Twisted: New camera position, aero entry speeds and maintenance matters

G-FUUN has done 50 hours already. So I'm doing the 50 hr maintenance now.

As an update to the 15 hr maintenance issue - the overly large amount of metal found in the oil filter. After sending the filter to Patrick at UL Power for analysis I changed the filter and oil again at 26 hours as a precaution and to see what would be in the filter this time. It turned out to be virtually clean - see below photos. Just one small ali flake and no steel.

I've just cut open the latest filter at 50 hrs and it is completely clean. So this is reassuring that the original filter just had to work very hard to remove all the swarf from the CNC machining in the factory. Clearly they had not washed all the swarf out before final assembly. The engine is not producing any more metal which bodes well.

During this latest maintenance I also noticed what I thought was oil on the pushrod tube of cylinder number 3 - See photo below. After further investigation it seemed to be coming from above the tube and dripping down onto it. So the pushrod tube itself is not leaking. I thought it may be the cylinder head gasket which was leaking. I sent this information to Patrick and his response is posted below:

Andy,

This is not oil but “black stuff” I think. We saw it several times.

Problem is a leak on the exhaust gasket. When engine do not run for a while , condensed water comes in the exhaust tube and even during first run ( starting the engine) condens coming from the sucked air is in the cyl head .

This “black” water comes out along the gasket and falls up the tubes. It looks as oil, but it isn’t.

So no problem in fact. You can try to re-torque the 4 bolts on the exhaust tube, or replace the seal.

It is for sure not the cylinder gasket.

Met vriendelijke groeten,

Cordialement,

Best Regards,

Patrick Denorme

So that's good news. I will try a re torque of the exhaust bolts and see if that helps. If not then I may try a new exhaust copper gasket on number 3.

UPDATE: Today I discovered that one of the exhaust flange screws was missing! That explains the leaking gasket and 'Black stuff' on the pushrod tube. This is not specifically mentioned in the maintenance manual as part of the inspections but I will be adding in a check of these screws from now on. I went round and tightened up all the rest - some of them were a bit loose. Beware - the lock washers do not really work.

After discussing aerobatics with Crispin I noticed that their flight manual had much lower entry speeds than what I had been using. Typically their speeds were 20 knots slower.

After trying these new speeds the aero sequence is now much easier - no longer a tendency to accelerate too fast on the downlines of both the stall turn and the half cuban. Also the whole sequence now takes up less space so the danger of running outside the 'box' is much reduced.

The speeds they determined are as follows (all in knots):

Stall Turn - Entry 125 - Exit 125

Loop - Entry 110 to 125 - Exit 115 to 120 (the slower speed will produce a 'Granny' loop - so best to aim for 120-125 Entry and a 4 G pull).

Roll - Entry 100 to 125 - Exit same speed

Half Cuban - Entry 120 - Exit 125

Half Loop with Half Roll - Entry 130 (50 over the top then accelerate to 80 before doing the half roll)

Half Reverse Cuban - Entry 120 - Exit 120 to 130

Vertical Roll - Entry 135

Avalanche - Entry 130 - Flick Roll on top at 75

Outside Loop - Entry 130 - Exit 70

Rolling Circle - 120

I've also tried a new camera mount position - on the tailplane - which is giving a useful view for analysing my mistakes with the aero sequence. Only problem is the lens gets oiled up during the stall turn and the image then gets blurry. So I have just moved it to the right hand side tailplane and hopefully this will cure that problem. This view is of no use on the upline of a vertical though so I may supplement this with a wing view later.

The competition is just a month away from today so I need to up my practising schedule.

Only bit of ali from the 26 hr filter change. And no steel which is the main thing to worry about. The 50 hr filter is completely clean with no metal at all.