Partial Power Loss to Engine Failure in the Pattern

[AerostarDriver]

I have potentially reached a breaking point with my Mooney. Approximately, every 3-4 months I have a new issue, while not necessarily being expensive, destroys my confidence in the plane. In June of 2021, I had an unplanned power off landing due to the fuel flow divider failing on a downwind to base turn. Next in September 2021, I had the gear fail to retract and get stuck in transition (ultimately it was just a battery). Over the weekend, after not flying the airplane since November (98% weather related), I had a partial power loss shortly after departure as I turned on to the downwind leg after a full stop taxi back, after about 30 minutes of flying with no issues. 

For my own personal reasons, I fly with a gopro and use it as a debrief tool primally so that I can go back and evaluate myself. This was important for this last fight as I had also not flown since November. My A&P and I have used this video to try to figure out what went wrong, and we believe we have narrowed our scope to the fuel servo for a few reasons:

• It is the only thing that has not been replaced in the last few years fire wall forward
• They have a TBO and we can't seem to locate were in the logbooks the servo had been replaced. Assuming it was done at engine overhaul, which again there is no record of that would be atleast 5 years.
• The airplane now has a heavy fuel drip from the leading edge of the nose gear bay
• Power was only able to be gained when full power or bursts of throttle were applied

However, I am looking for any ideas that can help figure out what went wrong? As far as the engine instruments are concerned, the only indication of an issue was the increase in manifold pressure and decrease in rpm. Oil pressure and Temperature were acceptable as was Fuel pressure. As the time I did not have the bandwidth of checking the JPI for fuel flow. 

 

[Ragsf15e]

31 minutes ago, AerostarDriver said:

I have potentially reached a breaking point with my Mooney. Approximately, every 3-4 months I have a new issue, while not necessarily being expensive, destroys my confidence in the plane. In June of 2021, I had an unplanned power off landing due to the fuel flow divider failing on a downwind to base turn. Next in September 2021, I had the gear fail to retract and get stuck in transition (ultimately it was just a battery). Over the weekend, after not flying the airplane since November (98% weather related), I had a partial power loss shortly after departure as I turned on to the downwind leg after a full stop taxi back, after about 30 minutes of flying with no issues. 

For my own personal reasons, I fly with a gopro and use it as a debrief tool primally so that I can go back and evaluate myself. This was important for this last fight as I had also not flown since November. My A&P and I have used this video to try to figure out what went wrong, and we believe we have narrowed our scope to the fuel servo for a few reasons:

• It is the only thing that has not been replaced in the last few years fire wall forward
• They have a TBO and we can't seem to locate were in the logbooks the servo had been replaced. Assuming it was done at engine overhaul, which again there is no record of that would be atleast 5 years.
• The airplane now has a heavy fuel drip from the leading edge of the nose gear bay
• Power was only able to be gained when full power or bursts of throttle were applied

However, I am looking for any ideas that can help figure out what went wrong? As far as the engine instruments are concerned, the only indication of an issue was the increase in manifold pressure and decrease in rpm. Oil pressure and Temperature were acceptable as was Fuel pressure. As the time I did not have the bandwidth of checking the JPI for fuel flow. 

 

I’m curious where you had mixture set throughout the pattern?  It seemed like you adjusted it a lot?  How about the prop rpm?  Full forward the whole time?

Possibly the fuel leak will tell you a lot when you find out where it’s coming from… or it’s coming out the sniffle valve?  Or the fuel pump drain?  Or the elect boost pump drain?

It appears you have a nice airplane!  Don’t get too down on it, engines can be sorted out and are eventually pretty darn reliable!  My servo is at least 18 years and going!

[PeteMc]

Who does the maintenance?  Maybe it's time for a new shop???

We just had this discussion today at lunch, though it was really from the other direction.  A friend bought a plane 20+ years ago, but when he was first looking at it the shop that did the pre-purchase, that was also the shop that had been maintaining it for year, found a HUGE list of issues.  Friend sent the list to my mechanic (Air Mods @ N87) had a great laugh.  But he couldn't get up to see the plane right away.  So the friend found another mechanic who was able to look at the plane - and also had a great laugh with the list.  

