How often do commercial flights go-around? I've seen many references here to a flight going around, and YouTube is filled with videos of it happening, but I don't recall ever having been on a commercial flight that had an aborted landing. It might have happened when I flew as a small child, but, having been really, really excited to fly, I think I'd have remembered that.

How often do commercial flights actually abort a landing and have to make another attempt?

I'm primarily curious about US statistics, but non-US would be interesting as well.

As mentioned here:

  Go-arounds occur with an average rate of 1–3 per 1000 approaches.

Most of the videos on YouTube are of go-arounds because of weather. This is not a common scenario as many flights divert to other airports where weather is less severe.


Which are more efficient in putting out wildfires: planes or helicopters? A lake is near where both helicopter and plane can access the water and fire.

Which aircraft (if you had access to only one) is more efficient in putting out wildfires? Which aircraft is preferred to fly for this? What cost less to operate and which aircraft can deliver the most water per load and on the average?

I have added this link below on how this airplane delivers water. Sorry it is longer than 4 minutes. In the video at 4:49 the plane can touch down and refill without stopping.

Both have their respective uses. A fixed-wing carries far more water (3,200 gallons or 12 tons for the Be-200 vs 100-700 gallons for helicopters), but takes more local infrastructure to operate, and is more difficult to discharge exactly where you want it. A helicopter is more precise, but carries less water. A heli is quicker to load up and discharge near the water, but a fixed-wing flies faster, so is better suited to delivering water or a custom mix a longer distance away.

You want both, not just one. You'd use helicopters to suppress smaller fires if possible before they get out of control, attack larger ones at specific spots, and fixed-wings to lay down longer lines of fire retardant against developed wildfires. Larger helicopters also support fixed-wings in this. Which is "better" if you could only have one kind... that's not so much an aviation question as a fire-fighting one.

As for cost, helicopters are normally less cost-effective, being far more expensive to operate per ton-mile. A large aircraft is more expensive in absolute terms. Being smaller and less demanding of the infrastructure, helicopters can be stationed in a more critical location and react more quickly.

It's not a worse/better question, it's tools for the job. Fixed-wing fire-fighting aircraft are more specialized, with their internal water storage, while fire helicopters can be as basic as a light utility heli carrying a water bucket.


Does Boeing use a similar display to Airbus ECAM to view a particular system? Airbus has a dedicated ECAM panel forward of the throttles which is used to select a system for display on the LCD. Is there a similar panel used to select a particular system for display on Boeing's EICAS?

Boeing 777 fuel-system display; A.Katranzhi, CC BY-SA 2.0, via Wikimedia Commons

The following:

747-400 and 747-8
777
787

... display aircraft systems digitally. Except the -400, they also have electronic checklists. For Boeing, it started with the 747-400. The main drive for it was customer demand. After which it was to be like the 757/767, but the "Airbus style" second-generation synoptics was settled on:

One launch customer, Cathy Pacific, originally wanted the standard electromechanical instruments, to avoid retraining. Boeing's initial approach too was "minimum change", but in 1985 other customers, happy with their Airbus and Boeing glass-panelled Efis twins and two-pilot efficiency, pressed for Efis.
(...)
Boeing first responded with the 757/767 flightdeck, keeping the same autopilot. "Minimum change" was still the watch-word. The users' committee became a formal body with chairman and minutes, and the Airbus A320 was now influential.
(...)
The lower Eicas display presents engine data—compressor speeds, oil pressures and temperatures—[and] a major change in Boeing philosophy, [a] systems "synoptics" Airbus style.
— Boeing's two new 400s. FLIGHT INTERNATIONAL, 16 January 1988

Further reading for how it evolved:

Stoll, Harty. "Boeing flight deck design philosophy." (1990). https://ntrs.nasa.gov/citations/19910001624


Why does the PA28 only have one door? I did the majority of my PPL training in a PA28 Warrior and I've recently started transitioning over to a C172 and one thing that amazes me is how convenient it is to have a door either side of the aircraft.

My question is: Why does the PA28 only have one door on the passenger side of the aircraft?

I've never seen the schematics of a PA28 but my assumption might be that there's equipment that runs down the left side of the fuselage preventing a door from being added.

Having one door is just a design preference which makes the aircraft simpler, and lighter to build.

There are many other light aircraft with only one door. Besides Piper, most Mooney, Beechcraft, and Bellanca aircraft only have one door. Even the high wing Cessna 195, 206, P210, 337, and low wing Cessna 310 and 340 have only one door.


What steps do I need to follow to use my PPL for income? So I am currently taking my PPL because flying was always a passion. But, as I am sure all who do such can relate, it is an expensive license to hold on to.
None the less we go through simply for the joy of flying. But I am wondering if we can transform, somehow, or how fast could we, make this investment something we could have as a possible weekend job?
So, what would be the path to take starting from a PPL to be able to fly an airplane and also make a profit out of it?
Thank you all for your experience sharing and patience!

PS: Apologies for missing this one out, countries around Europe, though more specifically UK and Portugal :)

This depends on your jurisdiction a bit since the nuances vary from country to country but in general to get paid to fly (or get paid enough to break even) you need to have at least a commercial pilots license. This would allow you to get paid to fly. With a CPL you can do lots of things like:

Tow banners
Fly charters
Fly cargo
Fly sight seeing flights
Tow gliders (can be done for compensation with a PPL and proper endorsements as well see Rons comment)

What many pilots go on to do if they are only looking for weekend break even fun, is to get their Certified Flight Instructor ticket and teach others to fly. This is a nice way to make some money, fly some beat up planes, and pass along the hobby to others.

The speed to any licenses is hard to predict. It varies based on your time, money and aircraft availability as well as how good of a study you are. You also need to accumulate the hours required for a CPL which can take time. With good weather and a consistently working and free plane you can get through it in months. If you are a weekend warrior and only have access to busy rental planes and live in an area with weather it can take a few years to get everything done.


Why is a part from a Boeing 777 being analysed by Airbus? Since MH370 was a Boeing 777, why are they taking the suspected wing flaperon to Toulouse, France?

Are some spare parts made by Airbus?

Why are they taking the wing to Toulouse, FR?

Because the part was found on the island of Réunion, which is French territory.

  Why is a part from a B777 being analysed by Airbus?

It is not. Airbus is not the only company/institution to have plants/facilities in Toulouse: The BEA (France's equivalent to the NTSB) also has facilities there.


Why can gliders fly for so long? When you throw a paper airplane, it flies for a couple of seconds before losing speed and stalling. With a glider, it has a very long wingspan, but you take off with another plane or winch tow pulling it and then it is released on its own. Shouldn't the glider lose all speed and stall?

A glider and a paper airplane operate on the same principle: Exchanging whatever potential energy (altitude) they have for the kinetic energy (airspeed) required to keep air moving over the wings so they produce lift, giving a stable, controlled descent (glide).
In both cases the airfoil will not stall unless it exceeds its critical angle of attack which is independent of the airspeed. You can continue to fly (with the wing not stalled and producing lift) as long as you still have altitude to trade for that airspeed, and if you do it right you will eventually run out of both altitude and airspeed fairly close to the ground, where you can have a soft landing at a speed where the aircraft is not damaged. In the case of a manned glider hopefully this happens on a runway where you can get another tow plane to take you up again.

Both aircraft can extend their glide time by finding other sources of  lift - thermals, ridge lift, etc. - to carry the vehicle to a higher altitude, providing more potential energy.  Gliders are better at this for one major reason: They have a pilot who can keep the aircraft in an area of rising air longer to gain the most altitude possible.

A paper aircraft can similarly be made to fly for a longer period of time if given an adequate source of lift (equal to or exceeding its minimum sink rate). There's a rather famous video of the "infinity paper plane" which is a paper airplane circling over an electric stovetop, but I'll spoil it for you and tell you that one is a hoax (the general consensus is the plane was on a string).
This one, however, can be replicated fairly easily: The result is more similar to a helicopter in autorotation or an autogyro in a glide than a traditional fixed-wing glider, but it's a good demonstration of the principles involved.


How does keeping the parking brake applied when brake temperatures are high contribute to the dragging brake phenomenon? While going through a presentation on the Airbus WIN application with regard to cost saving practises. It was told with regard to brake life. If the parking brake was applied when the brake temperatures were still high that it can contribute to the dragging brake phenomenon.

Could someone help explain how does this happen ?

From Airbus:

  Why is it not recommended to leave the parking brake ON with hot
  brakes?

  The SOP recommends to set the parking brake brake back to OFF once the
  chocks are in place when the brakes are hot (refer to FCOM for
  temperature values). This is to prevent transmitting heat to the brake
  pistons potentially causing seal degradation, hydraulic fluid
  overheating and generation of a black aggregate, that can reduce the
  piston running clearance and then lead to brake dragging.

(bolded for emphasis)


What's the maximum seat configuration for a 747 that is actually used? I'm curious what model and configuration of the 747 has the most seating capacity actually used somewhere in the world. The Wikipedia page lists "typical" seating, maxing out at 467 (the 747-8). But that list also shows "Exit limits" on the 747-400 as 550 or 660 depending on exit type, and the 747-400 article claims the 747-400 can be configured in a single-class setup with 660 seats (matching that upper exit limit). The 747 article says:

  In Japan, 747s on domestic routes were configured to carry nearly the maximum passenger capacity.

The linked article "isn't available in my region" but a copy viewed via the wayback machine says:

  At the opposite end of the luxury spectrum is what All Nippon and Japan Airlines have done to a few of their 747-400s for high-density domestic routes in Japan.

  They carry nearly 600 passengers in one class.

So, is the 660-seat 747-400 configuration actually used anywhere? Or if not, what's the largest actually used, and what model is it?

