Standard Altitude Performance Charts

Manderson

Manderson

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Manderson
Up to this point, I've been training in a Cherokee 140 with performance charts listed as "Density Altitude vs. X". I have moved up to a Cherokee 180, and am finding that in its POH, all the performance charts are listed as "Standard Altitude vs. X".

Trying to calculate my climb performance. Is this essentially the same chart?
 

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Manderson said:
Up to this point, I've been training in a Cherokee 140 with performance charts listed as "Density Altitude vs. X". I have moved up to a Cherokee 180, and am finding that in its POH, all the performance charts are listed as "Standard Altitude vs. X".

Trying to calculate my climb performance. Is this essentially the same chart?
Click to expand...

Yes unless it's a trick question, then I don't know.

dtuuri
 
Density altitude is indicated altitude corrected for nonstandard pressure and temperature (and position error, technically).

Standard altitude is standard pressure and temperature.

Sounds the same to me.:yes:
 
MauleSkinner said:
Density altitude is indicated altitude corrected for nonstandard pressure and temperature (and position error, technically).

Standard altitude is standard pressure and temperature.

Sounds the same to me.:yes:
Click to expand...

Yup...

29.92 and 59f are the standard....
 
Well, that certainly is the dictionary definition.

But it also CLEARLY is not what that chart shows. It's density altitude, or there would be a temperature correction. An airplane's climb performance doesn't care what the pressure is. Only density.
 
FastEddieB said:
Doesn't it?

Doesn't 1" less pressure equal 1,000' higher altitude (in terms of performance, of course)?
Click to expand...

Yes, but it's the density that matters. Fly at a higher pressure altitude on a cold day, and you can get identical performance if density altitude is equal.

You're making an airplane climb, not building an altimeter.
 
MAKG1 said:
Yes, but it's the density that matters. Fly at a higher pressure altitude on a cold day, and you can get identical performance if density altitude is equal.

You're making an airplane climb, not building an altimeter.
Click to expand...

Ok, so if it's not a standard pressure day, does it affect how this chart is used? If I calculate that the given density altitude is 1000ft ft that day, could I just use the 1000ft mark to get the climb rate on this chart?
 
Manderson said:
Ok, so if it's not a standard pressure day, does it affect how this chart is used? If I calculate that the given density altitude is 1000ft ft that day, could I just use the 1000ft mark to get the climb rate on this chart?
Click to expand...


I say ... yes.... 710 fpm climb...
 
Manderson said:
Ok, so if it's not a standard pressure day, does it affect how this chart is used? If I calculate that the given density altitude is 1000ft ft that day, could I just use the 1000ft mark to get the climb rate on this chart?
Click to expand...

Yup, exactly.
 
MAKG1 said:
Well, that certainly is the dictionary definition.

But it also CLEARLY is not what that chart shows. It's density altitude, or there would be a temperature correction. An airplane's climb performance doesn't care what the pressure is. Only density.
Click to expand...

what is clearly not what the chart shows?

Standard atmosphere at sea level is an indicated altitude of 0, 29.92 in Hg, and 15 degrees C. A sea level altitude with 29.92 in Hg and 15 degrees C works out to a density altitude of sea level.

Standard atmosphere at 10,000 feet is 10,000 indicated, 29.92, and -5 degrees C. Calculate density altitude from that, and you get a 10,000 foot density altitude.
 
MauleSkinner said:
what is clearly not what the chart shows?

Standard atmosphere at sea level is an indicated altitude of 0, 29.92 in Hg, and 15 degrees C. A sea level altitude with 29.92 in Hg and 15 degrees C works out to a density altitude of sea level.

Standard atmosphere at 10,000 feet is 10,000 indicated, 29.92, and -5 degrees C. Calculate density altitude from that, and you get a 10,000 foot density altitude.
Click to expand...

What do you do if it's warmer than standard?

That's why it's DA.
 
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