Manufacturers are narrowing seats. Any possibilities for price cut?

You will likely not see a price cut, but you also might not see a price increase.

Seat pricing (along with just about any other service in a competitive market) is a complex function of actual cost to the company + desired profit + market factor. The last one is the difference between what they want to get and what the market is willing to pay. It is sometimes negative.


Why does the autopilot disengage even when it does not receive pilot input?

The "autopilot" is a fairly basic control system. Usually it is composed of just a few components (logically speaking) like a wing-leveler, heading mode, and altitude mode. The autopilot can control the aircraft usually through servo's connected to the control cables or through the hydraulics. External systems can feed into this to do things like follow a descent path, follow GPS/VOR routes, etc. The autopilot itself is basic.

The autopilot is designed to fly an aircraft that does not otherwise have any other issues. The autopilot is not designed to fly outside of normal operating circumstances. This means that when some kind of abnormality is detected (usually through the autopilot hitting its programmed limits) it will automatically disconnect.

In the Learjet case you cited, the autopilot continued to maintain altitude after the engines failed, but because maintaining altitude without engines means your speed will decrease, the autopilot disconnected before the aircraft stalled rather than fighting the pilot through a stall. It assumes that it is safer to automatically hand-off than require the pilot who is now trying to stabilize the aircraft to also have to worry about disconnecting the autopilot.

Most autopilots give some kind of warning that they've disconnected. This can be things like a chime, voice alert, stick shaker, etc. It's the autopilots way of saying "I've reached the limits of what I can control, you need to take over now". Otherwise it could potentially make a situation much worse.

The cornfield bomber was not on autopilot when it crashed. It just regained stability as a result of the ejection and remained on a fairly level (but descending) path until it bellied into a field (and continued to run/move for quite some time).


Where I can get historical jet fuels prices?

U.S. Energy Information Administration keeps tabs on most refined and crude prices including kerosene-type jet fuel. For those who hail from metric units' land, these are in dollars per gallon.


Why is the A380’s with-reversers stopping distance the same as its no-reversers stopping distance?

In all Airbuses auto-braking system aims for specific deceleration. Once the design target has been reached, the system does not apply more brake pressure although there usually is more available. So, if you apply thrust reverser with autobrake selected it will apply less pressure on wheel brakes and as the target deceleration remains the same, the stopping distance remains unaffected.

On slippery runways the autobrakes apply brakes until anti-skid starts to limit the brake pressure so in those conditions reverser would shorten the stopping distance. This would also apply to rejected take-off where maximum braking is commanded.


How do airliners cross the ocean without GPS?

Well, most airlines do cross the ocean with GPS in today's world.

That being said, most (if not all) transcontinental airliners, and many flying domestic routes as well, have what's called an inertial navigation system (a form of dead-reckoning where gyros and accelerometers are used to compute changes in position). The INS feeds into the flight management computer which is used to cross-check the GPS position, and can be used as a primary navigation source should the GPS signal be lost or corrupted.

Prior to GPS, inertial navigation was the primary means of navigating across oceans. However, a great many airplanes did cross oceans before INS... with varying success. The general idea was to use a combination of dead-reckoning, radio beacons where you can find them (small islands and coastlines), the sun (with the help of a sextant) during the day, and the stars at night. Hopefully, this puts you in position after some period of time to pickup ground-based navigational aids, or to identify a coastline. This actually works pretty well if your wind estimates are good, and the margin for error is high enough. As DeltaLima points out, long-range radio navigation systems also started to emerge around World War II (LORAN and Decca) which had a much greater range than previous radio beacons, and therefore decreased the amount of time required to fly by dead-reckoning alone. By the time inertial navigation became prevalent in the 1970's, airlines were already providing reliable transcontinental passenger flights every day.

Another possible outcome is that your plane is lost in the ocean, never found, and the Discovery Channel funds an expedition to look for you 75 years later.


How to determine the MAP for an RNAV MDA approach?

The Missed Approach Point (MAPt) is at the runway threshold. The other reference you will see on this RNAV chart is the Visual Descent Point (VDP), at 1.1NM RWY05R, which is at the Minimum Descent Altitude (MDA).

  The concept of VDP was developed by the FAA to encourage pilots to decide to initiate a missed approach prior to reaching the MAP, in a situation where the runway or its environment is not visible at a normal descent angle. Conversely, if the runway is visible at the VDP, the pilot may continue descent, following a standard descent angle to the runway, while being assured terrain and obstacle clearance.[5] The VDP is always located prior to reaching the MAP, and is a more useful checkpoint for making the decision whether to continue on the approach or to go around than the MAP itself.

(Source: WikiPedia)

If the MAPt is intended to be elsewhere, it will be assigned its own identifier.

  "The missed approach waypoint is assigned a pronounceable name when it is not located at the runway threshold."

(Source: AIM 5-4-5.d.5(d))

(Source: www.faa.gov)


ETOPS stands for Extended-range Twin-engine Operational Performance Standards, a rule which permits twin engine aircrafts to fly routes which, at some point, is more than 60 minutes flying time away from the nearest airport suitable for emergency landing. ETOPS may also be interpreted as Engines Turn or Passengers Swim.
It is not a rule which applies after an engine has failed. Rather, it is a set of regulations and standards which must be met if an airliner wishes to fly its planes more than 60 minutes away from a suitable emergency airport.
History
Early combustion engines were noticeably unreliable. It was not uncommon for a 4-engine piston aircraft to arrive at its destination with only 3 engines running. Twin engine aircrafts, as a result, were required to fly dogleg paths to stay close enough to an adequate airport.
Aircrafts with more than 2 engines were not restricted by this rule. Thus, many transatlantic flights were flown with Boeing 747s and L-1011s, since airliners can fly a more direct route with these aircrafts.
As engineers gained more experience in jets, they slowly recognized that jet engines are much more reliable than their piston counterparts. The FAA began to approve flying twin engines 120 minutes away from a suitable airport. This made twin engine aircrafts popular, because the fuel efficiency of flying a twin is much better than flying a 4-engine 747 or A340.
Certification
ETOPS certification requires both the aircraft and the airline to comply with a set of standards.
For the aircraft, the manufacturer must demonstrate that flying with only one engine is relatively easy for the flight crew, safe for the airframe, and an extremely remote event.
The airline must demonstrate that its flight crew training and maintenance procedures are up to a higher standard. Pilots, engineers and staff must be specially qualified for ETOPS.
Recently, more operators are adopting the ETOPS approach to non-ETOPs routes. They discovered that the approach offers significant improvements in reliability, performance and dispatch rates. The cost of application is later offset by reduced maintenance costs, and costs associated with diversions, delays and turn backs.
Flight Plan
An ETOPS flight plan may look something like this:

Let's say the aircraft's ground speed (with one engine inoperative!) is 450 knots. By drawing circles with radius 450nm around alternate airports, we can obtain areas which the flight must stay within. The flight path always stays inside one of these circles. If we are operating under ETOPS 120, we will draw the circles at 900nm.
Actual flight plans are slightly more complex, since winds aloft (sometimes more than 100 knots) will affect the aircraft's ground speed. Dispatchers use software to calculate a route, taking aircraft weight, fuel consumption and winds into consideration.


Why does the MiG 21 use anti surge shutters?

Normally, such shutters are close to the intake and covered by simple spring-operated doors which open when the pressure in the intake duct drops below ambient pressure at low speed.

AV-8B air intake (picture source). The upper two doors are open while the lower three are closed.

The ideal area of a jet intake varies with flight speed. At low speed, it needs to be large so the amount of air swallowed by the engine can be supplied without too much resistance. At high speed, a big intake captures and compresses more air than the engine needs, which increases drag. Especially fighter jets need an intake which is optimized for high speed flight, and in consequence much of the engine power is needed to suck in enough air during the take-off run. Adding doors which are sucked open in that condition will add another pathway for air to reach the engine, which in turn will help to avoid a compressor surge and improves thrust at low speed.

I have no detail knowledge of the MiG-21 intake, but it appears to me that the anti-surge doors are only open at low speed and high engine RPM. At high speed, the pressure in the intake duct is a lot higher than the ambient pressure and the doors are firmly closed.


Why does fuel vaporize in the carburetor?

Vaporization is closely related to the concept of volatility, which in turn is directly tied to the vapour pressure of a substance.

The vapour pressure of a substance is a function of temperature, and is the pressure at which a room filled with some liquid (or solid) and some gaseous parts of the substance are in exact equilibrium. Increase the pressure, and some gas will want to condense; decrease the pressure and some liquid will want to evaporate. For fuels, this is in the order of tens of kPa (e.g., the Reid vapour pressure of avgas, which is the vapour pressure at 37,8°C, is ~38kPa).

If we assume that air is an ideal gas, we can say that liquid fuel and gaseous (evaporated) fuel are in equilibrium when the partial pressure of liquid fuel equals the vapour pressure of the fuel. Since the partial pressure of the constituents of a gas are directly tied to the molar quantities of a gas, we can easily extract the fuel-to-air ratio. Given that the partial pressure of oxygen is about 21kPa (which will only decrease if you add fuel, assuming this happens with constant atmospheric pressure), we can easily see that if you leave a tank of air and fuel (with a vent to keep it at atmospheric pressure) long enough for the fuel to reach equilibrium, you have a very rich mixture indeed.