The maximum was likely 568 seats.
It is hard to find a definitive source for this, but it is likely that the 747-400D (Domestic) version had the largest number of seats since it was specifically built for this purpose. This type was used by Japan Airlines (JAL) and All Nippon Airways (ANA). JAL published the number of seats they used in a press release:

How many seats in JAL's passenger 747s: We have many configurations for international and domestic airplanes. The latest international route 747-400 has 348 seats - 12 in First Class, 99 in business class and 237 in economy class.
Our domestic Short Range 747s have as many as 568 seats in two classes: 24 seats in the domestic version of First Class, which we call Super Seat, and 544 seats in regular economy class.

(jal.com)
Here is the seat configuration used by JAL:

(image source: simpleflying.com)
I did not find a statement by ANA itself on their seating. The following article however lists 565 seats as their configuration, so 3 less than JAL:

The Boeing 747 – once dominant in the sky is slowly fading away. The latest airline to wave goodbye to the Boeing  747 is All Nippon Airways, who completed the final flights on its domestic routes.
It marks the end of Boeing 747-400s by a Japanese airline – and also the end of an era of the passenger heavy Boeing 747-400D aircraft.
These aircraft had a massive passenger load of 565 seats on a plane.

(economyclassandbeyond.boardingarea.com)
While not impossible, it is unlikely that another airline would have ever operated a 747 with a higher seating capacity.


Why does a Phugoid occur? How can it be eliminated? My model aircraft seems to do phugoid oscillations and I'm having trouble landing. It is around 2 kilos, very high mounted wing, so bad landing takes out the underbelly everytime.

I'm wondering what's causing the phugoid, CG placement? The extremely high wing causing pitch oscillations due to inertia? Insufficient tail?

How can I solve this? I cannot change the wing configuration, but I can change CG along the fuselage length / modify tail.

Edit: More detail - design:

Move the center of gravity forward

What you experience looks almost like a phygoid motion (well, most of it is a phygoid), but involves stalling at the low-speed part of the cycle, so it is not the classical Eigenmode.

Rather, your aircraft's trim point is beyond its stall angle of attack. It will, therefore, stall when not actively steered towards a lower angle of attack and then, when lift on the wing diminishes and its center moves backwards while lift on the tail is still linear, the aircraft will pitch down and pick up speed again.

Maybe it will be already enough to change the setting on your elevator to a few degrees more trailing-edge-down deflection. What certainly will help is to move the center of gravity forward because this will increase static stability and require more trailing-edge-up elevator deflection to maintain the same trim point.

From your sketch I would also guess that your tail volume* is on the low end. Move the tail further back by lengthening the fuselage: This will increase stability and, especially, damping, so the pitch motion after stall becomes less violent.

*  This is the area of the horizontal tail surface, multiplied with it's lever arm (distance between center of gravity and the tail's quarter chord point).


What equipment qualifies as FAA-acceptable for providing "Supplemental Oxygen"? FAR 91.211 tells us when supplemental oxygen is required, but it's not very specific as to how that oxygen is to be provided. FAR 23.1447 gives some information about installed systems, but I can't find much on FAA requirements if you're using a portable system (cylinder, regulator, and cannula/mask like a Mountain High system).

Are there specific requirements/recommendations regarding portable oxygen equipment for Part 91 General Aviation, or can you just pick up a a medical or welding tank, stick a regulator on it, and pass out masks to your passengers?

An even more important question than how is how much oxygen to take, but there's no specific FAA guidance or regulation on either point. Different aircraft can carry different equipment, and people have different requirements depending on their age, lungs, blood chemistry, whether they smoke, day vs. night etc. The FAA's guide on oxygen equipment for GA use is extremely limited and although it describes a range of equipment types it doesn't mention any specific requirements.

Having said that, the 'usual' approach seems to be to use a pulse oximeter to measure your oxygen saturation and if it's too low then go on oxygen immediately, regardless of altitude or other considerations. The moderator of AOPA's medical forum is an AME and he recommends oxygen use any time your saturation level drops below 90%, which is apparently also the required level in hospitals for a patient to make an "informed" - i.e. clearheaded - decision.

But returning to the question of equipment, there aren't any regulations on this at all, so provided that the equipment is safe to use in the aircraft (including not obstructing exits and so on) and not illegal under any other law that might apply (carriage of dangerous goods or whatever) then you can go for it. But the usual 'always act as if you'll have to justify your decisions to the FAA tomorrow' advice applies here, IMO, and personally I would always go with an aviation-specific setup if I needed one.


How can I calculate polar curve? I recently got the polar curve of an aircraft with the method of Anderson. But this method is too old.

Does someone know a recent method for the polar curve without using CFD?

Here are some other methods (excluding CFD and computational ones) for building up a polar curve:

Wind tunnel testing, one of the earliest methods, still one of the most applied and explored one.
Flight testing ("dynamically scaled" model or a 1:1 real prototype)
Empirical methods (e.g. Hoerner's books on "Lift" and "Drag")
Reverse calculations; i.e. if the performance charts AND the engine deck (force model) is published or known, then the flight performance chapter of the aircraft operations manual could be used, at least to a certain confidence level, to guess about the polar curve for different configurations and conditions.
If you know a few speeds of best endurance/best range glide, you could get an idea of the CL/CD at those speeds, and if you know the mass of the aircraft, the polar curve can be plotted.
Asking the manufacturer certainly could help (if not a model of commercial competition)


How are different parts of airliners handled after the end of life-cycle? When I was young my father opened a ship equipment shop. He purchased the broken airliners wheel and resell to the ship operators as anti-crash barrier on ship or in the pier like in the picture.

How does the other parts in airliners be used after life cycle?

Various parts of the airliners face different fates once it has been decided to breakup the aircraft. Most of the parts are reused in one way or the another. The dismantling of the aircraft starts after removal of hazardous liquids and radioactive components.

Engines- Usually, the aircraft and engines will be at different stages of their lives. The engines are removed and sold for operating in other aircraft. In case the engine life is also considered over, either its components will be used for spare parts or it too will be scrapped for materials.

Source: jalopnik.com

Avionics- The avionics components are usually valuable and are removed for use in other aircraft. Since they are line replaceable units anyway, this should pose no problem.

Stripped down cockpit of 747-400; Image from aviationweek.com

Interior- The interior of the aircraft, like the seats, entertainment systems are stripped and sold off. Items in the galley (like coffee makers), the air-conditioning systems also face the same fate.

Stripped cabin of 747-400; Image from aviationweek.com

Some items like the APU, actuators, landing gear, pipings, etc, if they have life are removed and sold for use in other aircraft (after appropriate checks and certification).
In case the aircraft has removable winglets, they are removed as well, for re-use.
Any hazardous materials like composites, depleted Uranium (used as counterweights in 747s, 727s etc.) are removed and disposed off.
The aircraft (structure) is then cut to pieces and metal parts are melted and reforged for reuse in industries, with unusable parts finding its way to landfill.

Source: tarmacaerosave.aero

The following figure from ICAO report Aircraft End-of-Life: Scrapping and Recycling shows how the materials are reused.

Image from What's new in aircraft materials recycling? ICAO workshop presentation

In general, stripping down and recycling of aircraft involves millions of dollars and is highly efficient, with over 90% reuse of materials being quoted. It remains to bee seen what happens to material reclamation as more and more aircraft components are made from composites.


Why hasn't there ever been a large 4-engine commercial airplane with 2 engines on the wings and 2 engines at the tail? This question refers to large passenger jet aircraft only, which I define as being able to carry at least 100 people.

There have been many 2-, 3-, and 4-engined planes in this category. Some of the twinjets have both engines on the wings. Other twinjets have them both at the tail. Some trijets have all engines at the tail, and other trijets have 2 on the wings and 1 at the tail.

But most quadjets (again, only 100+ passenger jet airplanes) put all of them on the wings. Why not put 2 on the wings and 2 at the tail?

Such a configuration would save weight on the wings, because the wings wouldn't need to be so strong to support 2 outboard engines far away from the fuselage. If twinjets can be configured with both engines at the tail, then I see no reason why a quadjet cannot.

In fact, I know of one old quadjet that put all engines at the tail---the Ilyushin Il-62. So I do not think balancing the center of mass and center of pressure is a problem. Some trijets put all engines at the tail, whereas what I'm talking about would only put 2 engines at the tail (and 2 on the wings).

So is this a good idea? Why not do it this way?

EDIT: It was pointed out that exhaust from the wing engines would interfere with the rear engines. If so, then can't we borrow the trijet design for the intake? A large intake at the vertical stabilizer splits in half and feeds both rear engines.

Such a configuration would save weight on the wings, because the wings wouldn't need to be so strong to support 2 outboard engines far away from the fuselage.

You seem to be under the impression that the fuselage supports the wings. The reality is the other way around (in flight, at least.) The wings are the most efficient place to hang weight, as they are what is providing most of the lift. This is why the main fuel tanks are usually located in the wings, for example. The strength required to support an outboard engine while the plane is sitting on the ground should be relatively small compared to the strength required for the wings to support the weight of the entire fuselage (including your proposed tail-mounted engines.) Aircraft with tail mounted engines actually need a heavier wing spar, not a lighter one.

It's also important to note that aircraft with 4 engines nowadays are usually very large aircraft with very large engines, such as the 747-8 and A380. Engines of this size would be very difficult to mount from the tail, especially with the modern high-bypass turbofans and their enormous diameters. Think of a GEnx with 2.8 m / 111 inch diameter fan, for example. This would require strengthening the fuselage as well as the wing spars and would also wreak havoc on the center of gravity. Having twin tail-mounted engines would also probably require converting the plane into a T-tail, which causes yet more engineering problems for an aircraft that large. The bending moments on the engine mounts would be enormous, too.

Can you imagine this hanging from the side of the fuselage? Note the size of the engine compared to the size of the van parked beside it.

