N201HH Off field Deer Valley this morning

[Gary0747]

How much power will a prop that has failed to flat pitch generate without exceeding 2700 rpm?

[Hank]

6 hours ago, Gary0747 said:

How much power will a prop that has failed to flat pitch generate without exceeding 2700 rpm?

It's supposed to be 100% with WOT / Full Rich at sea level. My Performance Charts only go to 12,500 msl, and there  WOT = 18.3" and at 2700 it's 68.3%.

What's in your Book?

[cliffy]

If we have low pitch stops in the prop why wouldn't the prop act just like a fixed pitch prop if the gov fails  (that is assuming that oil is not being lost, then its only a matter of time until silence prevails).  Inquiring minds want to know. 

BTW the engine won't self destruct above 2700 RPM  It will survive for quite some time even up to and above 3000 RPM. You'll want an overhaul after that little  episode but it will survive to get you down somewhere. 

[Gary0747]

Those Mooney performance charts all assume you have a working governor. 

It seems to me that it all depends on where the mechanical stops are set for that prop.  In an extreme situation if the pitch of the blades were allowed to go completely flat one would just have a prop spinning generating little or no thrust.  The mechanical stops are supposed to prevent this but I have never seen any info on a power vs rpm with the prop testing on the stops.  I think Carusoam above eluded to this situation when he had his governor fail in his C model.

[cliffy]

IIRC we have the same prop on both the C and the E the difference is the low pitch setting

Again IIRC   11 degrees and 13 degrees respectively.  The prop can not "go flat" on our airplanes

I'm going back a lot of years but I think that is correct. Where's our prop expert? 

 

[ragedracer1977]

On 5/14/2020 at 9:42 PM, Gagarin said:

The airport was 18AZ Sky Ranch at Carefree, well within range with a suitable runway. Wonder if the plane had a moving map GPS depicting all nearby airports. 

Even if it didn't, he had to know it was there.  We all do, and he flew over it all the time.  

I suspect he didn't think the issue was that serious at the beginning. By the time it got very serious, it was too late.

[carusoam]

@Cody Stallings is our prop guy...  (question above) ^^^^

 

As far as where the stops are set on our props... it is outside the gov’s range.... just slightly...

Keep in mind, the gov’s range is wide to account for air density and temperature variations...

PP thoughts only, not a mechanic...

Best regards,

-a-

[afward]

12 hours ago, Hank said:

It's supposed to be 100% with WOT / Full Rich at sea level. My Performance Charts only go to 12,500 msl, and there  WOT = 18.3" and at 2700 it's 68.3%.

What's in your Book?

The fine pitch stops are supposed to be set for 2700 RPM at full power in standard conditions with zero forward speed.  Once you start to move, the pitch _must_ increase to maintain 2700 RPM with the same torque input.  Case in point: At sea level, accelerating from a standing start at full power to 70 mph will rotate the blades about 6.7 degrees (ignoring wind, non-standard atmosphere, and slippage).

NOTE: I'm actually not sure I got the math right...  I did it as atan((70 * 5280 * 12 / 60 / 2700)/(74 * PI)).  That completely ignores all variables related to non-standard atmosphere or altitude, so I'll gladly defer to the aero. engineering types for the full formula.

[Ibra]

19 hours ago, Gary0747 said:

How much power will a prop that has failed to flat pitch generate without exceeding 2700 rpm?

I think the most interesting questions when you are stuck on fine pitch are: 1/ what speeds where RPM stays bellow 2700rpm on max WOT MP? 2/ and at what MP and speed the rpm starts to drop from 2700rpm where the engine drive and governor flyby weights runs out of action?

I understand for the former climbs around Vy should work on WOT while for the latter MP less than 16” RPM starts to reduce on slow speeds, so I would try to fly cruise about there 

There is no way I can fly at 150kts on 2700rpm with full forward pitch as I do at 90kts, also some Lyco engines can overspeed at 2900rpm for 5seconds which is just about the time one can pull up to climb to 90kts on idle throttle 

How to go down is tricky? honestly, if power-plant hold it’s breath, I will fly keep some height to overhead and go for power off landin rather than trying a planned cruise descent, 

Note in normal aspirated engines you can keep propeller & throttle forward and fast IAS with no issues at FL100 but as you go down with propeller or throttle stuck forward nominal engine horse power and kinetic energy will just come out of nowhere, so I don’t think that will be manageable if you fly away from drag configurations and drag speeds 

Not sure if poor mixture to set power can be abused in the scenario? but no doubts I will pull it as well if things goes out of control 

[Ross Taylor]

This is a fascinating discussion and I'm looking forward to all the input.  As a former Phoenix resident and frequent flyer from DVT, and over that entire North Phoenix/Cave Creek/Scottsdale area, I'd also have to assume that any local pilot knows of Sky Ranch.  There are no FBO services there, but it's a nice strip and there are lots of helpful resident pilots there.  So, I'd have to agree with @ragedracer1977 that there was some thought/hope that the issue wasn't as bad as it turned out to be.  But, how bad was this failure?  That's what I'm looking forward to learning more about here.  So, if my engine's still turning and the prop's at the fine stop I'm going down...maybe before the closest available field?  I honestly didn't realize that...so, faced with the same scenario I'll be honest that I might think getting back to DVT was a viable option.