So, we limit the amount of fuel entering the carburetor to close to stoichiometric (exactly enough oxygen and air). As per above argument, all of this fuel will eventually evaporate as the vapour pressure is much higher than the eventual partial pressure reached by the gaseous fuel. The only question that remains now is how fast we can evaporate all this fuel. This only happens at the surface of the liquid fuel, so the trick here is to maximize this surface area. This is done by spraying the fuel into tiny droplets, each of which has a large surface area compared to its volume (remember, area scales with the size squared, while volume scales with size cubed - if you make the droplets smaller, the volume will decrease more rapidly than the surface area). They will thus be fully evaporated before they reach the actual cylinders. The smaller the droplets, the quicker this happens and the better mixed your fuel will be into the air.


Do they wait until all aircraft have landed before winding up an airline?

The article speculates based on a single precedent:

  It's likely (looking at the precedent of Monarch's collapse) that any announcement about that will be made late at night, once all planes are on the ground.

But evidently that's not entirely the case. Thomas Cook ceased trading at 0109 UTC of the 23rd, with some of its planes still in the sky:

(Flightradar24) Showing only TCX callsigns.

As you can see, some of them are long-haul returning from USA. I also could not correlate last departure time with the announcement. The latest I found was at 1131 UTC (MT2643 from Orlando to Manchester).


When might a pilot hand-fly a jet at cruise altitudes, and is it difficult?

For 747-100 and -200 aircraft at 35,000 ft and above, you can do it, but it's hard to keep the airplane within 100 feet of the assigned altitude, and you typically can't do that (or at least I couldn't) without practice. 200 foot altitude excursions were the norm when I first took control if I had not done it for a while. For the few first officers that accepted an invitation to try it, an initial 300 foot altitude excursion was typical when they first tried it, especially immediately after disengaging the autopilot.

I found the concentration required was very tiring. Ten minutes was typically enough to satisfy the urge.

Insofar as when you might want to do it, I found hand-flying produced a smoother ride in heavy to severe turbulence than the autopilot's turbulence mode, which tended to try to keep the assigned altitude and aircraft pitch too slavishly.


What would happen if a takeoff is not rejected following an elevator malfunction?

There are a number of scenarios that I can see happening, most of which depend on the aerodynamics specific to the aircraft.
Scenario 1: Nose Down Force > Up Force
I believe this to be exactly what happened in this instance. What happens is that the downward deflected elevator overpowers the upward deflected elevator creating more down force than up force. This means that the pilot can't rotate the aircraft into a climb attitude. This seems the most probable otherwise the pilots would have lifted off after V1 and went around.
Scenario 2: Nose Down Force < Up Force
If the pilots were able to get the aircraft into the air, and the asymmetric elevator didn't act like ailerons, they would probably have noticed that the aircraft would easily pitch down but be very difficult to pitch up. They would have noticed that as they got faster, pulling back on the stick would have resulted in less of a pitch up. Depending on the pilots, if they noticed this quick enough they could reduce power and control it for a landing. If they didn't realize what was going on and remained at TOGA power, they may have pitched into a stall.
Scenario 3: Extra Ailerons
If the elevators had enough of a roll effect, it would cause the aircraft to roll. They could have probably countered this with opposite aileron, but depending on the amount of up force versus down force scenario 2 would have taken over, only now they would have difficulty turning. (As per Kevin) The asymmetric deployment with the elevator at the top of the tail may create a yaw component, so the aircraft may also be slipping. This can put a lot of force on the tail, especially a twisting force as the pilots put in rudder to counter the yaw.

What it really all boils down to is that the pilots were probably right in rejecting the take-off, and probably would not have noticed the problem until Vr, which is after V1. Learning how to fly a crippled aircraft is not something you want to do at low altitude. If they did get it up and managed to get it in the air, they probably would have gained as much altitude as possible and spent time learning how to fly it while burning off extra fuel. This is pretty much what happened with United 232, where they had to learn how to fly the aircraft again.
Were the pilots right? Probably, but I believe they really didn't have a choice. I'm not sure that the aircraft would have rotated at all. Once they hit Vr and realized they couldn't get the nose off the pavement, it takes a couple seconds to make the decision to pull the power and hit the brakes. At 200mph you are traveling 293 feet per second. If they took 3 seconds to realize the problem and power down, that is almost 900 feet of runway gone.


Does the B-1B Lancer have controllable canards?

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


When can I descent below the MDA if the approach light system does not have red terminating bars?

You can descend down to 100ft above TDZE if you have any ALS in sight. You need an ALS with red lights (ALSF I & II) to go below that.

Red terminating bars/red side row bars help you find the threshold. Think of an ALS with red lights as being in the same category as Runway/lights/markings, Threashold/lights/markings, Touchdown Zone/lights/markings, VASI/PAPI, and REIL. Any other type of ALS (MALSR, MALSF, etc.) has the 100ft above TDZE restriction put on it when it is the only thing you can see.

@mins linked to a couple of helpful articles in the comments.


How do airliners get from the factory to the client if the aircraft does not have the required range?

Sometimes they do add temporary tanks. Here's a picture of what Hawaiian Airlines had to do to get their fleet of 717's over the Pacific because they did not have the range.

I don't have the answer to your question specifically, but I would guess they either add temporary tanks and go from SBNT-GUCY which is not much further than max-range, or take the long haul through the US and Europe.

There's a Cranky Flier blog post about this.


How can I use an ADS-B receiver to make my aircraft visible in Flightradar24?

ADS-B is broadcasted by many aircraft and contains flight and aircraft information. This can easily be received and decoded, either by dedicated devices or a simple 20 bucks TV USB dongle. All information is then sent to flightradar and other sites by the members of their community. (there are also other sources for their data)

However, once ADS-B is broadcasted and received by any receiver working for flightradar, the aircraft appears on their map. There is no need to register your self, in fact, you have to opt-out if you prefer to be invisible.

Now, you write about a receiver, and also a short visit of the product page shows that your device is a receiver only. Together with the built-in GPS it might just warn you about other near aircraft (which do broadcast ADS-B). You will need an ADS-B sender to find yourself on flightradar.

In the US, ADS-B Out is required to be installed (by Jan 1, 2020), it cannot be a portable unit. ADS-B In can be a portable unit.


Deployment of leading or trailing edge flaps - increase or decrease the angle of attack and critical angle of attack?

How does AOA change?
The angle of attack (AOA) is defined as as the angle between the chord line and the relative wind. When flaps and slats are deployed, the effective chord line changes. This is already nicely illustrated for trailing edge flaps in the article you linked:

(boldmethod.com)
As you can see, the new chord line has a higher angle compared to the relative wind, which results in an increase of AOA. Combined with the increase in camber, this will result in more lift (at the same airspeed), which means the pilot will usually reduce pitch to lower the AOA again when flaps are deployed.
I modified this image to illustrate the same for slats:

Now the new chord line is at a slightly lower angle compared to the relative wind, which results in a reduced AOA. The same is true for other leading edge devices (like e.g. Krueger flaps).
How does critical AOA change?
This depends on the exact type of device used. The following graphic shows how the coefficient of lift $C_L$ as a function of AOA $\alpha$ changes with various trailing edge high lift devices:

(HAW Hamburg - Aircraft Design)
For the slotted flap, critical AOA remains unchanged, but for all other types shown here critical AOA is reduced when deploying flaps. Note however that the maximum lift coefficient is always higher. The reason for the change in slope for extending flaps is already explained here: Why does lift curve slope increase when Fowler Flaps are deployed?.
The following graphic shows the same for leading edge high lift devices:

(HAW Hamburg - Aircraft Design)
Here, critical AOA is always increased compared to the clean wing.


Does a full set of legible structural engineering drawings for the Hughes H-4 Hercules still exist?

I would contact the Evergreen Air and Space Museum in McMinville, OR.  They currently have the actual H-4 prototype and their curators may be able to help.


Are answers posted to the FAA Sample Knowledge Exams?

Let me answer your question by first quoting from the 2017 Gleim Instrument Pilot Knowledge Test book.

The FAA no longer releases the complete database of test questions to the public. Instead, sample questions are released on the Airman Testing page of the FAA website on a quarterly basis.…
Gleim utilizes customer feedback and FAA publications to create additional sample questions that closely represent the topical coverage of each FAA knowledge test.

The rewrite removed questions that are no longer relevant to most pilots, e.g. NDBs, Colored airways, and added new questions on things like GPS, PFDs, CRM.

In addition, they now shuffle the answers for each tester, so you can’t just do things like remember that most of the answers to a group of questions is 'A'.

They supposedly cleaned up the answers on some of the calculation questions so that minor differences in measurement do not result in getting an answer that is not one of the choices. For example, in previous exams some of the charts were reproduced at 98% scale. If you didn’t correct for that you would get an answer that was midway between two selections.

They also cleaned up the questions that had two right answers but one was more right than the other.

Since the exams are testing for the same content, and draw the questions from known publications, understanding past questions will give you the knowledge to pass the current exam.

Purchasing a test book from GLeim, ASA, or Sporty’s is probably worth the money for most people. With your purchase, most booklet makers also give you on-line tests so you can go into the test well-prepared.

According to Gleim, 85% of test takers pass on the first try, so don’t make too big a deal out of the test. If you are prepared, you’ll pass.


Only in aerobatic aircraft is the inverted stall speed identical to the upright stall speed in level flight. Airplanes registered in the Normal and Utility classes have cambered airfoils which have a higher positive maximum lift coefficient. In inverted flight, their stall speed is higher than their upright stall speed. The same goes for gliders and airliners.

When I had my last aborted winch launch in a ASK-13, I involuntarily checked how well the cockpit had been cleaned last time. I had to briefly close my eyes to avoid getting sand and dust into them. I can confirm that it is fully possible to fly a negative maneuver in upright position, albeit only briefly. However, the negative acceleration had as much to do with the rate of rotation and my position ahead of the cg as with negative lift.

