News just reported CRJ crash...

[Toecutter]

Yes and no. You can use the APU to restart AN engine only with a double engine failure. The limit is 13000 ft max for this however, so you'd definitely try to windmill start it first on the driftdown. The APU cannot be used to restart an engine with the other engine running.

I stand corrected.

 

[~~~^~~~]

I think other airlines will follow with altitude restrictions. My observation has been that our IP's and experienced line pilots seem to believe 37,000 is the maximum sensible altitude for the airplane. Although nothing is codified, we are told of experiences of low IAS / Mach resulting in compressor stalls.

Two factors are involved. First, CF34-3B1 is correct that mass airflow is very important to these engines. I have seen the thrust carat react to slowing airspeeds. Simply put, the more air you ram into the front of the engine the more power it makes. Nearly no air in the front of the engine results in compressor stalls, although I will be surprised if they could be so serious as to cause dual flameouts in an engine with variable stators.

The other factor is the supercritical wing. This wing hates to go slow. The L/D curve on the slow side of the wing's envelope is steeper than you might think.

These two factors combined make the RJ a great airplane to be at FL410 if you are at .76 or more. At .68 you are someplace you do not want to be.

Other observations about the report are that this airplane about set a time to climb record for a 200 and that the RT engine may have been damaged during a airstart attempt.

Gossip is that this was a very low time crew. New hire FO and Captain with about a year's time with the operator. Anyone know?

This is a bothersome accident. Airplanes should not have dual flameouts in their certified flight envelope. My prayers are with the friends and families of my fellow RJ pilots.

 

[TonyC]

Enigma,


As I read through the timeline, those exact same questions came to my mind. Why didn't they declare an emergency and announce a dual engine flameout from the beginning, if indeed that's what happened? Did they not know 2 engines failed, or were they trying to hide something, perhaps a mistake they made? And more . . . The problem is, to even ASK these types of questions tends to paint the crew in a bad light.

These and other "why" questions are best reserved for after the investigation is complete. We might not like the answers, and we don't have the "rest of the story," namely the CVR. The cockpit conversation will undoubtedly provide better insight into the actions of the crew.

I'm dying to know, too, but let's be patient and respectful.

 

[TonyC]

GRRRRRRRRRR....


Double post deleted - - daughter interrupted me.


What happened to the fail-safe feature this board used to have that prevented double-posting?



HAVE A NICE DAY !

 

[hmmm]

The APU CANNOT restart the engines in flight on a 200 series. If you read the QRH, you'll see a note that reads "due to system logic, the apu cannot be used the restart the engines in flight" The only procedures in the QRH are for windmill and crossbleed, however, on the 700, the APU can be used to restart in flight.

Guess u didn't know the airplane very well, or you didn't read the QRH, or didn't read it or your other books very well. Maybe its just your memory. I have both the companies and the Bombardier's QRH in front of me at this moment. Direct copies of each other and there is no note anywhere in Emergency or Abnormal procedures like your referred to and they specifically take you through the in-flight APU assisted start procedure.

There is the windmill start.
The starter assisted crossbleed. (Engine to engine.)
Or in the case of the Double flameout the APU start and then if able the starter assisted crossbleed to start the second one.

 

[hmmm]

Actually, N-Number guy has a point.

Having had this aircraft at 41,0 on a number of ocassions, I can tell you the PSID is EXACTLY 8.2 when you're there (max pressure differential for the uninitiated).

The aircraft's pressurization system is not designed to take the aircraft higher and would exceed the limitation on said system.

I'm certain all those other factors Mmmm (signature mmmhmmm) mentioned were included in the certification of this aircraft, but pressurization is definitely ONE of the limiting factors to a FL 41,0 ceiling. If they weren't going to put a pressurization system capable of maintaining a higher flight level with the same cabin altitude, I'm certain they had no intention of doing test flights OUTSIDE THE LIMITATIONS OF THAT SYSTEM... that would be kinda foolish.

ummm hmmm No "Base Hopper" I mean Lear70 just who's side are you on. If the aircraft is certified at the ambient temp and weight at FL410, then it was certificated to operate that night at FL410 and if the engines flamed out it is the entities that certified its responsibility. They shouldn't have flamed in the first place.

The Max DP is EXACTLY 8.7 not 8.2 Mr. Initiated.

And yes pressurization is ONE of many factors.

And yes they due test these factors waaaaaay OUTSIDE the envelope, just ask the resident test pilot now teaching at the sim.

 

[FN FAL]

Enigma,


As I read through the timeline, those exact same questions came to my mind. Why didn't they declare an emergency and announce a dual engine flameout from the beginning, if indeed that's what happened? ........

Could it have been from the startlement of having two engines quit, getting dumped to the emergency power level, having the CWS going off and quite possibly every look up light on the dash illuminated? Plus, without bleed air, wouldn't there be some depresurization occuring at that time?

