NTSB report on MD83 high speed abort after VR due jammed elevator
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NTSB report on MD83 high speed abort after VR due jammed elevator
Firstly, well done to the crew, the capt in particular for making a hard decision that goes against everything drummed into us and listening to that little voice.
Secondly well done to the investigators for specifically mentioning that the capt made the correct decision under the circumstances. It is often easy to draw a line between the “non compliance” (in this case the post V1 reject) and the crash, but to acknowledge that the person making the decisions had all the info and made the appropriate decision is great to see.
Interesting and challenging position for the check pilot though.
i do reckon that the 12 seconds between V1 and the captain pulling the pin and rejecting the takeoff would have been the longest 12 seconds of his life and to evaluate the situation and make a decision like that is pretty good going.
Secondly well done to the investigators for specifically mentioning that the capt made the correct decision under the circumstances. It is often easy to draw a line between the “non compliance” (in this case the post V1 reject) and the crash, but to acknowledge that the person making the decisions had all the info and made the appropriate decision is great to see.
Interesting and challenging position for the check pilot though.
i do reckon that the 12 seconds between V1 and the captain pulling the pin and rejecting the takeoff would have been the longest 12 seconds of his life and to evaluate the situation and make a decision like that is pretty good going.
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Nothing non-compliant about a post-V1 abort for an unflyable aircraft! Of course, if you've put the aircraft into that state yourself, as in the Air NZ 777 at Narita (autopilot engaged prior to commencing the takeoff roll), there are bigger questions at play (in that case, autoflight system design and crew type conversion training).
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Well executed, that guy had balls of steel!:-) I know I always say part of my brief is Blw V1 the usual eng fire/failure etc but control malfunction also is cause for rejection, trouble is unless it's rudder & or pedals during the T/Off run which would become obvious roll & pitch would normally not until it's too late. Makes one think this event that's for sure !
Cloud cutter - I agree with you which is why I said non compliance in inverted commas but on face value a reject after V1 is a no no, but yes you are correct the V1 is meaningless if the machine won’t fly
The 717 has a display of the elevator position, and has had so from build. I'm surprised that the NTSB didn't mention that. The control check procedures were tweaked after this accident, but even before, a jammed elevator would in all likelihood have been picked up.
I know nothing about the 717 but on a -9/80 series how would they know? You can move the yoke all you want but you're just checking the control tabs, not the elevators. Even the NTSB said as much - "Contributing to the accident were (2) the lack of a means to enable the flight crew to detect a jammed elevator during preflight checks for the Boeing MD-83 airplane."
...on a -9/80 series how would they know? You can move the yoke all you want but you're just checking the control tabs, not the elevators. Even the NTSB said as much - "Contributing to the accident were (2) the lack of a means to enable the flight crew to detect a jammed elevator during preflight checks for the Boeing MD-83 airplane."
Yep...they shoulda thought of that decades ago. A bit late now.
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And the PAX on the flight ended up doing well, too. This flight was a charter taking the University of Michigan basketball team to their conference (Big 10) tournament being held in Washington, DC. After evacuating, the team had to take another flight the next day to Washington, arriving just before their first game that afternoon and without their equipment (which was still in the bashed up belly of the accident plane). Even though Michigan was only expected to be a middling team at the tournament, they ended up winning the whole thing.
On the DC-9 and MD-80 the wires, pulleys and bellcranks don't move the actual elevators. They move the control tabs and air flow across the control tabs generates a force that moves the elevators. That's why it's common to see one elevator up and one elevator down on a parked aircraft. And even if you had someone looking aft from the main door and they could see the left elevator control tab the problem was the right elevator had been damaged by high winds while the aircraft was parked. The right elevator control tab was not able to generate enough force to over come the damage.
I haven't been flown a -9 in 23 years, don't think I'll see one anytime soon. There's a hydraulic assist to lower the nose so full stick forward will drive the elevator nose down if the accumulator is charged but pulling up just moves the tabs, not the elevator.
What you're remembering is the Elevator Augmenter. It uses left hyd system pressure to push both elevators full nose down if/when the elevator control tabs are moved 10 degrees AND in relation to elevator surface by action of the control columns. The Elevator Power On light merely indicates that hyd pressure was applied to the system (it also has it's own accumulator).
The flight control check performed as part of the taxi checklist wouldn't have any way of showing what the actual control surface position is...because the actual controls surfaces don't move...only tabs move at that point. You are told to look for the Elevator Power ON light but this still doesn't indicate where the elevators went when the augmenter was supposed to move them nose down...just that hyd press was applied.
The flight control check performed as part of the taxi checklist wouldn't have any way of showing what the actual control surface position is...because the actual controls surfaces don't move...
Get out on the stairs and tell your effo to push and pull to the stops. I bet you'll see the elevators moving. There must be some sort of followup from the control tab circuit that moves the elevator.
Last edited by Capn Bloggs; 21st Mar 2019 at 07:37.
I'm always happy to stand corrected. Despite a rather embarrassing amount of exposure to the -9/-80 series, there will always be something I don't know. I'd never heard of such a follow-up on the elevator control mechanism. Just in the interest of intellectual curiosity, would you happen to have a schematic or diagram you can post showing that elevator follow-up mechanism ?
As a further variation on a theme, if the augmenter were removed from the equation (deplete the accumulator, I guess), would pushing the control column full nose down also move the elevators down via such a follow-up ?
POMs have always been rather sparse in such details but time and happenstance will always offer a time when knowing such fine points might have been valuable.
I said "must be". I don't know why, or whether in fact there is. All I know is the control columns move the elevators (eventually). I've seen it for myself in the last couple of days by looking at the elevators (one with a stiff tailwind), and every time we do a control check prior to takeoff on the cockpit elevator display. Turn the EPAS off and I suspect the elevators would still move down.
In this accident, I have no doubt, assuming all these tails are the same, that pulling full backstick before startup would have had the left elevator responding and the right not (because it was jammed).
In any case, it'll be interesting to see how Boeing and the FAA respond to the NTSB's recommendations.
In this accident, I have no doubt, assuming all these tails are the same, that pulling full backstick before startup would have had the left elevator responding and the right not (because it was jammed).
In any case, it'll be interesting to see how Boeing and the FAA respond to the NTSB's recommendations.
