How do others deal with the restricted rpm zone on landing?

[RobertE]

I just read a long string from someone who had a prop strike due to, maybe, imperfect technique. Kudos to the guy who fessed up to being human.  

Anyway, a number of the responses described a landing technique that I simply don’t think is possible in my j model.

My aircraft has a yellow zone on the tach that restricts sustained operation between 1900 and 1500 rpm (I may be off on the exact restriction but it’s in that ballpark).  Anyway, this restriction means I use a little more power than I’d like for the first half of final and a little less than I’d like on the second half.  On that second half, because I’m a bit higher and faster than I’d like, I “chop and drop”.  Anyone else either suffer from this dilemma or have a fix?

[carusoam]

Many suffer from that challenge...

Early on in the history of flight...

Landing was considered temporary... not part of continuous flight... it’s the end of the flight...

The guidance stated...  avoid continuous flight in that regime...

Low power, non continuous operation, gave some people the ability to somewhat ignore the warning.

Knowing that harmonic vibration damages things, and can't be felt or sensed in any way reliably... can happen at any power level...

Engineers with a limited budget find a way to stay out of the zone...

The Engineer that believed Landing was not a continuous operation, also found broken welds on his engine mount....

Without any data that says low power in those rpm ranges is OK, expect 'temporary' means transitioning through the rpm range is OK.  Leaving it in that setting for any period of time is not transitioning... It is leaving it...

Is it an engineering limitation, or a legal limitation?

The more complete solution requires a different engine/prop combination....

PP ideas only, not a mechanic... but, I had a broken engine mount once in my M20C...

Best regards,

-a-

 

[201er]

I avoid the yellow arc more so because it is rumble and uncomfortable than the restriction. Starting out in the Mooney, I felt like it was the same dilemma as you describe (too much then too little power). However, I've grown used to staying a little high and then chopping and dropping. I strategically choose the timing for the power chop, base to final turn, and going to full flaps to end up on glidepath. This helps me maintain some energy reserve and avoid the yellow arc.

[Andy95W]

With all due respect to Anthony, I agree with Jim.  I have about 16 years flying an M20C this way, also without ill effect.

[carusoam]

Andy,

I only got 10 years without any vibration related challenges...

When the mount broke. There wasn't any way to know what broke it.

The dissapointing part...

I saw the engine was sagging once, then it wasn't...   it fixed itself!   (Sort of, but not really)

Then It was sagging again... So I flew it to the MSC...

A local mechanic could have pointed out what I had going on.  No need to take additional risk... flying it around. 

I visit with the mechanic more often now...

Best regards,

-a-

[Andy95W]

Point taken.

[N201MKTurbo]

Chop and drop is the way it is. 

Fly at the top of the rumble and then cut the power and land. 

Its not that hard.

Edited November 3, 2017 by N201MKTurbo

[201er]

4 minutes ago, bluehighwayflyer said:

You guys can feel or hear a discernible rumble when operating in the restricted RPM range?  I have never noticed that. Very interesting. 

It even shakes the camera making it unusable. I rarely operate in the range but you can see it on the approach in this video where being in IMC forced me to operate in the yellow instead of chop and drop. You'll see me make a power change around 16:20 and then it starts to rumble.

 

[201er]

11 minutes ago, bluehighwayflyer said:

That is really interesting. I can see why you avoid it now. I’m sure that I would, too, if it was perceptible like that.

The camera exaggerates it a little because of how it gets affected by the harmonic and the image stabilizer going haywire. But yeah, it makes the point. Can't be good for the plane. Hard to say how bad. Best avoid when able.

[bradp]

Is it more of a prop thing or a counterweight thing or both?  

I ask because the straight tip props have much more noticeable vibration in that range than curved tips. The time or two I’ve flown in another MT 3-blade there was no noticeable rumble.  

[jetdriven]

8 hours ago, bluehighwayflyer said:

I’m in the camp that doesn’t consider the few moments at very low power on base and final that I might be in the restricted RPM zone to be “continuous” operation. I think flying a nice stabilized approach on airspeed is a more important thing to concentrate on.  35 years with the C and 11 years with the J flying this way with no observed ill effects.

