What are MTRs used for? Ok, before you say, "Military Training Routes are used for... uhh... military training," let me elaborate.

I've read about how they work with ATC and speed restrictions etc. What I'm wondering is what they do on them.

Take, for instance, IR-504. It starts in the middle of nowhere about 20 miles south of the BUM vortac in western Missouri, almost 70 miles from the nearest Air Force Base. It takes numerous turns and meanders, seemingly randomly all over northeastern Kansas. It finally ends in an MOA in the middle of the state, but once again, not by a base or anything.

I can't see any rhyme or reason to the routing and can't imagine what it would be used to train for. It's not bombing practice; only a very small section is inside an MOA. It can't be terrain following exercises; its an IFR route and 3 digits means over 1500ft agl. Besides, what terrain could they be following? We're talking about central Kansas here.

What in the world do they use these routes for?

There is a description of this route page 1-139 of "Area Planning, MTR".

The scan is not good, you may get the textual content here too.

It says terrain following activities may take place, as well as visual contours (which I assume to be navigating without radar, looking at the outdoor and searching in a catalog the same relief contour to know where you are). As you commented, taking into account the local relief:

For terrain following should be for newbies.
For visual contours navigation should be for top-guns only.

There are different routes like this, starting from nowhere and ending in the Smoky MOA. They seem to be routes avoiding nearby airfields. On the image below, I've emphasized the area without airfields, including MOAs. It looks like IR-504 is drawn along the centerline.

Based on VFRMAP

Other possible selection criteria:

Unpopulated areas (noise from low flying jets)
Low radio noise areas.
Flat terrain for UAV training.


What is the usual range of Approach and En Route ATC VHF radios? I was wondering what is the regular range of Approach VHF radios used by ATC (normally 50W)? And what about En Route VHF radios (usually 100 or 250W)?

VHF radios are line-of-sight, and typically the range is limited not by the transmit power but by terrain and the aircraft's horizon. PPL students are taught a rule of thumb: the range in nautical miles is the square root of 1.5 times the aircraft's altitude in feet. This makes your range roughly 40 nm at 1000 ft, 90 nm at 5000 ft, and 120 nm at 10000 ft.

En-route stations intended to be used over a wide area will typically use several transmitters on high ground many miles apart, to ensure reception over their whole operating area. Even so, low-level flying can put you into a blind spot between transmitters.


What’s that weird sound during spool up on some aircraft? Some engines seem to make this characteristic “wailing” noise when spooling up. A good example of such is from 0:50 to 0:54 in the following video:

               . I’ve also heard it on a300s, 767s, and md-11s. Does anyone know the source of this noise and why it only occurs with certain engines?

That noise is almost exclusive to turbo fan engines.  If the air is right, turbo shaft engines can do it.
  On sudden and high power changes the big fan on the front is spinning at a different speed than the motor compressor.  Since the front fan is also the first couple of stages of the engine compressor, the air doesn't move cleanly between the two when they are not at the same speed, and make that sound.
The Navy S-3 made the same sound on power changes so it got the nickname Hoover.
@Rob,if you are close enough to it you can feel it.


What should I wash my plane with? What should I wash my airplane off with?  As a new aircraft owner, any help would be appreciated.

I am pretty sure using dish washing detergent is not the best here as we are told not to use the stuff on our cars.

You should wash your aircraft in accordance with the manufacturer's instructions.

We could all offer opinions and product recommendations in response to this question. However, the best answer is: in accordance with the manufacturer's instructions. Since you ask the question generically, without any information on what aircraft you might have, I will answer generically.

Your manufacturer's instructions can generally be found in at least two places: the owner's manual/AFM and the maintenance manual. For example, in the owners manual for a 1975 Cessna 172M, you will find Section V: Care of The Airplane containing instructions on how to wash painted surfaces, bare aluminum surfaces, interior surfaces, and the windscreen and windows. The maintenance manual for the same aircraft contains nearly—if not exactly—identical information in chapter 2.

Now, for that aircraft and others, Cessna recommends use of mild detergent in certain applications; you might not find that overly helpful in choosing what to use. Based on my research and experience, and time honored practice that I've observed, Dawn dish soap is widely used for cleaning painted Cessna aircraft with no apparent long term harmful effects. The airframe that I fly for work has tens of thousands of hours on it, and while I cannot vouch for how often it was washed in the past, I try to wash parts of it a few times a week. There is no apparent washing damage to the paint.

I will also highlight Cessna's instruction to use Stoddard solvent on areas of stubborn oil or grease; this can be especially helpful in cleaning the belly with it's typical collection of oil and dirt. My practice is typically to wipe down the belly with solvent first, and then follow with a water and detergent wash.

If the manufacturer's instructions are not clear, or are otherwise insufficient to answer your question regarding your specific aircraft, I would recommend asking your maintenance professional. He or she should have both the knowledge and experience to steer you in the right direction.

For more insight into the world of aircraft cleaning, and especially for the specific product recommendations you want, you might take a look at this AvWeb article by Kim Santerre: Aircraft Cleaning.


At what point during a long flight do commercial airliners have the best gas mileage? This question has several parts that are interrelated, and I didn't want to split it up:

Considering that several tons of fuel are consumed during a long haul flight which requires lift to be reduced as the flight progresses, do pilots do this by changing wing geometry, altitude, speed or all of the above?

Is this done automatically or manually?

What is the optimal strategy if you want to minimize fuel costs?

Having chosen the optimal strategy, is the latest phase of the flight where the airplane weighs least necessarily the one that gets the best gas mileage, or is there a minimum at a certain intermediate airplane mass during the flight?

There are a lot of things that go into determining the most efficient way to operate a jet, and minimizing fuel does not always make it cheaper to operate.  Some general "rules" that are used are:

There is an optimum speed to fly the airplane, which depends on several factors:

Altitude
Fuel savings by flying slower -vs- increased maintenance costs because you are taking longer to get there (and putting more time on the airframe/engines).
Temperature at cruising altitude
Winds at cruising altitude

There is also an optimum altitude to fly the airplane:

Aircraft weight
The higher that you can fly, the better - until you don't have enough power to maintain your optimum speed at the optimum power setting for the engines.
Temperature at cruising altitude
Winds at cruising altitude
Altitudes that are available from ATC
The amount of fuel and time that it takes to climb -vs- the amount of time that you will have at the high speed cruise

Anything that makes the airplane heavier makes it unable to climb as high (and lowers the optimum altitude for the current conditions), and makes it burn more fuel.  This includes the fuel itself.  Assuming a constant speed and constant weather conditions, you will always be more fuel efficient later in the flight.

As fuel gets burned off, the amount of thrust required to maintain the optimum speed goes down and the optimum altitude goes up.  Basically, we keep reducing the power to maintain speed until the optimum altitude increases to an altitude that ATC can let us climb to.  This is known as a step climb.  The speed will be controlled manually by the pilot, or can be controlled automatically by auto throttles.

Today's sophisticated flight planning software takes all of this into account and gives the pilot a very good plan on how to operate the airplane to be the most efficient!


How do i find a supercritical airfoil for my preliminary design? The following information is available but i don't exactly know where to get the information about SC Airfoils from. Do Airbus , Boeing use secret airfoil that they don't disclose?
Cruise Speed = 240 m/s or 0.7 Ma; Chord length = 5.5 meters
Using online tool to get the Reynolds number gives a very high number of about 85 million. Using the standard setting for kinematic viscosity of $1.4207E-5$.
1.How do I find a SC airfoil for a transport jet of about 150 Pa @ 0.7 Ma?
2.Why are my Reynold's number so high? It should be around 25-30 Million.

Answer to the implicit question: Yes, the more recent airliner airfoils are indeed secret. Look for reports like this to see what is out there.
Answer to question 1: Try the linked NASA Technical Paper 2969.
Answer to question 2: Your viscosity is for sea level. Try to use the value for the tropopause and it will be only ⅓ as large.


Why is the manufacturing process of an aircraft mostly manual? Why is the manufacturing process mostly done by humans, and not by robots as in case of most other industries?Video

Although robots have taken over many jobs in the process of manufacturing things like cars, airliners are much larger and more complex. In some ways it has more in common with constructing a building than assembling a vehicle. There is a much larger variety of tasks to be performed over a much larger area.

That being said, many parts of the manufacturing process are completed by robots. For example, Gemcor makes machines that automatically drill aircraft wings and fasten them with rivets and bolts.

Robots are also used in manufacturing large composites. You'll notice how massive these machines are, and they are only completing one task on one component. They are very good at tasks that require one or more of force, repetition, and accuracy.

However, so much of the process is not economical to be done with robots. A robot specializes in one task or one type of task, while humans can do many different tasks. Many tasks involve working in tight spaces, which humans can do better than a large robot. Tasks like installing wires require dexterity as well, which humans are better at.


Is threshold crossing height and glide path angle the same for ALL airports and applied to ALL aircraft? It seems to be agreed (at an international level) that these values are standard and should be respectively 50 ft and 3 degrees. Are all airports following these rules, and are they applied to all type of aircraft?

Why would departure operations not have the same kind of constraints?

In the US, the requirements are specified in FAA Order 8260.3, United States Standard for Terminal Instrument Procedures (TERPS).

Section 2-3 states:

  2-3. General PA Requirements. See Order 8260.19 for requirements
  related to GPA/TCH coincidence.
  a. GPA. Utilize a standard 3-degree
  GPA where possible. GPAs greater than 3 degrees but not more than the
  maximum (table 2-1) are authorized without approval when needed to
  provide obstacle clearance or to meet simultaneous parallel approach
  standards. Other cases or GPAs less than 3 degrees require Flight
  Standards or military authority approval (USAF not applicable).

  b. TCH. The published TCH (nearest whole foot) should accommodate the
  largest aircraft height group normally expected to use the runway and
  must not be less than the minimum or exceed the maximum TCH.   Note:
  60 feet is the maximum TCH regardless of height group.
  (1) CAT I.
  The TCH is based on achieving an acceptable wheel crossing height
  (WCH). The WCH is the difference between the TCH and the approximate
  glidepath antenna-to-wheel height (see table 2-2).
  (a) The optimum
  TCH provides a 30-foot WCH. It must provide a WCH no less than 20 feet
  or greater than 50 feet.
  (b) Displaced Threshold Considerations. The
  TCH over a displaced threshold can result in a WCH of not less than 10
  feet if the height of the glide path over the beginning of the full
  strength runway pavement suitable for landing falls within the
  minimum/maximum TCH values.
  (2) CAT II/III. The optimum TCH is 55
  feet and must be between 50 and 60 feet regardless of height group.

