Frequency of Mechanical Failures Poll

[201er]

Mechanical issues are more of a question of when not if. I've already experienced repeated failures of certain systems to have my own stats on how long some components go between failures.

For this poll, only base it on failures in operation (in the air or on the ground). Not, preemptive replacement or failing a checking at maintenance and being replaced. For in-flight failures, share your stories. 

For electrical system, vote based on any failures that entirely or partially hindered electrical system operation. So, not a radio failure but a master switch failure, alternator failure, wiring failure, voltage regulator, etc. Not a dead battery and won't start failure. But, if you had an electrical problem in flight because the battery stopped working.

For vac system include any vac systems from the vac pump to the actual vac driven instruments.

For powerplant, it doesn't have to be a full engine stop or necessarily even power loss. Vote based on a failure that affected power production, that you can feel in the cabin or at the controls, necessitated an urgent landing, or prevented further engine operation without maintenance after the failure. You can be more specific in the discussions.

I'm particularly interested in hearing the number of hours of Mooney operation for pilots who've experienced the same failure at intervals (not the same thing breaking again immediately after being fixed). Basically take an average based on the number of Mooney hours flown divided by the number of times you've experienced a failure in that category. 

Don't include pilot error things like fuel starvation or exhaustion, turning something off accidentally, etc.

The numbers aren't particularly exact, just round to the nearest category.

Edited December 3, 2025 by 201er

[Greg Ellis]

I have about 1900 hours on my C model.  In that time, prior to removing the vacuum system, I have had 2 vacuum pump failures both in VMC.

I have had two generator failures (both at night) before converting to an alternator.

I have had one engine failure at 10,000 feet over New Mexico.  Partial power loss until over the threshold of Clovis, New Mexico then complete power loss.  The engine decided to get rid of a main bearing.  Guess it didn't like the one installed. 

[Vance Harral]

I am surprised, and fairly bothered, that initial results indicate our community is experiencing substantial powerplant failures at about the same rate as electrical and vacuum system failures.  That is not what I was expecting, and not at all what I hope is true.

[Yetti]

1 hour ago, Vance Harral said:

I am surprised, and fairly bothered, that initial results indicate our community is experiencing substantial powerplant failures at about the same rate as electrical and vacuum system failures.  That is not what I was expecting, and not at all what I hope is true.

I was a little concerned that the way pilots were finding out that their alternator was offline was after the battery went down.    I noticed mine by doing an instrument scan and noticing the AMP meter pegged. 

[DXB]

1 hour ago, Vance Harral said:

I am surprised, and fairly bothered, that initial results indicate our community is experiencing substantial powerplant failures at about the same rate as electrical and vacuum system failures.  That is not what I was expecting, and not at all what I hope is true.

Category includes losing mags, which I suspect comprise the vast majority.  

[DCarlton]

In about 1000 Mooney hours....  one alternator (field wire), zero vacuum, two power plant (one loss of power; one extremely rough running engine), one propeller (spinner backplate shredded metal) plus several on the ground post maintenance (fuel system, vacuum system).    

[DCarlton]

2 hours ago, Vance Harral said:

I am surprised, and fairly bothered, that initial results indicate our community is experiencing substantial powerplant failures at about the same rate as electrical and vacuum system failures.  That is not what I was expecting, and not at all what I hope is true.

If I consider all data prior to, and after my engine overhaul, this is true in my case.  I was fairly bothered too; thus an overhaul prior to TBO.  

[Bartman]

In 1500 hours I have experienced the following, approx hours of ownership listed in parentheses:

-VR failure 3 hours from home, turned into a great 4 day weekend adventure at OBX (100)

-uneventful vacuum pump failure in VMC (150)

-cracked spinner noted on landing at home (300)

-D3000 mag failure in flight, diagnosed in flight by 100deg EGT rise on all cylinders (350)

-lost alternator in flight, broken field discovered after landing at home (500)

-coms and transponder failure, resolved with replacing wiring harness (800)

-skytec starter failure 4 hours from home (1000)

-broken spinner bulkhead (1500)

[Shadrach]

3 hours ago, Vance Harral said:

I am surprised, and fairly bothered, that initial results indicate our community is experiencing substantial powerplant failures at about the same rate as electrical and vacuum system failures.  That is not what I was expecting, and not at all what I hope is true.

If one does not differentiate between a catastrophic powerplant failure and an issue with a single mag, the number is going to seem needlessly scary.

[takair]

Have had vacuum pumps fail at about 500, all VMC. Generator partially failed at some point. Engine failure. Have had only partial on various airplanes. Significant because it scared me and forced me to land, but not catastrophic like forcing me to ditch. 