Jim

THIS

[Hank]

I've also never noticed anything in my C, even with the Hartzell 3 blade that everyone says is so awful . . . and that I really enjoy.

I usually enter the pattern at 2300, but sometimes still at 2500, and whatever MP it takes to slow below 100. After that, I rarely look at the right side of the panel, just out the windows and at the ASI, with a couple of glances at the altimeter. From downwind entry to touchdown is maybe 2 minutes of low power operation, and my placard says to "avoid continuous operation between 2000-2250 RPM." To me, this isn't continuous, it's brief. 

The placard does not say "do not operate the engine between 2000-2250 RPM."

[mooniac15u]

It is interesting to note that the M20A-F models (with certain props) have a RED arc on the tach and the M20J has a YELLOW arc on the tach.  The notes in the TCDS describe a "restriction" versus a "caution."

The following notes are from the TCDS.  For the M20A-F:

"Engine tachometer is to be marked with RED arc between 2000 and 2250 RPM indicating the restriction against continuous engine operating in this speed range for M20A, M20B, M20C, M20D, M20G models with Hartzell HC-C2YK-1/7666 propellers or HC-C2YK-1B/7666A-() propellers."

"Engine tachometer is to be marked with a RED arc between 2000 and 2350 RPM indicating the restriction against continuous engine operating in this speed range for M20E and M20F only."

For the M20J:

"Engine tachometer is to be marked with a YELLOW arc between 1600 and 1950 RPM indicating a caution range against continuous operation in this speed range with manifold pressure below 15" Hg"

[Bob - S50]

I think all of us that have a J have that problem.  We can...

Come in a bit steep and keep the power just under the yellow range or..

Come in a bit shallow and keep the power just above the yellow range or..

Come in on glidepath and go back and forth between too much and too little power or...

Ignore it or...

Use less drag like no flap or half flaps that allows staying on speed with power just below the yellow.  The extra speed requires extra runway so I only do that if I have plenty.

[steingar]

My C has a restriction from 200-2300, again avoid continuous operation.  It isn't continuous operation if you're going to and from to take off and land.  I don't worry if I'm in that zone during low power operations during landing.  I've never seen  restriction between 1500-1900.  Which Mooneys have that?

[mooniac15u]

Just now, steingar said:

My C has a restriction from 200-2300, again avoid continuous operation.  It isn't continuous operation if you're going to and from to take off and land.  I don't worry if I'm in that zone during low power operations during landing.  I've never seen  restriction between 1500-1900.  Which Mooneys have that?

M20J.  It isn't a restriction (red arc), it's a caution (yellow arc).

[Andy95W]

It seems like it's an apples/oranges thing between the vintage airplanes and the 201s.  

The specific guidance for the M20J against low power operation (below 15") probably accounts for Stinkypants' "rumble" on final.  My M20C is very smooth at low power no matter the rpm, but at cruise power there is definite vibration the closer I get to the red arc between 2000 and 2250.  I suspect the M20E and F are similar.

But Anthony's broken engine mount is definitely cause for concern, if it's related.

[AaronDC8402]

I do the chop and drop method to keep out of the yellow. Like a lot of the other J flyers, I can easily feel the vibration in the yellow. I don't even have to look at the tach to keep out of the caution range. 

If you're having trouble with the plane setting down harder than you prefer using the chop and drop, try adding 5 or 10 knots to your airspeed before the chop. That should give you enough additional energy to bleed off as a cushion. 

[201er]

33 minutes ago, AaronDC8402 said:

I do the chop and drop method to keep out of the yellow. Like a lot of the other J flyers, I can easily feel the vibration in the yellow. I don't even have to look at the tach to keep out of the caution range.

Yeah, exactly. And it becomes intuitive. You bring power back on downwind to just above the yellow arc, about 2000rpm. Then at the appropriate time you chop the throttle a bunch and it gets you to below it. You do the chop a little late cause then you have the energy to continue to maintain the same angle of attack ("airspeed" in lay terms). Might be a tad nose down to compensate the lost power. The sink rate will increase. I don't think about it any more. It just becomes second nature to the way to bring it in. But at this point, most of my approaches are smooth without the rumble and it's a rare time to encounter it like in the video unless I just have to do it.

