Why not this?

EdFred

EdFred

Taxi to Parking
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White Chocolate
Short field take offs. Why not implement part of the soft field technique when starting the take off roll? Instead of taxiing onto the runway getting lined up, and then holding brakes and adding power, why not hold the brakes and add power before taking off. You will accellerate more slowly from a complete stop than you do a slow roll. So why not add power before getting on the runway just like we do with soft fields?

I haven't done take off rolls measuring this yet, but I have noticed when doing this, I use less runway.
 
excellent question Ed. Probably because it seems that the hold the brakes, full power method is the way typically laid out in POH's and FAA literature on the subject (I think) and how it is usually tested. So sadly, once again, students learn that way because that is the way they will be tested.

Im with you on the quicker acceleration though. Coeffecient of kinetic friction is always lower than static.
 
I belive because you can make a tighter turn at slow/no speed then you can at power, turning with higher speed reduces the runway length you have to use. Most short feild also have no taxiways and doing a fast 180 is difficult.

Just my WAG... thinkging about the short, non soft feilds I've flown out of.

And then just because it's turf doesn't make it soft. I have used the full power with breaks on a short turf runway before. It wasn't musshy and the grass was nice and short, we did jump it off the ground early into ground effect but we used the full breaks / full power at the begining of the roll. (the short runway at maple grove).

Missa
 
I know of guys who have had to land in fields to short to take off from. To get out they fast taxied, downwind, turned around as fast as they could, then were able to take off as they had speed to begin with. The one I know for sure of was in a B-24 in WWII England, but I have heard of other similar situations.
 
Missa said:
I belive because you can make a tighter turn at slow/no speed then you can at power, turning with higher speed reduces the runway length you have to use. Most short feild also have no taxiways and doing a fast 180 is difficult.

Just my WAG... thinkging about the short, non soft feilds I've flown out of.

And then just because it's turf doesn't make it soft. I have used the full power with breaks on a short turf runway before. It wasn't musshy and the grass was nice and short, we did jump it off the ground early into ground effect but we used the full breaks / full power at the begining of the roll. (the short runway at maple grove).

Missa
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I'm not talking about barrelling onto the runway at the speed of plaid. LOL You just have to be moving a little - around 5-10kts. Try it on a back taxi, I guarantee you will use less runway.
 
the speed of plaid. lol. reminds me of Ron White "We were going half the speed of smell, got passed by a kite..."
 
I suspect the FAA prefers the "stop, power, go" technique to discourage folks from tipping over when trying to make the turn at too high a speed, especially in taildraggers. In addition, some aircraft have prohibitions or restrictions on rolling turn takeoffs due to unporting of the fuel ports because the fuel in the tank to the outside of the turn goes to the wingtip end of the tank.
 
N2212R said:
Short field take offs. Why not implement part of the soft field technique when starting the take off roll? Instead of taxiing onto the runway getting lined up, and then holding brakes and adding power, why not hold the brakes and add power before taking off. You will accellerate more slowly from a complete stop than you do a slow roll. So why not add power before getting on the runway just like we do with soft fields?

I haven't done take off rolls measuring this yet, but I have noticed when doing this, I use less runway.
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I suppose this is OK as long as you do a full power runup to check static RPM before taking the runway. One of the reasons to go full power before releasing the brakes is to check static RPM and verify all engine gauges in the green before rolling.
 
Ron Levy said:
I suspect the FAA prefers the "stop, power, go" technique to discourage folks from tipping over when trying to make the turn at too high a speed, especially in taildraggers. In addition, some aircraft have prohibitions or restrictions on rolling turn takeoffs due to unporting of the fuel ports because the fuel in the tank to the outside of the turn goes to the wingtip end of the tank.
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But they will give them the A-OK to tip over on a soft field?
 
N2212R said:
But they will give them the A-OK to tip over on a soft field?
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There's always the speed judgement thing for the PIC naturally, on any surface (that's why I've always hated sharp step-turns on the water, too damn dangerous). Soft fields often won't let the plane go very fast at all at first application of power, for a number of seconds.

