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Vr is the rotate speed, at which time the nose wheel can be pulled off the ground.
(V1 is the go-no-go speed. If an engine fails below V1, you abort the take-off. If it fails after V1, you continue to V2 and take-off)
V2 is the safety take-off speed, which is the speed where the airplane can become airborne if one engine fails after V1.
You accelerate to V2+10 and raise the gear, then accelerate to climb speed as the flaps are raised. In this case he normally would not go below V2+10 because it's getting too close to stall speed. He probably would be climbing at V2+10-20 with flaps at take-off setting until reaching around 1,000 feet, at which time he would begin accelerating and raise the flaps.
When we used to take-off from Danang and Saigon airports in our Pan Am 707 and 747s, we used a high rate of climb, but we didn't allow our airspeed close to the stall speed. We still accelerated. It was worse at Danang because the Viet Cong were on the hills near the airport and could hit the airport with pin point accuracy, and did. They were mostly targeting the airport, and we were trying to avoid small arms fire. However, the situation in Bagram could be very different, where they may have had to avoid SAM's, so the climb out instructions for pilots could be different.
In the video, it appears as if they only got one or two hundred feet up in the air. Stop the video just before the plane hits the ground and you can see that the nose gear is still extended. Of course I can't tell if it had started up or not. I also can't tell if I see the main gear, or if that is the engines.
The airplane probably lifted off at about time zero on the video. At 8 seconds the left wing starts to dip; at 12 seconds he begins a recovery and the left wing is raising up; at 14 seconds it goes to a right wing low position and continues to vertical; it appears to reach the highest altitude at 16 seconds, and strikes the ground 7 seconds later at 23 seconds.
I don't have any conclusions from that information, except that it was a very short period of time, the airplane definitely appeared to stall, and it also appeared as if the pilot was attempting a recovery from that stall.
I would think that the nose gear would be up by that time, or at least partially up. He would have called for gear up a few seconds after safely airborne. Could that indicate a possible catastrophic hydraulic or electronic failure? Possibly. It could also indicate compound failures. (More than one failure at the same time.) There are just so many variables, that it is difficult to determine what happened from viewing the video. Hopefully, they will find out the cause and we'll learn what happened.
If the aircraft was at an air speed in excess of V2, would it not be reasonable to speculate that engine failure was not the cause of the stall & crash (unless the pilot got distracted and allowed the nose to pitch up)? I agree that leaving the gear down may indicate other problems (unless they were just trying to cool it). Would trim runaway be a possible factor on this aircraft?
If the aircraft was at an air speed in excess of V2, would it not be reasonable to speculate that engine failure was not the cause of the stall & crash (unless the pilot got distracted and allowed the nose to pitch up)? I agree that leaving the gear down may indicate other problems (unless they were just trying to cool it). Would trim runaway be a possible factor on this aircraft?
If one engine fails, there will be a loss of airspeed, so it's entirely possible to loose sufficient speed to get to stall speed. It all depends on what his airspeed was at the time, and that is an unknown.
The aircraft veered to the left, so IF an engine failed, it was either number 1 or number 2 on the left side. The immediate pilot reaction, if an engine failed with the aircraft in that situation, would be to push the nose forward to gain airspeed to compensate for the loss of airspeed caused by the engine failure, and simultaneously apply right rudder to keep the airplane on its heading. At that slow speed, it would take more than the normal amount of rudder, and that would create some drag which would also cause a little airspeed loss.
When an airplane stalls going straight ahead, without any rudder being applied, it will stall with the wings level. That didn't happen here. The airplane first veered to the left, for some reason. Then it went hard to the right, to around a 90 degree position after it stalled. That probably indicates that something happened to make the airplane veer left, and the pilot made a correction by applying right rudder at the moment it stalled, and possibly over corrected, which caused the drastic right wing down during the stall.
I want to clarify that I am not implying pilot error when I say "possibly over corrected." Whatever occurred in the airplane must have justified the correction. And we must be open to the fact that there could have been a control system malfunction, either electrical or hydraulic, or both.
It may have required a lot of rudder, at that slow speed, to stop the veering to the left, and then as the airplane stalled, the right rudder took effect, and as we saw in the video, the pilot again applied left rudder and actually got the airplane level before it hit the ground. Whatever happened in that airplane, it appeared to me that they were fighting to get it under control, but just didn't have the altitude to fully recover from the stall.
Trim runaway could be one of many possible factors. However, trim runaway is noticeable right away, and both pilots would immediately grab the trim wheel to manually stop it, and the pilot flying would have simultaneously made a nose down correction at the same time. While trim runaway is a possible factor, I would put it low on the list.
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My apologies for calling that tank an *Abraham* ...
I do remember an accident in Europe a long time ago that was definitely load shift.
