DHL 757 in the dirt in San Jose, Costa Rica

That Duke video... LMAO!


dtuuri said:
Vmcg? On a landing aircraft? But I get the larger point.
Click to expand...

Yes, but not in a normal use of the term I know. On takeoff with an eng-out occurring a low speed, say 60 kts, it becomes very difficult to control even with the rudder fully displaced, until the good engine is brought to idle of course. Adding or just holding a touch of tiller will prevent the nose wheel from making that small turn at low speed. I don’t know the exact speed, or if there’s even a vmcg published, but this is the vmcg tendency that I see normally with a low speed cut.
Based my understanding of what we’re assuming about this airplane’s condition, it seems possible that they experienced a similar tendency. If they were using full reverse on only the right side in an attempt to stop on the remaining pavement there would definitely be an asymmetrical pull. Normally not a big deal, even on one engine, but without any nose wheel steering? Once rudder authority is lost due to low airspeed it’s going to torque right at some point during the deceleration. I’m calling it “vmcg of the day” for this crew.
 
Last edited:
benyflyguy said:
Everytime I hear about a duke or see one I can’t help but watch this vid
Click to expand...

I thought this video was lost, discarded in the internet landfill. It's a classic, and damn funny.

:D
 
When I see a mention of Vmcg, it reminds me of Air Transport International Flight 782. The DC-8 crashed on February 16, 1995, while attempting a second try at a night three engine takeoff at Kansas City International (KMCI). The crew had agreed to ferry the aircraft to a maintenance base after Engine #1 failed to start for another crew earlier in the day.

The Captain and First Officer had no experience performing a three engine takeoff. On the first try, they nearly lost control and aborted the attempt. After a discussion, they decided to try again. The aircraft began to veer off the runway while approaching VR, and the Captain prematurely raised the nose. After a long tailstrike, the aircraft left the ground, but stalled and crashed. The three crew members perished.

This was the first major accident I had heard of that was caused by loss of control involving Vmcg. Maintaining directional control while manipulating three throttles of a four engine transport category aircraft, managing rudder input, and depending on runway edge lights for guidance must have been extremely challenging.

https://aviation-safety.net/database/record.php?id=19950216-0

https://en.m.wikipedia.org/wiki/Air_Transport_International_Flight_782
 
Last edited:
3393RP said:
This was the first major accident I had heard of that was caused by loss of control involving Vmcg. Maintaining directional control while manipulating three throttles of a four engine transport category aircraft, managing rudder input, and depending on runway edge lights for guidance must have been extremely challenging.
Click to expand...
They did it wrong, which made it much more difficult than it should have been. As the NTSB determined, their training in three-engine takeoffs was inadequate and fatigue likely played a factor, too.

The correct procedure is to accelerate with only symmetrical thrust, until above Vmcg, then smoothly advance the asymmetric engine as the flight controls (rudder) are adjusted to compensate for the increasingly asymmetric thrust. On the second takeoff attempt, they did just the opposite. They increased the asymmetric thrust sooner instead of delaying it longer.

Asymmetric reverse thrust is much less of an issue in the airplanes that I've flown. I did a landing with only one reverser earlier this week in the 737 and you hardly notice the turning tendency from it. I don't remember if I ever did a landing in the 757 with only one reverser. Probably not, as I didn't fly it for long.
 
Larry in TN said:
They did it wrong, which made it much more difficult than it should have been. As the NTSB determined, their training in three-engine takeoffs was inadequate and fatigue likely played a factor, too.

The correct procedure is to accelerate with only symmetrical thrust, until above Vmcg, then smoothly advance the asymmetric engine as the flight controls (rudder) are adjusted to compensate for the increasingly asymmetric thrust. On the second takeoff attempt, they did just the opposite. They increased the asymmetric thrust sooner instead of delaying it longer.

Asymmetric reverse thrust is much less of an issue in the airplanes that I've flown. I did a landing with only one reverser earlier this week in the 737 and you hardly notice the turning tendency from it. I don't remember if I ever did a landing in the 757 with only one reverser. Probably not, as I didn't fly it for long.
Click to expand...