GEnx hanging from a 787 wing Source: Wikipedia

It is usually only much smaller aircraft that have had tail-mounted engines. This is done largely to allow them to keep the wings low to the ground. For larger aircraft, there's usually already enough clearance under the wing to mount the engines anyway or, at least, the increase in wing clearance needed to wing-mount the engines is not as much as would be needed in a smaller aircraft. Of course, for high-wing airplanes, clearance is also not an issue and most of these do indeed wing-mount the engines, even on small regional jets. For example, the Avro RJ-100:

SWISS Avro RJ-100 with wing-mounted engines Source: Wikipedia

The question Why do large aircraft have their engines mostly on the wings, while smaller ones tend to have them in the tail or the tip? provides more detail on this. As usual, Peter's answer is informative and there are other good answers, too.


How do I calculate the landing weight in this situation? Empty weight 538kg
Pilot and passengers are 150kg with full fuel tanks

If we use 2 US gallons for taxi and 10 US gallons for the trip, what will be our landing weight?

Fuel Capacity

Total Fuel Quantity:  24.5 US gal. (93.0 liters)
Usable Fuel: 24.0 US gal. (91.0 liters)
Unusable Fuel: 0.5 US gal. (2.0 liters)

First calculate your weight on the ramp:

$$
\mathrm{Empty~Weight} + \mathrm{Crew} + \mathrm{Fuel} = \mathrm{Ramp~Weight}\\
538\, \mathrm{kg} + 150\, \mathrm{kg} + 93\, \mathrm{L} \cdot \Bigg[\frac{0.72\, \mathrm{kg}}{\mathrm{L}}\Bigg] = 754.96\, \mathrm{kg}
$$

During Taxi, you said 2 gallons of fuel will be used:
$$
\mathrm{Ramp~Weight} - \mathrm{Taxi~Fuel} = \mathrm{Takeoff~Weight}\\
754.96\, \mathrm{kg} - 2\, \mathrm{gal} \cdot \Bigg[\frac{2.72\, \mathrm{kg}}{\mathrm{gal}}\Bigg] = 749.52\, \mathrm{kg}
$$

Then subtract the weight of the fuel that will be used on the trip:
$$
\mathrm{Takeoff~Weight} - \mathrm{Trip~Fuel} = \mathrm{Landing~Weight}\\
749.52\, \mathrm{kg} - 10\, \mathrm{gal} \cdot \Bigg[\frac{2.72\, \mathrm{kg}}{\mathrm{gal}}\Bigg]= 722.32\, \mathrm{kg}$$

(Source of conversions)


Antennas on airliner wings? From the question about sharp pods under airliner wings, I think the right term is anti-shock bodies, or flap actuators/track fairings.

What's the little antenna looking thing extending off the rear end of it? My best guess it something anti-static? Why are they necessary?

I should add that this is an American Airlines Airbus 321.

You're very right. It's a static discharger or "static wick", and it is used to dissipate the static electricity accumulated during flight. The electrical buildup happens during flight through precipitation, clouds, dust, etc., and is known as "precipitation static".

Once the static reaches a certain point, it will discharge. Without wicks, this happens through antennae and can really mess with communications or navigation. Wicks make sure that process doesn't cause problems.


Why does a steady-state non-zero body yaw and/ or roll rate induce side force? An answer on ASE states

The presence of steady-state non-zero body yaw and roll rate induces side force ($C_{y_p}$ and $C_{y_r}$).

What is a non-mathematical explanation of why this is so?
Is it correct to say that the side force components described above would exist even if the body were somehow following the same trajectory, and experiencing the same yaw and roll rotation rates, in a vacuum?  I.e., that they do not directly stem from aerodynamic effects?
Also, do the sideforce components created by a non-zero body yaw and/ or roll rate depend upon at what physical location on the aircraft we are measuring the sideforce, i.e. upon exactly where the slip-skid ball (inclinometer) is located?  If so, might there be a location where the measured sideforce resulting from the yaw and/or roll rate is zero even though the aircraft is yawing and/or rolling?

Let's say we have a thin, straight and rigid stick traveling in a 2D circular path. We will attach our reference of frame to the CG of the stick, aligned with its natural forward. If it has a forward speed of $u$ and the circular path has a radius of curvature of $R$, then it has a yaw rate, $\dot{\psi}=u/R$, all of which are expressed in the said reference frame.

At locations forward or aft of the CG, different parts of the stick will experience different lateral speeds due to the yaw rate, when measured using our reference frame: $u(x) = \dot{\psi}x$. The intuition is that the stick is spinning, so top and bottom will experience the largest speed while the centre will have none.
If you had attached a fin near the of the stick, then it will experience a side airspeed, effectively giving it an aerodynamic incidence angle. As a result, there will be aerodynamic forces and moments, simply from the motion of rotation.
From an analysis perspective, we usually don't re-calculate the effects on every surface due to local speed changes. Instead, the stability derivatives are measured in the body axis (well, usually in the stability axis but easily transformed to the body axis). So we can easily lump the sum of the aerodynamic effects of the individual portions into a single derivative with respect to the rate of rotation about that axis.


What is the history of the aircraft logbook? I need to know when the mandate to maintain a logbook started. Was it a US requirement, or was it from another regulator in the world? Did the aircraft logbook start at the same time as the pilot logbook?

Similar to several other terms (e.g. port and starboard), the logging formats came from the shipping industry. Ship used to have detailed logs about their voyages.

Smithsonian states in an article:

  In a logbook from 1913, a pilot penned on one page the date of a
  flight, airplane used, passenger’s name, time aloft, and course flown.
  On the opposite page, he recorded height achieved, distance, weather,
  and remarks.

The above-mentioned article also tells:

  The Wright brothers kept detailed notebooks, recording dispassionately
  the results of their experiments in building the first airplane.

In the US, pilots are required to document their flights in logbooks (14 CFR 61.51). I doubt that logbooks would be optional anywhere in the world. In fact, if you do not log your flight, it is your loss more than anyone else's.


What's the purpose of this red marking on the fuselage of a Boeing 737? I was watching some aircraft today and noticed a red marking on two of them.

What is that? I've seen that marking on many other aircraft.

@SMSvonderTann is correct. The marking is there for warning ground personnel about engine hazrd. In this photo (of a 737) you can see 'INGESTION HAZARD' written above the line.

Image from airliners.net

In this image it is possible to zoom in to see it much more clearly. Note that this marking is not found in all 737s. The danger area is marked with two lines- one in forward fuselage and another in the engine, as can be seen in @mins photo, which I've put below.

Image from airlinereporter.com

Also, as @mins notes, the lines in 747 are for equipment positioning (to prevent damage to fairing, looks like)


What effect does the Space Shuttle have on the Shuttle Carrier 747 I saw a picture of this the other day and it got me thinking... How does having the shuttle on the back of the 747 affect the factors of flight? My guess is that is provides an incredible amount of additional drag and obviously weight. What I'm really wondering is do the wings of the shuttle provide some sort of additional lift to the entire aircraft?

@fooot beat me to it in the comments but the linked podcast answers all your questions

The shuttle effected lots of factors of flight, in quick summary (from the info in the podcast) the whole assembly was:

...aerodynamics not neutral as is answered in this question
...Speed limited due to the braces that held the shuttle on
...VFR only due to the fact that impacting rain could cause water build up issues in the heat shield tiles
...Altitude limited
...Bank angle limited
...Quite short range by default
...Required the orbiter to be empty (although hypergolic fuels were left onboard. All payloads had to be removed if the orbiter was returning something.
...Required rib re-enforcements where the braces were mounted
...Was quite noisy due to the brackets used to hold the orbiter on


How can I get flight destination from ADS-B? If I have aircraft details such as the callsign, transponder code, and ads-b info, how can I look up the departure and arrival airdrome? Is there an API to obtain this information in a programmatic way? How does flightradar24, for example, obtain this data?

If you have the call sign, or Air Carrier flight number, you can track flights with http://flightaware.com. Air Carriers are required to file IFR flight plans so the destination is in the system and trackable. Part 91 (general aviation) and Part 135 (non-scheduled for hire) IFR flights also file a flight plan and their origin and destination are trackable. Most Part 135 flights are on an IFR flight plan but most Part 91 flights are not. However, Operators can block the release of information so FlightAware may not have the info for some aircraft. The information is also available if Part 91 fliers are receiving flight following. If a Part 91 operator is not in contact with ATC the information will not appear in FlightAware.

FlightAware gets the info from the FAA, so there must be an API for it but I don’t know anything about it. “Flightradar24 has a network of more than 3,000 ADS-B receivers around the world that receives plane and flight information from aircraft with ADS-B transponders and sends this information to our servers.” It also gets data directly from the FAA radar with a 5 minute delay.


How can I know DME distance? When I fly 12000ft, how can I know a distance from DME station?
Is there any formula to know or measure distance from DEM?

If your radio has DME installed, then it is shown on the instruments


Did every X-15 pilot become weightless when flying into the upper strato- and mesosphere? The North American X-15 was aimed at breaking airspeed and altitude records. The flights that sought to achieve new airspeed records (Mach 5+) were rather leveled but the flights into the upper stratosphere, into the mesosphere and into space were parabolae. Since all of them were parabolic flights, was the pilot always weightless at peak altitude even during the flights that didn't surpass the 50 mi space border? In the stratosphere I think it depended on the rotational velocity of the plane whether they experienced weightlessness, negative gravity or "just" lower positive gravity after engine shutdown.
The same question also applies to any other high atmosphere parabola-flying plane such as Aleksandr Fedotov's MiG-25 reaching 37,650 metres (123,520 ft), Iven Kincheloe's Bell X-2 reaching 38,491 m (126,283 ft) and the SpaceShipOne and Two reaching sub-space altitudes.

Yes they did. Take away both rocket thrust and wing lift, and the plane goes into free fall. In this condition everything on board becomes weightless.
The pilot would feel only the light bursts of thrust from the small manoeuvring rockets, and the slow return of aerodynamic lift during re-entry.
You don't even need to go into outer space; check out the vomit comets used to train astronauts.


Could an explosive decompression trigger the smoke detectors? In a commercial airliner at FL370, in the event of rapid (explosive) decompression, will the cabin air fog? And can that fog trip smoke detectors?

