Need help with Rocket, high MP and LOW RPM on static run.

[Austintatious]

Hello everyone...

A maintenance facility is having trouble after an engine install...  They are unable to get the Manifold pressure down from 39" to the prescribed 38".  This is a brand new turbo and an overhauled controller.

Furthermore, they cannot get the RPM up to 2650 on a static run... they were able to get it from 2550 to 2600, but cannot get the last 50 RPM.  This is a brand new propeller and prop governor.  It is unlikely the prop governor because we took one off another rocket that was making full RPM in static run and put it on... still low RPM.  The prop had even been taken off and sent BACK to a prop shop for an inspection to eliminate it as a cause.

 

Everyone seems to be at a loss as to what to do now.  We seem to be completely stuck.  any ideas greatly appreciated.

 

 

[A64Pilot]

I think the prop shop will find your RPM issue.

Wait you said they have already had it? Sorry, never mind

Edited August 23, 2021 by A64Pilot

[Will.iam]

Is the prop governor have you adjusted the prop governor to it’s maximum limit? Just because the governor was making correct RPM on another aircraft doesn’t mean you will not need to adjust the governor on this aircraft. I had an AD on my prop governor and had to send it in to get different bearings replaced and it was still under warranty because it was less than a year old. They did not change or adjust my maximum RPM set screw but when i got it back and reinstalled it on my airplane it was 150 RPM low so i had to readjust the set screw.   

[smwash02]

I don't know the procedure for the Rocket, but with the Ks the MP is set with the oil at 180F. Less than that it will be high per the service manual. On the stock K there's a manual adjustment on top.

RPM wise -- how are you measuring the RPM?

[carusoam]

Hey Austin!

Make sure you have the set-up manual for the Rocket’s specific engine… (PP guessing…)

Our prop guy flys a Rocket… @Cody Stallings

Best regards,

-a-

[PJClark]

Agree on @Cody Stallings.

And ditto on being sure you're following the Rocket setup instructions (they're in the STC install manual). Anything else and you're doing the wrong things (including if you're trying to use Continental SID-97....won't work. STC takes precedence I'm told). (learned by experience).

I should have added: If you do not have the Rocket stuff PM me and I'll send you scans of the relevant pages.

[Guest]

Knowing the propeller type would be helpful.  Fine pitch stops on McCauley props can not be adjusted in the field, whereas Hartzell props can.

Clarence

 

[PJClark]

It's a McCauley if it's a vanilla Rocket. I know there's someone (maybe @aviatoreb) who's put on an MT 4-blade, and @Cody Stallingsmay have added a featherable scimitar Hartzell to his.  But the Rocket STC added a big McCauley.

[Austintatious]

Thank you everyone... I think I do have the rocket STC paperwork...  PJclark, if you have it handy, an electronic version would be really awesome... Ill owe you a beer!

 

My email address is Austinswill@gmail.com

Edited August 25, 2021 by Austintatious

[Stetson20]

My Rocket is in annual right now, so I'm paying attention to this thread. Love MooneySpace!

[PJClark]

@Austintatious I guess mine is still in the Rocket since Annual, hard copy. I'll have to run out there and get it and scan the engine setup pages. It's in the Maintenance manual, not the STC installation manual if you have them both.

[A64Pilot]

22 hours ago, Austintatious said:

Thank you everyone... I think I do have the rocket STC paperwork...  PJclark, if you have it handy, an electronic version would be really awesome... Ill owe you a beer!

 

My email address is Austinswill@gmail.com

I would edit my post and remove the email address, send it via a PM, there are bots or something that somehow harvest email addresses, it’s above my head but smarter people have told me it’s true.

[Austintatious]

4 hours ago, PJClark said:

@Austintatious I guess mine is still in the Rocket since Annual, hard copy. I'll have to run out there and get it and scan the engine setup pages. It's in the Maintenance manual, not the STC installation manual if you have them both.

I would greatly appreciate it!

[PJClark]

K, tomorrow 

[Cody Stallings]

I don’t Have a Hartzell on my Rocket yet, but a STC for one sure sounds good.

Your Rocket Sir just like every other Non -MT Converted planes will have a McCauley C505 CS/Feathering propeller, an it has No external pitch change provision.

Have actually seen an issue like this but it wasn’t on a Mooney, Fortunately for us though it was on a Cessna 414 Chancellor

New engine(reman) an O/H Propeller, High MP an Low RPM

At the end of the day it ended up being the oil transfer bearing in this guys situation, there was to much clearance when the engine was assembled.

With the Feathering Propeller you have what’s called a Latch or Start-Lock, this is in place to keep your propeller from going to feather at shutdown. The Latch angle is normally in the 3 to 5 degrees more aggressive that your low pitch(takeoff blade angle).

So at startup your propeller has to get 3-5 degrees flatter to makes its published blade  angles, which means fully compressing two giant springs that when not installed are almost as long as one of the propellers blades,(will provide some pictures below)takes a lot of pressure for this to happen. 

If your not able to flatten the prop out at startup that will yield a higher than normal MP followed by a lower RPM because you have to much Angle. The engine is normally sluggish to spool up an won’t get near the book RPM, but it will buildup RPM 300ft or so on the takeoff roll.

The problem was found with a pressure decay test between the Governor an propeller. The Gov comes off an a block off plate is installed where air pressure is used to actuate the prop an measure how long it takes for the pressure to decay. 
If the decay is to much the Hydraulic system can overcome the Cwt Weight an Spring forces to acquire Low pitch.

These props require a lot of pressure to actuate.

[carusoam]

Wow! Cody you have done it again…

Showed proof that I didn’t know what I didn’t know about propellers…. 

I’m glad you share these details so often…

Best regards,

-a-

[PJClark]

Rocket engine service manual attached as two scans--it's printed both sides and my home scanner doesn't do that. Odd pages are in order front to back...sorry but even pages are in order back to front.

Rocket MX manual ODD pages.pdf Rocket MX Manual EVEN pages.pdf