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Starlionblue
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Crashes Revisited. What Actually Happened?

Sun Dec 21, 2008 12:03 pm

I wanted to look into if the causes of some of the more spectacular crashes of late are now resolved. When there is a crash, there tend to be 1-5 looong threads in a week and then nothing. As we all know, investigators take longer than a.nut "experts" and final results don't often get published until months or years after the fact. So what were the results? My questions are:
- Is it now known what caused them?
- If it is known, what were the causes?
- Are they still being investigated, and if so, what does the investigation point to?

The crashes I am most interested in are the following. Feel free to add to the list.
- Spanair 5022 at MAD. MD-82. 20 August 2008.
- TAM Airlines 3054 at Sao Paolo. A320. 17 July 2007
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
wilco737
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RE: Crashes Revisited. What Actually Happened?

Sun Dec 21, 2008 12:54 pm



Quoting Starlionblue (Thread starter):

Such investigations usually take quite some time. Somtimes 2 years or so. Depends on how complicated and unclear the accident was.
Usually once the officials are done with their investigation they publish a final report which can be read on the internet. I think on some NTSB website or so. There you will be able to read the full report.

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Mastropiero
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RE: Crashes Revisited. What Actually Happened?

Sun Dec 21, 2008 1:41 pm

Latest I read about the Spanair crash was an article in spanish newspaper El Pais. Apparently it has been leaked that the pilots where in the middle of the take off checklist when they interrupted the checklist in order to get on the radio to ask for take off cleareance. It also says in the article that they interrupted the checklist right before checking the flaps. When they resumed the checklist they did it after calling the flaps. So, latest assumption is that they skipped checking the flaps due to getting on the radio.
 
tdscanuck
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RE: Crashes Revisited. What Actually Happened?

Sun Dec 21, 2008 5:37 pm



Quoting WILCO737 (Reply 1):
Usually once the officials are done with their investigation they publish a final report which can be read on the internet. I think on some NTSB website or so.

NTSB stuff can be found here:
http://www.ntsb.gov/ntsb/major.asp

The do a preliminary report early, then attach the final report when they're done. The recent ones are listed at the top of the page, you can search for others at the bottom.

You can also get everything back to 1967 here:
http://www.airdisaster.com/accrep/

Tom.
 
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RE: Crashes Revisited. What Actually Happened?

Sun Dec 21, 2008 6:49 pm



Quoting Mastropiero (Reply 2):
Apparently it has been leaked that the pilots where in the middle of the take off checklist when they interrupted the checklist in order to get on the radio to ask for take off cleareance. It also says in the article that they interrupted the checklist right before checking the flaps.

Assuming that's true, (I have no idea about the reliability of El Pais or the person who leaked the info), aren't we beyond this sort of thing now? I'm sure I'm not the only person who can think of at least half a dozen ways of making sure that an interrupted checklist gets picked up again at the right point.
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tdscanuck
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RE: Crashes Revisited. What Actually Happened?

Sun Dec 21, 2008 10:03 pm



Quoting BAe146QT (Reply 4):

Assuming that's true, (I have no idea about the reliability of El Pais or the person who leaked the info), aren't we beyond this sort of thing now?

Unfortunately, no. Electronic checklists help, but the vast majority of current airliners don't have them. There are other ways, obviously, but most of them rely on the humans as a crucial link and humans make human errors from time to time.

Tom.
 
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Starlionblue
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RE: Crashes Revisited. What Actually Happened?

Sun Dec 21, 2008 11:56 pm



Quoting BAe146QT (Reply 4):
Assuming that's true, (I have no idea about the reliability of El Pais or the person who leaked the info), aren't we beyond this sort of thing now? I'm sure I'm not the only person who can think of at least half a dozen ways of making sure that an interrupted checklist gets picked up again at the right point.

One would think. But humans are fallible in this regard. An argument for electronic pilots? Perhpas. But an easier solution as Tdscanuck says is an electronic checklist.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
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HAWK21M
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RE: Crashes Revisited. What Actually Happened?

Mon Dec 22, 2008 7:52 am

I'm very curious about the EXACT cause of the Flame out on the BA B777 at LHR........
regds
MEL
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tdscanuck
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RE: Crashes Revisited. What Actually Happened?

