AA Flight 587

[scottkin]

Not to beat a dead horse, but after some research I have a few questions. I dont have a conspiracy theory mindset but i'm very curious as to why the NTSB and the FBI discounted so many of the eyewitness reports of an explosion on board before the vert stab seperation? Over 349 witnesses interviewed and 95% claimed to of seen an explosion before the seperation. http://hometown.aol.com/missiletwa800/aa587.htm

[TriStar-MiStar]

I have asked this same question over and over and never got an answer that made any sense / had any logic. There seems to be lots of oddities surrounding the ArrowAir DC-8 crash at Gander, Nfld, too.

[chrisburns]

None of the wreckage had any signs of an explosion before impact and the data recorder also showed what was going on.

[Dmmoore]

Not to beat a dead horse, but after some research I have a few questions. I dont have a conspiracy theory mindset but i'm very curious as to why the NTSB and the FBI discounted so many of the eyewitness reports of an explosion on board before the vert stab seperation? Over 349 witnesses interviewed and 95% claimed to of seen an explosion before the seperation. http://hometown.aol.com/missiletwa800/aa587.htm

The eye witnesses saw and heard engine compressor stalls due to air flow disruptions in the inlet caused be the yaw motion set up by the rudder input. A compressor stall (engine surge) can cause visible flames from both ends of the engine.

Yaw an A300 30 degrees and the nose of the aircraft blocks ram air from entering the engine inlet cleanly. A 20 degree cant on the inlet is enough to disrupt air flow into the engine.

[Cam]

Eyewitness account can be notoriously inaccurate.

[scottkin]

Don a quick question. During tear down of the engine would investigators be able to tell if there was any pre-impact malfunctions including a compressor stall?

[Dmmoore]

Don a quick question. During tear down of the engine would investigators be able to tell if there was any pre-impact malfunctions including a compressor stall?

If the stall was caused by an internal failure the answer is very likely. A stall caused by unstable air followed by an impact with earth, not likely. The damage from the collision would hide or destroy any evidence of a stall.

Many stalls leave no indication at all. I've borescoped many post stall engines looking for tip clang on the compressor blades. The tips bend forward and clang on the non rotating stator. It's about 50/50 on finding damage, however "IF" I heard the stall, I've been 100% in predicting the outcome. Tip clang = engine change.

[scottkin]

Don just one more question and i'll go back to my corner. Is it possible that investigators would be able to detect any scarring on the engine or possibly the fueslage or wings from the stall? Such as scorch marks. I read a snipet where the inspectors found no evidence in either engine of pre crash failure. Thanks again.

[Dmmoore]

Don just one more question and i'll go back to my corner. Is it possible that investigators would be able to detect any scarring on the engine or possibly the fueslage or wings from the stall? Such as scorch marks. I read a snipet where the inspectors found no evidence in either engine of pre crash failure. Thanks again.

It's not likely. A stall caused by airflow disruption is not an engine failure, so the report of no pre-existing engine defects would be valid assuming engine stalls are involved. Flames from an engine surge (Stall) are in free air and a long way from the fuselage. They are of very short duration and would not leave much (if any) evidence on the aircraft.

The bigger picture is there is no indication on any explosion anywhere on board the aircraft. It's impossible to have an explosion anywhere in the aircraft and not have a trail of evidence.

[Gabriel]

Don, wouldn't a compressor stall or other type of engine stall / surge, specially those that "cause visible flames from both ends of the engine" and are seen or heard by 300 witnesses, leave an audible record in the CVR? Was there such evince in the CVR.

I don't remember so (but hey!, I don't remember that there was a bomb explosion recorded either).

[alanh]

People are likely to describe any loud bang as "it sounded like an explosion". Couple that with something like this (http://www.jetphotos.net/viewphoto.php?id=5761971).

[Dmmoore]

Don, wouldn't a compressor stall or other type of engine stall / surge, specially those that "cause visible flames from both ends of the engine" and are seen or heard by 300 witnesses, leave an audible record in the CVR? Was there such evince in the CVR.

I don't remember so (but hey!, I don't remember that there was a bomb explosion recorded either).

The sound may be recorded on the DCVR but it will be recorded on the DFDR if power was present at the time of the event. The stalls would have been after tail separation.

[Gabriel]

The sound may be recorded on the DCVR but it will be recorded on the DFDR if power was present at the time of the event. The stalls would have been after tail separation.
I don't understand the implications of what you are saying. The DFDR kept recording after the fin separation, didn't it?

Please do it fool-proof: Was there any evidence of the engine stalls recorded in the CVR or DFDR? If there was none, Why there was none? If the answer to that last question is "there was no power", Why there was no power?

