RPM at rotation speed?

[Joe Larussa]

Just switched from a McCauley C212 to a C214 prop. Static run up full throttle was 2630 and 2660 on takeoff roll at 71 mph, rotation speed. Should I be hitting 2700 ?

[T. Peterson]

8 minutes ago, Joe Larussa said:

Just switched from a McCauley C212 to a C214 prop. Static run up full throttle was 2630 and 2660 on takeoff roll at 71 mph, rotation speed. Should I be hitting 2700 ?

I get almost identical numbers. It never concerned me…..maybe it should???? I hope not.

[Joe Larussa]

4 minutes ago, T. Peterson said:

I get almost identical numbers. It never concerned me…..maybe it should???? I hope not.

 I hear you can adjust it with the prop governor. I’m getting 20 more with new prop. Just wondering if I should leave it alone.

[RobertGary1]

Never thought to look at the tach while rotating

[Guest]

36 minutes ago, Joe Larussa said:

Just switched from a McCauley C212 to a C214 prop. Static run up full throttle was 2630 and 2660 on takeoff roll at 71 mph, rotation speed. Should I be hitting 2700 ?

Your governor requires a small adjustment of the high speed stop screw, likely 1/2-3/4 turn.

[Joe Larussa]

1 minute ago, M20Doc said:

Your governor requires a small adjustment of the high speed stop screw, likely 1/2-3/4 turn.

Do you think it’s worth messing with for 40 rpm?

[T. Peterson]

2 minutes ago, M20Doc said:

Your governor requires a small adjustment of the high speed stop screw, likely 1/2-3/4 turn.

That probably goes for me too. One more thing…

[T. Peterson]

21 minutes ago, Joe Larussa said:

 I hear you can adjust it with the prop governor. I’m getting 20 more with new prop. Just wondering if I should leave it alone.

Clarence answered that question for us. Sure wish he was in Texas!!

[Guest]

6 minutes ago, Joe Larussa said:

Do you think it’s worth messing with for 40 rpm?

It’s a judgment call.  Performance charts are based on full RPM, you’d hate to clip to top of a tree on takeoff someday. “I just hit a little bit of the tree because my RPM was just a bit low”

[Niko182]

18 minutes ago, Joe Larussa said:

Do you think it’s worth messing with for 40 rpm?

Yes. I do. full rpm makes a difference. Even if it is small.

[PT20J]

Is it a digital tach? If not, I would check the tach accuracy first before adjusting anything. Here's the McCauley procedure:

General Calibration Procedures Following Installation of McCauley Constant Speed Governors

A. Perform Static Run-up: Lock aircraft brakes. Place cockpit propeller RPM lever in high RPM (takeoff) position. Advance throttle slowly to maximum permitted engine manifold pressure limits. Record propeller RPM. If local wind conditions are over 5 knots, repeat check with aircraft pointed in opposite direction and average the two numbers. As a general rule, propeller RPM should be 25-100 RPM below redline limit during the above check.

B. Perform Flight Test: During takeoff acceleration, record maximum propeller RPM. When sufficient altitude is reached, level out aircraft, leaving propeller control in full RPM position. Maintain this setting for three (3) to five (5) minutes while monitoring propeller RPM. Following this check, two conditions may exist which require adjustment:

1) If propeller RPM is exceeding redline limit, reduce it to redline using propeller control. Leaving propeller at this redline RPM setting, land aircraft and shutdown. Remove cowling and note position of control arm on governor. Adjust governor high RPM screw clockwise so it just touches stop on governor control arm; this will ensure that the correct arm position for governor redline RPM setting cannot be exceeded.

2) If propeller RPM is below redline limit with max RPM setting on the propeller cockpit control, note RPM and land. Remove engine cowling and adjust the governor high RPM screw counterclockwise to increase RPM.

Note that one full screw turn will cause an increase of approximately 25 RPM.

Perform another test flight to confirm adjustments were sufficient.

General Facts About McCauley Governors

Static Run-Up - What is Normal?

There has been some confusion in the field concerning propeller low blade angle setting, the governor setting and how it relates to static run-up and take-off RPM. As a general rule, engine redline RPM cannot be reached during a full power static run-up. Contrary to popular belief, the governor is not controlling the propeller at this time, the propeller is against its low pitch stop. Attempting to increase propeller static run-up RPM by adjusting the governor high RPM screw will have no effect and will probably result in a propeller overspeed during the take-off roll. On a single engine aircraft several considerations determine both the low and high blade angle settings. Normally 25 to 100 RPM below rated take-off RPM is desirable and acceptable during a static run-up. McCauley's practice is to set the low blade angle so that rated take-off RPM is not reached until the aircraft has reached some significant groundspeed during roll out. At this time, and only this time, the propeller is controlled by the governor. There are two advantages to this practice. First, the maximum static RPM can be used as a check on developed horsepower as with a fixed pitch propeller. Any loss of maximum power over time is readily apparent during a preflight check. Second, if the propeller remains in a flat pitch after take-off due to some malfunction, the higher angle low pitch setting will permit more thrust to be developed to fly the aircraft without overspeeding the engine.

