It has been quite a while since I wrote about what I've been doing in the hangar. Well, I'm still working on the Cessna 402 for 'Wings with Word' with another MAF UK apprentice. The good news is that we have finally finished the spar strap modification and got the engines installed and rigged. Below are some photos of the finished job. The first shows the engine in place. The second has the nose bowl in place (making sure the engine was set correctly on its mounts). The third shows the engine with the propeller, spinner and top cowling on (although we removed it again so we didn't keep on hitting our head on it whilst installing the landing gear). The side cowlings were going to be going on as well, but that was before we found inter-granular corrosion and chaffing which will require more work.
Now that the engines are done, it's time to get the aircraft back onto it's wheels. That sounds SO much easier than it actually is. Every push-pull rod had to be removed and inspected, all the bolts, nuts and washers had to be checked for wear and corrosion, and specific inspections had to be performed. One specific inspection involves NDT (Non-Destructive Testing) using florescent penetrant. The part has to have all paint and primer removed and be totally clean. Then the penetrant is sprayed on, left to dwell for about half an hour and then removed. A developer is then put on which draws out any penetrant that has seeped into cracks. You use a black light to highlight the cracks. Follow the link ( http://www.youtube.com/watch?v=1cl2ULh0_ss&feature=email ) to see a short example of florescent penetrant.
All along we have found problem after problem, but we have finally managed to hang the main landing gear. The photo below shows the left hand main landing gear strut on the table being inspected. The two parts on the lower left are the torque knees. One of the bushings had to be replaced, filed down and reamed to the correct size.
The landing gear on the 402 is a retractable system. This means that the once the aircraft is up in the air, all three wheels are retracted into the fuselage/wing and doors close over them. There are two types of systems: the first is a hydraulic system that uses hydraulic fluid and pistons, whilst the second system is all rods, bell-cranks and pivots. This 402 uses the second method, and you can see some of the mechanisms in the photos below. The first photos shows the main wheel door mechanism. You can see the main push-pull rod coming through from the fuselage on the left and the door push-pull rod hanging down. The second photo shows some of the nose wheel mechanism.
We have finally got the main landing gear hung and have installed the wheels. Unfortunately the money has run out again, so we cannot purchase the things we need to finish the job until the mission raises more funds. We will need to buy new brake cylinders (damage found due to special inspections and corrosion), nose wheel halves (corrosion), wheel bearings (water marks and overheating), high pressure strut valves (incorrect ones installed) and numerous hardware.
There will be more updates as we proceed with getting this aircraft complete and back into the mission field.
