How does pressure increase in a multistage compressor? Given the overall pressure ratio of a multi-stage compressor, how can I calculate the increase in pressure at each stage?

Does pressure increase linearly at every stage, or does it increase logarithmically or exponentially?

Intuition tells me that pressure increases logarithmically since the latter stages of a compressor can't compress the air as much as the first stages, but intuition hasn't served me so well in thermodynamics...

Thanks!

Firstly, your intuition doesn't really apply in terms of basic thermodynamics (but, as I'll explain, you're kind of right):

  Boyle's Law: "For a fixed mass of gas, at a constant temperature, the product (pressure x volume) is a constant."

Pressure does increase linearly [assuming the temperature stays the same]: if you squash an amount of a gas into half the volume, the pressure will double (assuming you keep the temperature the same). If you squash it into half the volume again, the pressure will double again (4x the original)

However you're also right in that we don't simply increase pressure by the same amount as we go along: Each stage compresses the air by a different amount (otherwise an engine would look like a weird triangle). and perhaps more importantly we can't maintain a constant temperature in an engine... as we compress the air into a smaller volume the temperature increases unless the air is being cooled in some way.

Essentially, though, you can calculate the pressure change at each stage if you know how much the volume reduces by (ie how much smaller each chamber is than the last) and the temperature of the air in each.


Besides size, what determines the cost of creating a composite structure for a single engine piston aircraft? When designing an aircraft (LSA or GA), how would one minimize the cost of construction when the aircraft is composite. To be clear, I am talking only about the structural components, not the interior, engine, or instruments.

Cost drivers for composite structures:

Weight: Lighter is harder to do and needs more work and more expensive materials.
Surface quality: Either you use lots of filler and several sanding and filling cycles, or you produce a high-quality negative mold, which is a lot of work.
Reproducibility: If you want to produce several identical parts, you need to produce a reusable negative mold. Simple composite structures can be built in a positive technique.

Positive building techniques

You can either use a styrofoam core which you cover with fibers and epoxy (just as Burt Rutan did), or you build a balsa wood core on a simple jig and cover it in fibers and epoxy on both sides to produce a sandwich shell. In both cases you build from the inside out and have to finish the surface with repeated cycles of filling and sanding until you arrive at the desired contour and surface quality. This is a lot of work already, but much simpler than building a negative mold.

Negative building techniques

Here you first produce a core of the desired shape (again much like the styrofoam-epoxy structure above) and use this to produce two casts which will serve as the mold in which to build the eventual structure, or you take a large CNC mill and have it produce the mold from a big block of aluminium (or another suitable material). Now you will build the structure from the outside in, so you achieve the desired surface quality without filling and sanding the final structure, and you can repeat this process to produce several identical pieces until the mold is worn out.

If you add up the material and labor cost of the two techniques, you will find large cost differences which are reflected in the quality of the final parts.


Can short buildings near an airport affect runway winds? Reddit user u/ywgflyer contends for CYYZ, Toronto International Airport,

23 is the "good" runway. The 24s are garbage in a crosswind because of the localized wind effect that all the hotels (and the terminal) have. I've never had a windshear problem on 23, but I've gone around several times on 24R with a crosswind from the right.

I never visited CYYZ. But I just roamed CYYZ on Google Maps. I see many short hotels, maximum 7 floors? I see no tall edifices in or near CYYZ, except the two? ATC towers?

But let's hypothesize that  buildings near airport create these localized wind effects. How can these buildings erect in first place? Won't airport's lawyers try to stop these edifices being erected on grounds of safety? But I don't know aviation, land, or planning law.

Buildings near or on an airport are generally only restricted in height for obstacle clearance purposes.  I've never heard of a wind related planning limitation that would apply at Pearson (although there may indeed be other airports with building restrictions of some kind due to some kind of unusual wind effects).
The buildings on the north side of 24L's threshold end at Pearson can certainly produce a fair about of "burble" below 300 ft that would bounce light aircraft around pretty good on a day with strong winds.  They don't have to be all that tall; the area and complexity of the structures will produce plenty of turbulent flow in the surface boundary layer.
Anticipating this is a basic part of airmanship. Usually it's having an awareness of wind shadows caused by trees and hangars at small airports, but situations like Pearson with all the hotels and big hangars on the windward side of the threshold take it to another level. If I was landing there on a strong wind day on that runway and saw all the structures, I'd approach high and land farther down the runway to try to avoid the burble; same thing you do to avoid wake turbulence from a heavy that landed ahead of you.
If someone in an aircraft that only needs 1500 ft to land insists on landing on the threshold of a 9000 ft runway in spite of the turbulence generators to the right, they haven't been trained very well.
At the other extreme, if you were flying a Paramotor, you'd have to give the same consideration to small trees and houses on the upwind side of your landing area.  It's all the same pretty much, just different in scale.


Why couldn't the DHL611 crew hear the ATC transmissions for the Bashkirian 2937 crew? In the mid-air collision over Uberlingen, why couldn't the DHL611 crew hear the instructions given by the controller to Bashkirian 2937 crew if both aircraft were on the same frequency?

It wouldn't matter if they had.

The DHL611 crew had been trained to obey TCAS orders over ATC. This was fairly common, but not universal practice at the time. Their training was unambiguous, and stated that TCAS should be followed over ATC instructions. They had been trained that both aircraft would follow TCAS and avoid the collision, and had no reason to believe that wasn't the case: they didn't even necessarily know that BTC2937 was the aircraft causing their TCAS alert

The crew of BTC2937 hadn't been trained to follow these priorities, or became confused.

From the Wikipedia page about the incident:

  The TCAS Pilot's Guide was ambiguous as to whether or not TCAS advisories should take precedence over ATC instructions.[BFU 14] This ambiguity was replicated in the Tu-154 Flight Operations Manual, which contained contradictory sections. On the one hand, chapter 8.18.3.4 emphasized the role of the ATC and describes the TCAS as an "additional aid",[BFU 15] whilst chapter 8.18.3.2 forbids manoeuvers contrary to the TCAS

Since that accident, it was made official procedure for all flights to follow TCAS, ignoring ATC when a TCAS RA is in effect.


Did WW2-era aircraft have constant-speed or variable-pitch props? This is slightly related to my other question on variable-pitch controls.

I want to know if WW2-era aircraft typically had variable-pitch or constant-speed propellers. Variable-pitch lets the pilot adjust the propeller blade pitch. "Constant speed" is the same as variable-pitch, but the engine does it automatically to keep the best performance at various airspeeds. This also lets the engine keep a constant RPM so it can always run at its optimal RPM, also increasing efficiency.

Anyway, were such things seen in WW2? Were they the norm, or the exception? Did single-engine aircraft have them, or were they more common on multi-engines?

I'm interested in all the nations who made aircraft, especially USA, UK, USSR, Germany, and Japan. And I'm interested specifically in the combat aircraft, like fighters and bombers, not necessarily the civilian transports of the era. This will give us a good idea if the extra complexity and weight was acceptable for combat aircraft of the era.

Variable pitch (with feathering) was virtually universal on (at least American) multi-engine fighters, bombers, and transport aircraft even early in the war: the DC-2 had feathering variable pitch, and it entered service in 1934.  The P-38 had feathering and variable pitch, and was in service before the US entered the war.

Constant speed propellers were also found on many single engine combat aircraft -- one was the Hellcat, which entered service in 1943, though it's very possible the technology was introduced earlier.  The P-47 Thunderbolt also had this feature.

When you're talking about aircraft that weigh several tons and need to deliver thousands of horsepower through a propeller, especially for combat operations, the weight and cost of variable or constant-speed propellers became negligible by comparison to the cost of the aircraft or the cost of fielding a losing design.


Please tell me which trainer aircraft is this? This trainer aircraft was spotted by me on a video on youtube, which said they were at the Lahore Flying Club. I really could not tell what aircraft they were on. If anyone can tell me, that would be great. Its some Cessna but which?

link to the youtube video:

Picture from the video attached.

Its a Zenair Zodiac CH601 XL you can see the registration code on the side and if you watch the video a bit more they show the inside of the cockpit and you see the registration code a bit more clearly, which you can look up here. It appears to be owned by this flying club.


Why does the glideslope use UHF when the localiser uses VHF band? Why does the glideslope use UHF, while the localiser uses the VHF band?  I mean, the glideslope could have used the VHF band too, or vice versa, so why is it so?

The higher the frequency the smaller the transmitter, so fitting the G/S on a small tower near the touchdown zone becomes practical. Compared to the large LOC array at the other end of the runway.

  [Of] the advantages of using UHF frequencies for glideslope operation is only a small antenna and ground plane is required. As a rule of thumb, the higher the frequency, the smaller the antenna can to be (avionicslist.com).

Here is a table for the localizer and glide slope frequency pairing (fcc.gov).

As for why not UHF for the LOC, my understanding is the range. A pilot can receive the LOC farther out than the G/S (8 miles more).


Black boxes: great for crashes on land. How about additional "floaties" for water crashes (low-tech, light, cheap) Without getting into the mess of redesigning existing Flight Data Recorders, I have a simple proposal that I think would help in deep water crashes.

I propose that several floating cushion sets be distributed around the plane (tail section, along fuselage, etc.). These FDR floaties would be about the size of a seat cushion, but they'd be wrapped in a water soluble cover. When a plane crashes into the water, if the plane breaks up, then several of the cushions would float to the surface. When the cover dissolves, several folded arms open up making it much bigger exposing a orange-nylon covered mesh with an aluminum sheet embedded. This would be easier than seat cushions to see from satellites and planes, and the aluminum layer would reflect radar and make it easier to find.

This alone would help find water crashes sooner, but if you add a simple USB memory stick in the center, then have data similar to the current FDR's being fed into it, then finding one of the floaties would give quite a bit of information including the final GPS coordinates before the crash.

