If you turned base early, cutting off other traffic, what is the safest way to rejoin downwind? Joined the left traffic pattern at a controlled field downwind.  Controller informed me I was number three for landing. Saw traffic on final, turned base, reported to tower "following cessna on final". Controller comes back a minute later and realizes I cut off a plane on final and I was now number two (my mistake here.  I realize now, I think, I should have not maneuvered at all unless I was 100% sure I could see planes 1 and 2 on final). Controller tells me to rejoin the downwind.  At this point, I was still on the base, so I turned right to rejoin the downwind and the plane behind me that was on final passes too close below me while I am executing a turn from base back to the downwind.  Didn't seem safe.  In fact, as soon as the controller told me to rejoin the downwind, that didn't seem safe.  I am not sure what I should have done.  I could have A) had more situation awareness and turned left to get back to the downwind  B) called for a go around (on a base?), moved to the upwind leg (not departure) and rejoined the pattern. C) the controller should have told the plane on final that was behind me to get out of the patter by going around to the upwind leg.

I realize I caused this issue by maneuvering to base following the wrong plane.  Like most aircraft incidents, it is usually a combination of factors. I caused the first, did I cause the second?  Should I have called for a go around. What should the controller have done?

In the future, I can fix my issue. But what do you do if you are cutting off for whatever reason a plane on final, while you are on base. What is the safe way to get out of the situation.  Ideas?  Thanks

Interesting, but you're not the first to encounter this situation. I understand from what you say that you were going to wedge in between the no 1 and no 2 traffic already established on final.
Given the circumstances and not time to think about this, the preferred option would be to turn left to rejoin downwind. Assuming no other traffic in the pattern. Then you are turning towards the other traffic. A left turn would have given you a full 270 degree and time to regroup

Should there have been other traffic on the left base then they would be positioned further downwind from your position. You may become a conflict for them then by turning right.  Equally there may have been traffic joining downwind like you did in which case a left turn could become a conflict to them.

This is just assumption. I'm just pointing out the need for full on situational awareness particularly in the circuit. Need to know where all traffic is relative to you.

Finally, I would say it would have been more reassuring for the controller to specify “turn left/right now to rejoin downwind”. If you had made it to final then a missed approach would be the way out and continue rwy heading until advised.


A330 flown by low cost airline - is 8 cabin crew really all they have? I'm reading the Australian Transport Safety Bureau report on an incident involving an AirAsia X A330 (PDF). The flight in question was intended to be Sydney to Kuala Lumpur so something like a ten to twelve hour flight.

The report mentions that there were 8 cabin crew on board.

Wikipedia says AirAsia has 377 seats in their A330's. Can it be true that they service that many seats with only 8 cabin crew ?

The number of flight attendants required on flights are mandated by international safety regulations. For planes with up to 19 passenger seats, no flight attendant is needed. For larger planes, one flight attendant per 50 passenger seats is needed.—Wikipedia

Eight cabin crew is enough. 377/50 is 7.54.


What are the mechanisms fitted in the SA321G Super Frelon rotor head? Past the cyclic-collective pitch control, I understand (maybe incorrectly) that additional mechanisms are required to prevent or limit vibrations and loads on the mast and the blades.

Aerospatiale SA321G Super Frelon, photo by Burkhard Domke (source)

There are other rotor heads that are very simplified:

Bell AH-1 Super Cobra (source)

Can you explain what are the main mechanisms in the Super Frelon rotor head, and why the simple rotor head design is not used?

All rotor heads need to deal with multiple forces but two in particular have a big influence on the design and complexity of the rotor head.

As a blade moves forward (the advancing blade), it experiences an airflow equal to the speed of the blade plus the air speed.  As the blade moves backwards (the retreating blade), it experiences an airflow equal to the air speed minus the speed of the blade.

Therefore, the advancing blade generates more lift and will rise which causes the airflow to hit the blade with a more vertical component, reducing the angle of attack and the lift generated.  The opposite happens to the retreating blade.

This causes the advancing blade to flap up and the retreating blade to flap down.  The rotor head must allow this to happen and deal with the resulting forces.

The second effect arises from the Coriolis effect.  This results in a force applied to the hub by each blade as it speeds up and down called lead/lag.

There are three main types of rotor head.

Fully articulated.

From danubewings.com, copyright of FlightLearning.com

The blades are attached to the hub with hinges that allow the blade to flap up and down and lead/lag (or drag) hinges around the hub, allowing these forces to be absorbed without applying them to the blade or the hub. The blades may also rotate in a cuff through which the blade is attached to the hub. Each blade can flap and lead/lag.  Note that dampers may also be fitted to reduce vibrations and to better absorb the forces.

These are the most complex heads, an example of which is in your first image.

Semi-rigid.

Copyright www.copters.com

The blades are attached to the head with lead/lag hinges only.  Flapping is enabled by allowing the entire head to "teeter" on hub so that if one blades rises, the other must fall.  They cannot flap independently. Since the entire disc tilts together, semi-rigid heads can only have 2 blades.

The coning hinges allow both blades to move up and down together, without regard to where the teetering hinge is, as power is changed collectively.  So, the flapping (or teetering) hinge enables cyclic flapping whilst the coning hinge enables collective flapping.

Rigid.

Copyright helistart.com

The blades are rigidly attached to the hub and the flapping and lead/lag forces are absorbed entirely through flexing of the blades.  This is the simplest of all heads.

The choice of rotor head type is a complex one with intended design and performance being primary drivers but, as the head gets more complex, rigid being the simplest and fully articulated being the most complex, the maintenance cost goes up and generally, so does the weight.  Conversely, fully articulate heads produce the lightest loads on the main rotor shaft, it's thrust bearings and the gearbox coupling allowing weight savings to be made there. Rigid heads also require the strongest blades, and therefore weight, although modern composites are enabling the manufacture of blades with high flexibility but lower weight.

The head you have shown is particularly complex as it is six bladed and has an automatic folding system so that it can be stored and hangared in small spaces and be ground manoeuvrable on aircraft carriers with limited deck space. The tail folds at the same time as the blades. Most of the stuff you can see apart from the blades, their cuffs and their hinges is hydraulic piping, pumps and motors, electrical bonding strips, sensors and transducers. There is also an oil lubrication system for the bearings - you can see the oil reservoir on the top of the hub.  The use of elastomers in bearings has removed a lot of the need for lubrication.

If you stripped all of that it away, it wouldn't look (quite) so complex.  I.e. Not so barking mad!

Copyright helistart.com


Can the autopilot (or stall avoidance system?) of the B737 MAX 8 be overridden by sheer force? A New York Times article from today about the Lion Air Flight 610 crash claims that in order to control the airplane the pilot

  could have braced his feet on the dashboard and yanked the yoke, or control wheel, back with all his strength.

Thanks to T.J. Crowder's comment I realize there is not only the autopilot but also a (new?) stall avoidance system installed on this new line of B737s.

Is it true that either one can be overridden by a simple application of sufficient force to the yoke? If so:

What is the respective underlying mechanism for the systems?
What force would be necessary, respectively?
Are both systems designed such that they can be overridden simply by applying an unusually strong force, or would that be just a violent and "unofficial" way to control the yoke despite the systems' best efforts?1

I understand that the main flight controls of this recent incarnation of the Boeing 737, the MAX 8, are still hydraulic. Does that play a role in the "override by sheer force" possibility?

1
A design which would allow a pilot to eventually control the plane just by applying excessive and unusual force (as opposed to perform a complicated series of button presses and/or touch screen actions to disable either system) would in my opinion make a lot of sense as a "panic mode".

I'm not sure of the full story here, but if you pull the controls of a 737 while the autopilot is engaged the autopilot will trip and the pilots can fly the plane manually. This requires about 25 lbs of force.

There is also a button on the yoke where you can disengage the AP. So if the AP was controlling the plane and going into a violent descent the pilots should have been able to cancel it by pulling the yoke or pushing the button on the yoke or the mode control panel below the windshield.

And no, the controls being hydraulic doesn't play a role in the "override by sheer force" possibility.

Edit:

  The autopilot servos are limited to 25 lb of force for single channel operation. Separate force sensors measure pilot column input and the autopilot will disconnect if the force applied by the pilot(s) exceeds 21 lbs.

Source


Why can planes generally take more positive g's than negative g's? Most commercial airliners are rated to take +2.5g and -1.0g.  Why is this?  Is it designed that way on purpose?  To clarify, this would mean that the cost difference between -1g and -2.5 g is minuscule, so price (and thus engineering difficulty, which drives price) isn't really a factor.

Or, are there in fact significant difficulties with creating a frame that can handle a lot of negative Gs?  (And if there are, what are they?)

It's partly pragmatic (you start from +1.0 G, so why not optimize for that???) and partly because (most) aircraft are designed to carry human beings.  Humans as well as a lot of other things are FAR more tolerant of positive G-forces than they are negative G-forces.

There's very little technical reason that you couldn't design an aircraft wing and other structures to handle high negative G loads.  But adding that strength also means adding weight, complexity, and cost.  And since the benefit of being able to pull high negative G loads is pretty small, very few designers choose to do this.


Who performs repossessions of airplanes? When the owner of an aircraft defaults on their loan, their lender can send repo men to take the aircraft back, often against the owner’s will. However, unlike cars, which can be driven by anyone with a license, there are so many expensive type ratings for aircraft.
Do they specifically hire a pilot with the needed rating for each given job, or are there dedicate aviation repo men with scores of type ratings to cover any eventuality? It seems like the skill set to fly the plane doesn’t necessarily qualify you to slip in quietly and take it back from a belligerent owner.
Also, my friend Bianfable got me thinking of another issue. Who repossesses aircraft when the owner has fled with it to a foreign country?

Yes there are a couple of reality TV shows that have been done on repos.  There are companies who specialize in the business, and the pilots have to be type rated where appropriate.  They have to be legal to fly the airplane.
It takes a special kind of risk taker pilot to do that kind of work, in view of the risks of getting into confrontations with irate owners, and flying airplanes that may or may not be airworthy.  The companies are usually hired by the holder of the chattel mortgage on the aircraft; the lender in other words (and who is, ultimately, the owner).  Banks and leasing companies generally, and even government foreign aid financing organizations from time to time.
Yes the scenarios presented on the tv shows are semi-fictional BS,  with dopey staged chase scenes, but even dialing the drama back closer to reality, it's not a job for the faint of heart.


