AA 737-800 Emergency Landing

[320DRIVER]

WASHINGTON, April 20 - The Federal Aviation Administration is looking into an emergency landing on Thursday by an American Airlines plane. The plane developed vibrations in its tail, which had been repaired right before the flight.

Botched repairs that require emergency landings are rare, but the tail was de-iced just before takeoff, which the agency recently discovered is linked to severe vibration. The agency said Friday that it ordered that planes of the type involved in the incident fly slower on takeoff if they have been de-iced.

On Thursday, the flight bound from Reno to Chicago, was delayed two hours for repairs to the stabilizer, the horizontal part of the tail. The tail problem was discovered in an overnight inspection.

Because snow was falling at the airport, the plane was also delayed for de-icing. Shortly after takeoff, at 12,000 feet, the pilot declared an
emergency because of the vibration and landed at Sacramento, which has a long runway and no high terrain in the area.

The plane, carrying 99 passengers and a crew of 6, is a Boeing 737-800. At the factory, a spokeswoman, said that some late-model 737 models had had tail vibrations because a part was not stiff enough. The company will begin installing a redesigned part this summer, she said.

[PaperTiger]

tail was de-iced just before takeoff, which the agency recently discovered is linked to severe vibration
Say what ??
There have been a number of ADs for 737NG tails but I don't see anything about de-icing. What possible effect could this have ? Or is this simply bad English (ie. the tail is linked to vibration not de-icing it !).
http://www.b737.org.uk/faaad.htm

[A and C]

De-icing fluid can get into the elevator balance panels and freeze the drill Boeing recomend is that after de-icing the stab trim should be set full (aircraft ) nose down and the elevator moved stop to stop at least six times to ensure that the fluid drains from the balance panels.

[eng1170]

just for info - we had a man from technical down south up looking at our bird with regards to starting mods for Boeings proposed new rudder design for 737. Apparently it may include 2 PCU's not the current single main PCU, this all seems to have come about from the 2 a/c lost in the States around '94/'95. I believe it will be a mandatory mod.;)

[breguet]

AA pilots are not submitting a petition to stop flying the 737-800 yet!!!!!

[scottwiser]

"Because snow was falling at the airport" from the orginal News citation. Not uncommon to see snow in April.

Scott,

[tired]

Good point, breugeut!! :) I'm sure they'll get around to it pretty soon ;) ;)

[None]

>breguet AA pilots are not submitting a petition to stop flying the 737-800 yet!!!!!


Wasn't it only 7 of the 10,000+ AA pilots that had made that petition? And I believe the APA leaders were publicly against that petition.

[5 APU's captain]

Did they use Type IV fluid, which can lead to freeze controls?

[320DRIVER]

I think there is an AD by the FAA (not on their website yet) that limits the B737-700 to 270 KIAS in all phases of flight after it has been de-iced until it is inspected by maintenance for fluid residue etc. I don't think that they specifically mention Type IV but is applicable to all fluids. I think the Type IV also caused problems to Scandinavian MD80s due to their elevator configuration but wasn't aware that it affected the B737 as well.

[EXCIN]

Not only icing can do this !!

According to the Emergency Airworthiness Directive 2001-12-51 "To inform flight crews of an operational limitation associated with elevator control surface vibration", you may not use the speedbrakes at speeds in excess of 300 KIAS.

Due to a lack of sufficient damping necessary to prevent elevator tab vibration they had problems on a flight with a 737-800 and during the 737-900 flight test program.

Boeing warned every user that: "Use of speedbrakes at speeds in excess of 320 KIAS could result in a severe vibration, which, in turn, could cause extreme damage to the horizontal stabilizer."

That's what happens when you design an airplane as a panic reaction due to the A320. The 737NG is just an airplane designed in the 60's which is over-modificated.

[I. M. Esperto]

The agency said Friday that it ordered that planes of the type involved in the incident fly slower on takeoff if they have been de-iced.


How does one fly slower on takeoff?:confused:

[PaperTiger]

Yes I saw the speedbrake AD, although originally it did not apply to the -800 (?). Seems like it does though. Looks like the original article I quoted confused (quel surprise !) two separate ADs.
Freezing the elevators would lead to a damn sight more than vibration I'd imagine.

[320DRIVER]

The newly published AD is at:

http://www1.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/WebNewAD/07084C655D8B45D186256BA700527D94?OpenDocument

[A and C]

As stated above this is mix up over TWO quite different AD,s.

The speed limitation of 300kt with speed brake deployed is due to elevator trim tab vibration and the resultant damage that may happen.

The de-ice fluid AD is as a result of the fluid freezing on the balance panel this effects the mass balance of the elevator this may also result in vibration.
Boeing have a crew drill to action after the aircraft has been de-iced. It should be remembered that all de-ice fluids will freez at the normal cruse altitudes of jet airliners.