After refurbing 24ZN’s Mikuni fuel pump and fitting two new in-line fuel filters obtained at a local motor factors I did some high speed high power taxies followed by another test flight. There was a big improvement when at low revs but for safety reasons, I switched the electric pump on for take off and climb out. So far so good.
I then switched the pump off in the cruise (5600 rpm ~60 mph) and the engine continued running sweetly but with fuel pressure on the minimum, 0.2 bar. I made it as far as Faversham (15/20 minutes) and the engine briefly pulled it’s trick again so it was time to switch the pump back on again, head back to Clipgate and look even more deeply into the problem.
I got back without incident with the engine running fine with EGTs both good and the fuel pressure at a healthy 0.4 bar with the electric pump on continuously. However, I’m not satisfied with that as I don’t want to fly the length of France, let alone the Channel, relying on an old, unproven electric pump.
So I was thinking about replacing all of the fuel lines when something hit me. Whoever tinkered with the Xair last (at least 11 or 12 years ago) had replaced all of the fuel hose from the hand primer up to the Mikuni with 6mm hose. Now I reckon that 6mm is probably of large enough diameter to run from the pump to each carb but NOT as the main supply to the pump as it will not supply enough fuel for the engine at high revs for an extended period. So I decided that I’d replace all of the small bore hose that I just mentioned with new 7.6mm.
And know what? After doing so the problem has been solved. The fuel pressure is the like of which I’ve never seen before in the whole of the 11 years that I’ve known this aircraft. I also found more split/perished ends on the old tubing that I stripped out and the bonus is that after switching off, the pressure now only falls very slowly leaving a small residual, as it should. And the pressure now holds up at take off revs without the need of the electric pump, falling only slightly as the throttle is opened wider.
The shocking thing is that this aircraft has been officially inspected several times over the years by different BMAA inspectors for annual Permits to Fly. These inspections are mandatory and are at the expense of aircraft owners and are required for ‘safety’ purposes. None of the inspectors concerned had picked up on this obvious fault which had the potential of bringing down the aircraft as my own experiences had shown.
High speed taxi runs having indicated that I had a normal working fuel system, I just needed to confirm this with an air test. However when I taxied back to the hangar and switched off, the engine kept running so at least one magneto wasn’t earthing. I was 99% certain that the problem was in the dreaded Xair multiconnector which I must have disturbed when I changed the vacuum pipe. It can be a problem in older aircraft and I cut my French Xair’s one off and replaced it with a bunch of single connectors.
It didn’t take too long to sort out the magneto earthing problem – it was in the multi-connector as I’d suspected. It took a couple of goes because in the process when I pushed the two connectors that had moved downwards in the bottom half back in again and remade the main connector, that pushed the two top parts out, which was hard to see, leaving the connections still not made. That multi-connector is a lousy arrangement and if I’d had my tools here I’d have taken it out.
But anyway, all was eventually sorted and I waited until the evening to do an air test as it had been so hot during the day. And I couldn’t believe it. I had a mag drop on one side and I’d gone from having an engine that was all-clear and running perfectly to one with the symptoms of a stator problem – yes, the well-known old Rotax 582 problem. Been there, done that with my old French Xair.
There was a slim possibility that it was due to eg fouled plugs from starting/stopping the engine while I was sorting the mag earth problem. If it turned out to actually be a stator problem I’d be placed in a difficult position, depending on its severity, as revealed during an air test, as I don’t have the tools here including eg a flywheel puller to do the job. And I don’t have a multimeter with me either to check the resistance of the relevant ignition coils. With the weather beginning to slowly collapse looking as though an early departure would be impossible anyway, all that I could do was go for an air test the following day.
Now I am ashamed to say that I have a confession to make. During the air test, at around mid-day yesterday, for the first time in over 50 years since I first began flying I ran out of fuel. I’d thought about adding some before I went off but decided not to as that would give me more time to burn off the old stuff in the tank and when I’d topped up on my return, I’d have had nearly all fresh fuel on board when I did eventually make the flight.
I’d filled up after my last check flight and had done only less than 1/2 hour more when I’d aborted the next one at Faversham but I hadn’t taken into account that I’d done numerous full power test runs since then, plus I’d lost a bit when I’d replaced the fuel hoses – probably more than I thought actually.
I was in such a hurry to get into the air yesterday that I didn’t visually check the fuel contents as I should have done. The result was that I was blithely flying back to Clipgate at 1800 feet about 4 miles north-east of Headcorn when it all went quiet up front. I realised what had happened when the electric pump wouldn’t give me any pressure so immediately declared an emergency (mayday) with London Information with whom I’d previously been in contact (readability 5 on an old 25kHz A20) and stated my intention to ‘land out’ as glider pilots say.
I had a huge choice of fields and well before I landed I told the controller that I’d found a huge field with sheep and goats (so short grass, no crop like all those surrounding it) and that I would be able to carry out a normal glide approach landing, which I did. I couldn’t contact London on the ground so it was a while before I could make a phone call to NATS and in the meantime they apparently had time to launch the D & D helicopter and I was told when I contacted them again later that they’d located me from the position info that I’d given, seen that I was safe and returned to base.
But anyway, no harm done and after adding fuel I got out of the field and back to Clipgate in under 20 minutes. The Xair is not perfect and does appear to have the beginnings of a stator problem. From my experience with my old French Xair I’m certain that it is, however, good for the flight south (whenever the weather allows) and I’m just left red faced.
I always plan to have at least 30-60 minutes of fuel left in the tanks at destination. This is the first time ever that I’ve overlooked my own rule and could have paid the price for doing so – possibly a broken aircraft. I think that I’m paying the price of trying to get an aircraft that hasn’t been flown for several years back into the air with minimum work (because I aim to do a proper job down south). But this was out-and-out my own fault, in some ways brought about by my anxiety before taking off on a ‘make or break’ check flight. No excuses, however. You must never allow yourself to be distracted from the fundamentals. I’ve always believed that and this has brought it home to me in an unforgettable way.
When I called my mayday (in my book, total loss of engine is a mayday, not a pan), the services responded impeccably and nobody should ever be concerned about declaring if facing any kind of emergency. If in doubt, declare. London Info stopped all other traffic while dealing with me and would have continued for longer I’m sure if I hadn’t told them that I’d found a great field and was no longer concerned as I knew I could get in with a glide approach. I even called final just before I landed but couldn’t get them again when on the ground unfortunately.
All’s well that ends well but it’s embarrassing to say the least 😕