What is the fastest accelerating aircraft on takeoff? As of Feburary 2017 the Tesla Model S has the fastest 0-60mph time of any production car. With the fastest 0-60mph time recorded as 2.28 seconds.

This got me thinking, is there any aircraft that whilst on the ground can achieve a similar 0-60mph time?

Airplane performance really isn't gauged that way, partly because quick acceleration 'drag race' data is not a pertinent aspect of their flight envelope.  That being said, there are a few examples, one being from the TV show Top Gear where a Bugatti Veyron races a Eurofighter Typhoon - and gets smoked by the jet.

I don't have data on jet fighters as far as linear acceleration; a quick calculation could reveal some basic data.

Take the case of an F-22.  Assuming a 55,000 lbf takeoff weight, lineup, 70,000lbf thrust at full power, then brakes off and rolling, we expect to see an acceleration around:

$$(70/55)*32.2 ft/s^2 = 41 ft/s^2$$

This also assumes no friction from the wheels or air resistance during the takeoff roll.

By basic kinematics, the jet would reach 60mph or 88ft/sec in 88/41 = 2.15 seconds.

So could an F-22 or another high performance jet fighter beat an Model S in a drag race?  Well it's theoretically possible and and as the above example shows, it has happened and it didn't end well for the auto.

As for airliners, the car is going to smoke them until the car reaches Vr for the jet or thereabouts.

And there is no way in hell a Model S is going to do 0-1000 mph.


What exactly do "attempt" and "cycle" mean in these starter duty limitations? Can someone please explain me this A320 Starter Duty Limitation in simple terms?
E.g. for the CFM56 Starter:

No running engagement when N2>20%
4 cycles of max 2 mins
Pause between
start attempts . . . . . . . . . . . . . . . . . .. . . . . . . . . 20
sec
Cooling period after 4 attempts . . . . . . . . . . . . . . . . .
. . . . . . . . 15min

Does it mean the moment I put Engine Master to ON till Automatic abort by FADEC in case of Automatic Start or Manual abort by turning the engine master and man start button off (limiting it to 2 mins) in case of Manual start = 1 Cycle. Then 20 Seconds gap. Then Next Cycle and so on and then say after 4 unsuccessful cycles I got to wait for 15 min.
But things get confusing between words Cycle and attempt. Since for another type of Engine it says

Auto start with up to 3 start attempts is 1 cycle.
Between
successive cycles – 20 seconds pause (for auto or manual ground
starts).
After 4 failed cycles – 15 min cooling period.

What is attempt and what is cycle? I hope someone explains it in real simple terminology.

Three start attempts are considered one "CYCLE" (we talk this in terms of starting the engine, that engine will get started in atleast these attempts).
A gap of 20sec or 35 sec after each attempt (failed /successful) is required.
And the cooling period of 15 min after 1 COMPLETE CYCLE (or 4 failed attempts) is required.
hope this helps.


What are approach control's expectations regarding weather information for flights to satellite airports? I have never passed through class-C airspace without intending on landing at the primary airport.

If the flight is conducted under VFR, and I am planning on landing at a satellite airport to the primary class-C, will approach control expect me to indicate that I have ATIS information from the primary airport, that I "have numbers" for the satellite airport landing destination, or that I have both weather station information sets?

What about just passing through their airspace with no intent to land nearby? Do they still expect that you indicate receipt of ATIS information?

I fly out of a controlled satellite class D (KLOU, Bowman Field) below a class C (KSDF, Louisville International) so I'm fairly familiar with this scenario, at least in the way that it's handled there. The short story - in my experience - is that Approach only cares about you having the numbers or ATIS for the airport where you'll actually land.

First the theory. The ATC orders say:

  7−1−3. APPROACH CONTROL SERVICE FOR VFR ARRIVING AIRCRAFT

  Issue the following where procedures have been  established for
  arriving VFR aircraft to contact approach control for landing
  information:

  a. Wind, runway, and altimeter setting at the airport of intended
  landing. This information may be omitted if contained in the ATIS
  broadcast and the pilot states the appropriate ATIS code or if the
  pilot uses the phrase, “have numbers.”

Note the "airport of intended landing", they aren't going to pester you to get the ATIS for somewhere that you aren't going to.

Second, the practice. If I'm inbound to KLOU on flight following (don't leave home without it!) then my first contact with Louisville Approach usually goes like this:

  Me: Louisville Approach, N12345 level at 6500
  Appch: N12345, roger, Louisville Altimeter is 2992, report when you have the weather at Bowman, information Kilo is current
  Me: N12345 has Kilo at Bowman
  Appch: N12345, roger [and further instructions as needed]

As a controlled field, Bowman has ATIS, not "the numbers" but I've had more or less the same exchange at other places.

I think that Ron's comment about information is useful here: when I'm inbound I usually have both the KSDF and KLOU ATIS anyway, just in case. Also notice how the KSDF controller helps me: the KLOU ATIS could have changed from Kilo to Lima between the time I got it and the time I called Approach. By telling me that Kilo is current, the controller is effectively telling me if I have to go and get the ATIS again or not.

As for just passing through class C, the very few times I've done that ATC has simply given me the local altimeter setting and that's it. I'm not landing, so they don't seem to care if I have the ATIS or not.


What is the distance from an airport from which an airliner climbs above 550 m? Is it possible to determine a common distance from the runway threshold at which an airliner climbs above 300 metres and 550 metres above-ground-level (AGL)?

And for landings? Where do they descend below it?

I need to determine at least an approximate value of common distance. But in  the best case I’d like to determine:

the maximum distance
the minimum distance
the average distance or the distance which is used by most airliners.

I am not from aviation, thus I need to ask this question to professional pilots.
The aim is related with the “Bird strike problem”.
300 m and 550 m – is respectively the common height and the maximum height of flight of Black vulture - a bird species living in South and North Americas which caused the most strikes with aviation within its range. I’m doing the scientific research and study the risk of collision with this bird and the possible measures to decrease this risk.

For the landing is quite easy.

Airliners usually approach an airport descending along $3^\circ$ slopes. This means that they will be 300m AGL approximately 5.7km before the runway threshold, and they will be at 550m AGL about 10.5km before the same point.

For the take-off the situation is a bit more complicated, as each aircraft will have a different performance. Taking a value of about 1000ft/min for the vertical velocity and 200Kts for the forward velocity (in aviation we use the imperial system, for a bit of background see here) we get similar distances to the above (it is a $2.8^\circ$ slope)

Note that these paths are more or less a straight continuation of the runway, particularly on the landing side (less so on the take off side).

Each airport has approach and departure procedures, you could try to have a look at those. They are usually published by Jeppesen.


How does an FMS shift after losing all external navaids? It's not uncommon for polar flights to lose GPS signal (ionosphere issues due to the high latitudes). But it is not a concern because the typical IRS drift is 650 meters for every hour of flight, and the skies are empty (compared to the Atlantic tracks) in those regions.

Sooner or later GPS will be back, navaids will be within reach, and radar coverage will resume.

Q: Now, what happens when the GPS signal is lost? Does the FMS navigation start to drift from this point on, or does it switch to all the accumulated IRS drifting that's been going on for hours prior?

One way to picture the latter (I guess), is the magenta line on the navigation display to abruptly shift away from the plane-symbol, even if it is just by a mere few nautical miles.

My question applies to the older IRS systems that require stationary alignment, unlike the new GPS-coupled align-in-motion systems found on the 787, etc.

Turns out indeed it's an issue affecting polar operations. It differs from type to type, but for the 737-600/-700/-800/-900 as an example, the message UNABLE REQD NAV PERF-RNP will be displayed.

For oceanic areas this will only happen if ANP shifts by over 10 NM, i.e., after losing the RNP-10 capability.

At an IRS drift rate of 650 metres per hour, it would take 28 hours of being airborne or a rather shifty IRS unit—no pun intended—for the message to be displayed.

So the answer is that the magenta line won't shift, unless the pilots choose an IRU over the rest by using the position shift function of the FMS.

For the 747-400:

  When no global positioning system (GPS) updating occurs, all position and velocity corrections gradually are phased out until the FMC navigation parameters equal the selected IRU position and velocity.

This logic is part of the RNP standards and regulations, to stop an auto flight system from chasing the course when navigational accuracy becomes questionable. Any loss of GPS (away from ground navaids) inhibits the FMS from applying any corrections without crew intervention.

Source: Polar Route Navigation


Why are the engines of the Airbus A400M slightly tilted down? Picture: Youtube.

Firstly, are the engines really tilted down? I have tried to check another picture over the net, seems they are really tilted down slightly. But need confirmation from you experts, however.

Second, if it is true, what is the reason?

As Jeffrey points out in his comment to the question:

  In flight, they are probably horizontal.

When that plane is at cruise conditions, it will be in a very slightly nose-up pitch attitude. the thrust line from the props will then be in the direction of travel.


What is SNLF technology? Aerion together with Lockheed Martin is building the AS2 supersonic jet. This is the most realistic SS business jet project of all time. But what do they mean by SNLF technology which claims to reduce drag? And how is it better than the delta wing which they claim is inferior.

SNLF stands for Supersonic Natural Laminar Flow.

Laminar flow over the wing reduces the friction drag. Achieving this has been the aim of a number of designs, from the laminar flow airfoils of the past to the latest 737 MAX winglet. While it is difficult enough to achieve in subsonic flight, the high wing sweep and Reynolds number in supersonic aircraft make it much more difficult to achieve.

One method of achieving this is to use wings with low sweep (unlike delta wings) and sharp (supersonic leading edges) at the expense of other forms of drag.

Dark colors show the expected laminar flow regions, while the graph shows the pressure gradients. Image from Unconventional Configurations for Effecient Supersonic Flight by I. Kroo

A number of designs have been proposed to this end from reverse delta to the Aerion's design, which looks strikingly similar to F-104 starfighter.

One method of achieving the laminar flow (i.e. extending it chordwise) in supersonic flight is by using laminar flow control (LFC) methods like suction etc. A good example is the use of suction in a F16XL test aircraft by NASA, which produced laminar flow over nearly half of the wing (less than the design value though).