If I had pushed a lot more, I could had stalled the wing by undershooting the negative lift minimum. But this would had just limited the downward acceleration, and the negative lift would not had been sufficient for inverted flight, because the inverted stall speed in level inverted flight was most likely higher than the speed at the time of the tow line rupture.

The negative stall speed is just your flight speed, and the possible negative gs grow with the square of speed. Stall is a matter of angle of attack, not of speed. A negative stall in upright attitude is rather uneventful - the aircraft will be at a high rate of rotation and will just hit the limit of downward acceleration.


Where is the aerodynamic center for an A320?

The location of the aerodynamic centre can be tricky to find in an existing aeroplane, it will shift as a function of speed, Angle of Attack, flap deflection etc. In the pre-design phase the aerodynamic centre is often taken at 25% of Mean Aerodynamic Chord, and since you draw a plan view of the aircraft, we can use this to get an approximation.

If the wing has straight taper over the planform, the MAC can be constructed like in the picture below. Then take the point at 25%: this approximates the location of the aerodynamic centre for one wing, the other side is identical of course, and aerodynamic centre of both wings is halfway the connection line of the two.

 However, like many transport jets, the A320 has a trailing edge sweep of zero next to the fuselage to accommodate the main gear. So the aerodynamic centre shifts a bit aft. You can construct it or estimate it, aerodynamicists may frown upon this. There are many sites that show the graphical method of the picture above (here's mine), because it is nice and simple. To illustrate the complexity of finding the MAC in other cases, here is a graph from the same source.

Update

The above method gets us the MAC, which is the first step in determining the AC of the aircraft. A further method for finding AC in the pre-design phase is presented in Appendix E of Torenbeek:

Find wing AC as above.
Wing/Fuselage pitching moment, Appendix E.7 This is sensitive to the pressure distribution and is therefore hard to predict, except for:

Forward shift due to fuselage sections fwd & aft of the wing, particularly the nose. Based on the ratio of fuselage lengths.
Correction for lift loss in the wing/fuselage lift carry-over according to DATCOM.

Fuselage pitching moment. Equation obtained from Munk's theory for near circular cross sections.
Nacelle contributions. Appendix E.8, cannot be predicted reliably other than by wind tunnel tests, only a statistical correction is given.

The above is used for determining the AC of the aircraft. The contribution of the tailplane is included in the lift equations since it is dependent upon the Angle of Attack of the aircraft.

The complete method including graphs and equations is too lengthy to present in this forum, and can be consulted directly in the referenced Appendix.


Do these red stop signs apply to aircraft or only to vehicles?

No, those signs do not apply to aircraft. They are for vehicles and marks entry to the maneuvering area.


How is the quadrantal rule applied to VFR flights in Hungary?

Since the question is about Hungary, the answer will be in Hungary's AIP.

ENR 1.2 says:

  2.6. VFR flights in level cruising flight, when operated above 3 500 FT (1 050 M) MSL, shall be conducted at a level appropriate to the track specified in the table of cruising levels (ENR 1.7 para 3.).

(Emphasis mine.)

And by referencing that table (PDF) in ENR 1.7, it becomes clear Hungary uses a semicircular/hemispheric, and not a quadrantal rule.

The pilot's starboard drift will make their actual track 355 + 8 = 003°. VFR flights use the IFR rule + 500 (see below), so for this "eastbound" flight the pilot should fly odd + 500, an example would be FL 55.

(Hungarian eAIP)


ADS-B receiver, dongle vs SBS-3 or Garmin

Most ADS-B receivers in the market (including USB sticks such FlightAware Pro Stick USB) are receiving the same data using the standardized GDL-90 protocol. There is not a lot of data available on their amplifier characteristics.

Both in the air and on the ground, the main differenciator will be the quality of the antenna and its positioning. In that respect, avoid some USB sticks with a tiny embedded antenna without an antenna connector, as they will lead to lower performances than those of devices that are connected to much more efficient antenna.

Furthermore, with any device with an antenna connector, you will be able if needed to install the antenna at a more convenient location, as it is important the antenna has unobstructed view of the sky and when installed the ground be located as high as possible. According Garmin GLD-5x installation manual, ADS-B receiver antenna should be a standard 50 Ω vertically polarized antenna with a VSWR < 1.7:1 at 978 MHz and < 1.5:1 at 1090 MHz.

On that respect, the FlightAware Pro Stick USB, Kinetic SBS-3 and Garmin GDL-5x are all supplied with an external antenna connector, so I guess the cheapest one will do the job.


Why does the MiG-15 have a cruciform tail?

The tail position is a compromise which is influenced by these factors:

Interference with the wing's wake: The tail should be outside of the boundary layer flow coming off the wing root at all normal angles of attack. A high tail can cause a deep stall, something that was not known in 1947. Today all similar designs try to get the tail surface below the wing's wake.
Lever arm: By mounting the tail higher up on the swept vertical tail, its lever arm (in horizontal direction) can be increased without lengthening the tailpipe. A longer tailpipe means more mass and more internal drag and is best avoided.
Flutter: The higher the horizontal tail is along the vertical, the higher the danger of flutter. Here the longer lever arm (now in vertical direction) will lower the eigenfrequency of the bending mode of the vertical and the torsion mode of the rear fuselage. I suspect that for that reason the full T-tail was not chosen.

Mounting the horizontal smack in the middle of the tailpipe would require a heavy spar there to carry the bending moment across the fuselage. Mounting it on the vertical tail allows for a much lighter construction.


Why are test crashes not made harder on the airframe?

If the plane crashes with high vertical speed, the decelerations involved are so insanely huge that there is absolutely no way to make it survivable. That is well explained in
Even after years of research, why are planes unable to keep passengers alive in case of a fiery crash?.

However in many cases the aircraft is still, at least partially, controllable, so a crash-landing can be made. And that is the case where survivability can be improved by careful design, so that is the case they were testing.

This is also relevant for accidents on landing where the aircraft simply does not have that much vertical speed. Together these scenarios cover more accident cases than the out of control scenario.


Why is the fatality rate in the Diamond DA40 so remarkably lower than the SR20/22?

Not sure how true it is, but one theory I've heard about the high accident rate of the SR22 is the parachute. Every added safety feature tends to make people more careless. Was the same when airbags were first introduced in cars, accident rates shot up for a while before slowly trending down again.
Also, the DA40 is used more often as a trainer, while the SR22 is more often used by relatively inexperienced pilots who do have a license. Might well make a difference (student pilots tend to be more aware of the limits of their skill and knowledge than cocky fresh graduates who think that now that they are certified to know it all they really do know it all). And often that student will have an experienced instructor in the cockpit with him as well.


I'd like to know the name of this aircraft

This is a P-51D Mustang. The main clue for the "D" model is the bubble canopy.
To identify it as a P-51:
It has D-day paint stripes, which means it is not an obscure prototype of some other American fighter design.
It has a belly-mounted cooling air scoop, square rudder, wingtip and elevator tip profiles, and an induction air inlet under the prop spinner- which all distinguish it from the P-40, along with the bubble canopy.
It has a 4-blade prop, which distinguishes it from the P-39.
It has the engine in the nose and no cannon firing through the prop spinner, which distinguish it from the P-39 and the P-63.


How do airliner manufacturers come up with typical capacities of their planes?

These numbers are based on mixed-class configurations and use of floor space for other things. The A380 for instance can theoretically be configured with 853 "economy" seats, but no-one I know of has bought one configured that way. Typical first-business-economy configuration is 525, and Emirates seats just 489 because its first-class section is basically staterooms, and it has showers and a bar taking up floor space (it also has an excellent and large business class instead of using the back half of both decks for coach).

When designing an aircraft's seating capacity, especially for long-haul flights, total cabin weight (passengers and cargo) must be taken into account. The more stuff you're hauling, the less weight allowance you have for fuel, and therefore your range is reduced. Therefore, increased room per passenger on long-haul flights isn't just for passenger comfort, it's often a necessity to reduce total cabin weight and thus be able to max out the fuel load to get between the airports non-stop. Operators of shorter flights don't care as much because you can pack them in like sardines and still have plenty of fuel to get them where they're going.

Therefore, dimensions of various classes of seat differ by airline, aircraft and route (Lufthansa, for instance, operates three different A380 configurations based on the routes they run). The typical coach seat is between 17 and 19 inches wide (including half the armrest), and has a "pitch" (space between seats which determines the legroom and ability to recline) of between 31 and 35 inches.

For business class in three-class planes it gets a bit better; seat width averages about 21" and a pitch of about 38" (more for planes outfitted with lay-flat seats). First class ranges widely by aircraft type and airline (it's truly "first-class" in aircraft with three-class configuration; in two-class what's called "first" is closer to business class), but typically offers room to spare especially on long-hauls.

Coupled with required/desired aisle widths and additional amenities that widen the seats or replace them in certain areas of the cabin, it's fairly academic to count up how many seats you can fit aboard a particular airframe.


