Should "Check fuel tank breathers are free of obstruction" be part of every daily"?
Thread Starter
Should "Check fuel tank breathers are free of obstruction" be part of every daily"?
I am posting this in the hope that it might help someone else avoid a potentially dangerous situation.
I had a fuel starvation event in the Bonanza on Monday (don't tell Wally!). As it turned out, it was not a big deal - but it could have been!
I was in cruise at FL150 at the time and just happened to be watching the fuel flow guages when the digital fuel flow numbers started to wind down and the needle on the analogue guage headed north. I barely had time to think "What the @#$%", when the engine died.
I had changed tanks about a minute earlier, but that is just a co-incidence and not relevant to subsequent events - but my hand was already headed for the tank selector when the engine died. A change of fuel tank immediately restored power. I had drained 1.5 hrs of fuel from that tank in 30 min blocks, alternating with the other tank.
My first thought was that I had missed the detent when changing tanks, but I have done 1000+ tank changes in that aeroplane with no problems. My next thought was that I had a leaking fuel tank and had vented fuel overboard leaving an empty tank - but the fuel guages didn't support that. As it was I did drain another 30 min out of the tank which was enough to get me home without having to divert.
As indicated by the title of this thread, the problem was a blocked fuel tank vent. On landing I extracted insectoid material from the vent outlet for that tank with a length of lock wire. I flew the Bo again yesterday and drained 2.5 hrs continuous from that tank with no problems.
I have read about this occuring, but in 30 yrs and 3000+ hrs I have never experienced it before. The fuel being pumped out of a sealed rubber bladder had collapsed the bladder and obstructed the fuel outlet.
I had a hint the previous evening that something was amiss but I didn't pick up on it! When I removed the cap from that tank to refuel after a long flight, air was sucked into the tank! That should have alterted me to the problem.
I religously put the cover on the pitot to keep bugs out but have never paid much attention to the fuel breathers. It is not easy to cover or block off the breathers on the Bo while on the ground.
I now have an additional item for my daily pre-flight inspection.
Dr
I had a fuel starvation event in the Bonanza on Monday (don't tell Wally!). As it turned out, it was not a big deal - but it could have been!
I was in cruise at FL150 at the time and just happened to be watching the fuel flow guages when the digital fuel flow numbers started to wind down and the needle on the analogue guage headed north. I barely had time to think "What the @#$%", when the engine died.
I had changed tanks about a minute earlier, but that is just a co-incidence and not relevant to subsequent events - but my hand was already headed for the tank selector when the engine died. A change of fuel tank immediately restored power. I had drained 1.5 hrs of fuel from that tank in 30 min blocks, alternating with the other tank.
My first thought was that I had missed the detent when changing tanks, but I have done 1000+ tank changes in that aeroplane with no problems. My next thought was that I had a leaking fuel tank and had vented fuel overboard leaving an empty tank - but the fuel guages didn't support that. As it was I did drain another 30 min out of the tank which was enough to get me home without having to divert.
As indicated by the title of this thread, the problem was a blocked fuel tank vent. On landing I extracted insectoid material from the vent outlet for that tank with a length of lock wire. I flew the Bo again yesterday and drained 2.5 hrs continuous from that tank with no problems.
I have read about this occuring, but in 30 yrs and 3000+ hrs I have never experienced it before. The fuel being pumped out of a sealed rubber bladder had collapsed the bladder and obstructed the fuel outlet.
I had a hint the previous evening that something was amiss but I didn't pick up on it! When I removed the cap from that tank to refuel after a long flight, air was sucked into the tank! That should have alterted me to the problem.
I religously put the cover on the pitot to keep bugs out but have never paid much attention to the fuel breathers. It is not easy to cover or block off the breathers on the Bo while on the ground.
I now have an additional item for my daily pre-flight inspection.
Dr
Last edited by ForkTailedDrKiller; 22nd Jul 2009 at 02:01.
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They are included on our preflight checklist. 'Fuel Tank Vents - CLEAR of OBSTRUCTIONS'
It doesn't take long to have a quick look and keep walking.
And it's much better than giving yourself a heart attack when the engine coughs.
I bet you'll check them from now on after that little scare.
Maybe an additional checklist item should be "Change of Jocks - Onboard"
It doesn't take long to have a quick look and keep walking.
And it's much better than giving yourself a heart attack when the engine coughs.
I bet you'll check them from now on after that little scare.
