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Old 12th Oct 2017, 15:24   #1 (permalink)
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Vodka burner - where was V1?

https://www.youtube.com/watch?v=ThoZNxy2JZk

I'm sure many of you will be familiar with the video of an Il-76 taking off from Canberra Airport, Australia and using every last inch of the runway. Video is 2:25 long. At what point in the video would the aircraft have passed V1 and been committed to taking off no matter what happened?

Last edited by Super VC-10; 12th Oct 2017 at 15:24. Reason: fix typo
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Old 12th Oct 2017, 18:09   #2 (permalink)
 
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That would assume that they did take performance calculations diligently.
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Old 16th Oct 2017, 12:42   #3 (permalink)
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Assuming the aircraft is near its maximum take-off weight for the conditions at the time (hot, little wind). Take-off begins at 0:50, airborne at 1:46. Somewhere between the two the aircraft would have reached V1. Question is, roughly where? Video apparently taken before the runway was extended.
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Old 17th Oct 2017, 01:18   #4 (permalink)
 
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Not dissimilar to this C-5.

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Old 17th Oct 2017, 01:21   #5 (permalink)
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The question, basically, is unanswerable.

In any such situation, there are too many variables at play .. unless you have some inside information either from the crew or operator. Alternatively, if you had a copy of the relevant AFM, you would be able to make some assessment yourself .. but, otherwise, it's a murky pond in which you are endeavouring to seek some enlightenment.
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Old 17th Oct 2017, 05:30   #6 (permalink)
 
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I think the answer lies in a Russian culture of there's not enough room to stop, we're going, lets get as much speed before we rotate because it makes me feel better and I was probably overweight anyway. We can see any obstacles to miss them.

At least that's my personal observation after chartering Mil8s in Russia.
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Old 17th Oct 2017, 16:03   #7 (permalink)
 
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At flying school, 70's, the ground engineer told us of his days in RAF and some experimental flying in, I think, a Victor. This was before the use of computers, RTOW tables etc. There was a structural weight calc and 'finger in the wind' takeoff roll calculation. The bosses wondered just what this beast could do for MTOW. They found a runway with only the sea beyond, the a/c had radio contact with ops during the whole test flight, opened the taps and launched. It probably looked a little like the Russian demo. As per military runways they had distance markers down the side, and they called out their speeds as they passed them. I heard there was some puckering of lips and tightening of buttocks and they eased the rumbling groaning metal elephant off the last pebbles of tarmac and into ground/water effect. Wheels were up ASAP. Perhaps it was good job the under fuselage is so boat shaped.
The story concluded with the FE, our instructor, announcing over the radio, about 2-300yds beyond the runway end, with great jubilation & relief, "V2".

Is there not a limit on clearway? Is there not a maximum % of TORA? It's been too long ago and I can't find a quick reference.
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Old 17th Oct 2017, 23:42   #8 (permalink)
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Is there not a limit on clearway? Is there not a maximum % of TORA? It's been too long ago and I can't find a quick reference.

The general rule is that available clearway declared is limited to 50% TORA. This has been discussed in other threads previously but no-one has pinned down just where it came from back in the olden days of antiquity.

As I recall, and that might be a tad scratchy with the passage of time, the only place I have seen it written in "official" documents was in one of the FAA aerodrome ACs .. but I'll leave it to you to go searching for that detail.

From a practical point of view, I can't imagine any aircraft being able to use that percentage of TORA ... keeping in mind that, for most aircraft (ie other than ancient BCAR Types for which the factor was 1/3) that would infer an air distance to screen up to being equal to TORR ... now that would really be an aircraft relying on the curvature of the earth to fling itself (very sedately in the nature of enjoying a port in the late evening) away from the ground.
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Old 18th Oct 2017, 05:03   #9 (permalink)
 
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FAR 121.189(c)2 gives the 50% limitation.
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Old 18th Oct 2017, 07:38   #10 (permalink)
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Good man .. and (3) ties it into TOR. I have no doubt that the figure has its origin in some dark and musty ICAO or similar words .. just where .. well, we await some keen researcher's advice.
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Old 18th Oct 2017, 14:33   #11 (permalink)
 
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With that amount of dirt on the runway that C5 would have sucked up plenty in a standing high-power-start. Once you start a vortex it takes about 20kts to break it.

The risk is highest at the end of a runway where most planes have blown the dirt. I would always recommend the high-power procedure a hundred yards down the runway from the turn-on when you have that amount of dirt.
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