The following important information regarding Nanchang fuel vents was sent to us by one of our members. AWAL applauds safety-related input but, pending official review, does not necessarily endorse the stated views.

The Nanchang had 10hrs of flight testing which we do in most of our aircraft and was hangered most of the time .The two days in which it was out side it had its canopy cover on and its pitot.I was doing a demonstration flight and with a passenger on board when and I was only going up for twenty minutes .I had 50lts in the right and 25lts in the left which is plenty of fuel as we do all our test flying above the field .I was on climb passing 1500ft and North east of the field when it just stopped ,there was no coughing or spluttering just stopped .Immediately lowering the nose as we were in a steep climb I wobbled the wobble pump but and full deflections of the rudder to possibly free up any fuel non return valves which was a last resource to regain fuel as I new I had plenty .I landed back on the runway and double checked things as I already had done a pre-flight and had flown that day for approx two hours .The cause of the engine stopping was that in a very short amount of time possibly over lunch a hornet wasp had got lodged in the fuel vent and it would then not feed out of that tank as it only requires very little pressure to stop the fuel feed .The lesson I learned was that some Nanchangs have a very fine mesh filter over this vent line and it was something that I did not worry to much about as I already had flown down the tanks in previous test flights confirming our fuel calibrations .The lesson I learned was to make sure every Nanchang I deal with has the fine mesh over the vent line and as part of my pre-flight I now blow up the vent line confirming that the system is clear.