These devices would be light and cheap. I'd think current planes could be retrofitted very cheaply. The only challenge would be the wiring needed to connect to the main FDR or the nearby data splitter. But just putting a few in the tail section alone would end this madness of having to find FDR's on the seabed to get a better idea of what happened.

Wouldn't this be easy to implement without disturbing current FDR use and development? These would be destroyed in a fiery land crash, but that is not their purpose. This is just so we can find plane crashes in the sea when we don't know precisely where they went down (and to get basic data when the black boxes are too deep to get to immediately). Malaysian flight 370 and Air France Flight 447 would have both been greatly aided if these floaties were in those planes. What do you think?

The first thing that comes to mind to me is that they'd have to be firmly attached enough to not come off in flight, yet somehow detach easily when in the water. They'd also create additional drag, which - especially to commercial air carriers - translates to money lost (additional fuel).

There would also need to be some connection (wired or wireless) to continuously transmit data to them (I'm assuming that you're proposing several of them).

Finally, the whole point of the FDR's housing is that it's rigid enough to withstand explosions and impact, yet the floatation proposal requires that there be some sort of expanding material that'd inflate upon contact (or presumably submersion - consider weather/rain) with water.

General aviation aircraft use ELTs (Emergency Locator Transmitters), which are designed just to notify of the location of a crash incident. They are required in the U.S. for general aviation and commercial aircraft, but unfortunately not for scheduled flights by an air carriers.

I get the impression that the trend is probably towards having more data transmitted real-time during the flight (think Air France stall/crash) of systems monitoring data and location such that location and recovery of more data-intensive logs (voice recorder) would be more efficient.


Could two GE9x engines power a 747? These new GE9x engines are huge and extremely powerful, but could two of them power a B747–8?

It is possible for some engines to power the original 741s but I am mainly interested in the B748.

The curently operational GE90-115B engine is somewhat more powerful than the listed specs I've seen for the GE9X, at 115,540 lbf thrust vs just 105k.

That engine powers three current variants of the 777. Interesting to note that the 777-300ER is actually 5% heavier than the original 1966 version of the 747. Two of the 90-115 also have more takeoff thrust (~230k lbf) than the original 747-100 (~175-205k lbf).

So, in theory, two modern engines can power a 747, but only the original, not the 747-8.

Twins have higher thrust requirements, as they have to be able to take off with just one engine, while quads can use three. The 741's wings aren't as effective as the 777's, so even the 741's 5% lower weight might not quite suffice. But as the "741-twin" could use less fuel than the original, it could still maintain the 741's original payload and range.

There are other changes required for a twin and for ETOPS, so it won't be just a re-engine. All in all, a twin-powered aircraft with the early 747's fuselage, general layout and performance, but some control modifications, should be possible.

The 748 is a much heavier aircraft than the 741. It could in theory be ferried with the power of two GE9x engines, but its total weight would have to be restricted to less than that of a 741. That cuts its useful load in half - essentially, half the aircraft is now useless.

If operated, it wouldn't be able to fill all its seats or fly its full range. Such an aircraft would have no value for commercial operations. The only uses for it I can think of would be an oversized vomit comet or carrying something extremely light. And there are special aircraft with oversized fuselages for that like Airbus Beluga or Boeing Dreamlifter.

The minimum a modified 748 could operate commercially with is three modern engines. With two out of three GE9x running it would get 210,000 lbf of thrust, which is marginally above the 200k that three of the 748's engines produce.

TL;DR version: Two GE9x could keep a 748 in the air, but not in the black.


Where does Google Flights get its pricing information? I was wondering if anyone knows how I can get flight data in mass.  Specifically, I'm looking for price, time, and airports involved.

Do you know where Google, Expedia, and the likes get their flight information from?

Google bought an airline pricing optimization
company called ITA Software that has interfaces with the GDS systems.


How is the type of deicing fluid chosen and how much time is required for application? From my understanding there are 4 different types of deicing fluids.

How exactly is it determined what type of fluid needs to be used?
How much delay does every type of fluid cause on average?
What is the holdover time for each fluid type?

I am building software for a school project and with the software I want to determine if deicing is needed for a flight.

I'm mainly addressing your "with the software I want to determine if deicing is needed for a flight."

There are three possibilities for whether deicing is needed or not, which are based primarily on actual and expected weather conditions (both at the point of departure, enroute, and possibly at the destination) and the airplane's capabilities:

Deicing is obviously not required
Deicing might be required, but is not obviously required
Deicing is obviously required

No reasonable pilot is going to request deicing in a case where deicing is obviously not required, so that leaves us with the other two. (Remember that deicing costs the airline money, and a pilot who regularly requests deicing for a short local hop in the height of summer is probably going to get talked to by their boss about it.)

If deicing might be required, it's basically at pilot's discretion, likely supported by company standard operating procedures and airplane manufacturer recommendations.

If deicing is obviously required, any pilot who does not request (and wait for) deicing before beginning the takeoff roll is delinquient in their duties, and is putting both the passengers, the crew, and the airframe at risk. Unfortunately, there have been crashes where a decision to not deice in conditions that required deicing were a major contributing factor.

Thus, if deicing is determined to be needed, yet not requested and waited for, then the only safe alternative remaining is to stay on the ground; effectively cancelling the flight.

Consequently, the options are:

Deicing is not needed before takeoff
Deicing is needed, requested and waited for before takeoff
Deicing is needed but not requested, thereby precluding safe execution of the flight

If it is known while the aircraft is still on the ground that a flight cannot be done safely, then the flight should be cancelled.

A flight cancellation can, simplistically, be modeled as an infinite delay.

Therefore, we can conclude that if deicing is needed, then waiting for deicing is required, and whatever this means in terms of additional delay will simply have to be tolerated as a necessity for the ability to safely undertake the flight. It's really not different from inoperative critical flight instruments; if, for example, all attitude indicators or airspeed indicators disagree, you're just going to have to wait to get that fixed, too.

In an ideal world, the choice of whether or not to deice the airplane is entirely unrelated to the time required to deice the airplane.


Why are modern aircraft wings often pointed instead being more rectangular? When viewed from the Z axis (above or below), why are modern aircraft wings often pointed as they get towards the wingtips instead of maintaining the same surface area for their entire length?

This seems to be a design change in the last 50-60 years, as earlier designs typically featured more rectangular wings.

Extra points if you can explain why some rectangular wings feature rounded tips, with the maximum protrusion halfway between fore and aft of the wing.  This design was very common for biplanes.

Rectangular wings are easy to build: You need just one rib size and can repeat making it several times, using the same jig. Early airplanes needed a lot of manual assembly by semi-skilled workers, and it made sense to simplify the task.

SE5a wing under construction (picture source)

However, to produce the least amount of induced drag, the downwash behind the wing should have the same angle over the whole wingspan. This can be achieved with washout, but then the washout needs to be tuned to one angle of attack. Change the angle of attack and your lift distribution over span is producing more drag than necessary. To overcome this problem, elliptic wing planforms were used, but they are complicated to build and prone to tip stall. This is when the wing tip loses lift first during a stall and causes the aircraft to roll violently. If this happens close to the ground, a crash is inevitable.

Therefore, designers soon settled for something wich resembles the elliptic planform, but leaves more area at the tip such that it has less loading and more stall margin. Especially when this wing is covered with sheet metal, it makes sense to have only one direction of curvature, thus trapezoidal planforms soon became the preferred way of building wings once aluminium became the primary structural material for aircraft.

The SB-11 glider uses a rectangular inner wing and a trapezoidal outer wing. This way, the mould for the inner wing could be used for the left and right side, making construction easier (picture source).

The trapezoidal wing is also helpful in another respect: Cantilever designs have high bending moments at the wing root. If the root has more chord, the spar can be made thicker, and if the area at the tips is smaller, less bending moment is created for the same lift. The bracing of biplanes takes care of root bending moment, but when monoplanes emerged, the rectangular wing lost most of its benefits.

Now for the rounded wingtips: They are an attempt to get the wing closer to the ideal elliptic planform without losing the benefit of a constant-chord wing over most of the span. Much of the wingtip design is also about aesthetics, and some people hold quasi-religious beliefs about the benefits of a particular wing tip shape. For metal wings, wingtips can be made by pressing the aluminium sheets for the top and bottom part in shape and riveting them together since the aerodynamic loads on the wing tip are low. Wingtips and fairings were also among the first parts on aircraft to be made with composite materials, which make three-dimensional shaping much easier. Closer to the root the wing needs much more strength, and here the trapezoidal planform is still the best compromise today.


Where does the difference between calculated and actual groundspeed come from? I'm a paragliding pilot. At school we learn that the trim speed of a paraglider is about 38km/h airspeed, the accelerated airspeed is about 45km/h and the minimum airspeed is 22km/h - being inside the weight range of the wing.

If I fly with a headwind of 25km/h, my groundspeed should be: 38-25=13km/h.

Well, from my flying experience (1200 flights in total) with that kind of headwind I never went forward +13km/h groundspeed but much less, near the minimum relative speed (22km/h).

Why there's a difference between the calculated groundspeed 13km/h and the actual groundspeed?

I have a little paragliding experience. While only a tiny fraction of yours, I think I can answer your question, which boils down to: data accuracy.

The trim speed of a fixed-wing aircraft would depend on its weight. Without accurately measuring the pilot's weight (FYI the measurement in small aircrafts is precise to pounds / kilograms) and plotting that against a chart, the speed you were told in school is only an approximation.

I (like others in the comments also) question the accuracy of your speed data.

To accurately measure forward airspeed, you'd need a pitot tube pointing in the right direction.
Or you can use a wind measuring device which measures speed and direction
To measure your ground speed accurately you'd need a GPS.
To combine the two (wind speed + ground speed), you'd need some sort of computer to do the computation, either in real time or with recorded data.
The ground station only measure wind speed at ground level. When you're up in the air (albeit relatively low compared to aircraft), the wind can be different.


