dublinpilot wrote:
The 70% of Take Off speed by 1/2 way is a good judge if I will actually take off, but it’s no real indication on if my engine is performing as normal as different length runways mean that I’ll be at different speeds by 1/2 way.
I have always seen it more as a check that I will be able to get to my take off speed before the end of the runway rather than a performance test of my engine. .
I agree. I also check the fuel flow; this should be about 25 USG/hr. There isn’t much scope for the engine to have some non obvious performance shortage while burning the right amount of fuel.
Obviously if a piston is seen exiting the engine then you have no option but to jump on the brakes 
I read about the 70% at half way in Sparky Imeson’s book ‘Mountain Flying’ and I use it though my percentage is a little higher just because of where the first number is on my ASI. Perhaps more valuable at tight strips is the associated need to walk the strip and note the half way point as well as the conditions of the second half compared to the first.
Jason – yes I did, and yes I would before lift off. Unless you’re pushing the TODR vs TODA, with the take off safety factors I would say there should be perfectly enough space to safely reject a takeoff from Vr in an average SEP. As an aside, I find stacks of people that have never really practiced a rejected take off.
Right, most private pilots never practice that stuff, and of the ones that do most pull the power five seconds into the t.o. run … I understand that nobody wants to bend an airplane in training, but this is really useless. It’s a fine line between productive and dangerous training … and it takes a great instructor to really achieve something.
It is really a V1 for SEPs!!!!
V1 is the critical engine failure recognition speed or takeoff decision speed. It is the speed above which the takeoff will continue even if an engine fails or another problem occurs
There is no such thing for a SE Aeroplane
Balliol wrote:
Jason – yes I did, and yes I would before lift off. Unless you’re pushing the TODR vs TODA, with the take off safety factors I would say there should be perfectly enough space to safely reject a takeoff from Vr in an average SEP. As an aside, I find stacks of people that have never really practiced a rejected take off.
But that is the point. You seem to be doing the calculation and know you can stop. Many don’t have a clue.
Steering a tailwheel aircraft to a stop with no propwash is much trickier than with the engine running.
Stopping the engine when aborting on a short strip will help. I didn’t, and just hit the fence.
PS there’s been a two-fatalty accident this weekend where the aircraft failed to gain height on T.Off, hit a hedge, and burned.
Balliol wrote:
I think trying to export twin and commercial type performance calculations and the notion of continuing a take off with a failure beyond a certain point in SEP is utter guff to be honest.
Sure, but making procedures appropriate to a SEP is something else. Whenever the runway length is in the least critical, I determine a decision point at a distance of at least the expected take-off run and with at least as much runway remaining as corresponds to a landing run. If I’m not airborne at that point I abort.
