Engine "Core-Locked"

[MolaKule]

quote:

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Pinnacle Probe Unveils Training, Engine Flaws
Aviation Week & Space Technology 06/20/05
author: Frances Fiorino

Pinnacle Probe

Finding the cause of an accident often leads to a cure--and the ongoing probe of Pinnacle Airlines Flight 3701 is highlighting the need for enhanced high-altitude training and safety management programs at regional airlines.

Those shortcomings came to the fore during the NTSB's June 13-15 hearing that aimed to gather more information about the events leading to the Oct. 14, 2004, crash of a Bombardier CL600-2B19 (a.k.a. CRJ200) regional jet that resulted in the deaths of the two pilots on board. The board's findings show that on that date Pinnacle Airlines Flight 3701, operating as Northwest Airlink, departed Little Rock, Ark., at 9:21 p.m. local time on a repositioning flight to Minneapolis-St. Paul.

The flight plan showed an intended cruise altitude of 33,000 ft. or FL330, but at 9:43 p.m. the crew requested a climb to 41,000 ft., the service ceiling for the aircraft, and maintained that altitude for about 3.5 min. prior to stickshaker. About 20 sec. later, the aircraft was in a 32-deg. nose-down pitch and 80-deg. left bank. In that time period, the stickshaker and stick pusher had been activated four times. FDR data indicated both General Electric CF34-3B1 engines stopped simultaneously at 41,000 ft.

THE CREW DECLARED an emergency at 9:55 p.m., and 4 min. later requested descent to 13,000 ft. At 10:03 the crew informed ATC of a double-engine failure and requested vectors to the nearest airport; they were directed to Jefferson City (Mo.) airport. The crew reported runway approach end in sight, and at 10:15 p.m. the aircraft impacted the ground and was totally destroyed.

The captain had accumulated 6,900 hr. total flight time; the first officer, 761.

NTSB findings show that the crew attempted restarts according to manufacturer and company guidelines. However, the attempts were unsuccessful.

"If just one of the two stalled engines had restarted, this accident would never have occurred," said ALPA Chairman of Safety Terry McVenes. "The crew followed proper procedures. . . .But both engines failed to start because they had suffered "core lock--a risk previously known only to engine and aircraft manufacturers."

The engine core lock phenomenon is not well-known or understood throughout industry. The term refers to the seizure of the engine's core, or inner spool, by differential cooling that causes parts to bind.

Bombardier said every "prone" aircraft (CL300, CL604, CRJ200, DHC-08) is tested prior to delivery. During initial aircraft certification, engines are forced to 0% core speed and the aircraft is accelerated to confirm that engines will not lock up and can be windmill-restarted.

The manufacturer said the CF34-3 engine series has two areas suspected of causing core lock-up: the outer balance piston seal and inter-stage seal. The latter was found to be a contributor and a design change was implemented, reducing the lock-up phenomenon to 1.5%.

The NTSB Operations Group Factual Report revealed details about Pinnacle's training program, including:

*Jet upset training consisted of 6 hr. of ground school and 20 min. of simulator training at FL350.

*High-altitude climbs and recommended climb profiles were neither conducted nor demonstrated during simulator training--but were discussed at pre- and post-flight briefings.

*Double-engine failure training scenarios were not provided to pilots during simulator training.

*Operations at 41,000 ft. were not discussed or demonstrated in any ground or similar training segment--but the CRJ service ceiling was discussed in ground school.

Further, investigators learned there was a "sense of allure" to some pilots to cruise at FL410 just to say they had "been there, done that."

Several safety improvements have been implemented since the Flight 3701 accident: Pinnacle placed a 37,000-ft. ceiling on CL600-2B19s and issued an alert bulletin telling flight crews to no longer accept or request clearances above FL370. Simulator training now includes high-altitude stall and stall buffet margin demonstrations. The airline also revised the instructor's guide to include single- and double-engine failures at 35,000 ft. in initial new-hire and captain upgrade training.