This was a well known "New England" shop, but obviously there were issues with their work.  And they were willing to tell whomever what they thought they should hear vs. what the straight story is.

So, just saying...   Maybe your guy isn't really finding these issues until YOU find them.  Might be worth someone else looking at plane to give you an honest evaluation. 

 

[AerostarDriver]

2 minutes ago, Ragsf15e said:

I’m curious where you had mixture set throughout the pattern?  It seemed like you adjusted it a lot?  How about the prop rpm?  Full forward the whole time?

Possibly the fuel leak will tell you a lot when you find out where it’s coming from… or it’s coming out the sniffle valve?  Or the fuel pump drain?  Or the elect boost pump drain?

It appears you have a nice airplane!  Don’t get too down on it, engines can be sorted out and are eventually pretty darn reliable!  My servo is at least 18 years and going!

Fuel leak appears to be right under the fuel servo. 

On takeoff mixture was full rich, full throttle full prop, first power change was to 26/26, next power change was 24/23.5. The MP dropped way more then I expected. The next power event is the RPM drop. From that point forward it was an attempt to keep the engine running. To be quite frank, I was running out of ideas. In hind sight, screwing with the mixture likely was a bad idea, however, my last engine out was because the fuel distributor was allowing the engine to flood itself where a leaner then normal mixture would allow it to run. 

[cbarry]

I’m not a mechanic, but it appears to be a fuel starvation issue such as the fuel pump going TU or even a bad fuel line  connection causing it to suck air.  At full power it might still be drawing in enough fuel, but at low power settings, air may be getting into the fuel flow.  Another item to check is to make sure both tanks’ fuel vents are clear.  A partially obstructed fuel tank vent might result in the similar fuel starvation issue.  
 

[Ragsf15e]

2 minutes ago, AerostarDriver said:

Fuel leak appears to be right under the fuel servo. 

On takeoff mixture was full rich, full throttle full prop, first power change was to 26/26, next power change was 24/23.5. The MP dropped way more then I expected. The next power event is the RPM drop. From that point forward it was an attempt to keep the engine running. To be quite frank, I was running out of ideas. In hind sight, screwing with the mixture likely was a bad idea, however, my last engine out was because the fuel distributor was allowing the engine to flood itself where a leaner then normal mixture would allow it to run. 

Yeah if it’s already running poorly, adjusting mixture isn’t terrible, but must folks are going to follow the standard technique of everything full forward, switch tanks, etc.  Honestly, if you’re in the pattern, just getting it back on the ground soonest is your best bet.

If I may (as a CFI, but only a shade tree mechanic…) - when doing patterns, there’s not much point in adjusting mixture or prop if you’re near sea level DA.  Full rich, full prop, don’t touch them.  If you’re at high DA and need to adjust mixture for full power, then do that prior or during takeoff (target egt method is one way).  The engine is rated for 2700 rpm and full throttle and it’s the fastest way to get altitude.  Then you’ll pull throttle back on DW but leave all else alone until further reduction to start descent.  When you’re using like 5 power settings through the pattern, things get complicated and there’s not really a good reason for it.

It will be important to identify exactly where the fuel is coming out because there are like 4 places down there that are designed to let fuel out.  Try flooding the engine… there’s a drain directly below the servo tgat will pour fuel.  Boost pump broken?  There’s a drain for them.  Find the one if it’s coming out there and follow it back to the source.  Take pictures, post that info.

Just my 2 cents.

[AerostarDriver]

17 minutes ago, cbarry said:

I’m not a mechanic, but it appears to be a fuel starvation issue such as the fuel pump going TU or even a bad bad fuel line  connection causing it to suck air.  At full power it might still be drawing in enough fuel, but at low power settings, air may be getting into the fuel flow.  Another item to check is to make sure both tanks’ fuel vents are clear.  A partially obstructed fuel tank vent might result in the similar fuel starvation issue.  
 

