Full RPM for McCauley prop on M20C?

[phxcobraz]

Kind of an off the top of my head question I guess. The POH provides RPM settings up to 2600 RPM.

My 63 M20C has the McCauley 2D34C prop, and I generally only see about 2500-2530rpm full forward, this is confirmed with the old Mooney gauge, as well as the new digital one on my CGR30P engine monitor. Is this pretty average or is there some adjustments we could make to get closer to 2600RPM?  Higher I would think should help some for takeoff performance. 

[Ragsf15e]

15 minutes ago, phxcobraz said:

Kind of an off the top of my head question I guess. The POH provides RPM settings up to 2600 RPM.

My 63 M20C has the McCauley 2D34C prop, and I generally only see about 2500-2530rpm full forward, this is confirmed with the old Mooney gauge, as well as the new digital one on my CGR30P engine monitor. Is this pretty average or is there some adjustments we could make to get closer to 2600RPM?  Higher I would think should help some for takeoff performance. 

Is that a static runup or rolling ~50mph?  Usually static is a little lower than max, but you should be able to hit max rpm during takeoff.  
Someone will be along with the specific numbers for you.  I believe there’s a static rpm number and then obviously you want to be able to get to the max.

You can use some phone apps to check your rpm gage as well.  They work pretty well.

[Hank]

My '70 C spins a Hartzell at 2700, and the Performance Tables have 2700 at every altitude from Sea Level to 12,500 in 2500' intervals.

Sea Level shows data for 25", 26", 27" and 28" all at 2700, while 12,500 msl has data for 16", 17", 18" ans 18.3" at 2700. 

And yes, higher RPM means shorder takeoff runs and faster climb rates. I'm usually off the ground around 1000' from when I push the throttle forward.

[phxcobraz]

1 minute ago, Ragsf15e said:

Is that a static runup or rolling ~50mph?  Usually static is a little lower than max, but you should be able to hit max rpm during takeoff.  
Someone will be along with the specific numbers for you.  I believe there’s a static rpm number and then obviously you want to be able to get to the max.

You can use some phone apps to check your rpm gage as well.  They work pretty well.

This is at any time, typically full rpm use during takeoff/climb. 2530 is the highest I have seen in the 2yrs I have owned it.

[Ragsf15e]

1 minute ago, phxcobraz said:

This is at any time, typically full rpm use during takeoff/climb. 2530 is the highest I have seen in the 2yrs I have owned it.

Yeah that’s not good.  You’re gonna need to dig into that.  Step one is probably checking that gage.

[EricJ]

1 minute ago, phxcobraz said:

This is at any time, typically full rpm use during takeoff/climb. 2530 is the highest I have seen in the 2yrs I have owned it.

Something is wrong.    Your engine makes full power at 2700 rpm, so takeoffs and initial climbout should be seeing close to that.   Since 2700 is also redline, often the prop governor is set for max rpm just a little less than 2700, like 2670 or so.   If you are only seeing 2530 at takeoff, and you're sure it's accurate, that's definitely a problem.

Get an optical tach and verify that your two tachs are reading accurately.   After that you'll need a mechanic to diagnose whether there is an issue in the prop governor, prop high pitch stop, or engine.   It could be as simple as the cable isn't providing full travel to the prop governor, too, but something needs to be sorted out if the rpm is accurate.

[Ragsf15e]

6 minutes ago, phxcobraz said:

This is at any time, typically full rpm use during takeoff/climb. 2530 is the highest I have seen in the 2yrs I have owned it.

You know the airplane and have been flying it for years, so your reaction is different than mine, but if I saw that on takeoff roll vs my normal 2650 increasing to 2700, I would abort.  Granted, that could be a fine distinction on your gage.

[phxcobraz]

Just now, Ragsf15e said:

Yeah that’s not good.  You’re gonna need to dig into that.  Step one is probably checking that gage.

Confirmed by both my old Mooney gauge and the new CGR30P primary engine monitor we put in this year. No other issues really, still get off the ground in around 1000ft, climb performance at Vy is about 750-1100fpm this time of year.

[Ragsf15e]

1 minute ago, phxcobraz said:

Confirmed by both my old Mooney gauge and the new CGR30P primary engine monitor we put in this year. No other issues really, still get off the ground in around 1000ft, climb performance at Vy is about 750-1100fpm this time of year.

The takeoff and climb performance is highly dependent on weight and weather.  Also, Mooney’s performance tables were not always accurate.  It’s pretty tough to tell just from takeoff/climb if something is wrong, but if you really only see 2550, that isn’t right.

[PT20J]

Here is a summary of the procedure for McCauley props.

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.
 

[phxcobraz]

Thanks for the confirmation all, I had always suspected it seemed low but all operations have been in line and most people with the 63C seem to have the Harzell prop so never found much info. The prop control has always been a little bit finicky to stay in place, and I have had it tightened up a few times and wondering now if somehow when that was done before I owned it, the limitation was changed.

