Short Field Takeoff Speeds

[B767Driver]

My Piper Warrior has a Vx of 63KIAS. The short field takeoff performance chart lists a barrier speed of 55KIAS. At first I thought this was because the POH recommends 25 flaps for the short field takeoff. But I noticed the 0 flap normal takeoff performance chart has the same barrier speed.

Does anyone know the difference between Vx and the short field performance barrier speed?

[MidlifeFlyer]

The "barrier" speed is usually what your speed should be at 50 AGL.

Remember, you are rotating at a speed and aiming for Vx. It doesn't happen immediately. It doesn't go from rotation to Vx in a 1/4 second. The airplane has to accelerate as it climbs. From rotation, it's gotta get to 55 before it gets to 63, right?

If the takeoff is done by spec, the acceleration will bring the airspeed through the 55 at 50 AGL.

[B767Driver]

Originally Posted by MidlifeFlyer

The "barrier" speed is usually what your speed should be at 50 AGL.

Remember, you are rotating at a speed and aiming for Vx. It doesn't happen immediately. It doesn't go from rotation to Vx in a 1/4 second. The airplane has to accelerate as it climbs. From rotation, it's gotta get to 55 before it gets to 63, right?

If the takeoff is done by spec, the acceleration will bring the airspeed through the 55 at 50 AGL.

Makes sense to me...thanks for the reply.

[Foxcow]

I was also taught that it is a momentum thing too. As you are accelerating down the runway and you pitch up for your barrier speed your initial rate of climb is going to be greater than if you were piching for Vx. Once your rate of climb starts to settle down, you can pitch for Vx. By this time, you are usually over 50ft.

[MidlifeFlyer]

Originally Posted by Foxcow

you pitch up for your barrier speed your initial rate of climb is going to be greater than if you were pitching for Vx. Once your rate of climb starts to settle down, you can pitch for Vx. By this time, you are usually over 50ft.

I don't think it's a =pitch= differential. You =pitch= for the attitude that will get you to Vx. It just takes time to get there.

I think we mean the exactly the same thing. It's just that when I hear "pitch for" with two different speeds, I hear that you are making pitch changes. You're not and wanted to clarify that in case someone else has my hearing problem.