EAA Sport Aviation Aircraft Performance Program

[N1277D]

In the December 2002 issue of Sport Aviation their is an article on aircraft performance. It also includes a spreadsheet (downloadable from - http://www.eaa.org) where one can estimate a design's performance. I put in some numbers for the 170 into the spreadsheet and it seemed to be in agreement with the C170 book numbers after inputing an estimate for the flat plat drag area and the lift coefficients. I ran some different prop engine combinations and the results looked reasonable. Here are some of the results at 2200 lbs for rate of climb and take off distance at sea level and 59F.

FPP - Fixed Pitch Prop
CSP - Constant Speed Prop
ROC - Rate of Climb in fpm
TO - Take off distance on pavement over a 50 ft obsticle

C145 (145 hp)
FPP (ROC - 690 fpm, TO - 1,620 ft) CSP (ROC - 890 fpm TO - 1,104 ft)

O320 (160 hp)
FPP (ROC - 830 TO - 1,380) CSP (ROC - 1,040 TO - 975)

O360 (180 hp)
FPP (ROC - 1,000 fpm TO - 1,180 ft) CSP (ROC - 1,250 fpm TO - 850 ft)

IO-360 (210 hp)
FPP (ROC - 1,300 TO - 973) CSP (ROC - 1,550 TO - 724)

Franklin (220 hp)
FPP (ROC - 1,350 fpm TO - 922 ft) CSP (ROC - 1,650 fpm TO - 690 ft)

I also ran some number with the C145 at 2,000 lbs since the higher hp conversions seem to add about 200lbs to the empty weight. The numbers are:

C145 (145 hp @ 2,000lbs)
FPP (ROC - 810 fpm TO - 1,300 ft) CSP (ROC - 1,040 fpm TO - 900 ft)

Based on these results the addition of a constant speed prop to the C145 would approximately increase the rate of climb by 200 fpm and reduce the takeoff distance over a 50 ft tree by about 400 to 500 feet. It looks to be roughly equilivant to an O360 conversion with a fixed pitch prop, or an O360 with a constant speed prop and a very poor exhaust system (157 hp).

[N170BP]

Those numbers look close enough to be awarded a cigar.
Especially the last set.

With just me on board and light fuel (less than half tanks),
& with my 51 pitch prop, I see right around a 1000 FPM
initial climb rate on what you might call a "close to standard day"
(atmospheric pressure & temp.).

Bela P. Havasreti
'54 C-170B N170BP

[Dave Clark]

WAY COOL! There's nothin like horsepower. I don't know that my stock setup with a 76/53 ever did 690 fpm at gross at sea level though. More like 500 maybe. The conversion progresses but slowly.