Aeronautical Insanity: switching to secondary tolerances

The Something Awful Forums > Discussion > Automotive Insanity > Aeronautical Insanity: switching to secondary tolerances

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Tsuru: May 12, 2008

CommieGIR posted:

More aircraft cupholder goodness:

Cupholder by Radar display at Nav's station:

Click here for the full 2048x1536 image.

Cupholder by Co-Pilot's right knee

Click here for the full 2048x1536 image.

There was one by the Pilot's left knee

So which type of Herc is this that it needs a radar display?

# ¿ Oct 23, 2010 16:35

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# ¿ May 17, 2024 22:07

Tsuru: May 12, 2008

MrChips posted:

I did some poking around regarding the elevator trim tabs on the P-51, and I found this:

It seems as though the elevator trim in a stock P-51 isn't great at high speed and power settings. The Reno racers are likely to have been modified, but no modifications can save you if they depart the aircraft. If what I read is true, there was likely no recovery from this...the control force needed would have been hundreds of pounds.

If I'm reading this correctly, the worst thing about this is that according to this you need your elevator trim fully down at full power... so imagine if you will, you are flying at very high speed and high power setting, with your elevator trim fully down as well as pushing on the stick to keep the nose down... and then your trim tab lets go.

On another forum I read about another incident with a P-51 called Voodoo Chile, which was flown by Bob Hannah. He went into a sudden +10G climb when his trim tab failed at high speed, with him blacking out instantly. He regained consciousness at 9000 feet.

With this information I think it's hard to see how the pilot's age could have been even a minor factor. RIP.

Tsuru fucked around with this message at 19:10 on Sep 17, 2011

# ¿ Sep 17, 2011 19:04

Tsuru: May 12, 2008

MrChips posted:

...causing the elevator control forces to increase almost instantly. Since no one short of He-Man would be able to hold several hundred pounds of force, the elevator would center itself in the airflow, causing an uncontrollable pitch-up of the aircraft.

Whether or not this proves to be a probable cause in this accident remains to be seen, it is certainly within the realm of possibility.

On a sidenote, has no-one considered that a fully trimmable stabilizer or a fully moving tailplane would be an asset for an air-racer? Since so many other things have been so heavily modified on these birds, a redesigned longitudinal control system and tailplane would probably make these birds even faster (and maybe safer?). As far as I can see nothing like this has been done to these racers. Even though many of them have been given smaller ailerons and tip fences, the tail looks like it hasn't been touched.

Bondematt posted:

Isn't this impossible due to the decreasing efficiency of prop engines as they reach the speed of sound or does it just make it a bitch?

This is probably true. You could conceivably do this if you had an engine that has enough power in a structure that could deal with all the vibration and compressibility issues, but acc to wikipedia even the thunderscreech with its nearly 6000hp could only do mach 0.7. So in theory yes, but practically no.

Tsuru fucked around with this message at 21:04 on Sep 17, 2011

# ¿ Sep 17, 2011 21:00

Tsuru: May 12, 2008

Is this fan / final stage turbine wheel connected to the front of the compressor in any way or is just bolted onto the back of a J79?

# ¿ Sep 21, 2011 22:18

Tsuru: May 12, 2008

MrChips posted:

Both the CF700 and the CJ805-23 have the fan mounted on a single stage, low-pressure free turbine. There is no physical connection between the core engine and the fan.

After my previous post, I was wondering to myself why GE went about creating both the CF700 and CJ805 as they did. Just now, it dawned on my what their rationale was; it allowed them to convert their existing family of turbojets into turbofans with a minimum of engineering work. At the time, GE's turbojet engines tended to be single-shaft designs, unlike Rolls-Royce and Pratt & Whitney's engines. While they are simple, single-shaft engines are impractical to convert into turbofan engines; the single shaft of their engines turned too quickly to run a fan efficiently, and the forces acting on the bearings would likely have been too high. GE realised instead that they could slap a free spinning power turbine behind one of their existing cores and drive a set of fan blades attached to the outside of the power turbine in a "double deck" configuration, like you see in the cutaway diagram I posted. It isn't an ideal solution, but it allowed GE to create a range of turbofan engines at relatively low cost to themselves.