Mon Dec 22, 2008 6:14 pm



Quoting HAWK21M (Reply 7):
I'm very curious about the EXACT cause of the Flame out on the BA B777 at LHR........

So are a lot of people. Are you unsatisfied with the level of detail in the preliminary report or do you think they got the wrong conclusion?

Tom.
 
SEPilot
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RE: Crashes Revisited. What Actually Happened?

Mon Dec 22, 2008 6:43 pm



Quoting HAWK21M (Reply 7):
I'm very curious about the EXACT cause of the Flame out on the BA B777 at LHR........
regds

The most recent information I saw on another thread that they are focusing on the way the excess fuel is routed on the RR engine; the fact that it reenters the fuel intake AFTER the filters. Since the fuel is warmed by being run through the fuel pumps, it would help melt any ice/wax buildup in the filter if it were introduced BEFORE the filter, which is the case with the P&W and GE engines. Since all of the uncontrolled rollbacks reported have occurred on RR powered planes, this is thought likely to be the culprit. RR is considering changing the piping accordingly.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
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HAWK21M
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RE: Crashes Revisited. What Actually Happened?

Tue Dec 23, 2008 3:45 pm



Quoting Tdscanuck (Reply 8):
So are a lot of people. Are you unsatisfied with the level of detail in the preliminary report or do you think they got the wrong conclusion?

I find it difficult to believe the cause stated.What caused only this Aircraft to flame out when the aircraft type was operating for over a decade.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
SEPilot
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RE: Crashes Revisited. What Actually Happened?

Tue Dec 23, 2008 4:03 pm



Quoting HAWK21M (Reply 10):
What caused only this Aircraft to flame out when the aircraft type was operating for over a decade.
regds

From what I have read, the normal procedure for an aircraft arriving after flying through extremely cold airspace is to descend well before arrival and give everything (most importantly the fuel) a chance to warm up before landing. As I understand it, this flight descended relatively quickly. This appears to be one of those cases where a deficiency is very subtle and needs very precise circumstances to manifest. Look how long 737's were flying before one experienced a rudder hardover; as I understand it the potential was there on the very first one.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
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Jetlagged
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RE: Crashes Revisited. What Actually Happened?

Tue Dec 23, 2008 4:35 pm



Quoting HAWK21M (Reply 10):
I find it difficult to believe the cause stated.What caused only this Aircraft to flame out when the aircraft type was operating for over a decade.

It might help your understanding to realise the engines did not flameout, so it is not unique in that respect. The engines rolled back to an EPR a little above flight idle.

Quoting SEPilot (Reply 9):
The most recent information I saw on another thread that they are focusing on the way the excess fuel is routed on the RR engine; the fact that it reenters the fuel intake AFTER the filters. Since the fuel is warmed by being run through the fuel pumps, it would help melt any ice/wax buildup in the filter if it were introduced BEFORE the filter, which is the case with the P&W and GE engines. Since all of the uncontrolled rollbacks reported have occurred on RR powered planes, this is thought likely to be the culprit. RR is considering changing the piping accordingly.

There have certainly been rollbacks on GE90 powered 777s caused by FADEC problems. There was even an emergency AD on the subject, affecting the 777-200LR and -300ER. This was the first dual engine rollback on a RR powered 777 IIRC.

I'd be interested to know where you saw this speculation, or is it a "leak" from the AAIB investigation.
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Jetlagged
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RE: Crashes Revisited. What Actually Happened?

Tue Dec 23, 2008 4:46 pm

Quoting Starlionblue (Thread starter):
- TAM Airlines 3054 at Sao Paolo. A320. 17 July 2007

The official report is not out but as I understand it this accident happened as follows. The aircraft had been dispatched with No.2 engine thrust reverser inoperative. On landing the crew only retarded the left throttle, presumably because they were intent on only selecting reverse on No.1 engine. No.2 throttle being advanced prevented the ground spoilers activating. When auto-thrust disconnected No.2 engine spooled up to CLB power (the lever was in the detent). The aircraft therefore did not decelerate and veered off the runway with tragic consequences.