F16XL with porous titanium LFC glove on the left wing, image from NASA report TF-2004-12 DFRC, F-16XL Supersonic Laminar Flow

The problem with LFC is that it increases weight and takes up space in the wing, hardly an advantage in a supersonic aircraft. So, the next thing to do is increase the laminar flow distribution without using any mechanical (or other) aids.

Natural laminar flow means the presence of laminar flow even in the absence of any LFC measures. From NASA F-16XL Supersonic Laminar Flow document:

  Passive laminar flow can be achieved in the wing design process, .... Passive laminar flow can also be created on an existing wing by altering the cross-sectional contour of the lifting surface to change the pressure gradient. Both of these laminar conditions are called natural laminar flow.

SNLF then, is basically laminar flow in supersonic flight without the aid of active boundary layer control methods.

SNLF has been demonstrated in the past (unsurprisingly in F-104), but the tools to analyze it and replicate it in other aircraft were lacking. This seems to the main thrust of the Aerion.

The AS2's wing design has been tested by NASA in a F-15 and the results seem to be encouraging.

SLF flight test on F-15 with NASA Dryden (top). Predicted transition (left)
and infrared image (right) showing extensive natural laminar flow. Mach 1.8, 40,000 ft., Reynolds Number about 10 million. Image from Unconventional Configurations for Effecient Supersonic Flight by I. Kroo

Aerion doesn't say that delta wing is inferior, but it is a simple fact that you can't use a delta wing for supersonic laminar flow. Aerion claims that its design will have 20% less drag than delta wing, but till the aircraft actually flies, we should take its announcements with a large dose of salt.

There are other problems the company has to overcome if the product is to be successful- if the wing is thin (as I expect it to be) and quite small, the aircraft's range appears wildly optimistic. For example, the F-104 had thin wings, but had the fuselage to put the fuel in; something that is very difficult in AS2 unless the passengers agree to carry some. Also, the small wing size may lead to quite high landing speeds.

Planform comparison of AS2 (top) and F-104. Not to scale. AS2 from company website; F-104 from Wikipedia- attributed to Kaboldy.


Why are airliner seats higher than chairs and couches at home? I'm 6-feet tall and even I find airplane seats too high. My feet barely touch the ground when I sit upright. Why can't they make the seat cushion as low as a living room couch?

The short answer,

Your couch is made for you to fall asleep on, watch football from, and generally be of any non determinant shape since no couch (as far as I know) carries a type certificate.

Aircraft seats are designed to fit as many passengers as is legally allowed and practically possible while still passing the 16G tests the FAA imposes. The 16G requirement is largely for your safety.

Most pilot seats are in some way adjustable up/down and forward/back depending on the age of your aircraft.


During single-engine taxi, how is the asymmetric power compensated for? For various reasons (e.g. noise, fuel savings), some airlines allow single engine taxiing. Obviously, this produces an asymmetric thrust during the taxi. If the left engine is used, the aircraft always wants to steer to the right. How is this compensated? Do pilots use the tiller all the time to countersteer, or pedals, or brakes? Is there a possibility to "trim" the aircraft during taxiing?

First off, the thrust asymmetry problem is far less pronounced in large jet aircraft as compared with light twin engine propeller driven aircraft.  Secondly, taxi operations generally don’t use very much thrust, with the engines often at idle power during this process, only requiring brief bursts of moderate thrust to get the aircraft moving from standstill.

Taxiing small, light twins can be difficult in an OEI (One Engine Inoperative) scenario, in many cases being almost impossible to turn the airplane sharply toward the good engine.  Sometimes pilots will simply turn the aircraft only towards the dead engine and perform a 270° turn toward the dead engine instead of attempting to turn the airplane toward the good engine, should a turn toward the good engine be required.  Sometimes, as a loss of an engine becomes an emergency situation, a light twin pilot will sometime just shut down on the runway or on a turnoff, then just have the aircraft towed back as opposed to attempting to taxi it with an OEI.

Asymmetric thrust can also be used by light twin aircraft to perform even sharper turns at slow speeds, with the pilot simply advancing the throttle to the engine on the outside of the turn while leaving the throttle on the inside of the turn at idle.  This can also be useful for maintaining directional control while taxiing, taking off and landing in strong crosswind conditions, since it requires less rudder input to correct.


How do drones overcome latency? The US Military's use of drones has become commonplace, and widely known at this point. Although these vehicles are operated from nearby bases during these attacks, it seems like the latency (time of transmission) would be problematic as far as flying goes. Are these vehicles typically flown 100% by autopilot, where there's very little real-time reaction?

There are multiple ways to fly and control Unmanned Aerial Vehicles (UAV), or drones, for e.g. the Predator.

Source: science.howstuffworks.com

Some UAVs (like the Global Hawk) can perform the entire mission (from takeoff to landing) autonomously, negating the need for a pilot.
Most of the UAVs, like Predator can perform (i.e. fly in) some simple missions (like reconnaissance) autonomously.
In case a geostationary satellite is used for communication with the UAV, the latency is around 300 ms (The electromagnetic waves have to travel ~70000 km). In case of other delays (like equipment etc.) this will not be greater than 500 ms or around half a second. This is not significant in case of slow moving systems like Predator (they are not dog-fighting, after all) and the 'pilot' can effectively control the aircraft.
The only situation where this is a problem is when the UAV is taking off/landing and in this case, the control is handed over to local LoS operators.

The Predator is reported to have a 'latency' of around two seconds, which causes problems during takeoff/landing. According to the telegraph,

  But the two-second delay between a pilot moving a joystick in Nevada and an aircraft responding in Afghanistan is enough to cause a crash during take-off and landing. Crews in Afghanistan control 'launch and recovery’ through direct contact with antennae on the aircraft. Half an hour after take-off, control of the Reaper is handed to a crew in Nevada; half an hour before landing, it returns to the crews on the ground in Kandahar.

Note that the RAF also does things the same way. According to the report on formation of 'drone' squadron' at RAF Waddington,

  Although the personnel will be permanently based at RAF Waddington, some will go to Afghanistan to control the take-off and landing of the drones locally.


Why are airplanes parked at the gate with max rudder deflection? Quite often I see aircraft parked at the gate with rudder deflected to the max. I see this either with Boeing and Airbus aircraft so it must have been done on purpose. I know that there are dampers connected to the yaw, or are those not powerful enough to keep the rudder straight e.g. undeflected?

The control surfaces of airliners are not connected to the pilots' control via cables; they are operated by a hydraulic pump. When the engines are shut down, there is no hydraulic pressure in the pipes, and the control surface is free to move.

The rudder is moved from the center position by wind. If you observe the gates, you should note that all airplanes have their rudder deflected to the same direction. In a perfect no-wind scenario, the rudder would stay neutral.

There are no gust locks which the pilot must arm before leaving the cockpit on Boeing aircraft (and I presume Airbus too). Gust locks are, however, common in general aviation aircraft. They can also be found on some small business jets.

The reason being, control surfaces on small aircraft work "both ways" - if you move the elevator by hand, the yoke in the cockpit will move as well. These are called "reversible flight control systems". Therefore, when the control surfaces are moved by wind, the entire system - yoke, cables, wheels, bearings etc. are all moved back and forth. This brings a significant amount of wear and stress to the system. Strong wind may also cause the surfaces to deflect past their designed maximum, causing damage.

The control surfaces on airliners are much heavier and much stronger. Also, they are not "directly" connected to the cockpit's controls - when there is no hydraulic power, pretty much every component is disconnected. Unless you're facing gale force winds, it is safe to just let them swing free with wind and gravity.


What happens to a plane that goes to / from an enclave when the surrounding country closes its airspace? When Pakistan closed its airspace, planes that had routes flying over Pakistan had to deviate around that country.

What would happen to planes en route to or from Lesotho, if South Africa closed its airspace?

Are the planes simply unable to leave or enter the country, or there is a law / regulation about this situation?

it would be no different than in case say China and Russia both closing their airspace for aircraft flying into and out of Mongolia. There'd be no way for aircraft to enter or leave that country.

Nothing special about being an enclave there.


Can you change airways when they cross without a named fix? There are a few victor airways that cross without a named fix, just two solid lines drawn over each other on the IFR low charts. Can these be used as intersections for changing airways in IFR route planning? Assuming you are above MEA for both, prior to the crossing. They aren't very common but I happen to have one very near my usual airport that along with a poor DP makes planning for certain directions rather tedious.
Examples

the crossing of V55 and V170 just north of JMS VOR on chart enroute L-14 North Dakota;
V495 and V23 with V187 over Tacoma(this one may be due to SEA class B) ;
V183 NE of RZS near Santa Barbra, could you plan to turn north from V183 onto V485 or V107?

Yes one can fly one airway to intercept another. Many reasons exist as to why not all intersecting airways have an intersection, the simplest being, it wasn't necessary.
I will suspect one may encounter difficulties in executing your desire to change airways as stated. Such would be the inability to file a flight plan with dispatch or that flight planning software can't/won't accept this unconventional navigation method and the most illogical, if one could accomplish the later, I would image would be ATC. Why? Because the controller has never encountered this situation, before and doesn't want to explain their actions should something go afoul.
For years ATC would issue preferential routes to aircraft departing KPIA to KORD as such; PIA PIA030R V10 PLANO ORD. Aircraft would depart KPIA on the tower assigned departure heading then be vectored to join the PIA 030-radial to intercept Victor-10 northeast of BDF VOR onward to KORD. Then computers became more involved along with flight management systems and pilots were no longer capable to navigate this route because computers couldn't calculate the routing or how to intercept one radial (airway) from another without a set point (intersection) along the second radial , something pilots had done since the 1950's.


What Paper Format do Boarding Passes use? I'm looking at creating some Boarding Passes for my Virtual Airline called "Zelandas". After looking at websites like the SITA website, Wikipedia, and more, I cannot seem to find what format of paper is used for a Boarding Pass.

When I am talking about Format, I mean something like A4, or B5 etc.

Where would I be able to purchase this kind of paper, not in bulk?

Thanks, Will

Standard boarding passes are the size of an IBM punchcard, 7⅜ by 3¼ inches (187.325 mm × 82.55 mm) because paper and printers in that size were readily available at the time, and then inertia kept the size the same even when punchcards fell out of use and it became a specialty item.

