Do you always pitch for Vx or obstacle clearance speed in a short-field take-off?

Question

Thanks.

Answer 1

do you need to clear an obstacle?  if the strip is short (or partial paved then grass,) just get off the ground!

  if it is for a test, then the obstacle is imaginary, and you say outloud to the examiner, max performance, flaps (as specified in the POH), hold breaks, power up, check gauges, release breaks, backpressure, accellerate to Vx, pitch Vx, which is XX in this plane.

also have a no-go point on the runway...if you aren't flying by the, it is aborted (wind change, temp/pressure not what was reported, plane is tired........)

Answer 2

They are the same thing.

I tend to go for best rate (Vy) because it tends to be closer to the real Vx (rather than the ISA Vx) when density altitude is high and when I am at max gross (usually the only time I am concerned about obstacle clearance).  The reason is because Vx and Vy come closer together as the aircraft approaches its maximum altitude.

Answer 3

The answer to the question is , no!

Answer 4

That totally depend on what airplane I am flying and what problems the short field offers to me on departure.  Remember, just because you can get in doesn't mean you can get out.

Answer 5

I've not heard of obstacle clearance speed, so I'm going to go with Vx.

Vx is the best angle of climb, it gets you the best altitude over distance, but does not get you the best fuel efficiency.

No 2 ways about it.  If you want to clear an obstacle, you want to get the fastest climb you can over the shortest distance possible.  

Vx is a speed specifically demonstrated and outlined for that exact purpose.

Best Climb over shortest distance = best opportunity to clear an obstacle, without any other considerations, is VX

Answer 6

No.  Some short fields do not have climbout obstacles.

Answer 7

Vx is defined as the maximum altitude gain for the minimum horizontal distance traveled.  There are 2 factors required to clear an obstacle; takeoff distance and climb.  After you are in the air, to clear an obstacle you need maximum altitude for a given horizontal distance.  There is no speed other than Vx that gives you that combination.

Don’t take my word for it, go to the source … the FAA Airplane Handbook --- starting on page 5-8 discussion of the Short-field takeoff and maximum performance climb is discussed.  Then on page 5-10 it says after takeoff, “...the climb-out is performed at Vx until the obstacle has been cleared.”

http://www.faa.gov/library/manuals/aircr...