I should also clarify that the CJ805 is GE's designation of the military J79 engine; the CJ805-23 variant is the wacky, aft fan turbofan we're discussing here.

That is really interesting, thank you

There were of course going to be problems with this, I mean, the weight of the cowling would have been excessively high compared to a JT3 or a Conway, and there are going to be fatigue issues with a turbine wheel that has the inside spinning in a high temperature zone and the outside spinning in a cold zone, with all of the energy transfer contained within this same wheel and the inner/outer blades attached at different angles. It's a very clever idea if you have a massive stockpile of military J79s laying around, but not in a lot of other ways I can think of.

The commonality between military and civilian engines is an interesting one, I also remember reading somewhere that the core of the CFM56 used on the 737, A320, A340 and re-engined 707s/DC-8s is the same basic one as used in some US-built fighters and the B-1B.

# ¿ Sep 22, 2011 06:25

Tsuru: May 12, 2008

BonzoESC posted:

Just flew a simulated C-130 around for an hour. Look forward to lots of my dumb opinions about military power and air safety based on this experience!

Anything that's on your mind regarding the sim? I happen to be a sim engineer.

Incidentally one of our machines is also of a C-130H.

# ¿ Sep 26, 2011 07:50

Tsuru: May 12, 2008

BonzoESC posted:

It would have been a lot better if one of the projectors wasn't offline, but it was boss as hell.

I hope the volume was all the way up?

Hehe

# ¿ Sep 26, 2011 16:07

Tsuru: May 12, 2008

I thought I'd just leave this here:

https://www.youtube.com/watch?v=jPWtIhIFL14

# ¿ Oct 21, 2011 10:56

Tsuru: May 12, 2008

Epic Fail Guy posted:

Douglas had so many amazing aircraft. The A-4, Dauntless, DC-3, DC-8, etc.

Too bad the DC-10 and MD-11 didn't follow the tradition. Maybe they'd still be around.

For all its initial woes the DC-10 turned out to be a great aircraft... it was the MD-11 that did not do justice to Douglas' great history (DC-3/C-47, DC-4/-6/-7, DC-8, DC-9/MD-80).
The MD-11 is a dog, with a cruise fuel burn that was too high when it was new, and too many patches and corners cut trying to bring the performance up to par. The wing twist/aileron droop, the no.2 engine intake, the shrunk horizontal stabilizers/LSAS... It was never a big seller to begin with, and most of the airlines that did buy it to fly passengers were not really happy with its performance. The 777 was the final nail in its coffin. I have been told some of the reasons KLM keeps on stubbornly flying them on the mainline is because they got a killer deal on them and are cheap for them to fly due to the low cost of ownership, and the takeoff performance makes it really suitable for KLM's many Caribbean and South-American destinations. The capability for lifting bigger loads off of hot-and-high fields and relatively austere, short runways trumps its fuel burn at altitude.
For example, despite all the recent developments on the 777, the MD-11 is still king in Quito: Due to its situation at high altitude in a valley in the Andes, a 777 or 747 would be too performance-limited in case of an engine failure. The 777 because you simply lose 50% of your thrust, and the 747 because it's relatively low thurst-to-weight ratio puts it closer to the line in terms of minimum climb gradients, simply due to it having four engines (no ETOPS requirement, so no big thrust surplus). This is also the reason the MD-11 was never really that good at carrying passengers, but is still very popular as a cargo plane.

It's a big shame though... the MD-11 had great potential and was really out there in terms of on-board-systems automation, but it never got the better of its basic economic shortfalls. I had the opportunity to fly a couple of hours on an MD-11 sim and have access to a military DC-10 sim these days, and I have to say it's one of my favourites.

# ¿ Oct 25, 2011 14:47

Tsuru: May 12, 2008

Fayez Butts posted:

So basically the Queen Elizabeth 2 is like taking a Lamborghini across the pacific. Hmm. What about, say A380s or 747s?

