JETPILOT From United States of America, joined May 1999, 3130 posts, RR: 27
Reply 2, posted (16 years 3 months 4 weeks ago) and read 1786 times:
I know an investigator at the NTSB. I just thought I would pass this info which I received first hand on to others who may be interested in this inside information.
Sim evaluations have already been conducted in light of this crash with the stabilizer locked in the most downward position and it was found, acoording to the loading of the AC, a full up elevator would have bee needed to arrest the descent to 1300 FPM. The stabilizer would have stalled in this condition with the AC ending up in the situation described by eyewitnesses.
So this is maor than speculation on media hype. This is what you won't read in the papers.
So it may be true you know nothing, but I am more fortunate.
Tom in NO From United States of America, joined Nov 1999, 7194 posts, RR: 31
Reply 7, posted (16 years 3 months 3 weeks 6 days 21 hours ago) and read 1728 times:
JETPILOT is on the right track. If we look over the progression of information we have heard since last Monday night (aircraft out of control, stabilizer jammed, pilots working for over 30 minutes to correct problem, descent initiated to LAX, loud popping noises coming from tail area), it sure seems like some sort of stall or loss of stabilizer pieces may be a factor.
Nobody around here is saying that they know everything. However, some of us probably have a little more insight than others, and therefore have something to contribute to the discussion.
If we wait for the NTSB to release their final reports, or even official updates, we'll all be here a while. Besides, isn't the idea of a forum to share information and ideas?
Keep up the good work, JETPILOT, let us know if you hear anything new that you think we would be interested in.
Tom in NO (at MSY)
"The criminal ineptitude makes you furious"-Bruce Springsteen, after seeing firsthand the damage from Hurricane Katrina
Buff From Australia, joined Mar 2007, 0 posts, RR: 1
Reply 8, posted (16 years 3 months 3 weeks 6 days 18 hours ago) and read 1712 times:
Without commenting on the theory, the latest "sounds" reported by the F/A's tend to make me believe there was an inflight loss of part of the airplane. Additionally, the CVR correlation (such as it was) seemed to relate the final loss of control to 1/ a "bang" & 2/ a flap selection.
Whatever the case, a sad week in aviation it has been. Let's cross our fingers to hope we don't have to discuss another one in the near future.
R347216 From Canada, joined Dec 1999, 159 posts, RR: 0
Reply 9, posted (16 years 3 months 3 weeks 6 days 16 hours ago) and read 1696 times:
So far, from all you guys very good information. But I am flying scared.
There must be right this minute, people lined up at some airport , waiting to board an MD80, who are totally oblivious that this airplane is a death trap.
Surely this airplane should be taken out of service until the problem is rectified.
Or is that too simple? Is there something that a professional pilot can tell us which will make our fears groundless.
Let us hear from the professionals, pilots and aircraft maintenance personell who make these things go, and who drive them. They are the 'hands on ' people who are the ones who know. TELL US, would you let your loved ones fly on the MD80?
Or is this just a sad and tragic thing that happened to just one airplane?
But please, from all of you professionals, lets hear from you. TELL US.
NKP S2 From United States of America, joined Dec 1999, 1714 posts, RR: 5
Reply 10, posted (16 years 3 months 3 weeks 6 days 16 hours ago) and read 1690 times:
In deference to your rather strident request for info,I offer you this: I've worked on DC9's and MD80's for over a decade (and have co-workers who have worked the "nines" since they first came out). Damn good airplane. Solid and simple. Don't fall for the media's inflammatory comments...or they'll have you right where they want you.
Bruce From United States of America, joined May 1999, 5099 posts, RR: 13
Reply 11, posted (16 years 3 months 3 weeks 6 days 16 hours ago) and read 1692 times:
Now they are saying that on the CVR tape we hear an F/A tell the crew that they heard a loud "bang" from the rear, and the pilots stated that they heard it too. That sound also appears on the tape approx. one minute before the crash.
One piece of speculation now is that this was some part of the stabilizer or tail section that had come loose and was being slammed against the plane by the force of the wind.
could this be true?
ALSO, I heard a rumor somewhere that an AA MD-80 recently reported difficulty with the stabilizer and the problem turned out to be a short-circuited switch on the co-pilot's side. Has anyone else heard this?
Bruce Leibowitz - Jackson, MS (KJAN) - Canon 50D/100-400L IS lens
Pilot1113 From United States of America, joined Aug 1999, 2333 posts, RR: 11
Reply 12, posted (16 years 3 months 3 weeks 6 days 15 hours ago) and read 1686 times:
Yeah the American Airlines incident is true. The stabilizer was jammed on that one, owing to a short circut. However, the crew remained in control of the aircraft and landed in Phenoix.
Aircraft are only designed to 4 times their maximum weight for a short period of time. After that time, things break off the airplane. I think the designers design it so the 'non-essential' pieces break first. That just may happen to be the trim tabs.
The MD-80 is a reliable and safe aircraft. Just becuase the trim got stuck in the up position doesn't make it a death trap. This happens to other aircraft also. Heck-- it could even happen to my Piper Warror. In the world of emergencies a stuck trim tab usually is very routine; the manufacturer has tried and true remedies.
AAR90 From United States of America, joined Jan 2000, 3589 posts, RR: 44
Reply 14, posted (16 years 3 months 3 weeks 6 days 13 hours ago) and read 1672 times:
>>There must be right this minute, people lined up at
>>some airport , waiting to board an MD80, who are
>>totally oblivious that this airplane is a death trap.
