nigelspeedy
Well Known Member
The other half of my learning how to land my 8 was learning how the takeoff configuration and technique affected the takeoff distance. I did an experiment to find out by doing a series of takeoffs using flap 0, 10, 20 & 40 degrees. For the ground roll I also used a tail up attitude (approximately 0 deg pitch attitude), tail low (approximately 5 deg nose up pitch attitude) and tail down (tailwheel lightly held on the ground to hold the 3 point attitude of 11 deg nose up). So a matrix of 12 takeoffs overall, which I measured with a DGPS on runway 24 at California City, L71, in nil wind at 1540 - 1600 lbs. For each takeoff I adjusted pitch attitude after liftoff to achieve 1.2 Vs for the particular flap configuration at 50' AGL. This resulted in 72 KIAS for 0 deg flap to as low as 60 KIAS for 40 deg flap. Each takeoff started with mixture rich, prop full fine with the aircraft held stationary on the brakes until throttle was fully forward. There was only one attempt at each configuration so there is no statistical relevance. I've made no attempt to correct for runway slope, aircraft weight, wind, air density or power so these results are only representative of my aircraft on the test day, which is a polite way of saying they are incorrect everywhere else so don't use them for operational planning. I was really only after the relative changes not absolute distances.
The results are shown in the graphs below.
[/URL][/IMG]
[/URL][/IMG]
[/URL][/IMG]
[/URL][/IMG]
[/URL][/IMG]
[/URL][/IMG]
[/URL][/IMG]
So in general tail low or tail down results in a shorter takeoff distance than tail up. The advantage for tail down over tail low is minimal.
On the farm dad alway said "if a little is good, more is better and too much should be just about right", but it doesn't seem to be that way with flaps. No flap is always the longest takeoff distance but 10 deg does just as well as 20 or 40 for the most part.
Taking off with the tail up gives the best field of view. Tail low allows you to see the runway centerline so directional control is still easy. Tail down might be a bit harsh on other than smooth surfaces and the field of view is a not as good as tail low or tail up and there is no real performance gain.
When using 40 deg of flap you get off the ground slower but the extra drag means it takes the same ground distance as 10 or 20 deg flap to get to the lower speed. Using 40 deg flap and maintaining 1.2 Vs to 50 feet is great as long as the engine keeps on running but 20 deg nose up, 40 deg flap, 60 KIAS and an engine failure would be pretty sporting combination.
So based on this I've settled on the following:
Normal Takeoff from a sealed runway with no obstacles. Rolling takeoff, Flap 0 deg and tail up.
Short field takeoff: Hold on brakes until power applied, Flap 10 deg and tail low during the ground roll, 1.2 Vs till clear of obstacles then accelerate to normal climb speed.
Soft field takeoff: Rolling start, Flap 10 deg, tail low, level off to accelerate to normal climb speed after ground break.
Cheers
Nige
The results are shown in the graphs below.
So in general tail low or tail down results in a shorter takeoff distance than tail up. The advantage for tail down over tail low is minimal.
On the farm dad alway said "if a little is good, more is better and too much should be just about right", but it doesn't seem to be that way with flaps. No flap is always the longest takeoff distance but 10 deg does just as well as 20 or 40 for the most part.
Taking off with the tail up gives the best field of view. Tail low allows you to see the runway centerline so directional control is still easy. Tail down might be a bit harsh on other than smooth surfaces and the field of view is a not as good as tail low or tail up and there is no real performance gain.
When using 40 deg of flap you get off the ground slower but the extra drag means it takes the same ground distance as 10 or 20 deg flap to get to the lower speed. Using 40 deg flap and maintaining 1.2 Vs to 50 feet is great as long as the engine keeps on running but 20 deg nose up, 40 deg flap, 60 KIAS and an engine failure would be pretty sporting combination.
So based on this I've settled on the following:
Normal Takeoff from a sealed runway with no obstacles. Rolling takeoff, Flap 0 deg and tail up.
Short field takeoff: Hold on brakes until power applied, Flap 10 deg and tail low during the ground roll, 1.2 Vs till clear of obstacles then accelerate to normal climb speed.
Soft field takeoff: Rolling start, Flap 10 deg, tail low, level off to accelerate to normal climb speed after ground break.
Cheers
Nige