The link doesn’t work for me.
But, more to the point, I think that we are a little bemused by the thread title. What problem are you trying to solve?
I am not trying to solve a problem, more considering some scenario based planning.
Havent we all been there? Lined up, and we know there isnt sufficient distance to stop if there were a failure, and we also know there are terrain constraints.
Timothy, as you mentioned earlier do we rotate “normally”, or do we rotate with more speed, and if so, what parameters do we use?
and to widen the discussion a little, at what point might we elect to stop, even though we know we arent going to remain on the runway? How do we assess he collateral damage compared with attempting to fly.
I suppose if there is a problem to be solved, I just wonder how much we consider the various possibilities, and to what extent we have mentally set some parameters before the roll is underway or do we, as you mnetioned earlier, rely on the chances of an engine failure being very remote and deal with it as best we can should it happen?
If I am taking off from a short runway, I rotate at a lower speed, not a higher one.
This increases the chances of survival in an accelerate stop and also gives more level ground over which to accelerate to blue line in the event of an engine failure very soon after take-off.
But I generally try to avoid runways shorter than balanced field length.
I’d fly faster if the flight manual presented such a procedure.
Otherwise, if the runway is too short for the balanced field length, I either wait for conditions which are more favourable, or accept that an engine failure at exactly the wrong moment would make the plane more like a single engined plane with an engine failure. There are some operations where having two engines does not give you redundancy.
As drag increases with a square of the speed, flying faster than Vmca or Vyse as appropriate, means that gear, flaps, and in particular a stopped propeller are creating more drag than the aircraft design compensates for at the specified speed. This can be managed with adequate time at cruise speed, but may be a needless handful around Vr.
There may be another thread, but IIRC, if your MEP publishes an ASDA table it is regarded as a limitation, at least in FAA terms. Airmanship/duty of care issues acknowledged.
The Twotter will rotate on gravel runways below TOSS and then accelerate to TOSS in ground effect – but this maybe a soft field technique and not a STOL technique.
In general the POH always applies.
Pilot_DAR wrote:
I’d fly faster if the flight manual presented such a procedure.
Please can you expand?
gallois wrote:
a water tower at 1000ft agl about 1Nm further away.
That is a very big water tower
From an energy point of view accelerating past Vx until clear of obstacles is a waste. So Timothys approach is more sound get up and clean as soon as possible.
I wasnt intending this is about obstacle clearance.
It is about suffering an engine failure at or shortly after rotation and the advantages / disadvantages of carrying some extra speed when a landing back on is not possible, or other techniques.
It was intended to be about other techniques for short field departures in a twin to mitigate engine failure at any critical point, perhaps high terrain where single engine perfomance after take off might be more of a problem etc.
mcrdriver wrote:
From an energy point of view accelerating past Vx until clear of obstacles is a waste
Actually climbing at Vy minimizes energy but evn that energy gain (vs climb at Vx) is worthless as it will only translate to 3 extra seconds of flying in the case of total engine failure bellow 1000ft, depending how “sharp pilot population” we are talking about that does not give much flying or options neither
IMO, if you get an total/partial engine failure at Vx on lift off say bellow 200ft you will stall irrespective of what you fly (e.g. Gliders, SEP, MEP…) or how you would manipulate controls as you don’t have any energy to accelerate or flare (with stress that means +/-10kts on ASI and +/-20 degres on bank angles), so better accelerate to whatever V you think appropriate for your aircraft in the next show (e.g. Vs0, Vms, Vg, Vmca…)
