Momentary slight loss of rpm/power in cruise

[bmcconnaha]

1 hour ago, carusoam said:

When a tank vent gets clogged... mud dauber style.... the fuel pumps pull enough fuel that the wing skins oil can...

They start collapsing...

So... when you look out the window and the wing skins look funny... because they are getting crushed...

changing fuel tanks gives some reprieve... but if the other tank vent is equally blocked... you might have equal amounts of time to find the ground...

One mud dauber vent blockage is enough...

+1 for sumping, because you can...

 

Got any other flights you can share data from?

Best regards,

-a-

this was the previous day from Salinas, CA to Redding CA where the plane spent the night on the ramp.  it was the following flight that had the "event"

https://apps.savvyaviation.com/flights/4917480/f044d8c0-3395-4340-9ac9-f4ba0217f7f6

this was the flight home from Prossor, WA to Coeur D Alene.  this was the flight after I landed and checked things out

https://apps.savvyaviation.com/flights/4917482/dbbd15a7-af74-4c6b-960c-86223e017dfa

[ZuluZulu]

8 hours ago, bmcconnaha said:

This is an IO390.  Trues out at 163-165.  Still slighty rich, but only 150 or so rich of peak.

What did you true out at with your IO-360?

[bmcconnaha]

Just now, ZuluZulu said:

What did you true out at with your IO-360?

162 was the fastest i had seen.  I've seen 168 with the 390.  i expect it will be a little better after a proper rigging at a mooney service center next mo 

[carusoam]

Bmc,

Any further issues since?

I reviewed the additional data from the other flights...

But nothing is standing out to my untrained eyes... 

Best regards,

-a-

[bmcconnaha]

8 hours ago, carusoam said:

Bmc,

Any further issues since?

I reviewed the additional data from the other flights...

But nothing is standing out to my untrained eyes... 

Best regards,

-a-

Pulled the belly of the airplane to look for and fuel leaks.  None noted.  We inspected the gascolator while we had the belly off and found nothing.  We looked at the fuel inlet screen.  It was also clean.  I flew several hours yesterday and it ran great.  No long legs like when the event happened, so there is that, but probably an unrelated variable.  I’ll have the service center take a look at my boost pump, but I’m thinking I’ll have it overhauled when It’s there for annual.  

[bmcconnaha]

update to this thread.  The electronic ignition was believed to be the culprit.  i have the lycoming branded surefly.  the aircraft is a 28V airplane and there is a known issue on the surefly side on some airplanes.  I called surefly, but they couldnt give me a power conditioner since mine was a lycoming branded mag.  I called lycoming, they let me know they sent me an old magneto when they shipped my new engine this march.  they have updated the software on the mags to not be so sensitive to momentary voltage spikes.  the revision on the new mag is L, and lycoming tells me the ligtning protection circuit will not activate until 60V know, and should cure my problem.  Ill update when it is in next week. 

[ZuluZulu]

On 5/13/2021 at 4:25 PM, bmcconnaha said:

162 was the fastest i had seen.  I've seen 168 with the 390.  i expect it will be a little better after a proper rigging at a mooney service center next mo 

Please definitely keep the IO-390 updates coming.  I've only got 400 hours on my A3B6D but I'm already thinking about replacing it with a 390 once the time comes.  What prop do you have?

[bmcconnaha]

On 6/18/2021 at 7:19 PM, ZuluZulu said:

Please definitely keep the IO-390 updates coming.  I've only got 400 hours on my A3B6D but I'm already thinking about replacing it with a 390 once the time comes.  What prop do you have?

will do! hartzell top prop two blade.  i was level last night at 10500, and it was pretty warm.  still making well over 160kts true.  seems to work well at altitude! planning to replace the junk ignition harness lycoming supplied with the engine next week when i replace the mag.  ordered a new maggie ignition harness.  if it works as well as thier customer service, ill be thrilled.  

[ZuluZulu]

4 hours ago, bmcconnaha said:

will do! hartzell top prop two blade.  i was level last night at 10500, and it was pretty warm.  still making well over 160kts true.  seems to work well at altitude! planning to replace the junk ignition harness lycoming supplied with the engine next week when i replace the mag.  ordered as new maggie ignition harness.  if it works as well as thier customer service, ill be thrilled.  

What led you choose that prop over other options?  

[bmcconnaha]

3 hours ago, ZuluZulu said:

What led you choose that prop over other options?  

The only other option was the three blade top prop.  It had an rpm restriction, the two blade doesn’t.  I hate removing cowling with a three blade.  

[carusoam]

Great updates bmc!

Thanks for sharing them…

Best regards,

-a-

[Shadrach]

On 5/13/2021 at 6:14 AM, ArtVandelay said:

If really running that rich, maybe just the spark plugs getting clogged with lead.

For comparison, at that altitude I run around 9gph with a TAS of about 150k.

Very unlikely spark plug would pick up lead when combustion temp and pressure produce CHTs in the mid 300s. That’s plenty of heat for good scavenging.

Edited June 20, 2021 by Shadrach