Density altitude take-off performance

[Larson]

Can anyone share the highest altitude and temperature that one has completed a take-off when on amphib floats?

 

[Snowbirdxx]

Lars

I ve been in the water with my skis. I admit not to a full stup..But highest takeoda.on snow was 14800 ft at 11 deg celsius. Go figure the da.

 

[Larson]

Tom

I am guessing that was an uphill landing and downhill take off?

What about a level landing (no slope).full stop. Then takeoff from full stop on level snow? At what height and weight would you have done this at?
Am thinking 5000ft? 8000? 10,000? ..... once again no slope?

What about floats on a lake at 6000ft, 20deg. How would it perform? .....

 

[Larson]

Re: skis in water, you need to pull a skier, that would be a sight!

 

[tbienz]

My highest level snow takeoff was 11,200 with two people, camping gear and packs & skis (done several times at different temps). On spring day with wet slushy snow almost didn’t work, but in mid winter it was fine.

 

[Snowbirdxx]

LArs,

all my skilandings are uphill and takeoffs downhill. To takeoff at 6000 ft yflat you better have fast snow. Or RATS

 

[Wayofftrack2]

Can anyone share the highest altitude and temperature that one has completed a take-off when on amphib floats?

Lars,

I just saw your question. We run a training school with a A-1 model (180hp) on Wipline 2100As.
One exercise we do is simulating a high altitude takeoff by reducing the manifold pressure. This simulates the reduced power but not the fact that you need to reach a higher TAS (same IAS) to get airborne. So its about as close as you can easily get to the real thing.

Every 1000 feet you climb you lose about one inch of MP so 22 inches equates to about 8000 feet. At max weight, which for us is 2079 lbs, you can take off using 22", just. It can take a mile or so of water. 23 inches is easy, 22 needs care and I haven't tried 21 as I think I'd run out of distance. The water state is important, calm is bad as it feels like glue, you need some ripples. The skill comes in getting on the step. The nose won't rise as much as at sea level. If you push over too quickly onto the step you'll start a gentle porpoising, best to abandon and try again. The secret is to very slowly pitch down and keep one eye on the ASI. So long as it going up you're doing well. If it's not increasing you're probably too nose high.

Practising it at sea level is fun, and you can always open the throttle if it's not working,

 

[Larson]

Wot
Really appreciate the input.
I hadn’t considered a reduced power take of, but it makes sense...

I’ll give it a try, then report back ... may be a while, I’m enjoying the HD gear too much