[thinwing]

On 5/16/2020 at 7:55 PM, cliffy said:

If we have low pitch stops in the prop why wouldn't the prop act just like a fixed pitch prop if the gov fails  (that is assuming that oil is not being lost, then its only a matter of time until silence prevails).  Inquiring minds want to know. 

BTW the engine won't self destruct above 2700 RPM  It will survive for quite some time even up to and above 3000 RPM. You'll want an overhaul after that little  episode but it will survive to get you down somewhere. 

I used to operate my fixed pitch 0360 in an experimental Pitts at 3400 rpm to get 225 hp.It was run for about 800 hrs before we overhauled it due to fuel contamination.No issues from extended “ over speed”

[Cody Stallings]

I really couldn’t say how much Thrust it would make.

You would definitely decelerate, or Overspeed.

Possibly both.

Would be like doing highway speed an downshifting to 1st Gear.

 

[tmo]

Kind of begs of a Mike Busch (I think) quote: "Not how hard you drive the engine, but how you drive it hard"

[Ibra]

Hot & fast diesel cars do get excited on fast on low gears that the only way to slow them down is for engine governor to cut fuel, initially gas pedals don't help much so there is an extra layer that cut diesel on engine overspeed, for aircrafts tough I am not sure if everybody agrees to the idea of linking propeller governor to mixture ?

A similar story happens in aircrafts (DA62 & DA40NG) that runs with JetA instead of Avgas? in these the engine does run way faster (7800rpm) to what propellers can take, then things get shifted via gear-box (2:7) and feed a variable pitch propeller (1900rpm-2300rpm), in the ECU engine overspeeds are automatically controlled by fuel flow & pressure controllers (torque = fuel injector mass * fuel boost pressure) after that propeller speed is set in the constant speed unit with electric pitch adjustment, propeller speed & engine torque give you the desired power 

It will take some nerves to do the same with throttle & mixture & boost-pump manually in a 160kts dive with a failed governor 

Also, wondering why we can't manually adjust propeller pitch say in two positions for emergencies? say an emergency cable directly connected to the spinner return spring as backup to governor pump & engine oil? 

[Gary0747]

http://www.kathrynsreport.com/2020/05/mooney-m20j-201-n201hh-accident.html

[jetdriven]

On 5/14/2020 at 12:49 AM, jetdriven said:

Propeller.governor failure really often means oil quantity failure.  

 

[hammdo]

Prop issue and flew with A&P to diagnose after overhaul...

not developing full power for takeoff...

according to report... maybe something other that the the prop was the initial issue that caused the prop overhaul in the first place?

very interesting read, hope it was not a MIF...

-Don

[Gary0747]

Are the mechanical stops normally set so that the max rpm is closer to 2700, not 2850?

[carusoam]

The mechanical stops are set outside the normal operating range...

This way... the gov has enough latitude to get to 2700 or max rpm under various atmospheric conditions....

PP thoughts only, not a mechanic...

Best regards,

-a-

 

[EricJ]

On 6/16/2020 at 5:40 AM, Gary0747 said:

Are the mechanical stops normally set so that the max rpm is closer to 2700, not 2850?

I believe it should not result in exceeding the tach red line under any conditions, e.g., static run-up, takeoff roll, climb out.

EDIT: This means under power-limited propulsion or static.

Edited June 18, 2020 by EricJ

[cliffy]

If its against the low pitch stops and the pitch change is not working would it not be airspeed dependent much like a fixed pitch prop?

Do we remember how the RPM would exceed the redline in a Cessna 150 if we left it firewalled and pushed the nose over?  

Same thing here except that being as how its probably at a lower pitch setting than what would be put on as a fixed pitch prop on that engine (probably closer to a climb prop than a cruise prop pitch setting, obviously for better take off performance) the RPM will go high at a much lower airspeed OR power setting. Quite possibly the low pitch setting will only absorb a HP% below max for the  engine before going overspeed. 

Hence it won't "absorb" full throttle HP even in level flight without over speeding. 

 

[Ross Taylor]

I know we're talking a lot about whether he (or we, in that situation) could maintain enough power to remain aloft.  I pondered that myself, in an earlier question above, wondering if a loss of governor pitch control meant I'd be going down.  But in reading the Kathryn's Report, it isn't clear to me that they were unable to keep flying...until they lost the engine entirely...then that's a done deal, of course.  Thanks to all who've provided input and mechanical insight into this...it's an interesting learning opportunity for me.  The fact that all are okay makes it easier to dissect and ponder.

[Parker_Woodruff]

I was CFI onboard an M20R that experienced a transient propeller governor failure.  The engine rapidly accelerated to 3600+ RPM and held there until I could get the throttle pulled back.  Then it settled in at 2700 RPM.

By rapid acceleration, I mean basically instantaneous.  It was an MT.

I never want to hear that sound again.

I'm curious about the report where it says the pilot looked for max RPM on the ground and then adjusting the governor.  Can the M20J get to 2700 while standing still?  It can get close...not sure if it can get all the way there.

[jetdriven]

No, it’s about 2575 RPM static. At about 60 to 90 mph, it can reach 2700

[PT20J]

2 hours ago, jetdriven said:

No, it’s about 2575 RPM static. At about 60 to 90 mph, it can reach 2700

Did you mean 2675 static?