737 Vertical Stabilizer Trim

[Lantirn]

Hi everybody!

I just had a conversation with some friends yesterday about the vertical stabilizer trim of the 737's.

We compared the accident of the MD-80 Alaskan Airlines, with the Silkair 185, 737 (although its not sure that it was vertical stabilizer failure in the silkair flight).

There is a video in the internet that shows how the trim works in the 737, im sure that youll know it here. Aircraft trim system | Veoh Video Network (http://www.veoh.com/videos/v382244KFJh32DJ)

Infos about the 737 trim scematic that we found is here.
http://www.dephub.go.id/knkt/ntsc_aviation/MI-185_pdf_reports/MI-185_SilkAir_Figures.pdf

Now the question comes..!

How about if a vertical stabilizer trim fails (disconnects from the jackscrew) in the 737 just as in the MD80 Alaskan airlines??

I know that is more difficult due to the location of the trim stabilizer, but what IF ?

Is there any backup mechanism that you can maintain pitch control of the 737 aircraft ?

Thanx Guys

[cirr737]

According to Bill Boeing elevator is sufficient to maintain control of aircraft even with stabilizer in the most extreme position...

[Lantirn]

Thanks man.

The question was what if the stabilizer trim would separate from the jackscrew.:)

[Rainboe]

First, your question is using completely wrong terms. The vertical stabiliser is the fin, not the horizontal stabiliser or tailplane.

If the forward mounted screwjack should fail and break, then I expect the tailplane will lose it's forward stabilising force and would tend to go to max deflection and break. ie immediate break up of the airframe. I do not think it would remain fixed and allow you to work the elevator.

You and your friends have a funny topic on conversation in the pub!

[spannersatKL]

Surely it would go fully horizontal stab nose down with the screw jack sheared (airplane nose up). The horizontal stab is an inverted aerofoil on the 737 and would tend to fly and the lift forward of the hinge would make the stab nose down increasing the down force on the tail. As said earlier probably Mr. Boeing made the Elevator to just oppose the moment!!!

[Rainboe]

I really wouldn't like to try it!