I have heard a 747-400 is analogous to a Ford Fiesta on a seatmile basis.

# ¿ Oct 30, 2011 06:05

Tsuru: May 12, 2008

LOT 767 makes gear-up landing in Warsaw:

https://www.youtube.com/watch?v=d-N1L82VVoM

# ¿ Nov 1, 2011 16:44

Tsuru: May 12, 2008

Slo-Tek posted:

I just noticed that is a trijet. Very cool.

There were actually plans afoot for a 3 engine A-5 Vigilante.

Would have been about as close to a Battlestar Galactica Viper as you could get with early 60's technology.

I don't care that the Vig was a terrible aircraft, it was about the zoomiest looking thing that ever took to the skies.

What was it about the Vigilante that was so terrible? I always thought a supersonic nuclear bomber that could be launched from a carrier was a pretty loving cool thing to have back then.

# ¿ Nov 4, 2011 15:47

Tsuru: May 12, 2008

LOO posted:

Engine test-bed

Wasn't there at some point the idea to replace the BUFF's 8 engines with 4 bigger turbofans?

# ¿ Nov 7, 2011 11:47

Tsuru: May 12, 2008

HeyEng posted:

I just like Boeing design philosophies better. Cable and pulley with mechanical linkage is a lot more comforting to me than fly-by-wire. Not that it's a bad or poorly engineered system it's just that I feel more comfortable with mechanically-driven controls. Also, Boeing jet's look way better. Except the 757. That's just a gangly fucker.

The only difference between a 777 and an A330 with regards to the flight controls is the fact that Boeing put in an old fashioned arrangement with fully artificial feedback like a simulator. So no mechanical link for Boeing anymore either.

However, Boeing's control laws leave more up to the pilot, and are simpler and less restrictive. You can stall and barrel roll a 777, for instance.

# ¿ Dec 4, 2011 10:44

Tsuru: May 12, 2008

HeyEng posted:

Yea, forgot about the 777. Also didnt know about the FBW softened restrictions.

Airbus and Boeing really aren't that different. It's also not even like Boeing is late to the game: Airbus' first full FBW plane (the A320) came out in 1988, and Boeing's first full FBW plane (the 777) in 1994. Even before that, Boeing and Airbus alike implemented alpha protection functions to the autothrottle systems of their planes.

# ¿ Dec 4, 2011 11:19

Tsuru: May 12, 2008

Epic Fail Guy posted:

And i'm betting that Soviet radio navigation wasn't exactly up to western standards either. Probably lots of dead reckoning and NDB approaches into lovely conditions and tiny airstrips.

The dual-NDB approaches that were typically used in this part of the world are actually surprisingly accurate, as well as dirt cheap to implement. But as everywhere else it's when the minima are exceeded when aircraft start hitting terrain. Russian airlines kept employing navigators long after the West replaced them with flight management computers, and their work was typically top-notch. Airline crews typically held university degrees, as a matter of fact the only time I have ever heard an airline captain holding a PhD was an IL-62 captain from Interflug, the airline of the GDR.

Maintenance practices however, were not-so. Poland's most infamous air disaster was caused by fitting half the required amount of ball bearings to an engine turbine bearing due to a spares shortage. When the aircraft carried out a missed approach after completing a flight from New York the no.2 engine of the IL-62 exploded and brought down the aircraft.

# ¿ Dec 7, 2011 00:20

Tsuru: May 12, 2008

It looks pretty real to me... I see no reason at all why it would be a fake. Its construction is too high-quality to be made from something as crude as expanding builder's foam, and it even has the same kind of drag rudders and other details present on other drones that I've seen.

Stealth is not all it's made out to be, and hopefully this will finally convince my country's MoD of just that.

# ¿ Dec 8, 2011 21:13

Tsuru: May 12, 2008

grover posted:

Perhaps this still from the Iranian press release will convince you:

If it landed, why set it on a box? Where is the landing gear?
If it crashed gear-up, where is the damage?
Not to mention this model is about 1/3 the size of the Polecat. poo poo, it's not even as large as a predator. Lockheed does a better job of taping seams, too.