Let's start by skin friction drag formula:
$$F_s=\overline{C_f}\frac{\rho V^2}{2}A$$
where $\overline{C_f}$ is the average skin friction coefficient, $\rho$ is the density, $V$ is the True Airspeed and $A$ is the surface area of the wing.
By varying the Angle of attack, the term $\frac{\rho}{2}A$ stays constant assuming incompressible flow. As the Angle of attack increases, the velocity of the fluid increases over the top surface of the airfoil due to the lower static pressure being created. Therefore, as the Angle of attack increases, the skin friction drag also increases.
As the Angle of attack increases, the skin friction coefficient will also change. Let's assume two scenarios, one in which the angle of attack is close to zero, and one in which the angle of attack is very high, but the airfoil is not stalled, for instance, $12^{\circ}$. In the first scenario where $\alpha\approx0$, the flow over the airfoil is mostly laminar, that is, the velocity gradient inside the boundary layer is smaller close to the surface $\left(\nabla V=\frac{\partial{V}}{\partial{y}}|_{y=0}\right)$ which exhibits lower skin friction coefficient. Therefore, in scenario #$1$, the drag due to skin friction would be lower.
If the angle of attack is suddenly increased to $12^{\circ}$, scenario #$2$, the transition point on the upper surface would move upstream thus increasing the portion of the turbulent layer over the airfoil. And since the turbulent boundary layer has a higher skin friction coefficient, as a result, the skin friction drag would increase. On the lower surface, things are reversed. On the lower surface, the transition point would move downstream, increasing the laminar portion and lowering the skin friction coefficient. Since the fluid becomes more turbulent around the airfoil with an increasing angle of attack, the net change would be an increase in the skin friction coefficient resulting in the higher skin friction drag.
If we were to account for the compressibility effect on the skin friction coefficient, the skin friction coefficient would decrease. That is, the skin friction coefficient in the compressible flow would be smaller compared to the skin friction coefficient determined by incompressible flow:
$$\overline{C_f}^\prime=\frac{\overline{C_f}}{(1+0.144Ma^2)^{0.65}}$$
where $\overline{C_f}^\prime$ is the skin friction coefficient of the compressible flow, and $Ma$ the Mach number.
To summarize, with an increase in the angle of attack there would be an increase in the skin friction coefficient due to the presence of turbulent flow along with an increase in the fluid velocity over the airfoil, which would result in higher skin friction drag.


What is the difference between a VOR and a VORTAC?

A VOR ground station (VHF Omni-directional Range) provides azimuth information to aircraft equipped with a VOR receiver.

A TACAN facility (Tactical Air Navigation) provides azimuth and distance information to the facility in slant range (known generally as DME) using the UHF (Ultra High Frequency) band to TACAN equipped aircraft (normally military aircraft).

A VORTAC (VHF Omni-directional Range/Tactical Air Navigation) combines a VOR ground station and a TACAN ground station into a single facility.

If a VOR equipped aircraft is also equipped with a separate DME unit it will receive distance information between the TACAN ground station (at the single combined facility) and the aircraft.

More technical and expanded information can be reviewed beginning with section 1-1-3 in the Aeronautical Information Manual (AIM)


Who logs Pilot-in-Command time with all automation, autopilot, auto throttle, FMS, Autoland doing the flying?

In the US, there are two types of "PIC" that can be logged & may be interesting to report -- such as for an interview, perhaps.

Most common when starting out is "sole manipulator of the controls" -- and FAR Part 61 (61.51.e.1.i) defines this.  This includes essentially "sole manipulator of the autopilot," so the pilot who is designated as the PF -- pilot flying -- can log his time as PF as PIC, even though the autopilot is engaged & is driving the controls.  Early on, the time that you've spent "flying the plane" is of interest -- are you proficient and experienced taking off, landing, using the automation, and so forth.  (The standards for logging don't really give a way to distinguish between 10 minutes of hand-flying and an hour on autopilot, vs the whole time being hand-flown. It's not a perfect system.)

Of more interest when interviewing for jobs requiring significantly more experience is PIC as defined in FAR part 1 (1.1, definition of "Pilot in Command"), which amounts to essentially "who signed for the aircraft & is reponsible for the overall flight?"  Airlines who are considering hiring you are interested in this sort of PIC time, because they want to know that somebody has entrusted you with their expensive aircraft for enough hours (typically 1000+) that you've proven to be a good pilot IN COMMAND of not just the controls but the overall flight.

One person I talked to who did airline interviews (as an interviewer), said that when he looked at a logbook and saw every other leg logged as PIC, he knew that this pilot was essentially the copilot, the second-in-command of the flight, flying every other leg, but still responsible to the other pilot, who'd signed for the aircraft & was going to answer for it if things went wrong.  Then at the point when the logbook started showing every leg as PIC, that's when this pilot became the designated PIC, per the FAR Part 1 definition, and every leg was his responsibility, regardless of who was PF and who was PM.  That's the point at which the hours were "interesting" for hiring purposes.

At some point in one's career, the ability to manipulate the controls starts to become a given, and what distinguishes the pilots you want to hire from those you don't becomes factors like judgement or decision making.  Regardless of who is flying the leg, somebody has to be the final authority on decisions like, do we need to upload more gas?  Is this airport acceptable (not just legal, but wise) as an alternate? How long are we willing to hold before we punt on Plan A and divert to the alternate?  All sorts of stuff like that.  And the captain is the final authority on all of that just as much on the First Officer's legs flying as he is on his own legs flying.  (Which isn't to say he doesn't solicit input -- he certainly should -- but the final decision is his.)  Those are the decisions that occur during FAR Part 1 PIC, that may or may not be yours to make during Part 61 PIC.  Thus the different ways to count and report one's flight time.

Related discussion of Part 1 and Part 61 PIC time and logging thereof.


Chapter 4 of Degani's Taming HAL covers some of the details of this disaster, and is on a NASA site The Crash of Korean Air
Lines Flight 007

It details some of the interface deficiencies in the aircraft's navigation selection system.  We don't have definitive evidence about exactly what happened, but it is possible.  It goes over the idea that it was easy to get the system in a mode where the pilots could easily have thought that the inertial navigation system was engaged, but actually wasn't.

The Mayday show covered this one as well.  They noted that after the FDR was returned, it showed that the FMS was set properly.  Even though it wasn't controlling the plane, it would have continued to show the waypoints being passed as the aircraft crossed to the side.  Given that behavior, it would be very easy to believe that the system is working and you're where you should be.


Why do cockpit windows often appear to have a rainbow ‘tint’?

Thin-film interference

Thin-film interference is a natural phenomenon in which light waves reflected by the upper and lower boundaries of a thin film interfere with one another, either enhancing or reducing the reflected light.

It's the same mechanism behind your oil example. The thin film in this case is the heating coating applied to the windshield, which is intentionally non-uniform (explained below), making the effect even stronger.

(wikimedia.org)

Fringes observed on a windshield due to thin film interference caused by a conductive Indium Tin Oxide (ITO) thin film deposited on the window for electrical defrosting/defogging.
The fringes are strongly visible because the thin film thickness is highly non-uniform on purpose: as the voltage is applied on two opposite points of the window, a uniform conductive film (uniform sheet resistance) would lead to non-uniform current density, and non-uniform defrosting. Some window parts, especially on the sides and far from the electrical contacts, would dissipate less heat, and defrosting would be significantly less efficient here. The ITO thickness pattern is cleverly designed to provide a rather uniform heat dissipation over the whole window.


The small bulb houses the antenna that provides the satellite communications for the internet link.

Inside the aircraft several wireless access points provide a WIFI signal to the passenger's equipment. The wireless access points are connected to a central modem which in turn is connected to the transceiver unit. The transceiver uses the rooftop antenna to communicate to a geostationary satellite.

source: dailywireless

source: Flightglobal

The antenna is a small dish or phased array that is aimed at the communication satellite using servo motors and/or electronic beam steering. The antenna control system receives information about the position and attitude of the aircraft to calculate the relative position to the geostationary satellites that provides the internet communications signal.

There are also systems available on the market that use a ground based network to communicate with the internet. These systems cannot provide global coverage since the aircraft needs to be in line of radio sight of a ground based antenna.


When did the color orange enter flight test?

They were originally used to allow ground spotters to better spot the aircraft from the ground for optical tracking during flight test.  Another use of painting wingtips, tailplanes and tailfins bright colors was to allow observers a better means to determine the aircraft’s orientation and attitude in flight.

Finally if it all went so wrong so fast, hi viz colors made it easier for SAR crews to locate the wreckage....and the remains of the pilot.....quickly.

I know the Navy and the USMC were using orange flight suits as early as the Korean War, not for their test pilots, but for fleet air crews to make it easier for SAR aircraft to locate then in the event of a ditching or bailout over open water.


Is there an online source for European Instrument Approach Procedures?

Eurocontrol has an online repository of European Aeronatical Information Services.

You'll need to register, but the basic service is free.

By default, the application is JAVA applet based, which works not in the best way. After logging on, you can change the default behaviour to HTML based, which makes it more user friendly.

Then clicking "Enter Application" will bring to the next level.

Here you'll find several reporting options, but what you are interested in is located under "PAMS Light [AIP]"

Select the country you are interested in, "Charts" for AIP type and "AD" for Aerodrome and there you have the charts.


How much simulator training for general-aviation?

Under FAA rules, simulator training is not a requirement for any certificate/license. Only a certain amount of simulator training can be substituted for training in an actual aircraft for each certificate. Even then, only simulators certified by the FAA can be counted towards training time. The cost of the hardware and complexity of the software necessary to be good enough to receive FAA certification makes only high level FFS devices financially advantageous for airlines. These devices compared to the average home simulators is like the difference between 1970s TV night to holographic day.
Then, the question is if the allowed simulator time makes sense for the General Aviation pilot. Part 61.109 allows 2.5 hours of sim time to be substituted for actual flight time towards a private pilot certificate. That number doubles if the training is done in a Part 142 training center. By the time you get to the 1500 hours required for an ATP, ...

Not more than 100 hours of the total aeronautical experience requirements of paragraph (a) of this section or §61.160 may be obtained in a full flight simulator or flight training device provided the device represents an airplane and the aeronautical experience was accomplished as part of an approved training course in parts 121, 135, 141, or 142 of this chapter.

