Cessna 210 gear problems
I had an interesting snag on a Cessna 210L many years ago. The pilot reported that the plane was ‘lurching’ during flight - speed up and slow down etc. “You mean the engine is surging” I asked.
The reply was negative, RPM, fuel flow, manifold pressure all stable. No change in audio pitch of engine. However, the aircraft was due for its Mandatory Period Inspection (MPI) so I carried out normal ground runs and everything checked out. I figured out that it must be aerodynamic, but what? Everything in its place and secure. No loose panels, control flutter or trim tab issues were visible.
We jacked up the plane and carried out gear retractions. The gear went up almost all the way, enough to be out of the pilot’s vision and then changed direction and lowered slightly, then switched back to up a bit and then back down a bit and so on. This was before the modification to incorporate a ‘landing gear motor running’ warning light. The problem would have been resolved had the pilot seen the light on continuously and therefore he would have known that he had a gear problem. At no point could the pilot see that the gear was not actually fully up, because there was no mirror to see the full gear retraction. A note here is that the warning light modification is an excellent idea, whilst the inclusion of a mirror to view the nose gear is a great added safety feature.
So, what was the problem? It turned out that the squat switch wiring had broken inside the plastic sheath that protects it. The sheath and wiring are routed through an almost 90-degree curve in the wheel well and as the gear retracted the bending action caused the wiring to disconnect, meaning that the squat switching had not been made. The landing gear would then start deploying and the wiring would reconnect with the squat switch active again. The gear would then return to the up position until it disconnected again, whilst the process repeated itself over and over causing the oscillation the pilot experienced.
Once the diagnosis had been made the problem was easy enough to fully repair. However, this was a rather unusual situation as it was not possible to see the condition of the wiring inside the sheath without stripping all the wiring out. This was an isolated incident that I have never experienced since in all the years I have serviced Cessna 210 types.