C85 Questions

[dkenney1]

One thing I have learned about the Tcraft is the manuals don't give much information. Plus mine has been upgraded to a C85-12 and metal prop. I'm trying to find out what redline on the tachometer should be. The POH says 2300 but that is for the A65, and it appears the C85 is higher but I've seen 2400 and 2500. Does anyone know? Also my tach has a white mark at around 2150, I'm assuming that's in a harmonic area, or where you should not keep it for long period of time?

If anyone has or has had a BC-12D with a C85, thanks for the info. I'd also be curious to know what your TAS is at a given power setting. I have wheel fairings and pretty clean/straight airframe and do around 105mph at 2350 rpm, and averages about 4.8gph which seems pretty good. Back at 2200 rpm about 92mph on about 3.6gph.

Lately I'm burning very little fuel due to lousy weather. Can't wait to get it in the air after a long winter. Thanks

[skip]

Re: C85 Questions

My Continental overhaul manual dated Jan 1984 lists max rpm for the C85-12 as 2575 RPM; Table V. page 12. This is also where the little hand-painted red line was painted on my Tach long ago.
I have no white line and the overhaul manual doesn't say anything about a limit, but there may be some engine/prop combination that has special limits.

N34237 is a mid-1946 BC12D with the normal C-85 STC on the long engine mount. Gross was kept at 1280, not 1500. The different weights will make a difference in speed. My flying is also all at high altitudes as my home field is at 7200 MSL, and at 8500 MSL I generally count on 102MPH true at 2400 RPM at a little under 5 gph. This from experience with lots of GPS readings cross-checked against different winds. The design is fairly clean, and it doesn't seem to loose a lot of speed with higher altitude or lower power.

Hope another data point helps

[KewFlyer]

Re: C85 Questions

4N39991 has a C-85-12 0-200 mounted on a short engine mount with a metal Sensenich prop at 74-2-CK-44 , Luscombe dual straight exhausts with a red line at 2575 RPM with 4 to 4.5 GPH cruise at 2,300 - 2,350 RPM @ 75 % power based on the chart, with a M-S Carburetor leaned short of peak RPM...some 100 MPH + -. With 24 gallons on board [ 22 useful] some 4.5 to 5 Hrs { with the fuel gage almost to the bottom.... not recommended..4 hrs is a typical flight with some allowance for reserve }. Have a white line at 2,350 for cruise.

Hope this info helps you.

ralph

[3Dreaming]

Re: C85 Questions

The white line is likely a cruise setting for the 65.

[Ragwing nut]

Re: C85 Questions

A true white line is flap speed. No harmonics on the continental

[TimHicks]

Re: C85 Questions

The Type Certificate for a TCraft with a C85 says 2575 RPM.

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/f11a5c945ba842338625747a006b2f74/$FILE/A-696.pdf