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Cessna POH Question.... Pressure and Density Altitude (Read 643 times)

Aug 18^th, 2012 at 2:44am

tcco94 Offline
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Okay so I've noticed throughout my whole private training that my Cessna 152 handbook refers to Pressure Altitude on the takeoff and landing performance pages...

When you take off you really want to know about Density Altitude more than Pressure Altitude (at least what I've been taught) so you'd know if you're going to get good or poor climb performance after takeoff.....

Why does the Cessna POH's use Pressure Altitude instead of Density Altitude for it's figures? Might be a dumb question but never had it answered for me.

It came across my mind the other day when looking at a cross country flight where the pressure altitude was just under 2000 feet but density altitude was about 4500...

Thanks for the help. Cool

Sincerely, Tyler

www.tylerconnell.com
http://www.phoenixva.org/index.php/profile/view/PVA1557

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Reply #1 - Aug 19^th, 2012 at 1:04pm

Rocket_Bird Offline
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The take-offs and landing charts simply groups the numbers a little tidier. Well, same goes for the cruise charts. If you look closely, the charts all list pressure altitude, but most of these numbers are grouped into different temperature columns. Because density altitude is pressure altitude corrected for temperature, the math is already done for you when you line the columns and rows up.

Think of a whizwheel flight computer. To calculate density altitude, you simply line up the pressure altitude with the temperature and you get a number. It's the same thing on the charts, only you don't get a density altitude figure but some kind of performance figure.

Cheers,
RB

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Reply #2 - Aug 19^th, 2012 at 7:09pm

tcco94 Offline
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Ah you know what that makes a lot of sense now. I guess I never really thought about it being the density altitude because I just had that temperature figure.

Thanks. Cool

Sincerely, Tyler

www.tylerconnell.com
http://www.phoenixva.org/index.php/profile/view/PVA1557

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Reply #3 - Aug 19^th, 2012 at 9:51pm

beaky Offline
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And that is why they call the PPASEL a "license to learn". Grin

congrats, BTW!! Wink

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Reply #4 - Aug 19^th, 2012 at 10:10pm

tcco94 Offline
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beaky wrote on Aug 19^th, 2012 at 9:51pm:

And that is why they call the PPASEL a "license to learn". Grin

congrats, BTW!! Wink

Yeah I hear that a lot. Almost every time I go up I learn something new. It's usually just small things but still something I love about aviation that you can always learn and become better.

And thanks!