McCauley 7142 Kliptip Prop on a65??

[zipperdu]

I've just purchased a 7AC with an a-65, it has the metal McCauley prop- I've tried to find documentation for approval....anybody have experance with this??

[Captgrumps]

If it is a McCauley 1B90CM the specs for a A65 are
Diameter not over 74"
Diameter not under 72.5"

Static RPM not over 2250
Static RPM not under 2100

It should turn up like a buzz saw.


That prop sounds like a 85hp prop --I have a 1B90/CM 7144 on my 85 hp Champ.

Doug

[zipperdu]

Hey Doug,

Thanks for the info- to say that it turns like a buzz saw sums it up pretty well.....
silly thing is that it's been on for years!

Jon

[MikeB]

For whatever it's worth, all three of the 65 Champs on our field have McCauly 1BM90/CM7443. I can run static around 21-2150 on mine.

Mike

[Paul Agaliotis]

Jon,
This one of those areas that gets a little tricky.

The TCDS for the 7AC gives you the limits that Doug posted. Which leads you to conclude that the prop is too short for a 1B90 on an 7AC but good for a 1A90 on the same airplane. But when you go to the TCDS for the prop, P-842, it allows a minimum length of 69 1/2 for both props on the A65. To further confuse the situation Note 6 tells you the props are so similar that they are completely interchangeable in diameter and static limits with no test flight required.

If everyone involved with the plane is satisfied with the performance and the max RPM is not exceeded I wouldn't worry too much about it.
Paul

[Mikek]

Hey Doug,

Thanks for the info- to say that it turns like a buzz saw sums it up pretty well.....
silly thing is that it's been on for years!

Jon

I have a McCauley 7142 kliptip on my 7AC with the A-75 which gives me 2600 rpm max RPM

[Captgrumps]

This one of those things like a starter on a C85-12--legal--but the wire from the battery that powers the nav lights (legal) or the GPS (not mentioned) isn't to the starter (to eliminate hand propping--which can be dangerous and hazardous to your health--and illegal in some gov't funded airports). All are safety items subject to paper cuts due to governmental lack of experience..Let common sense prevail. I'll bet 99% of improvements on old airplanes are aren't within the age old TCDS.

Doug

[zipperdu]

Hey, thanks to all......
fact is the prop does overspeed in flight and FTSR is above limits also...
a new Sensenich Wood prop is on the way.

Jon

[Mikek]

Hey, thanks to all......
fact is the prop does overspeed in flight and FTSR is above limits also...
a new Sensenich Wood prop is on the way.

Jon

Would you want to sale or trade that prop?

mknemeyer@gmail.com

[Larry]

Some information that I found some years ago said:

1B90 7146 is a climb prop
1B90 7148 is a standard pitch
1B90 7150 is a cruise prop

Remember, static RPM requirements are specified for Sea Level, Standard Day. As they say, "Your actual RPM may vary depending upon your conditions". If you can find the TCM chart for your engine, you can see the HP curve vs. RPM which shows that my C85 is only developing about 60 HP up here at my 6400 MSL airport on a summer day.

A Merry Christmas to everyone on the forum, and a Safe New Year while flying our Aeronca antiques.