There were also other factors such as the wet runway and a runway surface which was not grooved to increase friction in the wet.

http://aviation-safety.net/database/record.php?id=20070717-0

http://en.wikipedia.org/wiki/TAM_Linhas_A%C3%A9reas_Flight_3054

[Edited 2008-12-23 08:47:40]

[Edited 2008-12-23 08:49:21]
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RE: Crashes Revisited. What Actually Happened?

Tue Dec 23, 2008 5:41 pm



Quoting Jetlagged (Reply 12):

I'd be interested to know where you saw this speculation, or is it a "leak" from the AAIB investigation.

I thought it was from a thread about the other RR 777 that just experienced a power rollback on one engine; but I couldn't find it. It could have been from an article; but wherever I saw it it makes a lot of sense to me. And apparently there have been other incidents with the Rolls engines on the 777.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
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Jetlagged
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RE: Crashes Revisited. What Actually Happened?

Tue Dec 23, 2008 6:24 pm



Quoting SEPilot (Reply 14):
I thought it was from a thread about the other RR 777 that just experienced a power rollback on one engine; but I couldn't find it. It could have been from an article; but wherever I saw it it makes a lot of sense to me. And apparently there have been other incidents with the Rolls engines on the 777.

Regarding the BA accident, the key is to identify what caused a near simultaneous engine rollback. A single cause affecting both engines. The chances of two unrelated rollbacks occurring at the same time are very small.

What probably caused the accident was the combination of circumstances (very low ambient temperature, use of V/S mode for step climb, continuous descent at low power). Such a combination could also have occurred with a GE90 powered 777.

The AAIB enquiry is the one which matters, not speculation in a thread on a.net.
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tdscanuck
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RE: Crashes Revisited. What Actually Happened?

Tue Dec 23, 2008 7:07 pm



Quoting HAWK21M (Reply 10):
I find it difficult to believe the cause stated.What caused only this Aircraft to flame out when the aircraft type was operating for over a decade.

Any aircraft failure that's not the result of a direct and obvious error is, essentially by requirements, extremely rare. So this particular failure may just have a probability of about once per 10 years (given the current fleet size & utilization). As the number of 777's increases, the frequency would creep up unless they took steps to mitigate it, which they've already done.

Also, the investigation hasn't yet disclosed how close airplanes are to getting into this situation in the past. It's entirely possible that most 777 flights with RR's ice up the heat exchanger during descent, but the higher fuel temperature and longer descent let that dissipate before the crew needs more thrust on final. This may be happening all the time, and it's only when you get exactly the right alignment of circumstances that it manifests in a way the flight crew can notice.

Quoting SEPilot (Reply 11):
Look how long 737's were flying before one experienced a rudder hardover; as I understand it the potential was there on the very first one.

Excellent comparison...my understanding is that this potential was always there in the original PCU design and it took many many years before it actually happened.

Tom.
 
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RE: Crashes Revisited. What Actually Happened?

Tue Dec 23, 2008 7:17 pm

Quoting Jetlagged (Reply 15):

Regarding the BA accident, the key is to identify what caused a near simultaneous engine rollback. A single cause affecting both engines. The chances of two unrelated rollbacks occurring at the same time are very small.

It does seem unlikely that the fuel would congeal in the same manner at the same time on both engines, but that does appear to have happened. What makes this plausible is the rapid descent. Just because chances of something are small does not mean it can't happen. What we do know is that the only common item between the two engines was the fuel; and the cavitation found in the pumps clearly points to obstruction on both engines. Since the fuel passed all tests, it must have something to do with the temperature, unless gremlins somehow got introduced.

Quoting Jetlagged (Reply 15):
Such a combination could also have occurred with a GE90 powered 777.

Yes it could, but the difference is that on the GE engine the excess fuel from the engine is reintroduced to the intake BEFORE the filter, which is the most likely for any congealing to block the flow. (The RR engine does it after the filter. The excess fuel, having been heated by the pumps, helps to melt any congealed fuel. As I mentioned earlier, RR is considering changing the piping to do just that.

"The AAIB enquiry is the one which matters, not speculation in a thread on a.net. "

What matters is the truth. The official inquiry certainly has the best opportunity to find it, but does not always do so. I certainly concede that our speculation is unlikely to discover something that the official inquiries overlook, but there is nothing wrong with discussing what we hear and read and exploring possibilities.