Pressurized aircraft can have a cabin altitude of 6,000 ft, or so. What is the differential pressure at 37,000 ft? Again, would an explosive decompression of 8-9 PSI, fog the interior environment?

In an explosive decompression the cabin air may fog, this is because of rapid cooling causing the moisture in the air to condense. How thick it is and how long it may last depends on a number of factors.

There are two types of smoke detectors, these are optical particle detection devices and ionization devices. Both types are used on commercial aircraft, some detectors have both methods built in.  Ionization devices are tripped by changes in the electrical conductivity of the air flowing through them and are not very sensitive to steam. Optical smoke detectors work on a different principle, detecting light being scattered by particles in the air. Optical devices are susceptible to false readings from moisture, in fact manufacturers of home devices recommend they are installed away from bathrooms to avoid false alarms.

However, airplane certified units are designed and built to a very high standard, the FAA states in the Aviation Maintenance Handbook that requirements for fire protection systems include:

  No false warnings under any flight or ground condition.

So it is very likely that the manufacturers have taken steam into account, after all cabins sometimes fill with steam when the air conditioning has been turned on when if the air is very moist. An extreme example is this flight at Shenzen. That did not set off smoke alarms, and although I've never seen it that bad I have personally been in the cabin when it's noticeably filled with steam and there were no smoke alarms.

So yes, the cabin can fill with steam in an explosive decompression, but it is unlikely - but possible - that the smoke alarms would go off.


What's it like to be a volunteer at the temporary airport set up at Burning Man? I've heard that the Burning Man festival sets up a temporary airport each year for the week of the festival and that it is staffed by volunteers.  What is it like to be a volunteer there?  Do the employees at surrounding airports find dealing with them better or worse than non-volunteer airports?

Update: Previously I asked what it is like to be a "volunteer ATC", but that is not the right terminology. I have broadened the question to be less specific.

I volunteered at the Airport in 2015 and it was a really cool experience.
I only worked one shift as "Night Watch" / "Border Control" which is basically making sure people going to/from the event to the parked airplanes have the proper wristbands and making sure no one tries to sneak in at night. There are a ton of other positions listed on the volunteer website you can read about here: http://airport.burningman.org/us-who-we-are-and-were/volunteer-info/

The volunteer jobs range from logistical stuff like processing passengers, to ramp operations like guiding taxiing traffic, checking arrival documents to actually running the UNICOM and giving weather advisories to local traffic, particularly about what runway/pattern is in use given the current winds.

Many of the positions (especially ramp side jobs) require some familiarity with how the airport operates and my impression was you "worked your way" up to those. Like many things at Burning Man, if you show up, volunteer and contribute you can end up doing some cool stuff.

You can subscribe to the volunteer mailing list by sending a blank email here:
airport-announce+subscribe@burningman.org

If you're curious about pilot experiences flying to/from the event (which is what I think your original question was about) I would subscribe to the aviators discussion list by sending a blank email to this address: aviators-list+subscribe@burningman.org

Both are great resources for getting first hand information about what its like to fly into and volunteer at 88NV


Why is the front section of the Su-30 not aligned with the longitudinal axis of the body? Please take a look at the picture of the Su-30 below. You will notice that the front section of the Su-30, from the nose to the canopy, is not in alignment with the longitudinal axis of the body. The canopy is raised vertically above the extended axis, and the front portion points downward.

In US fighter jets like the F-18 the canopy is not raised vertically above the extended axis and the front portion aligns with the axis from nose to tail.

So why is the front portion of the Su-30 shaped in that manner? Is it to give the Su-30 any advantage over aircraft that do not have such a front portion?

This is not necessarily the best way to look at this airframe;  it is better observed in a 3-view to understand this.

Viewed from the side and top, the main fuselage does not curve down but blends into pancake like lifting body which mates with the wings and empennage of the aircraft; the engines then are slung under the fuselage in a linear pylon which blends into the fuselage at the tail the design is beneficial for several reasons.

Fuel capacity: The Flanker family of aircraft all have very long legs and can carry a lot of gas due to this flattened mid section and makes a good solution for the need to carry a lot of fuel.
Aerodynamically clean: the blended wing/body design offers low drag as well as low wing loading, making the aircraft very maneuverable as a consequence of high drag during high alpha flight.
Stores carriage: blended wing/body offer a lot of ordnance hard points (12 to be exact) for carriage of weapons, fuel tanks, sensors, etc.

The forward action of the fuselage is based upon the the SU-27UB airframe with an aft crew station raised in order to better facilitate flight instruction in the airplane this required raising this section of the fuselage.  The nose and radome appear to droop down but are laid out that way to increase the real estate for a large radar antenna in the nose radome for increased detection ranges.

Like most East Block war machines, the SU-30 is brutally functional, refined only where needed and passed up for utility elsewhere.  While it may appear to 'curve' the fuselage is essentially straight and the engines aligned with the COG.


What are the security measures preventing someone from chartering a 747 and using it to commit a terrorist attack? While most travelers are well familiar with the security measures imposed by conventional airlines, it is unclear how they apply to private aircraft.

Is it possible for a private individual to charter a 747 for private uses? And if so, are there any security measures in place to prevent said private individual from misusing the aircraft?

(hopefully this question won't get me on the no-fly list) :)

I haven't spoken to any terrorists, so the only source I have for this is Bruce Schneier, but apparently, they're hard to pull off. Objectively, this makes sense; if they were easy, there would be more of them.

For the sake of not referencing any actual living or dead person, let's call our supposed terrorist "Hans Gruber". Hans has enough money to charter a 747 and the desire to terrorize someone. How does he go about it?

If he charters the plane himself, takes control of it, and then crashes it into something (the Nakatomi tower, perhaps), and succeeds, then he dies. Surprisingly, I don't know of many people who are (a) willing to commit terror, (b) willing to personally die for their cause, and (c) multimillionaires.
Okay, what if Hans puts up the money but hires someone else to fly?  Well, money comes from somewhere and charter operators tend to remember you when your passenger hijacks and crashes your 747. Suddenly now you have the authorities after you. Plus, there's no guarantee that the person you hired is going to get the job done.
Okay, but what if Hans is the president of a group of shell companies that can funnel money here and there and disguise the source? Sorry, no good there either. The more people who know about your plan, the more likely the NSA knows about it. At some point (and I would guess that point is not very large) more people in the know results in diminishing returns.
Okay, but what about an opponent who has lots of money, enough willing people to pull off the plan, resources to get them in place and provide the proper training, all while disguising the source? A vast conspiracy? Well, yes, those exist. They're called nations, and other nations go to war with them over things like that. But at that point, it's not really terrorism anymore, is it?


How to execute a gear up landing on aircraft with low propeller? On some GA aircraft such as the Piper Malibu, the propeller would touch the ground if the gear was up. How would you land the plane when gear actuators fail?

I would pull out the mixture knob and turn off magnetos, so the propeller is stopped when it touches the ground, but what is the official/best way to do this?

You can assume the propeller is constant-speed.

Not only some, but in fact most GA propeller-driven aircraft have propellers that extend below the bottom of the fuselage. (The only exception that quickly comes to mind is the Cessna Skymaster; I'm sure there are plenty of others.)

Note that the aircraft will have some secondary method of gear extension, such as gravity drop, a manual crank, or a blow-down bottle. But there are still times where the gear cannot be extended and locked.

In this situation, you've got one emergency. Don't make it two emergencies by shutting down your engine. There's an aphorism - "If the gear fails, the insurance company just bought the airplane."1 Without gear, you're going to do some damage: scraped belly, probably tearing off some antennas. The aircraft will already require maintenance; the extra time and cost of an engine teardown is insignificant compared to the increased risk from a higher workload and a landing that the pilot may not have ever practiced before. (The approach with gear up and engine out will be different than that with gear down and engine at idle in a simulated engine failure.) Don't risk your life to save the insurance company money.

Additionally, just stopping the engine isn't sufficient to prevent a teardown. You must also rotate the prop so that it's horizontal, which requires slowing substantially as you pull the mixture to stop it from windmilling, and then using the starter to move the prop.2 You'd need to prevent any substantial contact between the propeller and runway, as Lycoming's Service Bulletin on propstrikes that require inspection and repair (Continental's is similar) includes the situation of

  Any incident, whether or not the engine is operating, where repair of the propeller is necessary

After all of that, there are some best practices:

Declare an emergency. ATC will help you, have equipment ready on the ground, and clear traffic around you - but they need to know about it first.
Use your checklist. An airplane with retractable gear will have an entry for gear failure; follow it. In particular, you'll shut down the electrical system before landing, and probably brace open a door for exit.
Land on a paved surface. Dirt or grass may seem softer, but they aren't as smooth. According to an AOPA flight-training newsletter, "Statistics suggest that putting the airplane on the asphalt is likely to cause less damage to you and your airplane than putting it on the grass."

(1) I've also heard "The insurance company buys the aircraft when you take off; when you land safely, you buy it back."

(2) Or you could do it in the flare - a suggestion so dangerous I include it only for completeness.


How does the advancing wing in a flat spin create nose thrust? Peter's answer to this question leads me to another question.

How does the advancing wing in a flat spin create nose thrust?

I imagine this like some object spinning in a liquid.  I would think that the motion of each wing would only create drag that acts as torque opposing the motion of the spin in the geographic plane of the spin that would tend to make the spin slow down rather than be maintained.

A very good question, considering so many people do not draw the thrust vector for gliders.

The wing generates thrust by converting energy from falling to forward motion.  From scratch building gliders (and reading) one comes to realize that a falling parachute (straight down) only uses drag to reach a constant rate of descent.

A glider, with its center or gravity off set from its center of pressure (including tail!!!) will start to move sideways (glidogenesis) and generate lift with its wing.  This motion, known as "thrust" in this example, uses altitude as fuel and falling as its engine.

Notice both wings may be "thrusting" as it corkscrews down, but the outside wing, with its lower AOA, generates more lift/thrust and much less drag, sustaining the spin.

