Ryanair uses all the runway.

[Musician]

Originally Posted by kungfu panda

I have read the definition of take off distance. Now you re-read it. It refers to Engine failure at V1.

I agree that we don't know the position on the runaway that they achieved V1 and agree that looking at the video, it's speculation that stopping would not have been possible from minimum V1. However on a dry runway V1 normally approximates Vr.If they rotated at Vr. They certainly could not have stopped from any point within the previous 500' of where they started the rotation.

I believe the aircraft started to rotate at the touchdown marker before the aiming point, that would be 480m/1600ft from the end of the runway, at a very approximate 146kt. Going back to 500' before that, i.e. to the previous touchdown marker, the plane was at approximately 141 kt. Does it seem unlikely to you that V1 and Vr differ by 5kt on a derated takeoff?

35' is basically the height where the plane enters the "takeoff flight path" that maintains 35' obstacle clearance; obviously you can't do that at a lower height. TOD is computed such that the plane can reach that height with 15% spare distance on all engines, and can reach it with one engine inoperable from V1 and Vr. Clearway is limited to half the runway length by regulation.

The more interesting definition is for TOR: FAR 121.189 or 135.379 prescribe that "(3) The takeoff run must not be greater than the length of the runway." With FAR 25.113,

If the takeoff distance includes a clearway—

(1) The takeoff run on a dry runway is the greater of—

(i) The horizontal distance along the takeoff path from the start of the takeoff to a point equidistant between the point at which VLOF is reached and the point at which the airplane is 35 feet above the takeoff surface, as determined under §25.111 for a dry runway; or

(ii) 115 percent of the horizontal distance along the takeoff path, with all engines operating, from the start of the takeoff to a point equidistant between the point at which VLOF is reached and the point at which the airplane is 35 feet above the takeoff surface, determined by a procedure consistent with §25.111.

"VLOF is the calibrated airspeed at which the airplane first becomes airborne." So basically, the aircraft must achieve 35' within the same distance past the runway end that it achieved liftoff prior to the runway end. If that distance is 600ft, as this departure probably exceeded, a 5% / 3.5° angle of ascent would suffice. So that seems within margins as well.


P.S.: There is a safety consideration, though. I found an article in an old BOING AERO issue with a nice infographic down the page that shows that a 737 usually lifts off at 7°-9° attitude, and that this should be reached 3 seconds after Vr. If you rotate more slowly, a higher liftoff speed could result, and that might lead to a tire overspeed event.

P.P.S.: Pilot Guide to Takeoff Safety (2007):

• "Roughly 15% of the RTO accidents of the past were the result of improper preflight planning."
• "The use of clearway to increase takeoff weight “unbalances the runway” and results in a lower V1 speed."

P.P.P.S.: I should probably amend my above calculations to account for the 15% margin for all-engine operation; this effectively shortens the allowable runway use by 13%, that's 260m in case of Bristol. Since the aircraft was not at 35' at the actual runway end, liftoff needed to be at least 520m (1730') prior to the runway end for the end of the takeoff run, to allow for the 15% extension and not exceed the actual runway length (TORA). I believe that this was not the case here, since I have previously figured that liftoff did not occur before the plane reached the aiming point.