Convince me of what, exactly? That it does not matter what size or colour it is? The thing with UAV designs is that they scale really really well to suit a particular task, because there is no fleshy bit in the front of a given size. This moves your design starting point to the designed range/fuel capacity and the amount of payload that it has to carry. Given that this particular example was flown from Afghanistan to Iran and not from a base in the USA like a Global Hawk or a Polecat actually convinces me that the size of this thing looks pretty spot-on. Its comparative size to the taxiway lights in the other pictures also confirms that the size matches.

As for the seams and the drapes, it simply makes it look like the Iranians propped up a damaged aircraft as best they could to convince people who are not familiar with aircraft that they captured a fully intact UAV, but it looks to me they are trying to hide the fact that this plane will never fly again, and that they failed to preserve its most valuable component, the sensor suite.

Tsuru fucked around with this message at 05:51 on Dec 9, 2011

# ¿ Dec 9, 2011 05:42

Tsuru: May 12, 2008

Godholio posted:

Except you're wrong.

Color does matter. Evidence!=proof. A stealth aircraft is coated with special paint. IT DOES NOT COME IN TAN. Tan would be a poor choice for aerial camouflage as well. There is no reason the USAF would go that route.

This thing is way too small to have a decent sensor suite or payload. This size would limit it to roughly the capability of a Predator/Reaper, which would be pretty ridiculous to spend the kind of time and money it would take to drop the RCS. There are smaller RCS systems that have similar sensor capabilities already in existence, this thing would be redundant. Not only that, the mockup Iran displayed isn't large enough for the engine. This alone should prove the point.

Wings don't break off along a seam like that. A wing also couldn't be held up by loving BONDO.

I don't think assumptions are proof either, but let's just wait and see. I'm sure in good time we'll know.

# ¿ Dec 9, 2011 15:48

Tsuru: May 12, 2008

Godholio posted:

I'm not really making a lot of assumptions. That thing is too small to hold the engine that powers it.

I guess the paint thing is kind of an assumption, but it's based on my experience in the Air Force. I'm pretty confident about it.

I'm familiar with the sensor suites used on USAF UAVs. That thing isn't big enough to carry anything better than what the cheap/disposable UAV already carries.

As much as I hate to point out the obvious, and as incomprehensible as this concept may be to a proud American such as yourself: bigger is not necessarily better.

# ¿ Dec 9, 2011 19:40

Tsuru: May 12, 2008

Tremblay posted:

Really dude? He's in a good position to be making comments.

Maybe he's not the only one, but perhaps others might not be so tempted to engage in internet willy-waving.

It was an attempt at humour, but let's just forget about it before more egos are harmed.

Tsuru fucked around with this message at 19:59 on Dec 9, 2011

# ¿ Dec 9, 2011 19:53

Tsuru: May 12, 2008

Bondematt posted:

If he let go of the stick the Airbus would have corrected itself. The airplane design is dynamically stable.

The airplane initially thought it was overspeeding, so the flight directors commanded a nose-up attitude, which the pilots followed. The crew pulling back on the sticks caused the horizontal stabilizer to autotrim fully up (+14deg if I recall correctly). After this point simply letting go would not have saved them, recovery would have required the crew to push the nose hard down. Don't forget the aircraft also had a very rearwards CG for slightly lower fuel burn in cruise, at 28-29%.

I'm not even sure if at any point they realized their THS was trimmed all the way up.

# ¿ Dec 10, 2011 20:45

Tsuru: May 12, 2008

Bondematt posted:

The plane knew it was in a stall, I haven't seen it say anything about overspeeding. With the pitots blocked it would still be showing last speed(immediate blockage of drain/ram) or no speed(ram blocked) until they changed altitude/unblocked the pitots, assuming they fail the same as a standard pitot.

Was the CG outside of set limits? Cause otherwise it is still dynamically stable, just less so, the point of a CG limit. Of course a full trim will negate the hell out of this.

