Flaps and Performance

[spiderweb]

I have a question about flaps and performance.

On youtube, there is a long video of a complete oral exam. At one point, the examiner asks the applicant about flaps and performance at a high-elevation airport. The student says, he wouldn't use flaps, as that would decrease performance.

Is there something I am missing here? I would have answered that I would use the recommended takeoff configuration for maximum performance, as specified in the POH. Often, as you know, that would include the use of takeoff flaps.

Thoughts? Anyone see that video?

 

[Jim Logajan]

I have a question about flaps and performance.

On youtube, there is a long video of a complete oral exam. At one point, the examiner asks the applicant about flaps and performance at a high-elevation airport. The student says, he wouldn't use flaps, as that would decrease performance.

Is there something I am missing here? I would have answered that I would use the recommended takeoff configuration for maximum performance, as specified in the POH. Often, as you know, that would include the use of takeoff flaps.

Thoughts? Anyone see that video?

You are correct about reference to the POH. It is airplane specific - even the C-172 and C-152 are different:

If the airplane happens to be a Cessna 172M, then you'll find these statements in the "Normal Procedures", "Takeoff", "Wing Flap Settings" paragraphs:

"The use of 10 degree flaps will shorten the ground run approximately 10%, but this advantage is lost in the climb to a 50-foot obstacle." ... "If 10 degree of flaps are used for the minimum ground runs, it is preferable to leave them extended rather than retract then in the climb to the obstacle." ... "During a high altitude takeoff in hot weather where climb would be marginal with 10 degree flaps, it is recommended that the flaps not be used for takeoff."

But in the Cessna 152, specifically the 1985 POH, it states:
"Using 10 degree flaps reduces the total distance over an obstacle by approximately 10%."
The "Takeoff Distance [Short Field]" chart for the C-152 has entries for altitudes from sea level to 8000ft - with the condition always being that flaps are at 10 degrees. I could find no recommendation of zero degree flaps for hot and high short field takeoffs in a C-152.