technique to avoid rpm restriction below 15"?

[RobertE]

I'm new to Mooneys with an M20J.  Typically somewhere on base but, if not then, then on final I encounter the restricted area of between, as I recall, 1,500 & 1,950 RPM when at less than 15" MP.  Is this simply unavoidable?  The vibration tells me the airplane doesn't like it.  If there is a technique I could learn to minimize it, I'm eager.

Thanks.

[jetdriven]

I use full flaps  and gear down abeam the numbers.  I ignore the RPM restriction for the 2 minute or so it takes to descend from there and land.  I have noticed if you fly a slightly wider pattern and are reasonably heavy it takes 2000 RPM to fly that descent profile

[pjsny78]

I was always trained to have full RPM when on final and it’s on the checklist as well. It is the "P" in Gumps Check.

Hope this helps.

 

[rbridges]

I don't lower my RPMs much.  With full flaps and gear down, it slows down pretty decent on its own.

[jetdriven]

full RPM below ~18" on an M20J is going to be less than governed RPM.   The C212 or C214 prop has a pretty coarse low pitch stop.

[David Mazer]

I'm not a 201 driver but I did some transition training in one.  As I recall, the restriction is for continuous operation at those settings.  I wouldn't think the time from downwind at the numbers to landing would amount to continuous in any sense of the word.

[flyboy0681]

Uh oh, I feel the old argument of wide pattern vs tight, prop forward on downwind vs final, full flaps vs partial, mixture rich vs cruise all bubbling up and ready to  brew again.

 

[jetdriven]

deleted

[Cruiser]

you can also trim to the point that it takes a little more power to maintain your airspeed and carry that power to the threshold then pull the power when the runway is assured.

Remember, if you decide to abort the landing and apply full power you will need alot of nose down trim quickly. I think this condition contributes to the departure stalls some have experienced in our Mooneys.

[testwest]

When we had the C212 prop, what I would do is try to fly a little steep and keep the rpm below the 1500 limit (with throttle near idle, remember at this point the prop is on the stop and won't govern). If I wound up aiming short a reasonably fast add of power to around 2000 rpm for a few seconds would fix things. Too steep, a nice slip will get you down (glider technique).

It's not the easiest thing to manage, though.

[Vref]

This my process which feels Ok too me...Gear Down first to get my speed down let's say 110Kts, throw in some flaps then and go full flaps abeam the numbers. I try to stay in the green until short final 2000 Rpm and > 15". This doesn not give  me a steep approach but good enough I think.  During base I X-check again that prop,mixture are full forward and gear down + mechanical indicator down) the last part I am on idle when fully commited.......I'am having autistic behaviour with regard to the gear down X-checks....I land with my two hands on the control wheel, bleeding residual airspeed this method assures me to pull full aft when the stall is impending..it works for me..

You feel that the engine/prop is not too happy in the yellow part...

The most difficult part for me is to anticipate how much time/distance and altitude I need to slow down (I have no speedbrakes). Belgium has a very tight airspace you can easely bust a busy airspace going to to some airfields....TMA, CTR or even worse a Military CTR.

If space is not available I tend to goo below the pattern altitude (outside the pattern of course) by 200 Ft pulling up gently often get's me faster to the right gear down speed. the prop is used as additional speedbrake during that process.

Though my serial allows to select gear down below 130Kts I avoid doing that (stress on gear mechanism).........110Kts seems more reasonable..my 0.5 eurocent input on this thread......is it boiling again flyboy0681...!!!

Luc

[PTK]

I have found that the J strictly adheres to the Power + Pitch = Performance tenet. As I'm sure other Mooneys do as well. Prop full hi Rpm (GUMPS) as someone said, pitch to hold an airspeed (S IN GUMPS) and power to manage descent. Keeping airspeed and descent nailed with this pitch/power interplay will enable the airplane to smoothly transition through the yellow zone rather than linger in it.

As far as use of flaps, personally, my goal is not to use full flaps on every landing as every landing is different. It depends on variables not the least of which is winds. Yes, the great majority of landings will be with flaps of a certain degree but it will also land nicely with no flaps. 

This is my two cents worth as I have learned from the pros at the Mooney Safety Foundation seminars. I strongly recommend them!

[Hank]

Well said, PK!

Personally, I don't pay a lot of attention to where needles are pointing from when I drop flaps & gear on downwind [by then, I'm already at 90 mph, prop & mixture forward]. I do pay attention to altitude and airspeed, but MP & RPM are on the other side of the panel because they aren't critical. I'm concentrating out the windows, with quick peeks at altitude and airspeed, and I confirm flap indicator position when moving them.

If I'm fast, retard a little throttle and pitch up slightly; if I'm high, retard a little throttle and pitch down slightly, and add a little more flap if necessary [that's why I don't automatically go to FULL DOWN]. There are no magic set-points for anything when landing, because every landing is different. Move the controls as required to put yourself over the runway, with the stall horn squeaking at a foot or two agl. Usually I go the last hundred vertical feet with the throttle at idle and the engine burbling away; preventing this requires adding throttle which will change my slope and put me further down the runway, but I can't fly a long, stable approach--there are trees in the way. Clear the trees, increase descent a little, once I'm sure I'll clear the road cut, throttle to idle.