Fuel pump was on and constant 36 PSI was maintained the whole time. I will check the vents and I am going to go ahead and do all new hoses firewall forward. Thank yoou

13 minutes ago, Ragsf15e said:

Yeah if it’s already running poorly, adjusting mixture isn’t terrible, but must folks are going to follow the standard technique of everything full forward, switch tanks, etc.  Honestly, if you’re in the pattern, just getting it back on the ground soonest is your best bet.

If I may (as a CFI, but only a shade tree mechanic…) - when doing patterns, there’s not much point in adjusting mixture or prop if you’re near sea level DA.  Full rich, full prop, don’t touch them.  If you’re at high DA and need to adjust mixture for full power, then do that prior or during takeoff (target egt method is one way).  The engine is rated for 2700 rpm and full throttle and it’s the fastest way to get altitude.  Then you’ll pull throttle back on DW but leave all else alone until further reduction to start descent.  When you’re using like 5 power settings through the pattern, things get complicated and there’s not really a good reason for it.

It will be important to identify exactly where the fuel is coming out because there are like 4 places down there that are designed to let fuel out.  Try flooding the engine… there’s a drain directly below the servo tgat will pour fuel.  Boost pump broken?  There’s a drain for them.  Find the one if it’s coming out there and follow it back to the source.  Take pictures, post that info.

Just my 2 cents.

My E has so many power and RPM restrictions it is hard to keep track of them all. I was informed when I did my transition training that you were to not maintain full power and RPM for more than 5 minutes. Then on top of that with the top prop, Hartzel says no continuous operations above 24" at greater then 2350 rpm while preserving the existing RPM restriction of 2000-2350 rpm. The guidance has been unclear to me from Hartzel as to what "continuous" means, I have heard everything from 5 minutes to 90 seconds. Am I missing something? I would very much like to not to have to make so many power changes. In theory, there is no reason I would not be able to make it to pattern altitude on the downwind in 90 seconds so I am likely making this way more complicated than it should be.

[PT20J]

I once had the B nut on the fuel pump end of the fuel line from the pump to the servo back off and it dripped fuel. I would check all the connections and especially locate the source of the leak before pulling the servo. I can’t think of how a servo could leak as you describe. There’s no fuel reservoir in a servo like a carburetor. Servos can get crudded up with varnish and corrosion if they sit a lot. Most common failure is probably the diaphragms. You might also call Al Jesmer at Precision Airmotive and discuss it with him.

Skip

[EricJ]

Just as a fwiw remote diagnostic, I'd +1 on getting the fuel servo overhauled.   I went through a very similar period with three engine failures in three months, during which the flow divider was overhauled, injectors cleaned, etc.   Once the fuel servo was overhauled it was like a new airplane and it's been pretty much solid since (five years and six hundred hours or so).

Something to check before you send it off, though, is to inspect the finger filter screen in the servo.   Whether it has any crap in it or not I'd still be sending the servo away, but it'll give you an idea of the condition right now.

It looks like a really nice panel, and I'd love an E with that panel, electric gear, and a quadrant.   Definitely worth putting some effort into it, imho.

 

[Ragsf15e]

28 minutes ago, AerostarDriver said:

Fuel pump was on and constant 36 PSI was maintained the whole time. I will check the vents and I am going to go ahead and do all new hoses firewall forward. Thank yoou

My E has so many power and RPM restrictions it is hard to keep track of them all. I was informed when I did my transition training that you were to not maintain full power and RPM for more than 5 minutes. Then on top of that with the top prop, Hartzel says no continuous operations above 24" at greater then 2350 rpm while preserving the existing RPM restriction of 2000-2350 rpm. The guidance has been unclear to me from Hartzel as to what "continuous" means, I have heard everything from 5 minutes to 90 seconds. Am I missing something? I would very much like to not to have to make so many power changes. In theory, there is no reason I would not be able to make it to pattern altitude on the downwind in 90 seconds so I am likely making this way more complicated than it should be.

Sometimes it’s tough to stay within the restrictions without overthinking them.  Especially when the manufacturer doesn’t define “continuous” for us.
 

