RJ Crash Prelim

[enigma]

It sounds as if jetflyer has a reasonable scenario for an overtemp start. However, I find it hard to believe that the engine was rendered totally inop because of the overtemp. We used to get shown CT wheels in Kingair gs that had been "hot-started". In each case the engine was running when it was torn down because it wouldn't make rated power. I once flew a Lear that somehow suffered heat damage of uncertain origin. The Lears' TFE731 had burned through the nozzle, but was still making good power when it came off of the pylon. The Lear tipped us off about a problem because it started running more ITT than the other side.

enigma

 

[surplus1]

Jetflyer,

You're doing a lot of good thinking and many of your scenarios appear to be logical. However, your focus is entirely on the reported heat damage to one of the engines and how that might have happened.

I assume that you currently fly the CRJ so I offer some suggestions.

1) Don't focus exclusively on the possible "hot start". Focus on the entire scenario.
2) Before you get to how a hot start may have developed, think some about why the engines flamed out in the first place, apparently at the same time.
3) Think again about the altitude (FL). Then think about the speed. Then think about the AOA.
4) Then think about this - have you ever noticed the ignition lights come on temporarily during a brisk rotation in a normal takeoff? If so why does that happen?
5) Now go back to #3 and think about the stall protection system in this aircraft. Review your manuals and answer this question for yourself: What is the 1st thing that happens in the stall protection sequence? Why is that 1st and not the shaker?
6) How does the auto ignition system function and why is it there?
7) Go back to #2 again and ask yourself the why question.

Now apply any new information you may have found from those suggestions to your theory. I'm not trying to contradict or shoot down your theory, but only to expand your thinking (which is very good) a little more.

Remember that the NTSB report says the crew initially reported the loss of ONE engine and did not report the loss of a second engine until at 13000 feet. Yet the same report says that BOTH engines flamed out at the same time. Why does there seem to be a contradiction in this?

What would trigger the "memory items" you mention and how does that relate to the difference between what the crew allegedly said and what the NTSB says was a simultaneous double failure? What is the reason for the 1st memory item, given the "logic" of the systems?

Which engine was the one with evidence of heat damage (they didn't say both)?

Was that the same engine that the crew first reported as having lost or was it the other one that they reported at 13,000? Do we know that?

If the crew actually reported one engine out, but in fact both were out, why did that happen? Is it just a coincidence or is the report we got wrong?

Now go back to your own scenario and all the bells, whistles, noise from the ADG, etc., that you outlined and tweak it a little with your new information, expanding on the heat damage question.

We won't know what happened for some time, but your thought process is a good one. The more you know about your airplane the more surprises you can avoid. Even if your theory turns out to be way out of line your thought process might serve you well in the future.

PS. More food for thought ~Do the shaker and the pusher still function if the ADG is the only source of electrical power?

 

[jetflyer]

Thanks Surplus, Enigma, and Saab.

Well heck, good point Surplus about the continuous ignition coming on automatically when approaching a stall. I forgot about this.
But as they lowered the nose the continuous ignition would have gone back off right? I don't think it would stay on because you'd be away from the stall at that point. Then my scenario would be back in play?

My scenario for a reason the engines may have been damaged obviously has some problems with it since we don't know all the facts.

Like Enigma said the engines should have been able to be relit even with engine damage. But maybe not this time?
Maybe the engines experienced more than a spike like Saab said he had seen before. Maybe they shot up close to 1000+ degrees celcius for about 3 or more seconds.
Would this then render the engines useless? I guess it depends on how long they're that hot.

Like Surplus pointed out only one of the engines was reported to have engine damage. Maybe they haven't found that the other one was damaged yet? Maybe it was too? If the other one wasn't damaged they should have been able to restart it.

I think the most important question is why could the engines not be RESTARTED? Wouldn't we all hope that we'd be able to relight the engines after we experienced a double engine failure?

