de-clutter happening, and the right side is all brown with the low pitch chevrons and de-clutter.  The noise is building to a crazy roar and with no horizon (all blue left and all brown right) it's hard to tell where the wings are relative to the horizon.  They both became hopelessly disoriented.

The did several rolls on the way down and hit the ground close to Mach.  There were no large pieces.

In my opinion there was a basic breakdown of a fundamental IFR skill.  When the Capt's PFD went weird, with no physical sensation to match, and no altitude and speed deviations to match, the FIRST reaction should be to do nothing, and cross check with the opposite PFD and the Standby ATT.  It's a case of the old saying, "Don't just do something, sit there".  Seeing the right PFD and the Standby working normally and the airplane's behaviour agreeing with what they showed, the capt should have transferred the AP to the right FD and made the copilot the Pilot Flying, turned off that display, and they would've carried on their merry way.

So bottom line is if the Capt had done nothing, they'd have been fine.  Even once the AP auto-disengaged due to the erroneous pitch attitude, the airplane itself would have continued level flight as trimmed.


How can pilots obtain runway length information for airports that do not appear in the chart supplement? How can pilots obtain official runway length information for airports that do not appear in the chart supplement such as private airports?

If an airport does not appear in the Chart Supplement, the only official information about it seems to be in the relevant Sectional Chart.

In the case of Horseshoe Acres (FA24), the sectional shows that the longest (and only) hard-surface runway is "18", which means 1770 to 1869 feet.

In the case of Brady Ranch (80FD), the sectional shows that the longest (and only) hard-surface runway is "46", which means 4570 to 4669 feet.

Note that you can only guess the runway numbers, the lengths of shorter runways, and the presence of unpaved runways. As @RonBeyer comments, since you have to get permission to land on these fields anyway, it's probably best to ask for such details at the same time. If you get data from the airport operators themselves, that would seem to qualify as official.

However, Airnav and others have lots of consistent data about many airports not in the Chart Supplement, particularly private ones, so it's possible there is some other common source. Since I don't know what that might be, I can't guess how official it is.


Is it allowed to start engines during push-back? Is it allowed, considered safe, and done, to start the engines while the aircraft is moving under the push-back power? On one hand it seems like a big time saving, on the other hand the running engines are rather dangerous and there is still a wing-walker often present during the push back.

It is common. In fact, for aircraft parked at a gate (i.e. not a hardstand), it is quite uncommon NOT to start the first engine during pushback. The wing-walkers stay well away from the intakes, and with the engines at idle power, the danger zone isn't all that large - not nearly as large as if the motor were running at a high power setting.


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How to decide on a rate of climb or descent if no specific vertical speed is required? Obviously, obstacle clearance, charts, atc instructions etc. can require a specific rate of climb or descent, or at least pose limits that are easily calculated. When no such restrictions apply, there appears to be a large amount of freedom in selecting a vertical speed for reaching a certain instructed altitude. Are there standard rates in common use? What (preferably quantifiable) factors help pilots decide how quickly they want to get to their desired altitude?

In general terms, the higher you are the better your fuel efficiency, so you will want to climb quickly and then stay as high as you can until you need to start your descent in order to land.  For jets, a common way to approximate your top of descent is by using the "3:1 rule" where you take your desired altitude loss in thousands of feet and multiply it by three.  For instance if you need to lose 35,000 ft. you would start down 105NM ($\frac{35000ft \times 3NM}{1000ft}$) prior to your destination, staying at altitude until then in order to save fuel.

As far as your rate, the first place I would check would be the AFM of the airplane that you are flying.  Smaller airplanes will have Vy (best rate of climb speed) that may be used for this purpose unless another speed is specified (to help with cooling, etc).  Larger aircraft often have specific climb and descent schedules (for example, climb at 250 KIAS until 10,000 ft then 300 KIAS until you transition to Mach 0.76) which the manufacturer recommends and provides performance information for.  Fly these speeds and take what vertical speed that you get.  Usually, flying by the book is the place to start unless you have a specific reason to do otherwise.

The AIM 4-4-10 says:

  d. When ATC has not used the term “AT PILOT'S DISCRETION” nor imposed any climb or descent restrictions, pilots should initiate climb or descent promptly on acknowledgement of the clearance. Descend or climb at an optimum rate consistent with the operating characteristics of the aircraft to 1,000 feet above or below the assigned altitude, and then attempt to descend or climb at a rate of between 500 and 1,500 fpm until the assigned altitude is reached. If at anytime the pilot is unable to climb or descend at a rate of at least 500 feet a minute, advise ATC. If it is necessary to level off at an intermediate altitude during climb or descent, advise ATC, except when leveling off at 10,000 feet MSL on descent, or 2,500 feet above airport elevation (prior to entering a Class C or Class D surface area), when required for speed reduction.

  NOTE- Leveling off at 10,000 feet MSL on descent or 2,500 feet above airport elevation (prior to entering a Class C or Class D surface area) to comply with 14 CFR Section 91.117 airspeed restrictions is commonplace. Controllers anticipate this action and plan accordingly. Leveling off at any other time on climb or descent may seriously affect air traffic handling by ATC. Consequently, it is imperative that pilots make every effort to fulfill the above expected actions to aid ATC in safely handling and expediting traffic.