Clearly it’s ok to takeoff and initial climb full throttle and 2700rpm.  Even if you weren’t staying in the pattern, you’d leave that power setting up through 1000’ or more to give yourself options in case there’s an issue.  In the case of a pattern, do the same thing, full power, full throttle to 1000’, level off, accelerate to desired speed (~110mph?) and then retard throttle to ~20” (or enough to hold DW speed.  I think that will keep you within your constraints and is reasonably non-continuous.  The 5 minutes restriction is not applicable in the pattern - your whole video was only 3 minutes and clearly not all at full power the whole pattern.  I’m not telling you to disregard limits, but think through what you’re doing and why and make sure it’s needed.  I think less power changes (throttle, mixture, prop) will help you know when something is actually going sideways.

Personally, I would track down the fuel leak, fix anything found, and run the engine again before sending off the servo, but again, I’m not a mechanic.

[Marauder]

I have potentially reached a breaking point with my Mooney. Approximately, every 3-4 months I have a new issue, while not necessarily being expensive, destroys my confidence in the plane. In June of 2021, I had an unplanned power off landing due to the fuel flow divider failing on a downwind to base turn. Next in September 2021, I had the gear fail to retract and get stuck in transition (ultimately it was just a battery). Over the weekend, after not flying the airplane since November (98% weather related), I had a partial power loss shortly after departure as I turned on to the downwind leg after a full stop taxi back, after about 30 minutes of flying with no issues. 
For my own personal reasons, I fly with a gopro and use it as a debrief tool primally so that I can go back and evaluate myself. This was important for this last fight as I had also not flown since November. My A&P and I have used this video to try to figure out what went wrong, and we believe we have narrowed our scope to the fuel servo for a few reasons:

• It is the only thing that has not been replaced in the last few years fire wall forward
• They have a TBO and we can't seem to locate were in the logbooks the servo had been replaced. Assuming it was done at engine overhaul, which again there is no record of that would be atleast 5 years.
• The airplane now has a heavy fuel drip from the leading edge of the nose gear bay
• Power was only able to be gained when full power or bursts of throttle were applied

However, I am looking for any ideas that can help figure out what went wrong? As far as the engine instruments are concerned, the only indication of an issue was the increase in manifold pressure and decrease in rpm. Oil pressure and Temperature were acceptable as was Fuel pressure. As the time I did not have the bandwidth of checking the JPI for fuel flow. 
 

I’m a 32 year owner of an F model which has the same engine as yours. As Rags mentioned, I wouldn’t mess with the mixture in the pattern unless you’re in the higher elevations.

What caught my attention was that you said your fuel pressure was 36 PSI.That is way too high. Something isn’t right. My F will have an inflight pressure in the 24” to 25” range. With boost pump on, I see a solid 27”. I think the red line is 30”.

As others have mentioned, it might be good to have another set of eyes have a look.


Sent from my iPhone using Tapatalk Pro

[Bartman]

You have a leak and that’s the place to start.
 

Also, the flow divider issue may have been related to something failing up stream like internal hose deterioration. If this were my plane I would replace every fuel hose and send BOTH the fuel servo and the flow divider in for service. As stated remove the finger screen from the fuel servo and inspect before sending it. Check the electric fuel pump for leaks. Mine was a Dukes 1499 series and just rebuilt and in process of installation and inspection and it has the finger screen just downstream of the pump outlet. Remove and clean it and install new O-rings. Remove and check/clean the injectors and verify the fuel lines from the divider to the injectors are clean. While you are at it, go ahead and replace all of the rubber fuel line clamps. 
 

Don’t forget to flush the new fuel hoses before installation. 

[Bartman]

@Marauder caught something I didn’t see and it caused a couple of neurons to fire. I remember a while back someone reported higher fuel pressure after replacing the electric boost pump.  I have no idea what the results of high fuel pressure would be. 

[Bartman]

Last thing. I zoomed in on your manifold pressure gauge and it’s all over the place. Do you have a partial obstruction ???