Maybe an additional checklist item should be "Change of Jocks - Onboard"
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Thanks Doc for bringing that to my attention.
About 6 months ago, I removed one of the fuel (aux) caps off the Baron and got a a big whoosh of air. At the time I thought 'why did it do that?" and then did not give it another thought. Your article has now alerted me to the potential problem and I will certainly be more vigilent in the future.
About 6 months ago, I removed one of the fuel (aux) caps off the Baron and got a a big whoosh of air. At the time I thought 'why did it do that?" and then did not give it another thought. Your article has now alerted me to the potential problem and I will certainly be more vigilent in the future.
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Had it happen in a Tiger Moth, the non-return breather on top of the tank has corroded closed. Impossible to detect from the outside - short of sticking the gob on it and giving it a blow.
After an engineers inspection it was assumed the engine failure was due to carby ice, i agreed, given the conditions on the day were perfect for it. Of course she started up beautifully after we had opened the tank a few times! Thankfully the owner of the field was nice enough to let us slash a strip and out I flew.........5 mins later........ I learnt a lesson that day
The second farmer was just as nice, though she got trucked home.... I walked.
Ironic really, the Tiger's the only aircraft i've flown where checking the breather isn't part of my Pre-Flight, mainly because of accessibility.......it is now.
After an engineers inspection it was assumed the engine failure was due to carby ice, i agreed, given the conditions on the day were perfect for it. Of course she started up beautifully after we had opened the tank a few times! Thankfully the owner of the field was nice enough to let us slash a strip and out I flew.........5 mins later........ I learnt a lesson that day
The second farmer was just as nice, though she got trucked home.... I walked.
Ironic really, the Tiger's the only aircraft i've flown where checking the breather isn't part of my Pre-Flight, mainly because of accessibility.......it is now.
Last edited by Wanderin_dave; 22nd Jul 2009 at 03:25.
Yes a good lesson.
My vents get mud wasp nests in them but fortunately have an tiny hole further down the line to act as a secondary vent should the main vent be obstructed.
Little bits of fly wire cable tied over the ends of the vents have hopefully solved the problem.
With wet wings I imagine the fuel flow would stop a lot sooner with a blackage than than with the bladders.
My vents get mud wasp nests in them but fortunately have an tiny hole further down the line to act as a secondary vent should the main vent be obstructed.
Little bits of fly wire cable tied over the ends of the vents have hopefully solved the problem.
With wet wings I imagine the fuel flow would stop a lot sooner with a blackage than than with the bladders.
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Doc,
When i was flying them on charter, the operator i worked for was paranoid about that very incident and included a piece of hose which fitted over the breathers to check the flow by blowing through them and some wire to clean the inevitable build up out.
Glad it all went well
Load it
When i was flying them on charter, the operator i worked for was paranoid about that very incident and included a piece of hose which fitted over the breathers to check the flow by blowing through them and some wire to clean the inevitable build up out.
Glad it all went well
Load it
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Similarly, heard recently about a composite aircraft owner had his tanks sealed at the vents by a similar event. Supposedly due to the internal de-pressurisation the tanks delaminated from the external skin. Both of them. Ouch.
Fly screen mesh rolled and inserted in the end gives the bugglies nowhere to live and breathes well still.
I'm from the govt and I'm here to help you.
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Fuel Tank Vent Problems
Way back when airliners had props a DC4 Skymaster overnighted at Perth Down Under. Tanks were topped up. Next day was hot and the fuel started dripping out of the wings' integral tank vents. Some non thinking idiot put some bungs in the vents.
Yes - it took to the air with the bungs in place. Result - wing surfaces sucked in and ruined. Powerful suckers are those fuel booster pumps.
Then there was the time we flight testers wanted to force fuel out of a repositioned fuel vent back in the tail of a Canberra to prevent any vented fuel going anywhere near the horizontal stab trim motor. A USAF TP on exchange to the RAAF launched the Canberra out of Darwin for the venting trials not knowing that the convoluted tubing to the new vent was kinked enough to be blocked. To force fuel venting fuel transfer was commenced from the wing integral tanks into the full bladder fuel tank sitting on top of the weapon bay and the control rods to the tail. The bladder fuselage tank became pressurised enough to deform its floor and Jam the rudder and elevator controls.
Ejection was an option but brute strength was just enough to permit a hairy landing and earn a USAF TP a British/Australian Air Force Cross.
