Emergency Landing Troubleshooting

[bjdecker]

We will look at the fuel pump vent port and gascolator when we decowl today. Gascolator sump looks good but may not be indicative of the whole story inside. I'll report back.

From memory, after ICO the pressure drops pretty quickly. Definitely does not stay more than an hour.

The plan today is to decowl for a thorough visual inspection. When we're happy with that, 2 hours of ground runs to make sure we're happy with the performance of the electric pump. If that checks out, my instructor will solo ferry the plane. Circling climb to 12,000 above the airport it's currently at, monitoring performance and then picking up class C clearance with Montreal terminal (who will know the plan ahead of time) and straight-lining to home base which is 25NM away. If the engine quits halfway, he will be able to glide to either field or if required to the longer runways of CYHU.

This assumes that the fuel pressure is measured between the Mech. fuel pump outlet and the Servo inlet -- e.g. the pressure in my IO-360-A1B6 w/ Avstar 5VA1 (RSA5 clone) servo remains > 30psi for quite a while (hours), dropping to ~16psi after a few days...

 

[lr172]

This assumes that the fuel pressure is measured between the Mech. fuel pump outlet and the Servo inlet -- e.g. the pressure in my IO-360-A1B6 w/ Avstar 5VA1 (RSA5 clone) servo remains > 30psi for quite a while (hours), dropping to ~16psi after a few days...

are you suggesting that not holding pressure there after shutdown is a problem?

 

[bjdecker]

are you suggesting that not holding pressure there after shutdown is a problem?

Depends on the "leak" right?

Fuel Pump: A tear in the diaphragm can allow fuel to enter the accy. case - poisoning the oil.
Fuel Pump: A weak check valve (inlet) can push fuel back into the tank, or (outlet) suck fuel away from the servo.

Servo: ICO isn't, more fuel to bleeds through the rotary valve...

 

[Ralph Inkster]

I would
1- do a fuel flow test from each tank, slowly changing the Andair valve from Rt to Lt to determine where the valve positively opens or closes flow based on knob position. Also confirms proper flow rate from each tank (at this moment!).
2- if there are fuel filters inline to each tank, check both for FOD blockage.
3- drain each tank separately to confirm no other FOD in the tank & clogging up the fuel pickups (remember, trouble happened while you were flopping around doing stalls & such)
Checking vents is easy to do but I don’t think the problem (without prior symptoms) is there.
Edit- actually I’d REPLACE the inline fuel filter elements if there was a possibility of FOD or bad fuel load. There could be potentially a shellac layer (invisible) on the filter element restricting fuel flow (happened to a friend) & if you are in there anyway, not a bad idea anytime.

 

[lr172]

Depends on the "leak" right?

Fuel Pump: A tear in the diaphragm can allow fuel to enter the accy. case - poisoning the oil.
Fuel Pump: A weak check valve (inlet) can push fuel back into the tank, or (outlet) suck fuel away from the servo.

Servo: ICO isn't, more fuel to bleeds through the rotary valve...

I would suspect most servos will not hold pressure very long. When mine was OH'ed, it did, but after 50 hours, it did not. Not sure that is a definitive test to prove FP leakage.

 

[bjdecker]

I would suspect most servos will not hold pressure very long. When mine was OH'ed, it did, but after 50 hours, it did not. Not sure that is a definitive test to prove FP leakage.

"I never promised you a rose garden..." nor did I say it was definitive...

But, that aside, mine is still "new" (400 hours) and it holds full pressure for about a day, then drops to about 1/2 after another day, etc. after a week it's down to 5psi or so.

Also, fuel pressure is a useful tell/tool during our hot start shenanigans. I now have all of the RV operators at my home field at least looking at the gauge before mindlessly opening the throttle & mixture all the way, turning on the boost pump for 10 seconds, then holding the starter on for 30 seconds (like a Cirrus pilot -- (shaking head)).