The International Cessna 170 Association

Thanks Bruce.
One piece of information I didn’t say was that the prop was originally stamped 7653. It looks like they took a center punch and punched the 53 out then stamped 48 below where the 53 was originally stamped. So I guess that means it was re-pitched .

I do not understand how to determine static rpm ! I’ve read in the POH that max rpm is 2700. To the best of my knowledge at full throttle in level flight I’ve never seen over 2400 to 2500 rpm. I just thought it was a tach issue.

Like I said , I’m still learning all of this stuff.

RealCowboyPilot wrote:Thanks Bruce.
One piece of information I didn’t say was that the prop was originally stamped 7653. It looks like they took a center punch and punched the 53 out then stamped 48 below where the 53 was originally stamped. So I guess that means it was re-pitched .

I do not understand how to determine static rpm ! I’ve read in the POH that max rpm is 2700. To the best of my knowledge at full throttle in level flight I’ve never seen over 2400 to 2500 rpm. I just thought it was a tach issue.

Like I said , I’m still learning all of this stuff.

The -over-stamp indicates the prop has been re-pitched. (Do you not have any prop records on this prop?)

Static RPM is…. Standard Atmospheric conditions (Sea Level, Baro: 29.92”, 15-degrees C.)… full power with brakes held…. with an accurate tachometer…the acceptable RPM limits are 2230-2330 RPM.

Thanks George,
I do have a prop log book. Have not studied it but will. With these temps we are having in Texas it will be December before it gets cool enough to do a static rpm check !

Done a quick review of logs.
Trying to speed read through the chicken scratch of many years I found no entry of propeller being reshaped.
IA’s doing annuals in the past were not very attentive to what they were doing. On prop inspection they said it was a 7651 and it is clearly over stamped a 7648. I’ve got a clear picture of the stamp and it was originally stamped 7653.
The IA that did my annual this year informed me that I had a climb prop and that was all that was said other than it wold have to be re-inspected soon.
Not sure of that cost so I guess I need to bite the bullet and buy a new prop.

Only our IA could say why you'd have to have the prop inspected soon. There is no time table for required simple fixed pitch prop inspections other than routine preflight inspections and then annual condition inspections.

George gave you the text book definition of a Static RPM check. But you may not have many of those days to do the check. However going out on the ramp and facing into the wind with nothing blocking the air behind you such as a hangar, go to full throttle and recording your RPM can give you valuable information to access, taking the non-standard conditions (which you should also record) into account.

Assuming you don't do this under extreme ends of atmospheric conditions and you find your are well within or well out of allowable RPM range you probably are. If you find your on the edge of a limit then atmospheric conditions will come into play as to whether you have a legal installation or not.

When I first got my 55 170B I was having trouble making the minimum static RPM. The prop that was on the plane was a DM7653 that had been repitched to a 55. While on the phone with McCauley, the tech told me I should be leaning for full power while doing the static run up (which I hadn't been doing). I don't recall if leaning during subsequent tests made much difference in RPM.

Ultimately, the prop failed inspection due to corrosion and I purchased a used DM7651 from another association member and all is well.