What does the code FU1FU2FU5 mean in this metar? In their METAR, CYPK reported ... 25SM FEW037 SCT050 OVC250 21/15 A3016 RMK FU1FU2FU5 DENSITY ALT 400FT.

Since it's quite smokey out, I would have expected a simple FU in the weather section after visibility.

I'm wondering what FU1FU2FU5 is about. According to the remark format at http://meteocentre.com/doc/metar.html it should be "layer type and opacity in oktas". Is this just the way to say "sky covered by smoke"?

It's indeed the layer type and okta, but in the remark the layer type is repeated for each reported cloud (smoke) layer. From your example:

FEW037  →  FU1
SCT050  →  FU2  →  1+2=3
OVC250  →  FU5  →  3+5=8

The oktas of the layers are added, that's how OVC is shown as 5 and not 8, by adding the previous oktas it does become 8.

FEW = 1 to 2
SCT = 3 to 4
BKN = 5 to 7
OVC = 8

Similarly for CYCD:

METAR CYCD 012200Z 34010KT 12SM BKN038 BKN051 30/11 A3012
RMK FU5FU2 VIS LWR N-E SLP201 DENSITY ALT 1600FT=

BKN038  →  FU5
BKN051  →  FU2

When no remark is needed for the smoke (French: Fumée), the FU code is placed before the remark:

METAR CYBD 012200Z 29007KT 8SM FU FEW240 28/13 A3019
RMK CC1 SLP225 DENSITY ALT 1400FT=

According to Wikipedia, this is how Canada handles the remark section. Here is what navcanada.ca says:

  Where observed, the obscuration and cloud type amount for each
  reported layer is included in remarks. It may exceed 8 oktas if a higher
  layer is observed through transparencies in a lower layer

(Emphasis mine.)


What's the difference between a Sole Means Navigation System and a Primary Means Navigation System? For bonus points, how you define a supplemental means navigation system?

Sole means it is the only system, primary implies there is a secondary or even tertiary system, and supplemental means it supplements another system.


Would the wings of a Boeing 787 be snapped off in the same turbulence in which a DC-8 lost an engine and parts of a wing? From forbes.com:

  In 1992, a DC 8 cargo aircraft suffered turbulence so severe over the Front Range of Colorado’s Rocky Mountains that its left outboard engine was completely ripped off as well as some 12 feet of its left wing’s leading edge. Mercifully, the pilot was able to make an emergency landing at Denver International.

If a 787 was put in the same turbulence as the DC-8, would the wings snap off? The DC-8 is from the '50s while the 787 is a new aircraft.

It's very likely that the 787 would have less problems with turbulence than the DC-8 did.

The wings of the Boeing 787 are more flexible than the DC-8, and that flexibility will damp the immediate impact of turbulence. More important, the Boeing 787 has a gust alleviation system that reacts to turbulence by counteracting the induced accelerations using the control surfaces.

Note that the aircraft certification standards have changed a lot since the DC-8 was certified. Originally the focus was very much on the maximum g-forces the wing could sustain, but this is not a very good measure for turbulence. The g-forces encountered in turbulence are the result of a combination of the turbulence itself and the aero-elastic response of the aircraft. Using a more flexible wing and gust alleviation systems will result in a much smoother ride (less g-forces) than a traditional very rigid wing.

Currently the certification standards define, in addition to a required g-force, the characteristics of the turbulence that the aircraft has to sustain. For example, see the FAA's regulation for large aircraft, FAR Part 25, Sec 25.341.
This takes into account a range of characteristics of turbulence that can be encountered as well as the dynamic response of the aircraft to that turbulence.

Apart for aerodynamic and structural differences between the DC-8 and the Boeing 787,  better understanding of (mountain wave) turbulence, better weather prediction, better reporting of turbulence by aircrew (simply because there are more flights) and better weather radars on aircraft have reduced the risks of encountering turbulence since the DC-8 era.


What is the average g force experienced on takeoff for an ultralight? How much g-force is made on an ultralight during take off if its upward velocity of 2m/s?And what's the average g force experienced during takeoff on an ultralight?

I fly part 103, specifically a Hy-Tek Hurricane. I also have a G meter on board. It is a Dynon D2, which features an artificial horizon (attitude indicator) and also a G meter. The average G's on takeoff is pretty small, usually around 1.1 to 1.2 Gs. I can also tell you it is impossible to pull anything over 2 G's during takeoff. I actually performed this test in the air at 2000ft, straight and level at full throttle (simulated takeoff from 2000ft?) at about 55mph, then pulled the stick back all the way in about 1/4 of a second until I was nearly vertical. The highest recorded G reading during this maneuver was 1.8 Gs. Of course all ultralight aircraft are different. I would NOT recommend performing this test from an actual take-off from the surface. Also you should consider that by performing the test at 2000ft, I was not in any kind of ground effect, so you would have to factor in that little bit of extra lift cushion you would get from an actual takeoff from the surface, but I would guess the extra lift component is probably small, so that is why I estimated 2 Gs max.


Could a UAV ever be hacked and piloted? I am currently reading a book at the moment, and I got to a point were a UAV was hacked, piloted, released its pay load and crashed, could this ever happen in real life?

Not only is it possible to hack a UAV, but it has already happened. In December 2011 a US RQ-170 recon drone landed in Iran after being hijacked by Iran's security services, possibly with Russian help. This was as much poor security implementation on the drone as clever hacking on the part of Iran.

As for whether it would be possible to take over an armed drone and fire its weapons, it would certainly seem so.


Why is there no "reverse sensing" on a horizontal situation indicator (HSI)? When we use this awesome instrument for navigation (not only for ILS/LOC), it is said that there is no reverse sensing (except for back course thing). I kind of understand why pilots are confused when we use conventional VOR, and now I want to know why there is no reverse sensing? How does it work? Can anyone help me out?

Essentially because you turn the instrument upside down and read it normally.

On the back-course, the signals are reversed. That is a property of the ILS signal. When using traditional ILS/LOC instrument, the needle moves right when it senses more of the right signal, but since the signal is now on the left, you get reverse sensing.

On the HSI, the needle still moves right when it senses more of the right relative to the arrow when it senses more of the right signal. However, the needle points in the selected heading and is rotated with compass. So when you fly a back-course, you dial the normal course of the ILS and since you actually fly opposite direction, the arrow points down and right relative to it is left. And you get normal sensing.

For VOR, the situation is similar. In VOR, the needle moves normally if you are flying the heading selected and it moves in reverse if you are flying the opposite heading. And when you are flying the opposite heading, the HSI arrow points down, reverting the sensing back to normal.


Does the A320 autopilot work in flight with both engines off? For a series of simulator sessions to determine the speed polar with students we plan to cutoff both engines in our A320 simulator, but we still want to use the autopilot to control speed (in theory, the autopilot would adjust pitch to keep a desired speed). Obviously, some modes, like altitude hold, positive vertical speed and autothrottle modes will not make sense in such a scenario.

In a real A320, can the autopilot (or selected functions only?) be used (activated) when both engines are cut off? (for example, after a double bird strike)? Assume APU running, so electrical power is guaranteed.

You want to assume the APU is running. The FCOM says:

APU start is not available for 45 s after the loss of both engine generators. This 45 s delay prevents any interference with emergency generator coupling.

So the APU can be started following dual engine failure after waiting 45 seconds.
With the APU running, the green (G) and yellow (Y) hydraulic systems will also be powered, so AP1+2 should work. (The Y hyd will run via the elec pump on AC2, and with Y pressurized, so will the G via the power transfer unit.)
Descending by maintaining a speed using pitch control is called OPEN DES in an Airbus (FLCH for Boeings). OPEN DES doesn't require the A/THR to be working:

The engine-out descent strategy requires disconnection of the autothrust, and descent in OPEN DES mode.
Disconnecting the autothrust prevents an automatic setting of THR IDLE; therefore, the autopilot will fly the target speed in OP DES mode, with a thrust manually selected by the crew.
When reaching the FCU-selected altitude, or whenever normal descent is resumed to a lower altitude, reengage the autothrust.

The flight law reconfiguration table in the FCOM says the AP is lost when any of the items in the dashed box below fail:

I tried to disprove it, but it seems like with the APU started, an OPEN DES should work. (Report back please.)


Why don't short-haul regional jets go for composites? We have seen Airbus and Boeing going all the way for composites on their A350 and 787, but when it comes to smaller planes like the Embraer E-jets or the Bombardier C-series, they choose to use aluminium, I'd like to know what are the reasons for this to happen, why is more cost-effective?

The C-Series has a carbon wing box.  The fuselage is aluminum but is a newer fairly exotic aluminum lithium alloy that is a bit lighter than 2024.  The decision to go with aluminum for the fuselage was mostly development and manufacturing cost (a fuselage requires a massive autoclave and it's development is fairly high risk the first time around) and ease of repair (the fuselage takes the brunt of vehicle damage on the ramp, especially on smaller aircraft) compared to carbon.

Cost is probably the number one driver.  They stuck with things like bleed air services, and wisely decided to avoid lithium ion batteries (Boeing had to use L-ion with the level of electric services).  The C-Series is overall a more conservative design than the 787, and it still almost broke the company, which was forced to give the airplane to Airbus for free or go under.

The E-jet is more or less the old 190 with a complete systems state of the art revamp (and I believe a new airfoil) that make it more or less a smaller C-series system wise without the risks of composites development.  An even cheaper choice, and a wise one on Embraer's part.


For taking-off and landing in a DHC-7, what elements can be used in writing a novel? What cockpit elements can be used in writing a novel for taking off and landing in a de Havilland Canada Dash 7 from a short runway in Rothera, Antarctica? Including the names of those switches overhead, and the throttle and the steering stick/wheel?

(wikipedia.org) Viewing the full resolution image from the link might help you notice things to use.

