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RPM Restrictions -ILS

slowflyin

By slowflyin
in Vintage Mooneys (pre-J models)

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slowflyin Mentor

slowflyin

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I've been trying to refine my "flying by the numbers" and have found this forum and the MAP manual invaluable.  However, I'm having trouble implementing all the great info regarding IFR approach settings while respecting my 2000-2350 rpm restriction.  It seems anything below 14.5-14.75" of MP puts me in the red.  Any advice?  Thanks in advance.

 

PS-M20F 

slowflyin Mentor

slowflyin

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During an IFR approach while running down hill on the GS.  15 yields around 95-100 kts with flaps at approach.   The MAPA manual and others have suggested 13 inches while on the glide slope.

MooneyBob Mentor

MooneyBob

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Posted

I don't remember exactly what my place card says but I think the RPM restriction applies over 80 knots and for longer period of time. I might be wrong.

HRM Grand Master

HRM

Posted
Posted

I've been trying to refine my "flying by the numbers" and have found this forum and the MAP manual invaluable.  However, I'm having trouble implementing all the great info regarding IFR approach settings while respecting my 2000-2350 rpm restriction.  It seems anything below 14.5-14.75" of MP puts me in the red.  Any advice?  Thanks in advance.

 

PS-M20F 

 

I believe the wording is avoid continuous operation. That means, stay out of there during cruise. Landing, which other than taxi puts the least strain on the aircraft, is not a place to worry about being in the red.

N201MKTurbo Grand Master

N201MKTurbo

Posted
Posted

I personally think that case cracks are caused by operating in the red zone. I would avoid it. Torsional vibration is insidious it can't always be felt but puts tremendous stress on the crank and case.  

carusoam Grand Master

carusoam

Posted
Posted

90% of power input comes from MP the other 10% comes from RPM...

While trying to select speeds and settings that work for the situation... Consider using an rpm that is outside the limitation, then adjust the MP to get the performance you are looking for.

With the O1... 2500RPM is the key setting. Adjust MP to get the speed you are looking for...

Does that cover what you are asking about?

Best regards,

-a-

Bob_Belville Grand Master

Bob_Belville

Posted
Posted

@ 15" I assume the gear is down otherwise the gear alert should be blaring. And with the gear down I would be very surprised that the prop is in the restricted zone unless you're practicing approaches with a big tailwind.

Marauder Grand Master

Marauder

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Posted

I fly approaches in my F at 100 KIAS, flaps at 15 degrees. Try 16" 2400 RPM leading up to the FAF. This will keep under the 104 VLo. At FAF, gear down. This should keep you stabilized at 100 with around 450 FPM decent. At the DA with field sighted, I drop in 33 degrees of flaps and reduce MP to 12".

Did you make out a power setting chart? If so, post it please. Some of the mods on an F will change these numbers. Be curious to see how mine compare.

Based on what you spot above, I'm wondering if your flaps are out. If they are not, good luck getting the numbers too work. You would need to drop the MP to keep the speed under control.

Ratherbflying Enthusiast

Ratherbflying

Posted
Posted

I believe the wording is avoid continuous operation. That means, stay out of there during cruise. Landing, which other than taxi puts the least strain on the aircraft, is not a place to worry about being in the red.

I was talking to a Hartzell technician about this just the other day. "Avoid Continuous Operation" means you can traverse the red zone but don't let the needle stop. Cruise, landing, whatever. Keep the needle moving until you get out.

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slowflyin Mentor

slowflyin

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@ 15" I assume the gear is down otherwise the gear alert should be blaring. And with the gear down I would be very surprised that the prop is in the restricted zone unless you're practicing approaches with a big tailwind.

Yes, gear down,  red zone below 14.5.   I'm fine at 15" but I'd like a slower approach for some fields.

slowflyin Mentor

slowflyin

Posted
  • Author
Posted

90% of power input comes from MP the other 10% comes from RPM...

While trying to select speeds and settings that work for the situation... Consider using an rpm that is outside the limitation, then adjust the MP to get the performance you are looking for.

With the O1... 2500RPM is the key setting. Adjust MP to get the speed you are looking for...

Does that cover what you are asking about?

Best regards,

-a-

With the prop full forward RPM drops with MP when you get in the lower MP ranges.  For my bird anything below approximately 14.5-15" MP and the RPM drops below 2350 into the red zone even with the prop full forward.

slowflyin Mentor

slowflyin

Posted
  • Author
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I fly approaches in my F at 100 KIAS, flaps at 15 degrees. Try 16" 2400 RPM leading up to the FAF. This will keep under the 104 VLo. At FAF, gear down. This should keep you stabilized at 100 with around 450 FPM decent. At the DA with field sighted, I drop in 33 degrees of flaps and reduce MP to 12".

