P337 Fuel Consumption

[aknott]

Considering buying a P337.

What do people expect for block fuel burn @ say 17,000 ft at 65% power (with Intercoolers if it makes a difference)?

Also what TAS should I expect to see at standard temps?

Thanks

Andrew

[kevin]

For all altitudes I use 25 gph plus 10 gallons for climb for planning purposes, at 65% power, which with my intercoolers is 27" and 2400 RPM. This always results in my having some fuel margin. On a recent 3.5 hour flight at 17,000, the above rule would predict 97 gallons burned, actual burn was 93.

I have boots which slows me down, I get 210 mph TAS at 17,000 and the above power settings.

It's a '73 P337 with American Aviation intercoolers.

It has a TAS indicator (not a ring, it actually has an outer ring that moves depending on altitude and temperature), so I am telling you what the indicator says. It may be off, but it seems to match actual groundspeed and expected winds a high percentage of the time. I have never flown it over a closed course to check it.

Oh ya, I lean 50 degrees rich of peak on the cylinder that peaks first, and I do not have GAMI injectors, so the other cylinders are running richer. I have about a 100 degree spread from the coldest to hottest cylinder.

Kevin

[aknott]

Kevin,


Thanks for the input. Interested in your comment re boots. How much do you think they slow you down?

Thanks

Andrew

[kevin]

10 mph, some say 15.

Kevin

[aknott]

I'm suprised it's as much as that. I don't have a POH for a Skymaster yet (I have one on order) but on an Aztec it's a matter of a few knots according to the POH.

Why do you think it has that much impact?

Andrew

[kevin]

Well, as I say, I think it is 10 mph, not 15. The 10 mpg figure comes from flying booted and unbooted P337s of the same year at the same power settings, and seeing the difference. It is backed up by talking to other pilots who have done the same. But then, there is disagreement about everything in aviation, why not this? I am sure someone will tell me I am wrong...

The only real proof would be to add boots to the same airplane, and I have never done that...

As to why more impact than an Aztec, you've got the wrong guy for that question, I do not have the engineering knowledge to comment. I just fly 'em and fix 'em...

Kevin

[aknott]

Fair enough!

I really appreciate the info though!

[Bob Cook]

Kevin

How much does a prophylactic slow you down Kevin?
Bet you never measured it ? <G>

I rather doubt clean "boots" will take more than a mph off the airspeed. maybe more due to weight. Keep them clean and polished.

You will slow down a lot more in certain conditions when you do not have them. (that's why you do have them)

Running around it a "P", being used to its fullest extent, I guarantee you will be using them...

As far as a Aztec is concerned there is nothing aerodynamic on that aircraft including the wings. Kinda like a "beaver". <G>

A 337 is far more efficient than any other twin because there is less appendage out there to create drag.

Kevin, ur right, about 10 mpg is what I read mos of the time. That is when i am not flying into a headwind (5% of the time).



Bob

[aknott]

Bob,

Exactly what kind of "beaver" are you referring to? :-)

[Bob Cook]

A DeHavalland Beaver.
Big thick wings, radial engine and profile of a steam engine.
need a picture ?

Bob

[aknott]

Oh that kind of beaver!

It even makes a Aztec look streamlined!

Andrew

[SkyKing]

I have to agree with Bob... I'll bet there's not any significant decrease in speed with boots or without. Cruising around low (5000-7000') we typically see 145-150 KIAS with 27" MP, 2300 RPM and 60PPH each end, with our '77 P-model and we're equipped with American Aviation Intercoolers, boots, and R/STOL.

SkyKing

[rick bell]

my "p" had boots and were removed to add the stol kit. sent them to boots west for refurbishing, they lost them and then went broke (but thats another story) never noticed any difference, it there is it is very small, maybe 1 or 2 mph.