[alanh]

The NTSB says about sounds:The CVR group examined all of the CVR channels to document any unknown or unusual cockpit or airplane sounds. The sound of a brief squeak and rattle at 0915:37.3 and the sound of two thumps at 0915:52.9 were associated with movement of cockpit items in response to the airplane’s encounter with wake turbulence. The CVR group identified no specific events or noises on the CVR that, by themselves, could be positively associated with the departure of the vertical stabilizer. Also, the Board did not determine the sources of sounds after the airplane was believed to have started its uncontrolled descent.The rudder separated at 09:15:58 and the CVR quit recording at 09:16:15, at the time of crash. Later in the report they show that the "loud bang" at 09:15:58 corresponded to the time the rudder separated -- the CVR group couldn't identify it on their own because they didn't have a reference for "sound of rudder falling off".

The main thing is, they found the rudder in the bay with an overstress fracture. It wasn't cut and it didn't blow up. The rudder didn't separate as part of an in-flight breakup because the jet was in one piece before it fell off.

[Uncle Jay]

After successfully observing TWA 800 arising from the ocean in flames and ascending to 11,000 feet, the eyewitnesses were packed into a bus and ferried to Queens in time to observe AA 587 explode in mid-air.

[3WE]

A few comments- a compressor stall sort of basically means it stops sucking air. Whether you suck air or don't, there isn't NECCESARILY any physical evidence of it (although Don mentions the blades being bent back).

I think one can say that 727 engine #2 stalled "somewhat regularly" without any sort of physical evidence or follow up needed.

Now along these lines: (This may be a stupid comment), but who says a compressor stall has to go "bang".

I do recall one on a 727 and it certainly did go BANG, but I also recall L-1011 RR start ups where there would be flames behind the engine, but no bang. A start up isn't a compressor stall, but I THINK the bang is sudden ignition of fuel-air mixtures...so even if the plane spewed some fuel-air into a 200 MPH slip stream, maybe it burned instead of exploded.

As to "no evidence of pre impact damage", I thought this aircraft DID break up (including engine separation) before ground impact- but at a time when speed and attitude would have built up & combined into forces generally expected to cause breakup.

[Dmmoore]

A few comments- a compressor stall sort of basically means it stops sucking air. Whether you suck air or don't, there isn't NECCESARILY any physical evidence of it (although Don mentions the blades being bent back).

Actually they bend forward.

I think one can say that 727 engine #2 stalled "somewhat regularly" without any sort of physical evidence or follow up needed.

Apples and oranges. Okay, P&W and G.E. They behave very differently in a stall. The Pratt is designed to accept an occasional stall as part of it's "NORMAL" operating experience without damage. The General builds engines to operate without stalling and thus when they do, the compressor blades can be damaged.

Now along these lines: (This may be a stupid comment), but who says a compressor stall has to go "bang".

While a quite stall may occasionally happen, a stall caused by blocking the inlet will almost always be an explosive event.

I do recall one on a 727 and it certainly did go BANG, but I also recall L-1011 RR start ups where there would be flames behind the engine, but no bang. A start up isn't a compressor stall, but I THINK the bang is sudden ignition of fuel-air mixtures...so even if the plane spewed some fuel-air into a 200 MPH slip stream, maybe it burned instead of exploded.[/quote

The flames you observed from the tail pipe at start up were not caused by a stalled condition. Over rich or not fully propagated flames in the burner section can cause the tail pipe flames.

[quote]As to "no evidence of pre impact damage", I thought this aircraft DID break up (including engine separation) before ground impact- but at a time when speed and attitude would have built up & combined into forces generally expected to cause breakup.

The noises heard and the fire seen may have been the sound of parts failing and engine separation. Fuel line breakage and associated ignition of the fuel could make a nice fire.

[scottkin]

In the link I'm providing below, check out the last few frames on the video from the toll booth. Im curious as to what was on fire as it dropped from the aircraft. Im assuming its the engine but im not sure. You can see the airplane in the video still above the flaming debris. Any thoughts on this? http://www.ntsb.gov/events/2001/AA587/board_mtg_anim.htm

[cegro27]

Reports were that one or both engines separated from the a/c before it crashed, so that [the engine(s)] would be the flaming debris you see in the video.

[Schorsch]

Just one remark as I am professionally connected to aircraft tails: it is the Vertical Tail Plane (VTP) and not the rudder. Big difference. If just the rudder had fallen off, no bang, no scrap, no bloodshed. But it was the whole VTP with the VTP attachments failing.

