The International Cessna^® 170 Association

For full power static run- up what RPM would you consider accepatble?? I have been checking this out with my AME and we are getting 2350. He feels higher would be better. Any thoughts would be appreciated. Thanks Gary

simatos wrote:For full power static run- up what RPM would you consider accepatble?? I have been checking this out with my AME and we are getting 2350. He feels higher would be better. Any thoughts would be appreciated. Thanks Gary

Check the TCDS At FAA.gov (A-799)

http://www.airweb.faa.gov/Regulatory_an ... /A-799.pdf

Look under propellers for the RPM spec's
2330-2230 for a Land plane
Regardless at which pitch???
Jim

It's also available on this site in the members section. http://cessna170.org/phpBB2/membersOnly ... _Rev54.pdf

It depends on the prop you have. If your AME doesn't know that information is in the TCDS I would seriously question his qualifications.

Under Note 1:
Propellers and Propeller Accessories 1. Propeller (a) McCauley 1A170 Static r.p.m. at max. permissible throttle setting: Landplane: Not over 2330, not under 2230 Seaplane (Models 170A and 170B): Not over 2525, not under 2300.

Make sure your tach is accurate.

Maybe someone can give some input in the same subject. My tach is only reading 2000 rpm during the static test. I just had my carb overhauled because of some loss of power experiences . Anyway, since I've only flown about 5 hours since I picked it up, I do not have a baseline on what the tach read before hand during a static test. I just came back from the airport and had the mechanic test the rpm with an optical tach reading from the prop. The most we can get is about 2150. I pulled the spinner last week and verified the prop (McCauley 1A170 DM7653). A call to McCauley verified that it is a standard prop on the bird. Does anyone have any ideas or am worrying about nothing? As a side note, the engine sounds great and compressions where checked (72/80). Maybe I am just being paranoid, but when the warm weather gets here and the short fields open up, I want all I can get

Thanks,

Paul

Your engine really seems pretty short on turns (rpm) on a static run up. That is the only way you can determine the power on an installed engine. Are you confident that the ignition timing is correct and the plugs are in good shape? I have often found that mechanics that are not familiar with the O-300 engine do not time it properly and sometimes screw up the ignition harness set up. It is different than other engines.

Thanks. The harness is was installed in 1973 and has over 600 hours on it. Maybe I should replace it because of age/time? As a side note, I have been an auto mechanic for close to 30 years and can understand working on systems a person is not familiar with I have been getting a huge amount of new mechanical knowledge since I now own a hole in the sky to through money into

I may have to recheck the mag timing and maybe put a new set of plugs and wires in it (can I do this under maintenance?). I think that I can.

Thanks again,

Paul

As the owner operator, with at least a private ticket, you can replace spark plugs, check the mag timing (but not adjust) but replacing the ignition harness isn't on the list. Of course I would never work on my airplane illegally

The list of owner allowed preventive maintenance chores is found under FAR 43.3. appendix A. Russ Farris

What Dick is refering to is the fact that on the C-145/O-300, the left mags fire the bottom plugs and the right mag the top. Most engine criss cross
e.g., left mag fires bottom left bank of cylinders and top right.
Check your engine on this, to be legal.

If it were me, I would defintely replace the harness after 33 years. Any idea how old your plugs are? Anything over about 400 too 500 hours can cause problems. Russ Farris

Remember, also, that the mags on our engine do not fire simultaneously. There is a two degree spread.

Keep in mind that the temperature effects the static RPM. On a cold day the static RPM will be significantly lower than on a standard day, even though the engine is actually producing more power.

"Keep in mind that the temperature effects the static RPM. On a cold day the static RPM will be significantly lower than on a standard day, even though the engine is actually producing more power."

Can you expand on that a little more? Is it because the air being denser will create more "drag" on the prop which in turn lowers RPM? I would think that the increase of air density should increase engine horsepower which would compensate for this. Just speculating as I am by no means any kind of rocket scientist

Paul

Both the engine and the prop are working with more dense air but the prop is working with a larger volume of it.

Thanks for all the input. I think that we may have found the "problem". The mechanic from the FBO called this morning. According to the stamping on the prop, it should be a standard prop, but the actual pitch on the prop is pitched as a cruise prop. I don't have the figures in front of me. We think that someone rebuilt this prop and changed the pitch to a cruise prop without stamping the changed pitch on the prop. I am going to fly it this way for now, but may send the prop in this spring and see if they can repitch it back or better yet, repitch it to a climb prop. I'll let everyone know how it turns out.

As a side note - thanks for the great resource. I have learned a TREMENDOUS amount of information since becoming a member. I hope that as the years pass, I get to meet some of you!

Paul
N3458D

For all-around use (including grass/short strips) I really like my 76-51. I believe any more pitch would compromise takeoff and climb performance. I can still attain 120-ish cruise speed -- I turn it up around 2550 I want to get somewhere, it seems to like it.

Eric