Forced landing due to leaking fuel drain

[Thruster88]

Report from RAAus 

 

STATUS: Under review OCCURRENCE DETAILS SUBMITTED TO RAAUS: The Jabiru departed YMKT first light with full wing tanks (135 litres) for a non-stop flight to YBKS. A planned flight time of 5.7 hours. The pilot had been tracking fuel use via fuel flow meter ranging between 13.5 - 15 litres an hour which was as expected, however 27 miles on the 320 radial short of the destination at 2500’ the engine stumbled once and caught again the pilot immediately switched on the electric pump and focused on a landing area on the black soil before flying over a highly treed area that separated the aircraft from Barkley. The engine ran for another 10-15 seconds before winding back to 1250-1300 RPM at full throttle. The pilot had been monitoring the LED fuel lights for the last hour of flight as they were dropping into the red then back to one green bar continuously. They find them notoriously unreliable and always use Fuel Flow Vs take of fuel as my reference. The pilot declared a MAYDAY on area frequency 126.7 and when they received no answer switch to 121.5 and retransmitted the MAYDAY. Response was heard from QANTAS international flight who contacted Brisbane on their behalf. After landing successfully on the desert floor QANTAS handed the pilot over to another aircraft. They do not have the details as all the flight planning and flight log have remained with the aircraft. The pilot of that aircraft stayed in touch with the Jabiru and Brisbane Centre for around 5 minutes. After losing contact with that aircraft on 126.7 the pilot was still unsure if their position was fully known so they activated their beacon and waited for further contact to be made. They tried Brisbane Centre several times with no success and each time transmitted in the blind their position. The pilot tried both area frequency and Brisbane Centre on the hour and half hour times to conserve battery life but received no answer. Approx. 3.5 hours on the ground they heard a helicopter in the distance and contacted it on area frequency to be notified they were coming to assist. R22 landed 5-6 minutes later and remained on the ground at idle until the Jabiru pilot was ready to climb aboard. All they could take was their overnight bag and one Jerry can for fuel. R22 flew them to Barkley Homestead where they spoke to SARWATCH who had contacted the manager by phone. They confirmed there was only 1 POB and the EPIRB was deactivated before they left the landing area. Once on the ground it was immediately obvious that the fuel drain for the header tank had failed open as the last litre had drained onto the desert floor and the remains fuel (approx. 40 litres over 5.7 hours had drained away in flight) at no time did the pilot smell any fuel leak. When the fuel total seemed to be low they visually checked both wing drains and fuel filter clamps and no obvious leak, visual or using smell was present.

 

Interesting report although very poorly rewritten once again. "They find them notoriously unreliable and always use Fuel Flow Vs take of fuel as my reference." They and my in one sentence? 

 

Probable Cause, pilots failure to notice fuel drain did not shut off fully after fuel check due low light in pre dawn. We change leaking fuel drains regularly at work, the orings don't last forever. Debris can also lodge in the drain.

[facthunter]

Probably more common than realised. I don't like the idea of relying on an "O" ring. Nev

[Thruster88]

Just about every light aircraft uses the same system. Orings are almost totally reliable when used in a fixed recess like a propeller seal. The used in fuel drains rely on the Oring not breaking to remain in place.

 

[facthunter]

Earlier types relied on metal to metal You gave it a bit of a turn when  drain completed to seat it and checked it had visually... Nev

[Thruster88]

Our very experienced CFI at cowra aero club has said to me in conversation that fuel gauges in aeroplanes are not there to show how much fuel you have, they are there to show how much fuel you don't have.

[turboplanner]

On 30/07/2022 at 11:18 AM, facthunter said:

Probably more common than realised. I don't like the idea of relying on an "O" ring. Nev

They work OK on lamb’s tails.

[kgwilson]

Curtis drain valves work well & can be locked open & fuel will drain quickly from them so it is pretty hard not to notice. I replace the Oring if I ever notice a drip on the bottom of the valve after a fuel check which I do before the first flight of the day & after every refuel. I have replaced a couple over time.

 

Jabirus do not use Curtis brass drain valves.

Edited July 31, 2022 by kgwilson

[facthunter]

"O" rings are notorious for having pieces cut out of them when being "ported.". The "other" metal on metal type is able to be pushed off it's closed position by a drain pipe and better/essential where the wings are well above  normal reach. Both rely on a spring to close off. Leaving the fuel cap unsealed with a bladder tank is worse.   Nev

[IBob]

Good informative thread for me: something to add to the list of simple preflight checks.

