When aborting past V1 is the right thing to do

[Will]

The aircraft was damaged in a way that couldn't become apparent until the crew attempted flight. Then after VR, the aircraft wouldn't rotate. The captain aborted the takeoff well past V1 and the aircraft overran the runway. Yet had he insisted on continuing the takeoff, the results could have been catastrophic. As it was, there were no serious injuries.

In the case of this attempted takeoff, it was not until after the airplane had exceeded V1 that the captain discovered that the airplane would not rotate in response to his control inputs. When the check airman called "rotate," the captain pulled back on the control column, observed that the airplane did not respond in pitch, then added more back pressure until the control column came "further back than for a normal rotation," but the airplane still did not respond. The captain called for the rejected takeoff, and the flight crewmembers applied maximum braking, but the airplane went off the end of the runway. [...] The NTSB concludes that the airplane's lack of rotational response to the control column input during the accident takeoff did not become apparent to the captain in time for him to have stopped the airplane on the runway. Rarely could all of the safeguards in place to ensure an airplane is airworthy before departure (such as proper aircraft maintenance, preflight inspections, and control checks) fail to detect that an airplane was incapable of flight, as occurred with the jammed elevator on the accident airplane. Perhaps even more remarkable was that a flight crew would be placed in a situation in which the airplane's inability to fly would not be discoverable until after it had accelerated past V1 during a takeoff roll. The captain had extensive flight experience with many takeoffs, but none of them presented a scenario like the one he faced during the accident takeoff. Although the captain was relatively new to flying the Boeing MD-83, because of his prior NTSB Aircraft Accident Report experience in the Boeing DC-9 (a variant with an identical elevator system and controls), he correctly assessed the state of the accident airplane and quickly called for and initiated the rejected takeoff. Thus, the NTSB concludes that, once the airplane's inability to rotate became apparent, the captain's decision to reject the takeoff was both quick and appropriate.

https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR1901.pdf
https://en.wikipedia.org/wiki/Ameristar_Charters_Flight_9363

[Hardy Heinlin]

So on their flight deck there's just a position indicator for the left elevator? Or no elevator position indicator at all?

[Will]

(Not an MD-80 expert) My understanding is that there is no cockpit indication of elevator position. In addition, the control column moves the elevator tabs (not the elevators), so with a stuck elevator, the controls would still move the tabs as normal. This means the control checks in this aircraft would have felt normal, i.e. full travel, no resistance. The tabs were moving... but the R elevator didn't move in response to the change in position of the tab.

[Jeroen Hoppenbrouwers]

A design that is pretty much impossible to check without flying it. Very reliable, but IF...

[Martin Baker]

I flew on those things a handful of times in the States in the 90s. Was always relieved to get off alive!

[Will]

This story struck me because of the airmanship involved. You had a captain, in the presence of a check airman, make a call in literally just a second or two that prevented disaster... and yet was a call that deviated from all the rote learning he had been given from the first day he flew a jet. You always continue after V1, and you never practice aborting when 20 knots over V1, and there isn't any simulator training for stuck elevator on rotation.

But if that weren't enough, he was in the presence of a check airman, who was grading his performance on that very flight! This would be the flight where you'd think he'd be most likely to stick to the training, to hold the yoke back, and try to fly, because you always continue after V1, and you never practice aborting when 20 knots over V1... and if he aborted after V1, everyone in the company was going to know about it.

Turns out, the late abort was the right call. Aborting and standing on the brakes made the difference between going off the end of the runway at 25 kts and going off the runway at 200 knots, and maybe hurting or killing dozens of people.

Every now and then you really want a fully functional human being in the cockpit, someone who can react properly to unforeseen circumstances.

[Martin Baker]

Presumably a more fundamental logic kicks in at this point: continue as trained and die for sure, or...

[Britjet]

MB,
I think your namesake would probably have a better solution ;-)
Peter

[Martin Baker]

:-) and a great way of dealing with unruly passengers...

[IefCooreman]

Presumably a more fundamental logic kicks in at this point: continue as trained and die for sure, or...

On the "modern" Boeing (73 and beyond) jets the "die for sure" sounds pretty doomsday :-).

If we would notice problems like these we would use the pitch trim to rotate. It is "old school" to think technical failure. There has been a recent A300 "beyond V1 reject" here in Brussels, it turns out they simply misread the trim indicator and had the wrong trim in.

Even with a fully blocked/failed elevator system, the idea "primary controls" and "secondary controls" is still valid and as long as the aircraft is accelerating, you are only gaining energy. Use of secondary controls (pitch trim) should get you airborne.

It is true that modern day jets on big airports are frequently not field length limited but the idea of rejecting passed V1 is very a dangerous thing to train. It only takes fear and ego to reject and end up in a field with unknown outcome, than to give a few burst of pitch up trim and go fly with basically slow but full pitch control available.

[Will]

If we would notice problems like these we would use the pitch trim to rotate.

This wasn't the case of a merely stuck elevator; the elevator was locked over-center in the full nose-down position. Can stabilizer trim overcome that?

[Avi]

This wasn't the case of a merely stuck elevator; the elevator was locked over-center in the full nose-down position. Can stabilizer trim overcome that?