      Note: To determine the
  minimum allowable TCH, add 20 feet to the glidepath-to-wheel height
  and to determine the maximum allowable TCH, add 50 feet to the
  glidepath-to-wheel height (not to exceed 60 feet).

So, the answer to the question is ; No, they are not all 3 degrees and 50 feet.


Could the Aurora D8 have Ramjets instead of traditional jet engines? By the  design of the Aurora D8, the engines would receive the boundary layer of air atop the fuselage, however, because jets have what I am calling "moving parts", and the pressure differences would cause problems for the turbines. Could we eliminate this factor with ramjet engines?

The Aurora D8 doesn't have traditional jet engines at all. The design incorporates a very large bypass fan which due to its size is not mechanically linked to the engine core. It's more like a turbo-prop engine, but driving a ducted fan instead of a propeller. The fan is specifically designed to cope with the flow disturbance in the boundary layer. Indeed, according to the Wikipedia article

  Clustering the engines together atop the wide tail of a flattened fuselage enables them to reenergize the slow-moving boundary layer over the fuselage

Take a look at that article. It might answer a few more of your questions.


How do different RPM–MAP settings affect range? For a cruise in constant-speed prop aircraft, you can choose different combinations of the manifold pressure and prop rpm to generate the same amount of power. For example, in order to generate 117 BHP (65% Rated Power) at sea level in the chart above, you can select either the combination of 24.5 for MAP and 2100 for rpm or that of 22.9 for MAP and 2400 for rpm. Here, what's the difference (if any) in selecting different combinations of rmp and MAP to generate the same power? Any benefits using the combination of low rpm and high MAP or vice versa?

This other post answers my original question, yet I have a follow-up question:

How does the combination of low rpm and high MAP extend the flight range?

To my knowledge, whatever combinations are chosen, as long as the combinations generate the same power, the same amount of fuel is consumed. The above chart supports that: The same 10.3 Gal/Hr is flowed into the engine regardless of the combinations in the box.

For your information, I asked the same question to my instructor, and he told me there's really no difference when it comes to power and fuel efficiency. But I was not persuaded at first, because I thought it was the MAP that controlled power output (BHP), and therefore, the less the MAP, the less fuel required. And a more efficient use of props could supplement this loss of power, resulting in the same thrust power. But the above chart just contradicts my reasoning. According to the chart, it's not the MAP alone but the combination of MAP and rpm that determines the BHP. But if it's the case, I don't understand how the range of flight could be extended by decreasing MAP and increasing rpm.

The advantages of oversquare (MAP > RPM/10) are:

  less vibration, noise, heat, and wear
  longer engine life as a result of this
  much less noise emitted from the engine/propeller
  more efficient cylinder charging and better combustion, gives lower fuel consumption if leaned properly
  less power lost to friction inside the engine

  — Source

Since there are fewer loses to friction and high propeller RPM, the same fuel flow will yield slightly faster flight, and thereby range.

Another article from AVweb that discusses the topic: Why "Over Square" Is Good


How can I be US aircraft maintenance technician? I have only an airframe-related experience of 8 years without a license, but have logbook, my US citizenship in process, and want to become an aircraft technician. How can I become a US aircraft maintenance technician? I have Pakistani aviation experience in airframe/B1.

The FAA has a guide to becoming an aviation mechanic, and the related regulations are in 14 CFR 65 Subpart D. In summary:

Be at least 18 and be able to speak and write English
Have 18 months experience working on airframes or powerplants; or, 30 months experience working on both
Pass three tests: written, oral and practical

The experience requirements are in 65.77 and it doesn't say that you need to have worked in the US. So your experience in Pakistan should be valid, although I have no idea what documentation you need to provide.
If you're inside the US, there's no requirement to be a US citizen, although to work and/or study in the US you need an appropriate visa (or green card). Some employers might require citizenship for specific positions, for security or other reasons.
If you're outside the US, you have to be a citizen or permanent resident, or get special approval per 65.3:

§65.3   Certification of foreign airmen other than flight crewmembers.
A person who is neither a U.S. citizen nor a resident alien is issued
a certificate under subpart D of this part, outside the United States,
only when the Administrator finds that the certificate is needed for
the operation or continued airworthiness of a U.S.-registered civil
aircraft.


What would happen if put a jet engine behind another jet engine? Just curious. Would it do nothing, would it generate a massive amount of thrust? Would it even work?

There is an alternate way to answer your question, and it relates to thermodynamics.

Think about the purpose of a jet engine.  It exists to take uncompressed air, compress it, mix it with fuel, burn it efficiently and then expand it (hopefully adiabatically) to generate a larger volume of gas at higher pressure than the intake.  The work done by the engine is described by the Brayton cycle (Figure 3.13 from http://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node28.html), and this cycle shows us where we can and can't hope to achieve theoretically efficient operation.

If you look at the chart of the cycle in the above reference, you'll note that the compression and exhaustion portions of the cycle are where inefficiency (in the form of entropy) creep in and prevent the cycle from being perfect.  As such, even if there were sufficient oxygen left to burn, putting two jet engines back to back would be horribly inefficient (because you are repeating the inefficient portions of each twice).

The better solution is to work towards improving compression ratios, and recovering more work from expansion.  Much of this has been done over the last 50 years, and is why Brayton efficiencies are in the 0.6 to 0.7 range for modern jet engines (ref same website, Figure 3.19).

EDIT: Also, remember that jet engines are designed to work on air that is "cold" relative to their exhaust. They don't compress hot gases efficiently. You could certainly design a compressor to efficiently compress hot gases for combustion, but jet engine compressor sections are not designed for this, so the compression achieved by the second engine in your question would be MUCH lower than its design, which would further decrease it's contribution of additional thrust.


May a pilot legally fly an ILS approach to ILS minimums with an inoperative Attitude Indicator without declaring an emergency? A seasoned pilot told me the other day that if the vacuum system fails while on final approach leaving the Attitude Indicator (AI) inop, the pilot must use localizer minimums even with both glideslope and localizer needles functioning normally.

Is this accurate, or did I misunderstand?

For the record, the asker changed the question after I answered, specifying that not declaring an emergency is a condition of the question, so I will address this at the top without modifying the original part:

An attitude indicator is legally required for IFR flight.  If equipment becomes inoperative during IFR, the pilot should inform ATC.  I do not know that there is any specific legal text that addresses this particular situation you're describing with an ILS approach coupled with an AI failure, but it would be generally accepted by pilots that losing an attitude indicator is an emergency as opposed to losing other required IFR equipment such as the clock.  So, I'm going to go with no, not without declaring an emergency.

Original:

In that situation depending on the circumstances, declaring a missed approach, an emergency informing ATC of the system failure, and requesting vectors to VMC conditions would be the best option.

In an emergency, you can deviate from rules to meet the needs of the emergency at your discretion, so I don't believe that technically you can't still shoot to minimums for the ILS, but it would be dangerous, especially if the pilot isn't highly proficient, and should be a last resort with no primary gyros.

If an approach needed to be shot, and there was no VMC within range, a 'Precision Approach Radar' approach would likely be the best option if one existed within range.  This is can be a 'no-gyro' approach upon request.


What is the difference between Fly-By and Short-Turn? By all definitions that my team and I have found, fly-by and short-turn (with respect to military unmanned air vehicle waypoint based flight) mean the same thing.  Briefly, this allows the pilot to fly within a capture distance of the waypoint but is not required to fly directly over or through it.  In other words, the pilot can start turning before the waypoint is reached.

Current Definition:
A short turn will be performed at the turn location.  A short turn indicates that the vehicle may begin its turn prior to reaching the waypoint and fly-by it instead of through or over it.

Is there any nuanced difference between these two states so that I might further clarify this in my definition?

The context of your question is a bit unclear, but assuming that you're asking about navigation waypoints in the US then you're probably referring to these terms as defined in the FAA's Pilot/Controller Glossary:

  FLY-BY WAYPOINT- A fly-by waypoint requires the use of turn
  anticipation to avoid overshoot of the next flight segment.

  FLY-OVER WAYPOINT- A fly-over waypoint precludes any turn until the
  waypoint is overflown and is followed by an intercept maneuver of the
  next flight segment.

As per the comments, I have never heard of a "short turn" waypoint and it isn't in the P/CG.


Is it possible for the sensors which determine when an aircraft has landed in water to become damaged? A plane has sensors that should transmit data back somewhere when it hits water correct? Is it possible that these can be turned off/damaged?

Yes, the component in question is called the Underwater Locator Beacon.

They are not foolproof. To disable them manually you need physical access to the black boxes, which are located in the tail section of the plane.


Why are the engines on the MAX and neo prone to bowing? The engines of the 737 MAX$^1$ and Airbus A320neo family$^2$ are [more] prone to bowing (shafts deforming if no debow is applied during start – as I understand it, this happens in a turnaround while the core is still hot).

The debow solution is cold motoring to harmonize the temperatures of the various engine parts. This in turn leads to much longer start durations (was upwards of 7 minutes on the A320neo until a dual-cooling button (shown below) was added to allow the motoring of one while the other was being started, which brought the delay down, but still takes longer than the ceo).

(YouTube)

Operational impact aside, why are those engines prone to bowing? The only other jet-liner I'm aware of that needed a debow procedure was Concorde.

My first thought was the higher overall pressure ratios (OPR) of the new engines, while plausible, Concorde's OPR on ground was nowhere near the levels of the new engines (15.5 vs. 40).

What design element/changes made those engines require the noticeable debowing procedure?