[Niko182]

If you want a quick way to know the tach is somewhat accurate, take an iphone out and record the prop at 2400rpm. The prop should look like it isn't moving at all. if your tach is showing right around 2400rpm and the prop looks like its stationary, you're probably good on the tach being fairly accurate.

[Pinecone]

https://apps.apple.com/us/app/strobe-tachometer-rpm-meter/id831460940

iPhone Strobe tach to measure RPM.

[Joe Larussa]

13 hours ago, PT20J said:

Is it a digital tach? If not, I would check the tach accuracy first before adjusting anything. Here's the McCauley procedure:

General Calibration Procedures Following Installation of McCauley Constant Speed Governors

A. Perform Static Run-up: Lock aircraft brakes. Place cockpit propeller RPM lever in high RPM (takeoff) position. Advance throttle slowly to maximum permitted engine manifold pressure limits. Record propeller RPM. If local wind conditions are over 5 knots, repeat check with aircraft pointed in opposite direction and average the two numbers. As a general rule, propeller RPM should be 25-100 RPM below redline limit during the above check.

B. Perform Flight Test: During takeoff acceleration, record maximum propeller RPM. When sufficient altitude is reached, level out aircraft, leaving propeller control in full RPM position. Maintain this setting for three (3) to five (5) minutes while monitoring propeller RPM. Following this check, two conditions may exist which require adjustment:

1) If propeller RPM is exceeding redline limit, reduce it to redline using propeller control. Leaving propeller at this redline RPM setting, land aircraft and shutdown. Remove cowling and note position of control arm on governor. Adjust governor high RPM screw clockwise so it just touches stop on governor control arm; this will ensure that the correct arm position for governor redline RPM setting cannot be exceeded.

2) If propeller RPM is below redline limit with max RPM setting on the propeller cockpit control, note RPM and land. Remove engine cowling and adjust the governor high RPM screw counterclockwise to increase RPM.

Note that one full screw turn will cause an increase of approximately 25 RPM.

Perform another test flight to confirm adjustments were sufficient.

General Facts About McCauley Governors

Static Run-Up - What is Normal?

There has been some confusion in the field concerning propeller low blade angle setting, the governor setting and how it relates to static run-up and take-off RPM. As a general rule, engine redline RPM cannot be reached during a full power static run-up. Contrary to popular belief, the governor is not controlling the propeller at this time, the propeller is against its low pitch stop. Attempting to increase propeller static run-up RPM by adjusting the governor high RPM screw will have no effect and will probably result in a propeller overspeed during the take-off roll. On a single engine aircraft several considerations determine both the low and high blade angle settings. Normally 25 to 100 RPM below rated take-off RPM is desirable and acceptable during a static run-up. McCauley's practice is to set the low blade angle so that rated take-off RPM is not reached until the aircraft has reached some significant groundspeed during roll out. At this time, and only this time, the propeller is controlled by the governor. There are two advantages to this practice. First, the maximum static RPM can be used as a check on developed horsepower as with a fixed pitch propeller. Any loss of maximum power over time is readily apparent during a preflight check. Second, if the propeller remains in a flat pitch after take-off due to some malfunction, the higher angle low pitch setting will permit more thrust to be developed to fly the aircraft without overspeeding the engine.

I have two digital tach's and both are within 10 RMP of each other. Thanks for all the info!!!!

[RobertGary1]

17 hours ago, M20Doc said:

It’s a judgment call.  Performance charts are based on full RPM, you’d hate to clip to top of a tree on takeoff someday. “I just hit a little bit of the tree because my RPM was just a bit low”

I know people who intentionally set it high for high density take offs but just otherwise take off with the prop pulled back slightly 

[jlunseth]

Well, before I had my JPI930 installed the RPMs looked just fine to me. Then the 930 went in. The sensor and the 930’s readout ability is vastly better than the old factory analog gauge. So for years I would see just a slight over speed at takeoff. Say 2710 or 20. Then it would settle back. We tried fiddling with the governor screw but there was always about a 30 or 40 rpm variation at the top end. When it went over 2700 (the redline) I would usually try to adjust it back with the prop knob, but adjusting out just 10 or 20 rpms does not work very well. Now I max out at about 2680, with the speed sometimes as low as 60 or even 50. It is in the realm where we really can’t adjust the governor to exactly 2700, in light of the sensitivity of the sensor and JPI there is always a little variation.

[T. Peterson]

22 hours ago, M20Doc said:

It’s a judgment call.  Performance charts are based on full RPM, you’d hate to clip to top of a tree on takeoff someday. “I just hit a little bit of the tree because my RPM was just a bit low”

I am just curious. How many inches of tree per revolution?

[Guest]

6 minutes ago, T. Peterson said:

I am just curious. How many inches of tree per revolution?

Canadian maple or southern pine?