Steering the yoke right and left controls the aircraft's roll. Pulling/pushing the control column controls the aircraft's pitch (nose up/down).
Radio altimeter is used in landing, it offers precise measurement of height above ground.
Landing gear lever, down is wheels down.
Airspeed indicator shows how fast the plane is going. 12 o'clock position, not going anywhere. Moves clockwise with speed increase.
Flaps lever: fully down for take-off/landing from short field.
Power levers: push away from you, full power. Pull all the way back, full reverse, which is useful in stopping the plane especially on ice. Don't use the brakes in your novel if the runway is icy.
Trim wheel: pilot will use it to fine tune the approach. And after take-off to make pulling the control column easier. You can watch it on YouTube (head-mounted GoPro).


Why would one cylinder on a Continental O-200 run cold at idle? I have a Luscombe with a Continental O-200 engine. The #4 cylinder is running cold at idle, does anyone have an idea why? The other three cylinders are running fine.

Some extra information:

The engine has only 300hrs SMOH but it hasn't run for two years and it's just had some maintenance work done (carb, filters, plugs)
Cylinder #4 is cool to the touch, the others are too hot to touch
A mag check seems normal (expected RPM drop on both mags)
A compression check seems normal (76/80 on #4 cylinder)

A: Idle circuit is set too lean and the cold jug is not firing.

B: Intake leak, causing same condition as A.

C: A little of both.

I know that a lot of people will lean out their idle mixture, by adjusting the screw on the carb, to reduce plug fouling with 100LL fuel (since leaning with the cockpit mixture doesn't do anything in the idle range).  You can tell when this has been done because the engine doesn't have the little RPM bump when pulling idle cutoff, and also it may require extra prime to keep running when cold.

Also, please write your questions with a bit of structure and grammar.  That stream of consciousness no-grammar style (that a lot of people use in emails out of laziness) is a total pain to read and interpret.


What are the rules for flying drones in National Recreation Areas? National Recreation Areas allow powerboats on lakes and roads for vehicles, so can drones fly in this area? Can model aircraft fly in this area? Can model boats be used on the lakes or rivers? Can rafts be used in the rivers?

The operation of UAS in these areas is regulated by the National Park Service, but, according to a 2014 memorandum, this authority has been delegated to the individual parks themselves.  You would have to check with the park itself.  Further information is available in an NPS article on the topic and in the NPS rules and regulations section.

For an example on the state level, the Pennsylvania Dept of Conservation and Natural Resources has designated flying sites in six flying sites at a selected number of state parks.  If I go to the website for the Allegheny Portage Railroad (a park managed by the NPS), they have a specific statement on UAS usage in their policy compendium.

Boats and such...that I'm less sure of.


Can I execute an ILS approach using a NAV CDI with LOC signal only? I have been flying a small Cessna airplane that has a COM/NAV NARCO MK12 equipment with CDI (lateral needle only).

This CDI does not incorporate a horizontal needle to provide vertical guidance, so there is no glide-slope indication for ILS.

Last time I tuned the LOC frequency of an ILS procedure and the CDI captured the LOC signal. The audio panel also captured the O M I markers.

My question is if it is legal to execute an ILS approach "with LOC" only limitations, as published in the approach plate (since the airplane does not have any GS information).

No, you cannot execute an ILS approach without an ILS glide slope indication as the primary form of vertical guidance.

Even if you could supplement it with alternatives (WAAS, GPS software, etc), they are not recognized as the appropriate standard of vertical guidance required for an ILS approach.

Many airports that have an ILS also have LOC (localizer-only) approaches.  If such an approach is published, you could certainly fly it with only the use of the localizer, but then again, it is not an "ILS approach" it is a localizer approach.

The localizer -only approach will have different minimums which will be based on your altitude at a published minimum descent altitude rather than a decision height.

If no localizer approach is published, then you'd need to find another method or airport.


Do modern airliners have oxygen sensors in the cabin? I know that airliners have pressure sensors to check the cabin pressure, and thus check if we can breathe (and get enough O2) inside it so we don't get hypoxia. But that got me thinking:

Is there any oxygen sensor to check if there is enough O2 inside the cabin?
Is there any situation (emergency or not) in which some other gas could pressurize the cabin and lower the O2 percentage inside it?

While it would not significantly affect the O₂ percentage one thing that must be tabulated on a cargo aircraft is the amount of dry ice loaded. Dry ice is very common in packaging to keep perishable shipments cool during transport. Since dry ice sublimates into gaseous CO₂ as it warms there is a limit to how much can be loaded into an aircraft. If there is too much there's a possibility that the pilots could be overcome by gas trapped inside the plane. It's a rather insidious threat because you can't smell it so you would only realize something was wrong when you started feeling physiological effects.

An O₂ sensor would not help since pilots would be overcome long before it made any detectable difference in O₂ levels. AFAIK there are no sensors for CO₂ either. The amount of dry ice loaded is carefully tabulated and pilots who fly cargo containing dry ice are aware of the possible hazard and how to recognize symptoms of CO₂ poisoning.


What certificates/medical are required to fly in Japan? I am FAA certified, but my medical certificate has lapsed. Would my pilot certificates and a fresh medical enable me to fly in Japan?

With a US license, you are allowed to fly US registered (n-registered) airplanes everywhere in the world.
Find a US CFI (in Japan) that can get you current and start flying.

The bigger problem might be, to find a Medical Examiner in Japan that is allowed to do medicals in Japan. My first search, at the FAA website (https://designee.faa.gov/SelectTypeOfSearch/SelectTypeOfSearch), didn't show anything.

Not sure if BasicMed works for you though.


Where can I find the active time of a MOA on the VFR chart? I am trying to find out the time when the HILLTOP MOA is active and its elevation. Where is this information located in a VFR chart?

It's in a table on the border of the sectional.  Looking at the Chicago sectional, this is along the top....


Is a 20% forced transition in xfoil similar to adding a vg? Is a 20% forced transition etc. in xfoil similar to adding a vg?

I understand a 20% forced transition in xfoil, is tripping the boundary layer from laminar to turbulent.  Isn't that what a VG does?

A classic shaped naca foil like 2415, has a max cl of 1.5.  I understand that vg's usually add a cl of about 0.5-0.7.

So... if I force a transition to turbulent at about 15-20% of chord in xfoil, shouldn't the max cl of a classic foil go up from 1.5 to about 2?

It doesn't....?!?

No

It is more like putting a turbulator (such as a trip wire) there. Vortex generators will create a small vortex (hence the name) which puts much more energy into the boundary layer. XFOIL has no mechanism for simulating vortex generators.

Adding a forced turbulent transition will weaken the boundary layer downstream of its natural transition point, so it will tolerate less pressure rise. I assume you put them on the upper side: Now the airfoil will stall a bit earlier (at a lower angle of attack and lift coefficient).

15-20% is an unusual location for a turbulator, especially on the upper side. Their best location depends on the Reynolds number and the pressure distribution. On gliders, they make most sense on the lower side at around 80% of chord. On the upper side they might help a bit in part of the polar when placed at around 50%.


Are there any EU/EASA regulations surrounding aviation software? A great question's been asked: Is there any U.S. / FAA regulation that could apply for aviation software?

This is interesting to me as a programmer and aviation enthusiast, but being based in the UK,  I'd like to know if there any EASA regulations surrounding the creation of software for use in the aviation industry?

If we speak about airborne software, the main document is the RTCA/EUROCAE DO-178/ED-12 currently at the "C" version: Software Considerations in Airborne Systems and Equipment Certification: if you want to certify (and thus commercialize) your software for flight, this is the main document to read.

Depending on the scope of the software and the design/development process there might be different supplements (see here):

  DO-330 Software Tool Qualification Considerations
  DO-331 Model-Based Development and Verification Supplement to DO-178C and DO-278
  DO-332 Object-Oriented Technology and Related Techniques Supplement to DO-178C and DO-278A
  DO-333 Formal Methods Supplement to DO-178C and DO-278A

It has been prepared by the RTCA/EUROCAE joint committee and approved by both FAA and EASA under different names, but the content is the same.

As @Greg mentions, these documents are not freely available


Would this mechanical apparatus be a new means of creating aerodynamic lift? I recently came up with a conceptual idea for creating aerodynamic lift which would use an unconventional centrifugal impeller. I would like to know if this conceptual design of mine is something that has already been built and tested in the past.
I have emailed this design over to some aerospace historical societies and aerospace institutes inquiring if they know if this particular design, or something very similar to it, has already been built and tested by an aerospace company in the past. They replied back saying they had not seen this particular design. So, I thought it would be worth asking the Aviation community on Stack Exchange if anyone has already seen this particular design.
I have created some CAD drawings (shown below) to illustrate what this mechanical apparatus would probably look like. Its primary components would be a centrifugal impeller with two rows of blades, a motor to turn the impeller, and a curved panel which would be fastened to the fuselage or to a wing of an aircraft. I want to point out that the curved panel would not rotate along with the impeller, rather the centrifugal impeller would rotate around the curved panel.
This mechanical apparatus would have a simple working principle. The centrifugal impeller would have an inner row of blades and an outer row of blades. The inner row of blades should create high air pressure along the bottom surface of the curved panel and the outer row of blades should create low air pressure over the top surface of the curved panel. This should result in aerodynamic lift.
EDIT
I am thinking now that it may be better that the outer row of blades be backward-curved in order to reduce turbulence and to maximize the static air pressure drop along the top surface of the curved panel.

Would this mechanical apparatus be a new means of creating aerodynamic lift?

Yes, this device would produce some thrust. If oriented properly, this thrust could be used to lift a weight. But it would be extremely inefficient when compared to a standard airfoil, such as a wing or helicopter blade.
What you've basically created is a centrifugal pump without a case. Air would enter the "front" of the device (assuming the motor is the "back") just like a regular centrifugal pump, but without a case, it would be sprayed in all directions, including at an angle out of the "front". The curved panel would partially block the radial flow of air upward, creating a net upward force. But the fact that air exits at all angles, not just straight down, means that the various flows would partially cancel each other. What's worse, a lot of the air mass that emerges from the "front" would be drawn back into the incoming air stream, which would consume some of the motor's power but wouldn't contribute to the net thrust at all.
In short, I would be very surprised if this device could match even 1% of the performance of a simple ducted fan of the same power rating.
It's kind of hard to explain what I mean in words, so, here, have some bad, hastily-created images instead:


What is Tropopause height, and how is it determined? I have seen the term "Tropopause height" used in a flight navigation plan. What is it and how is it determined?

