Cessna fuel system

[CyclicRick]

Hello all, I have a question for a Cessna engineer.

Aircraft: C182Q fitted with long range tanks (300 litre)
Engine Continental 470 (230bhp) with approx 100 hrs since new on it.
1/ before a flight I noticed that the rubber tank (right hand wing when viewed from the pilots seat), upon opening the fuel cap was nearly poking out of the hole!

2/ An engineer said that the tank had come loose and hooked it back in (I've personally never seen exactly how the tank is "hooked up" inside) Re-hooked ok.

3/ Said tank did it again, another enginner re-hooked the tank and said that the air pressure system was blocked creating a vacuum in the right hand tank, fixed..ok!

4/ Recent flight in the Alps thank goodness up at around 9 to 10 thousand feet, right hand tank empty, swapped tanks and after about 10 mins left hand tank empty! Forced landing in a field as a result. Fuel tanks showed both quarter full (I know they can be unreliable)

Flight was calculated at 4:20 duration, fuel uploaded for 5:30. Fuel ran out after 4:05. RPM 2300, MAP 21-22inches. Flight manual says 47.6 litres/hour consumption. I took 50litres/hour for flight planning purposes.

Q1: Can the engine use that much fuel without warning? (previous experience on long trips concurred with FM)
Q2: Could it be possible that fuel was sucked/forced out of the
fuel cap or the forced air system under left the wing?

The aircraft is now being repaired by the engineer who last played with the tanks at his own workshop( friend of the owner), so I'm not sure what is going to come out of it.

I'm a professional helicopter pilot with many thousand hours of flight time under my belt and I'm normally VERY careful with my fuel management but something was wrong here and I don't think it was me to be blunt.
Any ideas on what might be the cause would be of interest to me anmd no I'm not after the engineers guts either, I just want to know

Thanks

Rick

[CyclicRick]

Wow slow down...I didn't expect THAT much response!

never mind :(

[sprocket]

:D Rick, the cessna fuel system is a simple one yet an 'obvious' problem can still be hard to nail. Lack of replies suggest that your engineers would have probably found and corrected the problem by the time someone attempted to answer your question.

The 'air pressure' system I presume is the tank vent. It should have a check valve in it ie, it will let air in to replace fuel used but should not let air out. If it failed in the closed position you may end up with the problem you described.
Also the vent can be blocked by foriegn objects, one example we get here in Oz is mud wasp nests if the vents are not covered when the A/C is parked.

If your tank bladder had already semi collapsed, lets say from a previous flight , the next fill will give a higher reading (on your qty gages) than what is in your tank. Therefore a lot less endurance.

Good Luck.

[Sunfish]

Sprocket probably has it right.

There is an article somewhere in an Australian Flight safety magazine about how a Piper had what might be a similar problem.


In that case the fuel tank caps were replaced with identical ones that were non vented instead of vented. (model changes Cherokee or Warrior or some such).

So aircraft sucks fuel out of bags and collapses them because there are no vents, pulling everything out of alignment.

Next flight the pilot topped tanks up to brim and dipped them - everything showing full tanks - and then ran out of fuel two or three hours later.