Leaky FCUs?

[Kzastrow1]

I’m curious how many of you TC drivers have leaky or leaking fuel control units?  Not so much on the -10 engines but on the early engines?  It seems like about 50% of the MU2 fleet with -1 to -6 motors have some sort of fuel dripping on the hangar floor.  Some owners shut down by turning the main fuel switches off and letting the engine starve prior to hitting the stop switch so that there’s little to no fuel available for post flight drip.  Similar situation on the Commander?  Just curious. 

Kirk

[Adam Frisch]

Isn't that the SPR valve that tends to leak?

[Kzastrow1]

I just found this in the Spring 2021 issue of Flight Line.  (Google is my friend)

“Notice three separate lines coming from the drain mast on the underside of the engine cowling. The forward line is fuel, the middle is hydraulic fluid, and the aft line is oil.  If fuel is dripping from the forward line it could be coming from one of four components: the fuel pump, the fuel control unit (FCU), the start pressure regulator (SPR), or the plenum drain fittings. The allowable fuel leak limit when the airplane is static is 15 drops per minute.”

15 drops per minute sure seems like a lot.  I have 2 drops per minute on my right engine and 1 per minute on the left.  Nothing to be too concerned with I guess. 

[donv]

Mine drips a little bit when I have a large fuel load on the airplane. It doesn't do it unless I have probably 1500-2000 pounds or more. If I turn off the fuel shutoff, it stops.

I've been told it is usually the FCU.

[Bruce Byerly]

It happens and fuel can be pushed past the FCU seals. It’s fixable. Few properly fix MU2’s.

[Kzastrow1]

 “Few properly fix MU2’s“

Hey Bruce,

So is this just an MU2 phenomenon or are you saying that the MU2 drivers just live with it while other TPE331 airframe drivers don’t?  I’m sitting between two dash 1s in my F model and I’m guessing the older engines are more prone to the leaky FCUs.

[Bruce Byerly]

Sorry I meant to add a 😊 There’s no reason they can’t be fixed. People just put up with it.  If it’s FCU, higher the fuel load and pressure on the unit, the worse it gets.

[donv]

To add to that, at least in my case, it didn't stay fixed. As I recall, I had to overhaul one of my FCUs for some reason, and the drips went away, but a few (okay, maybe 8-9 years-- time flies!) they drip again.

Sorry I meant to add a 😊 There’s no reason they can’t be fixed. People just put up with it.  If it’s FCU, higher the fuel load and pressure on the unit, the worse it gets.

[donv]

They replaced a bulb seal on mine, which seems to have fixed it for a while at least. I'm sure it will be back at some point.