Originally Posted by
B2N2
One thing I want to emphasize here, it is entirely possible to regain control after an upset and still be in an unrecoverable situation due to lack of altitude.
As in the airplane is under positive pilot control and still crashes.
Simulator upset training will show you how little time you have before the situation becomes unrecoverable either because the airplane is so far out of the envelope that it will come apart during the recovery or insufficient altitude.
The question that remains is what got them there?
Prior to doing Mdive testing I ran LED and DES simulations using STAR CCM+ of high-resolution 3-D BAC447 series of sections and variants, and found that the Cl collapses at extreme mach numbers, well above MMo. That was also associated with a very large shift in the Cm. The wing works fine within the design envelope. Any extended time in an extreme nose low atitude is going to compromise the ability to generate adequate aoa to get a good recovery pitch rate going. This isn't grandads pitch problems in his P-38 or Spitfire IX, its not even the P-80's discomfort at high speed, and it isn't reflected in the QTG if you go play in the B737 sim. This isn't specific to the B737, it is just one of those things, doing supersonic aerobatics is bad enough if you can pull 9 G if you start from M0.8 vertical downwards.
[ before discounting the loss of g capability at high speed ask any phabulous phantom driver what the g available was supersonic, or how much real estate gets used up with a supersonic dive from 45K, due to the limited g available to pull out in such a case. And that is a wing that arguably was designed for high-speed flight and dogfighting. Some may unkindly argue that the Phantoms wings were only used to have a place to hang MERs and fuel tanks].
The speed buildup just from gravity is ~20 kts/sec at -90 FPA, at 45, is around. 15 knots/sec, without the engine thrust, which adds about another 4kts a sec in a vertical dive. Drag increase is a fair bit but is still low order, the B737 total drag at M0.8 at average weighs is around 5,000-7,000 lbs roughly, it isn't a large amount, compared to acceleration available from gravity. Most speed brakes reduce lift, and that increases the aoa that has to be set to get adequate g loading, and that increases buffet and shock effects. Now this is not what the FAA espouses on aerodynamics, but then the FAA still demands we teach Bernoulli's principle for lift which just ain't so. Move your hand across the sink full of water and soapy bubbles, and you will find that the circulation theory/ bound vortex is visible, including the start vortex, the bound vortex and a stop vortex. What you won't find is what we are supposed to teach pilots about how their plane actually flies, which while simple to explain is fundamentally wrong, and gets wrongerer the more that compressibility comes into play.
Mods; remove or not this post, it is your choice. It is factually correct, and the insistence of our industry to put it's head in the sand means we are bound to repeat the same mistakes needlessly.
What happened to this aircraft, 50/50 the CAAC will not find a cause, and won't agree with Boeing. There is a guy in Denver that worked on kinematic reconstruction of some flight paths by a different method to the one I used in the same accidents, both being variants of MLE to match the couple of data points that existed. In one case, the CVR was able to give the engine RPM from the broad band FFT, and the actual acceleration and deceleration was able to be found from the harmonic lines of the AC system which ran fans in the cockpit; The CSD has a lag function and the overspeed or underspeed of the CSD is traceable on the CVR. The CVR in this case may ahve survived, the EEC memories are most likely to have survived, the DFDR had a less than 50% chance of surviving for various reasons.
it is possible that the debris dispersion analysis with prevailing winds will prove or disprove that any component departed early in the event. It is unlikely, but it would be reavealing if ever found. Components of the stabiliser/elevator and tail will very likely be found from a failure point in the mid dive case, and would be evident as missing components from the local debris field. The military search radar from around Wuxu airbase may have tracked the debris from the aircraft, it is about the right range to have tracked targets.