Did you make out a power setting chart? If so, post it please. Some of the mods on an F will change these numbers. Be curious to see how mine compare.

Based on what you spot above, I'm wondering if your flaps are out. If they are not, good luck getting the numbers too work. You would need to drop the MP to keep the speed under control.

No chart yet, that's what I'm working on.   I'll try the 12" and see if it gets my RPM out of the red on the other end.   Thanks

slowflyin Mentor

slowflyin

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No chart yet, that's what I'm working on.   I'll try the 12" and see if it gets my RPM out of the red on the other end.   Thanks

I meant to say, 12" on the end of the approach.   I'll post the numbers as I get them worked out.  My F does have the 201 front end and most of the 201 mods.  

Marauder Grand Master

Marauder

Posted
Posted

No chart yet, that's what I'm working on. I'll try the 12" and see if it gets my RPM out of the red on the other end. Thanks

If I get some energy today, I will run over to the airport and pull the card I made 20+ years ago and the one I hang in front of the co-pilot's seat when I do IPCs with a non Mooney proficient instructor. It might get you some starting points.

I hit the red range but not on an approach, it usually a pass through as I am slowing to final landing speed.

  • Like 1
carusoam Grand Master

carusoam

Posted
Posted

Questions that come to mind...

If the MAPA book suggest one thing...

And an individual plane wants to do something else...

It may help to review what the governor limitations are...

What governor do you have?

When was it OH'd last?

There may be newer designs that could help with your situation?

I remember doing an OH on my O360’s governor, but none of the details that went with it...

1-2 amu (hardware cost) for a new one?

Or maybe this...?

http://mooneyspace.com/topic/14066-fs-pcu5000-ath-1/?hl=governor

Best regards,

-a-

slowflyin Mentor

slowflyin

Posted
  • Author
Posted

Questions that come to mind...

If the MAPA book suggest one thing...

And an individual plane wants to do something else...

It may help to review what the governor limitations are...

What governor do you have?

When was it OH'd last?

There may be newer designs that could help with your situation?

I remember doing an OH on my O360’s governor, but none of the details that went with it...

1-2 amu (hardware cost) for a new one?

Or maybe this...?

http://mooneyspace.com/topic/14066-fs-pcu5000-ath-1/?hl=governor

Best regards,

-a-

Thanks for the input, I'll track it down in the logs.  I know the prop is around 400 hours since new but don't recall the gov.

Hank Grand Master

Hank

Posted
Posted

I generally have to add about 3" MP when I drop Takeoff flaps to hold altitude. The gear goes down 1-1/2 dots above glideslope and I come right down all centered unless I screw up.

Bob_Belville Grand Master

Bob_Belville

Posted
Posted

I did not even sleep at a Holiday Inn Express last night but I would bet that the rpm restriction is not applicable when the rpm is being controlled by the throttle as contrasted with the prop governor. IOW, 25" and 1900 RPM is surely stressing the drive train where 15" & 1900 rpm is not. 

Ratherbflying Enthusiast

Ratherbflying

Posted
Posted

I did not even sleep at a Holiday Inn Express last night but I would bet that the rpm restriction is not applicable when the rpm is being controlled by the throttle as contrasted with the prop governor. IOW, 25" and 1900 RPM is surely stressing the drive train where 15" & 1900 rpm is not.

Bob, it's not about engine power, it is about harmonics. You can read about it at:

https://answers.yahoo.com/question/index?qid=20070619132438AAJJFTG

The actual restriction is contained in the Propeller Type Certificate. You need your Hub model (e.g. C2YR-....) , blade model (e.g. F7666), and engine (e.g. O-360-A1D). For Hartzell, go to

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/802f367a21c7e7fc86257d00004d5d82/$FILE/P-920_Rev_34.pdf

and look up your information in the table. Bob, there are some combinations that take MP in to consideration, but on my C the restriction is RPM range based. Period.

  • Like 1
slowflyin Mentor

slowflyin

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I generally have to add about 3" MP when I drop Takeoff flaps to hold altitude. The gear goes down 1-1/2 dots above glideslope and I come right down all centered unless I screw up.

That's how I've been managing the approach.  Many advised no flaps but the only way I can keep the speed down with 14.5" MP is flaps to approach.

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