$^1$ http://www.b737.org.uk/737maxdiffs.htm
$^2$ http://aviationweek.com/commercial-aviation/new-pw-president-has-nothing-hide-gtf-starting-issue

Rotor bowing is not unique to this generation of engines. It was an issue with the early IAE V2500. I remember initially they would have somebody manually rotate the fan some time after shutdown. This engine still has a longer start motoring period over the comparable CFM.

The root cause is simply making the shafts thinner, increasing their flexibility. When natural differential cooling occurs, they bow. This is done in the pursuit of weight reduction, which is important as new engines are larger and heavier than before.

The PW1000G is a special case, which is where the majority of the issues are occurring. Because of the fan gearbox, the fan operates at a slower speed than the core. Thus, for the same amount of power, the core will spin faster with less torque. The thickness of the shafts are only dependent on torque and not speed, so Pratt and Whitney was able to thin the shafts significantly and cut weight. Unfortunately, they did not properly account for rotor bowing.


Is this WWI movie scene realistic? In a poignant scene of 1933 WWI film The Eagle and the Hawk (not to be confused with the same-name 1950 western film), while the pilot played by Fredric March performs a loop-the-loop in his – I believe – Airco DH.9 (is that correct?) to evade a German opponent, his observer/gunner falls out of his place and plunges to the ground (he had already been hit and probably killed by the German, but the pilot wasn't aware of it, so this is a real trauma for him).

See the scene here, starting from about 57:25.

Besides the dramatic value of this scene within the narrative, would such a fall as the gunner's be realistic? If those aircraft were capable of such manoeuvres, wouldn't the crew be somehow secured?

A loop is about 3G on the initial pull, declining to maybe half a G over the top, then increasing to 3G on the pull out.  If you go in at the proper entry speed etc and you want to make it reasonably round.  If you release enough back pressure to go even slightly negative over the top, whatever is unsecured falls out (as well as all the crap on the floor coming up into your face, and, if carbureted, the engine quitting momentarily).   All it would take is a little push on the stick while rounding the stop, for whatever reason.

Observers weren't strapped in because they had to be free to move around to do their thing.

So that scene is perfectly plausible.


Can stored/leased 737s be used to substitute for grounded MAXs? The 737 MAX was introduced relatively recently. I would have assumed they were replacing at least some older 737 models in operation with the major airlines that took them (eg Southwest, American, United, in the US). Did those airlines immediately sell off their older planes as the new ones joined their fleet? I see reports of huge flight cancellations from lack of the new aircraft. Since they have common type ratings with the earlier 737, what happened to the older planes that none of them can be pulled from storage or dry leased and put back into service? Surely this grounding is long enough to be worth the transient expense?

It really isn't 1 new aircraft = 1 mothballed aircraft. Most of the 737 MAX aircraft were fleet expansions (for US carriers). The older aircraft get retired when they aren't economical to fly anymore, and even then a retired aircraft is often sold either to a scrap yard or to a lower budget operator. In order to bring an aircraft back into service they may have to go through C or D checks before they can be considered airworthy again (because old aircraft are often retired at a D-Check when it needs a major check).

Airlines need to schedule C/D checks out months in advance, each aircraft costing millions to go through the check and a month or more of downtime. There is only limited space available to do these checks, so even if they wanted to bring 10 aircraft back into service, it may take 6 months and cost $20-40 million. It's cheaper to cancel the flights.


What does performance speed refers to? Aircraft performance in general For example C172R specifications:
Cruise speed:122 knots
What does this mean?
Maximum achievable Indicated airspeed At specific conditions?
Another example - rate of climb: 721 ft/min
For what conditions? So much factors can affect this..

Read the POH - it will show the conditions the speed was measured under.

  Cruise, 75% Power at 8500 Feet. . . . . . . . . . . . . . . . . . 122 KNOTS

  NOTE

  *Speed performance is shown for an airplane equipped with
  speed fairings which increase the speeds by
  approximately 2 knots. There is a corresponding difference
  in range, while all other performance figures are
  unchanged when speed fairings are installed.

  The above performance figures are based on airplane weights at 2450
  pounds, standard atmospheric conditions, level, hard-surfaced dry
  runways and no wind. They are calculated values derived from flight
  tests conducted by Cessna Aircraft Company under carefully
  documented conditions and will vary with individual airplanes and
  numerous factors affecting flight performance.

(http://www.airilm.com/wp-content/uploads/172R-POH.pdf)


Is there a limit to how large an airplane wing can be? There are some agreeably large planes out there, like the C-5 Super Galaxy. But how big can these planes' wings really get?
The heavier the plane, it is usually larger, and with size of the fuselage comes size in the wings (most of the time). But is there a limit to how big you can make your wings?
If you make your wings so big that they're 6 feet thick and an absurd length long, say, for a colossal plane, will those wings provide enough lift? I mean, if the wing gets that big, It not only has to lift the plane, but its own weight then becomes a concern. But, with that weight comes the size. Another issue, is how the aerodynamics work on such a crazy big plane.
The thicker the wing, the more air is contacting the wing. This causes more resistance on the wing at a given chunk than a smaller wing. The question comes from seeing several shows that depict planes so large they're like flying cities, and it just doesn't look realistic to me, the sheer size of those planes.

No, there is no theoretical limit to the size of a wing. You could make a wing big enough to lift the entire Earth (assuming, of course, you somehow had an atmosphere to fly it in).
There are, of course, many practical limitations to wing size. The lift a wing develops is proportional to the square of the scale of the wing, all else being equal. However, the weight of the wing (and the rest of the airplane it's attached to, for that matter) is proportional to the cube of the scale. So, if you double a plane's size, the lift developed by the wings goes up four times, but the weight goes up eight times. So, in that case, the wings would need to be even larger compared to the plane in order to lift the added weight. This is referred to as The Square-Cube Law (Wikipedia, Aerospace Research Central, TVTropes). You eventually reach a point where there are no materials strong enough to withstand the stresses imposed on such a massive wing.


Can anyone identify this biplane from a TV show? Could someone help identify this biplane from a TV show, please? No other scene / camera angle is available though.

My vote would be a Waco UPF-7 without the engine cowl:

Source: American Power Museum
Looks like the one in the OP post has a different engine in it or at least a relocated cooler, but the struts and windscreen design look very similar. (Struts on the right side are distorted by perspective, look at the ones on the left). Gear bracing is also pretty close.


Any info on very strange wing endings on this Stemme glider? Do you have any info on this strange wing endings used on Stemme glider?

Source

This was a test aimed at measuring the effect of feathered wingtips. The Stemme S-10 has a four-part wing, and for the experiment the outer wing panels were removed and replaced by five staggered small wings, as shown on the picture in your question. This reduces wingspan from 23 m to only 11.4 m plus the span of the wingtips, in total maybe 14 m.

A feathered wingtip shows less induced drag than a straight wing of identical span, similar to a winglet, because it can involve a bigger mass of air into the creation of lift. But it cannot perform wonders, the effect is small.

The concept behind this experiment is called "winggrid" and the brainchild of Dr. U. La Roche. See here for one of the few still active sites on the topic - the original site http://www.winggrid.ch has long been abandoned.

Sad fact: This aircraft was destroyed in a mid-air collision in 2007. At that time, it had been reverted to the original wingtips.


Is low pressure compressor air used to cool turbine blades? This photo shows LP cooling air is being used to cool turbine blades. the question is, is it possible to use LP air to cool the turbine blades?

would you please guys explain why do they use LP air with HP air to cool the turbine blades?

Short answer:

Low pressure compressor air can be used for turbine cooling, but usually it can only be used to cool the low pressure turbine. For the HPT, you need cooling air from the HPC. This is because the cooling air must come from a location in the compressor that is a higher pressure than the part of turbine it is cooling, so it will actually flow into that turbine location.

Longer answer:

Cooling air from the compressor is air that the engine has compressed, so put energy into, but doesn’t get the full energy out of, when it enters the turbine as cooling air. So, you want to use as little as possible, and take it from the early stages of the compressor, rather than the back of the compressor, where even more energy has been put into it.

But.... the cooling air has to be taken from a location within the compressor that is a higher pressure than the turbine location which it is cooling, so that it actually flows into the turbine.

Hence, to reduce the parasitic nature of cooling air, the low pressure turbine is generally cooled with air from the early stages of the compressor, but the high pressure turbine must use cooling air from a sufficiently high source, so it usually comes from the last few stages of the high pressure compressor. As explained, this is necessary for the pressures to be favorable to cause the cooling air to flow. However, aside from meaning it is more parasitic towards the engine, there is another disadvantage of having to use high pressure air for cooling. Pressuring the air causes its temperature to increase. So, the “cooling” air from the exit of the high pressure compressor is hotter than cooling air from the start of the HPC. Because of this, sometimes the cooling air is cooled by a heat exchanger in the bypass duct, because the cooling air from the exit of the HPC is actually quite hot.

Why the picture shows both LP and HP air in the same blade:

In the picture you show, the same blade is being cooled by both LP and HP air. This appears to contradict this answer. If one can use cooler LP air, why use the hotter, more parasitic HP air. I found the source of your image, and the text there doesn’t explain this contradiction. But if you look at the two images attached, you can see that the pressure around a turbine blade is not uniform. There are higher pressure regions especially at the front of the blade, while the pressure at the trailing edge is lower. Since you always need your cooling air to have a higher pressure then the static pressure at the location of your outlet, you need high pressure cooling air at the front where the pressure on the blade is high and you can get away with using lower pressure cooling air at the back since the pressure on the blades trailing edge is low.


Do you know the exact model and use of this rotorcraft? I've tried to identify this. Someone suggested it is a Bell 206, possibly a Jet or Long Ranger. I disagree.

I think it is a US Coast Guard helicopter. It flew over my house in Mobile, Alabama. It's been difficult identifying from this angle I photographed it.