Thanks for the comment. Now I recall that the Captain prematurely throttled up #4. The crew was tasked with the flight shortly after their leg of an overseas flight terminated at MCI if I remember correctly. They still had flight time remaining, and agreed to reposition the DC-8. As you mentioned, fatigue must have been part of the accident chain.
 
Last edited:
3393RP said:
Now I recall that the Captain prematurely throttled up #4.
Click to expand...
It was the FE not the captain. From the accident report:

During this post-rejected takeoff taxi, the flight engineer suggested, “if you want to try it again I can try addin the power if you like.” The captain quickly responded, “okay let’s do it that way yeah....” This was a procedure that the flightcrew created themselves and was patently incorrect. The operating manual clearly states that the captain should control the throttles. This decision to allow someone else to do so was not challenged or even discussed by the flightcrew. Investigators who experimented with this takeoff procedure in the simulator found it extremely awkward and somewhat disconcerting. The Safety Board believes that allowing someone not even in nominal control of the airplane to apply the asymmetric power required the captain to constantly react to an unknown quantity of thrust and an unknown rate of thrust application during the accident takeoff roll. This increased his mental workload dramatically and probably contributed directly to the accident.
​
That would be like saying, "Hey, why don't you work the right rudder pedal, I'll work the left one."
 
My brother was a mechanic for ATI when that accident happened, and was trying to get home to BDL from somewhere in the MCI area. If he had known that flight was heading to CEF, he would have tried to get on it to get home.
 
Larry in TN said:
They did it wrong, which made it much more difficult than it should have been. As the NTSB determined, their training in three-engine takeoffs was inadequate and fatigue likely played a factor, too.

The correct procedure is to accelerate with only symmetrical thrust, until above Vmcg, then smoothly advance the asymmetric engine as the flight controls (rudder) are adjusted to compensate for the increasingly asymmetric thrust. On the second takeoff attempt, they did just the opposite. They increased the asymmetric thrust sooner instead of delaying it longer.

Asymmetric reverse thrust is much less of an issue in the airplanes that I've flown. I did a landing with only one reverser earlier this week in the 737 and you hardly notice the turning tendency from it. I don't remember if I ever did a landing in the 757 with only one reverser. Probably not, as I didn't fly it for long.
Click to expand...
Why did you only use one? Is that a routine thing to do?
 
Groundpounder said:
My brother was a mechanic for ATI when that accident happened, and was trying to get home to BDL from somewhere in the MCI area. If he had known that flight was heading to CEF, he would have tried to get on it to get home.
Click to expand...
I don't think anyone other than the minimum flight crew would have been allowed on the flight. A mechanic would only be allowed if a mechanic was required for a test flight, which this wasn't.

luvflyin said:
Why did you only use one? Is that a routine thing to do?
Click to expand...
The left thrust reverser was inoperative and deferred under the MEL.
 
dtuuri said:
It was the FE not the captain. From the accident report:

During this post-rejected takeoff taxi, the flight engineer suggested, “if you want to try it again I can try addin the power if you like.” The captain quickly responded, “okay let’s do it that way yeah....” This was a procedure that the flightcrew created themselves and was patently incorrect. The operating manual clearly states that the captain should control the throttles. This decision to allow someone else to do so was not challenged or even discussed by the flightcrew. Investigators who experimented with this takeoff procedure in the simulator found it extremely awkward and somewhat disconcerting. The Safety Board believes that allowing someone not even in nominal control of the airplane to apply the asymmetric power required the captain to constantly react to an unknown quantity of thrust and an unknown rate of thrust application during the accident takeoff roll. This increased his mental workload dramatically and probably contributed directly to the accident.
​
That would be like saying, "Hey, why don't you work the right rudder pedal, I'll work the left one."
Click to expand...

I can see I need to reread the NTSB report. It's been years since I did so, and details like those you provided escaped my memory.

Thanks.
 
3393RP said:
I can see I need to reread the NTSB report. It's been years since I did so, and details like those you provided escaped my memory.
Click to expand...
You weren't completely "wrong", the captain DID advance the throttles on the first try. Letting the FE do it on the second try was the fatal mistake.
 
You must log in or register to reply here.
Back
Top