I started on the Xair on Monday as planned and all went swimmingly until I came to start the engine and fuel came squirting out of the inlet joint on the rear carb from under the jubilee clip holding the fuel hose. I surmised that the tube end had perished as I’d replaced some of the tubing for that same reason last autumn thinking that I’d be replacing all of it due to age when I eventually got the aircraft to France. Sure enough, this was a small piece that I’d left that had decided to let go over the winter and luckily there was a good length in the scrap bin in the hangar that fitted the bill nicely to replace the piece that had perished.
Eventually I got to start the engine and with the primer pump off, all was well. With it on fuel was still finding its way out so evidently there was still some kind of fuel delivery problem but as there were no leakages while the engine was running under the pressure of its Mikuni fuel pump, I decided that I’d do a longer engine run and some taxi tests with a couple at take off revs along Clipgate’s runway.
I forgot to mention that over the winter someone had walked into the Xair’s pitot and snapped it off. I managed to find an old piece of brake pipe to replace it with but unfortunately when I fitted it there was no one handy to help me check afterwards that the pitot was actually working.
I thought that I’d do it while I was doing my taxi checks. This didn’t happen of course, because there was a tricky little crosswind and I was concentrating more on controlling the aircraft than checking its airspeed, especially when I was doing my couple of hops. Other than that the engine checks including the full power runs went perfectly smoothly. See how each little thing is adding up in the classical way…
Then it was time for lunch after which I thought that I’d do a flight of 1 1/2 hours to clear some of the old fuel that I’d left in the tanks since December so I could put some fresh in and also make sure that the engine was up to the mark for the Channel crossing. I noticed immediately during the take off run that there was no airspeed indicator but as I know the Xair well enough I decided to continue the flight using engine revs and experience and deal with it when I returned. And then, of course, it happened.
I can’t have got to any more than 50 feet (15 metres) or so before the engine began to fade. I immediately pushed the nose down to achieve best climb speed but there was only one problem with that. I had no airspeed indicator. Then the engine speeded up again only to fade again after a few seconds and the cycle then began to repeat itself, so a classical fuel starvation problem. Or was it? What if the engine was getting too much fuel – if that was the case turning the primer pump on could well have killed it completely so as I could hold altitude but not climb, I thought it best to leave things as they were.
I did have options. To the right there were some pretty decent fields where I could put the Xair down but they were in a valley and that would have meant a big derigging job and trailering it back to the airfield, which I didn’t fancy. While I was thinking about it though, although the aircraft wouldn’t climb, it had settled into stable flight albeit at low altitude and low airspeed and I wouldn’t recommend any low hours pilot to do what I decided to do as I know the Xair and its handling characteristics very well. I knew that I’d never be able to complete a full 360 degree circuit and return to land into wind on the take off runway. However, I thought that so long as the engine remained in its present state, I’d be OK for a 180 and a landing downwind.
The upside of this plan was obvious. The downside was that I’d be flying at low level over cropped fields (cabbages I think) and if I was unfortunate enough to go down I thought that I’d walk away but the Xair would get a bit messed up. The other downside was that I’d be landing with a 20kmh tail wind but to heck with it, I decided to go for it.
The strength of the tail wind really only became apparent the closer I got to the runway and I ended up touching down a bit hard about half way down. The Xair bounced a little but the second time I held it down and braked like crazy as the trees at the other end rushed towards me -but no problem that’s what long grass is for at this time of year at the side of the runway. So I ploughed into it and decided that in the last resort I’d broadside the aircraft to kill the speed before arriving at the trees.
But there was no need. One of the chaps at Clipgate was coming dashing down the runway in his car to find out what sort of sticky end I’d come to only to find me taxying calmly back up towards him with no harm done. The funny thing is that I wasn’t perturbed at any time during the whole course of events. Even though I didn’t have an airspeed indicator I’d pushed the nose down instinctively as I’d been trained to. I’d checked out my options and made what I thought was the best choice for me under the circumstances.
But lastly I’d followed the old Bob Hoover maxim – always fly the aircraft the whole way through the crash. He was right and on Monday it worked for me.
Now onto today. It was obvious that I wouldn’t get away as I needed to solve the Xair’s fuel problem and not having brought any tools with me, I went out yesterday to buy a few. This morning I stripped the carbs and finding them as clean as a whistle, I decided to go over the whole fuel system. I found a jubilee clip swinging in the breeze at the exit joint of the electric pump so surmising that that was the source of a pressure loss I tightened it and did another couple of fast short taxies at take off power. Everything looked good, although the fuel pressure was on the low side as it has always been.
The next test was to tie the tail to a heavy object and give the engine a minute at take off and climb out revs. I would have liked to have raised the nose to make it more realistic but couldn’t lay my hands on anything that I could safely put under the nose wheel, but anyway, the test was far from satisfactory. The fuel pressure at full chat was lower than at idle so the Mikuni fuel pump has to be highly suspect. The test indicated that you need the pump on at climb out much like a Group A and that’s not right
I was brave (or reckless) enough to try an air test using the pump as above and the engine was as sweet as a nut. However, I descended over the property of the Xair’s previous owner and had another butt clenching moment climbing away so decided to cut the flight short and head back to Clipgate with the pump on the whole way.
When I was here in the autumn getting 24ZN ready to go I bought a Mikuni refurb kit and thought that I had it with me now, but I don’t. So I’ve got one on order with 24hr delivery and will refurb the pump tomorrow. Hopefully that will then solve the problem and I should have done it when I originally intended to. Will I get away the day after? I’ll have to wait and see. I did 1 hr 20 mins today but there’s no way that it could go down through France the way it is. It’s got to be right and if I get off with just replacing a bit of fuel hose, the pump and the plugs, I’ll have got off pretty lightly I think.