According to Wikipedia, the World Meteorological Organization defines tropopause as

  The boundary between the troposphere and the stratosphere, where an abrupt change in lapse rate usually occurs. It is defined as the lowest level at which the lapse rate decreases to 2 ˚C/km or less, provided that the average lapse rate between this level and all higher levels within 2 km does not exceed 2 ˚C/km. Occasionally, a second tropopause may be found if the lapse rate above the first tropopause exceeds 3 ˚C/km.

The tropopause height varies with latitude and season. The variation with latitude, based on annual mean conditions, is shown below:

Image from das.uwyo.edu

Troposphere can be identified only if the lapse rates (the rate at which atmospheric temperature decreases with increase in altitude) in the stratosphere and troposphere are known. Also, weather phenomena like thunderstorms shift the tropopause. As a result, the height of the tropopause is forecast based on localized weather conditions, and is not a fixed boundary.

The International Standard atmosphere, however, defines tropopause as lying between ~11,000 and 20,000 meters (geopotential altitude) above MSL.


Why are fuel tanks located in wings? Passenger aircraft have fuel tanks in the wings. Why?
What are the advantages and disadvantages of this location ?

examples of disadvantages I would suspect:

added weight increases the structural load applied to the wings
different gravitational forces and wing-bending between full and empty tanks result in repeating stresses shortening the aircraft life-span
higher risk of catastrophic damage to wings in case of in-flight fuel ignition
higher risk of fire when lightning strikes a wing

Several advantages:

Wing structures are hollow and voluminous in order to provide structural rigidity against flutter and carry flight loads.  This provides the space needed to store fuel.
On a conventional aircraft, placing fuel tanks in the wings places the fuel mass very close to, or on, the center of lift.  This dramatically reduces Cg shift during flight and reduces the size and weight of the tailplane to maintain stable flight.  It also reduces Cg shifts due to sloshing of the fuel inside the tanks, due to the limited constraints of longitudinal travel for the fuel in the tanks.
In the event of a crash landing, having the fuel in the wings keeps it away from the cabin and the occupants, reducing risks of cabin fires.
The weight of the fuel reduces the loading moment on the wing roots, reducing the weight of the structure needed to support the aircraft during flight.
Fuel stored in the wings either partially or completely eliminates fuel storage in the fuselage, leaving more room for passengers and cargo.

Disadvantages:

1) Fuel sloshing with in the tanks laterally as a result of turbulence, or uncoordinated flight, can lead to lateral weight shift and potential lateral instability.   At low quantities of fuel, and in prolonged uncoordinated flight, there is a chance that the engine can suffer fuel starvation simply because the fuel has flowed out of the sumps in the tanks These problems can be alleviated with proper fuel tank baffling and the use of feeder hoppers fed by the main tanks which the engine drinks from.

2)  On aircraft which utilize a siphon feed fuel system such as low wing aircraft, the fuel cannot be evenly siphoned from both tanks at once.   This is a particular problem in single engine aircraft, where separate fuel systems are not dedicated to one engine in particular.   In such cases the engine will feed off either the left wing tank with a right wing tank  and this is controlled by means of a fuel selector valve in the cockpit. On aircraft that do not have automatic fuel management systems, engine fuel feed must be manually selected.  Care must be taken to alternate feed from both tanks periodically to prevent a lateral imbalance and fuel quantity. Additionally this fuel tank switching schedule, if ignored long enough, can potentially lead to fuel starvation of the engine and a forced landing.  This is particularly problematic in the low wing light single engine aircraft such as the Piper PA-28 or Cirrus SR-2X, especially if the pilot has recently transitioned into this airplane after flying high wing aircraft, which use gravity feed fuel systems, and allow the engine to feed from both tanks at once.  Larger single engine aircraft like the TBM have automatic fuel tank switching systems to address this problem.   Large multi engine jet aircraft have dedicated fuel management systems which address these problems.


How are aviation regulations treated on a global stage? I know that the two large aviation regulatory authorities are the FAA and EASA, but every country also has its own civil aviation authority.

Focusing on airliners that need to operate all over the world, are they designed to meet FAA and EASA requirements only or are they subject to the regulations of every country in which they operate's regulatory authority?

Also, where does ICAO come into the picture?

I'm going to answer this from an aviation safety regulation viewpoint only. There are many broader considerations, such as criminal juristictions, employment, and environmental laws, which will have differing answers. I'll also add that my experience is with the Australian situation, but I don't think it varies too much around the world - happy to be corrected.

So with all that considered, the answer is... sort of both! The short answer is that they must follow the direct operating procedures of the country they are flying in, but some "back office" regulations do not apply.

Firstly to ICAO. This organisation isn't really concerned about individual airlines. Their primary purpose is to set international standards for the individual regulators to implement. But these Standards and Recommended Practices (SARPs) are not enforceable - individual states can simply lodge a 'difference' and continue to do their own thing. Another important job of ICAOs is to basically regulate the regulator, giving them a rating on how safe they are. The FAA and EASA also conduct their own audits for the same purpose.

Each airline needs to be certified in its home country with an Air Operators Certificate (or Part 121 Certification, or the many other variants around the world). Part of this process involves approving pretty much every single procedure the aircraft would ever do in normal operations - including the procedures at international ports. That means that for an Australian airline wanting to fly to LAX, the Australian regulator CASA has to inspect the port and approve it for use, checking that what the airline has proposed complies with the local airport procedures.

So, once the operations at LAX have been approved by CASA, the airline then approaches the FAA for a Foreign AOC/Part 121 approval etc (I'm not certain of the US naming convention). This certification process for a foreign certificate is almost always no way near as thorough as the full version. A lot of it depends on the home countries regulator and their status with ICAO or the FAA/EASA. If the FAA knows that the oversighting country is up to scratch, issuing the foreign certificate might just be a tick and flick exercise.

This 'foreign' status of this approval is key to your question, because many regulations are written like "the Part 121 operator must..." and NOT necessarily "the Foreign Part 121 operator must..."

Take a breath now and try to follow this. In the majority of occasions, the foreign approval says that the airline must operate in accordance with what has been approved by CASA. But, the procedures which CASA has approved are already tailored to LAX-specific operations! So you can see that the Australian airline has to obey the conditions of its FAA approval, which is to follow the operations set by CASA, which is to follow the US procedures!

But what if CASA and the FAA have differing regulations? We do have different requirements for things like fatigue management. Pilots who get a medical clearance here might not get one from the FAA. These 'risks' are pretty much just accepted by the regulators as being extremely unlikely to bring down a plane in their territory given the handful of flights a week they will be making. In extreme circumstances the FAA could place some sort of condition on the approval to further mitigate the risk of differing regulations.


Could I issue clearances at a private airstrip without being a controller? Hypothetically, if I owned a private airstrip on my property, with all the necessary permissions to do so, and I only want certain aircraft landing there, would I be allowed to issue takeoff and landing clearances even though I am not an air traffic controller?

NO!

An uncontrolled field is just that - uncontrolled. No pilot will accept a clearance in uncontrolled airspace in the first place. Consider the legal consequences if two aircraft were to collide as a result of a "clearance" issued by you. Since the aircraft are in uncontrolled airspace, it is the responsibility of the pilots to make sure they do not get too close. However,  if you got on the radio and started issuing "clearances", you might trick pilots into thinking that you are in control. If something bad happens, you should not expect to just walk away from it.

Besides, what makes you think you are qualified to provide air traffic control? Becoming an air traffic controller takes years of intense training, and only the top few percent of applicants are admitted to the education in the first place. Even the fact that you have to ask this question makes it seem like you have a very poor understanding of air traffic control.

The issue of not wanting people to land on a private airstrip has nothing to do with air traffic control. Air traffic controllers do not exist to tell pilots what they can and can't do - they are there to provide a service to the pilots! As others have pointed out, this would be a matter of trespassing. Pilots are very well aware that private airfields are just that - private. No one will just randomly spot a private airfield from the air and decide to land there without having first done some research - unless in emergency situations, of course.


Why don't turboprop planes have push engines that use thrust more effectively? The Piaggo P-180 is one of the fastest private planes out there and uses the push system.

Pusher engines do not generate more thrust; they are basically the same engines, but mounted in a different configuration. As pointed out by @JanHudec in the comments, this configuration can be more efficient since in a traditional puller configuration the air displaced by the propeller washes over the wings and fuselage, thus increasing drag.

There are several considerations, such as those set out in the reference already given by Greg Hewgill in comments.

However, the main reason why propeller pushers are not as used on commercial aircraft is safety. Consider an aircraft taking off. If the pusher engines are placed, as usual, at the rear of the A/C, then the propeller tips are rather close to the ground. Even if the propeller does not actually make contact, any debris present on the runway and lifted by the A/C can conceivably end up within the propeller disk. This would be, naturally, at about the worst phase of flight to lose power.

This is perhaps less of a concern on drones and small aircraft used in GA. The pilot (and owner) may choose to forego a bit of safety to obtain a more compact aircraft and where the pilot's field of view is not interfered with by the presence of a spinner disk.

Another point that can be considered is the fact that turboprop engines are generally used in commercial aircraft that require shorter take-off and landing distances, to connect to smaller airports that handle jets with difficulty or not at all. In this case, a pusher configuration that requires higher speeds and longer runways would not be appropriate. On the other hand, in a puller configuration some of the prop-wash can be used to generate further lift through the Coandă effect and decrease take-off distance.