Never heard about the autotrim being connected to stick input, that is a dumb system at best and Airbus deserves even more flak for that. You should be able to stop what you are doing, and the airplane should recover to neutral (manual, previous or a standard trim)input. Having it fully deflected once the pilots release pressure is just asking for a stall to occur.

Pulling back on the stick at full throttle is a function of relying on the (now disabled)FCS, it will not let you stall that plane unless it is in "alternative law".

Do you know what happens to your indicated airspeed when you climb in a plane with blocked pitots?

# ¿ Dec 11, 2011 07:42

Tsuru: May 12, 2008

The Locator posted:

From the transcript:

02:10:35 (Bonin) D'accord.
Okay.

Thanks to the effects of the anti-icing system, one of the pitot tubes begins to work again. The cockpit displays once again show valid speed information.

02:10:36 (Robert) Redescends!
Descend!

...

02:14:27 (Captain) 10 degr�s d'assiette...
Ten degrees of pitch...

Exactly 1.4 seconds later, the cockpit voice recorder stops

They had valid speed on the instruments for the vast majority of the time. At the time the pitot tube becomes ice-free and the speed readouts returned, they were still climbing above their cruise altitude.

Not completely: for a short period speed information was lost again during their superstall descent, which lead to perhaps the greatest source of confusion: the temporary cancellation of the (AOA-driven) stall warning because the indicated airspeed fell below 60 knots. This is part of the way the stall warning system was designed, it never considered something like this could happen and of course assumed the aircraft would never enter a stall to begin with.
You also need to appreciate the way a large airliner handles when the stabilizer is trimmed fully up, especially when the FBW is working against you by neatly ironing out any G and pitch-rate clues as to what is happening. I flew this scenario in a military sim for an aircraft of similar size and weight/CG but without the FBW: even without the C-star pitch control "helping" you, the stablity of the aircraft on the pitch axis and the remaining controllability in the roll axis very deceitfully lull you into a sense that you are in control when you're not. At the same time being inside a ITCZ-sized thunderstorm at night probably did not help them getting a picture of what was happening.

# ¿ Dec 11, 2011 18:32

Tsuru: May 12, 2008

The Ferret King posted:

I think AoA instruction should be vastly more emphasized in all phases of pilot training. I wonder if the 330 even has an AoA indicator. Most civilian aircraft don't.

Most EFIS aircraft have an FPV symbol that can be enabled on de ADI, which gives you an indication of your AOA, combined with beta+drift. The problem is that for these guys their FPA was so far off the scale that it would have resulted in a dashed symbol at the bottom of the instrument, had they tried to turn it on.

# ¿ Dec 12, 2011 09:54

Tsuru: May 12, 2008

Ola posted:

This accident has fundamentally changed how I view aviation. Much like the A330, my attitude is upset by the idea that someone in control of a perfectly serviceable transatlantic airliner can ride it into the ocean while staring at the gauges going "I don't know what's happening!"

There's an infamous mythical quote where an Airbus pilot says "what's it doing now?" often quoted by detractors to illustrate the inherent flaw of abstracting the pilot out of the loop. How can you not be swayed in that direction when reading that transcript?

You can't. The stall warning logic is definitely something where Airbus dropped the ball and it will have to be fixed, even if it just means disabling the stall warning <60knots ONLY when the aircraft is on the ground. FWIW, Airbus has been working on a system that uses inertial reference data to reconstruct an approximate airspeed figure when air data sources become unavailable since well before the accident. The problem is, you can think up the most amazing avionic doodads, but you still have to get your regulatory authorities to accept it and your customers to buy it. Another example is an FMS/IRS based takeoff performance monitor that could have saved so many lives over the years and has come in and out of the debate since the 1970s, but it still isn't here.

# ¿ Dec 12, 2011 15:37

Tsuru: May 12, 2008

Mr.Peabody posted:

Every Airbus has a GPS, and every GPS can calculate speed. Why isn't this a suitable emergency backup for verifying airspeed?