[facthunter]

I'll add a bit extra on this. One night when operating a DC-4  (freighter) from BNE to SYD as we taxied in the ground marshaller said shut down everything and be ready to get out. The entire port wing was dripping fuel from the wheel well to the wingtip over the entire lower surface. One of the fuel drains had been replaced and when the thread didn't fit an adapter was put in, placing the new drain fitting about 1" lower. That fitting was located in the fairing to the inner engine, and when the hinged cover was closed and latched ( Done by the despatch engineer) the cover  forced the drain to the open position and it had leaked fuel for 2 and a half hours of flight  plus quite a bit of taxi time right near a 6' exhaust pipe with 18 inch flames coming out of it constantly. The entire wheel well was saturated with fuel. If that had exploded we would just be a statistic... Yours truly was far from impressed.  Nev

[IBob]

😬

[Blueadventures]

2 hours ago, IBob said:

Good informative thread for me: something to add to the list of simple preflight checks.

I carry two spare 'o' rings in my kit and a spare whole curtis valve when on trips away.  as a failed vale can muck up trip and flight plans.  So if discovered after fuel drain I can do a refit of an 'o' ring and no noticeable delay.  no weight or cost involved as light and cheap.

[facthunter]

The reason they get chopped up is some swell and the fuel (petrol) is not a lubricant as diesel is.  A Plain  threaded Bung is OK as a quick fix to get you home. No one could fault that. Nev

[onetrack]

If you're using o-rings in contact with petrol, you're better off to use Viton/Fluorocarbon o-rings, rather than Nitrile/Buna-N o-rings, as Viton o-rings are more durable.

 

https://www.nes-ips.com/viton-vs-nitrile-o-rings/

[Bosi72]

On 30/07/2022 at 8:42 AM, Thruster88 said:

pilot had been monitoring the LED fuel lights for the last hour of flight as they were dropping into the red then back to one green bar continuously. They find them notoriously unreliable

Obviously the LED's were reliable. 

 

According to my calculations, the pilot was ~50nm off the track from the nearest airstrip with fuel arrangements when the LED started flashing. Plus few airstrips without fuel along the track.

 

[turboplanner]

15 hours ago, facthunter said:

The reason they get chopped up is some swell and the fuel (petrol) is not a lubricant as diesel is.  A Plain  threaded Bung is OK as a quick fix to get you home. No one could fault that. Nev

I can't remember, but isn't there a specific O Ring material for fuel and similar applications, with a different colour?

[facthunter]

Never seen them. "O" rigs are common with lawn mower push pull but always leak. Some with Motorcycles too but some vintage stuff still uses CORK.. Most are problematic. Nev

[Yenn]

My Davis fuel drain is at the bottom of the fuselage and fuel comes from the tank via a tap to the drain. That was used for two reasons. 1 The fuel line from the tank to the drain goes between the pilots legs, so a tap makes it safer. 2 The davis drains are known to leak so  tap prevents the tank from being drained during flight.

The only problem is that I have to remember to turn on and off, which is not very onerous. The drain obviously will not pass fuel until the tap is on and the tap is adjacent to the main tap, so obvious when I start up.

[facthunter]

Many fuel set ups have just enough fuel to get airborne when the selector is in the off position. You can have the best motor in the world, and it makes no difference if you've made the wrong selection.. Nev

[Bruce Tuncks]

There was a crash in SA a few years ago where the student SHUT the fuel while checking it was "on".

They finished in a vineyard and the instructor did well to land it parallel to the wires.

They both survived well.

[onetrack]

I can remember a bloke with a microlight at Beverley, W.A. in the 1980's - he took off with the fuel tank tap in the "off" position. He got up to about 100-150 feet, and then dived straight back down again, when the engine stopped. The result was fatal.

The kicker to the story? The bloke was a former crash investigator for BASI! He'd probably examined the wreckage of dozens of aircraft, where the pilot made simple errors - not realising he would become a victim of his own simple error!

[Bruce Tuncks]

In this particular school, they taught their students to touch the control as they went through their checks. Prior to this crash, I thought that was a good idea.

[turboplanner]

10 hours ago, onetrack said:

I can remember a bloke with a microlight at Beverley, W.A. in the 1980's - he took off with the fuel tank tap in the "off" position. He got up to about 100-150 feet, and then dived straight back down again, when the engine stopped. The result was fatal.

The kicker to the story? The bloke was a former crash investigator for BASI! He'd probably examined the wreckage of dozens of aircraft, where the pilot made simple errors - not realising he would become a victim of his own simple error!

This is classic Human Factors, and should have been what CASA taught instead of the crap that no one could relate to. It's not too late to correct their blunder.

 

[facthunter]

THAT came and WENT pretty quickly. it's not a subject where you just tick the box and it's OVER.. It was actually trashed by the way it was dealt with.  Human Factors 101. Don't do something involved with aircraft, unless you do it properly. Nev

[NT5224]

The engine drain on my 320 always gets stuck and I have to manually close it after a fuel drain. 

 

This would be an easy mistake to happen. 

 

Alan

Edited August 2, 2022 by NT5224