Once yawing is stopped, the wings equalize, and can be unstalled by lowering angle of attack.


In F-16 the pilot or FLCS , use the rudder to address the adverse yaw effects in direction of roll during an aileron roll? or opposite way? Is the  rudder moving by FBW in direction of roll or in the opposite direction?

I understand that the rudder is used due to the ARI system (ailerons - rudder interconnect), but don't have any idea how much or in what direction it is used throughout the process ?

Adverse yaw from aileron deflection, at roll initiation, is a function of wing span: a longer wing span creates more adverse yaw. And a long wing span is not what an F-16 possesses.

Image source

Its main problem at lower airspeed is creating a roll rate at all with such short wings. Deflecting the rudder may help increasing the roll rate - for a left roll, it would be deflected Trailing Edge Right, creating adverse yaw. Which might or might be compensated by asymmetric aileron deflection, depending on the priorities posed upon the manoeuvres of a fighter aircraft at low speed. Of course, it makes much more sense to deflect the horizontal tail such that it helps in the roll.

At high roll rates, adverse yaw is created by the difference in local angle of attack at left and right aileron. Plus an aeroplane with low wing span will start to nutate: it wants to spin about its rotation axis with the highest moment of inertia, so tends to want to convert roll into pitch from inertial coupling. So high roll rates are a different kettle of fish in aeroplanes with short wing span, with lots of work to do for the fly-by-wire computers.

  In the F-16, is rudder used to arrest the adverse yaw effects...

Most probably not. Adverse yaw from aileron deflection is not a large issue on fighter aircraft.


What equation describes the relation between engine thrust and EPR? What is the formula for engine thrust as a function function of engine pressure ratio (EPR)?

If the EPR is lower than 1, is the engine producing thrust? For example during descent, when the engines are in idle power.

I'm heavily cribbing from Boeing's "Jet Transport Performance Methods" here, so hold on to your seat...

F = m· (V2 – V1)
where m· is the gas flow rate, mass per unit time
V1 is the initial velocity of the gas
V2 is the final velocity of the gas
Let’s re-write equation 3 in a more complete form:
Fnet = [(m·core air + m·fuel) × Vcore exhaust] + (m·fan air × Vfan exhaust) - (m·air × Vairplane)                                       Note that the force is
now called Fnet, for net thrust. What are those terms in
parentheses? The term (m·air × Vairplane)is the momentum per unit
of time of the air being taken into the engine.  The term [(m·core
air + m·fuel) × Vjet exhaust] is the momentum per unit of time of
the gas leaving the core of the engine. Notice that we are now
accounting for the fact that the mass flow of the exhaust is greater
than the mass flow of the inlet, because fuel has been added to the
intake air.  Finally, the term (m·fan air × Vfan exhaust)is the
momentum per unit of time of the air leaving the fan stage of the
engine. The net force, which is the thrust produced by the engine,
is the algebraic sum of these three terms, which is the rate of
change of momentum of the gas as it passes through the engine.
If we considered only the first two terms, the exhaust flow, we would see only the force created at the fan and the exhaust nozzle.
But this is only half of the story, because we must remember that the
flow of the air entering the engine also has momentum and the useful
work that the engine is doing is the difference between the two.

Note that m· is "m-dot." The dot should be over the letter "m" but didn't copy well from the original pdf. I bold-texted the part about force created at the fan and exhaust nozzle, because I think that's what you're measuring with EPR. Again, from the JTPM textbook:

This stands for engine pressure ratio. It’s the ratio of the gas flow
total pressures measured at two specific points: at the entrance to
the exhaust nozzle (station 7) and at the inlet to the fan and
compressor (station 2). EPR is defined simply as:
EPR = Pt7 / Pt2
where Pt2 is the total pressure measured at station 2 Pt7 is the total
pressure measured at station 7

Hope this helps. Just a little math, but I highly recommend the whole book.


How slow could the U-2 fly at 50,000 ft? How slow could the Lockheed U-2 fly at 50,000 ft?

It was surely subsonic as its max speed is 500 mph.

You can find the official speed envelope in this copy of the flight manual from '68 that was recently declassified, looks like at FL500 you are right around 105 Kts indicated (convert using figure 2). Also note on this chart it is set up for 1535 gallons of fuel at T.O. the plane had various load configurations (covered in the manual) that would more than likely have an impact on the number,

(figure 1)

If you want to do the correction to TAS you can use this chart also from the manual

(figure 2)

Interestingly the copy from '58 that was also declassified (and hosted on the CIA website) is missing most of these charts although it does not look like they were ever in there.

At higher altitudes the margin was much smaller right around its cruise speed of 373 kts as one of the interesting aspects of the U-2 is that due to its design it was always in and around the Coffin Corner at altitude. According to this former pilot of the U-2

  When the littler airplane got up to altitude, the margin between the
  climb speed and the critical Mach number and stall became very, very
  minor, and we were looking at plus or minus two-and-a-half knots at
  one particular point in the climb between the climb schedule and
  critical Mach and stall speed so that’s very very small. When we got
  the bigger airplanes, we got up to plus or minus seven-and-a-half
  knots of margin.

This question may also be of interested to you.

NOTE: The above answer is based on currently declassified information about older variants of the U-2. The plane is still in service and has seen more modern variants which include both aerodynamic and power plant changes to the original designs both factors which could effect the above performance data.


How can I find the optimum chord wing length for this wing? This Aviation SE forum looks the perfect place to ask this question: people here usually make maths the root of most solutions and I think this may solve my aerodynamic optimization problem!

I am having a very hard time optimizing the wing size of my rc plane. I already went to the excelent RC GROUPS community but, despite the generous help of many people, this subject got a little more confusing and personal opinions (practical experience) are conflicting.

My question is this: I already have an rc plane (with tail, fuselage...) and I want to optimize the wing size in order to get efficiency and the longer flight time. I already built dozens of rc planes but this time I want to make this one the most efficient as possible.

IMHO to get longer flight time I need to consume the least amount of energy from my lipo battery as possible - so I need to keep my brushless motor running in the slowest RPM possible, consuming less Amps. Having said that, my total plane weight (not considering the wing, of course) is around 300g (summed weight of ESC, servos, 1000kv motor, 11 inch prop, fuselage, tail, receiver and battery). The weight is fixed, 300g. My wingspan is also fixed, 90cm. I cant have a wing longer than that. The wing shape is rectangular (I know elipses would be the better shape but let's fix the wing shape to simplify this discussion).

If everthing is "fixed" so what is the variable? Well, I want to find the optimum chord wing length for this plane which is gonna bring me the highest flight duration.

I am using the CLARK Y airfoil but you can assume any other one you want. I wouldnt like to discuss airfoil, I would like to discuss the size of the chord and how to optimize it.

My experience and lots of study into this subject says that high aspect ratio wing are usually more efficient than low AR. My wingspan is fixed and all other variables are fixed (to make this discussion more specific) except chord.

So my dear friends, I am struggling a lot to find the optimium chord to get the best flight duration. It looks easy but I am almost 2 months trying to get this answer from many different sources and I still cant find a good solution.

PS: I know I could optimize many of my other fixed parameters, but to avoid having this question marked as too broad/global/generic, I really would like to only optimize the wing chord.

PS (2): the plane that I want to optimize the chord is in the image below. The wing that I show on the picture already provides good flight time (around 22 minutes) but I would like to optimize it in order to get better flight time.

You want to fly at the polar point of the lowest energy consumption. If you describe the drag with the usual parabolic equation, you can use the optimum point derived in this answer. It is
$$3\cdot c_{D0} = \frac{c^2_L}{\pi\cdot AR\cdot\epsilon}$$

Induced drag is three times the parasitic or zero-lift drag when you fly at the polar point for minimum energy loss. But the minimum induced drag at a certain speed is also fixed once wingspan and mass are given - you can only mess up by creating a non-elliptic circulation over span, but never get better than this limit.

Now get the zero-lift drag down as much as you can (pick a thin, highly cambered airfoil which produces a high lift coefficient at the given Reynolds number, definitely no Clark Y) and size chord such that this airfoil will work at the optimum lift coefficient.

Note that this will be an iterative process. Picking a chord will influence your aspect ratio and zero-lift drag, so the optimum lift coefficient will be depend on the chosen chord.


What are the two turning tendencies that occur during a steep turn? A question has come up in preparation for a Block exam. what are the two turning tendencies that occur during steep turn? If you know this may you please explain to me, why these tendencies occur.
Cheers !

One of the turning tendencies that occurs during a steep turn is the tendency to over-bank.  This is generally due to the outer wing (wing-up) moving faster thru the air and creating a bit more lift that has to be counter-acted.  A second turning tendency is due to adverse yaw (requiring a bit more rudder during a right hand steep turn).

Here is a link that will help you understand:

aerodynamics of a steep turn


What is the procedure after a missed approach at the destination alternate since alternate fuel does not contain a missed app. at the alternate? I am currently studying the fuel policy planning criteria for ATPL EASA(A) and i just learnt that the alternate fuel does NOT comprise the missed approach at the alternate destination aerodrome; in case of such a situation and without contingency fuel (imagine that is already used during trip), what is the procedure then since that I probably have to use the final reserve fuel? I guess that I should declare an emergency, how would it be declared?

Let's assume you started exactly with ICAO minimum fuel required (as explained in What are the ICAO fuel reserve requirements?):

Taxi fuel Let's assume you used all of it at your departure airport.
Trip fuel Used for the flight to the destination airport.
Contingency fuel Let's assume this was used in a holding pattern at the destination.
Alternate fuel Used for a go around at the destination and the subsequent flight to the alternate airport.
Final reserve Not used yet.
Additional fuel Let's assume you did not take any.

Under these assumptions you would be using the Final reserve fuel for your go around at the alternate airport. At this point you should declare an emergency (see Do I have to declare an emergency if I cut into fuel reserves?) by broadcasting

  MAYDAY, MAYDAY, MAYDAY, FUEL

as explained in What is the correct phraseology for declaring a fuel emergency?. ATC will then assist you to get to any suitable airport as soon as possible.