What advice would you give a novice pilot on controlling the rudder? I've recently picked up flying lessons for ULL (similar to LSA in N.America). I've thought I've been doing pretty well (I guess my experience with computer simulation helped considerably).

Yet more and more I seem to have trouble with my feet and controlling the rudder - my instructor(s) tell me that I just seem to be "unwilling" to move them, yet it just seems to me somehow unnatural and awkward.

Are there some tips for novice pilots on how to dive into the rudder-control, best feet stance etc? (I tried to do a web search but couldn't find anything useful.) Or is it a normal thing for beginners to struggle with this?

It's very normal for most students to struggle with the rudder initially.

One aspect that got me while learning to fly:

Unlike stick inputs is not 'applied pressure' that measures the effect of the rudder, but the actual physical displacement of the pedal. It was quite usual for me to feel the need for right rudder, increase pressure on the pedal but with very little actual pedal movement, so there was practically no effect on the a/c.

So I made a conscious effort when right rudder was needed to apply pressure enough To Move The Pedal.

In other words if you want to double the effect of the rudder you need to double the pedal displacement, not double the pressure applied.

Second thing that got me to using the rudder correctly:

Make a mental note to use rudder

when using the ailerons
when changing power settings.

Pretty soon these actions will become linked by the brain and you will do it unconsciously. Then with time you will also learn to use the correct amount.

On feet stance

I am pretty short at 1.70m so I was usually selecting the closest setting for rudder which was placing the rudders very close to my knees, and as such it was difficult to properly use them (as my body was literally resting on the pedals). I was once advised to push them further back and it has made a world of difference: adjust them so that maximum deflection requires just a little bit of hip effort and almost a straight knee. Try a couple of positions and see which one works best; your instructor can help to show you the proper adjustment, and it does make a word of difference.


Where can Cirrus Aircraft VisionJet Oleo Struts Material and Dimension Specifications be found? I am looking to get hold of Cirrus Aircraft VisionJet Oleo Struts Material and Dimension Specifications. Can anyone point me to or share where I can obtain these details. So far, I have been able to get general specifications at the following link.
https://cirrusaircraft.com/aircraft/vision-jet

Thanks.
Vedanth

You're after the landing gear oleo Source Control Drawings.  You need to contact Cirrus' tech support and request the drawings from their engineering organization via their support organization, who may or may not want to help you, or may charge for them if they do.

I expect they won't want to provide them because they'll suspect that it's for someone who wants to make a PMA (Parts Manufacturer Approval) copy. It's usually pretty tough to find source documentation like that for a product that is in current production.


How may I verify WAAS channel number on G1000? Take RNAV (GPS) Y RWY 36L and RNAV (GPS) Z RWY 36L at APC for examples,

All fixes and routes in the two approaches are similar.
The noticeable differences that I observe are minimums and WAAS CH number.

So some questions:

(1) How may I know which approach I am able to shoot? (or which WAAS channel is available?)

(2) Is the WAAS channel number automatically selected when I load the corresponding flight plan in G1000?

(3) ILS vs LPV: For an ILS approach, I may tune the localizer frequency and get both horizontal(CDI) and vertical (Glide Slope) information, without loading the flight plan. Can I get something similar with an LPV? I mean to get the LPV glide path guidance without loading any particular approach (set the WAAS CH number for instance?).

I don't know if you can check or set the WAAS channel number directly (and I couldn't find anything about it in the C172 G1000 manual) but even if you can there's really no point. When you load the approach, the G1000 gets the WAAS channel number from the database as part of the general approach definition and configures everything automatically.

I heard or read somewhere that the original concept was that pilots would 'tune' the WAAS channel in the same way that they tune an ILS frequency, but that idea was dropped because an RNAV approach is totally dependent on the database anyway: if you trust the G1000 to load all the waypoints, altitudes and other information correctly from the database then there's no reason to think it will load the wrong WAAS channel.

As for your specific questions:

(1) How may I know which approach I am able to shoot?

You read your G1000 manual, check the approach database, and review the approach plates to make sure that the approach is available and you meet all the requirements. If the approach is in the database that doesn't automatically mean that you can fly it, there can also be climb performance or altimeter setting requirements (for example) that are unrelated to the G1000.

(2) Is the WAAS channel number automatically selected when I load the corresponding flight plan in G1000?

Yes. The G1000 sets up the approach completely for you, the only input required (usually!) is to load the approach and select how you initiate it, i.e. via an IAF or radar vectors.

(3) [Can I] get the LPV glide path guidance without loading any particular approach (set the WAAS CH number for instance?)?

No, this wouldn't make any sense. The LPV glideslope is constructed virtually by the G1000 for each approach and the WAAS input just provides correction to an existing GPS position, it doesn't give you a position directly. So even if you could receive the WAAS corrections directly (and maybe you can, for all I know), the G1000 wouldn't be able to generate a glideslope without all the other approach information about the runway, elevation etc. It would be like asking, "the magnetic declination here is 4°W, what's the correct magnetic heading to fly from A to B?" Unless you know the uncorrected heading, the correction by itself isn't useful.


Can you identify this model of a twin-engine propeller aircraft? Can anyone tell me what this is please?

It resembles I.AE. 24 and I.AE. 30, but not close enough for a match.

I believe this is a model of the De Havilland Mosquito.

Image source: ThoughtCo.


Why not always take off with 10 degree flaps in a Cessna 172? 10 degree flaps increase our lift, reduce stall speed, reduce ground roll.
Seems like all advantages with no disadvantages.
So why does the Cessna 172 POH say normal take off is 0-10 degree flaps?
Why not always use 10 degree?

Flaps out will reduce the ground run, but you're forgetting that they also increase drag. This is why you don't climb all the way to cruise altitude with flap extended. A 172 will climb better without flaps.
With a take-off, you have to consider both the ground run and initial climb. After all, the take-off distance required is defined as the distance required to climb to screen height (50ft in Australia, sorry if the US is different). The aircraft also has to meet a legal minimum climb gradient to that height.
Without looking at the data, it is possible that in certain conditions, taking off with flaps 10 will get you off the ground quicker, but will actually take longer to reach 50ft compared to a takeoff with no flaps. In any case, retracting flaps in a busy time after takeoff is a potential hazard, and in a training aircraft like the 172 simple procedures are best.


What's the wisdom of attaching an aircraft lift strut to a wing spar utilizing a single eye bolt vs the common two plate or strap method? in the enclosed picture are three examples of types I'm speaking of.  In the top picture, the lift struts are attached via a single eye bolt.  The eye bolt is obviously vertical through the wingspar
I looked at the rudimentary engineering drawing elsewhere on this site showing the forces acting on the wing spar, and get that the wingspar is tending to make an S curve.  Let's assume that the wing spar in question has an internal sleeve doubler to effectively increase wall thickness to resist compression and prevent the collapse of the tube.
In the middle drawing, the most common method method. Two straps fore and aft, attached via a bolt horizontally though the spar. I have an elementary understanding that this second, commonplace method puts drilled holes through what I believe is the "neutral axis" of the spar.
finally, the bottom illustration of the "texas parasol" type of fitting.  It shares a commonality with the eye bolt in that there are holes drilled through the compression and tension axis vertically through the spar and attaching a u shaped bracket to the bottom of the spar into which the lift strut is through bolted.  Two holes, albeit smaller in diameter than the single but larger hole of the eye bolt.

Vertical bolt = less optimal.  The reason is the tube walls in the 12:00 and 6:00 locations (top and bottom areas) are effectively the primary tension and compression members of the tube, and the 9 - 3:00 areas are the shear zones.

In other words, if the tube was an I beam, you'd be putting holes right in the cap strip flange of the I beam where the tension and compression loads are highest.  You're like the plumber who drills holes in floor joists too close to the edge and severely weakens the joists.

The horizontal bolt is much better because the holes are in the neutral axis of the tube, the middle of the shear zone, and the bolt/nut serve to prevent the tube from ovalizing (squashing flat) under bending load. So the horizontal bolt actually strengthens the tube overall, because the hole has little effect on the upper surface's compression strength and the lower surface's tensile strength, and the bolt and nut support braces the tube against flattening (by preventing the sides from spreading), so the upper and lower surfaces can get closer to their actual stress limit potential.

So the middle picture, pound for pound structure wise, is the best method. However you can do it the other way if you size the material to compensate for the strength lost to the holes at the top and bottom, so either way will work.

And in fact, on something like an ultralight with wire braced wings and a spar supported at multiple points along the span, a designer may find a vertical eye bolt like the top sketch to be the most elegant solution in the greater scheme of things, and it's worth while to do it that way and compensate as required with heavier meat adjacent to the holes than would be needed with a horizontal hole.

But if you tested the single vertical bolt configuration against the single horizontal bolt configuration, with identical hole sizes and material thicknesses, the vertical one would almost certainly fail first.


Do I have to follow airways to meet the IFR cross country 250 NM flight requirement in 61.65? I understand that there is cross-country flight of "a distance of at least 250 nm along airways or ATC-directed routing" requirement for the IFR rating, but I'm not sure if understand what the second part of that sentence means.

Do I have to follow Victor airways? Will obtaining flight following from ATC be sufficient?

14 CFR 61.65(d)(2) says:

  (ii) Instrument flight training on cross country flight procedures,
  including one cross country flight in an airplane with an authorized
  instructor, that is performed under instrument flight rules, when a
  flight plan has been filed with an air traffic control facility, and
  that involves—

  (A) A flight of 250 nautical miles along airways or by directed
  routing from an air traffic control facility;

  (B) An instrument approach at each airport; and

  (C) Three different kinds of approaches with the use of navigation
  systems.

The wording is saying that you must follow airways or a route given by ATC. But since the flight must be under IFR, you'll get a route from ATC in your clearance anyway so I don't know why the FAA has the airways reference in there.

(As a complete guess it may be left over from a time when there was less radar coverage and the FAA wanted to make sure that instructors weren't taking any shortcuts.)