[0TreeLemur]

4 hours ago, PT20J said:

Here is a summary of the procedure for McCauley props.

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.
 

Skip, would this procedure also apply to a J model with a McCauley prop & gov?   I need to adjust the gov because it only makes 2640 max. on takeoff and climb out.

Thanks,

Fred

[Guest]

4 hours ago, phxcobraz said:

Thanks for the confirmation all, I had always suspected it seemed low but all operations have been in line and most people with the 63C seem to have the Harzell prop so never found much info. The prop control has always been a little bit finicky to stay in place, and I have had it tightened up a few times and wondering now if somehow when that was done before I owned it, the limitation was changed.

Time for a discussion with your maintainer, he should have spotted this during Annual Inspection.  
 

A few other things to check in the engine compartment, make sure that the cable is not slipping in the clamps at the governor, make sure that the end tube isn’t falling out of the end of the cable, make sure the control knob at the instrument panel has cushion, if these are good, make sure the arm is contacting the stop screw at the governor with the knob pushed full forward.  If this is making good contact, the governor requires a minor adjustment to the high speed stop screw to increase the RPM.  As noted you likely won’t make full 2700 static on the ground, but it should on the takeoff roll and climb.

[Bartman]

I downloaded a tachometer App for my iPhone and am very please with the accuracy. 

[PT20J]

2 hours ago, 0TreeLemur said:

Skip, would this procedure also apply to a J model with a McCauley prop & gov?   I need to adjust the gov because it only makes 2640 max. on takeoff and climb out.

Thanks,

Fred

Yes, it's a summary of the information in the McCauley manual. Of course, before making any changes, it's important to verify the accuracy of the tachometer. 

mpc26ow.pdf

[carusoam]

Summary…

See if I have this right…

0) Setting the stage…

Instrument error…

or power is off…

POH isn’t being used correctly…

 

1) All M20Cs have a 2700rpm red line…

2) HP is RPM dependent…

3) Sure… we can’t always get 29.92 inches of MP…

4) But, we can always get 2700rpm once moving…

 

5) Being off 100 rpm is very similar to being off by 5%… or 10hp of the excess hp variety…

if off 200 rpm… that is 10% or 20hp…

 

6) To see how important this is…

We can use the 310hp O3’s performance numbers… and compare to the 280hp O1…

Where the only difference is 200rpm, 2500 rpm vs 2700 rpm… 

turn up the dial… it becomes a whole new plane…

 

or bust out the performance charts for the M20C vs M20E… 180 vs. 200hp… (similar but really 160 vs 180)

 

7) 2500 to 2700…rpm.

8) 280hp to 310…

9) 1200’ T/O run down to 800’ T/O run…

If you are expecting 800’ and get 1200’… that is 50% more runway used than expected…!

 

10) watch the FF… if you only get 2600rpm, the max FF probably isn’t being delivered either…

 

11) Not generating full power is leaving important performance on the table…

12) There was a horrible Mooney accident of an M20K on a short runway…  it wasn’t delivering full power… the owner knew it… bags, passenger and pilot hit the berm at the end of the runway…

13) If the plane doesn’t make full power… the performance charts are not a linear adjustment… and the difference can be hundreds of feet… depending on how close to MGTW you are…

14) getting 10% more hp is worth some serious coin… 25amu roughly… for the 310hp upgrade…

15) Let’s say you bump your 2600rpm up to 2700 rpm… and check the FF, and rpm to match… 

that’s about 5% more hp for,very little coin!

16) 5% more hp will deliver better T/O runs, and climb speeds… when you need it…

17) Better when…

• runways are short
• load in the cabin is big
• DA is high

18) It is kinda odd that the OP isn’t seeing the 2700 rpm redline in the POH…  or on the tach

The charts are cruise data… where 2700rpm isn’t used…

The max power data is in the T/O section…

19) Get the latest POH available for the rest of the data…

 

20) Re-reading the OP…  2500 Max rpm?

Time to go see your maintainer… get things working properly!

Its possible your tach isn’t set up properly…

+1 for the phone app tach based on sound… low cost, makes a great comparison…

Kinda a performance check to help get the engine set up properly…

or a tach check to get the instruments set up properly…

PP thoughts only, not a mechanic.

 

My apologies in advance for sounding harsh… my writing skills are barely enough to cover the details…

Best regards,

-a-

[carusoam]

7 hours ago, phxcobraz said:

1) The POH provides RPM settings up to 2600 RPM.

2) My 63 M20C has the McCauley 2D34C prop, and I generally only see about 2500-2530rpm full forward,

3) this is confirmed with the old Mooney gauge, as well as the new digital one on my CGR30P engine monitor.
 

