Russian Plane Crash

[Anomalocaris]

If the plane was largely intact and its engines functioning normally When for whatever reason it suddenly climb from cruising speed and altitude to the point of stalling, then the plane would likely Experience large gain in altitude before the actual stall.

That's hardly possible with airbus systems in good working order. A 320 pilot once demonstrated to me what he could and couldn't do without the systems stepping on the brakes. A climb to a stall is virtually impossible, even if all the systems are disabled. Unless something took care of the safeties before that.

I said the aircraft was intact, not necescarily in good working order.

But in fact it is possible for out of safety envelope condition to happen even if the Airbus was mostly in good working order, as we saw with the air France Airbus A340 that pancaked into the Atlantic, and whose wreckage too 2 years to find, it is entirely possible for the fly by wire system on the Airbus to be fooled by an external air pressure sensor malfunction, leading to software commands that would destroy the aircraft.   The Airbus relies on differential readings from an array of external air pressure sensors to deduce the speed and attitude of the aircraft.   Failure of any one of these could cause the control system to detect of dangerous situation that does not in fact exist, and strenuously attempt to correct the dangerous situation, and in the process put the aircraft into a different dangerous situation which it could not detect.  What is more, Airbus uses a full authority fly by wire system.  Which means the fly by wire system would override any pilot input it judged to be dangerous.  So when the fly by wire system is confused by malfunctioning sensors and doing all it can to mitigate the danger which is in fact not there,  it is actually impossible for the pilot to override the FBW system and restore sanity.

In fact, one of the first Airbus A320s, same model as crashed aircraft here, also overrode pilot corrections and flew the plane right into the ground in front of spectators in 1989 because another sensor malfunction causing the computer to become confused over what the plane is actually doing.

But in this case, I think the aircraft is already catastrophically damaged when it deviated from cruise altitude and speed.

My guess is either a bomb, or explosive decompression had already either shattered major portion of the fuselage, or severed all control wiring. Because bombs tend to leave readily detectable evidence on the wreckages, my money is on explosive decompression causing massive structural damage. Perhaps the rear pressure bulkhead at the aft end of the passenger cabin blew out.

This aircraft sustained major damage by striking its tail on the runway during a landing early in its life. This could well have damaged the rear pressure bulkhead. If the repair was not properly conducted, the bulkhead may well fail after a number of pressure cycles. If that bulkhead blows out in flight, it could severe the plane's tail, or at least compromise all the control wiring to the plane's empennage.

[TheRocketSurgeon]

Damage to the tail which either severed it or else completely disabled the elevators is not consistent with what I read. The plane went into a rapid climb. The point of the plane's tail is to hold the nose up by pressing "down" at the back of the plane (unless it is a canard design, which the Airbus is not), so the loss of that control surface would cause a sudden dive, not a climb.

[Anomalocaris]

Not with a fly-by-wire aircraft.

Negative lift on the tail planes creates positive static stability that allows manual flight control.  But by working against the lift of the main wings, negative lift on the tail increase the induced drag, and reduce fuel efficiency.

Fly-by-wire aircraft can handle zero or negative static stability.  So they don't need tails to create negative lift.  In fact, they can handle tails with positive lift.  Positive tail lift makes the aircraft highly unstable.  But if the control system can handle the instability, then it also gives the aircraft very low induced drag and high fuel efficiency.

[TheRocketSurgeon]

All true, but I'm pretty sure that complete, catastrophic loss of either the entire tail or full control of the elevator would be beyond the capacity of an airliner's FBW system to handle, and because in all aircraft the center of gravity must be ahead of the center of pressure for the aircraft to fly in a straight line (again, I know FBW can handle unstable aircraft, but that's something you design into a fighter, which needs to turn sharply and suddenly, not an airliner) you'd still wind up with an a/c that's nose-down upon loss of the tail.

According to the PDF file, linked below, the A321 has manual backups in the event of power loss (page 39), and is capable of being aft-CG loaded for fuel efficiency, but does have positive pitch stability (nose-heavy design). There are warnings about fuel balance loading too far aft, so I suspect the a/c is not as tolerant as other designs in that respect.

http://www.737ng.co.uk/A320%20321%20FCTM...Manual.pdf

[Thumpalumpacus]

Perhaps the rear pressure bulkhead at the aft end of the passenger cabin blew out.

This aircraft sustained major damage by striking its tail on the runway during a landing early in its life.  This could well have damaged the rear pressure bulkhead.  If the repair was not properly conducted, the bulkhead may well fail after a number of pressure cycles.   If that bulkhead blows out in flight,  it could severe the plane's tail, or at least compromise all the control wiring to the plane's empennage.

This same sequence of events downed JAL 123 in 1985, including the tail-strike (which was followed up with a shoddy repair).

[Ludwig]

I've read that ISIS doesn't have the AA capabilities to shoot down a plane at such a high altitude so I'm going to with "bomb".

[StuW]

I've read that ISIS doesn't have the AA capabilities to shoot down a plane at such a high altitude so I'm going to with "bomb".

The expert on Sky News agrees due to the pattern of debris being consistant with multiple parts falling from the sky.

[Anomalocaris]

It looks like some sort of Heat bloom event attended the loss of control of the aircraft.  An engine fire, or even a fuel tank fire, would not be immediately fatal, and would not result in immediate loss of flight control, and would sound all sorts of warnings in the cockpit. So engine fire or fuel fire is not consistent with the lack of distress signals.

This leaves either a bomb, or a low order fuel detonation, which immediately inflicted enough damage to cause the aircraft to lose control, and either killed or incapacitated the crew right away.

The TWA b747 whose empty center fuel tank suffered a fuel vapor detonation off Long Island and generated all sorts of conspiracy theories in 1996 comes to mind as a possible analogue.

In that incident the empty center tank, not purged of fuel vapor, blew up when frayed wiring routed through the tank sparked amidst the fuel vapor.  The explosion compromised the fuselage structure sufficient to cause the nose of the aircraft, with the cockpit, to break off.  This caused then rest of the aircraft, minus the front third of the fuselage, to violently pitch up.   In many ways that incident seem to resemble what we know of this one.

However, in the TWA incident, the engines of the aircraft continue to function after the detonation, so the stricken aircraft gained a lot of altitude before stalling and crashing.   Here it appears the aircraft lost power as it went into the climb.

If it were a bomb, then evidence of the bomb explosion should surface soon as the wreckage is examined. Of

[Ludwig]

It turns out that the aircraft that crashed was owned by a company with a sketchy history that hasn't paid it's employees in a couple months.

http://www.msn.com/en-us/news/world/egyp...?ocid=News

[abaris]

Well, maybe just wait what the experts find out? In some weeks time?

As far as I know, none of us are experts in that field. Just saying, since every speculation leads into mralstoner territory.