[FireLight]

Just one remark as I am professionally connected to aircraft tails: it is the Vertical Tail Plane (VTP) and not the rudder. Big difference. If just the rudder had fallen off, no bang, no scrap, no bloodshed. But it was the whole VTP with the VTP attachments failing.

If the rudder goes but the VTP remains, how would they turn? Do hydraulics remain intact if only the rudder goes? Or do they use differential thrust to get the bird back home?

[cegro27]

The rudder is only used to keep the nose centered with the aircraft's flight path during turns, or keeping the nose steady while flying in strong winds. The plane could make a turn without the rudder, it would just be an uncoordinated (sloppy) turn. The rest of the vertical tailplane, the vertical stabilizer, "is" needed to maintain the plane's directional stability. Without it (rudder included) the nose would have no stability at all and a crash would result.

As for the hydraulics, it would depend on whether any hydraulic lines were cut by the loss of the rudder, and what specific hydraulic systems were affected. Differential thrust could be used (assuming the engines were still attached) if the plane suffered a serious hydraulic failure that affected the use of the ailerons as well.

[Dmmoore]

Correct. The vertical stabilizer provides directional stability critical to aircraft flight. Remember the DHL A310 that took a hit from a missile and landed safely (though not without additional damage) without hydraulics, and most of the R/H outboard flap using only differential thrust. A masterful job of airmanship.

[Airbus_A320]

If the rudder goes but the VTP remains, how would they turn? Do hydraulics remain intact if only the rudder goes? Or do they use differential thrust to get the bird back home?
As stated before the ailerons can be used to turn the plane, it would just be uncoordinated, but they could get it back safely. A while back an Air Transat A310 out of Cuba lost the entire rudder and was able to return safely.

http://www.jetphotos.net/user-uploads/airTransatA310rudder-1.jpg

Not sure how good/accurate the two articles are, but they should give a basic idea of what happened.

http://www.iasa.com.au/folders/Safety_Issues/others/rudder-sep.htm

http://technology.newscientist.com/channel/tech/aviation/dn12951-composite-aircraft-may-hide-dangerous-flaws.html

[Leftseat86]

Correct. The vertical stabilizer provides directional stability critical to aircraft flight. Remember the DHL A310 that took a hit from a missile and landed safely (though not without additional damage) without hydraulics, and most of the R/H outboard flap using only differential thrust. A masterful job of airmanship.


IMO even more amazing is how long JA123 stayed in the air.

[Gabriel]

IMO even more amazing is how long JA123 stayed in the air.
Flying more or less with the same stability that a leaf in the wind (permanent oscilatons of very large yaw and bank angles in ecxess of 90 degrees).

[Dmmoore]

IMO even more amazing is how long JA123 stayed in the air.

It would have been quite a feet if they could have figured out how to keep its oscillations under some control. The out come may have been much better.

In truth, the length of the 747's fuselage vs the frontal area is much better than the Airbus. The 747 tends to be more stable with the vertical fin missing.

[FireLight]

It would have been quite a feet if they could have figured out how to keep its oscillations under some control. The out come may have been much better.

In truth, the length of the 747's fuselage vs the frontal area is much better than the Airbus. The 747 tends to be more stable with the vertical fin missing.

I hope you mean " ... more stable than the Airbus with the vertical fin missing." Otherwise, they've been wasting a lot of time, money and energy putting VF's on 747's. :lol:

[Gabriel]

It would have been quite a feet if they could have figured out how to keep its oscillations under some control. The out come may have been much better.

In truth, the length of the 747's fuselage vs the frontal area is much better than the Airbus. The 747 tends to be more stable with the vertical fin missing.
The sweep of the wings also adds directional stability, and the wings of the 747 are more swept than most (inlcuding all airbus).

Yet, not enough to make it usefully stable without a fin.

[Schorsch]

Flying without rudder is generally not a problem. Of course, it would be very fugly feeling, especially as Mr. Yaw Damper cannot do his magic. But it would work.
The other problem mentioned is hydraulics. The pictured A310 apparently kept his fluids. Otherwise he would have been in trouble.

The DHL A300 that was hit over Bagdad was lucky in two ways:
First, they flew a virtually empty aircraft. With full load the things would have become much more difficult.
Second, the crew did train that sort of thing a bit. A normal crew would have failed.

The Japan Airlines aircraft did have some fin area remaining.
Without VTP no conventional current FAR25 passenger aircraft is controllable, at least not under standard conditions. I read an AIAA paper applying this problem theoretically. It concluded that the aircraft can be controlled in total absence of a VTP, but it needs some sort of dedicated (automatic) controller. Theoretically something you could put into the EFCS, while the current approach of decoupling the pilots pedals from the actual rudder makes sense, too. For the A320 and earlier A330/340 this was the only control that was really controlled directly, now you control sideslip angle via pedal.