It can be, but you have to know what you're doing. The difference between the (erroneous) TAS/IAS and the aircraft speed/track derived from the IRS+GPS under all circumstances is the wind vector, which is shown on the ND. In this situation, they would have observed an enormous tailwind component, with only the ground speed as shown on the IRU readout being correct. This is roughly what Airbus wants to do when they roll out this synthetic IAS system: to bring IRU data to the speed tape when air data is unavailable or unreliable.

# ¿ Dec 12, 2011 19:33

Tsuru: May 12, 2008

MrChips posted:

The FPV symbol, in all honesty, is just a toy in many cases. Sure it reports AoA, but does it tell you if you've exceeded the critical AoA? Does it take into account flap/leading edge device settings? A proper AoA gauge, or at least a number that changes colour on the PFD, would go a long way to helping in situations like this.

Boeing has an option to enable a dedicated AOA gauge on the PFD of most of their aircraft, similar to the AOA gauges many business jets use, plus a digital readout. I'm not sure whether this information comes only from the AOA vane on either side or whether it includes inertial vector data (the FPV does), but it's the same thing.

Link

# ¿ Dec 13, 2011 12:28

Tsuru: May 12, 2008

The primary reason for this is that most airliners these days have underslung engines, and slamming the throttles to get out of the stall will result in a large nose-up moment, exacerbating the situation rather than fixing it. It is also due to the fact that, for example in AF447 and THY1951, the aircraft was trimmed all the way up upon entering the stall because of misuse of the automatics. Trying to get the nose back down on a 737NG in approach config at very low speed, trimmed fully up and with the throttles firewalled is like riding a rodeo bull.

# ¿ Dec 14, 2011 17:52

Tsuru: May 12, 2008

I've been itching to post some pics of a small hobby of mine, and when the Cat got mentioned I couldn't resist. I am an aeronautical engineer who doesn't mind getting his hands dirty, and when I don't have to go to my aviation day job I help getting our Grand Old Lady back in the air. She just turned 70, and is registered PH-PBY. She is an ex-USN PBY-5A with 2,5 verified U-boat kills, and served as a water bomber in Canada before she came to The Netherlands to be beautifully restored and painted in late-1940's RNLNAS colours.

We share a hangar, tools and spares with the DDA, an association who owns and operates two classic Dakotas painted in the colours of our largest airlines, let's get their pics out of the way first:

PH-DDZ and PH-PBA, two C-47s in vintage Martinair and KLM colours respectively-

Hangar overview, with DDZ in the foreground and PBY in the back-

Some maintenance-in-progress action pics-

These engines and propellers are true works of art. We use the PW R1830 exclusively, with the same three-blade Hamilton prop. Looking at them and hearing their growl is one thing, but once you see and understand how these magnificent machines do their work and then realise they were first designed nearly 80 years ago in the early 1930s makes it all the more amazing. Crankshaft, pistons, carburettor, intake compressor, ignition, valve train, prop drive train, propeller governor and accessories all working in perfect harmony _{while spewing out lots of oil}. :11tea:

Video of a cut R1830 (not mine)-
https://www.youtube.com/watch?v=Q2DJZx08CYg

And what exactly is it I do, you ask? Well, since I work on simulators in my regular job I was given the task of minding the instruments, avionics and electrics. There's not much of it in these kind of aircraft, of course, but it's still important and delicate work that should be done extremely well. Upshot of course that I get to do most of my work in or around the cockpit :toot:

The cylindrical thing in the first pic is a Bendix 28V voltage regulator, which is basically a stack of carbon discs to, err... make 28V out of whatever is coming out of each DC generator.

A video of our bird from when she was airworthy-
https://www.youtube.com/watch?v=iW6b4AXzVi8

Our site-
http://www.catalina-pby.nl/

Closing pic taken from flight deck of PBY of the other two ladies-

If all goes to plan we will be flying again early 2012, in time for the summer season. If the CAA cooperates, of course :cop:

The people here nonetheless are great... even though at 28 I'm the youngest dude there, everyone has 110LL running through their veins and are fantastic people.

