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This section is for the discussion of the Restoration of Texans, Harvards and SNJs
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Flapper Valves

Mon Jul 13, 2015 10:09 am

I saw a report that fuel tank flapper valves were responsible for an unaccounted loss of power during an approach.

(Low fuel state following aerobatic flight using 20 gallon reserve tank position. Selected to RH restored power.)

3 in one tank and 1 in the other tank seized.

Is there an easy way to check flapper valve function without removing tanks?

Re: Flapper Valves

Mon Jul 13, 2015 12:26 pm

Someone forwarded the same report to me, and the only references I can find online that includes 'T-6' and 'flapper valves' are in reference to the Texan II.

If I'm wrong, someone please correct me...


Re: Flapper Valves

Tue Jul 14, 2015 4:33 am

It was a UK CAA Mandatory Occurrence Report related to a 1944 SNJ-7C registration G-BRVG
3 in one tank failed and one in other tank.
Report hints it may have been laid up for some time as it mentioned that there was sufficient fuel to cover valves during no-flying period.

There was previously fuel starvation on approach following aerobatics.

I would like to establish a good way to ensure flapper valves are okay without removing tanks or sumps - could boroscope perhaps but needs to be a tank safe probe.

Any ideas?
Last edited by Chipfire on Wed Jul 15, 2015 2:07 am, edited 1 time in total.

Re: Flapper Valves

Tue Jul 14, 2015 7:19 am

You should be able to reach them and maybe see them by removing the sump at the bottom of the tanks. I always thought the flappers just slowed down the sloshing of the fuel during turns etc. I think there are other openings in the ribs to allow fuel to transfer to the sump.

Re: Flapper Valves

Wed Jul 29, 2015 7:58 am

if you drain the tanks, you may be able to see them with a mirror and flashlight, but if they have never been changed, change them, they are flaps of rubber and I have found them broken off and laying in the tanks.

Re: Flapper Valves

Fri Jul 31, 2015 5:52 pm

Ditto what Matt says. If you don't know when they were changed you should change them.

Re: Flapper Valves

Mon Mar 21, 2016 10:13 am

I knew someone whose engine quit when he nose over somewhat steeply because he had come up on his refueling airport sooner than expected. The fuel all sloshed away from the tank outlet because his flappers had rotted and fallen apart. After landing, the engine restarted fine in 3 point attitude. His wife was in the back seat and she wasn't happy.
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