Just like your CFI taught you:  pitch for speed, power for altitude, flaps as needed, all to maintain a nice, smooth final approach.

[PTK]

Quote: jetdriven

I use full flaps  and gear down abeam the numbers.  I ignore the RPM restriction for the 2 minute or so it takes to descend from there and land.  I have noticed if you fly a slightly wider pattern and are reasonably heavy it takes 2000 RPM to fly that descent profile

[mooneym20d]

Quote: allsmiles

If you would agree that every landing is different (you do agree don't you?) in that they present different challenges, then you would agree that it is bad technique to use one recipe fits all. Also it seems sloppy and narrow minded to "ignore" anything. 

It doesn't say anywhere, on any plackard, that it is ok to ignore for two minutes or so. The arc is yellow because it is meant to be transitioned through, and not stay in it for any specified amount of time.

(Byron, you don't discount the yellow arc in the same way you discount ground handling by the prop, do you?!)

(ouch!!)

[jetdriven]

Descending from 12,000 feet and remaining in the yellow arc of the tachometer for 15 minutes or more might be considered continuous operation.  It is not a prohibition, it says to "avoid continuous operation".   

Earlier Mooneys had a redline on the tachometer between ~2200-2500 RPM.  They transition through that as well.

I dont have anything from McCauley, but this topic was hashed to death on [Mapalist] a few days ago.   Here is what Mike Trudeau, from Hartzell, has to say about the red arc on M20C-F models. Avoid that yellow arc to be kind to your prop.  But it does not exceed any design  limits.

 

Message: 2
Date: Mon, 20 Feb 2012 12:15:53 -0500
From: "Trudeau, Mike" <MTrudeau@HartzellProp.com>
To: <mapalist@lists.mooneypilots.com>
Subject: Re: [Mapalist] RPM Restrictions
Message-ID:
    <774A5CC8FCFBEB44911E010938AB10490CE3CE3D@hpex1.corp.hartzellprop.com>
Content-Type: text/plain; charset="us-ascii"

Guys,

   If I could interject. The yellow arc is dictated on the Mooney by
the propeller model. Or really a vibration survey or test done prior to
a propeller/engine combination being "vibrationally approved".  In most
cases, this test is done by the propeller manufacturer.  Actually, the
particular range is unique to different model propellers. But the 7666-2
two blade is still the most common prop flying on these airplanes, so it
almost looks like it could be an airframe or engine (crankshaft)
restriction.  You will note that different approved propeller models
come with different RPM/MP limitations on these airplanes.
   The vibration tested for during a survey cannot necessarily be felt.
The survey is a measure of stresses put into the prop at different
stations on the blade during various flight scenarios.  This dated is
compared to a "known allowable". If the vibration exceeds there
allowables, the propeller/engine combinations fails. If the data has
high stress peaks that don't exceed this allowable, but are high, then
the combination can still be approved, a yellow arc can be established
to avoid these scenarios. This latter explanations is what we see in the
2100 - 2350 RPM yellow arc on the E and F two blade 7666-2. The undamped
IO-360 is, to put it simple, hard on props.
   It is literally impossible to avoid the yellow arc altogether. And
it's not necessarily unsafe, given a regular maintenance schedule, to
operate there for a while when you have to. Think about it as if you
were doing burn outs in a car when you operate in the yellow arc.
Sometimes you just gotta do it. But you know that you are putting
unnecessary stresses on the tires, transmission, and other components,
so most of us keep it to a minimum.   Your yellow arc is quite simply a
range to be avoided if you have the desire to take good care of your
prop.

Happy Flying!

Mike Trudeau
Hartzell Top Prop Performance Conversions
One Propeller Place
Piqua, OH  45356
937-778-4212
937-778-4215  Fax
mtrudeau@hartzellprop.com

 

[Hank]

Quote: jetdriven

Descending from 12,000 feet and remaining in the yellow arc of the tachometer for 15 minutes or more might be considered continuous operation.  It is not a prohibition, it says to "avoid continuous operation".   

Earlier Mooneys had a redline on the tachometer between ~2200-2500 RPM.  They transition through that as well.

 

OMG! Surely you aren't advocating reduced-power descents???

To come down from cruise to pattern, I just push forward to my chosen descent rate [typically 500 fpm], trim out the forces, and every now and again nudge the throttle and mixture to maintain cruise MP/EGT. Level off at or near pattern altitude depending on terrain, reduce throttle a little and work the trim to slow down.

Thus I'm out of any restriced operating bands right up until midfield downwind, and from there around to the numbers is not "continuous operation" nor is it a significant % power. My Performance Tables don't go below about 60% [~20"/2300], but if level and clean that is well above 90 knots, and I like 90 mph for downwind.