I don't know what flight following has to do with this because that's VFR, and the flight must be IFR.


How are change-overs between regional air traffic patterns communicated? The airport near me that has two major landing/takeoff patterns part of a large regional air traffic control plan involving other major international airports (SFO/OAK/SJC)

The duplicate-cited question addresses the general question of change-over. I am in need of public service information on when this change happens.  I have edited this question to remove the general curiosity.

Generally  I would like to know how  the changes between two regional plans  is communicated or published to the public or if it is available on a public service. Specifically, the East-Plan/West-Plan change in the SFO/OAK/SJC area (CA, USA)

90% of the time the take off direction is in direction that does not impact me.

When the prevailing winds change the takeoff pattern is directly overhead. This has an impact on alarms and equipment. In order to automate the shutdown of certain equipment I would like to monitor regional ATC information.  I have considered simply monitoring flight patterns, prevailing winds, and weather conditions. A definitive source is preferred because it takes some time to reconfigure the equipment.  Does such a ATC or FAA source exist for the general public?

There won't be any publicly available source for what you're looking for. Any information that you could get access to (as mentioned below) won't be reliable enough to predict when the runway changes will occur. The initial coordination always happen over secured phone lines between the controllers at the radar approach/center facilities and towers. There is no way you can hear this.

Each airports ATIS (Automated Terminal Information Service) (https://en.wikipedia.org/wiki/Automatic_terminal_information_service) will be reporting what the runway(s) in use are - but this won't actually change until the runway change becomes active, maybe 5 minutes before. I suppose it would be possible to monitor this, probably via LiveATC (or setting up your own equivalent). You could somehow monitor or export this information and listen for key words to trigger your whatever-you're-using-to-shut-off-your-"sensitive equpiment" - but I think you'd get a lot of false positives. On the same note, you could also hear controllers making their initial calls to pilots advising them of the impending runway change (probably on arrival feeder sectors of ATC or the center descent clearances).

I don't think either of these methods are reliable enough for what you're looking to do. You may consider moving your "sensitive equipment" to somewhere not near an airport.


Does it really take 9000 feet to recover from a spin in a P-51 Mustang? I was a bit surprised to hear from this P-51 pilot (9:33 into the video) that the Mustang requires 9000 feet to recover from a spin.  This seems high to me.  The Mustang POH does not confirm this, but given the indicated recovery procedure, it seems possible:

  b. RECOVERY. -- Recovery procedure is the same in both a left and right spin. Upon application of opposite rudder, the nose drops slightly and the spin speeds up rapidly for 1 1/4 turns, after which the spin stops. Rudder force is light at first, becomes very heavy for a period of about one second at the first half turn after starting recovery, then drops to zero as the spin stops. Recovery is effected in the normal manner, that is, by applying full opposite rudder followed by movement of the stick to neutral.

I've researched altitude loss in more modern GA single engine planes, and <= 1K per turn seems common.  See this discussion about altitude loss in a 77 Mooney M20J.

I've also researched altitude loss in the Mustang a bit further, but have been unable to find confirmation of this.  Now I don't imagine we have a plethora of Mustang pilots actively participating in this forum, so I'll temper my question to be, does 9000 feet seem reasonable?  If so, why?

Note: It is not my intention to call into question what the pilot in the video is saying.  He does admit he hasn't actually spun the mustang, implying he either read or heard this elsewhere.

Update, July 21st 2017

I came across this video, a VERY good 1944 briefing likely filmed for pilots who are being introduced to the P-51 (Have to admit, I never knew Lee J. Cobb was balding!) .  The pilot demonstrates both left and right spins starting at 20:58.  It is mentioned that it takes 3 turns to recover, but unfortunately, it is never mentioned how much altitude is lost.  However, I suppose it is possible that it could be estimated  by looking at the plane against the background by someone far better at this type of math than me.

I've also reached out to the Flight Chops guy to see if he or the pilot want to add their two cents to the discussion.

9000 feet is not likely if the pilot applied recovery techniques in a timely manner.

US Army Air Force spin tests found here resulted in an average of 3000-6000 ft alt loss. There are several memos on it all resulting in similar figures.

This one dated 6/26/1943 shows 5500 feet for P-51A

This one from 4/30/1944 shows 3000-6500 ft for P-51B

The longest drop noted was on this memo from 7/10/1943 on the P-51A which indicated a single occurrence where the pilot modified his recovery technique resulting in a drop of 7500 ft.


What is the expected reaction of a civil airliner pilot upon an invalid request from a fighter jet? After asking a question about the recent diversion/pirating of the Ryanair flight in Belarus (that got closed, but has a nice answer), I got to wonder about how the pilot should have had behaved in that case (fictitious situation of a flight over Lithuania, Belarusian jets requesting it to fly back to Belarus).
What are the rules for a pilot of a civil plane when they are requested by a military plane (a fighter jet) to follow them, when the plane is from another country than the airspace?
I can understand that within an organization such as NATO, a Polish plane could fly over Germany to intercept a Singaporean plane (because of NATO agreements).
From the perspective of a civil airplane pilot - does it matter? In other words my questions are:

is the pilot expected to make a decision about whether to follow a military plane at all? (= if they see a plane that requests them to do something, should they follow the requests no matter what?)
is there any consideration of the airspace? (= should the pilot take into account the place they are above?)

I would like to highlight that I am interested in the rules on how a pilot must behave (and not acts of bravery or something like that).

What do rules have to do with your hypothetical situation?  At that point the question is what a completely unarmed person, who is immediately responsible for the lives of other people (assuming there are passengers), should do when another person who clearly doesn't obey laws and has a deadly weapon demands something, and nobody else has the power to interfere.
It seems to me that the choices available to the civil pilot are to comply, to refuse, or to try some sort of trick.  A rational person at that moment would be completely concentrated on survival for the aviator and passengers, and wouldn't be concerned about rules.


Is a slip an intentional consequence of a cross-control? In flight training, you're always told not to cross-control, (for example, rolling right aileron, and stepping on the left rudder), but it seems to me that is exactly what a slip is doing.

Is it that a slip is intentional, and a cross-controlled situation is typically unintentional?

You are right: A slip is a cross-controlled (and uncoordinated) situation. It's exactly what your instructor was teaching you to avoid during your early lessons.

As far as nomenclature goes: all slips are cross-controlled maneuvers, but not all cross-controlled maneuvers are slips: On climb-out in most piston singles you will be stomping on the right rudder to offset the plane's left-turning tendencies, and you will probably notice that you're rolling in a tiny bit of left aileron (which offsets the banking tendency introduced by the rudder) - your controls may be very slightly crossed, but the result is coordinated flight (a centered ball).

The real difference here between an "unintentionally cross-controlled situation" and an "intentional slip" is the intentional bit: When you are knowingly slipping the aircraft - for example to bleed off altitude on a high final without increasing your airspeed - you're aware that you're flying in an uncoordinated and aerodynamically unstable condition. You're aware of the risks, and are hopefully monitoring the aircraft carefully to avoid a stall/spin.

For a little more insight, faaflighttest.us has a reprint/copy of an Aviation Safety article from April 2006 which is worth a read, and possibly an hour in the air practicing some of what they discuss with your instructor so you can get the "feel".


What is the ALT INTV on the 737's autopilot? So, I was watching a quick tutorial on the FMC on YouTube. The FMC somehow had a 5000 ft restriction, and the guy got clearance to go higher up, and he set his altitude on the AP panel, and he pressed the ALT INTV button.

From the FCOMv2 4.10.10 (emphasis mine):

  Altitude Intervention (ALT INTV) Switch

  [Option - With speed and altitude intervention]

  Allows manual deletion of next FMC altitude constraint via altitude SEL and ALT
  INTV switch.

  Push – (during VNAV climb)

  lowest FMC altitude constraint below selected MCP altitude is deleted
  if airplane is currently at an FMC altitude constraint, deletion allows airplane to resume climb. MCP altitude must be set above current altitude
  for each press of switch, one deletion occurs
  if MCP altitude is set above current FMC altitude, FMC cruise altitude
  resets to MCP altitude. FMC cruise altitude cannot be decreased using
  ALT INTV switch.

  Push – (during VNAV cruise)

  if MCP altitude is set above current FMC cruise altitude, FMC resets
  cruise altitude to MCP altitude and initiates a cruise climb
  if MCP altitude is set below current FMC cruise altitude, an early descent
  is initiated. Lower FMC cruise altitude cannot be entered using ALT
  INTV switch.

  Push – (during VNAV descent)

  the highest FMC altitude constraint above MCP altitude is deleted
  if airplane is currently at an FMC altitude constraint, deletion allows
  airplane to continue descent. MCP altitude must be set below current
  altitude

  [Option - FMC U10.6 and above]

  if all FMC altitude constraints are deleted during VNAV path descent, an
  automatic transition to a VNAV speed descent is made.


Why do pilots do walkaround inspections for regularly scheduled commercial flights instead of aircraft mechanics? If the airline has personnel to maintain the aircraft, wouldn't it be more cost effective to have them inspect the aircraft before flight rather than have the captain or first officer do it?
Is it because whoever will fly the aircraft will probably do a better job of inspecting it because they are putting their own lives at risk?

Because it's the Captain's plane, for all intents and purposes. This is exactly the same for many other industries - in particularly shipping (as in boats) and haulage (as in trucks).
Similar to planes, ships and boats have captains and they are all fundamentally and legally responsible for everything that happens on that mission. And, likewise, a truck driver is expected to maintain responsibility for their truck - indeed, over here in the UK this is a legal requirement and truck drivers have to do a mandatory walk-around check.
It's also the same for car drivers - you, as a driver, are fundamentally responsible for your car and its safety.
Focussing on aircraft, the pilots probably have the single most holistic view of the aircraft, its mission and the requirements. In addition, the pilot is always going to be there - whether that's Heathrow at 2pm on a Tuesday, or a deserted dirt strip in the outback at 10pm.
The better question might be - what good reason would there be to skip a walk around in one of the most safety-critical industries? At best, for some airports in some circumstances, you can argue somebody else might be able to conduct the walkaround - but it's not guaranteed and it introduces another potential point of failure or miscommunication.