Happened in the early 80's, and I remember vividly because the pallet latches/locks were *ours*.
Those of you who produce stuff used on any aircraft, know that if something breaks, whether your fault or not, you are called in for some nasty investigations.
Plane never got off the ground, that time.
From what we gathered during the questioning, the pilot took off and then slowed down, because he thought something was *not right* (the load shifted backwards). Then he slows down and the plane feels *right again* ... So he speeds up again and the whole load came out the back of the plane ... literally !
I can understand if there was something like an Abram tank somewhere correctly placed, but then shifted to the rear, would have been able to be cause for what did happen moments later !
How does one go about loading an Abraham/Abrams whatever tank in a 747? To my knowledge, albeit limited, a 747 doesn't have a rear cargo ramp and certainly not one with a shallow incline conducive to loading wheeled vehicles. I know the 747-700f can be configured with a lifting nose section but it doesn't look nearly large enough to drive a tank through. To my knowledge, not as limited, the Army uses C-17 Globemasters, C-141 Starlifters and the mammoth C-5 Galaxies, which all have aft ramps (and forward in the case of the C-5) and very low to the ground profiles, so it seems to me rather unlikely that a 747-400 was being used to load any armored vehicles. But then again, all of my experiences are with helicopters and C-130's.
If one engine fails, there will be a loss of airspeed, so it's entirely possible to loose sufficient speed to get to stall speed. It all depends on what his airspeed was at the time, and that is an unknown.
The aircraft veered to the left, so IF an engine failed, it was either number 1 or number 2 on the left side. The immediate pilot reaction, if an engine failed with the aircraft in that situation, would be to push the nose forward to gain airspeed to compensate for the loss of airspeed caused by the engine failure, and simultaneously apply right rudder to keep the airplane on its heading. At that slow speed, it would take more than the normal amount of rudder, and that would create some drag which would also cause a little airspeed loss.
When an airplane stalls going straight ahead, without any rudder being applied, it will stall with the wings level. That didn't happen here. The airplane first veered to the left, for some reason. Then it went hard to the right, to around a 90 degree position after it stalled. That probably indicates that something happened to make the airplane veer left, and the pilot made a correction by applying right rudder at the moment it stalled, and possibly over corrected, which caused the drastic right wing down during the stall.
I want to clarify that I am not implying pilot error when I say "possibly over corrected." Whatever occurred in the airplane must have justified the correction. And we must be open to the fact that there could have been a control system malfunction, either electrical or hydraulic, or both.
It may have required a lot of rudder, at that slow speed, to stop the veering to the left, and then as the airplane stalled, the right rudder took effect, and as we saw in the video, the pilot again applied left rudder and actually got the airplane level before it hit the ground. Whatever happened in that airplane, it appeared to me that they were fighting to get it under control, but just didn't have the altitude to fully recover from the stall.
Trim runaway could be one of many possible factors. However, trim runaway is noticeable right away, and both pilots would immediately grab the trim wheel to manually stop it, and the pilot flying would have simultaneously made a nose down correction at the same time. While trim runaway is a possible factor, I would put it low on the list.
At this point in time (I have no more information than anyone else), I'm giving the benefit of the doubt to the flying pilot and assuming that the airplane was maintaining a speed of V2 + X, and IF engine 1 and/or 2 failed that he/she would have maintained a speed > Vmca. In other words, I'm choosing to believe that they could have recovered from an engine failure in that phase of flight (multiple engine failures might be a different story). Of course there is also the possibility of some type of system failure, but we don't have that information yet. I think that this is why some of the posters in this thread (myself included) are speculating that load shift was the culprit.
At this point in time (I have no more information than anyone else), I'm giving the benefit of the doubt to the flying pilot and assuming that the airplane was maintaining a speed of V2 + X, and IF engine 1 and/or 2 failed that he/she would have maintained a speed > Vmca. In other words, I'm choosing to believe that they could have recovered from an engine failure in that phase of flight (multiple engine failures might be a different story). Of course there is also the possibility of some type of system failure, but we don't have that information yet. I think that this is why some of the posters in this thread (myself included) are speculating that load shift was the culprit.
It's been many years since I've even thought of Vmca because it was not a speed that we used as a reference in flight-operation. We would use V1, Vr, V2, and a speed such as V2+x as references.
However, Vmca does assume that the gear is up, and in this case the nose gear appeared to be down. Also, at maximum weight, the Vmca may be less than the stall speed. If the wind was gusty at all, that could change the airspeed very quickly and cause the airspeed to go below stall speed. So, for discussion purposes, I'll just use the term above stall speed.
Certainly load shift is one of the many possibilities, and I wouldn't rule that out at this time.