What’s the setting range altimeters can handle? What’s the setting range altimeters can handle? Is there a standard requiring a certain range for aircraft to be certified? Are there many occasions where a QNH is so high or low that airplanes have problems handling that?

There are actually multiple different answers depending on the specific type of altimeter system and what standard applies.

The stand-alone altimeters in older aircraft and small GA aircraft (panel mounted "steam gauge") are certificated to SAE AS392C, Altimeter, Pressure Actuated Sensitive Type. The specified scale range is "at least 28.1 - 30.99 inches of Hg (946 - 1049 millibars)".

This standard was updated in 2016 to require compliance with SAE AS8009C, Pressure Altitude Systems. Altimeters built to this standard have a specified range of 27.50 - 31.50 inches of Hg (931.3 to 1066.7 mb).

Aircraft with "glass cockpits" use Air Data Computers certificated to SAE AS8002A, AIR DATA COMPUTER - MINIMUM PERFORMANCE STANDARD. Barometric corrected altitude correction is covered by Table 2, which defines a range of 22.00 - 30.98 inches of Hg or 745 - 1049 millibars.


Can a deployable ILS operate in CAT II or CAT III? Can a deployable ILS operate in CAT II or CAT III? As far as I know a deployable ILS can operate only in CAT I.

This article only states Cat 1.  Deployable ILS project has been ongoing for 7+ years, so -1 to you for not posting anything relevant about it in your question.

The D-ILS is to provide a system of equal performance to existing Category I fixed-based systems that provide aircraft guidance on final approach in low-visibility and low-ceiling weather conditions.

https://www.militaryaerospace.com/articles/print/volume-27/issue-11/rf-microwave/thales-developing-deployable-instrument-landing-system-for-air-force.html
March 2010 article on expected May 2010 Request For Proposal release:

The final RFP is anticipated to be out in May with source selection in June, and an award by December. Initial operational capability is scheduled to occur in early 2013.

http://www.aero-news.net/index.cfm?do=main.textpost&id=c873f7b8-2dd6-408f-9da2-b85f5b36a7ea
Here is another that says it is available in a transportable configuration and says it can do Cat II.  Is it available?  I don't know, the AF seems to be buying the Thales version currently.

Transportable and permanent configurations
Meets icao cat II ILS specifications
For Ground Controlled Approach (gca) operations, the ILS provides
controllers with par-like displays for up to four aircraft. All ILS glide slope
and localizer signal parameters comply with icao Annex 10 standards
for Category II ils, including accuracy, integrity, displacement sensitivity,
clearance, alignment, modulation and frequency. The fixed-based ILS has
been approved by the faa for use in the National Airspace System.

http://www.anpc.com/wp-content/uploads/2011/08/ILS-ANPC.pdf


Is it okay to purposely stall a small single-engine aircraft just before touch down to get a good flare? I'm still learning ground theory and have only flown in simulators (P3D v3 Academic). For a long time, I've been trying to properly flare single engine aircraft but have mostly failed. I even watched a video on youtube made by a certain flight instructor that said that the smaller airplanes like a Cessna 172 and Mooney acclaim don't flare - they "transition" just to make sure the rear gears touch down first.

However, I recently invented/discovered a trick that let me get a nice flared touch down while flying one of these aircraft (in P3D): as I approached the runway, I had the nose pointed down (or straight, as required) but as I was about to reach the threshold, with my speed somewhere around 50 knots, I reduced the speed (sometimes almost pulling the throttle to IDLE) and pitched up. In that condition, the airplane would tend to fall rather than go up and since the aircraft's height is just around 20 - 50 FT, the impact, I thought, would not be fatal.

However, I realized that I was essentially stalling the aircraft (purposely) and I even got a stall warning (though it obviously lasted for about 3 secs). And note: since I'm saying "STALL", I mean to say that the aircraft does cover some (significant) horizontal distance stalling before touching down. I know it's obvious to let the airplane sink a little by synchronizing the thrust and pitch but what i am talking about here is essentially something like a "flared approach", a nose-up approach like what usually jet airliners do.

As far as I know, a stall situation is usually a bad one. However, I was thinking that it might be okay if the pilot knew what he/she was doing and still had control while purposely stalling the aircraft. But I'm confused since I haven't flown a real bird yet.

So, my question is, is it okay to stall a small aircraft for the sake of a good flare?

"To get a good flare".  Never heard of pilots talking about "wow, I had a great flare on that landing!", although a very famous test pilot really had a beauty landing the XF-92A, reducing landing speed from around 160 to 67 mph.

So why do we flare?  What is a flare?

"Flaring"  is increasing AOA to MAINTAIN lift as the plane slows down.

Why do we slow down as much as possible before landing?

Too fast and the plane will "bounce". Bouncing is not a major problem if it is on the main gear (and not too hard).  Bouncing the nose gear can be disasterous.  Since you have a lower AOA for the same lift when faster, risk of bouncing the nose gear is greater.  For taildragger, the risk is prop strike.

So you flare to increase AOA after rounding out and prior to touchdown, reducing speed and increasing AOA.

Do you need to stall to get a good flare?  NO!

Does the stall warning mean I'm stalled?  Try it at altitude first.  Generally they are set a few knots ABOVE stall, and it is normal to hear it as you touch down.  Know your plane.

Finally, "round out" at approach speed (you don't want to stall here), then reduce throttle and pitch up (flare).  The trick is to hold it a few feet off the runway as speed decreases and AOA increases.  You are now flaring!

Actually landing, well, everyone has their own ideas.  In a 172, I could just start to feel the seat of my pants drop.  At that point, back pressure on the yolk was relaxed just a tiny bit (slightly reducing AOA and lift), and the plane would settle onto the runway.

Flaring as all about speed control.  Keep it safe.


Having declared a mental health condition in the past, how will this affect my plans to work as a pilot, and what should I do about it now? About a year and a half ago I moved into an apartment, where pets are not permitted. In order to be able to bring my pet with me, I applied online and obtained an "Emotional Support Animal" letter that in effect, states that my mental health is such that I am unable to live without the animal. This obliged the landlord to permit me to bring the cat with me.

The pet did provide with me emotional support during a difficult time in my life but in retrospect having it declared an emotional support animal was probably not the correct treatment but I couldn't get the building to accept me any other way. Now I'm concerned that this letter is going to be my downfall. I've never been treated or medicated for anxiety or depression, never actually met or spoke to the therapist that issued the letter. I know I have to declare mental health treatment on my medxpress form before my AME... What should I do about this ESA letter?

If this letter keeps me from flying I may never forgive myself.  I figure my best bet is to call AOPA and speak to someone in their Medical department and to schedule a consultation with an AME. I would appreciate any advice.

This answer is inspired by best-practices in dealing with immigration officers.

I shall not dance around your feelings.  You picked the right industry to tell that lie, because the airline industry in particular is extremely familiar with fraudulent "support animals" - people slapping a vest on Fido to sneak them where pets do not belong.  The airlines have struggled with this and its consequences, and the FAA is certainly well aware of it.

Simply Tell The Truth about your mental health.  Which is to say, tell the truth now.

But you can't tell the truth if you don't know what is is. At extremes, stating a fact you don't know is lying, because you imply that you know it.

The form asks if you were diagnosed with a mental disorder.  Note those words.

The origin of the question on the matter is the "doctor"'s letter.  Review it.  If it plainly claims "diagnosis" and "mental disorder", then that is that: you must tick "yes". However if it is ambiguous on the point, then you don't know -- you should ask the "doctor" for clarification. I would write them and say you are applying for an ATP license, and ask them a) Did you diagnose me?  If so was the diagnosis of a mental disorder in the meaning of this form (attached)?

And the doctor will write you back and state definitively a) whether it was a diagnosis and b) whether it was of a mental disorder or other reportable thing on that form.  She will surely give you the most helpful answer possible within her medical ethics. You may rely on that because she is a licensed professional.  There may be an ethical issue there, but that's between her and her medical board: not your problem.

"Ah, but she can't recant the diagnosis since she's not a bona-fide doctor!"  Well then, she also was incapable of issuing a diagnosis, so you were not diagnosed after all.

If FAA asks about the contradiction between your FAA claim and your support animal letter, show them this second letter.  Of course they will suspect your goal was to cheat your landlord, but that does not violate any FAA regulations (except perhaps the "morals" rule, but therein, they are concerned about serious arcs of behavior that indicate disrespect for the duties of pilot, e.g. lying to FAA about mental health, not lying to landlord about a cat).


Are there international standards to Air Traffic Control procedures similar to US standands? In regards to air traffic control, FAA Order 7110.65 is the standard for policy and procedure in the USA. Do other countries use this also?

Is there an 'international standard' for air traffic control? If so, are there any notable differences between that and the service provided by U.S. FAA?

ICAO Annex 11 "Air Traffic Services" is probably the top document. Implementations in national law might vary.


What is this c. 1930 beautiful monoplane seen in Oakland? Photo from Denny Wright's album.  He piloted for
Clyde Sunderland.  This photo has no stamp or markings. Anyone recognize this aircraft?

(wikimedia.org)

It looks like the Lockheed Model 8 Sirius, or a variant of it.

First flight was 1929, and 15 were built.

  Two versions of the same basic design were built for the United States Air Force, one made largely of wood with a fixed landing gear, and one with a metal skin and retractable landing gear, designated Y1C-25 and Y1C-23, respectively. Its basic role was intended to be as a utility transport.


How reliable are aircraft cutaway drawings from Flightglobal? I am working on a new system that would be retrofitted on jets (can't talk much about it yet), and I was looking for detailed drawings to start creating its detailed engineering design.

I stumbled upon this website, does any of you know how reliable Flightglobal and those drawings are / where they get their information? Your opinion would help a lot.

Thanks!

These cutaways are just general representations of what structural components go into the aircraft; they are NOT engineering drawings nor should they be used as such.