BOMBARDIER ON MAY 16 published a revised Airplane Flight Manual procedure for dual-engine failure aimed at improving chances of recovery. The FAA on June 2 issued a Special Airworthiness Information Bulletin instructing pilots on how to avoid the dangers of core lock.

The main training concern, according to ALPA, centers on low-time pilots shifting to jet operations too early, or pilots not gaining thorough training in high-altitude operations.

"The regionals are undergoing enormous growth and adding more sophisticated aircraft to fleets. The environment means pilots have less time to gain first-hand experience with aircraft before assuming command," says McVenes, who emphasized he is discussing regional carriers in general. "Regional carriers over the last few years have been transitioning from turboprop equipment, which typically fly below 25,000 ft. and in a slower [airspeed] regime where things just don't happen that fast," explains McVenes. He points out that aerodynamics differ between turboprop and high-performance jets, and that pilots need to recognize those important differences.

In contrast, he notes, pilots training at legacy carriers get a "big block" of high-altitude operations training.

Pinnacle said at the hearing that it intends to implement a Flight Operational Quality Assurance program, which will aid in detecting and correcting potential safety problems. The NTSB investigation of Flight 3701 is ongoing, and NTSB member Deborah Hersman, who chaired the three-day hearing, says the final report is not expected to be completed until late this year.

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[Hirev]

Never herd of that problem. Found this short PDF that gives some more explanation. Link PDF

 

[outrun]

Perhaps a pilot can chime in here...

At the point of double engine failure can the CRJ be put into a glide path like the space shuttle or something?

What I am getting at is that I hope this aircraft was not in free fall like a rock

 

[Drew99GT]

quote:

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Originally posted by outrun:
Perhaps a pilot can chime in here...

At the point of double engine failure can the CRJ be put into a glide path like the space shuttle or something?

What I am getting at is that I hope this aircraft was not in free fall like a rock

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Pilots train for this all the time. I'd personally rather be in a helicopter if the engine/s died (with a good pilot

).

 

[pitzel]

Never been past 32k in a CRJ (been to 39k in an A320, but only to avoid ATC congestion over the southeast USA), but sloppy airmanship shouldn't be tolerated amongst 'regional' operators any more than it tolerated amongst the majors, and if those regionals aren't training their pilots to the same standards as the majors, they really don't deserve FAA licenses.

I have my doubts whether there are are many, if any missions the CRJ can fly that really would benefit from a very high altitude (41k ft) within its performance envelope. Taking a plane to a very high altitude for the sake of doing so, and not for the sake of optimizing fuel consumption on a given mission is foolish.

 

[pitzel]

quote:

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Originally posted by outrun:

At the point of double engine failure can the CRJ be put into a glide path like the space shuttle or something?

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Once the engines are gone, the hydraulic power available is minimal. Yes there is a ram-air turbine for some hydraulics, but the RAT does not make up for everything.

http://www.airliners.net/open.file/191739/L

High altitude double engine loss is a very dangerous case because you are operating with minimal airspeed and the stall/buffet margins are minimal to begin with. It doesn't take long after a double-engine flameout to end up in a horrible situation.

 

[Shannow]

So that bloke that glided (is that a word) an airbus 80km onto a small island airport did something pretty schmick then.

 

[JohnnyO]

All that is possibly true, but to a right-wing conspiracy whacko like me, it's worth noting that the plane flew out of Little Rock, Arkansas. Therefore one should look to see if the pilots or anyone on the plane were connected in any way to the Clintons.

Arkancide--def. Committing suicide by shooting yourself in the back of the head with a rifle. (Coroner said so.) Occurs mostly in the state of Arkansas but victims have also been found in Ft. Marcy Park in Washington D.C.

