Performance question C172

highflying

New Member
I dont know why I am having trouble with this but can someone help me with this question.

At 65% power, 7500 feet, standard temperature what is your

RPM, Fuel Consumption, TAS?

If yo can explain to me how you got it that would be great also. Thanks for the help
 

MidlifeFlyer

Well-Known Member
[ QUOTE ]
I don't know why I am having trouble with this but can someone help me with this question.

At 65% power, 7500 feet, standard temperature what is your

RPM, Fuel Consumption, TAS?

If yo can explain to me how you got it that would be great also. Thanks for the help

[/ QUOTE ]I don't have a POH or PIM handy, but if I remember correctly, the cruise performance charts are pretty easy to read. How far have you gotten?
 

highflying

New Member
Well not to far. I mean I know how to use the performance charts but I can seem to figure out the 65% power. I mean if I could figure that out then the rest would be easy at least I think
 

jetman

New Member
From 172P POH

6000...63%..2400RPM 107ktas 7.0gph
69% 2500 rpm 113ktas 7.8 gph

At what rpm u would find 65%? from the chart u c that 6% rpm difference corresponds to 100rpm so 2% = about 35rpm
or 2435 rpm[65%]
Speed seems to increase 1k per 1% of increase power so at 65% 109 ktas and so goes for fuel about7.3 gph

8000...66%..2500 rpm.112 ktas....7.4gph
if u want to be exact u should use the 60% values and interpolate [ 2400 rpm106k 6.7g]and come up with something like
8000 65% 2485 rpm111ktas 7.3gph]

6000 65%2435rpm 109kktas 7.3gph
8000 65%2485 rpm 111ktas 7.3gph
Divide all the values by 4to find diff for avery 500ft and substract from the 8000 ft values [8000-500=7500ft]
2470rpm...110.5ktas
7.3gph
Good luck /// [ double check numbers calculations where done in my very tired head
in a hurry ]
 

highflying

New Member
Thanks for the help. I thought that was how you do it but I wanted to make sure there wasnt an easier way before I started do all the math work. Thanks again!!
 
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