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Malcolm

Overrun MD-83's elevator jammed by gusts while parked

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  • 08 March, 2019
  • SOURCE: Flight Dashboard
  • BY: David Kaminski-Morrow

US investigators have determined that localised air turbulence damaged the elevator of a parked Boeing MD-83 to the extent that it jammed when the aircraft attempted to take off from a Michigan airport two years ago.

The crew of the Ameristar aircraft aborted the take-off after the jet failed to rotate during its departure from Willow Run airport, near Ypsilanti, on 8 March 2017.

National Transportation Safety Board analysis found that the aircraft had been parked on the ramp for two days close to a large hangar.

While the surface winds and gusts did not exceed aircraft design limits, computational fluid dynamics simulations showed the hangar’s presence generated localised turbulence with a vertical component that “rapidly” flipped the MD-83’s elevator surfaces up and down.

This caused the elevators – which, by design, did not have gust locks – to strike their mechanical stops, sufficiently hard to jam the right-hand elevator in a full trailing-edge down position, leaving the aircraft incapable of rotation during take-off.

Circumstances of the accident, says the inquiry, highlighted that Boeing’s safeguards “do not adequately protect” crews and passengers from the possibility that a free-floating elevator can become jammed before departure.

The NTSB says there is a “lack of a means” for crews to detect a jammed elevator during pre-flight checks on the type.

It says the crew had calculated the V1 decision speed as 139kt and rotation speed as 150kt. The call to rotate, from the monitoring pilot, came at 151kt airspeed but, while the left elevator moved 15° up the right elevator stayed 16° down.

The aircraft, which reached a maximum airspeed of 173kt, did not rotate and the captain aborted the take-off roll.

NTSB analysis found the jet had travelled 5,850ft along runway 23 before the crew applied brakes, leaving just 1,800ft of paved surface. It overran the paved surface at 100kt and struck a raised perimeter road at 40kt before coming to a halt.

Investigators credit the MD-83’s captain with a “timely nd appropriate” decision to reject the take-off, and the monitoring pilot’s “disciplined adherence” to standard operating procedures after the captain’s decision to abort.

While the aircraft was substantially damaged, all 110 passengers and six crew members evacuated with only one passenger receiving minor injuries.

In the wake of the accident the inquiry has recommended that Boeing complete development of a modification for MD-80s – as well as the similar 717 – to prevent a possible elevator jam from wind exposure, and establish new pre-flight procedures to enable crews to verify that no jam has occurred

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The NTSB says there is a “lack of a means” for crews to detect a jammed elevator during pre-flight checks on the type.

Really?  That surprises me.   What’s the control check consist of on this type?

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I haven't flown one of these, but the the elevator is moved by tabs....if the tabs are serviceable, moving the control column back and forth will only confirm the tabs move...the aerodynamic forces on the tabs move the elevator. So there's no way of knowing that the elevator isn't going to function until it doesn't...

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What's with the thread title??

One would have thought that with all the difficulties the MD80 series of aircraft have had with their horizontal stab/elevator system, any such problems would have been addressed decades ago.

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4 hours ago, anonymous said:

I haven't flown one of these, but the the elevator is moved by tabs....if the tabs are serviceable, moving the control column back and forth will only confirm the tabs move...the aerodynamic forces on the tabs move the elevator. So there's no way of knowing that the elevator isn't going to function until it doesn't...

I think you are correct.  And activating the Elevator Trim will move the entire stab, but this is probably not part of a pre-flight control check, am I right?

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2 hours ago, Moon The Loon said:

What's with the thread title??

One would have thought that with all the difficulties the MD80 series of aircraft have had with their horizontal stab/elevator system, any such problems would have been addressed decades ago.

Title corrected.

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The DC-9 was the same design. On a windy day, one could see the elevators finding their own position, independently, depending upon the wind. As described, the CC just moves the tabs, but IIRC, a full check fore-and-aft moved the elevators a bit as the CC neared the stops. They would rapidly 'trail' once the takeoff roll had begun, (recall watching them while in the line-up).

Edited by Don Hudson

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1 hour ago, Canoehead said:

The Youtube video is great.  The DC9 is still one of my favourites... wish I could've flown it.  A bit of thread drift... sorry Malcom.

Interesting DC9/MD80/MD90 Info

Simple Elevator Design Description (with pictures)

https://youtu.be/7R0CViDUBFs

 

No pride of ownership here, good to see an aviation topic.  More please

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