As far as I know, not only it can't, it shouldn't.

A full elevator should "win" a full stab at the opposite position at any time.

Cheers,

[IefCooreman]

If we would notice problems like these we would use the pitch trim to rotate.

This wasn't the case of a merely stuck elevator; the elevator was locked over-center in the full nose-down position. Can stabilizer trim overcome that?

It's an interesting question and to be honest, I would love to try it in a simulator. But I would guess it will fly as at low speeds the elevator is less effective than the stabilizer (elevator is small, it needs high speeds to become effective, stab trim is the full horizontal tailplane). That's also why I'm referring to Boeing, I'm not familiar with the MD-80.

On a Boeing there would be indications preflight that there is a blocked elevator as the yoke would simply not move. There is also an override feature that allows movement, but the "breakout force" is really high. So the problem would be clearly identifiable before the flight.

If the blockage would occur in a neutral position (ie ice buildup during taxi), the stabilizer has plenty of authority to overcome a blocked elevator. You even need to be very carefull as it reacts slow. Put in some bursts and wait, the nose will rise.

Can an elevator override a fully blocked trim? This is the whole MCAS issue on the 737 although this problem is known for years and years on the 737. The elevator is less effictive than the horizontal stabilizer and this has lead to numerous crashes.

The first one is the Sabena flight 548. This is a crash in approach phase, hence slow speed. Although officially never really determined with full certainty, the general concencus is that they had a trim up runaway. The only option they had was to bank and end up in a continous turn untill they stalled out of the sky. The crash has lead to the creation of memory items and stab trim cutout switches, because the stabilizer movement needs to be stopped as quickly as possible or you risk losing controllability.

Another slow speed example is Turkish 1951 in Amsterdam, where the autopilot trimmed up all the way while slowing down, and full TOGA thrust and pushing down on the yoke, the nose would not descend and they stalled. Boeing changed procedures and emphasied the trim down if required to put the nose down, and wait with engine power until it is accertained the nose is coming down.

The MCAS crashes are high speed examples, where the elevator will probably be able to counter full trim deflections, but I'm not sure if I would could call it controllable (if believe mentourpilot has a demo video on youtube showing elevator input required with full stab deflection inflight - very interesting and I challenge any pilot to land in such situation. So you need to move the trim again or you are doomed). The stab trim runaway memory items are designed to stop the movement immediatly. The problem now is that - because the stabilizer is so big - you might not be able to trim manual due to high airloads and this is what surprised the Ethiopian pilots who crashed in the second MCAS accident. That's when the infamous "rollercoaster" should be used, where you pitch up with elevator to take the speed out (hence reduce airloads on the horizontal stabilizer) and then bring the trim back manual. If not, you end up flying like Mentourpilot in his video.

Anyway, all this to explain I wouldn't really push the panic button on a Boeing and reject... ;-)

[United744]

Stopping > V1 when the aircraft is clearly not going to fly? Hell yes that's the right decision!

he was in the presence of a check airman, who was grading his performance on that very flight! This would be the flight where you'd think he'd be most likely to stick to the training, to hold the yoke back, and try to fly, because you always continue after V1

...and that right there is the most dangerous mindset to have. Procedures are a good thing, but never, ever, leave your brain, critical thinking/analysis, or problem solving skills at the door. NEVER!

Expect the unexpected!!! Regardless of procedures!!!

I've witnessed V1 brief being "continue after V1 unless structural failure is suspected or the aircraft doesn't want to fly". You don't have many options in the latter case.

[Will]

Adding an additional thought to this old thread... I was perusing training documents from Boeing tonight, and I found this: "Rejecting the takeoff after V1 is not recommended unless the captain judges the airplane incapable of flight."

Note that this advice from Boeing is perfectly applicable to the scenario in this original post: the captain indeed judged the aircraft incapable of flight, and properly rejected the takeoff after V1.

I mention this because this sentence from Boeing might be uttered once in flight training, but what gets mentioned 1000 times, is that V1 means continue the takeoff. In a way, it's understandable, because most V1 incidents encountered in training are engine failures. Pilots train 1000 times for the failure of the most critical engine at V1, and they train very little (or maybe even never?) for discovering that the aircraft is un-airworthy at V1.

This was really great airmanship.

[United_744]

Adding an additional thought to this old thread... I was perusing training documents from Boeing tonight, and I found this: "Rejecting the takeoff after V1 is not recommended unless the captain judges the airplane incapable of flight."

Note that this advice from Boeing is perfectly applicable to the scenario in this original post: the captain indeed judged the aircraft incapable of flight, and properly rejected the takeoff after V1.

I mention this because this sentence from Boeing might be uttered once in flight training, but what gets mentioned 1000 times, is that V1 means continue the takeoff. In a way, it's understandable, because most V1 incidents encountered in training are engine failures. Pilots train 1000 times for the failure of the most critical engine at V1, and they train very little (or maybe even never?) for discovering that the aircraft is un-airworthy at V1.

This was really great airmanship.

Agreed. I was going to write exactly this - that the aircraft is "incapable of flight", and so an abort is the ONLY option.