The sweep of the wings also adds directional stability, and the wings of the 747 are more swept than most (inlcuding all airbus).
The B747 has 37.5°.
The A380 only gets 36° in one section.
Rest of the Airbus fleet is lame and slow.

[Highkeas]

I recall a Concorde lost the upper portion of its vertical stabilizer in flight and landed safely.

[Dmmoore]

I recall a Concorde lost the upper portion of its vertical stabilizer in flight and landed safely.

It was the upper portion of the rudder.

[Louis Gonzalez]

A question please: Why do large airliners tend to flip upside down when they lose all or parts of their tails in an accident? (1956 Crand Canyon Accident, TWA Connie, Aeromexico DC-9 mid-air in Cerritos, CA, and many more). This unfortunate scenario seems to happen with sad regularity in accidents of this category.

Does it have anything to to with the center of gravity of the remaining airframe?

I understand that if the horizontal stabilizer is gone, there's nothing left to counterbalance the normal "nose-down" tendency, but why do the aircraft often become inverted as well? I would think there's more weight on the lower parts of the airframe than the upper parts, especially on low-wing aircraft.

It's bad enough that you're falling uncontrollably nose down, but it must be even so much more horrifying to go down inverted.

I'm not sure of the attitude of Flight 587 in it's last few seconds, but any opinions would be greatly appreciated. Thanks!

[Verbal]

I think you should concentrate on not dropping flyballs when playing left field for the Arizona Diamondbacks, Luis.

[TaCA]

I think you should concentrate on not dropping flyballs when playing left field for the Arizona Diamondbacks, Luis.

haha, I think he's playing for the Marlins now, aren't you?

[Verbal]

I think he's playing for the Marlins now....
Concur. (http://sports.espn.go.com/mlb/players/profile?playerId=2419)

[TaCA]

A question please: Why do large airliners tend to flip upside down when they lose all or parts of their tails in an accident? (1956 Crand Canyon Accident, TWA Connie, Aeromexico DC-9 mid-air in Cerritos, CA, and many more). This unfortunate scenario seems to happen with sad regularity in accidents of this category.


Can't leave out Alaska Air 261 just off of Point Mugu.

[Dmmoore]

A question please: Why do large airliners tend to flip upside down when they lose all or parts of their tails in an accident? (1956 Crand Canyon Accident, TWA Connie, Aeromexico DC-9 mid-air in Cerritos, CA, and many more). This unfortunate scenario seems to happen with sad regularity in accidents of this category.

Does it have anything to to with the center of gravity of the remaining airframe?

I understand that if the horizontal stabilizer is gone, there's nothing left to counterbalance the normal "nose-down" tendency, but why do the aircraft often become inverted as well? I would think there's more weight on the lower parts of the airframe than the upper parts, especially on low-wing aircraft.

It's bad enough that you're falling uncontrollably nose down, but it must be even so much more horrifying to go down inverted.

I'm not sure of the attitude of Flight 587 in it's last few seconds, but any opinions would be greatly appreciated. Thanks!

Different aircraft respond differently to the loss if specific pieces of the aerodynamic control surfaces. Many aircraft have suffered a partial failure of some aerodynamic surface and were controllable. The loss of an entire stabilizer means the control and design stability over that axis is gone. Inverted is the position a DC-9 (Including all MD-80 series) becomes stable when the horizontal stabilizer departs the aircraft.

[Airbus_A320]

Can't leave out Alaska Air 261 just off of Point Mugu.
That one had the horizonal stabalizer trim travel past where it was supposed to causing the plane to dive uncontrollably. I don't think it actually came off.

[alanh]

The NTSB report says that the stabilizer went at least 15 degrees down, but doesn't indicate that it separated. The normal limit is 3.1 degrees.

[Louis Gonzalez]

I think you should concentrate on not dropping flyballs when playing left field for the Arizona Diamondbacks, Luis.

I wish I was that pro baseball player! Then I could afford to buy my own private jet! (wether I dropped the fly balls or not!)

Thanks for all the replies, guys

[Schorsch]

I'm not sure of the attitude of Flight 587 in it's last few seconds, but any opinions would be greatly appreciated. Thanks!

That is also important to remark: while JAL123 was somehow flying normally when it lost its tail, AA587 lost its VTP at close 20° sideslip angle and considerable yaw rate. The rupture was due to large bending loads due to sideslip and torsion loads when rudder was fully deflected in opoosite direction. Rudder retraction at full sideslip is what basically designs VTPs today.