It's a Bell TH-57, most likely a TH-57C, which is the Navy's variant of the Bell 206 JetRanger.  It's used for VFR and IFR helicopter primary flight training for the Navy and Marine Corps.  Most likely that picture you took was of a TH-57 out of Pensacola NAS on a training flight.  They like to come out to KBFM and Jack Edwards in Gulf Shores to practice flying, pattern work, etc.


Is it possible to divert a plane to a distant airport? Some years ago I have spotted that an Eurolot flight from Amsterdam to Gdansk, diverted close to final approach to a distant airport on the other side of Poland:

Is this another example of Flightradar24 bug and it is more than possible, that this particular flight actually landed in desired destination airport? Or are there any business or operational rules or some special situation, that would judge diverting a plane to a distant airport, while having at least 5-6 other airports closer "on the track"?

For me -- layman -- the answer is: No, there are no such reasons and airplane is always diverted to the nearest airport, that is able to accept it (taking plane type, weather conditions etc. into account). But, I'd like to get some expert confirmation, if there are no exceptions from this rule of thumb?

EDIT: In my opinion, we're dealing with a quite different situation here than in previous question (and that's why I didn't merged both questions into one). Mainly, because:

flight path IMHO is clearly suggesting a diversion, not an error in Flightradar24 and
plane's vertical speed is suggesting, that plane is actually landing in the moment, this screenshot was captured, and since I was living in Katowice for over 30 years now, I'm pretty sure, that there was not direct flight on AMS->KTW route, neither by Eurlot nor by any other airline and neither at the moment of capturing this screenshot nor right now.

So there actually was no other flight between Amsterdam and Katowice that Flightradar24 could mistakenly taken as this one.

The diversion airport is selected by the captain¹.

If the aircraft needs to divert for some urgent reason like engine failure, smoke/suspected fire/fire, medical emergency and similar, the captain will select the airport so that they can land as soon as possible. However from cruise altitude even expedient descent still takes about 15–30 minutes and the plane can cover 50–100 nmi, so they still have some choice in most places, especially densely populated areas like Europe.

But there are many less urgent reasons that warrant diversion. The most common is of course that the intended destination is closed due to weather, accident or other problem. And then there are problems like pressurization failure that require descent to lower altitude where the fuel consumption is higher, so the plane no longer has enough fuel to reach the original destination, but still has fuel to fly considerable distance.

Sometimes the plane can even reach the intended destination just fine, but some fault occurs that would be hard to fix there, so the plane returns or diverts somewhere it will be easier to fix.

In these cases, the captain calls the airline dispatching (over radio, HF radio or satellite phone) and discusses with them where they should divert to make least disruption to the overall airline operations considering things like ability to fix the diverting plane, availability of replacement plane or alternate connections for the passengers, availability of replacement crew to fly the replacement plane or this plane after it is fixed, availability of airline representatives to take care of the passengers and many other things.

So something happened and for some operational reason it was easier for the airline if they had the plane in Krakow than if they had it in Gdansk (or, if it was not possible to have it in Gdansk, better to have it in Krakow than, say, Warsaw, which was still closer). For example I remember reading about incident where wind shield cracked on a plane already on approach to their destination, Klagenfurt, and they returned to Vienna and sent the passengers by bus. Because it was apparently easier (and cheaper) for the airline than fixing the airplane in Klagenfurt without suitable hangar (with cracked winshield the plane may complete the flight, but not take off again).

¹ Except really special circumstances like violation of foreign airspace and arrest by interceptors, nobody from outside can divert the plane. The pilots do.


Does installing a PTZ dome camera outside the aircraft violate any FAA rules? I want to install a big PTZ camera at the exterior of the plane like A380 which can give the pilot a clear view while landing or taxing.

I have gone through a similar question but it doesn't give any specific answer though. Can I attach a camera to the outside of my aircraft in the USA?

My question is: if its going to be a permanent part of the aircraft and not a GoPro type, can it be included by the Manufacturer themselves?

I am not sure if this kind of exterior object is going to affect the aerodynamics of the plane. I got confused when an aerospace engineer told me it can affect the plane and can create some issues whilst in the air.
I would like to get clarification on this matter.

Aircraft out there already use external cameras for use during taxiing/landing. Airbus uses a system called external and taxiing aid camera system (Etacs) in A380 and A350, which uses three cameras:

One camera in nosewheel well gives a view towards the aircraft’s nose gear.
A second camera mounted on the vertical tail gives a high overview of the aircraft from the tail.
Another camera is situated on the belly of the aircraft for giving views of runway below.

Note that both of these are FAA certified and under operation.

Whether or the camera affects the aircraft performance depends on the aircraft and the camera used (and installation location), though in most cases it shouldn't. In that case, you may have to get a supplementary type certificate


Are there specific mass breakdowns for aircraft? I am interested in the engineering and weights for aircraft around 8,059 lb (3,655 kg) Citation 505) and  18,900 lb (8,570 kg F-16).

Curious about specifically structural mass and landing gear systems. How much can landing gears lift?

I can point you at some reference materials you can use. These methods involve estimates for different types of aircraft and formulas you can use to estimate the component weight based on the MTOW and OEW, for example.

You can use the following books:

Roskam - Airplane design (a series of books)
Egbert Torenbeek - Synthesis of Subsonic Airplane Design
Jane's All the World's Aircraft (over 600 aircraft)

scholar.google.com is another good source for finding articles about landing gear systems and design in general.


What do numbers signify in airport codes? As an Air Cadet, we go gliding very frequently. However, I've noticed something about the airport that we go to. The airport that we go to, Markham Airport, has a different airport code. CNU8.

Meanwhile, other airports, such as Toronto-Buttonville, Toronto-City-Centre, and Toronto-Pearson all have the following codes respectively: CYKZ, CYTZ, and CYYZ.

Do the numbers in airport codes signify something? If they don't, why is there a mix of both letters and numbers?

The code for Markham Airport, CNU8, is a Transport Canada identifier.

The codes for the other airports are ICAO airport codes. ICAO airport codes always consist of 4 letters. Markham Airport does not have an ICAO airport code.


Legend for SkyVector's Sectional Chart outside the US Does anyone know where can I find the legend for the symbols used by SkyVector's Sectional Chart for places outside the US? The US symbols are well documented but other places (e.g. the United Kingdom charts) seem to use a different set of symbols and line strokes for airspace classes.

Aeronautical agencies in Europe countries, not limited to European Union, and now Eurocontrol adhere to ICAO conventions more strictly than the US, this is historical as some European countries played a major role in ICAO creation.
Differences between FAA and ICAO approaches translate into the wording and the documentation. In accordance with Chicago Convention, these differences are listed in the country AIP, at section GEN 1.7 (examples: UK AIP, US AIP).
ICAO is an organization to facilitate international traffic, not domestic traffic, therefore it mostly deals with IFR matters, but there is some guidance for VFR too.
Sectional
The 1/500,000 VFR map is recommended and its characteristics are described in Annex 4 of the Chicago Convention, at chapter 17. The legend is described in appendix 2. The chart shown below, and its legend are compliant with Annex 4.
About annex 4, the US AIP tells us: "Charts vary in their conformance to ICAO Standards" This explains why US Sectional charts at SkyVector are different from charts covering Europe.
ICAO compliant maps are usually not public domain. In France maps are produced and published by a semi-administrative agency, the Institut Géographique National (IGN), in collaboration with the Service d'Information Aéronautique (SIA) in charge of the local AIP. They are commercial products, SkyVector cannot directly reuse them, but they can reuse public basic aeronautical information and open map bases.
In contrast, the French administration, probably by an effect of its infinite generosity, makes 1/500.000 ICAO VFR maps public via the GIS site used for various topographic/land information and aerial views.
ICAO and SkyVector versions of the same area (around Bordeaux).

ICAO 1/500.000 VFR map, France SW area
SkyVector shows a version which is significantly simplified (source: SkyVector):

SkyVector sectional map, same area
A notable difference is prohibited and dangerous areas drawn in red for the ICAO flavor. SkyVector lacks indications for activities like parachuting, and frequencies for ATC within controlled areas.
The map base is also a bit simplified, the Gironde estuary is missing though it's the continent largest (surrounded by famous vineyards, used to ferry parts by Airbus, Dassault or Ariane Espace, and also one of the places where surfers can ride a tidal bore).
The ICAO legend (a fragment showing airspace depiction, the full legend is here):

ICAO VFR map legend
VAC: VFR approach charts
If addition of 1/500.000 maps, detailed VAC are publicly accessible in the AIP for visual approach, E.g. the visual approach for Mérignac:

VAC Mérignac
Enroute
IFR enroute charts, the counterpart of Sectional and ICAO VFR charts are publicly available in the AIP, at section 2.


What is the most commonly occurring fault with this type of electrically driven gyro? I have an examination tomorrow about advanced avionics systems (EASA module 13) and we are required to troubleshoot a fault with the compass system. What is the most commonly occurring fault with a gyro compass system and how is it detected or identified?

Some idiot using magnetized a read by flux valve.
Gears  slipping. Sync knob sticking in.
Leaving it in DG mode.so it drifts

Not correcting for Magnetic Variation changes unless you fly along an isogonal


Normal tendency of helicopter with counter clockwise rotating main rotors (top view) with force trim off and leaving controls? Is it normal for the helicopter with CCW rotating main rotors to pitch down and roll left in forward flight, when force trim is turned off and hands off the cyclic?
Moreover, when we put the helicopter in right bank, would it tend to return to straight & level / left bank after a few seconds when hands off the cyclic (force trim off)?
By forward flight I mean 80 to 100 kts

With a American made helicopter equipped with a CCW rotating rotor, the helicopter will, as it accelerates past 10-15 KIAS, begin to pitch nose up as well as roll to the right.  This is a direct result of Effective Translational Lift (ETL) as well as Transverse Flow Effect.  Airflow through the main rotor disk past these speeds begins to take a more horizontal flow through the rotor disk, increasing lift on the advancing side of the rotor disk resulting in this.  European made helicopters with a CW turning main rotor will have a tendency to still pitch up as ETL becomes effective but will roll left due to gyroscopic precession from a greater lift imbalance on the front of the rotor disk being applied to the right side of the disk.


