Convair 340 (C-131D) ZS-BRV crash Pretoria, South Africa
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Agree, the almost full up left aileron, (left wing down) is really troubling. I remember 2-3 deg. bank towards the good engine and appropriate rudder is what we trained for on the turboprop I flew.
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Correct. There might be some cross control with the rudder full right, but surely not full left aileron. With light GA piston twins even on a single engine go around there is only a bit of aileron needed.
But there is some suggestion in the video that the RPMs of the two engines are already different. I don't know the R2800, but presume both props are selected to full-fine pitch for the take-off? So, like the R1830 (Twin Wasp) with which I used to be familiar, the RPM depends purely on the power available.
Videos, of course, are almost completely useless at representing props at running rpm. But not completely useless in this instance. Watching the video, the props appear at first to be rotating (albeit much slower than reality, but in the correct direction for a right-hand tractor) at the same speed. But, at elapsed times 8, 11 and 13 secs, the port prop seems to hesitate, whereas the starb'd does not. That is when the a/c is approaching the camera. We know from both videos, of course, that the port engine was on fire, whereas the starb'd seems okay. So I infer that the port prop was slower than the starb'd.
From about 15 secs, with the a/c going away from the camera, the port prop (as falsely represented by the video) starts to rotate much faster than the starb'd. IMO, that indicates that the prop had actually slowed down, but I wouldn't have any idea by how much. The other possibility, which seems highly unlikely, would be that the starb'd prop was being feathered and slowing down (i.e., the starb'd engine being shut down). No doubt, analysis based on the camera's frame-rate would enable someone to estimate the relative RPMs, but they are definitely asymmetric.
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Videos, of course, are almost completely useless at representing props at running rpm. But not completely useless in this instance. Watching the video, the props appear at first to be rotating (albeit much slower than reality, but in the correct direction for a right-hand tractor) at the same speed. But, at elapsed times 8, 11 and 13 secs, the port prop seems to hesitate, whereas the starb'd does not. That is when the a/c is approaching the camera. We know from both videos, of course, that the port engine was on fire, whereas the starb'd seems okay. So I infer that the port prop was slower than the starb'd.
From about 15 secs, with the a/c going away from the camera, the port prop (as falsely represented by the video) starts to rotate much faster than the starb'd. IMO, that indicates that the prop had actually slowed down, but I wouldn't have any idea by how much. The other possibility, which seems highly unlikely, would be that the starb'd prop was being feathered and slowing down (i.e., the starb'd engine being shut down). No doubt, analysis based on the camera's frame-rate would enable someone to estimate the relative RPMs, but they are definitely asymmetric.
From about 15 secs, with the a/c going away from the camera, the port prop (as falsely represented by the video) starts to rotate much faster than the starb'd. IMO, that indicates that the prop had actually slowed down, but I wouldn't have any idea by how much. The other possibility, which seems highly unlikely, would be that the starb'd prop was being feathered and slowing down (i.e., the starb'd engine being shut down). No doubt, analysis based on the camera's frame-rate would enable someone to estimate the relative RPMs, but they are definitely asymmetric.
Due to the interference a very small change of RPM (e.g. 20 RPM) will look totally different on the video. Therefore you cannot deduct anything meanigful from the perceived change in RPM in the video.
I watched a couple videos on YouTube showing Prop Airliner taking off (e.g. DC-6). The effect is exactly the same - direction and speed of the props seem to change through the T/O run.
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Other posts have pointed out the deflected aileron from the new vision looking out at the left wing. It does appear to be fully deflected up which means set for a left bank or the opposite to what would would be expected with a left engine failure. Maybe a clue to something worse going on ?
The perceived rotation of the props on the video are interferences between the acutal propeller RPM and the video frame rate. When the frame rate is exactly in sync with a full, a 1/3rd or 2/3rd revolution of the prop the blades seem to stop. So far so good. We can assume that the RPM is the same when both props seem to stop.
Due to the interference a very small change of RPM (e.g. 20 RPM) will look totally different on the video. Therefore you cannot deduct anything meanigful from the perceived change in RPM in the video.
I watched a couple videos on YouTube showing Prop Airliner taking off (e.g. DC-6). The effect is exactly the same - direction and speed of the props seem to change through the T/O run.
Due to the interference a very small change of RPM (e.g. 20 RPM) will look totally different on the video. Therefore you cannot deduct anything meanigful from the perceived change in RPM in the video.
I watched a couple videos on YouTube showing Prop Airliner taking off (e.g. DC-6). The effect is exactly the same - direction and speed of the props seem to change through the T/O run.
BTW, I gather the RPM on a R2800 at take-off is 2800 RPM at sea-level, but may be 2700 RPM at about 5000 ft. According to Janes, reduction gearing is 0.375 : 1 (3 : 8) - giving prop speeds of 1050 RPM or 1012 RPM respectively (roughly 52 or 50 blades per second).