Many airlines have switched to rolls of 3⅛ inch (79.375 mm) thermal paper, as is now commonly used in cash registers. For a new system, this is probably less expensive and easier to prototype.


Does speed or angle of attack generally have the greatest impact on total induced drag? I know induced drag varies with speed and angle of attack in straight and level flight.  Which factor primarily determines the amount of induced drag?  The speed of the airfoil through the air, or the angle of attack of the airfoil?

The change in angle of attack --as an end result of changes in speed-- causes the greatest difference in induced drag.

Induced drag drops with increases in speed because the faster-flying wing needs to deflect air by less in order to create the same lift.

Please read this answer which tries to explain induced drag much more intuitively than what you probably have read until now. With more air flowing past the wing per unit of time at higher speed, less deflection is needed, so the backward tilt of the lift vector is smaller. Since the weight of the aircraft should not change with speed, the same aerodynamic force has a smaller backward component at higher speed or in denser air.


Do the operations practices of low-cost airlines represent an increased safety risk? Low-cost airlines spend less money on their operations. In most (not all, clearly) contexts of life and business, more money spent on the same kind of thing means a higher quality product or service.

Do any of the cost-saving measures adopted by low-cost airlines lower the quality of their operations (flight operations, aircraft maintenance, crew training, crew quality) in a way that could affect safety?

We should not make statements about any particular airline. Air travel is and remains very safe, due to:

Good practices imposed by the regulatory institutions.
Feedback of things that went wrong in the past to prevent them from happening in the future.
Very mature engineering and technology implementation
Lots and lots of experience with reliability numbers over the decades.

That being said, proper procedures do need to be followed and it could theoretically be the case that only minimal maintenance is carried out at some airlines, while others are more pro-active and lead the field in safety practices. Think Rainman, and the airline that has never crashed.

Safety numbers of all airlines in the developed world are very good. Cheaper airlines must follow the same practices as more expensive airlines. The cheaper tickets are the result of better business practices, not of worse maintenance practices.

Edit

@Michael Kjörling points out a TV episode about a case of Madrid airport being closed, all traffic lining up for Valencia, and three RyanAir aircraft declare fuel emergency. Plus a LAN Chile declares engine out Mayday.

Don't know if this counts as evidence though, TV programs must find or produce a topic that is sensational enough for transmission. The safety numbers are still on RyanAirs side, their safety record is pretty good.


What is the difference between a loss of control and an upset? What is the difference between a loss of control and an upset? From what I have read, first, an upset occurs, which leads to a loss of control (LOC). But, when can one say that the upset has been transformed into a LOC?

Aircraft upset

   is a dangerous condition in aircraft operations in
  which the flight attitude or airspeed of an aircraft is outside the
  normal bounds of operation for which it is designed. This may result
  in the loss of control (LOC) of the aircraft, and sometimes the total
  loss of the aircraft itself.

Loss of control

   is the unintended departure of
  an aircraft from controlled flight, and is a significant factor in
  several aviation accidents worldwide and the leading cause of jet
  fatalities worldwide. Loss of control may be the result of
  mechanical failure, external disturbances, aircraft upset conditions,
  or inappropriate crew actions or responses.

TL;DR:

Upset occurs when attitude and/or airspeed are outside of the boundaries where the aircraft is controllable.
Upset is one of many possible causes for loss of control.


What system is there in the UK to prevent collisions between small aircraft? I met someone the other day who owns a small plane and he was going to fly from Cambridge to the Isle of Wight.  I asked him whether he had to file a flight plan and he said no.

Just wondering therefore how such collisions are prevented?

Small airplanes will be under VFR (Visual Flight Rules) which entails that the pilot looks out the window and is responsible for staying away from other aircraft and staying out of the clouds (the fog banks of the sky).

If you see another plane in your path then there are standard rules to avoid him see this question.

They can fly under IFR (Instrument Flight Rules) but that requires that Air traffic control monitors the airplane and steers it away from other planes.


Is it possible to make an analogy between a lever and an airplane wing in terms of force applied over distance? On most aircraft the engine force (thrust) is lower than the weight. Since wings therefore are always capable of generating greater force (lift) than the engine, there is an analogy between an airplane and a lever.

Now, a lever produces greater force by doing the same work on a shorter path. How can we prove that wings enable the doing of work on a shorter path than the engine thrust? Is it reasonable to say the path on which the thrust does the work is the distance the aircraft needs to accelerate to takeoff speed, and the work/energy accumulated this way is used by the wings to exert greater force on a shorter path on the air? (And then this kinetic energy is constantly replenished by the engine keeping it constant, assuming no further acceleration?)

Is this the right Newtonian explanation of flight? How can I find the distance on which the force is doing work on the air?

Well, they call them air PLANES for some reason.  Maybe not a lever, how about a ramp?

How does 1/4th the thrust lift a given weight?  One consideration that is very important for aviators is to realize the best way to use thrust is to create speed.  Speed creates lift.

It is indeed a minor miracle that the airflow over a wing at flying speed creates so much upward force.  One way to see how this works is to look at the back of a boat while it is travelling slowly.  See the swirls and eddies of the water in the wake.  Now speed up and the water separates from the stern and forms a wave behind the boat. The lack of water at the stern is the same as air being deflected away from the top of the wing at sufficient speed.
This area of lower pressure near the wing is lift.  How much to lift a one ton Cessna? The wing is roughly 5 x 40 = 200 square feet.  200 square feet x 144 square inches/square feet = 28800 square inches.  2000 pounds/28800 square inches = 0.07 psi.  Not much, but it works!

Slow down and the wave collapses back to the boat.  This is a stall on a wing.  So lift is INDIRECTLY produced from thrust by forward motion (and angle of attack).


How were large pieces of the A300-600ST and the B747LCF transported? I will present my reflection based on the Airbus A300-600ST Beluga and I suppose the reflection is the same with the Boeing B747LCF Dreamlifter:

The A300-600ST was built because its predecessor (the B377SGT Supper Guppy) was not large enough to transport future aircraft's large pieces. Those pieces are too large to be transported by train or by road.

But the A300-600ST's pieces must have been transported to build the aircraft. Some of the A300-600ST's pieces must be larger than the pieces this aircraft is designed to transport. So I'm puzzled because I cannot figure out how large pieces of this heavy transporter were transported to its assembly site. The same reflection goes with the B747LCF.

The answer may be that parts were transported the same way A380 parts were transported

  The A380’s size means its fuselage and wing sections are shipped via a surface transportation network that includes specially-commissioned roll-on roll-off ships to carry these sections from production sites in France, Germany, Spain and the United Kingdom to the French city of Bordeaux. From there, sections are transported by barge along the Garonne River to the Toulouse final assembly line.

From Airbus - TRANSPORT OF MAJOR AIRCRAFT SECTIONS

According to All about Guppys

  The A300-600ST was built in Toulouse, France.

All the smaller pieces would have fitted into an existing transport aircraft.


What lights are used on top of a building or structure near an airport? What type of light (strobe, beacon, color) should be displayed on top of a building or structure near an airport ?

The general guidelines are:

  4.3 Lighting Systems. Obstruction lighting may be displayed on structures as follows:

  Aviation Red Obstruction Lights. Use flashing lights and/or steady-burning lights during nighttime. Tower structures are typically
  marked with flashing red lights. Buildings and smaller obstructions
  located near airports should be marked with steady-burning red lights.
  (See Chapter 5).
  Medium-Intensity Flashing White Obstruction Lights. Medium-intensity flashing white obstruction lights may be used during
  daytime and twilight with automatically selected reduced intensity for
  nighttime operation. When this system is used on structures 700 feet
  (213 m) AGL or less, other methods of marking and lighting the
  structure may be omitted. Aviation orange and white paint is always
  required for daytime marking on structures exceeding 700 feet (213 m)
  AGL. This system is not normally recommended on structures 200 feet
  (61 m) AGL or less.
  High-Intensity Flashing White Obstruction Lights. High-intensity flashing white obstruction lights may be used during daytime with
  automatically selected reduced intensities for twilight and nighttime
  operations. When this system is used, other methods of marking and
  lighting the structure may be omitted. This system should not be used
  on structures 700 feet (213 m) AGL or less, unless an FAA aeronautical
  study shows otherwise.
  Note: All flashing lights on a structure
  should flash simultaneously except for catenary support structures,
  which have a distinct flashing sequence between the levels of lights
  (see paragraph 4.4).
  Dual Lighting. This system consists of red lights for nighttime and high- or medium-intensity flashing white obstruction lights for
  daytime and twilight. When a dual lighting system incorporates
  medium-intensity flashing white lights on structures 700 feet (213 m)
  AGL or less or high-intensity flashing white lights on structures
  greater than 700 feet (213 m) AGL, other methods of marking the
  structure may be omitted.

Specific details are spelled out in AC 70/7460-1L CHG1 Obstruction Marking and Lighting.


Why does Boeing name its aircraft B7x7 and Airbus names theirs A3x0? Airbus and Boeing use this special naming scheme for their civilian aircraft models.

All Boeings built today are B7x7.
(In the past, also other numbers were used: the shortened version of a B707, the B727 and even older models like B367, B377 etc. )

Also, Airbus uses a common scheme: A3x0, though there a few numbers outside this scheme: A318/19/21

(Both manufacturers also build military aircrafts with different schemes, like A400M.)

So, is there a special reason for these naming schemes, or is is just that they sound good and unique?

Airbus started with the A300, which as usernumber commented was a 300-seat airliner design. So A for Airbus, and 300 for the number of seats. An A250 was also considered (guess how many seats), which became the A300B. The models counted up by 10 from there.

Boeing model numbers historically counted up, including the Model 40, Model 80, Model 247, Model 307 Stratoliner and Model 377 Stratocruiser. At the dawn of the jet age, they decided to change up their numbering scheme:

  To support this diversification strategy, the engineering department divided the model numbers into blocks of 100 for each of the new product areas: 300s and 400s continued to represent aircraft, 500s would be used on turbine engines, 600s for rockets and missiles and 700s were set aside for jet transport aircraft.