If the time requirements for aeronautical experience were arbitrary to the need for training, a flight simulator can be a viable option. A realistic AATD (Advanced Aviation Training Device) would be affordable for a General Aviation flight school.  Compared to the millions of dollars of a full-motion FFS (Full Flight Simulator), an AATD would be less than $100,000. Most flight schools in my area would charge a student roughly half the hourly rate for an AATD that they would for the typical 4-seat, 6-pack, single-engine, fixed-winged trainer aircraft.
Unfortunately, the lack of realism in an AATD makes it a valuable tool for procedures training only. An AATD lacks the feel and feedback of real flight. Its value is only as good as the student, instructor, or pilot’s diligence to following the procedures. To gain the most training benefit from an AATD carry out the flight using flight planning, flow checks and checklists to their fullest. Role-playing ATC will further add to this benefit. Treat it like a real flight and not like a game.
Anecdotally, I have trained on sims ranging from full-motion Redbird BATDs with custom G1000 bezels to stationary AATDs with fully functional instruments and controls, home sims on personal computers to multimillion dollar full-motion, gimbaled FFSs at the American Airlines Training Center. Except for the AATC FFS, none of them had the realistic force feedback of a real flight. None but the FFS had software sophisticated enough to mimic landings or wind interaction with enough realism. And, the FFSs are far too expensive for general aviation use. Actual flight time in a GA trainer aircraft would be cheaper.


What are the differences between "Off/On Time", "Total AC Time", and "Offset"?

There are different definitions for times in the U.S. FARs.
For example FAR §1.1 has a definition for flight time

Flight time means:

(1) Pilot time that commences when an aircraft moves under its own power for the purpose of flight and ends when the aircraft comes to rest after landing; or
(2) For a glider without self-launch capability, pilot time that commences when the glider is towed for the purpose of flight and ends when the glider comes to rest after landing.

This would typically be your OUT and IN time.
The Hobbs meter (depending on how it is wired) indicates the hours the engine is running or the hours the airplane is flying.
FAR §1.1

Time in service, with respect to maintenance time records, means the time from the moment an aircraft leaves the surface of the earth until it touches it at the next point of landing.

FAR §91.409(b)

Except as provided in paragraph (c) of this section, no person may operate an aircraft carrying any person (other than a crewmember) for hire, and no person may give flight instruction for hire in an aircraft which that person provides, unless within the preceding 100 hours of time in service the aircraft has received an annual or 100-hour inspection and been approved for return to service in accordance with part 43 of this chapter...

So the OFF-ON times are used for maintenance intervals.
I am personally unaware of total aircraft time or offset.
Most FMS installations have the ability to capture this data automatically.  It is called the OOOI value or OUT-OFF-ON-IN times.  Use the OFF-ON for maintenance and the OUT-IN for pilot logbooks.


What's the difference between ATIS and D-ATIS?

ATIS is traditionally a voice recording of someone reading the weather. D-ATIS is a way to deliver the information digitally so onboard equipment can interact with it. From the requirements

  Digital ATIS is an enhancement of the Tower Data Link Service (TDLS)
  and uses the Pre-Departure Clearance (PDC) System microcomputer to
  automate the delivery of airport and terminal area operational and
  meteorological information to aircraft flightcrews.
  Two phases of development are planned. The first phase will provide,
  via data link, a digital version of the ATIS /4 to flightcrews. Voice
  recording will continue to be utilized in the preparation of the ATIS
  broadcast. The second phase will add automated voice generation for
  the ATIS broadcasts.

Its part of a larger data link system that allows aircrafts and controllers to communicate certain things (weather info, clearances etc) with out clogging the radio channel.

Some ATIS systems now have a voice synthesizer reading out the reports so that no one needs to manually update the recording every hour.


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

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

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

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


How can I get the ADS-B GNSS Antenna Offset and Position Offset?

The fields are transmitted when the aircraft has ADS-B protocol version 2 (assuming you are looking at 1090MHz) and is on the ground.

They are specifically added to the ADS-B MOPS (minimum operational performance standards) to allow for accurately depicting aircraft on the airport surface.

I don't know by heart which message type it is in, which bits are used and what the encoding is.

Best is to obtain a copy of the MOPS; RTCA DO260B or EUROCAE ED102A (they are essentially the same, get the cheapest).


Are jet streams a net benefit in time and fuel savings?

Yes, Jetstreams are a net benefit on longer flights because it is easy to minimize headwinds and maximize tailwinds for both directions.

Longer flights can detour hundreds of miles in order to take advantage of more favorable winds and still result in a net gain.

I frequently fly from Toronto to Hong Kong. We always fly a polar route YYZ-HKG as it is shorter, but usually take a HKG-YYZ North Pacific route over Alaska to take advantage of the prevailing winds.

This daily flight is always scheduled at 15 hours 40 mins for Toronto to Hong Kong over the pole but only 14 hours 45 mins returning via a longer route over Alaska.

The longer flight routing over Alaska is a net benefit in time and fuel due to the prevailing westerly winds over the North Pacific.  This type of flexibility is not available on shorter flights.

YYZ-HKG 6,787nm non-Stop 15:40

HKG-ANC-YYZ 7,050nm non-Stop 14:45


Why do Boeing and Airbus have distinctively different nose designs?

The answer to this is, in part to do with corporate culture and part aerodynamics.

The corporate culture and history part is that Boeing have always built their noses that way and senior engineers have a tendency to return to designs they have used successfully before. If you look at the nose of a 747 and the nose of a B-17 you'll see some distinctive similarities that follow through all the major Boeing aircraft. This isn't surprising as lead designer of the 747, Joe Sutter, started working for Boeing on the 707 project under the direction of the engineers that designed the early flying forts.
Airbus is a newer company with a different corporate culture. They tend to embrace new design techniques like CFD computer modelling to a greater extent and this leads to slightly more efficient but less aesthetically pleasing nose and wing designs.

The science side is related to the speed that modern airliners travel at (around 0.85mach). At these speeds aircraft begin to encounter a phenomenon called 'Wave Drag' which is the incremental build-up of compressive shockwaves along the wings and fuselage as the aircraft approaches the speed of sound. The effect of wave drag is to drastically increase the overall drag affecting the aircraft, increasing the power output required from the engines.

There are several methods of combating wave drag, the first of these is the swept wing that has been a feature of trans and supersonic aircraft since WW2. The optimum angle of wing sweep is determined by the cruising speed of the aircraft. A more recent innovation is the Transonic or 'Whitcomb' Area Rule which states that:

"Two airplanes with the same longitudinal cross-sectional area distribution have the same wave drag, independent of how the area is distributed laterally"

Wave Drag can be reduced by attempting to match the cross sectional proportions of an aircraft as closely as possible to those of a Sears-Haack body (an aerodynamically perfect shape for supersonic flight) This is why Airbus planes have blunter nose. it is also why there are strange bulges under the wing roots of the A380. they are both attempts to make the planes cross-section conform to a Sears-Haack body more closely.


What would FAA controllers be referring to when mentioning "code 0027?"

In the video the controller states that the target was a "code" 0027, which would indicate a transponder code.  Using ATC radar (in this case ARTCC) the controller can see what a secondary radar return (transponder) is squawking.  In this case apparently it's "0027" and displaying an altitude of 37,000 ft.

According to FAA Order 7110.66E entitled "National Beacon Code Allocation Plan (NBCAP)" code 0027 is assigned to ZAU (Chicago ARTCC) and is listed as IS-3 (code category) IS= Internal Departures - Special Use.

Here is the link 7110.66e

I have no clue as to why that transponder code is attached to that target in Oakland Center's airspace.


What does it mean for a door to be armed?

If a door is put into armed mode, it will trigger the evacuation slide when the door is opened.

Prior to departure (usually before engine startup), all the aircraft doors are placed into the armed (or automatic) mode by the cabin crew. Methods of arming vary from aircraft to aircraft, but ultimately the girt bar (a metal bar attached to the door end of the slide) is physically attached to brackets either in or adjacent to the door sill.[...]If a rapid evacuation is required and the doors are opened while "armed", the opening of the door pulls the slide pack out of the bustle (because the girt bar is physically attached to the aircraft floor)

This is also the reason for the famous All doors in flight announcement:

DOORS TO ARRIVAL AND CROSSCHECK “Flight attendants, doors to arrival and crosscheck.”
Meaning: Occasionally heard as “disarm your doors and crosscheck,” and announced by the lead flight attendant or purser as a plane approaches the gate. The intent is to verify disarming of the emergency escape slides attached to the doors. When armed, a slide will automatically deploy the instant its door is opened. Disarmed, it needs to be deployed manually. On departure the slides are armed to facilitate an emergency evacuation. (You might hear this as “doors to automatic.”) Upon docking, they’re disarmed to keep them from billowing into the boarding tunnel or onto the apron during servicing.

The orange or yellow tape is a visual indicator for ground workers or ramp agents that the doors are armed or not armed. The visual indicator can vary, it can also be built into the door lock mechanism, triggering a visual indicator externally if the door is locked and armed. In the following picture, the orange tape is not strapped over the window, which should indicate an unarmed door. In the video that this image is taken from, the flight attendant has just locked and possibly armed the door, the other flight attendant would place the orange tape over the door window during "cross-check".

(Image Source: YouTube "B757-200 Door Closing" - Author: Exupery747)


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.


They refer to the same thing, but there is some separation between the terms, especially in the military. A cockpit is a hole with a seat that you strap into for the entire flight. A flight deck is a larger version of a cockpit, where you can at least leave your seat and walk behind it.

