Density altitude -3000 feet.

DFH65

DFH65

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DFH65
Waiting on a commercial flight pulled up the ASOS guess the cold weather is good for something. :D
 
That's crazy! I bet that plane climbs like a bat outta hell.
 
I once flew out of Edmonton Internation (CYEG), with an OAT of -40.

Based on the elevation being 2,373, and the pressure was pretty high (like 30.40 IIRC), that gives a DA of -4,913', or over 7,000' differential between field elevation and DA.
 
I don't recall what temp it was yesterday, but at 80 kts I was climbing at 1300 fpm in my Archer.... I was like screw it, let's do this!
 
SixPapaCharlie said:
That's crazy! I bet that plane climbs like a bat outta hell.
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To some degree, but since turbines are either torque or thrust limited, you don't notice it as much as in a piston aircraft.
 
In my neck of the woods it isn't unusual to see DAs down to -7000'. Engines make good power IF you can provide them adequate fuel, which can be a trick. How do you enrich for -7000'? Wings provide excellent lift and props make tons of thrust. In cold temps we need to turn prop speeds back to prevent excessive tip speeds. On hard packed surfaces skis are really slick so takeoff performance can be crazy good but with no brakes landing performance isn't equally rewarded. Fun stuff, at least until you sink a ski through the ice and have to wade in the water in sub zero temps. That is not so fun.
 
Stewartb said:
. On hard packed surfaces skis are really slick so takeoff performance can be crazy good but with no brakes landing performance isn't equally rewarded. .
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Carry one of those dog sledding anchors.....
 
Some of you guys might need to restrict your intake air a little to keep from running too lean in cold temps. It's all fun until you cook a cylinder. Watch those EGTs!
 
At DA -3000 even these guys can get airborne...

75ed6576-ba73-4a83-a23c-380fbc16dfcb.jpg
 
DA -4900 here in Eastern Iowa this evening. It is -5 F on my porch, and the altimeter is 30.88.
 
Reminds me of some T/G's I did solo in a lightly fueled Cessna 182 with an outside air temp of 10F....

Should have had a helicopter rating for those...
 
Waiting in TEB for the passengers to show up and the DA is currently -3750, but along with that, the temperature - 12C and the windchill is -25C. (((((Burrrrr))))))
 
Speaking of... What would be the proper procedure for takeoff performance of a -3000' DA as far as mixture goes? Current altimeter here is 30.71 which is high and DA is -3100' right now.
 
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Stewartb said:
In my neck of the woods it isn't unusual to see DAs down to -7000'. Engines make good power IF you can provide them adequate fuel, which can be a trick. How do you enrich for -7000'? Wings provide excellent lift and props make tons of thrust. In cold temps we need to turn prop speeds back to prevent excessive tip speeds. On hard packed surfaces skis are really slick so takeoff performance can be crazy good but with no brakes landing performance isn't equally rewarded. Fun stuff, at least until you sink a ski through the ice and have to wade in the water in sub zero temps. That is not so fun.
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No way to go richer than full rich. Just make sure the oil temp and Cylinder head temp is up in the green, and easy on the throttle(s).

I left Barrow once at -41f. The plane spent the night in the hanger with the engine blankets on and tanis heaters were plugged in all night and it still took about 30 minutes to fully warm up the engines after start up. I went out the top of the class E airspace about the end of the runway.

A little isopropyl alcohol in the gas helps keep the fuel from freezing.
 
Gasoline doesn't freeze in temps we'll encounter. Water in the gas will, and ice crystals in the finger screens isn't a good idea so isopropyl alcohol can be helpful in winter. For guys like me who park outside we can't sump our tanks for several months since ice won't drain very well. It sure will foul a wing drain, though, and that will ruin your flight schedule. I run a little isopropyl occasionally. Actually I prefer Seafoam, which is mostly isopropyl alcohol. That ought to get a rise out of the maintenance police. :) your POH should address approved use of isopropyl. TCM and Lycoming instructions will if your POH doesn't.

Some guys in the far north will use restricter plates on the carb air intake to compensate for air density if their jetting isn't rich enough. If your EGTs are on the high side of 1500* you need to do something to alter the air/fuel ratio. For you guys in the lower states with less experience in cold flying, pay attention to your temps. Leaning by habit is a bad thing in cold weather. So might be winter fronts. Your oil temps will run lower but your CHTs may run higher because of the lean running. Blocking the oil cooler is common practice. Nobody I know uses a winter front.
 
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