The 707 prototype was called the 367-80, or "Dash 80." When the time came to give it an official number they knew it was going to be a "Jet Transport" and would get a 700-series number, and they decided "707" had a better sound to it than "700". They kept the 7's and have counted up from there (not entirely in order).


How do the cabin noise levels of the A380 and the 777 300 ER compare? I couldn't find any official comparison for noise level (dB) in Airbus A380 versus the Boeing 777 300 ER. Does anyone have some info about it? Which one is better in terms of acoustic isolation?

From a luxury round the world flight on several different models of aircraft on several different airlines, a traveler used the exact same sound meter at his seat in either business or first class to measure ambient noise level during cruise.

Here is a chart I made of his measurements, including carrier and age of aircraft. As you can see, long haul aircraft are quieter than short. Carrier and age of aircraft also seem to make a difference.

For this set of measurements, the b773 is 3db (or 25%) louder than the a380.


How does vorticity change the lift coefficient of an airfoil? For airfoils in unsteady motion, the lift coefficient oscillates and the wake is characterized by vortex shedding.
How does vortex shedding affect the lift coefficient for an airfoil?

Shed vortices from unsteady flow over an airfoil result in decrease and phase lag in lift.

Ref: https://www.researchgate.net/figure/Vortex-shedding-from-an-airfoil-oscillating-in-pure-heave-2_fig2_251006855
Using thin airfoil theory in incompressible flow, the lift coefficient for an airfoil undergoing cyclical pitching and/or heaving can be expressed as (Ref. Drela, Flight Vehicle Aerodynamics):
$$C_l=\text{Re}\{ C(k)C_{l_Q} + C_{l_A} \} + C_{l_0}$$
$C_{l_Q}$ is the circulatory part of the lift, which, at steady-state, is equal to $2\pi\alpha$. $C_{l_A}$ is the non-circulatory part that have to do with fluid inertia; at steady-state, its contribution would be zero. The last term is the camber contribution. $C(k)$ is the Theodorsen function, which serves as a complex gain on the circulatory part of the lift. $\text{Re}$ here refers to the real-part of the function, not Reynolds number.
The decrease in lift and lag is readily seen in the Theodorsen function, where $C(k)=F(k)+iG(k)$:

Ref: https://pdfs.semanticscholar.org/8457/c72b980f2f129a9f211617a5cdee4e162b75.pdf
The reduced frequency, $k=\frac{\omega c}{2V_\infty}$, denotes how many airfoil chord lengths per flow distance traveled in one motion period ($\omega$ is the angular frequency of the cyclic motion), and is a measure of how much the cyclical motion affects the flow on the airfoil. As $k \to 0$, there is no attenuation in lift and no phase lag; this is the quasi-steady aerodynamics. As $k$ increases, there is increasing attenuation in lift, up to 50%. The maximum phase lag occurs at $k \approx 0.25$.
For most rigid-body motions in commercial aircraft, the reduced frequency is low and the quasi-steady assumption is valid.


Is the old paint removed before applying a new one? I've heard that paint on large airplanes weigh 250+ kg.

When an aircraft gets a new owner, do they remove the paint that was previously on or simply paint over it?

If it is removed, how is it removed? What is the correct procedure for painting/repainting an aircraft?

Yes, paint imposes a significant weight penalty on larger aircraft. On commercial airliners, that weight translates to a reduction in cargo, passenger and fuel carrying capacity, and that means less money to be made on every flight. That is why some airlines have chosen to remove most of the paint and opt for the bare-metal look. However, there are tradeoffs to be considered, such as the fact that bare metal is much more susceptible to corrosion.

These days removing paint from an aircraft is a relatively straightforward proposition if you know what you are doing. There are a number of environmentally-friendly paint stripping chemicals available that when applied to the aircraft surface, cause the paint to bubble and lift off the underlying airframe.

The paint can then be scraped off with plastic tools or removed with a pressure washer, and the stripping chemical is washed off. Other products are then used to clean remaining residue, treat the metal for corrosion protection, prime and paint.

This explanation is intentionally simplistic, but it covers the basics to answer your question. If you want to see the process in action, you might check the many YouTube videos that show time-lapse recordings of aircraft being painted. Personally. I think they are fun to watch. :)


Can Savannah be stalled with agressive yoke pull? My friend fly ultra light Savannah, 2 seats plane,wings dont have slats ,it has vortex generators at leading edge.
He says that he cant stall plane with agressive yoke pull (I talk about speeds above stall-speed).
My question is this really true,why airflow dont separate from wing at high AoA and cause reduction in lift and sudden drop in altitude when pull yoke as fast you could?
He says plane just starts climb an that is what happend.

I have 500 hours in one, more or less... This one:

In my experience, if –with the engine at cruise, say 2/3 power– you start pulling the stick slowly, the machine does obediently pitch up, with no stall, but one has to be careful, and fast with the pedals. At the extreme, the airplane is pointing more or less to the zenith, and starts falling tail first while rolling, in reaction to the prop's torque. But it doesn't stall...
If you try the same gliding with the engine at idle, you won't be able to avoid a wing dropping down, more or less when the pitch reaches 30--40º...


What things can a passenger look out for, to indicate an emergency? As a passenger with a keen interest in aviation, I'd like to think I'd be eagle-eyed enough to spot a problem that the pilots mightn't be able to see, from where they're sitting (for example, an engine sputtering or ice on the wings).

What things can we look out for, sat in the cabin, that might ultimately save a plane?

Honestly, as a passenger, you're not really qualified to look for problems.  If you're a pilot qualified and with experience in that type then you might see something.

I've had passengers tell my flight attendants that they saw flames coming out of a seam in the engine cowling.  It was actually a section of orange rubbery material that was sticking out and flapping in the breeze.

Ice on the wings depends on the airplane too, you're often going to see some ice on the leading edges in icing conditions, and it's normal.  To know what's not normal, you have to have experience with that specific type.

There is actually one thing you could probably look for.  There are no airplanes that I know of that can safely take off with ice on the top of the wings (behind the leading edges).  That would be a legitimate thing to scream about; however, a pilot that would take off in such a case probably shouldn't be a pilot.

You can certainly ask questions about things you see, but don't phrase it such that you think you found a problem.

Window shades are requested to be open for take off and landing by some operators to allow the flight attendants to quickly assess the situation outside when directing an evacuation.  It has nothing to do with allowing passengers to look for problems.  Not all airlines have this policy either, it's somewhat uncommon, the first thing I do when I sit down at a window in the back is close the window, and it's rare that I'm asked to open it.


Why are the stabilised approach criteria different for an instrument approach and a visual approach? My question mainly pertains to the simple altitude difference. Why is the stabilised call given at 1000ft for an instrument approach and 500ft for a visual approach?

All instrument approaches are not alike. The Flight Safety Foundation Approach-and-Landing Accident Reduction Tool Kit, Section 5.1 — Approach Hazards Overview points out

Fifty-three percent of the accidents and incidents occurred during nonprecision instrument approaches or visual approaches (42 percent of the visual approaches were conducted where an instrument landing system [ILS] approach was available); …
Fifty-nine percent of the accidents and incidents occurred in instrument meteorological conditions (IMC); …

For a precision ILS approach, the ALAR recommends additional criteria in that the approach must be flown within one dot of the glideslope and localizer.
The thousand-foot gate is clearly driven by the worst case of a circling approach where the aircraft is not aligned with the runway, must transition off instruments back to visual flying, make the appropriate maneuvers, and land safely. Those all take time, so we should expect the recommendation to be at least as high as the visual approach.
In Section 7.1 — Stabilized Approach, we read

In addition, a stabilized approach provides

More time and attention for monitoring ATC communications, weather conditions and system operation;
More time for monitoring and backup by the PNF;
Defined flight-parameter-deviation limits and minimum stabilization heights to support the decision to land or to go around; and
Landing performance consistent with published performance.


Could a moving film of gas reduce aerodynamic drag? Source: Wikipedia
In this image there is depicted a system which creates, using the Coandă effect, a film of gas traveling along the surface of a body. If this object was moving through air in the "up" direction on the image, could aerodynamic drag be reduced since the gas at the boundary layer of the body would have lower velocity than the free stream air (in relation to the body)?

No, it doesn't reduce drag through reducing boundary layer speed, but it does create thrust by creating a region of low pressure in front of the vehicle (I mean technically, if the entire vehicle produces thrust, it does reduce vehicle drag, but in either case the reason why that happens isn't because the boundary layer speed is reduced). If you mount the device like in the image, then the low pressure zone will be created. The pressure at the bottom of the vehicle is higher than on the top, so it will generate forward thrust (well, in the orientation of the image, upwards thrust). This is because a jet of fluid will entrain it's surrounding fluid (aka "pull the fluid along with the jet"), which will create a region of low pressure around the jet. There actually are real-life implementations of this concept -

            ,

            .
However, the reason why this isn't used in real life is because if it's low efficiency - there's other ways to generate that thrust, such as using a propeller, a turbofan engine, etc, that don't require nearly as much fuel to produce the same thrust.


Center Controller with ADS-B question I don't know anything about planes (mechanics,electroinics,etc...) so bare with me (and the long post)!

In the USA

With ADS-B coming due in a few years, more GA are implementing their planes with ADS-B Out. They will call approach (who knows nothing about it) and in-turn they call us (center) for the answer. Or if they want to be "nice" they just have the pilot dial our frequency and the GA pilot will ask us (not fun sometimes).

All the GA pilot wants to do is verify with "FAA" that their ADS-B is working (center can see that it works, we have a button to toggle on and off). Once we tell them yes/no they are off the frequency. Sounds simple!!

The issue is Center, Tech-Ops, Supervisors.... don't know anything about ADS-B verification. I've taken upon myself to learn this in hopes to inform other controllers.

Questions~~~

What equipment do you have to have for ADS-B?
 Mode A/C transponder only or do you also need Mode S too?
Is ADS-B tied into Mode S or are they completely 2 different components?

Do you need a Mode S transponder to fly? (I think from what I read Part 121 ..commercial you do, but not required for GA if inside the US)

Does the ADS-B get registered to the N number or the air frame (not sure how you split that up)

What is an Example of an ADS-B "code" ? ....to clarify...If it is registered to the tail number, I would assume you have to register a specific "code" to tie the 2 together.

Is the ICAO hex number the same as the ADS-B number/code?