In general the OEMs and the engineering departments for the airlines are pretty sensitive about releasing engineering data for proprietary reasons.  If you are working on a product closely with an OEM or an airline, they may be able to grant you a license to access such data, generally for a substantial fee. Or, if you have a client who will allow you access to the aircraft, you may be able to take engineering photos and/or make detailed measurements directly on the aircraft.


Why are both ATC and TCAS tasked to prevent collisions although TCAS takes precedence anyway? « The primary purpose of ATC worldwide is to prevent collisions
  [...] Many aircraft also have collision avoidance systems, which
  provide additional safety by warning pilots when other aircraft get
  too close. » (source)

Why is ATC tasked to prevent collisions, when for this specific purpose aircraft already have "collision avoidance systems" on board, which even take precedence over ATC in case of conflict ?

This may look like an apparent contradiction to laymen.

I presume that there are several reasons for this, including:

Because not all aircraft are TCAS-equipped.
Because ATC ensures separation minima (although TCAS could be extended to enforce separation).

Which other reasons are there ?

While ATC's primary goal is to prevent collisions, it is also responsible for the efficient movement of aircraft through the airspace. That requires a strategic approach to managing air traffic to get aircraft from point A to point B safely and in a timely manner. The primary tool ATC uses is the flight clearance.

If air crews follow their clearances accurately and VFR traffic maitains adequate visual separation, there won't be any problems with separation being met.

TCAS can't issue a flight clearance. It doesn't know anything more than the traffic it can track via Mode C or Mode S interrogations. It's a tactical system that provides a backup when ATC or the crew makes a mistake and separation is lost. In this case, the TCAS is the automatic backup to resolve the loss of separation and avoid the collision.

The reason a TCAS RA must be followed, taking precedence over ATC, is that when there is a loss of separation immediate action must be taken.


What is timed approach? I have tried to find what timed approach is, but I cannot find any reference to it. Could you let me know what it is and when it is used?

I had never heard of this or seen an approach with a holding fix at the FAF or outer marker when I ran across a question on timed approaches from a holding fix in Gardner’s Complete Advanced Pilot. As you can see from the quotes at the bottom of the post, it is unlikely to ever be used. But they are still available to the controller, FAA Order JO 7110.65W Air Traffic Control.

FAA_H_8083-15B Instrument Flying Handbook 2012

Timed approaches from a holding fix are conducted when many aircraft are waiting for an approach clearance. Although the controller does not specifically state “timed approaches are in progress,” the assigning of a time to depart the FAF inbound (nonprecision approach), or the outer marker or fix used in lieu of the outer marker inbound (precision approach), indicates that timed approach procedures are being utilized.

In lieu of holding, the controller may use radar vectors to the final approach course to establish a distance between aircraft that ensures the appropriate time sequence between the FAF and outer marker or fix used in lieu of the outer marker and the airport. Each pilot in the approach sequence is given advance notice of the time they should leave the holding point on approach to the airport. When a time to leave the holding point is received, the pilot should adjust the flightpath in order to leave the fix as closely as possible to the designated time.

Timed approaches may be conducted when the following conditions are met:

A control tower is in operation at the airport where the approaches are conducted.
Direct communications are maintained between the pilot and the Center or approach controller until the pilot is instructed to contact the tower.
If more than one MAP is available, none require a course reversal.
If only one MAP is available, the following conditions are met:

a) Course reversal is not required; and

b) Reported ceiling and visibility are equal to or greater than the highest prescribed circling minimums for the IAP.
When cleared for the approach, pilots should not execute a procedure turn.

The actual order specifies that Timed approaches using either nonradar procedures or radar vectors to the final approach course may be used at airports served by a tower if the following conditions are met and goes on to give similar conditions.

The AIM has an example of how they might be used.

The sons of the guys who wrote that procedure are now in the “Old Controllers’ Home”, I can only guess at their intent. The last time I had to run timed approaches was when I was taking non-radar problems to certify on Denver Sector 26 (COS/PUB low) in 1968! R Butler – ATC Controller

We did some timed approaches when I worked a U.S. non-radar approach control in the ’80s. Don’t believe there are any non-radar approach controls left, and I don’t know a single radar controller who would try it if there were a radar outage of some sort. We also had to run them at the FAA Academy in training back in the ’70s. You would need to assign different missed approaches to succeeding aircraft, so #2 doesn’t catch #1 on the miss.

It’s a lot of radio and brain work to do successfully. Non-radar at a radar facility, (because of an outage) is usually very limited now. (One in, one out) Backup radar systems preferred, even if not as accurate. vector4fun


Why is True Altitude calculated using the difference from the QNH to 1013hPa? I have an example for true altitude calculation.
The given Information is
QNH: 983hPa, cruise in FL 85, ISA -10°C in this Alt.

The math and calculations are not hard and i also get to the correct result, but my Question lies in understanding the principles.

So to get the height difference from my QNH (MSL) and 1013hPa i simply take the difference of 30hPa x 30ft. and get 900ft. of seperation.

Now to the Question: Why is it correct to calculate the difference from the QNH, so actually a "virtual pressure", to a true temperature corrected pressure level of 1013hPa?
Wouldn't i need to calculate it from the actual temperature corrected pressure at MSL?

Because it is preferable to work with standard atmospheric data,(ISA international standard atmosphere where at mean sea level, the temperature is 15° and the pressure is 1013hPa)

and because your navigation instruments will display your altitude with respect to a reference, on QNH setting, above the transition altitude the reference is MANDATORILY the mean sea level pressure of 1013 hPa

However it is possible to set your instrument with respect to the field elevation(QFE) so that at landing your displayed altitude is zero.

Airfield QNH is obtained by correcting a measured QFE to sea level using ISA regardless of the temperature structure of the atmosphere. As your altimeter is calibrated using ISA, it will indicate altitude correctly at the airfield reference point. At other altitudes, the indicated altitude is likely to be in error, depending on the temperature of the atmosphere.

All altimeters are based on ISA, notwithstanding instrument error, altitude readouts between aircraft will be similar, whether flying colder than ISA or at higher temperature than ISA, the most important matter is that above the transition altitude you must be on QNH ISA condition(reference:1013 hPa) to insure height separation between aircrafts.


What is a rudder or fin stall? What is a rudder or fin stall, how will the aircraft behave in that situation, and how should the pilot recognise it? What is the recovery procedure? And what is rudder reversal?

Right side slip from left rudder, rudder stalls, what happens?

This is comparable to a wing stalling in that it is caused by the rudder/vertical stabilizer
exceeding a critical angle of attack.  There for, it has passed its maximum deflection potential.  The result will be the fuselage slip will reduce until the rudder/vertical stabilizer assembly unstalls.  Just like with the wing and elevator, reducing rudder deflection will also unstall it.

Notice designers have learned 3 techniques to help prevent this:  1.  Lower aspect ratio vertical stabilizer. Just like wings, these stall at higher AOA.  2.  Swept or delta shaped leading edge.  Many 1940s era Vstabs were fantasticly ahead of their time had their planforms been made into wings.  These shapes will stall at higher AOA, allowing greater rudder deflection.  3. The all moving rudder.  Making the entire assembly a rudder (as on the SR-71 Blackbird) and making them large enough will help over come the directional stabilizing effect of the rear fuselage when turning.

Rudder stalling would most likely involve some fairly aggressive control application, which may exceed the structural strength of the vertical stabilizer.  Beyond fighters, there may not be much benefit in that type of manuever.


How are airspace fixes named? Aircraft use nav fixes as waypoints or reporting points along their routes. I have noticed some interesting combinations.

Some make sense, like LUCKI to LYNDI on the LYNDI arrival into San Diego International, known as Lindbergh Field, or KSINO LUXOR on the GRNPA arrival into Las Vegas.

Some are more interesting, like HIMOM KALME on the FRNCH arrival into Denver, or ASTAH LVSTA ADYOS on the ADYOS departure from Albuquerque.

Some get downright suspicious, like ITUNE MUSCC DWNLD on the LOWBO arrival into Albuquerque.

So my question is: how do these points get named? These combinations are memorable, but are they also allowed to be sponsored? Or is this a case of "Any resemblance to actual entities is entirely coincidental."

In the US, they are assigned by a division in the FAA called Aeronautical Information Management (AIM), per FAA Order JO 7400.2J (Procedures for Handling Airspace Matter), section 3-3-2:

  a. Service area office are responsible for assigning and changing names of NAVAID and aeronautical facilities, and must follow the instructions contained
  herein and in FAAO JO 7350.8, Location Identifiers, Chapter 1.

  b. AIM is responsible for issuing five−letter names for radio fixes, waypoints, marker beacons, and compass locators. Five−letter names must be issued by AIM to the Terminal Procedures and Charting Group, Major Military Commands (MAJCOM) and Air Route Traffic Control Centers (ARTCC) for future assignments.

It's conceivable they accept suggestions from ARTCCs or other entities. I don't know. I doubt paid sponsorship is approved but have no first hand knowledge there. Suggestions are probably casual and intormal.

They are often quite amusing, like ITAWT ITAWA PUDYE TTATT. Very often enroute fixes are named for small towns or other points of interest near the fix.


How much jurisdiction does the FAA have over military aircraft? The FAA controls just about everything about civilian aircraft in US airspace in terms of regulation, certification, flight rules, etc. Do they have any authority over military aircraft beyond requiring military flights to communicate with ATC for safety and designating certain areas as military airspace?

This question addresses retired military aircraft in civilian use, and one of the answers to this question mentions a "Surplus military" category, but nothing about active military.  I'm asking about current, active military aircraft in terms of certification, pilot licensing/qualification, etc.

If they are being operated by the military, not much. Military operations can exempt themselves from the FARs (as a matter of practice they don't: When operating in the US National Airspace System they follow the same operational regulations we do, but as a matter of regulation they're subject to the military's rules for airworthiness, maintenance, etc.).

