RJ Crash Prelim

[DirkkDiggler]

I would say that you are accurate that in the above scenario, a lot of fuel is being dumped into the engines. However, after a flame-out, there is no more flame inside the engine to ignite that fuel. The only way to get the fuel to light is to turn the continuous ignition on. So unless the continuous ignition were on, the fuel would just be pissing out the back of the engines. If anyone disagrees, please educate me.

 

[jetflyer]

Dirk,
Thanks for replying so fast. I didn't think about there not being a flame. You're right. Thanks. How about this then:

SAY DOUBLE ENGINE FAILURE OCCURS:
You'd be losing pressurization, get 20-30+ Cautions and Warning lights. The ADG would be popping out, making things very loud. If the NOSE were not IMMEDIATELY LOWERED, the plane would most likely get a stick shaker, then PUSHER, because airspeed would degrade very quickly.

SAY 3 MINUTES HAVE PASSED BY, fuel has been pumping in the engines like crazy all this time, then the MEMORIZATION ITEMS ARE BEGAN.

FIRST MEMORY ITEM: Continuous Ignition ON.

What would happen then I wonder?? Could they almost immediately overheat the engines after turning on the continuous ignition if a couple minutes have passed by and ALL THAT FUEL HAS BEEN PUMPING IN THE ENGINES before the CONTINOUS IGNITION is turned on??

Again I don't know that's why I'm asking. But if this were the case and the engines wouldn't overheat till the CONTINUOUS IGNITION were turned on, they HOPEFULLY could catch the OVERHEAT in time and bring the thrust levers to shutoff before damage could occur.


Jet

 

[jetflyer]

I thought about this some more. The fuel would be pissing out the back of the engines like you said Dirk so a build up of fuel would not occur.

BUT IF THE CONTINUOUS IGNITION were turned on and because the speed would only be about .70 mach for a glide at that altitude, it would be essentially like a WINDMILL START with not enough speed. The RELIGHT ATTEMPT for the windmill start is not even supposed to be attempted until below FL 210 in the CRJ, so at FL 410, I would think the air would not be dense enough for a restart anyways.

So if they turned the Continuous ignition on LIKE THE MEMORY ITEMS SAY, the engines most likely WOULD NOT RESTART but would immediately begin to overheat.
If the engines had ALREADY CONTINUED TO WIND DOWN to almost nothing I would think an OVERHEAT and HOT START would be VERY LIKELY, VERY QUICKLY.
They would have to do number TWO in the MEMORY ITEMS pretty quickly at that altitude I would think:
2) THRUST LEVERS--SHUTOFF

If the thrust levers were not brought back quick enough after the Continuous ignition was brought on with too low an airspeed and TOO LOW AN ENGINE SPEED at SUCH A HIGH ALTITUDE damage WOULD OCCUR ALMOST IMMEDIATELY CORRECT??
This would leave any future relight attempts probably USELESS if the engines were already severely heat damaged, leaving a forced landing as the only option.

SORRY FOR ALL THE SPECULTAION. Just trying to see if I can figure out how to prevent such a HORRIFIC TRAGEDY from happening to me in the future. Thank you guys.

Jet

 

[Freddie Spencer]

So if they turned the Continuous ignition on LIKE THE MEMORY ITEMS SAY, the engines most likely WOULD NOT RESTART but would immediately begin to overheat

Overheat from CONT only? Don't think so pal..

BTW, "overheat:" sounds like you are jappin about Chevy -89 van with a busted radiator

 

[jetflyer]

Hey Freddie,


NO NOT ONLY THE CONTINUOUS IGNITION. You'd have fuel.

The ignition does what to fuel? Ignites it right?
If the engine speed is not fast enough you get fire but no operating engine, giving you a HOT START.

Jet

 

[jetflyer]

What I'm trying to say is that a HOT START is very likely at FL 410 I would think.

Say it took them 1 minute before they could begin the DOUBLE ENGINE FAILURE MEMORY ITEMS. At that point you'd basically, when you turn on the CONT IGNITION at that altitude if the engines had already spun down, be attempting a WINDMILL start with too low an airspeed.