Way back when airliners had props a DC4 Skymaster overnighted at Perth Down Under. Tanks were topped up. Next day was hot and the fuel started dripping out of the wings' integral tank vents. Some non thinking idiot put some bungs in the vents.
Yes - it took to the air with the bungs in place. Result - wing surfaces sucked in and ruined. Powerful suckers are those fuel booster pumps.
Then there was the time we flight testers wanted to force fuel out of a repositioned fuel vent back in the tail of a Canberra to prevent any vented fuel going anywhere near the horizontal stab trim motor. A USAF TP on exchange to the RAAF launched the Canberra out of Darwin for the venting trials not knowing that the convoluted tubing to the new vent was kinked enough to be blocked. To force fuel venting fuel transfer was commenced from the wing integral tanks into the full bladder fuel tank sitting on top of the weapon bay and the control rods to the tail. The bladder fuselage tank became pressurised enough to deform its floor and Jam the rudder and elevator controls.
Ejection was an option but brute strength was just enough to permit a hairy landing and earn a USAF TP a British/Australian Air Force Cross.
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PF.... in my case...YES! 
In yours probably not!
Get some big red pipe cleaners from the local Kindy..... shove them in and remove before flight along with everything else. If you forget them it wont kill you wither!
happy now PF?..... You can shove them up ya nose too!!!
J
Friendly banter PF
In yours probably not!
Get some big red pipe cleaners from the local Kindy..... shove them in and remove before flight along with everything else. If you forget them it wont kill you wither!
happy now PF?..... You can shove them up ya nose too!!!
J
Friendly banter PF
A known problem with single-engine Cessnas is misalignment of the fuel vents. Location is quite critical, and the tolerance is only about 8mm.
If not installed/aligned correctly, fuel venting can easily occur.
If not installed/aligned correctly, fuel venting can easily occur.
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Blocked Fuel Tank Vents.
In the 1960's I was returning to base in a C172 when the engine started to splutter. In my quick look around I noticed the left fuel tank drain in the lower surface of the wing going up into the recess. I opened the window and pressed the drain up which let air into the tank, the engine ran and we landed ok. There was quite some distortion in the tank. In those days we used to do aerial photography and so had disconnected the window hinge which allowed the window to float up towards the bottom of the wing, which helped me get to the drain plug.
Regards
Tmb
Regards
Tmb
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Damn fine point FTDK. Thanks for posting. I've read/heard of similar events in the past.
If memory serves, not all aircraft types have an "external" tank vent. Some (similar with cars, trucks etc.) have vented fuel-caps. A similar situation can arise if those vents should become blocked for any reason or the caps unwittingly be replaced with non-vented caps. Your AFM should have the good oil on that, or have a yarn with your LAME if in doubt.
Thanks for posting. I've read/heard of similar events in the past.If memory serves, not all aircraft types have an "external" tank vent. Some (similar with cars, trucks etc.) have vented fuel-caps. A similar situation can arise if those vents should become blocked for any reason or the caps unwittingly be replaced with non-vented caps. Your AFM should have the good oil on that, or have a yarn with your LAME if in doubt.
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We learn by experience (if we live to tell the story). Yes, I too have been guilty of not checking fuel vents on a Rockwell Commander.....same result FTDK. Fuel starvation enroute Canberra to Port Macquarie (during winter). My guardian angel got me into Scone where i found.....yep you guessed it, mud from a wasp nest. From that day after I check vents methodically on the daily. Sometimes the older and more experienced we get the more complacent we become. The coughing and spluttering soon had me dropping the coffee and grabbing switches.
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FTDK, sir you might want to check your bladders as well, I had a 182 on line that went for a lap with the fuel cap off, which apart from sucking the fuel out - deformed the bladder, thought nothing of it bought a new fuel cap and off we go again for another 100 or so hours, the bladder then fretted against the interior of the wing and had to be replaced. (not a cheep exercise).
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Should "Check fuel tank breathers are free of obstruction" be part of every daily"?
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AERO's right...Had the same problem with a C206 bladder came unclipped from the top of the wing and in doing so broke the clips off all together. Sure was an expensive exercise...From then on, all fleet had fuel vent covers to go with the pitot covers.
chimbu warrior is also right about the alignment of fuel vents...Can also be the major cause of fuel tanks not feeding evenly to the engine of C150 thru to C182's
chimbu warrior is also right about the alignment of fuel vents...Can also be the major cause of fuel tanks not feeding evenly to the engine of C150 thru to C182's