Backcountry Pilot

[pitfield offline]

I'd be grateful if somebody could direct me to a resource which will provide me with a formula which will enable me to calculate the effect upon normal take-off of a slope (up or down). I know one must also adjust for runway composition (dry grass, long grass etc etc), and I know this is usually an 'order of magnitude' guesstimation; I'm presuming, however, that there is a mathematical way to calculate increased (or decreased, as the case may be) take-off roll on a hard-surfaced runway (assuming no density altitude and wind considerations). Thanks very much.

[Bonanza Man offline]

Here you go.

http://pilotsweb.com/train/takeoff.htm

[Zzz]

I found this for Windows. Looks like it's made specifically for flight simmers who like heavy metal, but from the screenshots it appears you can add other aircraft too. It appears very comprehensive.

http://www.topcatsim.com/?page=main

Always nice to have a rule of thumb though for the field, maybe you can derive one from playing with this.

[gbflyer offline]

That would be an interesting calculation, and fun.

In a practical sense, your statement about "order of magnitude...." is right on track, and that comes from experience. Often times one will take a tailwind takeoff if it's downhill, again depending on slope, obstacles, surface, load, etc. My point is don't be killed by a slide rule, no condescension meant.

Again, seems like a fun exercise for the science fair.

gb

[tcj offline]

Doing the calculations is a good practice to get a feel for various takeoff influences. Just remember when you do, it is like measuring it with a micrometer, marking it with chalk, then cutting it with an ax.

[M6RV6 offline]

I like that quote, I'm always using the axe.
If your talking about.05% it's not even in the discussion but anything over your 3 Degree glide slope angle, Take down hill just about anytime unless lots of wind in your face going up hill!
My 2 cents


GT

[Zzz]

Found some good stuff on one of the EAA chapter websites:

http://www.eaa1000.av.org/technicl/take ... Slope_Corr

Of course this isn't practical to use in the field, but it can be enlightening to run some numbers from the safety of your office chair while daydreaming, to get a sense of the effect slope might have. Use your algebra to solve for the "actual takeoff" value, plugging in your "standard takeoff" value from the POH or AFM.

[Trimtab offline]

Hey Zanity

What I do if there is NO POH, much less an AFM, for my 170-B with upgrades?

Hmm

Trim

[Zzz]

Hey Zanity

What I do if there is NO POH, much less an AFM, for my 170-B with upgrades?

Hmm

Trim

I dunno? Be happy that you have a bad ass machine?

That equation above was meant to accept empirical data, written by some guy building his own flying machine and compiling his own performance data.

I imagine like most 170/180hp guys you've used the original AFM performance data and enjoyed a pleasant margin of safety.

[pitfield offline]

Thanks very much to all of you. This is exactly what I'd hoped to get.
Regards,
Chip

[Savannah-Tom offline]

Hey Zanity
What I do if there is NO POH, much less an AFM, for my 170-B with upgrades?
Hmm
Trim

I think you use the old rule of thumb that says you need to see 70% of your take off speed by the time you reach 50% of the runway length.

Here's the page that came from: http://www.allstar.fiu.edu/aero/AirPerf02.htm

It talks about all this stuff and more.

tom

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This topic split to "Optimizing fuel burn for headwind." -1SeventyZ