Piper Warrior II Soft-field performance

[pilotx86]

Hello all!!

So for some this may be a no-brainer, but I had a situation that I don't think I've ever encountered before.

I landed at a 4000 foot grass strip, and then took off again with a student. As we were taking off using the proper soft-field technique, I realized how much runway it took. I do realized that a plane may take up to 50% more runway than on a hard surface. That day, it was approximately 37 degrees C at sea level.

Here's my question: The POH goes only to about 30*C at sea level. Does that mean that anything above 30 is test pilot territory?

From my experience, I was in test pilot territory, and the plane can't be operated if there is no available takeoff distance data for sea level, 37*C for a Piper Warrior II

I think I know the answer, but I would love to gather the minds that be on this board to confirm it!

Thanks!

 

[dell30rb]

I can't comment on the POH

But to get the best results out of a soft field takeoff, hold the nose so that the nosewheel is just barely skimming the surface or 1" off.

If you hold the nose a a foot off of the ground, the takeoff will use more runway due to increased induced drag.

 

[pilotx86]

Thank you . No question on the technique, I'm more concerned about the Operating handbook issue. Thanks!

 

[murphey]

Hello all!!

So for some this may be a no-brainer, but I had a situation that I don't think I've ever encountered before.

I landed at a 4000 foot grass strip, and then took off again with a student. As we were taking off using the proper soft-field technique, I realized how much runway it took. I do realized that a plane may take up to 50% more runway than on a hard surface. That day, it was approximately 37 degrees C at sea level.

Here's my question: The POH goes only to about 30*C at sea level. Does that mean that anything above 30 is test pilot territory?

From my experience, I was in test pilot territory, and the plane can't be operated if there is no available takeoff distance data for sea level, 37*C for a Piper Warrior II

I think I know the answer, but I would love to gather the minds that be on this board to confirm it!

Thanks!

If true, then far too many cherokee/warrior/archer pilots would be grounded for 4-6 months of the year, between temps & altitude.

37C = 99 F

Temps in Arizona, New Mexico, Colorado and so on exceed 95F on a daily basis for many months of the year. Add in the altitudes, and we wouldn't be flying much.

The POH was written decades ago by people who live & work & build airplanes at sea level (Florida). If something happens, will the insurance company come after you? Entirely up to your insurance.

First issue is the density altitude. Example, I often fly from Denver to Salida, about an hour flight. In the summer I can get there, but can't get home due to DA. And let's not even talk about Leadville. So you need to adjust for temps.

Next is weight. A fully loaded warrior needs lots more runway than lightly loaded. Another adjustment for your calculations.

And then last, but by no means least important, is length & type of runway. There are rules of thumb for different surfaces. I've never liked the Piper manuals for this type of info - the Cessna manuals are so much better.

You don't mention how much of the runway used before airborne.

For example, the C172 manual recommends an additional 15% distance for grass at sea level. So let's use this as the test case. Characteristics are similar enough for the two aircraft. By the way, the C172 charts only go up to 8K MSL also.

At SL, 40C, short field, 10 deg flaps, 2400# weight, C172 ground roll is published as 995 ft. and 1685 for the 50 ft obstacle (let's round to 1000 and 1700). There's a footnote - for operation on grass add 15%. So for grass, 1100 & 1870 ft. Don't know about you, but I always err on the side of caution and for grass, add 25%.

 

[nosehair]

For soft field T.O.s, there are no "real" performance numbers. There may be guidance in some percentage numbers to add or multiply , but that is such a WAG.
If the field is not really very soft you should barely hold the nosewheel off creating less drag.
But if the surface is really soft, the nose will have to be held higher creating more drag and a much longer run. The actual softness, roughness, or high grass growth has so much effect it is impossible to accurately calculate.