Can water-cooled brakes be used for takeoff aborts? Airliner engines are sized to continue the takeoff if one engine fails after it has become too late to brake. This means that the oversized engine has to be lugged around the whole flight, increasing weight and drag. Creating traditional brakes that could withstand the heating of a rejected takeoff just before rotation would also add significant weight.

The brakes on the SKYLON spaceplane boil water during abort, and it appears that the steam is dumped. The water is fed by pyrotechnic blowdown. Following a successful takeoff, the water is dumped overboard. This saves weight for the remainder of the flight.

My question is, can this approach be used to save weight on airliners?

SKYLON info.
https://web.archive.org/web/20151129034506/http://www.reactionengines.co.uk/tech_docs/SKYLON_Users_Manual_Rev_2.1.pdf
https://web.archive.org/web/20110615104534/http://www.reactionengines.co.uk/tech_docs/JBIS_v57_22-32.pdf
https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=36826.0;attach=1073534

This solves the problem of rejected takeoff, which is certainly a major factor in brake design. However, dumping the water after takeoff means that benefit is unavailable for landing. Events such as flap issues can require an aircraft to land at a higher speed than usual, requiring more braking capacity. The difference between this and rejected takeoff may not be enough to justify the weight, complexity, and expense of the water cooling system.


Could an airliner abort a landing after using the brakes system while landing? Everyone knows that doing a go-around is a normal procedure, although the go-around happens usually before applying the brakes system (spoilers, ground/air brakes, and/or thrust reversers), but, could you perform an aborted landing after using any brakes system?

Of course, this is not for a normal flight/landing, and there must be some conditions, like enough runway to gain speed again, and of course you should be not so low from Vr speed.

Let's see why someone could do an aborted landing after braking: There were at least two cases (Atlantic Airways Flight 670 and TAM Flight 3054) where the braking system just "fails" (actually both were a pilot's error, but let's say that was just a mechanical error).

Of course you will only notice that the braking system is failing when you activate it, and maybe is not like they are not working at all, but just working poorly, so you could see that the speed is slowing down, but also you can see that is not normal and maybe you just need to takeoff again and do another approach, or even going to another airport for a longer runway so you could safety brake with your malfunctional braking system.

After that explanation, I have two questions:

Can you technically perform an aborted landing after braking? I mean, could the automated braking system or the flaps settings interfere?
Would be this procedure be in any airline/airplane manual in case of a malfunctional braking system while landing? (i.e., an official procedure for this type of case)

Immediately after touchdown, the autobrakes will start to function, and may start applying the brakes depending on the aircraft's deceleration and the commanded deceleration.  If the pilot hasn't yet started to deploy the thrust reversers, a go-around is still possible at this point.  Advancing the throttles will disengage the autobrakes, and it's a normal balked landing from that point.

Also, advancing the throttles will stow the speedbrakes as well -- this is the way the system is designed, for exactly this sort of a condition.

As discussed elsewhere, once the thrust reversers are deployed, you are committed to stopping; a go-around is no longer safe to attempt after that.

If the brakes malfunctioned in a manner that the crew only became aware of after landing, chances are that they'd only become aware of it well after the thrust reversers were deployed, so the go-around isn't going to happen in response to that.  Thankfully, the wheel brakes on modern airliners are extremely reliable, and I can't think of any example of this sort of a failure.  If it did happen, you'd stay in max reverse as long as possible, use the EMAS if the runway has it, and use any available braking that you have (i.e. if the brakes on one wheel had failed but the others hadn't).  But it's not something that tends to happen on modern jets.


How do the vortices affect the flow of the horizontal stabilizer upon leaving the wing? Other than the downwash effect, what other factors that affect the flow to the horizontal stabilizer? such as Dynamic Pressure? Air Flow Disturbance?

The answer depends on the relative position of both. If the wake from the wing directly hits the elevator, its reduced dynamic pressure will reduce elevator effectiveness.

Next, when near the stall angle of attack, the wing root will already exhibit some flow separation, and the turbulence of that flow will show up in buffeting on the tail. This is sometimes desired as a stall warning, but having the tail move into the wing wake just when the aircraft stalls is generally a bad idea.

To address the lift-related vortices: Those will reduce the angle of attack change on the tail relative to those on the wing. The increased strength of the downwash speed with lower flight speed (and, consequently, higher angle of attack) means that the effective angle of attack on the tail will be reduced. This narrows the range of angles of attack in which the tail needs to work and helps to ensure that the tail will show a linear response to changes in the flow even when the wing leaves the linear range already (in other words: When the wing stalls.)


Is a weak battery a valid reason to reject a rented aircraft? Today I had rented a Piper Archer III for a local flight. After taxing to the fuel and filling up, I went to start the plane again and it did not want to turn over. This particular plane is somewhat fussy and sometimes doesn't start right away. As I continued to crank the engine over, you could tell the cranking lulled and the battery was having difficulty turning the engine over as effortlessly as it typically would. At one point the prop wouldn't even rotate.

I eventually got the plane started after a series of cranking / resting periods. I made the decision to not fly given the battery issue and returned the plane to its hangar.

The owner of the flight school was initially reluctant to comp the 1/3 of an hour I had on the hobbs (from taxing to gas pumps, etc) stating that once I had the plane started, I could have flown since it would have been powered by the magnetos.

My question: I know that the plane is powered by the magnetos once started, however, was my decision to not fly unfounded and unnecessarily cautious or would there be good reason not to fly knowing that the battery was weak and unreliable?

Update: It seems that some answers and comments have a focus on the financial aspect of my question. To be clear, this is not about money or how much. No one should pay for goods or services that were not rendered. The FBO's argument was that the choice not to fly was my own and not due to a responsibility of the FBO's to fix a "broken" plane. The money aspect is just an indicator of where the responsibility lies, on my shoulders or the FBO's.

First off, you absolutely made the correct decision. As PIC/pilot you have not only the ability, but the duty to call off any flight you don't feel comfortable regardless of the reason. Your go/no go decision can be based off of anything and you should always be comfortable making that decision.

Now as far as the battery goes I can tell you I was in exactly this situation a couple years ago with a rented Piper Comanche. It was cold out and the start attempts completely killed the battery. The FBO (also the owner) decided to jump it using a start cart and got it going. They comp'd me about .25 hours since they wanted me to sit on the tarmac at 1200 RPM until the oil temp gauge came up (something that I would have done anyway).

I made the decision to go, but I also made (a rather poor) decision to board a passenger while the aircraft was running (at the direction of the FBO and because I was at an unattended airport to pick that passenger up). I don't regret taking the aircraft but I never felt comfortable boarding somebody with the engine running.

In this situation you probably would have been fine had you left, provided you were making a VFR flight in good conditions. If this were IFR I would say that it would be better to say "no-go". The only thing you would probably have noticed would have been the ammeter showing the battery charging, but it would probably have recharged the battery in about 30-45 minutes of flying.

The other question is if the owner should have comp'd you for this and that is a little harder. You probably didn't burn all that much fuel or put much time on the engine tach so I'm guessing that while it would have been inconvenient to the owner, you didn't make a lot of difference financially (maybe $20 at most).


In-game Air Traffic Control questions I have been making an AI ATC for a game I have been writing. The channel is mostly dead air but occasionally you can hear some chatter:

http://reskin.us:8081/stream

I am a former airline pilot and a few scenarios come up frequently in the game which I don't have experience with in RL (luckily):

1) Aircraft flying through the class B without talking to approach

2) Aircraft establishing communication with ATC when already inside the class B

3) VTOL operations - to separate aircraft I understand they fly a very normal approach to the airport but then are treated like rotorcraft after that? Do they hand you over to ground control when you are over the numbers or how is that coordinated?

Any controllers out there know what they would say in these cases (if anything) over the radio?

Thanks!

ATC will try to contact the unknown aircraft on the sector frequency and, if that fails, on Guard.  Since they don't have a tail number, they'll call the aircraft by location and altitude (e.g. unknown aircraft 4 miles northwest of XXX at 3500 feet).  At the same time, they'll begin vectoring other traffic away from it to maintain separation; this is similar to how Center/Approach will vector IFR traffic around unknown VFR traffic in Class E airspace, except in Class B they'll also be vectoring VFR traffic (rather than giving mere traffic advisories) as well.  There will likely be missed approaches, TCAS RAs, etc. that have to be dealt with as well.  Still, the only real difference with this happening in Class B vs Class C/D is the staggering volume of traffic affected.

ATC may in some cases ask a friendly pilot in the right place to try to identify the violator.  I've been asked to do that once; we weren't fast enough to get the tail number, but we did identify it as a low-wing single at the reported altitude, which was still useful info for ATC.  I don't know what happened after ATC vectored us back on course; this was years before LiveATC existed.

If/when communication is established, ATC will inform the pilot they're in the Bravo, give them a squawk code and vector them out as quickly and directly as possible without further disruption to traffic flows--without regard for the pilot's desired course.  They'll also ask them to "copy the phone number", as with other violations.  Don't expect any favors from ATC after that, of course, but they're as calm and professional as usual once the immediate safety problem is resolved.

I don't know anything personally about VTOL operations, but I'd assume they'd stay with Tower just like a helicopter--either "cleared to land" on the runway or "land at your own risk" somewhere else on the airport--and wouldn't go to Ground until/unless they needed to taxi within the movement area.


Is it an overkill to request to see airplane maintenance logs at a new flight school? I'm getting a checkout at a new flight school, so I don't know anything about the maintenance records of their airplanes other than this school has been in operation for some time and so I assume everything is in order.  As PIC, though, I would think I would feel better seeing for myself that this plane I have never flown before is indeed up-to-date, at least in its required inspections.  I've never had an urge to do this before, I've always just trusted that the flight school is running things properly, but I guess since I have quite a bit more experience since my last checkout I felt like looking into this would be judicious.

Is this overkill?  Would it be taboo or send a message of distrust to the school if I asked to see the mx logs on my plane I'm getting checked out in?  Does anyone make it a point to do this?  Thanks in advance for your comments.