What instruments are used to indicate aircraft attitude in acrobatic airplanes? As aerobatic airplanes don’t use gyroscopic instruments such as attitude indicators, what instruments are used to indicate the aircraft’s attitude in flight?

The basics:  Acro airplanes don’t have attitude indicators because they don’t need them.  The airplanes are certified at Day/Night VFR flight only and gyroscopic instruments are not required equipment here, not to mention can be precessed and damaged by aerobatic flight.

The only attitude instruments needed here is the horizon itself and the pilot’s Mk I eyeballs to see it.

Sometimes pilots make use of aerobatic sights mounted on the wingtips; these look something like eight spoke cowboy spurs or a 45° right triangle frame and are used to fly certain reference lines during aerobatic flight.

Some acro aircraft do make use of glass cockpits and solid state Attitiude, Heading, and Reference Systems (AHARS) as a safety backup on cross country flights, but they are not used during aerobatic routines.


Did CNN correctly state that AirAsia flight stalled and crashed? CNN reported that the cause the crash of AirAsia Flight 8501 is:

  ... it stalled and fell out of the sky ...

The reality is that when an airplane stalls it does not fall out of the sky. Why did CNN report such a statement?

The aircraft was at 36,000 feet when it stalled. According to the flight recorder, it was descending at 6000 feet per minute. Stalling an airplane at 36,000 feet means there is plenty of time to recover from any stall, unless the airplane was loaded tail heavy. But that was not reported.

Am I missing something here?

An aerodynamic stall is exactly that: the wing is stalled and is not generating enough lift to keep the aircraft in the sky. The aircraft is falling out of the sky. Whether the stall can be recovered from, and therefore the aircraft can stop falling out of the sky, is an entirely different question.
Some stalls can be recovered from, others cannot... particularly if whatever caused the stall is preventing recovery.

An aerodynamic surface which is stalled is no longer generating significant lift. Most specifically it's not generating enough lift to support the aircraft
An object which is not generating sufficient lift to keep it airborne, and is being pulled towards the earth by gravity, is falling

So yes, CNN is correct - the plane fell out of the sky while stalled. Generally a plane which is at 36,000 ft and is not falling out of the sky, doesn't hit the ground.
As Falstro mentioned in his comment, AF447 didn't realise it was in a stall at all, so therefore couldn't remove it. We don't really have enough information about the AirAsia flight to be sure what happened


Is fuel moved around during flight on a passenger or cargo plane? If so why? Is fuel moved around during flight on a passenger or cargo plane? If so why? Is balance an issue?

Maybe

This is dependent on the air frame and varies from plane to plane and not all planes have capability of moving fuel although most large planes do. The Concorde moved fuel all over the place from its 13 tanks to cool the nose cone as well as trim the aircraft. It was perhaps one of the most complex implementations of such a system and kept the flight engineer quite busy.

(source)

Here is a layout of how it was used to control trim.

(source)

For any of this to be possible the aircraft must be equipped with cross-feed abilities. On larger planes this is fairly common, in case of a single side leak the cross feed valve is usually kept shut but since engines can have slight variances in fuel burn the pilots may need to cross feed every so often to balance the plane out. There is a nice overview on 737 fuel systems here.

(source)

In small, often single engine aircraft fuel management is generally left up to the pilot. There are often multiple tanks which can be individually selected and must be rotated in flight every so often (30 min usually). Since some planes are prevented from drawing from "both" tanks, the switch has a lot to do with not running a tank dry in flight.

This article overviews weight and balance fairly well. Often times quantity of fuel is more important than location. Most modern airliners store the fuel fairly close to the CG (in the wings or belly for that matter). The Concorde's unique delta wing design led to a fairly different use case than your run of the mill jet.

Some of the balance issue is solved within the tank using baffles which keep the fuel from sloshing around too much but allow it to flow freely around a fairly large tank when need be.

You can find the full text of the FAA's book on fuel systems here.

Here is a neat video of how to actually cross feed fuel.


How far back from the final approach fix can you intercept the glideslope? I was looking for the point that you engage your auto pilot approach glide slope before the final approach fix in this question. How far back can you go?

From the navaid limitations section of the FAA Order 7110.65 (below), it's 10 miles from the transmitter. For the minimum altitude, it's shown on some charts as a lightning bolt.


Can repeated call-signs be present in one day? I am working with a big ADS-B traffic sample of one day Europe, and identified repeated call signs. Examples include:

Flight that ends in an airport and repeated call sign starts from there.
Two flights with the same call sign, ADEP and ADES.
Four Different ADEP and ADES.

I thought in one day it was not possible to have repeated call signs.
Is this possible? Is my data wrong?

It is no problem to have the same call sign on the same day. As long as the same call sign is not uses at the same time there is no problem.

For VFR flights, the same call sign can even be used at the same time as long as it is not in the same airspace.

Many of the ADS-B duplicated call signs on a single are aircraft registrations coded in the transponder's aircraft ID field, typically from General Aviation flights


How to calculate the wind variation? Given the:

True Heading = 070 degrees

True Track   = 061 degrees

True Air Speed = 120 knots

Ground Speed = 118 knots

what is the wind variation?

these are the steps I am taking to calculate the wind variation:

1 - put the true heading on top - the true heading is 070 degrees

2 - put the true air speed inside the little circle - the true air speed is 120 knots

3 - mark the drift ( true heading - true track) = (070 - 061) = 9 degrees on that line

4 - draw down to the ground speed (118 knots)

5 - bring the little blue circle back to zero

6 - rotate the disk so that the cross is on the central line

there I can see that the wind comes from 151 degrees at 19 knots.

Questions:

will this always be correct?

Could I have calculated it through a formula (without using the computer)?

Sure it can.  It's just vector math.

$$\vec{A} + \vec{B} = \vec{C}$$

If $\vec{C}$ is your ground speed vector and $\vec{A}$ is your airspeed vector (magnetic heading with true airspeed as a magnitude, then $\vec{B}$, the wind vector, can be solved for by

$$\vec{B} = \vec{C}- \vec{A}$$

Electronic flight computers and E6B apps for tablet computers/smartphones can do the same thing.  But it's nice to have some basic skills with a whiz wheel.


Could a hybrid electric steam plane be more efficient at altitude than at sea-level, and how to optimise it to frigid air? In the thirties a steam powered plane was built.
video

Could a hybrid electric steam plane be more efficient at altitude than at sea-level, and how could such a steam engine be optimised to benefit from frigid air at altitude?

Perhaps there are two advantages to going hybrid.

The steam engine can be down sized to cruise power levels.
The radiator is being cooled by frigid stratospheric air < -40 deg so can be smaller.

This is a parallel hybrid, the electric motor drives the propeller until the plane is at altitude. Once at altitude the electric motor is disengaged and the small steam engine starts up and engages with the propeller.

[edit]

There is a replica of the Besler engine at the Smithsonian. It has more specs than the video. It had a condenser

Steam Car Developments
and Steam Aviation, VOL. III. JUNE, 1934 NO. 28., The Besler Steam-Driven Aeroplane

'Under the fuselage nose is the condenser, which is simply a section of an ordinary petrol car radiator, and this is said to be sufficient to recover more than ninety per cent. of the water from the exhaust steam.'

'The tests have shown that ten gallons of water is sufficient for a flight of 400 miles.'

Forget the electric stage - when using steam, you will most likely already have mechanical energy and when ducting that steam through a turbine, even rotational energy to turn your propellers. What advantage do you expect from converting that rotational to electrical and directly again to rotational energy?

That design could be simplified even more: Instead of heating water, the fuel could heat compressed air and let that run through a turbine. That is how any modern jet engine works.

In order to keep mass down, the steam would need to be condensed in a cooling circuit. While the wing surface could be used for this, the required piping would add a substantial weight penalty. In an open circuit where the relaxed steam is simply dumped overboard (like on the Besler biplane or most steam engines), range would be rather limited.

There was to my knowledge a single attempt at building a steam-powered airplane with steam condensation. This was a version of the Messerschmitt 264 bomber which was supposed to run on a mixture of coal powder and heavy oil instead of gasoline. It was never completed.


Transonic Airfoil with high critical mach number does anyone know, how I can find a transonic airfoil (high subsonic, Ma=0.88) with a high critical mach number?

I know that if I know c,0,min = minimal pressure coefficient of the airfoil, then I can calculate the critical mach number.

But when I use Xfoil for plotting the pressure distribution, I only get a nice picture, but I can not write out the data for the pressure distribution. otherwise I could determine the critical mach number.

Maybe someone has some hints for me?

Thank you

Lucas

First I have to say that XFOIL is not the right tool for such a high Mach number. Professor Drela has written ISES to address the shortcomings of XFOIL at transsonic speed.

Next, the critical Mach number is well defined as $$c_{p_{crit}} = \frac{2}{\gamma\cdot Ma_{\infty}^2}\cdot\left(\left(\frac{2}{\gamma+1} + \frac{\gamma-1}{\gamma+1}\cdot Ma_{\infty}^2\right)^{\frac{\gamma}{\gamma-1}}-1\right)$$
which can be simplified for air as $$c_{p_{crit}} \approx \frac{1}{0.7\cdot Ma_{\infty}^2}\cdot\left(\left(\frac{5+Ma_{\infty}^2}{6}\right)^{3.5}-1\right)$$

$\gamma$ is the ratio of specific heats and is 1.405 for air.

For $Ma_{\infty}$ = 0.88 this is -0.23 which is too little to even accommodate a moderately thick airfoil without supersonic flow. Therefore, your wing needs sweep to function well. Even then, I recommend a supercritical airfoil which will have supersonic areas at this speed but without a big drag penalty. Take your pick.