They requested 13000 feet. This to me says they had the APU running, because 13000 feet is the altitude required to attempt an APU start.
I think they were reluctant for whatever reason to admit they had experienced a double engine failure, especially since that what it seems the NTSB thinks.
They probably only admitted to ATC how much trouble they were really in when they couldn't get the engines started. They admitted they had really experienced the double engine failure and requested immediate vectors to the nearest airport.

Why could they not start the engines with the APU? Has anyone ever relit an engine in the air before? Is it easy to relight the engines in the air?
I would think that at 13000 ft or below it should have been pretty easy to do, UNLESS the engines were somehow EXTREMELY damaged.

There are so many questions to be answered. I know we all are anxiously awaiting more info from the NTSB.

I've never followed an accident investigation this closely before. How quickly does the NTSB usually give out information. Do you guys think in the next month or so we'll get to see a transcript of the cockpit dialogue from the CVR? Will we get to see in the next month or so data from the FDR?

Jet

 

[jetflyer]

One more thing I thought about from Surplus' post about the continuous ignition.

Someone mentioned that a source close the NTSB said the CRJ stalled. Say it atleast got the pusher.

Did they get the pusher before or after the double engine failure??
a) If you lost both engines FIRST the plane would slow very quickly if the nose wasn't lowered fast enough possibly causing a pusher. If the continuous ignition then comes on, is it enough to start the engines?
Maybe the speed was simply so slow still that the engines still could not relight even with the CONTINUOUS IGNITION coming on automatically. Then as they lowered the nose the CONTINUOUS IGNITION would go off, making my theory very possible again.

b) Then again if the stall occured FIRST then one would assume at FL 410 that the engines possibly would not have enough air to keep running even with the CONTINUOUS IGNITION coming on AUTOMATICALLY and a DUAL ENGINE flame out could still occur. But again as they lowered the nose and increased speed the continuous ignition would go off again making my theory possible after the engine speed slowed and the CONTINUOUS INGITION PUSH/SWITCH LIGHT was not IMMEDIATELY PUSHED IN like the Memory items call for.

I think either way slow speed probably caused EITHER the STALL to occur first or the ENGINES to flame out first.

Were they slower than the manufacturer and company reccomend? MAYBE NOT. Maybe they hit some turbulence or an atmospheric change?

No matter what, the NTSB has said they had a double engine failure at FL 410.
I tend to believe they've looked at all the data already. For this reason I'm assuming the engines both really quit at FL 410, and for what ever reason (probably fear) they were hesitant to admit this to ATC and maybe even to themselves.

Jet

 

[efiscompmon]

New Flight Operations System Analyst – Contributed by David White, Director, Administration

We would like to welcome Aaron Workman to our Company as our new System Analyst. Aaron comes to us after completing graduate work with NASA, were he was earning his Master’s Degree in Mechanical and Aerospace Engineering. In addition to doing statistical analysis on our operation, the Company plans to put Aaron’s engineering talents to work on certain performance issues, especially related to fuel burn.

Welcome aboard, Aaron!

Pinch-a-nickel--spending dollars to squeeze pennies (and squeeze you too!)

I'm surprised they don't have the FO pull the a/c out with a tug and start the engines at position and hold. Of course the FO would have to enter through the service door; want to keep on-time departures and all...

Seriously, how bad is the job market the an engineer has to come to Melvis after working at NASA to find ways to burn less fuel? How long until APUs are removed and we start with huffers and cross bleeds?

And they want a concessionary contract!

 

[sf3boy]

This may have been said before, but what is the altitude limitation for inflight engine starts on a Canadair and when/what altitude did they try first try to restart the engines?

 

[PCL_128]

This may have been said before, but what is the altitude limitation for inflight engine starts on a Canadair and when/what altitude did they try first try to restart the engines?

Windmilling airstart can be tried at FL210 with a speed of 300 kts. APU airstart can be tried at 13,000 ft. They haven't released the info yet on when the airstarts were attempted.

 

[sf3boy]

Thanks, PCL 128. Just was wondering, speculating, guessing on the circumstances. Best regards and sympathies from all at XJ.