Military pilots have a military pilot's license (which can be converted to an FAA license with a little paperwork), and the airworthiness and maintenance standards for active military aircraft are defined and managed by the branch of the service responsible for the aircraft. (This is similar to, but legislatively distinct from, Public Aircraft Operations.)

This doesn't mean the FAA is completely silent about military operations/aircraft: There is guidance for military aircraft that are based on commercial designs (also available in an easier-to-read Advisory Circular: AC 20-169), which would be applicable to aircraft like the VC-25 ("Air Force One").


Can an airplane lift off the ground when lift is equal to weight? Can a plane lift off the ground at the point when there is the same amount of lift as weight? Or does lift have to be greater?

Yes they can, in fact aircraft regularly lift off the ground when lift is less than weight. They achieve this by rotating the nose, which provides a vertical component of the thrust vector. See the excellent answers to  this question for a detailed explanation.


Why did the flight Osaka -> Frankfurt circle above the airport after taking off from Osaka International? When departing form Osaka International (KIX) the Osaka city passed below twice, the second time much lower. Looks like our 747-400 was circling up in spiral before heading a long way over Russia to Europe.

I understand the reason of flying in circles before landing (holding pattern, waiting in a queue for landing). But why circle over the airport of departure? I think it could be more economical and faster to pick the altitude while heading in a needed direction. Is there also a queue to leave the airport? Why not to wait on the ground then?

If was the flight LH741 (Osaka - Frankfurt), departing 24.10.2017, 10:00 from Terminal 1.

Looking at FlightAware, we see this takeoff for your flight:

Examining some airport charts for KIX, this looks like the standard departure NANKO REVERSAL THREE DEPARTURE from runway 06R.

I guess that the loop is to give the aircraft enough time to climb to 8000 before it reaches NANKO. And, I guess the 8000 feet is for either terrain or noise abatement (notice the climbing loop is entirely over water.)


What would non-potable water be used for on an airliner? Airliners have potable water tanks and distribution systems for galley functions and such; of course, this water is used for any non-potable functions as well as it's what's available on a modern airliner.

However, this question makes me wonder if there are water uses on an airliner that could be served by a separate non-potable water system, or if all the water needed is potable.  If there are non-potable water uses, what would they be?

Aircraft travel in countries were pathogen bacteria or viruses are carried by insects which like to lay their eggs in stagnant water. Aircraft water systems must be designed carefully to prevent spreading diseases.

On a typical airliner like the Boeing 737NG, you won't find any non-potable water source that would contain chemically untreated water. Equipment is fed from the potable water tank. Used water is either dumped overboard or stored. From the aircraft familiarization manual, the water system:

and the toilet waste system:

Condensation water is a by-product of many systems cooling air (including by expanding it). This water is collected and drained overboard. Jet engines (including APU) are the main generators of water, as fuel combustion generates essentially water (in mass) and CO2.

It's worth noting that at cruise altitude, moisture in atmosphere can be insufficient for humans well-being. The water extractors present in air-conditioning packs then reincorporates a part of extracted water into conditioned air.


Approximately what percentage of aircraft are equipped with RNAV? I was hoping someone could provide me with an estimate of what percentage of aircraft are equipped for RNAV (Area Navigation). I'm more interested in commercial aircraft, but business and general aviation would be nice to know too.

This is for my own curiosity, so speculation is perfectly fine.

Use of RNAV began in late 1960’s . Some airlines began exploring RNAV systems

KLM/SwissAir/SAS/UTA had a cooperative effort
Swissair became responsible for the development of a database to
support this effort

In June 1973, National Air DC-10 equipped with Collins ANS-70 conducted RNAV operation, including approaches in VMC, with database.

In January 1983, the Federal Aviation Administration revoked all RNAV routes in the contiguous United States due to findings that aircraft were using inertial navigation systems rather than the ground-based beacons, and so cost-benefit analysis was not in favor of maintaining the RNAV routes system.

RNAV was reintroduced after the large-scale introduction of satellite navigation.And, since 1990 it is there in almost all the planes you see.
So, as a rough estimate it would be more than 90%. Because, most of the pre-1990 planes have either been upgraded or grounded.

Sources: Wikipedia, Federal Register, This Article.


Is ADS-C used in practice? Both the FAA and the EASA have decided against using ADS-C in the development of NextGen and SESAR, because of cost, scalability and ease of use. But has ADS-C actually been implemented and used in practice anywhere?

ADS-C is used in oceanic environments, for example over the Atlantic and the Pacific.

FL350 to FL390 on the North Atlantic Track System is restricted to ADS-C equipped aircraft. Non ADS-C aircraft have to fly either below or above those levels (crossing through those levels is permitted)

The text below is a part of today's Norht Atantic Track message issued by Shanwick Center (EGGX):

  222021 EGGXZOZX

  (NAT-2/2 TRACKS FLS 310/390 INCLUSIVE

  MAR 23/1130Z TO MAR 23/1900Z

  PART TWO OF TWO PARTS-

  E MALOT 53/20 53/30 53/40 53/50 RIKAL

  EAST LVLS NIL

  WEST LVLS 310 320 330 340 350 360 370 380 390

  EUR RTS WEST NIL

  NAR NIL-

  F LIMRI 52/20 52/30 52/40 52/50 TUDEP

  EAST LVLS NIL

  WEST LVLS 310 320 330 340 350 360 370 380 390

  EUR RTS WEST NIL

  NAR NIL-

  REMARKS.

  TMI IS 082 AND OPERATORS ARE REMINDED TO INCLUDE THE

  TMI NUMBER AS PART OF THE OCEANIC CLEARANCE READ BACK.

  2. ADS-C AND CPDLC MANDATED OTS ARE AS FOLLOWS

  TRACK A 350 360 370 380 390

  TRACK B 350 360 370 380 390

  TRACK C 350 360 370 380 390

  TRACK D 350 360 370 380 390

  TRACK E 350 360 370 380 390

  TRACK F 350 360 370 380 390

  END OF ADS-C AND CPDLC MANDATED OTS


How to keep an aircraft stationary with an inoperative parking brake? After High Speed Rejected T/O and an imminent evacuation, how would a pilot keep the airplane stationary with an INOPERATIVE parking brake?

Keep pushing hard on the wheel brakes... And hope those do work, obviously.

If there's soggy ground next to the runway, let the aircraft roll onto that and the wheels should bog down into the mud.

There's precious little else you can do unless you want to deliberate drive the aircraft into something solid.


Why can’t aircraft use GPS to generate the IAS, instead of using pitot tubes? I’m mostly asking after reading about Aeroperu Flight 603, which was caused by a piece of tape blocking the sensor. Is there any other way to gather IAS or is this the best way to do it?

To answer the other part of your question, in a scenario where you lose all 3 speed indications, you are left with pitch and power.  If you know the airplane really well and are sufficiently skilled at flying, this should be enough.

For example if you've been flying some jet for a while you will know that at Vref on a 3 degree glide slope flaps and gear down you will have an fan RPM range of say 60% at lighter weights and 65% at max landing weight.  So when on the glide slope you just hold the pitch attitude that keeps you on slope and keep the power there and the speed will take care of itself, within reason.

Same if you're just flying around in level flight.  Just holding the pitch attitude and setting power at the value you're used to will keep your speed somewhere in the ballpark.  In fact, at the extremes, it's quite easy to tell the difference between 250 kt and 330 kt just from the sound (the roar at Vmo is unmistakable).

On a descent at idle, you'll know from experience that the pitch attitude is, say, 15 degrees below the horizon at 200 kt.   So you just fly the attitudes you know will work, with power that's appropriate to the speed range you want, and you'll be close enough not to fall out of the sky.

On top of that, the manufacturers all provide pitch/power setting tables in their QRH procedures that can be used to maintain speeds close enough to avoid falling from the sky (fallout from some of the clear-air pitot icing incidents).

I know personally of an Atlantic Southeast Airlines CRJ crew that lost all 3 airspeed inputs from ice crystals, used their pitch/power skills to manage things on decent until they got their speed indications back when they were lower.  But they would have had no problem landing the plane with no airspeed if it came to that, and that was before there were QRH pitch/power tables.

The Aeroperu guys were unfortunate in that they went into brain-lock and became disoriented in the darkness.


What are the disadvantages (if any) of using a supercritical airfoil? The title sums up my question pretty well.

I've searched all over this site, having read many of the questions and answers to various supercritical wing topics, but I haven't found any mention of disadvantages to using them.

Are there any?

A supercritical airfoil has these characteristics:

Large leading edge radius
Comparably flat upper surface
Rounded lower surface with a maximum thickness location at around 50%
Flat or even negative camber in the forward section
High positive camber in the rear section (rear loading)

The large leading edge radius allows it to create more lift than comparable airfoils at high angle of attack. After R. Whitcomb re-invented supercritical airfoils (they had first be developed by K. A. Kawalki in Germany in 1940, and British airfoil research resulted in similar shapes, first used in the VC-10), he transferred some of their characteristics to a GA airfoil, the GA(W)-1.

From the Wikipedia article on Whitcomb:

  The unusual airfoil unexpectedly aided general aviation as well; its
  rather blunt leading edge allowed it to generate high lift
  coefficients before stalling, and Whitcomb published a low-speed
  airfoil which he called GA(W)-1; it is now routinely used in light
  aircraft and gliders.

As usual, Wikipedia is mostly correct, but the use of the GA(W)-1 on gliders is everything but routine. This gives an indication of their drawbacks:

The low forward camber limits the range of the laminar bucket to lower lift coefficients. A good glider airfoil tries to maintain the laminar bucket almost up to stall.
A positive camber throughout will produce higher maximum lift coefficients than what a supercritical airfoil is capable of. That is why the GA(W)-1 uses only the blunt nose and the rear loading, but not the camber distribution of supercritical airfoils.
The high rear loading gives them a large, negative pitch coefficient which translates into a larger travel of the center of pressure over angle of attack, requiring a larger horizontal tail. In airliners this does not matter because their large flaps dictate the size of the tail.