That's an awful lot of stuff going on at one time. You'll have to excuse the look up light reference, but I don't know the CRJ's at all...it's probably all on a screen with the new glass cockpits.

It would seem to me that there must have been a lot going on at that moment. Maybe all the communications and requests for altitude changes and such might not make sense to us now as we sit in front of computers in a relatively safe environment, but one would have to think that at the moment both engines shut down, it was a very unsettling moment to say the least.

Can anybody clue us in to how things might have appeared in the cockpit of a similar aircraft, similar situation...without any more speculation as to what happened with this unfortunate crew? What I am asking is, what would a person see in the cockpit in regards to changes in cockpit lighting if the plane went down to the emergency power level...if that's what happens when you lose both engines? What kind of bells and buzzers would be going off? Are there look up lights or do you get all your information off of a screen? Would there have been a loss of pressurization? How rapid would that be, and would that alarm be an audiable one as well?

Keep in mind, I just asking to get a sense as to what the cockpit environment would be like as far as sound, systems lost and indications in a double engine flameout...not for additional speculation on the current CRJ crash.

 

[hmmm]

Finally. To answer someone else question above as to why they didn't do some of the declarations over the radio.

THEY WERE BUSY.

On the CRJ the ADG would pop out which is a external generator with a variable pitch prop that would have given almost instant AC power so they would have all flight control and eicas screens up as well as one hydraulic pump hard wired to it.

There would be all kinds of eicas messages coming up to sift through. Some going away as soon as the ADG powered up which might be a second or a few.

The pressurization on the CRJ as certified would begin depressurizing with both bleed air pressure sources flamed out but would depressurize no faster than 500 fpm if the system springs in the two pressurization outflow valves were operating properly and their seals were clean.

The APU could be started at 30,000 for AC generator output and the bleeds could be transferred to the APU at 15,000 but if they did not get the engines started by windmilling at a speed of at least 300 kts passing 21000 they could start the engines off the APU at 13000 but no higher.

Why they didn't start in this case? The engines shouldn't have quit in the first place as certified. Hopefully we will all learn every factor involved here and nobody will hide anything or push aside their responsibility.

 

[Toecutter]

Guess u didn't know the airplane very well, or you didn't read the QRH, or didn't read it or your other books very well. Maybe its just your memory. I have both the companies and the Bombardier's QRH in front of me at this moment. Direct copies of each other and there is no note anywhere in Emergency or Abnormal procedures like your referred to and they specifically take you through the in-flight APU assisted start procedure.

There is the windmill start.
The starter assisted crossbleed. (Engine to engine.)
Or in the case of the Double flameout the APU start and then if able the starter assisted crossbleed to start the second one.

Hmmm,

As I stated earlier, Burritos corrected me on the procedure. I don't fly the 200 anymore, so you're right, I was thinking from memory on single engine procedures and I don't have a QRH at home. Sorry if I offended you.

 

[CatYaaak]

ummm hmmm No "Base Hopper" I mean Lear70 just who's side are you on. If the aircraft is certified at the ambient temp and weight at FL410, then it was certificated to operate that night at FL410 and if the engines flamed out it is the entities that certified its responsibility. They shouldn't have flamed in the first place.
QUOTE]

I don't think anyone's taking "sides" in the matter, just a discussion. It seems that the first statement the NTSB made indicated that the aircraft entered an "aerodynamic stall". If that turns out to be accurate..if that was the first thing that happened.. doing so could certainly flame out the engines, and a subsequent overtemp during an attempted windmilling restart could melt one. Correct me if I'm wrong because I may be getting my engines mixed up, but I seem to recall there is no overtemp protection in that scenario.

 

[hmmm]

Hmmm,

Sorry if I offended you.

Not I. Protecting the families and their memories of these two good people.

 

[paid4training]

what would be the benefit of that altitude?

 

[hmmm]

The only overtemp protection would be an eicas warning and a hand on the thrust lever. But if they maintained .70 kts up to 410 and leveled off there should not have been an overtemp or a stall as certified at the ambient temp and weight that they were flying at.

Speaking from experience.

 

[dondk]

And yes they due test these factors waaaaaay OUTSIDE the envelope, just ask the resident test pilot now teaching at the sim.

So why make such a big deal about FL410? I still find it odd that the NTSB focused on that one issue so quickly.

 

[hmmm]

So why make such a big deal about FL410? I still find it odd that the NTSB focused on that one issue so quickly.

Because they will be looking for reasons to blame the pilots over anyone else.
The FAA for use in this country, Transport Canada and Bombardier certified the aircraft for operation up there and that is where this mess started.
If it was certified for operation at that ISA temp and weight to FL410 there should be no question as to why they attempted to operate at that altitude.
If it was certifed to do it there should be no reason why not.