The traditional nautical term "cockpit" referred to a fairly small steering station at the top of the ship. Boeing introduced the term "Flight deck" post-WWII for their larger aircraft, to indicate the difference, and it has spread somewhat. A heavy's flight deck is still a cockpit, and can be referred to as such, but a "pointy's" (jet fighter) cockpit is very unlikely to be called a flight deck in speech.

In general and civil aviation, the terms are pretty much interchangeable. Still, a Ultralight Aircraft's cockpit is not a flight deck, so there is a strong connotation of a flight deck actually being a deck.

The B-2 has a flight deck, so do some fighters like the Su-34. Both can be called a cockpit as well. Basically, solo or tandem seating with entry through the canopy = "cockpit". Side-by-side seating with side door or bottom hatch entry = either "flight deck" or "cockpit".

This distinction is largely English-specific. Powered flight was being concurrently developed in France and Russia, and many languages ended up following their convention ("Piloting post/cabin" and "Crew cabin" respectively), where no term distinction was ever created.


Do small or regional airports have maintenance staff or companies onsite?

For scheduled commercial aircraft you will generally find:
If enough aircraft are coming and going from a particular airport, the airline may keep a line maintenance operation running there that can handle short-term maintenance and troubleshooting, or special inspection operations.
If not, and the airport has a AMO (approved maintenance organization) on site, the airline may contract with the AMO for line maintenance services, troubleshooting or special inspections.
If that's not the case, the airline will simply fly mechanics to the airport when airplanes are AOG.  This is typical when airplanes have problems that prevent dispatch at small remote airports.
So if an airplane needs a hard landing inspection at a remote "outstation", it'll be done by local contract staff if an AMO qualified to do the inspection is there, or barring that, airline staff flown out to the site.


Why A320/330 use C* FBW control without speed stability?

Many accidents have shown over and over that once the handling becomes muscle memory, the cue that having to pull harder means you are losing speed is easily missed anyway, so it's not as important as it seems.

So the artificial neutral stability instead decouples the controls: stick for flight path angle, thrust levers or A/T for speed. Nice and easy and you don't have to fiddle with the trim button that most pilots end up pressing rather mindlessly.

Large aircraft tend to be flown with auto-thrust all the time anyway, including e.g. a 777 which is stable in pitch and has trim. And when they are, the logic is rather like Airbus—control column for flight path angle, maintain flight path angle when released, just after changing speed you have to fiddle with the trim to get it stable again, which Airbus Normal Law does for you.

Note that aerodynamically all Airbus aircraft are still longitudinally stable, so if the sensors fail and the system degrades to Direct Law, the trim behaves like in any other aircraft.


How does the training for an EASA license from the US compare to that from Europe?

You definitely do not need to answer any theoretical questions before beginning flight training in Europe. In fact pop down to your nearest airfield, find a flight school, and chances are they will get you in the air (even for a trial flight) as soon as they are able.

Whoever told you that may have been thinking of the examinations you need to pass to get your PPL, and while 1000 questions is probably a high estimate, you need to be able to answer exam questions on a bunch of subjects such as Meterology, Air Law, Human factors and radiotelephony. You do this during your flight training, but again there is none of them you need to pass before you can begin.

I am from the UK, and I learned to fly in California. It was before the EASA licenses (In those days they were JAR licenses) but the idea was the same - I was training in the US for a license that was valid in Europe. I had to do the same training, and take the same exams as if I was in Europe learning  there was no difference.

On the cost, yes it was slightly cheaper per hour in the US however when you factored in getting there, staying in accommodation and food etc I don't think there was really that much in it. It was more an opportunity (excuse!) to take a 4 week holiday and do nothing but fly every day in great weather (Something which in the UK, at least, is hard to get to do).

Fun fact: I did this 11th October 2001. Conversation at LAX with TSA having explained I'm entering the US as a lone male to learn to fly - "Don't worry Mr C, you don't fit the demographic we're currently looking for".


Is there such a concept as 'Max Overhauls' for aircraft components?

Yes, but its a fairly new change from the FAA. The FAA recently regulated part Life Limits, a limit in place at certification time (or through a later AD etc.). The IATA also outlines guidance for life limited parts. This is a fairly new reg and many of the older aircraft out there may not be subject to it since they were certified prior to it. This AC also outlines some info relating to it.

However for any mechanical part there, in theory, is a limit to the amount of times it can be overhauled if that work requires reductive machining. Something like a crank case, cylinder head or piston sleeve can only be machined so many times before there is not enough material left for a proper overhaul.

The definitions of overhaul vs rebuild are important. A rebuild may reset a parts life, you can read more on that in this question.

Any life limited part should be listed in the documentation for the specific airframe/model in question. For example here is the list of the Robinson R-22 helicopter. More notably the Cirrus SR-22 has an airframe life limit of 12,000 hours as part of its certification.

  The certification requirements of 14 CFR 23.573 require that the
  composite airframe structure, cabin, wing, empennage their carry thru,
  and attaching structure whose failure would be catastrophic must be
  designed to damage tolerant criteria. Damage tolerant certification
  for the selected airframe life of 12,000 flight hours has been
  established for all of the affected parts with no special structural
  limitations or inspections.


Can anyone identify this biplane from 1920s-1930s?

It looks like a 1928 Swallow TP by Swallow Airplane Company.

(source)
(Swallow TP at Yanks Air Museum in Chino California.  Photo plus some information about the specific aircraft may also be seen on this website )

(source)


Why is stabilator used in some small airplanes?

Simplicity. Yes, a servo tab is helpful, but most control surfaces should include a trim tab, so this can double as a servo tab. Total part count should still be lower than that for a stabilizer-elevator combination. But there are other advantages: Easier adjustment of stick forces and little loss of stability with free-floating controls.

By hinging the stabilator (or full-flying tail) near the quarter point, its control forces can be kept small and tailored with the servo tab. Also, this helps to keep the hinge moment coefficient derivative over angle of attack $c_{r_\alpha}$ low. The ratio between it and the derivative over deflection angle $\eta$ determines the angle to which the control surface will float, and a small $c_{r_\alpha}$ means that the stability with a floating control surface will be close to the stability with a fixed surface.

Also, balancing masses are easier to place when the full surface moves.


Effect of Low Vitamine B12 on Class 1 Medical

I am not a doctor, really the best way to get definitive answers is by talking to an AME.

Vitamin B12 deficiency isn't by itself any sort of issue, lots of people get less than they need because of diet, especially vegetarians and vegans. Vitamin B12 deficiency can lead to a form of anemia, which is potentially disqualifying, unless it can be kept below a certain level.

So, if your doctor hasn't found any sort of anemia or other condition due to lack of B12 then there's no consideration on your medical. Work on getting more in your diet or keep up on the supplements. However, if you have anemia or some other condition due to the deficiency then it is a consideration on a medical.


Are steam gauges more reliable than glass panels?

Most aircraft using electronic displays have double (and sometimes triple) redundant power supplies to keep the electronics alive in cases of power failure. The mechanical gauge panels of the not so distant past did not have these same levels of redundancy built in.

Beyond power considerations, glass panels also contain features like weather radar, collision avoidance, and navigation that further increase the reliability and safety of the system as a whole.

That said, it's fair to say that glass panels are more reliable. The funny thing is, critical mechanical gauges are still included on most panels as last resort backups.


What are the legal issues for an Uber or Lyft type model for ride share on General Aviation aircraft in the United States?

Depending on how much detail you want, you can read the legal ruling in Flytenow Inc. vs FAA, which is the most recent and highest-level ruling on general aviation flightsharing. The Supreme Court declined to hear an appeal.

Essentially, Flytenow wanted to let pilots find passengers willing to share the costs of a flight. They emphasized repeatedly that all decisions about if and when to fly, the route to take etc. would be made by the pilot, not the passengers. On the other side, the FAA said that by advertising for passengers, pilots would be holding out and that makes it a commercial operation. There were plenty of arguments on both sides and ultimately the courts decided that the FAA was acting consistently with previous decisions and regulations.

Flytenow made three legal arguments, all of which were judged invalid on appeal:

Advertising for passengers is protected free speech under the First Amendment
Private pilots' equal protection rights under the Fourteenth Amendment are infringed if they can't share costs
The FAA's ruling was vague

If you read the court's decision, you can see that they basically agreed with the FAA that protecting passengers justifies limiting what private pilots can do:

  The FAA’s distinction between pilots offering expense-sharing services
  on line to a wide audience and those offering expense-sharing services
  to a limited group is justified: holding out to the public creates the
  risk that unsuspecting passengers, under the impression that the
  service and its pilots lawfully offer common carriage, will contract
  with pilots who in fact lack the experience and credentials of
  commercial pilots.

To put it even more simply, the basic difference between Uber and Flytenow is that the FAA believes that the general public can identify a bad driver, but not a bad pilot. That's the fundamental reason for having commercial licenses, part 135 etc.


Could a runway include a safety device to destroy a plane's landing gear?

There is indeed such a system installed at some airports. It is called an engineered materials arrestor system (EMAS). Incidents such as Southwest 1248 have shown the potential safety issues of runway overruns, as you have pointed out. The EMAS solution uses a pad of special material at the end of the runway, designed to allow landing gear to sink into the material. The landing gear is not ripped off, but as the gear travels through the material, the plane is slowed down.

Destroying the gear is not a desirable option. Although the gear on airliners is designed to safely separate from the aircraft, there is still the potential for damaging fuel tanks or other structure. The aircraft will also be even less controllable after the loss of landing gear. If a small aircraft is not going very fast, a small wall could cause it to flip over, worsening the situation.