 

[pitzel]

Looks like another CRJ, this time a CRJ-705, encountered another incident, again, at FL410

http://www.yyznews.com/Jun.html

" e)...on Thursday June 9th one of the new model CRJ-705s being flown by Jazz Air between Houston and Calgary had a stick shaker incident near Colorado Springs. The aircraft (C-GJAZ) was at FL410 and was at Mach 0.70 when the flight encountered a downdraft and the stick shaker activated. Maximum thrust was set and a lower altitude was requested. The airplane descended at approximately 1000 fee per minute with a 3 degree nose down attitude. An attempt to recover at flight levbel 4000 was made but the stick shaker activated briefly and the descent was continued. Recovery was made at flight level 380 and the airplane returned to a planned speed of Mach 0.77. There were 62 passengers on board and no injures were reported. The Transportation Safety Board of Canada has secured the flight data recorder and has provided an accreditted representative to the investigation. The NTSB will be conducting the prime investigation since it happened over U.S. airspace. "

Maybe a ceiling at 41,000 feet isn't appropriate? Maybe a design issue?

These incidents hit home for me because they are going to be deploying these aircraft on a rather long domestic route (3 hours) I fly numerous times every year. I prefer not to be in an aircraft that is operated so close to its "coffin corner" in terms of aerodynamic characteristics.

 

[flynavydiesel]

I just attend FSI refresher for the Navy C-9 and there was discussion of this incident. This is all second hand and I have no idea of the validity of this. From what I understand they were following the engine restart proceedure which required a very steep descent profile in order to build up airspeed. They traded altitude in an attempt to relight the engines. Apparantly the ERJ requires a real high speed for a windmill start. After a few attempts they then realized they had better start conserving the altitude but by that time they were too low and conversly crashed short of the runway.

These aircraft have very high lift capability and have good glide ratios. If they had set up for dead stick approach and turned towards an airport up at altitude and determined at what point they need to stop attempting the relight in order to dead stick it in they would be around today.

just my opinion.

 

[XS650]

quote:

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Originally posted by Shannow:
So that bloke that glided (is that a word) an airbus 80km onto a small island airport did something pretty schmick then.

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"Schmick" and you asked if glided was a word

It was an impressive feat, but airliners actually glide a lot better than tin kite private aircraft like Cesnas, etc. Assuming they still have their controls working.

Have you heard of the Gimli Glider?

Gimli Glider

 

[Shannow]

quote:

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schmick: Cool, great, awesome, etc. A way to express your approval.
Example: Very schmick, Mike.

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http://english.exue.com.cn/tools/slang/S.htm

Thanks for the link to the Gimli Glider.

 

[CTD]

It is obvious that neither the pilots nor the company had carried out the proper amount of training on these aircraft. To have your pilots fly with out training them on a multi engine stall is a accident waiting to happen. Saying that the manufacturer should have put a operating altitude on the airplane. And then a max altitude not to be exceded. just because the aircraft can go to the max doesnt mean you need to. the reality is these pilots flew the aircraft to its operating envelope with out proper training or guidence and thus caused not an accident but a neglegent crash. As for the pilot whom glided the aircraft 80 miles or so. he was also a glider pilot so he had an upper hand over an average pilot whom knows the theory behind gliding but hasnt practiced it all that much.

 

[flynavydiesel]

This flight was extremely bizarre to say the least. The two pilots also switched seats which is very bizarre. So the captian was sitting in the right seat and the copilot in the left seat. A fellow aviatior who works for Mesaba said the reports indicated that one engine failed which caused the aircraft to stall and depart. They ended up 80 degress right wing down and a descent rate of 13,000 FPM. They took about 1-2 minutes to recover and then attempted the relight proceedure. These guys were just asking for trouble.

They got in an unusual attitude situation and were sitting in seats where they were not trained. Seems like a small detail until you actually train and fly the majority of your time in seat and then move over to other. Then you realize that you will reach for the wrong switches because they are in different positions. That probably added to their confusion and detracted from a quicker recovery.

Sad situation to say the least.