I'd refer to FAR 91.3(a):

  The pilot in command of an aircraft is directly responsible for and is the final authority as to the operation of that aircraft.

Therefore, I believe you have a duty to determine that the aircraft is properly maintained.   While that doesn't mean disassembling it and checking the work yourself, I do think that its reasonable to verify that the maintenance logs have recent entries, and appear orderly.

At my old flight school, I never got any grief at all (and occasional complements) when I wanted to see the logs for some reason.

If they give you so much as an eye-roll when you ask to see the logs, that should be a cautionary sign.

I think it is also an easy way to meet the maintenance guys, and be introduced to them as a careful, thoughtful pilot.  (The Mx guys likely despise "cowboy" pilots who bring back damaged equipment, and don't report it.)  You'll get to know some people at the new school, and get a reputation right off the bat.


What was the Airfoil of Handley Page P.115? This extreme sweptback delta was built to test the Concorde wing at low speeds, sources say it had a biconv 6% airfoil, but I failed in finding data about it.

Did you see what Wikipedia had for it, and the book it came from?

  Specifications (HP.115)
  Data from X-Planes and Prototypes: From Nazi Secret Weapons to the Warplanes of the Future [Winchester 2005, p. 134]

  General characteristics

  Crew: one

  Length: 50 ft 4 in (15.33 m)

  Wingspan: 20 ft (6.1 m)

  Height: 12 ft 9 in (3.9 m)

  Wing area: 432 ft² (40.1 m²)

  Airfoil: Bicon 6%

  Empty weight: 3,680 lb (1,670 kg)

  Useful load: (Fuel) 1,175 lb (533 kg)

  Loaded weight: 5,050 lb (2,291 kg)

  Powerplant: 1 × Bristol Siddeley Viper BSV.9 turbojet, 1,900 lbf static (8.455 kN)
  Performance

  Maximum speed: 248 mph (399 km/h)

  Endurance: 40 minutes

This paper goes into calculations on biconvex airfoil as well, interesting reading  https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930085007.pdf


Are there any simulators around to simulate ADS-B data (TIS-B & FIS-B)? I am trying to find a simulator like the Spirent GPS Simulators. Are there any Simulators out there which can simulate and generate random traffic and weather information for TIS-B & FIS-B testing?

I have an ADS-B 978 UAT receiver hooked up to an antenna which receives signals mostly from 1 tower. I would like to hook up a simulator to the UAT receiver which can simulate the ADS-B data block (customized). I tried searching via Git and many other places couldn't find one.

Has anybody came across any such a thing? Objective - TIS-B to generate random traffic, FIS-B to generate necessary weather.

Aeroflex IFR-6000
From the manufacturer's website:

The Aeroflex IFR 6000 is a compact, lightweight and weatherproof unit designed for testing transponder modes A/C/S, TCAS I and II as well as DME. Includes antenna shield and hard transit case. The IFR 6000 features an extremely easy to use interface where every parameter the user commonly needs to view is displayed on screen.
Dedicated Mode keys for XPDR, DME and TCAS allow quick selection of the operational mode. The application dependent softkeys and data select/slew keys provide an intuitive man machine interface. DME mode is provided with dedicated keys for frequency/channel selection and RF level control.
For frequently varied parameters in DME and TCAS modes, such as Range and Rate, dedicated keys are provided. Each operational mode has one main user screen. The operational modes are: XPDR (Sub-Modes: ADS-B MON, ADS-B GEN & GICB) DME TCAS 1, 2 (Sub-Modes: TIS) Most tests can be completed without leaving the main user screens. This simplifies the line technician's testing task.

However, it is subject to stringent export restrictions. If you are outside of the US, it is not available to you.


Is there a downwash equation? I need to find an equation for the following problem: Suppose a full-size glider passes 10 feet over my head at high speed. No doubt I will feel the downward air pressure (downwash) caused by the angle of attack of the wings. But if the same glider flies over me at a distance of one mile, I will not feel any effect at all.

So obviously there is a diminishing strength of the downward air pressure that eventually lessens to a point where I cannot physically detect it. Therefore, is there an equation that, with all relevant criteria being inputted, such as air temp, air density, wing speed, wing characteristics, wing angle of attack, etc., can allow me to at least approximate how far I must be below a passing wing to be unable to detect its downward pressure wave?

What you probably are looking for is the Biot-Savart law.

This is originally describing the magnetic field generated by an electric current; however, it was soon found that it equally well describes the induced speeds caused by a vortex. The vortex is the bound vortex of the wing plus the free vortices trailing behind it. Integration over their length will give the induced speed at a given point. This speed is proportional to the inverse of the distance to the vortex squared. The vortex strength depends on air speed and span loading; the proportionality being with the inverse of flight speed, aircraft mass and the inverse of wingspan squared.

There is also a dependency of downwash speed with the inverse of air density at the altitude where the glider flies, but this will be canceled out when the effect at ground level is calculated. What is left is an inverse dependency on the local air density at ground level.

Note that you will only get the induced speed, not the pressure from the Biot-Savart law. In order to calculate the pressure increase, you need to add the equation for the pressure rise of the downwash interfering with the ground. This pressure is proportional to the downwash speed squared and air density, so now all density effects are canceled out and you will be left with those factors for the pressure rise from an aircraft flying overhead:

the square of the induced downwash speed

which depends in turn on:

the inverse of height squared
aircraft mass
the inverse of wingspan squared
the inverse of flight speed

Note also that this does not consider viscous effects.

In order to know the limit of detectability, you also need to know the sensitivity of your measuring equipment.


Is it possible to overheat or damage the engine on an F-16? The MiG-25 can supposedly damage its engines by commanding too much thrust and gaining too much speed. Somewhere around mach 3 damage to the engines is likely, I believe.

What about the F-16?

What happens if the pilot, at altitude, attempts to simply go as fast as it will go?

I believe the F-16 has FADEC (Full Authority Digital Electronic Control). The MiG-25 does not. I imagine this would limit the amount of fuel flow by some limit.

However, even if this is true, is it still possible for the pilot to exceed the ordinary limits imposed by the computer?

As a bonus question, it would be interesting to also mention if this does or does not apply to other fighters, in particular the F-14, F-15 and F/A-18.

Yes, you can overheat and damage an F100 or F110 engine just like any other jet engine.  It has mechanical and thermal limits that may not be exceeded.  And it often happens as part of high performance military flying, though it can make you very unpopular with your crew chiefs and inevitably with you commanding officers if you keep willfully exceeding the limits and damaging engines.

FADEC systems ie “power by wire” systems just use a computer to administer engine control commands based on pilot inputs.  They do not necessarily limit a flight crew from giving inputs that can exceed engine parameters.

Earlier engines were more finicky about this, in particular to exceeding hot section temperature limits or compressor stalls.  The F-14A with the TF-30 engines was particularly prone to compressor stalls and could be treacherous during critical phases of flight.  Improved intake diffuser, gas core aerodynamics, advancements in materials science and manufacturing plus improvements to fuel control units reduced the risks but did not eliminate them.


Up to what thrust setting of a gas turbine engine can the airplane stay stationary on ground? I noticed that when a jet engine airplane is started or is conducting run-up, the airplane remains stationary even though the engine is already burning gas and is supposedly producing thrust.

What keeps the aircraft stationary while the engine is spinning? Up to how much percentage of the engine's maximum thrust can you put the thrust setting on as to not have the aircraft move about its stationary position?

An alternate question would be: "On what thrust setting on each engine (assuming twin engine) will the airplane start to move and accelerate?"

There are two answers to this question depending on how you look at it.

If the brakes are on: Full Thrust wont even move the plane this is a requirement of the braking system.

Brakes off: Somewhere a bit above idle. John covers it in his answer nicely. It will vary by loading and aircraft.

A propeller plane can get moving even at idle thrust. While jets don't do run ups (unless required for maintenance), propeller planes preform a run-up prior to takeoff where the brakes are utilized to hold the plane in place at a high thrust. A proper short field take off will also involve the application of brakes and full thrust.


What are the factors behind crew pairing and crew rostering? What are the factors to be taken in to consideration for crew pairing and crew rostering?

It is very, very complicated.
It is so complicated that an entire department is dedicated to this task. Below I would provide a glimpse of crew rostering.
Basics
Most airlines provide roster on a monthly basis. The flights that will be flown are well planned beforehand. From this, a minimum number of crew must be on each flight, for example a Captain, a First Officer, and certain number of flight attendants. Many requirements and restrictions must be meet. For example:

Crew must be qualified to perform their duties (more on that below).
Duty time, rest time, ground time, turn-around time must be legal, and preferably, reasonable.
Mandatory crew may be different for different aircraft types. For example, a B777 on a long haul flight may require 2 Captains, 1 First Officer, 1 Second Officer and 10 flight attendants. A A320 on a short flight would require 1 Captain, 1 Second Officer, and 4 attendants.
Generally speaking, cabin crew can be swapped between aircraft types, such as between Airbus and Boeing. Pilots are current (legally qualified to fly commercially) only on a specific type.
Crew are sometimes assigned to ad-hoc duties, such as accepting delivery of a new aircraft.
Besides flying, crew would also have training duties, line-check duties and simulator duties.

Constraints
Mostly for safety reasons (and also for risk reduction), some pairing combinations are not allowed either legally or by company requirement. For example:

A pilot aged 60 or above must be paired with another pilot below the age of 60.
A newly joined Captain (defined as having flown X sectors or less) must not be paired with a newly joined First Officer or Second Officer.
Similarly, the percentage of newly joined cabin crew (defined as having flown X sectors or less) should not exceed a certain number.
Some flights may call for an experienced crew, for example a new route (no one has landed at that airport before) or charter flight.