Jet

 

[DirkkDiggler]

Jetflyer,


I'd say you've got a pretty decent theory as to why the engine may have had some heat damage. I don't know if that's what happened but at least it's a possible scenario. Thank god. Someone on this board has a brain, and uses it too. I was giving up hope.

 

[jetflyer]

Thanks Dirk, LOL.

 

[jetflyer]

Dirk,

It possibly may have been the reason they had to do the forced landing as well.

Haven't we all been wondering: Why couldn't they get the engines restarted??

We've all been sitting back thinking that we'd have been able to do the QRH procedures and get the engines restarted with no problem. MAYBE NOT.

A windmill start is a crazy procedure. You're not even supposed to begin it until FL 210 in the CRJ50. The QRH says you will even lose about 5000 ft at the required 330 kts.

My theory is and it's only a theory:
1) One minute or MORE passed after double engine failure occured before the DOUBLE ENGINE FAILURE memory items were begun.
2) With the engines having already spun down now, turning on the CONTINUOUS IGNITION is ESSENTIALLY a WINDMILL START at:
a) too low an engine speed
b) too low an aircraft speed
c) too high an altitude with very thin air
3) Under these conditions and GIVING FIRE TO FUEL, a HOT START COULD occur VERY VERY QUICKLY, if the thrust levers are not brought back to SHUT OFF. If they were only brought back to IDLE the HOT START would have continued.
4) If a HOT START happened this could have left them with USELESS ENGINES and making a forced landing of great importance.
5) This is maybe why they had to give up restart attempts and had to ask where the nearest airport was.

ALL MY OPINION and SORRY FOR THE SPECULATION. I'm trying to see if I can figure out how to handle this in the future to save me and my passenger's lives.

Jet

 

[DirkkDiggler]

Of course, that's assuming that they didn't to the memory items for a double engine failure immediately. I can't say whether they did but I can certainly see how easy it would be lose your train of thought given all the chaos that would be going on all at once.

 

[jetflyer]

Dirk I agree,

Losing your train of thought would BE VERY EASY to see with losing both engines.

When starting the CF34-3B1 engines we're supposed to wait till atleast 20% N2 on the ground.

Say turning on the Continuous Ignition was delayed by one minute:
Them turning on the Continuous ignition like they are SUPPOSED TO DO right after a double engine failure BUT with a slow engine speed where the engines have already spun down and with the very thin air up at FL 410 would have been about the EQUIVALENCY in MY OPINION OF:

1) Bringing the thrust levers to IDLE during an engine start at about 2-3% N2 at SEA LEVEL. <---Which would always cause a HOT START

Jet

 

[DirkkDiggler]

Not if they put the ignition on immediately as you're supposed to do from memory after a double engine failure. The N2 does spin down but there's plenty of time to get the ignition on while they're still spinning fast enough.

 

[jetflyer]

Yea,

I'm not saying this is what happened but it could have, I guess.

These would have all been happening:
MASTER CAUTION and WARNING flashing
bells and whistles going off
the AIR DRIVEN GENERATOR popping out of the nose making all sorts of noise,
and losing pressurization slowly
loss of some of the screens in the RJ till the ADG kicked in
a possible stick shaker and PUSHER if the nose was not IMMEDIATELY lowered because of the bleeding off of the airspeed very quickly with no engines.
Maybe having to don oxygen masks.
A ton of other things could have been going on and it was DARK the whole time.

Not to mention the immediate thoughts through their heads:
Oh Schnit!
I'm gonna be fired.
I'm gonna possibly not live.
ETC.

We're all told to slow down in these scenarios and not rush to judgement. I think almost all of us would have been delayed by trying to keep the plane from stall/spinning and being extremely overwhelmed that hitting that CONTINUOUS IGNITION button may have been delayed or not even IMMEDIATELY thought of.

Jet

 

[DirkkDiggler]

I agree.

 

[saabingitagain]

I don't think a hot start would cause obvious external heat damage. The hot start would take place in the combustor and be contained there. I have had GEs go hot.. real hot.. over 1000c in the blink of an eye.. no damage.. just an inspection and a lot of po'ed pax.