 

[pitzel]

quote:

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Originally posted by CTD:
It is obvious that neither the pilots nor the company had carried out the proper amount of training on these aircraft. To have your pilots fly with out training them on a multi engine stall is a accident waiting to happen. Saying that the manufacturer should have put a operating altitude on the airplane. And then a max altitude not to be exceded. just because the aircraft can go to the max doesnt mean you need to. the reality is these pilots flew the aircraft to its operating envelope with out proper training or guidence and thus caused not an accident but a neglegent crash. As for the pilot whom glided the aircraft 80 miles or so. he was also a glider pilot so he had an upper hand over an average pilot whom knows the theory behind gliding but hasnt practiced it all that much.

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It was also a Boeing B767-200 series, fairly lightly loaded (obviously without fuel) which has a very, very adequate wing for the weight of the aircraft.

I suspect that the lift to weight ratio on the CRJ is substantially lower, due to the CRJ being a stretch derivative of the Challenger bizjet. The CR7 would be even worse.

I know airlines have been very eager over these past few years to fly the same number of passengers around with 'less' airplane (the CRJ-700 carries almost as many passengers as the smallest DC-9 model yet weighs dramatically less and costs a lot less to fly), but problems like these have been virtually un-heard of with 737's and A320s.

Not to draw any conclusions here, but it sounds to me like CRJ-700 operators will be trying to operate them at the highest altitudes possible, with as much weight as possible to make long range flights possible. Probably one of the most dangerous combinations -- especially if the wing is marginal for the weight of the plane.

 

[flynavydiesel]

Not to draw any conclusions here, but it sounds to me like CRJ-700 operators will be trying to operate them at the highest altitudes possible, with as much weight as possible to make long range flights possible. Probably one of the most dangerous combinations -- especially if the wing is marginal for the weight of the plane.

I think you nailed it right there!!

 

[outrun]

While we are at it another though came to mind.

Any remarks on the MD-88 & MD-90 aircraft safety wise?

Since people here raised wing ratios, one thing that always irked me perhaps irrationally is on how relatively "thin" the wings are in reference to the aircraft.

Of course compared to a CRJ a MD88 is a different class altogether I know.

 

[flynavydiesel]

I can talk to the MD serious since I fly the-33 series. That wing is extremely efficient and has a good glide ratio. The airplane was designed well and a is a very forgiving and stable aircraft. I have been in some tough situations with em. The problem is usually not with the airplane but with the pilots, the do not understand high speed and high altitude flight characteristics. These planes will get you up to an altitude where they are flying on the engines, ie you decrease thrust and you descend. Or you take a too steep of a turn at high gross weight and altitude and they aircraft will stall a wing tip due to boundary layer separation.

All these issues is reminiscent of when the major carriers got their first jet aircraft, they had numerous problems. These commuter airlines have not beefed up their training programs to keep pace with the up graded and higher performing aircraft.

 

[pitzel]

quote:

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Originally posted by outrun:

Any remarks on the MD-88 & MD-90 aircraft safety wise?

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Yes, proper deicing/anti-icing is imperative, even under certain conditions in the summertime. Even moderate amounts of frost can cause bad things to happen aerodynamically. Definitely more sensitive than a 320 or a 737 to contamination.

The certificated ceilings on those models of DC-9 you specify, I understand, are all under 40k feet. And they tend to be far more conservatively operated -- not many DC-9's are ever dispatched at MGTOW, whereas with the CRJ's, it is fairly routine to deliberately leave seats empty on longer runs just to keep the weight down.

So the probability of getting into nasty incidents such as the ones described would be somewhat less.

 

[outrun]

More off topic Flight Q&A:

1. Can turbulence by itself cause a loss of control great enough to down an aircraft?

I ask this as a few rough spots before had me praying the pilot would get us out of it safely

If it is simply "bumps in the road" I will not worry then.

2. During some turbulence it seems as if the wings are "quaking" movement wise. From a structural standpoint is there anything to worry about?

3. "Wind Shear" warning systems, during the relatively rapid landing and take off periods how effective are such sensor suites?

In other words by the time your alerted of shear at such speeds are you able to quickly counter react?