Qualifications
There are various qualification requirements that must be fulfilled for a crew to legally perform duty on commercial flight. For example,

Captain must have made a takeoff and landing within the previous 30 days.
First Officer or Second Officer must have made 3 takeoffs and landings within the previous 90 days.
Certain qualifications (e.g. takeoff and landing requirements above) expire, but can be renewed on a commercial flight. You'd want to plan it so that the pilot has a chance to attempt it during duty hours, instead of going through additional training after it has expired.
Certain qualifications must be renewed through training, for example in a simulator. You'd also want to plan it so it is renewed before flying status is invalidated. Remember that the trainer may also have flying duties as well.
Route may require additional ratings. For example crew must be ILS CAT-III trained to use it. If it flies over Chinese airspace crew must be trained to fly metric system. If it flies over the Atlantic crew must be trained to fly North Atlantic Tracks.
Line-check needs to be performed every X number of days.
Crew must possess the necessary nationality or Visa for the departure / destination airport.

Ad-hoc / stand-by
Unforeseen circumstances such as mechanical problems, adverse weather, on-route diversions, crew sickness etc. may require last minute changes to the roster list. This is undesirable, so a certain number of crew would be on "stand-by" duty, meaning there is no duty assignment on that particular day, but they must be available at a particular airport within X minutes shall the need arises. There are legal requirements on stand-by time and duty time after stand-by as well.
If the department does not plan well, there may be insufficient number of crew members (i.e. not enough manpower) to serve all flights.
Improvements
Fatigue is becoming more of a hot topic in aviation. Just because a duty assignment is legal and within company policy, does not necessary mean it is good. Software can be used to analyze factors such as timezone shifts, jet lags, day night patterns etc. to identify and avoid possible fatigue scenarios.
On certain routes, it may be beneficial to assign crew who can speak certain foreign languages. For example, if statistics show that a portion of the passengers on a route are Koreans, it would be better to assign it to cabin crew who can also speak Korean. It may even be a company requirement that the cabin crew together must speak a few chosen languages, so at least there is someone who can translate.
How it is done
As you can imagine, given this many constraints, the roster is done by software. It is mainly a constraint satisfying problem, which can be solved by many well-established algorithms in computer science.
Some rules are "hard rules", meaning they are legal requirements. Some are "soft rules", they are best accommodated to provide optimal performance but may be violated when necessary. For example it is preferable to fairly allocate flight and duty time. It is also preferable to fulfill any route preference requested, but that may not be possible given other constraints.


Why do most authors use wingtips vortices as reason for 3D flow around wing? Quote John Anderson Fundamentals of Aerodynamics:

The three-dimensional ﬂow induced by the wing-tip vortices shown in
Figures 5.4 and 5.5 simply alters the pressure distribution on the
ﬁnite wingin such a fashion that a net pressure imbalance exists in
the direction of V∞ (i.e., drag is created). In this sense, induced
drag is a type of “pressure drag.

figure 5.5

I agree that induced drag is just one type of pressure drag but wingtip vortices don't cause 3D flow at wing (downwash behind wing  + two rollup vortex...)
Am I right?

It depends a bit on the definition of a "wing tip vortex".
If this is defined as just the local flow around the wing tip, it is too narrow to encompass all 3D effects and you are right.
If, however, the term "wing tip vortex" describes the beginning of the whole wake rollup process caused by downwash and sideways flow, then this does cause induced drag. The vorticity behind the wing cannot create drag anymore; this can only be done by things happening directly at the wing. But induced drag is spread over the whole wing and not restricted to its tips, so the "wing tip" part of the name is misleading.
In my view of the process, induced drag is caused by the gradual bending of the flow by the wing. By bending an already deflected flow further downwards, the reaction force must have a backwards component, which is induced drag. Note: No wing tip flow required for the explanation! But that is too simple, or pure 2D drag would also produce induced drag. In fact, the flow is first bent upwards ahead of the wing (induced angle of attack) so the bending happens not beginning with straight but upwards moving flow. Without the added downwash of the trailing vortices, all effects cancel out so only a vertical force is left. Add the downwash over the wing produced by the free vortices and - bingo! - the backward component is precisely the induced drag added in 3D flow.
The often-heard explanation that the flow around the wingtips causes induced drag is much less helpful and similar to saying that wet streets cause rain. In the end, wingtip flow is only a reaction to local pressure differences, in the same way that the induced angle of attack is. And it is this pressure difference over the whole span which causes the flow to bend around the wing and be accelerated downwards. This downward movement then causes wake rollup and the wake vortices, which in turn start at the wingtip.
As to the "why" you are asking: In my opinion it is copying from others without fully understanding cause and effect.


Are all IFR flights assigned squawk codes in US controlled airspace? In the US, all IFR aircraft need a clearance to be in class A, B, C, D, and E airspace. Does this mean that all aircraft with clearances need to be assigned squawk codes by ATC when they enter?

No.
/X (VOR only), /D (VOR/DME only), /Y (LORAN only), and /M (TACAN only) aircraft do not have transponders. Primary-only aircraft can be assigned flight plans, and fly IFR. It's not common, though, because aircraft that will fly within 30 miles of class B airspace, or aircraft that will operate above 10,000 feet MSL are required to be equipped with transponders and Mode C altitude reporting, similar to the ADS-B requirements. (14 CFR § 91.215)


Is a retreating blade stall a problem that can be overcome on dual-rotor helicopters? I know that regular main+tail rotor helicopters stall at higher speeds as the relative airspeed of the retreating blade approaches zero.

I'm curious if coaxial or intermeshing dual-rotor helicopters are affected by the same or a similar problem.

I'm aware that other factors may dominate and impose speed limits on them as well, but I'd like to know if a retreating blade stall is a problem that can be overcome with dual rotors.

Dual and intermeshing rotors also suffer from retreating blade stall at high forward velocity. But the effect of this is much less dramatic than with a single rotor.

Retreating blade stall causes a loss of lift on one side of the rotor: the single rotor helicopter will start to roll. A helicopter with two rotors that counter-rotate doesn’t experience this rolling moment, only an increase in drag.


What is this high-wing jet airplane? Can someone help me in identifying this plane?

(planespotters.net)

The flag is an easy giveaway. It's one of two* British Aerospace Avro RJ85's operated by Dubai Royal Air Wing.

* Probably it's the A6-RJ2 (but the registration is blurry).


What are RW values in Venule increments? In US AIP differences from ICAO:

12.3.1.7 d/e/f
U.S. controllers do not give wind speed, visibility, or RVR values in metric terms. RVR values are given in 100- or 200-foot increments while RW values are given in Venule increments. [emphasis mine]

Same AIP's abbreviation list does not mention RW. Google wasn't helpful.
Here 12.3.1.7 d/e/f references chapter 12 of Doc 4444 15th edition (not the latest). The same section in the latest 16th edition is irrelevant (phraseologies regarding traffic information). If I find the older 15th edition I'll update.
The same entry is present in the Nov 2016 AIP edition, so it's neither new, nor a likely typo (PDF; 20 MB).

The best way to get a definitive answer is likely to email the FAA (there's a link at the bottom of the AIP page) but my strong suspicion is that both RW and Venule are errors caused by scanning in an old document, or maybe manually entering it.
First, if you go back to a 2002 version of the FAA's ATC orders 7110.65, there are references to "RVR/RVV" values. I suspect that "RVV" was scanned or manually entered at some point as "RW" and no ever noticed. In fact, if you search the FAA site for "RVR/RW", the only hits appear to be old, scanned copies of paper documents.
I also found an explanation that shows that RVR and RVV were often used together, which to me supports the idea that "RVV" is the correct abbreviation:

g. RVR/RVV.

Provide RVR/RVV information by stating the runway, “visual range” or “visibility value,” as appropriate, and the indicated value. The
abbreviations “R-V-R” or “R-V-V” may be spoken in lieu of “visual
range” or “visibility value.”

The latest 7110.65 doesn't refer to RVV any more, by the way:

This changes [sic] removes all references to Runway Visual Value (RVV)
from this order.

Second, "Venule". Based on the dictionary definition and Googling, it's clearly a medical term, not an aviation or meteorological one. So what might it have been? The PC/G definition from the old 7110.65 linked above says:

Runway Visibility Value (RVV)- The visibility determined for a
particular runway by a transmissometer. A meter provides a continuous
indication of the visibility (reported in miles or fractions of miles)
for the runway. RVV is used in lieu of prevailing visibility in
determining minimums for a particular runway.

I can't think of a word close to "Venule" that means "in miles or fractions of miles" but possibly the original text was "1/4 mile increments" or "¼ mile increments" (or another fraction). Depending on the original text size, font etc. it's possible that "1/4 mile" become "Venule".
Anyway, this is all speculative even though I think it's very plausible. I'd definitely email them if you want an authoritative answer.


How would you get certified for the AgustaWestland AW609 as a rotorcraft pilot or without any previous certification? It seems like AgustaWestland might finally get certification for the AW609 in the next couple of years.  Let's say I buy one to transport people to the offshore oil platforms that I hypothetically own.  I'm going to need pilots with a commercial powered-lift rating or possibly an ATP powered-lift, depending on how the aircraft ends up being certified.  Where am I going to find these pilots?

As far as I can tell, the only people who current have FAA powered-lift ratings either converted military ratings from the V-22 Osprey, or are civilian test pilots who worked on the V-22 or AW609 programs.  I guess I could try to hire these pilots, but I will be competing with every other AW609 operator.

Is there a way for rotorcraft pilots to transition to powered-lift?  Is there any way, currently, for a civilian pilot to go from no ratings to commercial powered-lift without getting non-powered-lift ratings first?

I know nothing about powered-lift aircraft, but according to 14 CFR 61.5 they're a separate category for licensing, like airplane, rotorcraft or glider. It is therefore possible to get a "private pilot powered-lift" certificate without having any flying experience in any other aircraft type. 14 CFR 61.109, 61.129 and 61.163 state the flying requirements for private, commercial and ATP powered-lift ratings respectively and 61.65 has the requirements for a powered-lift instrument rating.

61.109(e)(5) does allow substituting some limited airplane (i.e. fixed-wing) experience for powered-lift time:

  (5) 10 hours of solo flight time in an airplane or powered-lift
  consisting of at least—

There are also allowances for using simulator and military experience in lieu of powered-lift flight time, but I couldn't see anything that directly allows rotorcraft experience to count towards powered-lift certification. The fact that powered-lift is a category of its own suggests that the FAA considers them to be significantly different from rotorcraft.