The DC9 aircraft (MD80/90 are marketing names for different models of the DC9) is not a death trap. It is very reliable and very forgiving. Virtually all flight controls are simple cable+pulley setups with no fancy computers or hydraulics to cause problems.
>>Is there something that a professional pilot can
>>tell us which will make our fears groundless.
I've stayed out of this fray because so little is known about what _really_ went on that everything is speculation at this point.
>>TELL US, would you let your loved ones fly
>>on the MD80?
Yes, without the slightest hesitation.
>>Or is this just a sad and tragic thing that happened
>>to just one airplane?
Most probably a single incident due to the simplicity of the flight control systems involved.
>>But please, from all of you professionals,
>>lets hear from you. TELL US. Peter.
Ok Peter, but understand conclusions are based upon speculation and not upon facts. There are few facts known at this time.
MD80/90 Stabilizer Trim is accomplished using one of two electric trim motors that turn a simple screwjack raising or lowering the leading edge of the Horizontal Stabilizer. High speed trim is the normal mode used by pilots (control wheel thumb switches) and moves the stabilizer at the blazingly fast speed of 1/3 degree per second. Slow speed trim is normally used by the autopilot and moves the stabilizer at an astounding 1/10 degree per second. Pilots also have switches on center pedestal to control that trim motor as well.
There is a Stabilizer Trim Switch (red guarded) on the center pedestal that when uncovered permits the pilots to flip the switch and stop the high speed motor from operating. That switch position is appropriately labeled: "STOP."
Behind the Captain's seat (within easy reach using your left hand) are three circuit breakers that remove all electrical power to the high speed electric trim motor and controls. Took me about 4-5 seconds to find and pull all three in the sim during multiple failure simulation Thursday.
Behind the Captain's left shoulder (again within easy reach using left hand) are three circuit breakers that remove all electric power to slow speed trim motor and circuits. Took me about 2 seconds to find and pull these.
So what do you do when one or the other system fails? Disconnect all electrical power to that system and use the other system. What if neither system operates? Disconnect all electrical power to both systems and continue to fly the aircraft manually.
How? Pilot control yoke is cable/pulley system to "control tabs" on the trailing edge of the elevators (trailing edge of horizontal stabilizer). Pilot moves yoke which moves control tabs which changes aerodynamics along elevator moving the elevator which changes aircraft pitch attitude. Essentially the pilot flys the elevator to the position desired. Very simple, very reliable system.
In the Alaska Air mishap the flight was an hour into the flight. What do you think was flying the aircraft: pilot (high speed trim) or autopilot (low speed trim)? Most probably the autopilot hence the slow speed trim motor is the problem. Pull the three CB's and the problem is solved. If not, your normal trim motor (high speed) is three times faster and stronger than the slow speed motor so just "override" what the slow speed motor is trying to do using normal trim switches.
If it was a high speed motor failure, you flip the trim switch to STOP (takes about 1/2 second) and pull the three CB's to that motor (another 4-5 seconds) then use alternate trim (slow speed motor) to retrim as desired.
Ultimately, the worst case situation is when none of the above works and you end up with full nose up or full nose down trim condition (motors can't go any further). Aircraft is still flyable, but only at higher airspeeds. Remember, you fly the elevator to where you need it so you need airspeed to get enough aerodynamic forces to move it where you want it. Nose up situation is relatively easy since you can more easily use leg muscles to assist holding (pushing) the control column forward. Full nose down is much more difficult since its mostly arm/wrist muscles at work (must be why trim problems are flown in the sim the day prior to 48's --2 days off--). Either way, it is possible --although not easy-- to land the aircraft. First did this 12 years ago as an FO and just 2 days ago as CA. My wrists are still a little sore, but it can be done.
Note: Long distance press photos of AA MD80 at PHX show horizontal stabilizer in full nose up trim condition. Yes it was a short-circuit in co-pilot trim switches.
The only thing scary to me about the Alaska Air mishap is that it appears to have been caused by the pilots trying to do too much with a broken airplane. By that I mean that if you've got an aircraft with control problems and you've got enough control that one of you (pilots) has the time to radio your maintenance base asking about CB's (remember, its a mechanical cable/pulley flight control system), then you've got enough control at that point in time to land the aircraft as is. Never mess with putting power back on a broken system if the system is not _required_ for flight.
My speculation on Wed. morning was that the pilots messed up (ouch, that hurts) or Alaska's procedures are messed up (that hurts more) or there was much more going on that hasn't been revealed as of yet. To date (Fri.evening) all information released so far further supports that position. )-;
The DC9/MD80/MD90 aircraft itself does not appear to have a safety related design flaw.
AA CA MD90
*NO CARRIER* -- A Naval Aviator's worst nightmare!
Panman From Trinidad and Tobago, joined Aug 1999, 790 posts, RR: 0
Reply 16, posted (16 years 3 months 3 weeks 6 days 7 hours ago) and read 1655 times:
The tail stalling reminds me of an accident that occured to BEA 548 where the tail stalled and the plane fell almost vertically in a nose up attitude. Reports here though stated that the MD80 was in a nose down attitude so all similarities end there.
The reason i pulled this reference was because there is a problem unique to all T tailed aircraft in that once the tailplane stalls (which means the wings have already stalled), there is no way at all to recover the aircraft.