Monday, February 15, 2010

MiG-23 Tire Change

Following the taxi test of the MiG-23 at the Cold War Air Museum during Soviet Big-Iron Saturday, we began noticing that the port tire was losing pressure. We had anticipated replacing the tires that came with Bord 022 and fortunately, our replacement set was already on hand.

A particularly handy thing is to keep a spare tire already mounted on a spare rim to minimize the time needed to "rescue" an aircraft in case a tire should "blow", or go flat during operations. One of our "spares" was already mounted on a rim, simplifying this replacement process.

However, this did not eliminate the need to read the instructions. The MiG-23 wheel assembly consists of approximately 60 individual components, not including nuts and washers (so much for Soviet Simplicity, this time anyway). Here Jon is seen trying to figure out what does and, more importantly, does not need to be taken apart in order to replace the wheel.

The massive disk brake mechanism incorporates an anti-skid system and uses six big rotors and seven heavy-duty stators in each wheel.

The amount of heat that can be generated by the brakes poses a serious bursting issue with the tires. To prevent this, the designers at MiG incorporated two interesting features. The first is an electric fan. Mounted in the center of the axle, the fan activates when the "weight on wheels" switch signals that the aircraft is once again on the ground.

Shown with the axle fan is the nut that holds the wheel on. A keeper ring goes between the fan mounting bolts and the axle to keep the fan and the nut from turning as the tire turns. In the picture below, Jon is inspecting the electrical connection for the fan motor in the center axle.

The second feature is a solder plug that melts at 140°C, allowing pressure to escape before the tire can burst. On fast landings or after any extensive brake use, MiG-23 pilots may alert their ground crews so the wheels can be doused with water so the plug doesn't melt.

Sliding the tire on over the six rows of rotors is a little like working a combination lock, but with a little light on the subject and some patience, Jon and Sean were able to get the tire on fairly easily.

All that remains is re-mounting the mud guard, applying safety wire and cotter pins to various keepers, and... of course... next, the replacment of the starboard tire.

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