RPM Restrictions -ILS

[Bob_Belville]

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.

I have a Hartzell Scimitar prop. The restriction is from 2350-2550 but only if MP is greater than 24". Obviously in the case of this prop/engine combination the issue is not confined to rpm alone. Once I'm above about 6000' I have no rpm restriction. So... it seems to be about engine power, at least in part, in some cases.

[HRM]

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.

 

What I had heard was from an old (crusty) A&P, so I'll go with Hartzell engineering. Actually, from all the discussion here it looks like you need not loiter in the zone--great tips that I shall experiment with. 

[Marauder]

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.

 

Welcome to the F troop. The boys in the Js have the higher gear speed and can get dirty at a much higher airspeed than us clean shaven F owners.   I learned that dropping to 17" 2500 RPM got me to VFo and once I dropped the flaps and stabilized at 100 KIAS, The gear can be dropped at the FAF and the rail ride isn't too far off. I do move the MP up and down a little depending on winter versus summer. I seriously debated installing speed brakes, but have learned that I can do 100 KIAS approaches all day long as long as I have at least 3k of runway.

 

Sorry I didn't get out to the airport today. But I found my file! Hope the cut and paste works...

 

[carusoam]

Nice cut and paste!

-a-

[slowflyin]

Welcome to the F troop. The boys in the Js have the higher gear speed and can get dirty at a much higher airspeed than us clean shaven F owners.   I learned that dropping to 17" 2500 RPM got me to VFo and once I dropped the flaps and stabilized at 100 KIAS, The gear can be dropped at the FAF and the rail ride isn't too far off. I do move the MP up and down a little depending on winter versus summer. I seriously debated installing speed brakes, but have learned that I can do 100 KIAS approaches all day long as long as I have at least 3k of runway.

 

Sorry I didn't get out to the airport today. But I found my file! Hope the cut and paste works...

 

Slide1.jpg

Thanks!   These numbers are pretty close to mine.   So I assume you too would get into the RPM restriction if you flew 13" while running down the rail?  I'm just clarifying so I can rule out a prop governor problem.

[Marauder]

Thanks! These numbers are pretty close to mine. So I assume you too would get into the RPM restriction if you flew 13" while running down the rail? I'm just clarifying so I can rule out a prop governor problem.

I think your governor is fine. If I am at 13" MP I would be in the red. Are you trying too fly an approach at 90? If so, take the RPM down to 2350 and run the MP around 14" to 15".

I am not surprised there are slight differences in the settings. Things like speed mods change things up a bit.

[Marauder]

And BTW the proficiency class teaches the 47 technique for our cruise numbers (MP + RPM). My bird likes 2,500 RPM and I usually will be at full throttle and that RPM.

[John Pleisse]

I have a great PAC chart I can send you....total money, hands off flying, centered around 2400 rpm. M20J.

[Andy95W]

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 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.

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.

I was thinking about this thread when I went flying today. I did an ILS, 0° flaps, gear down, 90 kt., prop full forward yielded about 2300 RPM- which is acceptable for the C model, even though it's the same prop as the E/F where it would be in the red arc.

Then flying a normal traffic pattern, I was in the red arc for most of it. Not a bomber pattern, just a regular traffic pattern like I was taught 25 years ago and have been doing ever since. The engine seemed happy and smooth.

I suppose the Hartzell technician would tell me it's okay to use the propeller, just don't fly a traffic pattern with it.

I think I'll keep from losing any sleep over this and not worry about it at low power settings. Wouldn't torsional vibration be a function of torque, which would be very low at such a low power setting?

[HRM]

I think I'll keep from losing any sleep over this and not worry about it at low power settings. Wouldn't torsional vibration be a function of torque, which would be very low at such a low power setting?

 

Are you a crusty old A&P by any chance?

[Ratherbflying]

I was thinking about this thread when I went flying today. I did an ILS, 0° flaps, gear down, 90 kt., prop full forward yielded about 2300 RPM- which is acceptable for the C model, even though it's the same prop as the E/F where it would be in the red arc.

Then flying a normal traffic pattern, I was in the red arc for most of it. Not a bomber pattern, just a regular traffic pattern like I was taught 25 years ago and have been doing ever since. The engine seemed happy and smooth.

I suppose the Hartzell technician would tell me it's okay to use the propeller, just don't fly a traffic pattern with it.

I think I'll keep from losing any sleep over this and not worry about it at low power settings. Wouldn't torsional vibration be a function of torque, which would be very low at such a low power setting?