4) Is this pretty average or is there some adjustments we could make to get closer to 2600RPM?  Higher I would think should help some for takeoff performance. 

I’m overly concerned… 

1) your not looking in the right place for max take-off rpm setting… 2700rpm max  (2600rpm is cruise data)

2) You are only seeing 2500rpm max? You gave prop details… rpm is controlled via the govenor…

3) somebody set your new tach to read the same as a 50yr old mechanical tach?  (Might be time to re-calibrate them both)

4) Holy cow… not average.  T/O and climb rate are severely impacted… especially as we move into the warmer months…

 

I’m glad you asked the questions and detailed your thoughts…

Looks like a few minutes with a tach app can help determine how real the challenge is…

Getting it fixed up properly isn’t that hard at all…

 

Reading the POH from cover to cover… may be enlightening… there is details in there that are only written once. In the wrong place if it is needed twice…

PP thoughts only,

-a-

[phxcobraz]

9 hours ago, carusoam said:

I’m overly concerned… 

1) your not looking in the right place for max take-off rpm setting… 2700rpm max  (2600rpm is cruise data)

2) You are only seeing 2500rpm max? You gave prop details… rpm is controlled via the govenor…

3) somebody set your new tach to read the same as a 50yr old mechanical tach?  (Might be time to re-calibrate them both)

4) Holy cow… not average.  T/O and climb rate are severely impacted… especially as we move into the warmer months…

 

I’m glad you asked the questions and detailed your thoughts…

Looks like a few minutes with a tach app can help determine how real the challenge is…

Getting it fixed up properly isn’t that hard at all…

 

Reading the POH from cover to cover… may be enlightening… there is details in there that are only written once. In the wrong place if it is needed twice…

PP thoughts only,

-a-

So being a 1963 POH there isn’t much info on takeoff “settings” beyond 1 page(see attached).

Mechanic should be able to sort it out, it’s going in for a few things soon before I’ll be flying anyway. Will be nice having more climb power in summer, though I’ve flown in and out of high altitude airports since I’ve owned it and it’s been great. Goes to show the Mooney is great even if down a few 100rpm. 

[Fly Boomer]

26 minutes ago, phxcobraz said:

So being a 1963 POH there isn’t much info on takeoff “settings” beyond 1 page(see attached).

If I had bought a new Mooney in 1963, that page would have been pretty exciting.

 

[Guest]

3 minutes ago, Fly Boomer said:

If I had bought a new Mooney in 1963, that page would have been pretty exciting.

 

At the same time Mooney installed a 200 HP engine making the E model, Piper installed 400HP in a Comanche and Sweringen installed a pair of 290HP engines in a Twin Comanche.

[Fly Boomer]

7 minutes ago, M20Doc said:

At the same time Mooney installed a 200 HP engine making the E model, Piper installed 400HP in a Comanche and Sweringen installed a pair of 290HP engines in a Twin Comanche.

Oh baby, now we're talking some serious go power!

[phxcobraz]

16 minutes ago, M20Doc said:

At the same time Mooney installed a 200 HP engine making the E model, Piper installed 400HP in a Comanche and Sweringen installed a pair of 290HP engines in a Twin Comanche.

I'd love a ride in a Comanche 400, the overhaul cost is more than my Mooney is worth. 

[carusoam]

11 hours ago, phxcobraz said:

So being a 1963 POH there isn’t much info on takeoff “settings” beyond 1 page(see attached).

Mechanic should be able to sort it out, it’s going in for a few things soon before I’ll be flying anyway. Will be nice having more climb power in summer, though I’ve flown in and out of high altitude airports since I’ve owned it and it’s been great. Goes to show the Mooney is great even if down a few 100rpm. 

Note the reduce power to 2550-2600 rpm statement…

what was it reduced from?

2700rpm!

See the excerpt from an M20C POH below…

There is a ton of valuable data in the POH… without a lot of organization…

There must have been a rule to write something once, and never mention it again…

You will get rated HP of 180 at 2700 rpm…

If you don’t swing the prop at 2700 rpm… you won’t be getting the rated bhp…

Without the rated bhp… the T/O data can’t apply…

Then T/O runs get more challenging closer to MGTW, as the OATs rise, and we are any where above sea level…

PP thoughts only…

Best regards,

-a-

 

[carusoam]

To prove the whole power, weight, and T/O distance thing…

It really helps to use the CloudAhoy app to measure the actual T/O run…

Most of us will be babying the engine a bit at first, and it’s hard to tell when the plane breaks ground with any accuracy…

Combined with a WAAS source… it’s calculations are down to feet… and it displays your track over the ground exactly where you were on the runway… for comparison to your memory…

To get this level of accuracy from CloudAhoy May take paying a subscription fee… highly recommended to get a feel for the data available…

Get ready for the DA discussions as the weather warms up… 

Best regards,

-a-