[Ragsf15e]

10 minutes ago, Bartman said:

@Marauder caught something I didn’t see and it caused a couple of neurons to fire. I remember a while back someone reported higher fuel pressure after replacing the electric boost pump.  I have no idea what the results of high fuel pressure would be. 

There are a few threads of high fuel pressure after replacing the mechanical fuel pump.  A few pointed to the wrong pump and/or internal pump spring I think but most were just a factor of the newer pumps sitting right at our max of 30psi.  I have a new tempest from 2 years ago and it still sits right at 30psi.  In that same thread, there’s documentation from the engine manual showing that it can handle much higher pressure.  I agree his fuel pressure should be less than 30 and that should be looked at but I doubt it’s the actual problem.  Now if my google-fu was good enough I’d find that thread for you…

[Ragsf15e]

1 minute ago, Bartman said:

Last thing. I zoomed in on your manifold pressure gauge and it’s all over the place. Do you have a partial obstruction ???

I agree with this as well, but he makes a lot of significant changes with the prop and throttle so it’s a little tough to tell exactly what is causing what.  He’s also got the control quadrant which can make those changes “abrupt” if not done carefully.

[AH-1 Cobra Pilot]

16 minutes ago, Bartman said:

Last thing. I zoomed in on your manifold pressure gauge and it’s all over the place. Do you have a partial obstruction ???

That was from throttle movement, until the rapid oscillation was from shutdown.

[Bartman]

The JPI is flashing 0.0 REM

[AerostarDriver]

All throttle changes I am doing are reactionary to the RPM decay and the MP increasing. Base and final you can see the EGTs just drop away every time MP increases. 

[AerostarDriver]

Just now, Bartman said:

The JPI is flashing 0.0 REM

The JPI will no longer save my fuel quantity inputs, it is scheduled to be replaced with a GI-275. Both tanks had well over 20 gallons and indicated on fuel gages on the other side.

[Marauder]

Last thing. I zoomed in on your manifold pressure gauge and it’s all over the place. Do you have a partial obstruction ???

I saw that too but didn’t want to be a Clarence and point that issue up as well.

I do wonder if the fuel leak and the high pressure aren’t a cause and effect thing.


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[Marauder]

That was from throttle movement, until the rapid oscillation was from shutdown.

I have a quadrant system as well. Can’t tell if the fluctuating MP is due to the engine issue or him yanking the quadrant back and forth. In order to get that much fluctuation on a quadrant, you need to move those controls pretty aggressively.


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[Derrickearly]

Good job getting back on the ground safely!

[mooniac15u]

11 hours ago, AerostarDriver said:

Fuel pump was on and constant 36 PSI was maintained the whole time. I will check the vents and I am going to go ahead and do all new hoses firewall forward. Thank yoou

My E has so many power and RPM restrictions it is hard to keep track of them all. I was informed when I did my transition training that you were to not maintain full power and RPM for more than 5 minutes. Then on top of that with the top prop, Hartzel says no continuous operations above 24" at greater then 2350 rpm while preserving the existing RPM restriction of 2000-2350 rpm. The guidance has been unclear to me from Hartzel as to what "continuous" means, I have heard everything from 5 minutes to 90 seconds. Am I missing something? I would very much like to not to have to make so many power changes. In theory, there is no reason I would not be able to make it to pattern altitude on the downwind in 90 seconds so I am likely making this way more complicated than it should be.

I think you need to verify these restrictions.  The only full-power time restriction I've heard of in Mooneys is with an IO-390.  If you have an IO-360 you should be able to run it at full power for more than 5 minutes.

The Top Prop brochure says this about continuous operations:

"Placard – “No cont. ops. Above 24” manifold pressure between 2350 to 2550 rpm” (M20E, M20F only)"

https://hartzellprop.com/wp-content/uploads/Mooney-Combined-PrcSht-Order.pdf

Which again allows you to remain at full power.  The limitation should be documented in the STC paperwork.

Edited February 22, 2022 by mooniac15u

[RobertGary1]

When I lost my servo the EDM was helpful as it showed fuel flow went from 25gal/hr to nothing.