So yes, you could theoretically start from zero and work to get your private, instrument, commercial and/or ATP ratings with flying time in powered-lift aircraft only. If, that is, you can find a powered-lift aircraft and an instructor: an ATP requires 1500 hours of experience and doing them all in powered-lift aircraft may not be practical (61.163 only requires 250 of them to be in a powered-lift aircraft).

In reality, I suspect that any civilian powered-lift pilots who are not ex-military are (or will be) people with extensive rotorcraft and/or fixed-wing experience who then follow a training program provided by the aircraft manufacturer. Your insurance company will probably also have a say in who you hire and what experience they have.

Finding and training those people won't be cheap, but if you're buying up new AW609s then you can probably afford it :-)


What are the regulations and testing that determine whether a "Spins Prohibited" placard is required in an aircraft? Clearly some flight testing and certification process is used to establish whether or not a type of production GA aircraft is or is not placarded "SPINS PROHIBITED". What type of testing and what results determine the outcome/certification? What does such a result mean for the aircraft's actual performance in a spin/recovery situation? I know spin certification is completed with a recovery parachute mounted to the tail in case of an unrecoverable spin and that an aircraft must recover within 6 turns to be certified (unless you are Cirrus and have a parachute) but what else is there?

Spins require a demonstration for certification, but can be bypassed with an FAA waiver as Cirrus did for the SR-20/22. The waiver was granted under the understanding that the only way to recover a Cirrus is to pull the chute.
FAA CFR Part 23 governs the process and requirements for certifying general aviation aircraft. Specifically for spins you are wanting to read CFR 23.221 which outlines the process of spin testing:

(a) Normal category airplanes. A single-engine, normal category airplane must be able to recover from a one-turn spin or a three-second spin, whichever takes longer, in not more than one additional turn after initiation of the first control action for recovery, or demonstrate compliance with the optional spin resistant requirements of this section.
(1) The following apply to one turn or three second spins:
(i) For both the flaps-retracted and flaps-extended conditions, the applicable airspeed limit and positive limit maneuvering load factor must not be exceeded;
(ii) No control forces or characteristic encountered during the spin or recovery may adversely affect prompt recovery;
(iii) It must be impossible to obtain unrecoverable spins with any use of the flight or engine power controls either at the entry into or during the spin; and
(iv) For the flaps-extended condition, the flaps may be retracted during the recovery but not before rotation has ceased.
(2) At the applicant's option, the airplane may be demonstrated to be spin resistant by the following:
(i) During the stall maneuver contained in §23.201, the pitch control must be pulled back and held against the stop. Then, using ailerons and rudders in the proper direction, it must be possible to maintain wings-level flight within 15 degrees of bank and to roll the airplane from a 30 degree bank in one direction to a 30 degree bank in the other direction;
(ii) Reduce the airplane speed using pitch control at a rate of approximately one knot per second until the pitch control reaches the stop; then, with the pitch control pulled back and held against the stop, apply full rudder control in a manner to promote spin entry for a period of seven seconds or through a 360 degree heading change, whichever occurs first. If the 360 degree heading change is reached first, it must have taken no fewer than four seconds. This maneuver must be performed first with the ailerons in the neutral position, and then with the ailerons deflected opposite the direction of turn in the most adverse manner. Power and airplane configuration must be set in accordance with §23.201(e) without change during the maneuver. At the end of seven seconds or a 360 degree heading change, the airplane must respond immediately and normally to primary flight controls applied to regain coordinated, unstalled flight without reversal of control effect and without exceeding the temporary control forces specified by §23.143(c); and
(iii) Compliance with §§23.201 and 23.203 must be demonstrated with the airplane in uncoordinated flight, corresponding to one ball width displacement on a slip-skid indicator, unless one ball width displacement cannot be obtained with full rudder, in which case the demonstration must be with full rudder applied.
(b) Utility category airplanes. A utility category airplane must meet the requirements of paragraph (a) of this section. In addition, the requirements of paragraph (c) of this section and §23.807(b)(7) must be met if approval for spinning is requested.
(c) Acrobatic category airplanes. An acrobatic category airplane must meet the spin requirements of paragraph (a) of this section and §23.807(b)(6). In addition, the following requirements must be met in each configuration for which approval for spinning is requested:
(1) The airplane must recover from any point in a spin up to and including six turns, or any greater number of turns for which certification is requested, in not more than one and one-half additional turns after initiation of the first control action for recovery. However, beyond three turns, the spin may be discontinued if spiral characteristics appear.
(2) The applicable airspeed limits and limit maneuvering load factors must not be exceeded. For flaps-extended configurations for which approval is requested, the flaps must not be retracted during the recovery.
(3) It must be impossible to obtain unrecoverable spins with any use of the flight or engine power controls either at the entry into or during the spin.
(4) There must be no characteristics during the spin (such as excessive rates of rotation or extreme oscillatory motion) that might prevent a successful recovery due to disorientation or incapacitation of the pilot.

Another good read is the Aircraft Certification Service - FAA Flight Test Responsibilities, Procedures, and Training which states:

506. Spin Tests. Spin tests conducted by FAA FTPs should be flown initially with a spin chute (or equivalent equipment) installed on the aircraft and approved by an FAA structural and/or systems engineer. (See Appendix 3 for additional guidance on requirements for spin recovery devices). After all spin modes have been evaluated and found satisfactory, the spin characteristics should be checked with the external spin chute removed, unless it is determined
that the spin chute installation has no significant effect on spin characteristics.

(Emphasis Mine)


Are any software or aeronautical engineers yet attempting to design pilotless passenger planes (PPP'S)? With all of the effort currently under way to attempt to create driverless land vehicles (which I believe may be a rather misplaced effort) has anyone yet heard of any serious efforts also being made to one day try to eliminate passenger jet pilots as well?  As a former private pilot myself, such a thought seems rather ludicrous, but just wondering.  It seems to me the elimination of humans from overseeing human safety concerns such as flying or driving, would simply be "unsafe."

Serious discussion of removing passenger jet pilots?  No.

Serious discussion of making pilotless VTOL aircraft? Yes.

Uber, for one, is already working on this. Check out this quote from page 40:

  To fast-forward to the safest possible operational state for VTOL
  vehicles, network operators will be interested in the path that
  realizes full autonomy as quickly as possible.


Is AMDAR a required system on aircraft? I was intrigued by the assertion that COVID-19 depressing commercial aviation has lead to lower quality weather forecasting

  The aircraft observations are a key piece in the jigsaw of national and global weather data that is fed into computer models through a process called data assimilation. Multiple studies have found that aircraft are among the most important data sources for reducing the error in forecast models.

After some poking around, I found out the system is called AMDAR

  The AMDAR system predominantly utilises existing aircraft onboard sensors, computers and communications systems to collect, process, format and transmit meteorological data to ground stations via satellite or radio links. Once on the ground, the data is relayed to National Meteorological and Hydrological Services (NMHS), where it is processed, quality controlled and transmitted on the WMO Global Telecommunications System (GTS).

Is this system required by aviation authorities anywhere? Or is there merely some incentive system to encourage participation?

AMDAR (Aircraft Meteorological DAta Relay) is a program established by the World Meteorological Organisation to gather weather data from around the world. It's run through a number of local and regional AMDAR organisations who negotiate with partner airlines arrangements to use existing aircraft sensors to gather and report weather data on each flight.

The gathered data is relayed by satellite or radio to ground stations and then forwarded on for processing and distribution.

(I've paraphrased from this source)

So, there is no specific AMDAR equipment. The AMDAR system is implemented by arrangement with partner airlines, and may be installed on some or all of the airline's aircraft that already carry suitable sensors.

There is no mention of a requirement that an airline partner with a regional AMDAR organisation, and thus no requirement for their aircraft to carry the system.

It's not clear from the pages at the WMO what the nature of the collaboration between the local AMDAR organisation and the airline is, so there may be some payment to the airline, or there may be some benefit in kind: free or reduced cost access to meteorological reports, perhaps.


Why might American Airlines fly a 767 from JFK to EWR? I was browsing FlightAware and saw the following:

This is an American 767 flying from JFK to Newark (EWR).  Surely this isn't a passenger flight...this isn't one of American's normal routes.  Why might an AA 767 be making this flight?

It's a positioning ferry, to move the aircraft from where it "is" to where it "needs to be" for its next revenue leg (or maintenance, in some cases). These sorts of legs are uncommon because they're expensive; ideally an aircraft is never out of position this way, but sometimes "stuff happens" and you fly an empty plane to get it where it needs to be.


Is this a C-17 (and why is it here)? This aircraft flew overhead at less than 1000 ft a little while ago. We think it's a C-17. We can't figure out what it was doing...

(Click here for full image)

We're in Culver City, between LAX and Santa Monica. It was traveling south to north, about 4:50 this afternoon.

Scared the neighborhood...

Yes, that is indeed a C-17. As to why it's in the area, only the Air Force would know.

https://www.boeing.com/defense/c-17-globemaster-iii/#/overview


When is the use of reverse thrust recommended in airline operations? I know the answer largely depends on each airline's FOM but I still wonder what the FOMs generally recommend with regard to the use of reverse thrust after landing. For example, I guess its use would be generally recommended for the accelerate-stop maneuver and also for landing on short runways.

So once again, what're their general recommendations on the use of reverse thrust after landing, if any?

The main use of Reverse on landing for big-fan engines is to kill the residual forward-thrust rather than to actually supply braking airflow. This offloads the (wheel-)brakes.

If the runway is short, then the wheel-brakes will need assistance to get the aircraft stopped in time, and then you'd use more Reverse. Some aircraft have an Intermediate Reverse click-stop, which allows you to use a standardised mid-level of Reverse; and then there's Full Reverse, but that gets noisy, which some airports don't like (especially at night).

The level of Reverse used is the P1's decision, while complying with aircraft performance on that runway, the airport's noise policy and the airline's balance between engine wear and brakes wear.