I deal a lot with the statistics of aircraft systems failure in my regular job. The FAA has surprisingly low criteria for engine failure, because the failure alone is not considered to be at the catastrophic level. They figure that the plane can still glide and stalls at a theoretically survivable landing speed, plus crash survivability. The  primary flight data has higher integrity demands than the engine. Even there, it is backups that matter. Vacuum pumps will fail, but hopefully not at the same time the electrical system. Even electronic flight displays assume a backup, because of the statistical failure rate. Best bet is always dissimilar solutions. Vacuum AND electronic display are actually quite complementary, although I’ve not run the numbers. 

[EricJ]

15 hours ago, Yetti said:

I was a little concerned that the way pilots were finding out that their alternator was offline was after the battery went down.    I noticed mine by doing an instrument scan and noticing the AMP meter pegged. 

I have an AV-17 voice annunciator that says, "Check bus voltage" if the system voltage drops below 13V.   Both times that the alternator quit I knew about it immediately, which does make a difference in being able to manage the remaining battery power.    It also says, "Engine monitor" if the monitor alarms at all, and then I just look at the JPI which always has whatever the alarm variable is in big letters on the bottom of the display.    It alerted me once when I forgot to open the cowl flaps on a missed approach, which probably saved my motor.   Although it does do some annoyance alarms sometimes, it's way more than paid for itself for stuff like this.    I always worry when I fly an airplane without similar voice annunciation that I'm going to miss something.

[Yetti]

3 minutes ago, EricJ said:

I have an AV-17 voice annunciator that says, "Check bus voltage" if the system voltage drops below 13V.   Both times that the alternator quit I knew about it immediately, which does make a difference in being able to manage the remaining battery power.    It also says, "Engine monitor" if the monitor alarms at all, and then I just look at the JPI which always has whatever the alarm variable is in big letters on the bottom of the display.    It alerted me once when I forgot to open the cowl flaps on a missed approach, which probably saved my motor.   Although it does do some annoyance alarms sometimes, it's way more than paid for itself for stuff like this.    I always worry when I fly an airplane without similar voice annunciation that I'm going to miss something.

Same with rental cars.   I was looking at Volvos around 2020 the Sales guy said this car has so many features that owners report problems renting cars without all the automated features.

Last couple of times I have rented a car the routine has changed.    It used to be jump in and adjust the mirrors and figure out the A/C while exiting the lot.    Now you need a whole systems check out if it is another brand. 

[AndreiC]

In about 1500 hours I’ve had the following:

1) Two vacuum pump failures, about 4-500 hours on each of them. Non-issues, I was in clear VMC each time. One of them I thought may have been caused by a mechanic washing the engine with solvent without sealing the pump intake port (pump failed one hour after the wash).

2) One mag failure in flight, about 20 miles from home base. Mag had about 500 hours from overhaul. Knew right away as my electronic tach gave me a red light warning. Mechanic had to drive to my field, take out the mag and send it out for refresh. 

3) Alternator failure that happened a few times (and took several trips to the shop to diagnose properly). Turned out to be a bad field wire that kept shorting and tripping the CB. Not in IMC (and until was resolved did not fly IFR). No big issue. 

4) I repeatedly had problems on a Cherokee I owned with the starter, once leaving me stranded at a remote field and requiring starting by hand propping, which was a bit scary. Was fixed by replacing the old aluminum wires with copper. 

[UteM20F]

I'm still new to the Mooney, with only 200 or so hours of Mooney time, so I have no statistically relevant information to share.  We just had our first failure that might fit your survey.  On a cross country flight, the weld at the inlet to the muffler broke, causing CO to enter the cabin.  Luckily we have a CO monitor that quickly notified me that the CO concentration was rising rapidly, to hundreds of ppm.  Turning off cabin heat and opening the outside air vent made the problem manageable.  While this isn't a powerplant failure, it had the potential of being worse if there wouldn't have been a CO monitor.  

A bright side to the story is that we're having a Power Flow exhaust installed while the plane is down.  

[47U]

Generator.

I’d flown up to MYV, about 10 miles away, to meet up with a CFII for a practice IFR check ride prior to scheduling with the DPE.  On the way up, volts dropped to battery voltage.  I landed at MYV, told the CFII that I had to cancel, and flew back to LHM on just the comm radio.  George in Rio Linda turned the generator overhaul around in a couple days.  I would have upgraded to an alternator but was against the clock to complete my check ride before my written expired (for the second time).  I passed the checkride, and am still on a generator.  I’ll upgrade to the alternator when the engine is overhauled.  And I miss George.  He was the best.