Capt. Geoffrey Thorpe
Touchdown! Greaser!
- Joined
- Jun 7, 2008
- Messages
- 16,026
- Location
- DXO124009
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Light and Sporty Guy
It's not an "obstacle", it's an "opportunity".
Management 101
Management 101
Is the term "50 Ft obstacle" just a average?
- Thread starter Matthew Black
- Start date
So what if the obstacle is 100 ft and I want to calculate if I can clear it based on the 50 ft data. The 100 ft obstacle would obviously need to be further away than the 50ft for it to be a consideration. Is there a formula I can use?
Maybe it is just about knowing how much time it would take to get to that next obstacle along with your climb rate at Vx?
RussR
En-Route
Pretty much, to a first approximation anyway.
The 50ft distance has to account for acceleration, ground effect, rate of rotation, gear retraction drag, etc. Not very steady state. That's why many airplane POHs have you climb out a speed of less than Vx until clearing that obstacle - because that was determined to be the best way.
After 50 feet-ish, though, the climb is (or can be) a lot more stabilized. So if you have tables for climb rate at Vx in your POH, and you know or can estimate your groundspeed at the time, you can calculate the distance it should take to climb that other 50 feet.