red slice of pie on my tach

[Flyhound]

There is a big red slice of pie on my tach that prohibits operations between about 2,000 and 2,300 RPM. I assume that is because of some weird harmonic between the McCauley prop and the Lycoming O-360 C1F engine (180 Hp). Is there another prop I can put on the plane to get that slice of RPM back? It isn't a huge imposition to keep my RPM above 2,300 in cruise, but it does reduce my options and that just frustrates me.

[Flyhound]

Ooops - I picked up the wrong prop manual in my owner's package. I've now pitched the one that says McCauley on it, and found the correct manual showing the Hartzell HC-C2YR-LBF/F7666 prop that is on the plane. The problem with that pesky RPM restriction from 2,000 - 2,250 RPM is the same though. Does that same restriction apply to any of the 235 Hp engines, or 180 Hp engines with other props?

[gbarrier]

Go to the aircraft type data sheet (3A23 Rev. 32) and find your airplane. The engines, propellers and limitations should be under that section. The propellers for 235 models for some reason are listed under note 14. Very few 235 models have any restrictions.

[Duane]

It has to do with some kind of harmonics with the 180 engine irregardless of propeller model. The C1F with a CS prop has a red arc of 2000-2250, C1F with a fixed pitch has an arc of 2150-2350. The O-320 B2D and the C4F are not affected by this.

[Flyhound]

Thanks Duane, that's what I was looking for. I was hopeful there was an STC for using another prop that would get rid of the restriction. If the engine has issues regardless of the prop, I guess I'll continue to fly below 2,000 or above 2,250 RPM. Sigh.

[Danws]

Gary. Just put an O540 in it, and forgeti it

Dan

[Maule988ms]

What about mt?

[Duane]

It doesn't matter whether TG or TD, it's a function of the engine, not the airframe.

[Maule988ms]

I didn't think mt props had that restriction

[Duane]

I'm not sure on that 988ms.

[pilot]

For some reason I'm thinking of a slice of cherry pie.

[gbarrier]

Strawberry, with lot of whipped cream.

[Njacko]

What about mt?

I've just fitted a MTV-15-D/210-58 prop to my MX-7-180 and I can confirm that the RPM restriction does not apply per page 5 of the installation manual:

"Markings and placard concerning RPM range restrictions for other propellers are obsolete."

ATB, Pete

[maules.com]

Can you give us a comparison report versus the original Hartzell including true weighed, weight difference including spinner assemblies.
It would be very good to know your experience with the change.

[Njacko]

Can you give us a comparison report versus the original Hartzell including true weighed, weight difference including spinner assemblies.
It would be very good to know your experience with the change.

The weight difference is -15 lbs at -61.3 inches. On my airplane that moved the centre of gravity aft by 20 mm (0.8 inches).

That may be a bit of a mixed blessing, because my empty CG was already quite far back (and now it is 13.8 inches) due to HSI gyro, AP control boxes and excess paint on the rear fuselage. So now I have a bit less rear PAX/baggage capacity but OTOH I may be able to dispense with rear ballast for muddy fields and for washing the tires in the local lochs. So in effect, for off-airport ops, the airplane has lost 30 lbs, or the weight of 5 gallons of gas.

Since the change I have only flown about 5 hours (of which much IFR on AP cruising back from south east England). I've hardly done any fun flying because the entire North Atlantic Ocean seems to have dumped on us in the last month.

Performance-wise it does feel different so it may take another couple of hundred landings to wring the best I can from it.

I'll report then, and as soon as I can, but it's not going to be until the new year unless you can persuade your compatriots in Florida to quit sending us their used tropical storms...