The reason I ask these question is for processing. A GA will call up and we will attempt to put in a flight plan mid flight (they pop up vfr and we try to work this out together) I tell them I need to give them a code to identify them and start a flight plan. I feel like when everything is entered, I am still missing something that needs to be entered to make sure the computer is aware the plane is ADS-B equipped. If it is tied to the tail number, once I create flight plan mid flight, it should auto acquire whether it is ADS-B equipped with no extra info input.

I ask about ICAO hex because I see some ADS-B equipped GA with hex numbers in the system and some do not have hex numbers but still verified ADS-B equipped. I want to know if they are both needed!!!

I also see Commercial flights with no hex number in the system too but I assume they all should.

Thanks, ZOB controller

What equipment do you have to have for ADS-B? Mode A/C transponder
  only or do you also need Mode S too? Is ADS-B tied into Mode S or are
  they completely 2 different components?

Either a mode S transponder with Extended Squitter (the ES broadcasts the ADS-s data) which broadcasts on 1090 mhz or a UAT (universal access transceiver) broadcasting only ADS-B data on 978 mhz. Both transmissions are received by FAA ground stations and the aircraft is placed in the ATC computer system where you see the ADS-B info.

  Do you need a Mode S transponder to fly? (I think from what I read
  Part 121 ..commercial you do, but not required for GA if inside the
  US)

yes, the advent of ADS-B does not change any requirements for transponders. Someday maybe but not now.

  What is an Example of an ADS-B "code" ? ....to clarify...If it is
  registered to the tail number, I would assume you have to register a
  specific "code" to tie the 2 together.

All ADS-B transmissions must output the same transponder code value that the pilot has dialed into the transponder. All ADS-B equipment has some sort of interface the determine Transponder code and that code goes along with the ADS-B transmission.

  Is the ICAO hex number the same as the ADS-B number/code?

ADS-B equipment broadcasts transponder code, ICAO hex, and the pilot's choice of flight ID or N number. There is something called anonymous mode and I'm not sure what's sent while in that mode.

  I ask about ICAO hex because I see some ADS-B equipped GA with hex
  numbers in the system and some do not have hex numbers but still
  verified ADS-B equipped. I want to know if they are both needed!!!

I've installed approx. 25 ADS-B units in small GA aircraft and every configuration I've seen has a entry for ICAO address. It's possible that you've seen improperly configured units or maybe there's something about it I don't know.

  @jScarry> I’m confused about your premise. Why would a pilot call ATC
  to verify

    that their ADSB is working?

The A in ADS-B stands for automatic so it works without any control input from the pilot whatsoever. Its just always on without having to actually turn it on. Consequently, he has no real idea whether or not it is working other than the possible absence of a fail message... so he calls ATC to ask him if his ADS-B is showing up or not. Most likely this is his first flight after the install and he just wants to know that he's showing up and that his $7k is actually doing what it's supposed to.


Why did flight attendants need to be seated early landing at Palm Springs? I took an Alaska Airlines flight to Palm Springs (PSP) and on landing the flight attendant mentioned that "this is one of the airports where we need to be seated early". Why is that the case for that airport, and what would be some of the other airports where that also happens?

I can't say for sure, but here's one plausible reason: Palm Springs is in a valley and surrounded by much higher terrain on three sides, which requires more maneuvering to land than at other airports. You can see on the VFR sectional that the airport elevation is 476ft MSL, but there are mountains over 8000ft within 10 miles of the airport. If you check the instrument approach plates for runway 13R/31L (it's the longer one, so most likely to be used by an airline), you can see that the flight paths are far from straight:

RNAV 31L

RNAV 13R

I can imagine the pilot would brief the cabin crew to be seated well before landing for safety while the aircraft flies the approach. Mountains often produce turbulence and high winds too, which would be another good reason to be seated while maneuvering at a lower altitude over that terrain.


Why does the FAA not support UL102 (formerly 100SF) unleaded av-gas as an alternative to 100LL fuel? The specifications for UL 102 are described in this Wikipedia article.  The fuel appears to exceed the specifications of 100LL in octane number and energy per unit volume although the fuel weighs 7 pounds per gallon instead of the 6 pounds per gallon for 100LL.  Is the additional weight the reason the FAA rejected this fuel as an 100LL alternative?

The problem is basically bureaucratic delays, helped along by easing of EPA timetables on the banning of leaded fuel, taking some of the pressure off, which has caused the developer of UL102, Swift Fuels, to suspend its 2nd Phase testing until the machine gets moving.


Can a private pilot obtain a recreational pilot certificate? While I'm thankful that third class medical reform has passed, I currently have a special issuance medical that the FAA has been reviewing for several months. This go around, they requested additional documentation further delaying the process.

I'm currently a private pilot. However, the aircraft I fly meets the requirements to be able to be flown by a recreational pilot. Looking at FAR 61.96, it doesn't look like I can "downgrade" my certificate with an additional recreational pilot rating per:

  § 61.96 Applicability and eligibility requirements: General.

  (b) To be eligible for a recreational pilot certificate, a person who applies >for that certificate must:

  (1) Be at least 17 years of age;

  (2) Be able to read, speak, write, and understand the English language. If the >applicant is unable to meet one of these requirements due to medical reasons, >then the Administrator may place such operating limitations on that applicant's >pilot certificate as are necessary for the safe operation of the aircraft;>

  (3) Receive a logbook endorsement from an authorized instructor who -

  (i) Conducted the training or reviewed the applicant's home study on the >aeronautical knowledge areas listed in § 61.97(b) of this part that apply to >the aircraft category and class rating sought; and

  (ii) Certified that the applicant is prepared for the required knowledge test.

  (4) Pass the required knowledge test on the aeronautical knowledge areas listed >in § 61.97(b) of this part;

  (5) Receive flight training and a logbook endorsement from an authorized >instructor who -

  (i) Conducted the training on the areas of operation listed in § 61.98(b) of >this part that apply to the aircraft category and class rating sought; and

  (ii) Certified that the applicant is prepared for the required practical test.

  (6) Meet the aeronautical experience requirements of § 61.99 of this part that >apply to the aircraft category and class rating sought before applying for the >practical test;

  (7) Pass the practical test on the areas of operation listed in § 61.98(b) that >apply to the aircraft category and class rating;

  (8) Comply with the sections of this part that apply to the aircraft category >and class rating; and

  (9) Hold either a student pilot certificate or sport pilot certificate.

Specifically (9). Is there a way I can exercise the privileges of a recreational pilot? I'm willing to take another knowledge test / checkride. Thanks!

Not technically.

You could opt to surrender your private pilot certificate to the FAA thus making you not a pilot, and then you could take a checkride for recreational.

Of course, there is no reason to do this at all!  You can do the same things as long as you're exercising the privileges of the lower certificate, then whatever medical rules are there should only apply for that operation if I'm not mistaken.


What is the shape of the power required curve? I understand that when flying level, some power is required to maintain altitude, this power amount being:

Normally larger when the speed is larger, this is flying on the forward side of the required power curve.
But below the minimum required power, this amount of power needed to maintain altitude goes down when speed increases. This is flying the backside of the curve.

This can be represented like this:

Being on the backside of the curve means flying in an area of strong instability, possibly reaching the stall point if not managed correctly.

Question: What is the shape of this power required curve for a small GA airplane, and for a large commercial airplane?

I mean is the backside a small portion where it is unlikely to be without obvious pilot mistake? (left hand side below) or is it a large area where it is easy to fall? (right hand side)

What is the shape of this power required curve for a small GA airplane, and for a large commercial airplane?

The answer depends on the span loading and flight altitude of the aircraft. For most practical cases, the left hand side power curve is more realistic, but it still can be entered if the pilot is unaware of what he/she is doing. Just witness AF447 …

The power curve is the sum of two drag curves, times flight speed:

The induced drag is dominant at low speed and decreases with increasing dynamic pressure, and
the friction (and parasitic and interference) drag grows with increasing dynamic pressure.

Below I have plotted the theoretical power curves for a small GA airplane at sea level. The dashed lines show the power curve if no flow separation would happen.

Aircraft with low span loading will exhibit low induced drag, so the friction drag (zero lift component) will become dominant soon. The higher the airplane flies, the more the available power is reduced and the induced drag is increased, so the power curve will shift to something resembling your right plot. The point splitting the left side of the curve from the right side is the point of minimum power. Where is this point for actual configurations?

We can calculate the lift coefficient at minimum power in order to know where the speed range of the backside of the curve starts. In this answer, I derived this already, so here is only the result:
$$c_{L_{min.\:power}} = \sqrt{\frac{2-n_v}{n_v+2}\cdot c_{D0}\cdot\pi\cdot AR\cdot\epsilon}$$
The symbols are:
$\kern{5mm} c_L \:\:\:$  lift coefficient
$\kern{5mm} n_v \:\:\:$  thrust exponent, as in $T = T_0\cdot v^{n_v} $
$\kern{5mm} c_{D0} \:$  zero-lift drag coefficient
$\kern{5mm} \pi \:\:\:\:\:$  3.14159$\dots$
$\kern{5mm} AR \:\:$  aspect ratio of the wing
$\kern{5mm} \epsilon \:\:\:\:\:\:$  the wing's Oswald factor, normally between 0.8 and 1.0

Now let's input the values for a glider ($n_v$ = -1):
$$c_{L_{min.\:power}} = \sqrt{3\cdot 0.00935\cdot\pi\cdot 21.43\cdot 0.98} = 1.36$$
So the minimum power speed for the ASW-20A is very close to its stall speed. Falling into the backside is practically equivalent with stalling.

Now the values for a jet fighter ($n_v$ = 0):
$$c_{L_{min.\:power}} = \sqrt{0.0172\cdot\pi\cdot 2.45\cdot 0.76} = 0.317$$
So the Starfighter pilot is on the backside of the curve until he accelerates beyond 191 m/s or 371 knots (at maximum take-off mass). That is already Mach 0.54 at sea level (and more the higher you go), and explains why the Starfighter prefers to be flown fast. Its best climb speed is at Mach 0.9!