We use the rolling method when practical not only for takeoff but for the run-up, so as to avoid the powering prop vortex inducing small stones into the prop arc. I prefer about a 45 degree angle approach to the RWY if possible, to maximize speed without aircraft wing tipping & dragging otherwise, it often just isn't worth it compared to a start on the RWY, there's often no gains to be had.
 
Ed - I ALWAYS do short fields out here like that, and for a reason:

Short field almost always equals gravel strip. You ever sit with full power and brakes locked on a gravel strip?

The sound would make you want to cry.
 
Ed: Excellent question. I asked the same question of my CFI when I was in training. It just didn't make sense to me. If I entered the runway at 5 kts it would take a shorter distance to get to 55kts than from a dead stop.

My CFI explained it by saying pretty much what Bill Jennings said. Essentially since you have less room for error make sure everythings working ok before you start the roll. But really no reason that could not be done on the taxiway cept I guess that some problems occur after power changes. I still think it makes more sense to enter rolling.
 
My instructor taught both methods. First the breaks and throttle technique because it was the FAA way and then the throttle from taxi technique because it works on short fields, and like Sky Hog said you don't sit there pulling stones up with the prop. My examiner accepted both so long as I could explain why I'd do either one. Plus my plane has a hand brake. It is a real pain to hold the break, push the throttle and control the yoke all at once. One way or another it takes three hands for a little bit and I was only born with two. Another thing I've noticed, when people pull on the runway they don't stop until the plane is perfectly aligned which eats up some possibly much needed runway length.

Barb
 
Remember, for Short Field takeoff distances, the Tail has to be hanging over, off the end of the legal runway. The mains need to be on thevey edge of useable runway. do that and I'll bet it works out equally.

I did that one once in the USN. The bird was minimally fueled for the flight to the Marshalls and was pushed back until the tail was wayyyyy over the end.
 
N2212R said:
Short field take offs. Why not implement part of the soft field technique when starting the take off roll? Instead of taxiing onto the runway getting lined up, and then holding brakes and adding power, why not hold the brakes and add power before taking off. You will accellerate more slowly from a complete stop than you do a slow roll. So why not add power before getting on the runway just like we do with soft fields?

I haven't done take off rolls measuring this yet, but I have noticed when doing this, I use less runway.
Click to expand...

I think they are probably weighing the risk/benefir ratio and on a hard but short field, on average the gain will be small enough not to outweigh the potential problems. That said, it's a technique I use quite frequently even on long runways just to get the heck out of the way. LGB used to clear me off with "04Y If you can get off with no delays, clear for 31" Throttles go up "04Y rolling", because they knew I when I called ready for departure I wouldn't waste time on the runway. If I wasn't feeling s**t hot about the airplane, I'd just call em back with "I'll wait" cause often there was a MD 11 on final when they called like that. As PIC, it's your call as to what technique you regard as safest for the flight.
 
In retracts there could be an increased risk of a gear collapse due to the side loads imposed with the temptation to accelerate out of a turn to takeoff, imho.
 
Steve said:
In retracts there could be an increased risk of a gear collapse due to the side loads imposed with the temptation to accelerate out of a turn to takeoff, imho.
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One of the potential risks, but when you consider what kind of forces they see on some ugly crosswind landings, it puts some perspective to that risk. That said, I remember the BD-10 collapsing the gear taxiing onto the runway.:D
 
Well, I was thinking in terms of repetitive side loads making a practice of it.

That BD-10 had a propensity to kill its pilots, too, as I recall.
 
I think one point to be taken away from this discussion is that it's all situations: there's no one single perfect short field or soft field technique for all occations. Aircraft limitations, surface conditions, combinations of short and soft, etc., must all be taken into account when deciding exactly how to do it with any given airplane at any given airport on any given day.
 
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