Andy... dude... if you want to argue with propeller type certificates, have at it. Me... I'll keep flying my plane in accordance with the placards on the panel.

And by the way... can you think of any difference between the C and the E/F that just might account for the difference in where the red arc is?

[Bob_Belville]

And by the way... can you think of any difference between the C and the E/F that just might account for the difference in where the red arc is?

You mean other than a very different engine?

[Andy95W]

Are you a crusty old A&P by any chance?

A&P yes, but 'only' 49. I did learn from some crusty old A&P's, one of whom worked on Corsairs during WW2. That could be the topic for a whole new thread- whether those old guys had it right by not worrying too much, or if we're better off today with a more uptight FAA and A&P's who are more "by-the-book".

[Andy95W]

And by the way... can you think of any difference between the C and the E/F that just might account for the difference in where the red arc is?

Well, maybe it's the extra 20 horsepower that they had to extend the red arc to 2300 rpm. Would that support my theory that at low power settings it doesn't matter as much?

[pinerunner]

OK I'll risk getting flamed. I'd rather not use power settings that get me into that propeller restriction zone (2000-2350 with my newer prop according to Hartzell). Up to now I have been in that range a bit on down wind. The solution is to use lower RPM's but that's not how I was taught. It's pretty much what Deakins reccomends in Pelican Perch. So I'm considering this.  As you drop the MP and the propeller comes out of governance and less power brings it into the restricted zone I'm figuring on dropping the RPM to 1900 and then adding MP if I need more power. Oversquare, yep. 

 

Of course I need to decide on an upper limit for that  MP; I don't think the warning against going oversquare is totally bogus. I'll sort that out at altitude by watching CHT's. 

 

Of course this will make my engine management more complicated during landing and that's an issue. My whole impetus to getting a Mooney was I wanted a complex, efficient, airplane. Guess I'm getting complex.

 

Deakin makes the point that you should think of all three engine controls (mixture, prop, MP) whenever you make any power change. That's complicated though and retraining yourself can be tricky. I don't think he's technically wrong but I'm on the fence implementing some of his advice cause I'm not sure I trust myself when doing something different. I've caught myself getting stuck in old habits before so I know there's a training phase.

[rbp]

Don't know if this will work in your airplane, but for an ILS in most  light retracts, you should be able to set the power while leveled off waiting for GS intercept, with the GEAR UP. Half a dot above the GS intercepts at the FAF, put the gear down without changing the power, and at intercept, start down the GS. the drag from the gear with the same power setting should give you a nice 3-degree descent at the same IAS. you may need a little power adjustment one way or the other to stay on speed/GS/out of the red arc, but this method should be pretty darn close.

[RobertGary1]

Don't know if this will work in your airplane, but for an ILS in most  light retracts, you should be able to set the power while leveled off waiting for GS intercept, with the GEAR UP. Half a dot above the GS intercepts at the FAF, put the gear down without changing the power, and at intercept, start down the GS. the drag from the gear with the same power setting should give you a nice 3-degree descent at the same IAS. you may need a little power adjustment one way or the other to stay on speed/GS/out of the red arc, but this method should be pretty darn close.

 

That does work in a lot of planes but not in any of the Mooney models I've flown. A power reduction is still required. 

 

-Robert

[rbp]

A big power reduction? or a little adjustment?

Works great in my M. I didn't mention it because the OP has an earlier model

[Hank]

Works pretty good in my C, too, but gear down at a dot and a half high. Not a lot of drag from the gear.

[RobertGary1]

A big power reduction? or a little adjustment?

Works great in my M. I didn't mention it because the OP has an earlier model

 

Small. Maybe an inch or so to maintain the same speed.

 

-Robert

[slowflyin]

That does work in a lot of planes but not in any of the Mooney models I've flown. A power reduction is still required. 

 

-Robert

This works for me as well.   I flew some more approaches after starting this thread and it seems like 15" is a set and forget number.  Keeps me out of the red and I can live with a faster approach.   My home field has 4600 feet usable  and about 300 agl for the decision.   Even with no wind I was able to chop the throttle at the MAP and land with plenty of room.  Slower would be better for those lower IFR days but this is manageable.  

[rbp]

>Small. Maybe an inch or so to maintain the same speed.

 

yes, well, that's exactly what i said: "you may need a little power adjustment one way or the other to stay on speed/GS/out of the red arc"