Since you asked about a commercial airplane, here we go:
$$c_{L_{min.\:power}} = \sqrt{1.67\cdot 0.01277\cdot\pi\cdot 9.58\cdot 0.74} = 0.687$$
This is for the clean configuration of course and falls between the glider and fighter values. The numbers for a GA aircraft are a little higher (around $c_L$ = 1) due to the piston engine, with a higher Oswald factor due to an unswept wing and a somewhat lower aspect ratio. Commercial aircraft prefer to cruise close to the minimum drag point, which for this example is at $c_{L_{min.\:L/D}}$ = 0.532, so at altitude their operating point is already quite close to the backside range. In contrast to that, a GA aircraft in cruise will fly low (no pressurisation) and much faster that at its minimum power, so its cruise point will be far to the right of the backside range, making the power curve look more like your left hand side example.


How to modify an amateur kit build with wing hard points I plan on modifying an amateur-built all-metal kit plane so it has a hard point under each wing where various external loads (cameras, probes, etc) can be fitted to (university research). The location would be approximately mid-wing. The aircraft in question is a Sling 2. It will be registered in Germany as an experimental with a permit-to-fly.

I was unable find any resources on how to tackle this engineering problem on small aircraft. The resources I have access to are all for large aircraft and are somewhat "oversized" in my opinion.

We are talking external loads up to about 5 kg (11 lbs) in mass.

An aerodynamic envelope expansion will be needed for each external load but how do I design the wing for it?

Edit: I found a builders log of a 75% Tucano-R Replica who did this, however there is no explanation on the engineering part. It looks relatively straightforward with just two thicker plates attached to a rib.

You will most likely need a Supplemental Type Certificate from EASA

According to their FAQ, emphasis mine:

  My aircraft has been modified in the USA by Form 337 action. Can EASA accept this?

  Answer

  EASA accepts alterations on non-critical components that are substantiated via Form 337, as detailed in the EASA-FAA Technical Implementation Procedure (TIP) rev 5, paragraph 3.2.8.2 EASA Acceptance of FAA Alteration Data:

  “Except for alterations on critical components, FAA-approved or accepted alterations per 14 CFR Part 43 installed on a used aircraft exported from the U.S., regardless of the State of Design of the aircraft, are considered approved by EASA at the time of import to the European Union. EASA shall accept such FAA alteration data when substantiated via an appropriately executed FAA Form 8110-3, FAA Form 8100-9, FAA Form 337 or logbook entry.

  Alterations on critical components must be EASA-approved via STC, in accordance with TIP paragraph 2.2 (Design Approval Procedures for Supplemental Type Certificates (STCs)).

  An FAA STC whose installation is documented on a Form 337 must be approved by EASA in accordance with TIP paragraph 2.2.”

From the aforementioned TIP:

  2.2 Design Approval Procedures for Supplemental Type Certificates (STCs).

  2.2.1 Scope of STC Application Acceptance.

  2.2.1.2 EASA may accept applications
  for STCs for:

  (a) All STCs (Basic and Non-Basic) when the original STC application is made to the FAA:

  (1) On products for which EASA acts on behalf of the State of Design,

  (2) On U.S. State of Design products, and

  (3) On third country aircraft which have been type certificated by both EASA and the FAA.

So you should be able to apply per point 2.2.1.2.a.3, assuming of course, that the aircraft is certified by EASA and not operated within Europe as an experimental with a Permit-to-Fly.

In light of the above, and considering that a modification of the wing to carry an external load is not likely to be classed as non-critical, you should probably contact both EASA and the Design Organization for the type.

Alternatively, you could look into moving the aircraft into the experimental category

In this case you will need a Permit-to-fly, more info here:

  The European Aviation Safety Agency (EASA) is responsible for the approval of flight conditions. Such an approval is the basis on which a Permit to Fly (PtF) can be issued by the Competent Authority of the State of Registry, or of the State prescribing the identification marks of an aircraft.

  A PtF is generally issued when a certificate of airworthiness is temporarily invalid, or when a certificate of airworthiness cannot be granted, but the aircraft is nevertheless capable of performing a safe flight.

  Please use EASA Form FO.CERT.00037 (with EASA Form 18B in the annex) to apply for approval of flight conditions at EASA. With the approved flight conditions (EASA Form 18B) you can apply for a Permit to Fly at the local national aviation authority the aircraft is registered.


Which Aircraft Models need a Tripod Jack for tail support at airport? Which are the aircraft models that need their tail to be supported by a jack when empty?

Wikipedia says this:

  Aircraft Tripod Jack

  They are used to support a parked aircraft to prevent their tail from
  drooping or even falling to the ground. When the passengers in the
  front get off an aircraft, the aircraft becomes tail heavy and the
  tail will droop..... When needed, they are tugged to the tail and
  setup by manpower. Once setup, no supervision to the jack is needed
  until the aircraft is ready to leave.

Are there even commercial airliners that need to be supported this way every time they load / unload? Sounded like a lot of work for ground staff. Was this a legacy equipment thing or still in use today?

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

Tripods are mostly found in cargo aircraft (and combis) as the cg shift is severe there (particularly for front loading). A good example is the Boeing 747s. Also used in DC10/MD11s used as freighters.

Image from reddit.com

Some 747-400 combis also use these, though it is mainly for cargo loading.

Photo: Je89 W. / Source: PlanePictures.Net

Some passenger airliners are prone to tipping (737-900 comes to mind) and are usually supported by a pole rather than by a tail stand (same procedure is used in a KC-135 tanker too). For example, a Boeing 737-932ER with tail support.

Image from airliners.net

The tail supports are not strictly necessary and the loading can be carried out sequentially (from front to back) for safe operation, but are used as a  precaution. In some aircraft (like ATR-72 and Saab 340, called pogo sticks) small tubings are attached to the rear fuselage to prevent tipping over when loading/unloading.

Image from theflyingengineer.com

The nose can be tethered to prevent tipping during loading/unloading as done in this Korean Air 747F

Image from koreanair.com


Does ICAO require (or suggest) set of technical statuses of radar and its subsystems? Does ICAO require (or suggest) set of technical statuses of radar and its subsystems? In other words is it required that radar status can be set to Normal, Warning and Error, or Idle, Alarm, Unknown also possible? There are 002 and 034 categories of ASTERIX which describe messages about radar status, but I haven't found out answer on my question.

These statuses are not defined by nor required explicitly by ICAO.

The details of how a radar (or other surveillance) system communicates with downstream ATC systems are defined in a technical specification documents, typically produced by EUROCAE and/or RTCA.

The ASTERIX specifications are maintained by EUROCONTROL and only give the format in which surveillance ground systems communicate amongst each other. The specifications were originally intended to facilitate surveillance data exchange between European countries, but they have now been adopted by many countries outside Europe.

Category 002 (old) and 034 define the status messages monoradar systems use to update downstream systems (radar trackers, displays) on the radar's status.


What does NSC mean in a METAR? Here's a METAR:

  SCEL 090000Z 15005KT 5000 HZ NSC 10/08 Q1020 NOSIG

What does NSC mean?


Has the F-35 Lightning II overheating problem been resolved? This is one of the sources explaining the F-35 overheating problem. Has this been resolved?

Are the constant problems, that are being reported about this type normal for an aircraft like this?

As to the first question, it appears as fuel cooling of electronic components and other equipment is integral in the F-35 design, all branches of the armed services will not be able to remedy this problem and it will have to be solved with only fueling the aircraft with cold fuel.  The Air Force has opted to use fuel trucks painted white in order to keep fuel cool while on the ground and it may require refrigeration equipment in fuel tank farms at F-35 bases at an additional cost to the program.

The fuel problems for the F-35 are but one of several hundred faults, shortcomings and outright vulnerabilities with the troubled Joint Strike Fighter program.  While developmental issues are common in new aircraft programs, none so far have been this serious, so numerous and so overbudget without being killed.


Does the B-1B Lancer have controllable canards? These three pictures shows the B-1B Lancer's canards and its elevators. I am not sure to call that feature a canard as the jet also has elevators. In my limited understanding, canard and elevator are substitutes, to use canard or elevator. Then my questions are:

What is that feature's name? Is that canard?
Is that feature (specific to the B-1B) also controllable like elevators?

Picture source 1 and 2: captured from this Youtube video.
Picture source 3: from here.

From Wikipedia:

  The Rockwell B-1 Lancer has small canard vanes or fins on either side of the forward fuselage that form part of an active damping system that reduces aerodynamic buffeting during high-speed, low altitude flight. Such buffeting would otherwise cause crew fatigue and reduce airframe life during prolonged flights.

Having a traditional tailplane does not exclude the use of term canard, but it must be admitted that in the case of B-1B the forward control surfaces are so small in relation to other lift or control surfaces that the term "fin" might be more semantically appropriate.

B-1B Canards are moving, but not pilot controlled:

  The B-1's Structural Mode Control System rotates the [canard] vanes automatically to counteract turbulence and smooth out the ride.

Wikipedia: Canard (aeronautics)

Wikipedia: Rockwell B-1 Lancer


Are military and passenger jets insured? Are aircrafts insured? Basically, I want to ask who bears the financial liability in case of some mishap? The airline company/government or some other company.

A partial answer for the case of military peacetime accidents: the government concerned seems to take responsibility for compensation - a few examples:

Cavalese cable car disaster (1998)
2012 Virginia Beach F/A-18 crash


How do check valves regulate the air in a multi-engine airplane's vacuum system? This is one of the examples of a pneumatic power system in a multi-engine airplane. In systems like this, if one dry air pump fails - let's say the right-hand one - then the check valve manifold closes the right-hand part of the system. I can understand this and it makes sense, but I can't understand how the check valve manifold works.

I already went through an aircraft maintenance manual which has kind of this system, but I can't find any clue. My instructor guesses that inside the check valve manifold there's some kind of shuttle valve. But I don't agree with this. Could someone help me out to understand?

On each side of the check valve manifold there is a check valve that only allows air to flow toward the vacuum pump on that side.  For the left pump, the check valve is the rectangular bit between the far left line going to the vacuum gauge and the adjacent line going to the deflate valve, and for the right pump it is between the far right line and the gyro suction line.

The result is if one vacuum pump no longer is producing suction, the vacuum gauge indication on that side, being "upstream" of the check valve now that only the opposite pump is pulling air, will show no vacuum; meanwhile the operating pump can still pull air through the other three lines and can still operate the deflate valve and vacuum gyros.  Its vacuum regulator will control the vacuum level.  Everything will continue to work normally with only the loss of vacuum indication for the failed pump providing an indication that something is wrong.


