What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

RPM-MAP limitations

scrollF4

Moderator, Asst. Line Boy
Ambassador
I have a relatively new 230 tach-hour Lycoming IO-360-M1B with a newly installed Hartzell C2YK-1BF constant speed prop. Searching the documentation that came with both the engine and prop, I don't see any limitations on prop RPM/engine manifold pressure (other than a 2700 max prop RPM). Specifically, I see no ranges or combinations to avoid.

I want to be sure I don't omit appropriate ops restrictions from my POH, but am not interested in incorporating WOM (word-of-mouth) practices not backed up by factory documents.

Does the VAF brain know of RPM/MAP combination restrictions for my engine/prop combo?
 
The posts noted below from Les Doud may be of assistance.

The -M1B has no RPM/MAP limits by itself from Lycoming, unlike some of the angle valve motors that have been shown to have a lower detonation margin.

I can only speak to one -M1B and prop combo which is the 7497 BA bladed compact hub prop sold through vans.
Per one of the links below, that one has no operational limitations.

Prop limits 1

Prop limits 2
 
The Hartzell website points to Note 9 in the Type Certificate Data Sheet (TCDS) for limitations for homebuilt aircraft. I would contact Hartzell directly since the propeller TCDS does not appear to list your combination directly (see link below). But the first line on page 9 lists your prop with various parallel valve O-360s. I don't recall if the -M1B is just a parallel valve -A1A (or -B1B) with FI. That shows a limitation of "Avoid continuous operation between 2000 and 2250 RPM", but it depends also on the blade type installed on the C2YK hub.

http://rgl.faa.gov/Regulatory_and_G...d738035862580170052ad40/$FILE/P-920_Rev37.pdf

It does show the IO-360-M1B with the C2YR prop hub with F7666A blades on page 10. That shows a limitation of "Avoid continuous operation between 2000 and 2350 RPM"

Also, whether you have Mags or EI will make a difference, and EI is not covered in the TCDS.

The link above points you to the Type Certificate Data Sheet. You need to know what BLADE is used with the Hartzell hub listed. I am aware of 3 different blades that have been used with the parallel valve 360 in Hartzel hubs.

The Mother Ship has links to two documents for Hartzell Prop limitations.
F7666A blade
F7496 blade

Going from memory, the F7497 blade is the one that I would desire on a NEW RV.
 
Thanks, all, I learn more and more every day (thanks to VAF). Looks like I need to know not only the prop model number, but the blades' and hub's model numbers and serial numbers. Then contact Hartzell for the bottom line. I'm on it.

Bill Lane,
I got your email and will give Les Doud a call tomorrow.
 
This is why VAF is worth the annual donation...and much more

Many thanks to Bill Lane, who got me in touch with Les Doud at Hartzell props. Les was able to look up my prop through its serial number, thus ID'ing my exact blades and hub. That, compared to my engine, helped him determine the precise engine/prop ops limitations for my particular aircraft. According to Les:

""This propeller model at 72? on the IO-360-M1B has the following operating limitation: ?Avoid continuous operation between 2000 and 2350 RPM.? This operating limitation is referenced in TCDS P-920, Note 9 (available on the FAA website) for propellers down to 74?. I consulted with our Test Engineer and he confirmed this would also apply to 72? diameter.""

In addition, he let me know that this prop/engine combo can sustain up to a 10% rpm overshoot above the 2700 rpm redline for up to 20 seconds without need to remove and inspect.

I'm rolling these into KELLI GIRL's POH. Thanks, everyone. VAF rocks! :cool:
We're mission complete.
 
I have an IO-375-M1S (Aero Sport Power), 8.5:1, 195 hp, dual P-Mags with a Hartzell HC-C2YR-1BFP/F7497-2 prop. Since Hartzell haven't tested this combination they recommended I go with the most restrictive placard i.e..Continuous operation is prohibited above 24 inches of manifold pressure between 2350 and 2550 RPM.
 
Gerry,
Not that much. Before it was 80.75", now it's 80.61". Weight did increase, though. It went from 1161 lbs to 1185 lbs.

Let me add, though, that this as a COMPLETELY DIFFERENT airplane. Huge performance boosts in takeoff and climb, plus drastic differences in managing acceleration, closure, and especially deceleration in formation flight and formation rejoins. Cruise speeds did not change, but fuel efficiency improved by 1 to 1.5 gph depending on altitude and power levels. Ant talk about a smoother engine/prop noise level...sweet!

Totally worth the money...but did I mention that my old FP prop is for sale?

http://www.vansairforce.com/community/showthread.php?t=145975
 
Last edited:
Gerry,
Not that much. Before it was 80.75", now it's 80.61". Weight did increase, though. It went from 1161 lbs to 1185 lbs.

Let me add, though, that this as a COMPLETELY DIFFERENT airplane. Huge performance boosts in takeoff and climb, plus drastic differences in managing acceleration, closure, and especially deceleration in formation flight and formation rejoins. Cruise speeds did not change, but fuel efficiency improved by 1 to 1.5 gph depending on altitude and power levels. Ant talk about a smoother engine/prop noise level...sweet!

Totally worth the money...but did I mention that my old FP prop is for sale?

http://www.vansairforce.com/community/showthread.php?t=145975


Wow...I thought the cg would move more than that. Good to know! I have the same Sensi prop on my plane that you had (so, no, I wouldn't be looking to buy your old one lol) and concern over messing with what is right now a really good cg location on my plane is one of the things (well, that and the $10g's it would take) that has stopped me so far from converting to constant speed. Your results are encouraging. BTW, you were camped one row over from me in HBC this year; I checked your plane out but never had a chance to talk to you. Missed opportunity!
 
Gerry,
Watch for KELLI GIRL this July in HBC...she (and we) will be there. Stocked with Spotted Cow.

I will say that this new-found performance has given rise to a new issue involving pitch trim. During takeoff, the aircraft accelerates so quickly that the pitch trim motor can't keep up. I can't run it forward fast enough, so I need to pick a new takeoff trim setting, somewhere forward (faster) than before, so the airplane accelerates into the trim setting. I'll try that technique and let you know how it works.
 
...

In addition, he let me know that this prop/engine combo can sustain up to a 10% rpm overshoot above the 2700 rpm redline for up to 20 seconds without need to remove and inspect.

...

For those of you running P-mags and possibly other electronic ignitions, you can set the "Max RPM" limit which will shut off the ignition. If you have an EICOMMANDER installed, your RPM limit is set to just over 3000 RPM but lowering it is fairly simple. The standard P-mag limit is set at over 2800 RPM.
 
Back
Top