In the crash you referenced, the aircraft was traveling very fast at the end of the runway, and an EMAS may not have been sufficient to stop the plane. An EMAS typically has a max entry speed of 70 knots, so in incidents like the one linked from the question, this kind of system may not completely prevent a fatal incident. Since the aircraft's gear must break through the material, lighter aircraft may not be stopped as effectively. However, small aircraft have been stopped with such a system.

The FAA is looking at places where these systems could be useful, with a focus on runways that cannot have the recommended 1,000 foot safety area at the end. The runway safety area (RSA) is the best option for a safety buffer at the end of a runway, providing extra distance for an aircraft to stop. The article above notes that the EMAS at Burbank airport took $4 million to install, and that is a fairly small airport that doesn't usually see anything larger than a 737. Any overrun will incur certain recovery costs, but an EMAS will need to be repaired after any overrun or accidental damage, possibly closing the runway, and will be less effective until repairs are completed. Airports must weigh all of their options for providing a safe facility.


On a large transport aircraft where exactly is the Forward pressure bulkhead?

It's located  in the aircrafts radome (nose) where the weather radar is located. It's to keep the pressurized air from exiting the fuselage.


Does the reference for AGL include obstacles?

AGL is "Above Ground Level".  Ground is the reference.  Trees, buildings, towers, and such are obstacles.  Pilots need to be aware that obstacles exist.  Most of the smaller ones can be addressed by just flying at a safe altitude.  This is covered (in the US) by the following Part 91 rule:

  §91.119   Minimum safe altitudes: General.
  Except when necessary for takeoff or landing, no person may operate an
  aircraft below the following altitudes:

  (a) Anywhere. An altitude allowing, if a power unit fails, an
  emergency landing without undue hazard to persons or property on the
  surface.

  (b) Over congested areas. Over any congested area of a city, town, or
  settlement, or over any open air assembly of persons, an altitude of
  1,000 feet above the highest obstacle within a horizontal radius of
  2,000 feet of the aircraft.

  (c) Over other than congested areas. An altitude of 500 feet above the
  surface, except over open water or sparsely populated areas. In those
  cases, the aircraft may not be operated closer than 500 feet to any
  person, vessel, vehicle, or structure.

  (d) Helicopters, powered parachutes, and weight-shift-control
  aircraft. If the operation is conducted without hazard to persons or
  property on the surface—

  (1) A helicopter may be operated at less than the minimums prescribed
  in paragraph (b) or (c) of this section, provided each person
  operating the helicopter complies with any routes or altitudes
  specifically prescribed for helicopters by the FAA; and

  (2) A powered parachute or weight-shift-control aircraft may be
  operated at less than the minimums prescribed in paragraph (c) of this
  section.

Following (a) and (b) is the safest course. Para (c) provides a great deal of latitude to fly low but has significant risks.  Agricultural pilots fly very low all the time.  But ask any one of them and they'll be glad to discuss all the stuff they've hit.

These rules are primarily directed at VFR flight. Under IFR, ATC clearances are designed to ensure operating at safe altitudes, clear of both terrain and obstacles.

For larger obstacles such as towers and bridges, they are charted.  As you can see on the clip below:

There are a number of towers in a relatively small area.  In this case there is the underscored BITHLO TOWERS label to bring attention to them. Adjacent to the tower icons are two numbers. The number not in parentheses is the height in MSL.  In parentheses is the height AGL.


Would injecting water into a jet engine’s exhaust increase velocity?

Spraying water into the exhaust stream will cool down the exhaust flow. The energy needed to heat and evaporate the water needs to come from somewhere, after all. The cooler and denser exhaust flow will slow down, so its impulse will become lower, reducing thrust. While the mass flow will go up, its speed will be reduced. Since water enters the flow as a liquid and leaves the nozzle as a gas, its evaporation enthalpy is irretrievably lost and removes energy from the exhaust stream. The slightly higher mass flow in combination with a lower speed will result in a lower impulse.

If you spray water into the intake flow (or after the first few compressor stages), the same evaporation enthalpy will allow a higher mass flow in the intake, so a higher mass flow in the combustion chamber can be achieved. Also, the cooling of the intake air allows to add more fuel in the combustion process, so more thrust can be created. Of course, this is bought with higher fuel flow.


Can the bleed air for deicing the wings of the aircraft be switched on and off for jumbos?

Yes. Automatic operation exists as well (may not be installed/chosen by the operator).

Nitpicking: this bleed air is for anti-ice, not de-ice (but even manufactures get it wrong in the manuals sometimes, see below).

Saving this bleed air when not needed saves fuel and engine wear, and allows higher more efficient cruise altitudes.

Speaking of the A380, due to its thick wing, it does not need much anti-icing.

(Source: A380 FCOM)


What should pilots do if they observe illegal activity onboard an aircraft?

I think a lot would depend on the type of illegal activity observed.  For example, if someone was getting injured or worse, that would mean the crew would need to take immediate and aggressive action, which would include possibly putting themselves in some danger to protect the victim, at least to a certain degree.  That said, getting the plane down safely would be higher priority for safety all the way around so protecting the victim needs to be weighed against the risk of getting injured to the point the pilot can no longer fly the plane.

In the Bieber's case, escalating the situation by trying to intervene would only create risk of the crew being injured and then unable to bring the plane down with no real upside.  Putting out a warning, then proceeding to a suitable airport immediately would seem to be the most prudent course of action.


How is stability ensured with bulk-loaded cargo?

You can simply tie down the cargo to prevent its movement. Most planes have nets that subdivide the bulk cargo compartment, so as to prevent movement of the baggage. For example, the following image shows the cargo hold of a B737 with dividers.

Image from airport-data.com Photographer:  Nick Taylor Photography

The ground operations manual of a carrier gives the following procedure for securing loads in A320:

  1.1.4.2.1. Load Securing A321 (bulk loaded)

  The divider and door net in each compartment must be closed at any time. Additional tie-down is normally not required except for individual items of load which by their nature, shape or density may constitute a hazard. They must be restrained, which can be achieved by filling the cargo hold or net
  section volumetrically, or by tie-down.

  ... Packages weighing more than 150kg shall be restraint or individually tied-down. Single packages should be tied-down. Tie-down of loads to aircraft structure is achieved by straps or nets connected to the tie-
  down points located on the cargo hold floor.


Is it possible to 'retrofit' electric flight control actuators to replace existing hydraulic actuators on aircraft?

Technically it's entirely possible to replace these actuators but it's unlikely they will because the economics don't work out. The weight savings you get will be offset by the costs from design, recertification and installation. It's not as simple as bolting something on.

When you make a big change like this to an airplane you have to take into account the changes it will bring. The actuator may be a different shape, the loss of weight in one area will change the balance of the airplane and affect its structures in ways that have to be accounted for. The forces the new actuator design will put on structures must be accounted for.

Electric actuators need electricity, that means you need to generate it and supply it. You'll have to run wires for it, maybe change the engines generators so they supply more juice. You may have to change the Ram Air Turbine so control can be maintained if engine power is lost. The airplane's control systems may have to be modified. Emergency procedures, maintenance manuals must be changed, people have to be trained, etc. Finally, all this must be certified with the FAA, EASA, and other bodies before passengers can be taken, only then can the actuators actually be replaced.

All this costs a lot of money to do, which is why major retrofits like that are rarely done, the ton of weight they save isn't worth the costs of doing it, even over 10 years of flying.


What documents/procedures I have to follow to fly my aircraft from the UK to Norway?

Are you flying in your own plane, or as a passenger on an airline?  https://www.udi.no/en/want-to-apply/visit-and-holiday/?resetguide=1 will give you some info, but not everything you need if you're flying in yourself.


Aircraft tires are replaced on condition, but maingear tires usually last about 250 cycles. A 777 in longhaul usage might only get two cycles a day, so a set of tires would last about four months.

The 777 uses a 50x20.0r22 with 32ply rating. I couldn't find that exact tire but a similar one costs $4700 new. It is common practice to retread or remold worn tires after inspecting the carcass to ensure its serviceability, and these cost about half of new.

Interestingly, this study by Embry-Riddle suggests that 99% of tire wear could be eliminated by prespinning the tires prior to touchdown, eliminating the puff of smoke you see as a part of the tire burns away as it matches up to relative runway speed. If correct, a tire would effectively last forever, until it was damaged as by debris or a hard landing.


Why are there so many aircraft designs which look generally profoundly similar?

It’s an interesting question.  Aviation historian Bill Sweetman wrote about just that in an Air & Space article called How the 747 Got Its Hump.  The answer to the question is quite long and specific to the aircraft type and use but the short and sweet answer is that airplanes are a great compromise between a number of factors, including mission profile, aerodynamics, structures, propulsion, avionics, manufacturability, realities and practicalities of product use, and on a few occasions customer insistence and industrial espionage.  See illustration below.

It just works out that, when all the factors above are taken into account, the designs you describe tend to be the best all around solutions for particular aircraft sizes, costs, payloads, mission profiles, safety, etc.  Like any other artifact made by humans, aircraft are but single answers to open ended design problems; a compromise between all of these competing requirements into a tangible product.  No one answer is 'correct' per se, but these kinds of aircraft designs seem to be the most optimal and every single design team when confronted with the requirements and design constraints create much the same thing.


CVG stands for Compressor Variable Geometry. (e.g., this pdf, page 5).