Thank you for watching... I will take your questions now :haw:

# ¿ Dec 23, 2011 20:25

Tsuru: May 12, 2008

co199 posted:

You could probably zorch something real good with a JSTARS.

(2100x1500)

So they actually did start fitting the JT8Ds. Does aynone have any data on how it compares to the CFM56 retrofit and the original JT3?

# ¿ Jan 23, 2012 10:36

Tsuru: May 12, 2008

Ah, the Bell Airacobra... famous for being the world's first and only mid-engined warbird.

# ¿ Jan 30, 2012 22:08

Tsuru: May 12, 2008

7of7 posted:

I'm hoping someone with a better knowledge of airliners can answer a question about crosswind landings. It seems in videos like this that the wheel bogies on many airliners are somehow kept parallel to the runway during crosswind landings. However, I've done a bit of googling, and read a few airliners.net threads, and found that only the B-52 was actually designed to align the wheel bogies with the runway during such a landing. It seems pretty clear in the video above around 0:24(also shown below) that the A-340's wheels are aligned with the runway.

Can anyone settle for me whether or not any major civilian airliners are capable of turning the wheel bogies to align with the runway during a crosswind landing? I suspect the answer is no and some other mechanism such as simple inertia is at work in the video.

On older 737s the main gear axles can swivel a few degrees to make crosswind landings a little less bone-crunching (though this is a passive system, and not active and pre-set like on the B52), and on jets like the 777, 747 and A380 with a lot of main wheels the rearmost of them can swivel to make turning while taxiing a little easier on the tyres. On the 777 the rear 4 of the 12 main wheels, and on the 747 and A380 two out of the 4 main bogeys swivel IIRC. This is just for taxiing though, and not to make crosswind landings easier.

# ¿ Feb 12, 2012 12:54

Tsuru: May 12, 2008

ManifunkDestiny posted:

Wait where?

Not sure if this is what he is talking about, but it is a video of an F-16 entering a spin during a dogfight. I'm not even sure if a failure of the flight control system is what is needed to get an F-16 to spin, but I'm sure someone can fill in the blanks.

https://www.youtube.com/watch?v=i0XP-ULK2gM

e: no crash in this one, but recovery to normal flight.

Tsuru fucked around with this message at 22:34 on Feb 22, 2012

# ¿ Feb 22, 2012 22:32

Tsuru: May 12, 2008

CroatianAlzheimers posted:

I know this is from a few pages ago, but the kid and I were at YAM again and I got you some pictures of their KC135. I tried to keep Captain Katya out of the pictures, but she was intent on her pre-flight checks.

Awesome

I must say I can't wait to take my oldest for her first ride in one of our sims... I mean, she's almost two!

# ¿ May 10, 2012 20:29

Tsuru: May 12, 2008

Raikyn posted:

I did a couple of wallpapers for someone

With all the spergin' about stealth this is not getting enough love. Glorious new desktop found... thank you!

# ¿ Feb 5, 2013 11:00

Tsuru: May 12, 2008

grover posted:

But it was all caused by a single small oil leak. If a single small oil leak can create a cascade of failures that results in loss of multiple redundant systems and very nearly loss of the entire aircraft, that's a very serious design problem. The engine failure should have been contained within the engine.

I have two questions for Airbus:
1. Why didn't Airbus design the nacelle to contain the turbine stage like they did the compressor stage?
2. Has it been fixed?

That's because there is, at least to my knowledge, no containment requirement for any casing other than the fancase. FAA, EASA or otherwise.

Any failure of a turbine wheel is almost sure to be uncontained, on any engine. You can find many examples of this happening to older engines such as the CF6, JT8D and others.

# ¿ Mar 2, 2013 15:32

Tsuru: May 12, 2008

holocaust bloopers posted:

I'm thinking that could be it. The dramatic pitch up isn't something a pilot would do in a stall recovery. The gear being down is also peculiar because if the pilots established positive rate of climb, the gear would've been tracking up or already been up. This is likely a problem that occurred right at rotation so ya maybe a drastic change in the CG by cargo shifting.