[Edited 2008-12-23 11:23:56]
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
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Jetlagged
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RE: Crashes Revisited. What Actually Happened?

Tue Dec 23, 2008 8:36 pm



Quoting SEPilot (Reply 17):
Yes it could, but the difference is that on the GE engine the excess fuel from the engine is reintroduced to the intake BEFORE the filter, which is the most likely for any congealing to block the flow. (The RR engine does it after the filter. The excess fuel, having been heated by the pumps, helps to melt any congealed fuel. As I mentioned earlier, RR is considering changing the piping to do just that.

A lot would depend on how much excess fuel flow there is at low RPM during a descent. If there is a high proportion of return fuel flow then the heating effect would indeed be significant, as you say. Most of the temperature rise in this return fuel would have come from the fuel/oil heat exchanger, not the LP and HP pumps.

What the AAIB appear to be considering is icing at the fuel/oil heat exchanger inlet. The fuel filter is downstream of this and it's unlikely that ice particles could get through the heat exchanger without melting. The scenario the AAIB have suggested is a sudden release of ice particles blocking the system. This would also mean no excess fuel to return and if the ice release was large enough and sudden enough it would block the inlet whether warm fuel was ported there or not.

My point about the AAIB enquiry being what matters doesn't mean people should not speculate about the possible causes. However that remains speculation only, based on incomplete information. Inaccurate information included in such speculation is not helpful, but inevitably it finds its way into such discussions on forums like these.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
SEPilot
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RE: Crashes Revisited. What Actually Happened?

Tue Dec 23, 2008 8:49 pm



Quoting Jetlagged (Reply 18):

What the AAIB appear to be considering is icing at the fuel/oil heat exchanger inlet. The fuel filter is downstream of this and it's unlikely that ice particles could get through the heat exchanger without melting. The scenario the AAIB have suggested is a sudden release of ice particles blocking the system. This would also mean no excess fuel to return and if the ice release was large enough and sudden enough it would block the inlet whether warm fuel was ported there or not.

This is much more accurate than my recollection; I was going from memory, and am not familiar with the system. You are probably correct.

Quoting Jetlagged (Reply 18):
My point about the AAIB enquiry being what matters doesn't mean people should not speculate about the possible causes. However that remains speculation only, based on incomplete information. Inaccurate information included in such speculation is not helpful, but inevitably it finds its way into such discussions on forums like these.

Quite true. And we have each other to point out inaccuracies, which usually happens. I certainly appreciate it when mine get pointed out.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
tdscanuck
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RE: Crashes Revisited. What Actually Happened?

Tue Dec 23, 2008 10:42 pm



Quoting SEPilot (Reply 17):
It does seem unlikely that the fuel would congeal in the same manner at the same time on both engines, but that does appear to have happened.

The theory is that the ice was forming for quite a long time on both sides...the triggering even for the rollback was attempting to throttle up, which happened to both engines simultaneously. Much has been made of the fact that the event happening at the same time on both sides makes it less likely, but what the AAIB described is a common-mode degradation of fuel flow on both sides that was only manifested when the flight crew throttled up. Since the throttle up happened on both sides at the same time, the error manifested on both sides at the same time, even though the ice buildup could have been progressing very differently on each side during cruise and descent.

Tom.
 
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Starlionblue
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RE: Crashes Revisited. What Actually Happened?

Tue Dec 23, 2008 11:12 pm



Quoting Tdscanuck (Reply 16):
Quoting SEPilot (Reply 11):
Look how long 737's were flying before one experienced a rudder hardover; as I understand it the potential was there on the very first one.

Excellent comparison...my understanding is that this potential was always there in the original PCU design and it took many many years before it actually happened.

Quite. In fact IIRC it took investigators about 2 years to even reproduce the fault in the lab.

Quoting SEPilot (Reply 17):

"The AAIB enquiry is the one which matters, not speculation in a thread on a.net. "

What matters is the truth. The official inquiry certainly has the best opportunity to find it, but does not always do so. I certainly concede that our speculation is unlikely to discover something that the official inquiries overlook, but there is nothing wrong with discussing what we hear and read and exploring possibilities.