This is a technique to change the pitch angle of the compressor vanes, much like a variable pitch propeller. Wikipedia does not have an article for the use in aircraft (probably because it's not used all that much), but does have an article on a Variable-geometry turbocharger which is closely related (for non-car-enthusiasts: a turbocharger compresses inlet air with help of a turbine at the exhaust). Basically, this system lets you control the pressure ratio independent of the RPM. Advantages include

More efficient settings based on air pressure (altitude / temperature). You basically decouple the turbine stage from the compressor stage (but instead of a gearbox, you use the vane angle). This way, you can optimize your compressor stage to different conditions while keeping the turbine RPM at the most efficient value.
More efficient cruise performance without compromising TO/GA capabilities. Aircraft engines are heavily overdimensioned to account for take-off power and contingencies, which means a bigger engine than strictly necessary and thus less efficiency in cruise. This can now be partially mitigated by varying the compressor vanes pitch for optimal efficiency during cruise and optimal power during TO/GA
Higher engine RPM possible during approach. Normally, to keep your engines spooled up for eventualities, you need to increase their power, and as such need to increase drag with flaps and spoilers to keep the speed down. Now, you can spool up the engine to a high RPM with low compression ratio, and increase power relatively fast without having to overcome engine inertia by increasing the compression ratio by increasing the vane angle.


Is the KC-135 landing gear life limited?

All landing gears have a limited lifespan unless they undertake in really, really big maintenance, as we saw with the Antonov 225, which went under maintenance for 18 months! And the KC-135 is no exception. Most landing gears last about 20 years, and the one's of the KC-135's is designed for 30 years. But even though it was designed for only 30 years, the operators of the KC-135 still extend it's life by a lot, with as you said, regular maintenance. So, you might see some KC-135 landing gears that are 40 years old!

Aging landing gear life extension
The committee is concerned that the Air Force has been extending the use of aircraft landing gear far beyond their original design life. The KC-135 was designed for a 30-year lifetime, but will retire at 86 years and the B-52, designed for a 30-year life, will retire at 94 years.

Source: congress.gov


Why is the L/D ratio numerically equal to the glide ratio?

The sum of all work done on the airplane must be zero in a glide. That is, the work done by gravity must equal the work done by drag. Note also that lift equals the force of gravity in equilibrium
Work is force times distance. If gravity is X times larger than drag, this means that the distance in vertical direction must be X times smaller than in the horizontal direction.


Though it's often omitted from diagrams, most pitot tubes have one or more drain holes connected to the pressure chamber, and are essentially "self-draining" (water doesn't make it into the lines):

In addition to drains on the pitot tube itself some aircraft have separate "drip chambers" and drains for the pitot (and occasionally static) system to remove condensation or rain that got past the drains (marked as 2 in the photo below):

Regarding other contaminants, at altitude the air is generally pretty clean.
The biggest problem you'll have with contaminants in the pitot tube is usually bugs (either building a nest in the opening, or smacking into it in flight). Pitot covers can be used on the ground to prevent this (and they're also used when washing or painting aircraft to prevent water or paint from getting into the system). Often some tape serves the same purpose - but you need to be sure to remove the tape or cover before flying.


What is the correct ATC phraseology for tower to clear a practice approach?

If you want to go missed on a practice instrument approach rather than land, the controller will clear you for a "low approach".

See here for more on the legality of low approaches.


What happens when a pilot has no Instrument Rating and visibility drops?

It is very rare for weather to go IMC unexpectedly.

A responsible pilot should see that weather is deteriorating, and begin planning for the nearest available landing.   If they cannot find a landing, they should contact ATC while still in VMC, declare an emergency, and begin working with ATC to get down safely.

In some cases, a pilot may inadvertently enter IMC unexpectedly.   The standard procedure is to execute a standard rate 180° turn, and fly equal time in the opposite direction.  That should get them back to VMC conditions.

If that doesn't work, unfortunately inadvertent flight into IMC is a leading cause of GA accidents, especially CFIT (Controlled Flight into Terrain - i.e. 'aircraft flew into the ground').   Because of that, even basic private pilot training includes more basic instructions on instrument flying (BAI) than it used to.


Why does a T-tail produce a pitch-down moment in sideslip?

I've found some useful research here: E.C. Polhamus. Some factors affecting the variation of pitching moment with sideslip of
aircraft configurations. Technical report, NACA T.N. 4016, 1958.

The image shows the situation for high angles of $\beta$:

  At large angles of sideslip with swept horizontal
  tails, the loading will probably not be antisymmetrical mainly because
  of the difference in lift effectiveness of the leading and trailing portions
  of the horizontal tail caused by the difference in their effective
  sweep angles. This would result in a net lift induced on the horizontal
  tail which is a function of sideslip and tail height. This possible
  effect of tail height is illustrated in sketch 9 for large positive sideslip
  angles:

Interesting to see is that the model has no wings, so we can rule out any causes related to wings, in case people were thinking in this direction.

I putsome more thought into it, and I drew these diagrams, which helped me understand the things being said in the paper.

The blue pluses and minuses are the resulting velocities caused by the horizontal velocity as a function of the sideslip ($V_{\beta}$).
The red distributions are the forces on the elevator as consequence of this $V_{\beta}$.

This component creates an increased velocity over the left side of the rudder, and a decreased velocity over the right side of the rudder.
If there's no sweep, the effects are equally strong, and no effect on the lift is present (denoted by the top two images)

However, if there's sweep, the effect on the left side is less strong, whereas it is stronger on the right side (indicated by the two tails in the bottom row).

In a T-tail, this stronger influence is acting on the lower side of the tail. As it is a minus (meaning a relative reduction in velocity), it will lead to a reduction in suction on the lower side, or an upward force, causing a pitch down.

In a normal tail, the minus will act over the upper surface. It causes a deceleration of the flow over the elevator, thereby reducing the lift it generates. This causes a pitch up movement.


Engine design speed is the shaft RPM and vane pitch which yields the rated thrust that the engine was originally intended to furnish. This will typically be quoted for takeoff at or near sea level at a standard ambient temperature (including a time limit to control maximum temperatures inside the engine) and for optimum cruise conditions at altitude (which will include specification of nominal fuel burn rate in pounds per hour).


For what is VMCL the minimum control speed?

I would go with B as well.  Minimum Control Speed - Landing is for the critical case where you are in the least favourable possible configuration on approach, gear down, full flap, trimmed at approach speed, C.G. at least favourable location, etc etc, then have one engine fail and the other is put to full power. VMCL is the speed at or above which control can be maintained at that instant maximum asymmetric trust is applied, before the airplane can accelerate or the configuration can be changed.  Go around speed in the approach configuration will be faster than VMCL.  VMCL is the edge of the cliff.


What are the major drivers of cost/price differences between Cessna 172 and Piper Cherokee?

There are a lot of factors here but in reality a 172 and a Cherokee are about the same price, lets look the reality.
First off a huge chunk of people rent instead of buy. In this regard at the two airports I have been flying out of have both the 172s and Cherokees (both of which I have rented) are the just about the same exact price (all prices in USD).

Cherokee Wet  : 108
VFR Only 172: 103
IFR 172 : 113

The used prices (how a lot of people buy planes like this) span the field and I would say are on par (as per my latest perusing of Trade-A-Plane). That being said you can get a beat up Cherokee 140 for in and around 20K and a beat up 172 for about the same price (at least from what I have seen listed). At the same time you can get a fully loaded Cherokee 180 or 235 if you go complex with dual GPS/COMS and other toys for the better part of 60-70K, same for the 172s.
Yes they are similar planes but the truth is that the price things actually trade hands for is often not disclosed and is almost always not the list price in terms of used stuff. There is a bit of preference as well, if you trained in a Piper you may be more inclined to stay in a Piper and likewise with the Cessnas.
As for safety, the 172 is a very safe plane by anyone's standards. Then again so is the Cherokee and it seems that the argument can go on forever but the numbers are the numbers (accidents per 100,000 hours of flight)

The 172: 6.17 overall accident rate.
The Cherokee: Cherokees came in at 6.86

In reality a small difference, but lets be honest they are about on par. For what its worth, the Cherokee numbers include the Arrow which is a retractable and suffers from the proverbial gear up landing as well as other things that make a retractable potentially fail more than a fixed gear plane. This may account for the difference in safety record (again, a very slight difference).
While similar on paper there are some mission profiles that allow the planes to serve different roles and may make the 172 more attractive in some cases. The high wing design allows for excellent downward view which makes the 172 a great plane for aerial surveying/photography/pipeline check ups and similar tasks. The 172 also sports two doors compared to the single one on the Cherokee. That being said some feel as though the 172 is a bit easier to get into for the less nimble, but I am young and nimble so I can't speak to this. There are also those who like the high wing design for landing on grass or other back country flying due to the increased ground clearance of the wing allowing you to avoid obstacles.

From an aircraft family standpoint the Cherokee 235 had a much better useful load than the highest power 172's. However even the 180 Cherokee has a better useful load than the 180 Cessna. When you are flying around a family this is worth considering.
Although Cessna had it to an extent, Piper has always had the selling point of "stepping up through the planes". The idea being that your mission (as time went on) would be to go faster, further, and higher. Subsequently you would need a bigger plane. They facilitated this by delivering a very constant platform in the, Cherokee, Arrow, Cherokee 6/Lance/Saratoga then up through twins with the Seminole and Seneca if you need to go there. While I'm not sure I have ever seen any real data on this, I do have a real world experience with a buddy of mine who has been flying for about 25 years.
In response to the question "Have you ever owned any other planes?"

Yeah, I had an Archer for a while, it was a great plane. But then I had a third kid so I bought a Saratoga.

Like it or not the Piper sales model there worked.
You could also forgo common sense and just buy a Mooney because everyone else put the tail on wrong.