This is actually the only possible way a 747 can come to a standstill in mid-air in a low energy state like this, barring maybe a stab trim runaway. You can see the latter is clearly not the case. With flaps 20, a rearward shift of CG of about 12 feet will do exactly this.
There are still people out there who think a large commercial transport won't drop a wing, see what happens when you put in some rudder.

Every loadmaster needs to see this movie... RIP to all on board.

# ¿ Apr 30, 2013 19:50

Tsuru: May 12, 2008

azflyboy posted:

From the statistics available within the US, it appears to be very rare.

A search of the NTSB's database only turns up 11 incidents for the phrase "runaway trim", and only a few of those were actual runaway trims (the rest were things like broken trim cables). Of those 11 incidents, only one involved an airline, which was operating a Beech 1900 turboprop. Of the four fatal accidents in the set, one was caused by the airplane being improperly loaded, one involved a pilot impaired by drugs, one was the pilot being distracted and flying into the ground, and the last was caused by improper maintenance resulting in the elevator trim operating backwards.

There were three incidents that actually involved runaway trims (two piston powered aircraft, one Cessna Citation), and none of them resulted in any fatalities, since most aircraft can be kept under some level of control through use of flaps, power changes, and brute force on the controls to counteract the trim.

One important (though probably obvious) distinction is that in smaller aircraft (including the Citation) you only move a small trim tab to offset the neutral point of the elevator and if you just offset the force, the aircraft is aerodynamically (nearly) identical to one that is in trim. On large aircraft the entire HS moves to avoid trim drag. Here, a stab runaway is typically an electric malfunction where the the stab moves to the forward or aft stop uncommanded. This is also the reason why yoke trim switches on Boeings and the like are always dual units, connected in serial so a failure of one will not trigger a stab runaway.

The key is that if you catch it in time, you have a fighting chance by deploying flaps, gear and whatnot. If you are too late with hitting the stab trim disco switches or the stab brake, the trim speed will end up outside of the flight envelope and you will die.

I know three examples of a stab trim runaway, two due to automatics and improper aircraft operation: AF447 and THY1951. Another one which was probably a true stab runaway happened in the 1960s in Belgium, where a Sabena B707 crashed near Brussels Airport. The aircraft was approaching the airport, until it pitched up uncontrollably and ended up flying a tight spiral at high thrust and extreme bank angle. It is suspected (FDR/CVR not available) the crew tried to use high bank angle to avoid a stall, but had zero chance to avoid a crash.

Tsuru fucked around with this message at 09:16 on May 1, 2013

# ¿ May 1, 2013 09:08

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# ¿ May 17, 2024 22:07

Tsuru: May 12, 2008

Linedance posted:

AF447 and THY1951 had nothing do with stab trim runaway.

azflyboy posted:

I don't see how either of those accidents had anything to do with trim malfunctions.

In the case of AF447, the pitch trim was functioning correctly up until impact, and the fact that the crew managed to stall the airplane (and hold it in the stall until it hit the water) is due to a mix of confusion and misunderstanding the FBW system on their part rather than any issue with the flight controls.

The Turkish Airlines accident also had nothing to do with the trim system. In that accident, the crew didn't disengage the autothrottle system after it began acting on commands from a malfunctioning radar altimeter, and somehow failed to notice the aircraft had slowed to around 40kts under the correct approach airspeed.

In both cases, the stab trim had likely shifted pretty far towards the nose up position before impact, but in both cases it only did so because it was trying follow commands from the flight crew, and there were no trim malfunctions of any kind involved.

What was the position of the elevator trim on both accident aircraft? Both these aircraft trimmed up without the crew realizing. Not a trim runaway in the direct sense, but definitely a contributing cause in both accidents. On AF447 the autotrim moved the THS fully up as per the FO's sidestick inputs which led to an AOA in excess of 40 degrees, and in the case of the Turkish the autopilot GS hold mode trimmed up until the stick shaker because the autothrottle was in retard flare mode.

# ¿ May 1, 2013 10:13

The Something Awful Forums > Discussion > Automotive Insanity > Aeronautical Insanity: switching to secondary tolerances

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