Red Cubes - Junk?

[airguy]

Originally Posted by Paul 5r4

Is the red cube an item that should be replaced at any certain interval or is it a use it until it fails then replace it? I have one and it's worked flawlessly for the 500+ hours/8 years it's been in use. Last night I was flying and noticed it was fluctuating .2-.3 tenths of a gallon on fuel flow. I've don't recall noticing this in the past. Wondering if this is an early failure symptom.

Could just as well be an indicator of another failure - like your carb floats or a misadjusted fuel injection servo.

[Bill.Peyton]

I had one fail at around 500 hours and 4 years. I now carry a spare

[RV7A Flyer]

Originally Posted by Bill.Peyton

I had one fail at around 500 hours and 4 years. I now carry a spare

That's okay, but I don't think necessary. I wouldn't want to change one out in the field. You don't actually *need* fuel flow meter to fly. Just lean the old-fashioned way (by EGT or roughness). If it dies during a flight, it's not an emergency...the engine will keep running

Mine started giving up the ghost a couple of months ago, at which point I ordered a new one and swapped it out at the next oil change, in the comfort of my hangar, without time pressure to "get it done ASAP" to get home, etc.

[9GT]

Originally Posted by RV7A Flyer

That's okay, but I don't think necessary. I wouldn't want to change one out in the field. You don't actually *need* fuel flow meter to fly. Just lean the old-fashioned way (by EGT or roughness). If it dies during a flight, it's not an emergency...the engine will keep running

Mine started giving up the ghost a couple of months ago, at which point I ordered a new one and swapped it out at the next oil change, in the comfort of my hangar, without time pressure to "get it done ASAP" to get home, etc.

I agree and would also rather do the swap at my home base hanger. That being said, the RV-10 has tons of room to carry spare parts and tools and if you have known small parts that fail often, why not.

[dhmoose]

When my red cube failed on a trip to Canada, I had a conversation with the manufacturer and they confirmed that the unit was designed to continue to allow the passage of full fuel flow even if the impeller inside was completely frozen/ unable to spin. Just further confirmation that in the event of a ?catastrophic? failure, you can continue to fly home for the repair/replacement.

[Linedog]

When they do fail, are people seeing zero indications? or fluctuations, or? What is a normal failure indication? Mine was flawless through 480 hours.... seems to be about the mean failure time?

On takeoff, I got indications of very high fuel flow (54 gph on an IO-540) that in retrospect seems almost exactly double what was expected. When I pulled the power back to come back and land, fuel flow indications returned to normal.

I suspect the cube, but wonder if it is an electrical connection issue...

By the way...no big holes for fuel to come out of... checked that

Thanks!

[Flash]

HI Jeff,
When mine failed a few months back, it started intermittently showing FF or zero then would function fine. It finally went out and just showed zero. Mine had about 400 hours on it but that was over 15 years.

[bnt83]

My red cube failed in about three years, the wire broke at the machined aluminum chassis. That joint is not very sturdy and the cable they used is pretty stiff with the outer jacket. The one I red RTVed the **** out that joint adding some support to the wire exiting the chassis.

Pay special attention when performing MX and not to stress that area.

[martinlw]

Did you ever get to the bottom of this?

Originally Posted by FasGlas

I'm going to keep this thread alive since I've done more testing, still have not solved the problem and have seen more Red Cube failure posts. I've increased the bias voltage, as suggested by a viewer, changed from FF1 to FF2 on the RDAC and remounted the Red Cube using all straight fittings and wrapped in fire sleeve. Added rubber to the Adel clamps. Still it reads and fails as it pleases, ALL other sensors/inputs work fine on both RDAC's.

I contacted EI, talked to product support and I'm shipping this third Red Cube to EI to be tested. They said they will test with vibration and heat to see if it will fail. If it passes then I can move my troubleshooting to other areas.

I will post the results of the test when I get it.