Just to be clear, I didn't intend for this thread to be a sort of amateur detective discussion. I simply was interested in revisiting some events which are now forgotten by the general public but whose investigation may have uncovered some interesting facts for interested a.nutters.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
CosmicCruiser
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RE: Crashes Revisited. What Actually Happened?

Wed Dec 24, 2008 12:34 am



Quoting SEPilot (Reply 11):
the normal procedure for an aircraft arriving after flying through extremely cold airspace is to descend well before arrival and give everything (most importantly the fuel) a chance to warm up before landing.

Never heard of that. One of our longest legs is CDG-SFS and in winter I've seen cold fuel recirculation but never as in never descended early to allow anything to warm up. If I descended early on that leg I'd better be landing in HKG.

Quoting SEPilot (Reply 17):
the fuel would congeal in the same manner at the same time on both engines, but that does appear to have happened.

Interestingly I was talking to a 777 crew(another airline) in FRA the other day and they were saying it was the P&W eng that they were looking at for icing prob! All of our 777s we are getting are GE so I'm told.
 
Viscount724
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RE: Crashes Revisited. What Actually Happened?

Wed Dec 24, 2008 1:52 am



Quoting SEPilot (Reply 11):
From what I have read, the normal procedure for an aircraft arriving after flying through extremely cold airspace is to descend well before arrival and give everything (most importantly the fuel) a chance to warm up before landing.

That reminds me of the following dated December 12, 2008 in the Transport Canada accident/incident website.

A G450 aircraft, registration N500J, was in cruise at FL430 from Shannon, Ireland to West Trenton, NJ when, at 2128 AST, the crew requested a descent to FL380 and the aircraft was cleared for the descent. At 2133 the crew declared an emergency due to low fuel temperature and possible ice in the fuel, and requested further descent to FL350. The aircraft was cleared to descend to FL 360, due to traffic at FL350. No further assistance was required.
 
SEPilot
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RE: Crashes Revisited. What Actually Happened?

Wed Dec 24, 2008 10:56 am



Quoting CosmicCruiser (Reply 22):
Quoting SEPilot (Reply 11):
the normal procedure for an aircraft arriving after flying through extremely cold airspace is to descend well before arrival and give everything (most importantly the fuel) a chance to warm up before landing.

Never heard of that. One of our longest legs is CDG-SFS and in winter I've seen cold fuel recirculation but never as in never descended early to allow anything to warm up. If I descended early on that leg I'd better be landing in HKG.

I read this in one of the previous threads about the BA accident; since it is second hand I cannot vouch for its accuracy. But there was quite a bit of discussion that the handling of this particular flight was different than normal, and questioning whether or not it played a role.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
CosmicCruiser
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RE: Crashes Revisited. What Actually Happened?

Wed Dec 24, 2008 11:35 am



Quoting CosmicCruiser (Reply 22):
never descended early to allow anything to warm up.

I hope I wasn't misunderstood on this. Of course if I get a cold fuel recirc warning there's no choice but to seek a lower altitude but as far as getting down early at the destination...no.
 
soon7x7
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RE: Crashes Revisited. What Actually Happened?

Fri Dec 26, 2008 11:52 pm

A friend of mine just sent me the real time full cvr recordings from the Gols/ Excelaire mid air over Brazil...Recordings were from both aircraft before, during and post impact...What an bizzare experience especially since I know the Legacy pilots. The 737 immediate after impact went into immediate dive/rapid roll configuration while hearing the plane break up during the recording. The 737 seemed to exist for only 20-30 seconds after impact to break up...What a tragedy!...
 
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HAWK21M
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RE: Crashes Revisited. What Actually Happened?

Sat Dec 27, 2008 12:20 am



Quoting SEPilot (Reply 14):
And apparently there have been other incidents with the Rolls engines on the 777.

any details.I'm aware of Two.
regds
MEL
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SEPilot
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RE: Crashes Revisited. What Actually Happened?

Sat Dec 27, 2008 3:32 pm



Quoting HAWK21M (Reply 27):
any details.I'm aware of Two.

Since I cannot find the source where I got my original information, I'm afraid I cannot help. But I do recall discussion of other incidents involving only RR engines, but none as serious as the two we are talking about.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler

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