High-RPM prop stop question

BigBadLou

BigBadLou

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Lou
Greetings,

my mechanic told me last night that my constant-speed propeller should not allow my engine to get up to the redline RPM (2700 by the book) while stopped. They call it "static RPM" and he says that it should be around 2500.
I checked the PoH and it does not mention static RPM or any other RPM check.
Where can I find this information?

My mechanic says that the flat-pitch stop should be adjusted to lower the static RPM.
Sure, I don't mind. But I must wonder why one would want to limit the RPM while not in motion, let's say at the beginning of ground roll for takeoff. Is there a benefit to it? (I cannot think of one but then again, I am not a mechanic or engine designer)

Thanks in advance for good information.
Lou
 
Most I've seen will go all the way to the redline that's on the tac, not past that through.

What plane and engine?
 
mine will not do redline at static.....once on the roll (~40kts) the prop does come off the low pitch stops and redlines at 2,700 rpm.

I have a TSIO-520-D with a three blade McCauley prop.
 
Some will reach redline static, some will come close and only reach it in the takeoff roll. 2500 for a 2700 RPM redline is too low. Sounds like maybe the low-pitch stops in the prop aren't set properly.
 
Where would one find the static RPM information? I downloaded some maintenance manuals but they do not disclose that information either.
 
Prop pitch limits are listed in the TCDS. Redline RPM is determined by the prop governor. Static RPM isn't an important value with CS props since it would change with blade length, number of blades, etc. Static RPM is important for fixed pitch props and the TCDS info for my Cubs (for example) includes static RPM limits.
 
Last edited:
Your mechanic is correct. A static run with constant speed prop should NEVER reach red line.

"""""NOTE: On static runs, the propeller should prevent the engine RPM from going to red
line. This is done to prevent overspeeding and is a design characteristic of the
propeller. However, it should be within 100 RPM of red line."""""

Pg 102 http://www.mccauley.textron.com/mpc26ow.pdf
 
Depends on the engine prop combination....some CS will....some CS will not reach redline at static.
 
And.......Unless you are checking RPM with some kind of digital tachometer.......you have no idea of the actual RPM.
 
BigBadLou said:
Greetings,

my mechanic told me last night that my constant-speed propeller should not allow my engine to get up to the redline RPM (2700 by the book) while stopped. They call it "static RPM" and he says that it should be around 2500.
I checked the PoH and it does not mention static RPM or any other RPM check.
Where can I find this information?

My mechanic says that the flat-pitch stop should be adjusted to lower the static RPM.
Sure, I don't mind. But I must wonder why one would want to limit the RPM while not in motion, let's say at the beginning of ground roll for takeoff. Is there a benefit to it? (I cannot think of one but then again, I am not a mechanic or engine designer)

Thanks in advance for good information.
Lou
Click to expand...

Like most form questions you didn't say make model year/serial number...
 
kgruber said:
Your mechanic is correct. A static run with constant speed prop should NEVER reach red line.

"""""NOTE: On static runs, the propeller should prevent the engine RPM from going to red
line. This is done to prevent overspeeding and is a design characteristic of the
propeller. However, it should be within 100 RPM of red line."""""

Pg 102 http://www.mccauley.textron.com/mpc26ow.pdf
Click to expand...
Thank you, sir.
Yes, static RPM is within 100 of redline. Good to know.
 
bnt83 said:
Like most form questions you didn't say make model year/serial number...
Click to expand...
There wasn't a need. I didn't ask for the magic number itself, I inquired where one might find it in general, since my PoH does not disclose it.

bnt83 said:
See above

While everyone shoots from the hip... I found this in Cessna document #D991-3-13 with temporary change 1 thru 4 in it.
Click to expand...
But you found it anyway, perfect.
Thank you very much!
 
From McCauley's web site:

The information in this guide is intended for general reference use only. The procedures explained in this guide may not be applicable for your installation. If any question exists regarding these procedures, contact McCauley Product Support at 1-800-621-7767.

Always consult the aircraft Type Certificate Data Sheet or owner/operator's handbook before modification to governor or installation

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.
 
and the kicker is if you look up your engine on the Lycoming website you will most likely find that 2900 is the red line for the engine. Then figure out what diameter blades your prop have and you will find that it would be 3200 RPM for your prop tips to go supersonic. The type data sheet was probably not updated (too much testing to recertify) between the 180 hp and the 200 hp. Or they wanted to keep it under the random 200 HP so you would not need a HP endorsement.
 
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