Once again in true restoration fashion, plans that are made and committed to print have to be changed or even abandoned altogether. Such is the case in this report and my aspirations to remove the tip tanks.
Tip Tanks Saga
The intention was to lower the wing tip tanks in order to gain access to the wing navigation lights and wiring. A start was made on the starboard tip tank removal by getting together a few 'willing' bodies to help lower it to the ground. Thatís when things started to go square-shaped.
It wasn't so much that I discovered that the tank was only held on by two detonation (det) bolts instead of three, but after the removal of the inboard nut the outboard bolt sheared when I was trying to remove the nut! The problem being of course is that these bolts are 'detonation' bolts of a hollow construction to take the charge and the shear-strength of the bolt material was exceeded before the nut broke its lock. Anyway it wasnít holding the tip tank any more so the tank should have lowered quite easily at this point. No such luck. The one bolt whose nut had undone correctly had its shank well and truly rusted to the aircraft.
Now came the dilemma, I could have removed the tank by force, hammering the bolt through. Although tempting, this could have damaged the aircraft structure in the process and also made the tip tank unusable. So I decided not to proceed and after giving the offending shank a good dousing in WD40 put the nut back on again. The hollow portion of the other bolt was tapped-out and a bolt put in to secure the tip tank to the aircraft again. Not an ideal solution but a prudent one I felt.
That still left the problem of getting the navigation (nav) light to work on the front of the tip tank. After a bit of thinking, this was achieved by splicing wires in to the loom that runs inside a conduit channel on the exterior of the tank. These were then connected to the nav light terminal block in the wing tip. A small hole had to be drilled in a removable panel to allow the wires to get inside the airframe.
Starborad Tip Tank and Nav Light and Port Nav Light (lit)
So much for the starboard tip tank. I then tried my luck on the port one. This had all three det bolts fitted, all with nuts. However thatís as far as it got. Learning the lesson from the starborad tank I didnít want to shear any of the bolts, and none of the nuts were moving under moderate pressure, so once again they were left soaking and the wiring process on the tip tank nav light was repeated on the port side.
That isnít quite the end of the story however as both light mountings had to be removed from the front of the tank and the bulb holders cleaned and made waterproof again. This involved filing off the dome headed screws as they were solidly rusted into their anchor nuts. Then removing the light mounting ring complete with the lamp assembly, replacing the anchor nuts of course, before refitting both serviced lamps. I was rewarded with lamps working on each wing tip, although to be completely honest the port navigation light supply is missing at the wing tip and I had to wire in to the taxi lights to achieve this. A 'Catch 22' situation exists here as the supply is at the wing root, but not at the wing tip and the obvious places to check are underneath the tip tank.
Next on the agenda was to try and make some headway on the fuel system. It has never been my intention to try and get an operational fuel system because, with number three tank missing, and not being in a position to remove the belly tank, it is not practical even to blank off the missing tank pipe connections. However I could see no reason why the fuel tank electrical actuators couldnít be operational and operated from the cockpit fuel panel. This exercises them and serves to keep them in a working condition.
The four fuel pumps of course should not be run, as they rely on being immersed in fuel for lubrication, so to prevent this they have been disconnected and the plugs bagged and sealed up. I did this to prevent any inadvertent operation as the Canberra doesnít have separate circuit breakers for pumps and fuel cock actuators; the supply for the actuators is fused separately after the pump circuit breakers. Not that the circuit breakers themselves gave in easily, they all had to be removed and persuaded to latch correctly again and provide a supply. Getting these fuel actuators working is why a full size aircraft (if you can get it) is so much more fun to renovate than just a cockpit section.
Fuel Actuator and Main Panel Circuit Breakers
Belly Tank Access Panel
Just in case anyone thought that I was spending all of my time renovating the electrical side of things, whilst the belly tank access panel was off, the de-lamination of the double skin, caused by corroded rivets, on the panel edges was repaired. The panel latches were cleaned and the panel re-painted.
Belly Panel Fitted and Before Repaint
Undercarriage Down Lock Micros
Still on the airframe side I noticed during a detailed inspection of the undercarriage that the arms that operate the down lock micro switches, although looking correct, had no split pins fitted to the castle nuts that secured them. Why they were not there I canít fathom, as there would have been no reason to remove them for the move from Marshalls; however, the nuts were tight. Not a particularly hard job but a rewarding one to get right.
Down Lock Microswitch Nuts
During a routine check on tyre pressures the port nose wheel showed zero! This is not immediately noticeable on WF922 because the aircraft is light on the nose and the other tyre can easily hold the aircraft level. Dragging the compressor to the rescue the tyre was re-inflated - the pressure lasted less than a day! Now we have in the museum store a Canberra main wheel but no nose wheels so any thought of a quick replacement was ruled out.
A member of the museum suggested, and even provided, a litre of puncture repair liquid. Putting all my prejudices aside about this repair method, I removed the valve, and squirted this liquid in to the tyre. To even out the distribution of the liquid the wheel was rotated and once the valve was re-inserted the tyre was re-inflated. Initial results were not promising when it went down again within a day. But after a subsequent inflation it held its pressure and has done ever since. I suppose for museum purposes it is justifiable but I still would have reservations about using this stuff on the road.
Port Nose Wheel Tyre
The one thing that has not given any problems until last month was the application of electrical power, the two switch mode 50 amp power units behaving perfectly every time. Until that is, after a heavy rainstorm the battery contactor instead of giving a healthy clunk, started to chatter. Checking out the power units showed it wasnít a fault in that area. But I suspected that the power units were being overloaded and their cut-outs were operating removing the 28v supply and causing it to cycle it as it recovered. So I was potentially looking for a massive short circuit in excess of 100 amps.
Now that sort of current very soon causes overheating and fires so a cautionary approach was needed. I started by removing all of the main bus-bar fuses and held my breath as I selected the battery switch 'ON' again. Just a single clunk and no signs of overload at all. It was then a case of putting the fuses back one by one until the fault re-occurred.
It turned out that water ingress in through the top hatch had short circuited the main start contactor for the Green Satin Rotax 103 inverter. As its fuse is rated at 160 amps my poor power units couldnít cope with this value of current and did what they should - cut the supply. I removed the fuse and put it in to a spare slot so as not to lose it and treated the short circuit area. I will, for the winter month, seal up the top hatch with sealant but I have now put covers on the inside to protect all of the equipment inside the hatch.
Wing Fillet Panels
I still have the intermittent services of another ex-apprentice on the aircraft once a week and he is currently repairing the rear wing fillets that were rather crudely removed/re-fitted during the move from Marshalls. It is, by his own admission, the sort of depth of work that he really enjoys doing and of course his workmanship is superb with a real attention to detail. I have of course several jobs lined up for him that will keep him occupied for the rest of the year at least and I am only too glad to have these extra jobs completed.
Port Wing Fillet Panel