RPM limitations questions

[Skybrd]

My son has a E model Mooney and I have a J model. Both airplanes have placards that warn about operating the propeller at certain RPM ranges. The E model has placards for not operating continuous between 2100-2350 and the J model has a different range. My question is, when on approach or in the pattern is it ok to be operating continuously within these ranges to keep airspeed and approach decent correct. I know you have to travel through these RPM's to operate and not to operate within them during cruise. What's your thoughts and actions concerning this? 

[jetdriven]

The E model is a red arc, the J is a yellow arc.  One is a restriction in cruise, one is a restriction to 'avoid continuous operation below 15".   This topic was covered in this thread here: 

http://www.mooneyspace.com/index.cfm?mainaction=posts&forumid=3&threadid=4504

 

-----------------

 

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

[rob]

duplicate

[rob]

My C has the same restriction as your Son's E. I assume the answer to your question is no, you shouldn't operate in those ranges as per the placard. As an aside of sorts, I've never found it necessary to adjust RPM into those ranges for approach or pattern work. I'm sure it falls in there at some point with very low manifold, but I've never worried about it. I guess a short answer is that I never set the prop to within the restricted range. 

[jetdriven]

On a C212 or C214 McCauley equipped J model, at middle weights, and a "normal" pattern, 500 FPM descent is right about 2000 RPM (landing configuration)   A steeper or closer pattern takes less power, and may be in the yellow arc.  The prop control does NOTHING below 90 KIAS. you have a fixed pitch prop below that speed.

  It is not  a red arc for a reason.  For all the millions of hours on M20J's, all of which were delivered new with this prop, I would like to read about  SINGLE prop failure due to this yellow arc. Produce just one.

  Its like a forum I read, where a Beech pilot said "the most important thing in my airplane is the traffic display."    Mid air collisions dont even make it in the top fifteen causes of accidents, bruh.   Neither do prop failures.  Let's worry about the things that do kill.

[SpeesseArcast]

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