[Bartman]

I try to keep RPM greater than 2,000 as needed on final to keep out of the yellow arc. Depending on flap setting and angle of approach that is usually around 15 on MP.   The yellow arc is uncomfortable, noisy, increased vibration, and gets my attention quickly.  It doesn't feel right in the seat of the pants and I don't fly there.

I chop the power about 1/4 mile out and there is some drop in the nose, but even with full flaps it does not drop like the Pipers I flew in primary training, especially the one with that thick square Hershey bar.

[Skates97]

1 hour ago, Andy95W said:

It seems like it's an apples/oranges thing between the vintage airplanes and the 201s.  

It appears that way. I have never experienced the vibration or rumble in my C/D that others have said they get in their J's. Regarding RPM, my POH says:

"In selecting a cruise rpm, it is recommended that the engine not be operated for cruise purposes within the range of 2150 to 2300 rpm."

The 1977 POH has similar language:

"In selecting a cruise RPM, the engine must not be continuously operated within the range of 2000 to 2250 RPM."

Both of them are talking about flight in cruise, not slowing down in the pattern and landing. Maybe I missed that somewhere in the times that I have read the POH? It seems to me that at least in regards to a C model that people have taken the word "continuous" out of context and are applying it to all phases of flight, including the few minutes prior to landing. From what I see it is clearly referring to flight in cruise.

[EricJ]

9 hours ago, bradp said:

Is it more of a prop thing or a counterweight thing or both?  

I ask because the straight tip props have much more noticeable vibration in that range than curved tips. The time or two I’ve flown in another MT 3-blade there was no noticeable rumble.  

My airplane has a two-blade Hartzell scimitar, and I can't tell much difference, if any.   If there's a vibration, it's very small.   Maybe I'm just not sensitive enough to tell.

2 hours ago, mooniac15u said:

For the M20J:

"Engine tachometer is to be marked with a YELLOW arc between 1600 and 1950 RPM indicating a caution range against continuous operation in this speed range with manifold pressure below 15" Hg"

I'm still just learning how to be efficient and smooth with this airplane, but so far I've not found it difficult to stay out of the caution range, given the 'below 15" Hg' condition.   15" isn't a lot of power so it seems to give a pretty broad range of control even if you need to be in the yellow arc.

26 minutes ago, Bartman said:

I chop the power about 1/4 mile out and there is some drop in the nose, but even with full flaps it does not drop like the Pipers I flew in primary training, especially the one with that thick square Hershey bar.

I sometimes miss the "plummeting behavior" of the Hershey-bar Piper wing from the Arrow I used to fly.   I fly fairly frequently with a buddy with that wing on his Cherokee 180, and he regularly does space shuttle approaches from so high I'm sure we'll not make it, and he never even lands long.

[Hank]

I took Cherokee pilot and his two young sons to ride once, he was plane shopping and had never been in a Mooney. When i pulled the throttle to idle on short final, over the trees causing ~300' displaced threshold at our 3000' field, he looked sharply at me.

After a normal landing and turning onto the taxiway at 2000' with minimal braking, he was still wide eyed, and said if he'd have pulled to idle at that point in the Cherokee he flew, he'd have gone down in the trees, "but in your plane, nothing happened!"

So glide profile and wing design are all what you make of it. 

[gsxrpilot]

4 minutes ago, EricJ said:

I sometimes miss the "plummeting behavior" of the Hershey-bar Piper wing from the Arrow I used to fly.   I fly fairly frequently with a buddy with that wing on his Cherokee 180, and he regularly does space shuttle approaches from so high I'm sure we'll not make it, and he never even lands long.

But we don't miss anything else, like all the wasted power and fuel used just to keep that wing flying and to push it through the air. With less than 1 landing per two hours of flight time average in my Mooney, it's plenty easy enough to land. I'll take the benefits of the laminar wing :-)

[Bartman]

I personally take the word continuous to mean setting the throttle and/or prop such that it remains at that RPM continuously.  Continuously to me can mean for a period of time whether it be 30 seconds or 30 minutes, but others may disagree and Moonies are not falling out of the sky either.  I transition thru the yellow arc, but if I set it in the yellow arc for any length of time, I consider that continuous.