My question would be, however, why did it take 8 seconds for the load to shift, because the 747 body has a very steep angle, even in normal climb, and this was a high pitch attitude climb. I experienced a load shift, and it's effect was immediate. There was no delay.
I had a load break loose on a cargo C-46, and it broke loose right after take-off, just about the time the co-pilot, who was flying the leg, called for gear up. It created a fairly violent porpoising, and as I took over the controls, I had to keep a lot of forward pressure on the yoke, keep full power, and went skimming over the tree tops at the end of the runway. Fortunately, I had enough elevator control that with full power I was able to keep it flying, but with very little altitude gain.
We suspected the load broke loose, so the co-pilot ran back immediately, and was was able to move the load enough for us to fly normally. That's the short version of the story.
...(V1 is the go-no-go speed. If an engine fails below V1, you abort the take-off. If it fails after V1, you continue to V2 and take-off)
V2 is the safety take-off speed, which is the speed where the airplane can become airborne if one engine fails after V1...
The information above is incorrect. Haven't flown the 747, but have spent thousands of hours in regional jets. When the pilots are flying the aircraft on the takeoff roll (when we start moving) we have a set number of call outs that are made, these typically include. (PF=Pilot Flying) , (PNF=Pilot Not Flying)
PF: Set Thrust
PNF: Thrust Set
PNF: 80 Knots (Can vary depending on Aircraft)
PNF: V1 (Go/No-Go speed)
PNF: Rotate (VR, rotation speed...after this, you're flying)
**Engine Fails**
PNF: Engine Failure
PF: Set Max Thrust (PF will lower the nose to attain V2 speed, which is used for engine out climbs)
PNF: Positive Climb (We've left the ground and it's registered on the instruments, namely Vertical Speed Indicator)
PF: Gear Up (Don't need that thing anymore, she's flying and there's no where near enough runway left to land on again)
PNF: Acceleration Height (Altitude ~400 ft above field elevation at which point obstacles are cleared and an aircraft with an engine out can accelerate to a more normal flying speed)
PNF: VFS (Aircraft has reached flap safety speed, at this point, continue to climb and retract remaining flaps, then begin notifying ATC of any failures, or intentions)
Originally Posted by Captain Bill ...(V1 is the go-no-go speed. If an engine fails below V1, you abort the take-off. If it fails after V1, you continue to V2 and take-off)
V2 is the safety take-off speed, which is the speed where the airplane can become airborne if one engine fails after V1...
Quote:
Originally Posted by flynavyj
The information above is incorrect. Haven't flown the 747, but have spent thousands of hours in regional jets.
Perhaps it's how I phrased it that caused you to say my information is incorrect. So allow me to be very specific.
V2 is the take-off safety speed, and the climb out speed for an engine failure.
Below is the procedure from my Airbus A310 Operating Manual (from 1991). I don't have my 747 manual any longer, but the procedures are all basically the same.
"If the engine failure occurs below Vr, keep the nose wheel firmly on the runway to aid in directional control. Rotate at Vr at a rate that will attain V2 at 35 ft above the ground."
Then we to climb to 600 feet, or the obstacle clearance altitude, whichever is higher, then begin to accelerate and raise the flaps.
Now, as applies to the Bagram 747:
V2+10 was possibly the target climb-out speed for the 747 at Bagram because V2+10 with flaps at take-off gives the maximum climb rate, in the shortest distance, and is the speed that we would normally use to make a maximum rate climb out. (However, the aircraft climb angle was restricted to 18 degrees pitch up.)
I'm still concerned that I saw the nose gear appearing to be fully extended when the airplane hit the ground. I believe it should have been fully retracted by that time, which raises the question of whether there was a catastrophic hydraulic, and or electrical failure, although it did appear that the pilot got the airplane to a level position before hitting the ground, which seemed to indicate that he had control of the flight controls.
I'm still concerned that I saw the nose gear appearing to be fully extended when the airplane hit the ground. I believe it should have been fully retracted by that time...
The gear were down.
Quote:
which raises the question of whether there was a catastrophic hydraulic, and or electrical failure, although it did appear that the pilot got the airplane to a level position before hitting the ground, which seemed to indicate that he had control of the flight controls.
Or... the poor soul was hoping that he could maybe land the damed thing?
Correct me if I am wrong but did folks say higher up in the thread that this should be a wait and see kind of thing... you know wait until some facts were known lest folks begin to sound like the usual suspects the networks drag into the studio to pontificate upon their expertise which is usually ended with a big "we don't know." Pretty much canceling out everything that they had just said for the last 15 minutes of their fame?
There are only two "facts" that are known, the crew radioed that cargo had come lose, that the plane was carrying a number of yet to be identified vehicles and other equipment, the plane stalled and crashed with all souls. So, I guess I will keep checking back when some real facts show up on the thread... whenever that may be.
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