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Maybe the left aileron upfloat is due to damage the left aileron primary control cable. (The upfloat changes from the first few seconds, of the latest video, to the 20 second mark, where upfloat is at its maximum, and stays there until impact. An NTSB report regarding a possibly similar occurrence refers. See NTSB ERA11LA117. The left aileron, with what appears to be close to maximum deflection, would make turning to the right on base challenging. With a left engine most likely producing less power in the final minute or so, manoeuvring the aircraft would be difficult. To me the engine note changes, in the video from inside the aircraft, in an attempt to keep wings close to level close to the ground.
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A post came up on Avherald comments section (publically available). Take it with a grain of salt at the moment.
Convair crash wonderboom. The inside story from my AMO who is doing the investigation is that a fuel line fractured on the carburetor avgas radial left engine. Fire then burned through the oil lines. Loss of pressure prevented them from feathering the prop. They turned right downwind to avoid crashing into built up areas. I.e. Against the live engine. They set it down on base but hit a single story steel and brick warehouse tearing chunks out and bending the i beams at right angles. Probably with an engine. This effectively broke their speed. Landed straight ahead with both wings separating and burning. All 18 pax WALKED OUT! Pilots injured but not sure how badly. Engineer in jump seat went through windscreen and died. Truly lucky for all except the engineer. Pilots were incredibly cool and pax too as reported by my AMO's friend who was on board.
Not familiar with Convair controls, but would a Fire uncontained have the potential to burn through control linkages?
It looks to me like roll was being controlled with asymmetric power till the LH finally died.
What is becoming clear is that this was a feat of good airmanship even with a sad outcome.
It looks to me like roll was being controlled with asymmetric power till the LH finally died.
What is becoming clear is that this was a feat of good airmanship even with a sad outcome.
Other posts have pointed out the deflected aileron from the new vision looking out at the left wing. It does appear to be fully deflected up which means set for a left bank or the opposite to what would would be expected with a left engine failure. Maybe a clue to something worse going on ?
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If you look at a satellite view of the ground track, and the comment posted above, the left aileron was used to turn away from a busy road and densely populated area in the last seconds of the flight. I.e. done under pilot control, no mechanical failure explanation necessary.
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The fire after shutdown is only excess old and fuel in the manifold and exhaust which is fairly normal after a cylinder head failure. The prop maybe windmilling slightly due the broken piston and probably rod thus lack of x % of cylinder friction. I have seen this before in flight with my own eyes . I suggest this is a normal radial engine failure nothing else.
Maybe the density Altitude and weight got them on the day. Swift recovery to all.
Maybe the density Altitude and weight got them on the day. Swift recovery to all.
If you look at a satellite view of the ground track, and the comment posted above, the left aileron was used to turn away from a busy road and densely populated area in the last seconds of the flight. I.e. done under pilot control, no mechanical failure explanation necessary.
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But something is awry here. #1 dead or dying, #1 prop not feathered, Power on the #2 and full down aileron on the left and it appears that it is still banked to the right until the last moments???
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The following is a theory, nothing more.... Looking at the video taken by the passenger in the cabin it appears the left hand aileron is stuck close to the full up position (it does not move at all from what I can tell). Normally if the right hand engine was producing more power the left hand aileron would be DOWN if anything. So I imagine they have put in close to full up aileron on the right hand wing to counteract. This would produce significant drag and loss of lift (think spoilers). The only thing left for roll control would be assymetric thrust. At the start of the video it sounds like there is a lot of power on the LH engine, assisting the turn to the right, trying to line up on finals runway 29. When it coughs and splutters with more flames, it loses power, then the left hand wing drops. The only way to stop it banking further left would be to reduce power on the right hand engine, and then they couldn’t maintain the height. As previously stated in the video of it after takeoff at the end of the runway there is no evidence of rudder or aileron displacement indicating the LH engine is still producing power at that time. So IF it was an aileron issue it happened further down the track- that may be the reason they never shut the LH engine down because it was the only way of controlling the machine in roll. That’s my theory anyway. Whatever the findings, it looks like these guys got dealt some really bad cards and managed the situation incredibly well, coming down close to wings level. Here’s wishing a speedy recovery to all involved. So sad.
Any aeroplane I’ve ever flown post V1 with full (or close to) aileron still rolls fairly spritely, even asymmetric.
Aileron input remained constant, yet varying roll rates and angle of bank, ending with a change in sound and seemingly power with a roll rate induced.
i respectfully disagree with you.
Aileron input remained constant, yet varying roll rates and angle of bank, ending with a change in sound and seemingly power with a roll rate induced.
i respectfully disagree with you.