How are flight schedules displayed without ambiguity on DST change days? Flight schedules are based on the local time of the station of departure or arrival. Twice a year though, this is either ambiguous or impossible. What happens on these boundaries?

Say, for instance, a flight is scheduled for departure daily at 1:30 A.M. This year, DST ends at November 2nd, 2 A.M., meaning the local clock will go from 2 A.M. back to 1 A.M. Will this flight depart on the first 1:30 A.M. or the second?

And the other way round, say next year a flight is scheduled for departure daily at 2:30 A.M. When DST starts, the clock will go directly from 2:00 A.M. to 3:00 A.M. and 2:30 doesn't exist. What happens for this flight?

It's only really ambiguous once a year, when moving from summer time to winter time and the hour is 'repeated' - in this case, departures and arrivals are scheduled in the 'first' instance of the hour: eg if the flight is scheduled 01:30, it will depart 1.5 hours after midnight. The clock will then go back eg at 2am, and the airport will be relatively for one hour with no departures (although, of course, arrivals may still come in)

On the other shift, the hour is 'lost' so the departure takes place later. In practice, no planes are scheduled to arrive or depart in this missing hour, and since almost all nations make the change in the middle if the night when airspace is very quiet and most airports have no departures at all there is virtually no knock-on effect. Arrivals arrive when they arrive, departures are simply scheduled for a 'real' hour, if there are even departures at all at that time of day anyway.

Note that this is only for passenger scheduling - in air traffic control etc all times are Zulu (UTC) which has no ambiguity.

TL;DR: Fall/Autumn, aircraft depart in the "first" instance of the hour. Spring: scheduling works as usual, but with no flights scheduled in the "missing" hour (eg 2-3am)


Why isn't luggage that goes in the hold scanned as thoroughly as hand luggage? I'm a regular international flyer, my hand luggage is always scanned, and despite my best efforts it often gets searched, either due to mistakes on my part, or security being extra cautious. On my most recent flight I estimate about 5-10% of my fellow passengers also had their hand luggage opened and searched by hand.

On the other hand, I have never had any issues with checked in luggage, I've never been pulled to one side and asked to explain anything, and as far as I can tell my luggage has never been searched (unless someone has picked the lock and then been very tidy in re-packing it)

So, my guess is that either 1) checked-in luggage isn't scanned as well as hand luggage, or 2) checked-in luggage is scanned by some super-hi-tech scanners that are infallible in identifying suspicious devices and never need checking by a person.

If the answer is option 1) then why doesn't checked-in luggage need such a thorough check? What's stopping a bad-guy putting a couple of kilos of something dodgy into his bag that brings down the aircraft over the Atlantic?

If the answer is option 2) then why can't the infallible super-hi-tech scanners be used on hand luggage too so no-one ever needs to be pulled over for a manual search?

The main reason why checked luggage is treated differently is that you cannot access it during the flight, therefore eliminating some of the security concerns (like e.g. a knife in checked baggage is not a risk). When your carry-on bag is hand-searched, it is most likely because something could not be seen properly or looked suspicious on the X-ray.
The checked baggage is still scanned though. The TSA writes:

TSA screens approximately 1.4 million checked bags for explosives and other dangerous items daily. Upon check in, your checked baggage will be provided to TSA for security screening. Once the screening process has completed, your airline will transport your checked baggage on your respective flight as well as deliver it to the baggage claim area. The majority of checked baggage is screened without the need for a physical bag search.
Inspection Notices: TSA may inspect your checked baggage during the screening process. If your property is physically inspected, TSA will place a notice of baggage inspection inside your bag. This is to inform you that an officer conducted an inspection of your property.

Note that the TSA will notify you with a notice in the bag when they opened it. Other countries might handle this differently and just open the bag without telling you.
Some more details of the screening process are given in this article (emphasis mine):

Soon after your suitcase vanishes behind the rubber curtain, it merges with the bags of other passengers -- in large airports, thousands an hour. After traveling up, down and around a vast network of high-speed conveyor belts, it arrives in a cavernous warehouse-like facility. Here, it will be scanned by Transportation Security Administration staff to make sure there's nothing in it that shouldn't be there, primarily explosives, illegal drugs or weapons. If they see any reason to open it, they will. Your bag might also be subjected to other checks, including sniffer dogs, X-ray and laser scanners and machinery designed to detect trace amounts of banned substances. If it passes muster, luggage handlers load your suitcase onto a wagon with the baggage of others on your flight. This wagon is driven onto the tarmac and its contents packed into the hold of the plane.


What rate of descent would kill you? I was watching a video where a plane an MD-82 descended 18,000 feet per minute and crashed into a mountain.
The plane was not upside down/on its side/spiraling- it had about a 5 degree pitch up the whole time.
My question is: Would this rapid descent kill you, or at least make you pass out? What is the descent rate that would simply just make you go unconscious?

There is no descent rate that would directly kill you or make you pass out, the notion is nonsense from a physics standpoint. It may be possible to rupture eardrums from the pressure change in some people with pre-existing sinus and ear trouble. It would also be possible to die from the heat of air speeds over mach 2, but the exact speed depends greatly on the aircraft design and is not unique to a descent trajectory.


What were the historical safety statistics of airplanes? There's lots of debates in the Space world about the safety margins of modern rockets (specifically the fact that the ITS isn't planned to have an abort mode as (in the words of many SpaceX supporters), it "should be as safe as airplanes").

Now, I know that modern airplanes are crazy safe (as in, the last fatal crash of a major US airline in the US was just a month after 9/11), but I presume that back in the 1920s seats on airplanes were sold commercially without passengers having an abort mode either, and those airplanes were much less reliable than modern ones.

How has the accident per flight statistics changed throughout aviation history?

Accidents "per flight" is unfair when comparing a 10-passenger Ford Trimotor
to an 853-passenger A380.  Passenger miles is fairer.
Even fairer is accidents per passenger, ignoring miles,
because takeoff and landing have always been more accident prone than cruise.
But even easier to measure historically is fatalities per passenger.
Commercial airline travel as we recognize it started in 1926.
http://www.planecrashinfo.com/1926/1926.htm
reports 36 fatalities worldwide that year.
1926 had about 6000 passengers in the USA.
Luft Hansa probably had more. Let's generously guess 20000 worldwide.
So the fatality ratio was about one in 550.
In 1930, 385,000 passengers were "carried on domestic and foreign airlines under the American flag".  In 1935, nearly, 1,000,000 (Berkeley Daily Gazette).  PlaneCrashInfo in these years veers away from airliners, though, and I couldn't find reliable global crash or fatality info for those years.
During World War II, and immediately preceding and following it, statistics about nonmilitary air travel are bound to be noisy.
From 1950 to 1970, per-year fatalities went from about 1,000 to 1,500
(with a dip in 1955).
Over that same interval, per-year passengers went from roughly 50,000,000 to 500,000,000.
So fatalities per passenger dropped from 1950 one in 50,000
to 1970 one in 333,000.
That second figure is corroborated by another source:
The "fatality risk per boarding" in 1968-77 was one in 350,000.
In 1978-87, one in 750,000.
In 1988-97, one in 1,300,000.
In 1998-2007, one in 2,700,000.
In 2008-2017, one in 7,900,000.
-- A. Barnett, "Aviation Safety: A Whole New World," Transportation Science 54(1), 2020.
https://doi.org/10.1287/trsc.2019.0937 paywalled;
summarized at http://www.sciencedaily.com/releases/2020/01/200124124510.htm


Does DO-178C require static code analysis for level A software? Does DO-178C have any guidelines on using static code analysis for level A software?

As per Do-178C:

  Section 6.3   Software Reviews and Analyses
  Reviews and analyses are applied to the outputs of the software development processes. One distinction between reviews and analyses is that analyses provide repeatable evidence of correctness and reviews provide a qualitative assessment of correctness. A review may consist of an inspection of an output of a process guided by a checklist or similar aid.

  An analysis may examine in detail the functionality, performance,
  traceability, and safety implications of a software component, and its
  relationship to other components within the system or equipment

Can this achieved by Static analysis ? Some of the tools like polyspace which has misra standard checks

DO-178C is a means of compliance, so it sets out what you need to do to show you are meeting your required safety levels in your design.  It does not give advice on what methods you might use along the way.

I have seen static analysis used as part of the process, often with hardware integration and system testing.

DO-178 tools need to be qualified for DO-178 if you are using them to test your software.  I am not aware of anyone successfully using tools qualified for other standards (e.g. MISRA) in avionics.


Which regulation requires me to report entering a hold? I have seen in many bulletin boards that a pilot is supposed to report upon entry into a holding position.
I can find that reporting nowhere in the regulations .
I can find in the regulations where a pilot must report leaving a hold at expected clearance time,  and at that time he is supposed to report time, altitude, and position, and the fact that he is leaving the holding position.
Where in the regs does it show that you must report upon hold entry?

So, this is found in the AIM, para 5-3-3 (a)(1)(f) (PDF), assuming you're asking about FAA regulations.

  5-3-3. Additional Reports

  a. The following reports should be made to ATC or FSS facilities without a specific ATC request:

    1. At all times.

      [...]

      (f) The time and altitude or flight level upon reaching a holding fix or point to which cleared.

      (g) When leaving any assigned holding fix or point.

Now, the AIM is not regulatory. It uses terminology like "should" instead of "shall", which lawyers will happily jump on, and it in fact says this about itself:

  This publication, while not regulatory, provides
  information which reflects examples of operating
  techniques and procedures which may be requirements
  in other federal publications or
  regulations. It is made available solely to assist pilots
  in executing their responsibilities required by
  other publications.


Is PVC tubing a good material for helicopter airframes? Been thinking of getting into the hobby of building ultralight helicopters, and would PVC tubing be a good choice to build the overall airframe?

No. The strength to weight ratio of PVC is poor compared to aluminum and you would end up with a very heavy, albeit cheap, machine, and will be even worse when compared to carbon fibre tubing, which would be the optimal choice performance-wise.  Extruded aluminum tubing would likely be the best choice cost wise.  Forget about building a plumb-O-copter.