V1

[donnlass]

Hi

I saw that impressive short-run 757 take off which posed the question of V1.

Since some takeoffs are assisted by a good headwind and need less runway than the average, where does V1 fit in when less runway distance is covered on the takeoff run?:eek:

Cheers

Donnlass



Cheers

Donnlass

[Mad (Flt) Scientist]

There are in many cases a range of possible V1 speeds, with the upper limit usually being the fastest speed from which you can safely reject a takeoff and come to a stop on the runway, and the lower limit usually being the lowest speed from which you can continue a takeoff with a failed engine and safely takeoff, with the considerations usually being either maintaining control of the aircraft with a failed engine (V1 determined by VMC) or having engough performance to continue the acceleration to the rotation speed and climb away in the available distance.

For en aircraft which is "overpowered" it is unlikely that the single engine continued takeoff is limiting for performance. So the lower limit is likely set by VMC considerations.
Unless the aircraft has sub-par brakes, with good acceleration it's likely that the RTO distance requirement also won't be a consideration, and so V1 may be effectively unconstrained at the upper end. In such a case the rotation speed, Vr, is the practical upper limit for V1.

So for the case you describe, V1 could be selected anywhere between VMC and Vr. Depending on the other circumstances (crosswind, company policy, nature of the overrun area) you might bias V1 high or low in that range to minimize the residual risks.

[donnlass]

Thanks lots for explaining that for me Mad (Flt) Scientist.:ok:

Cheers


Donnlass

[bucket_and_spade]

Our performance tables have three columns for the v-speeds - one for nil wind (most often used), one for a 10 kt headwind and one for a 10 kt tailwind.

B&S