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holding brakes on short field T/O
I have a couple of questions regarding short field T/O since I fly out of a very short field. I was instructed to hold the brakes, 10 degrees flaps, and release brakes. But according to the "Airplane Flying Handbook", I quote,
"Some authorities prefer to hold the brakes until maximum obtainable engine r.p.m...however, it has not been established that this procedure will result in a shorter takeoff run...take off power should be applied smoothly and continuously-without hesitation..." (5-9). Is this one of those items that would be forever argued and never be solved? Also does holding the brakes (especially if you don't hold the brakes tight enough, let the airplane move a bit) does that harm the brakes as opposed to holding the brakes fully? Which one do you prefer/teach and why? |
Originally Posted by PearlPilot
(Post 582156)
I have a couple of questions regarding short field T/O since I fly out of a very short field. I was instructed to hold the brakes, 10 degrees flaps, and release brakes. But according to the "Airplane Flying Handbook", I quote,
"Some authorities prefer to hold the brakes until maximum obtainable engine r.p.m...however, it has not been established that this procedure will result in a shorter takeoff run...take off power should be applied smoothly and continuously-without hesitation..." (5-9). Is this one of those items that would be forever argued and never be solved? Also does holding the brakes (especially if you don't hold the brakes tight enough, let the airplane move a bit) does that harm the brakes as opposed to holding the brakes fully? Which one do you prefer/teach and why? Joe |
Originally Posted by PearlPilot
(Post 582156)
"Some authorities prefer to hold the brakes until maximum obtainable engine r.p.m...however, it has not been established that this procedure will result in a shorter takeoff run...take off power should be applied smoothly and continuously-without hesitation..." (5-9).
I believe I'd instruct whatever the AFM/POH says, since I can't mathematically prove either one, and the Practical Test Standards say the applicant "applies brakes (if appropriate)", which could only mean "appropriate to that aircraft." Zach |
The numbers in the POH were all done from a complete stop. So if you want the data to be accurate, you must do the t/o from a complete stop. Otherwise, you're a test pilot :)
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Over here we teach on a short field to hold the breaks and apply full power and then observe the static rpm before releasing brakes
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One other thing to mention (which I teach my students), is on a shorter field there is much less room to abort a take-off. I would much rather notice a light or malfunction while I'm stopped at the end of the runway vs. already rolling 1/4 or 1/2 the way down the runway... By the time you notice a problem, react, pull the power to idle and apply the breaks, it could be a little too late... Good chance you could slide right on off the end.
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What kind of aircraft are we talking about? What does your POH say?
In C-152s and 172s, I've always taught holding the brakes until max power is established, then release. I suppose I taught this mainly because it's how I was taught, and it's what I believed the DEs would expect. In practice, I've done it this way because most of the short fields I've taken off from were also high-altitude fields, and I wanted to lean the mixture for max power prior to brake release. |
Always refer to the POH/AFM for what technique to use. The takeoff data in the C172's AFM indicate that the numbers are when you use the "Short Field Technique" from Section 4. The way I teach is how the AFM says to, that is, for the C172S: Apply Brakes, Go Full Throttle, Lean Mixture for Max RPM (For operations above 3,000 feet pressure altitude), Check Power Indication and Engine Instruments in the Green, Release Brakes, Accelerate to Vr (Dependent on weight, at MGTOW of 2550, Vr=51), Hold Vx Pitch Attitude to Climb Out at 50' Obstacle Speed (Barrier Speed, again, dependent on weight, for 2550lbs, 56 KIAS) Until Clear Obstacle(s), then at Positive Rate of Climb and at least 60 KIAS, flaps up, climb out at Vy.
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Why not try both back to back and see what you get?
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I do fly a 172 and I realize that the manufacturer's recs take precedence over the book (Airplane Flying Handbook) that I referenced to earlier. I thought it was "interesting" that they mentioned, how it was not a proven fact that holding of brakes reduces the total take off roll. But like one poster mentioned, it is better to observe all the engine instruments whilst applied full power, and that if there was a problem, the aborted take off would be less messier.
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