undercar

The undercarriage

Updated on December 20, 2003 file name:undercar.html

The main undercarriage of the MiG-3 was conventional, with inward retractable main gear by pneumatic actuators.
The shock absorbers had a 270 mm stroke, and were filled with a 70/30 glycerine/alcohol mix.
The shock absorber was covered by a rubber manifold to avoid dust adhesion on sliding surfaces. A knee prevented the rotation of the wheel axis.
The tubed tires were 600x180 mm.

The undercarriage bay is closed on its sides, and has a small step all around to locate the doors when retracted.
It has 3 small slots on its rear surface to pass air pipes for the actuator and the wheel brake and some wires.
When the wheel is up, it is locked by a spring mechanism, that can be released pulling a wire.

The doors are divided into 4 pieces for each main gear:

The larger piece is solid to the leg below the shock absorber; two thin cylindrical guides on the upper part of the leg align this piece, while it is free to move upwards/downwards during shock absorber compression/extension. On this piece, a narrow vertical door closed by a spring avoids interference with the retraction locking pin during extreme compression.
The second and third pieces are hinged between the first one and the upper part of the leg, so that they can allow both extraction/retraction and compression/extension movements.

Our best reference for undercarriage colors is this detail from this color photo of an original MiG-3.
Another color photo shows the same color for undercarriage doors, flaps and undersurfaces too.
The shades of the photo looks to have a too orange hue due to the sun's light.
The wheel hub looks green with an alluminium center, while the interior surfaces are probably light blue as the undersurfaces. According to the researches of Erik Pilawski, light grey is not likely in 1941.
Note the use of dark green on some internal surfaces.
It's not sure that all the aircrafts had their undercarriage painted in the same way.

This image of a damaged plane shows rarely seen details.
The flexible cover of the shock adsorber is probably black rubber; here it looks cylindrical, perhaps because it is fully extended.
Here is visible the pin protruding from the wing uppersurface.

left:
On this image, the wheel door was locked closed by hand for photo purposes; in normal functioning, it was closed for the pushing of the retracted wheel on an internal leverism.
In front of the bay, we can see an hole with a pipe protruding from it; this detail is present on the left wing only.

right:
the leg and wheel are well visible here.
Here the wheel disk appears all painted green, while we can see an unpainted center on other photos.
From Istrebitel MiG-3 of Medvedv, Hazanov, Maslov

This detail (from a photo of Jan Koennig of www.Jetmodell.de, allows to see good details of the undercarriage, as well as of the air intakes.
Note that the guide rods near the leg are deformed.

The tail wheel is pneumatically retractable; the extended actuator functions as a shock absorber too, allowing small rotations rearwards.
The tailweel is free-castoring.
The vane is closed by doors, mechanically linked to the gear strut; on early MiG-3s, the doors have an opening to protrude the wheel; on later MiG-3s, the doors were bulged and completely closed.
The well tyre was of the full type, with diameter of 170 mm.
A small chain protruding from the gear could be a ground dispersor for static electricity.

The tail wheel functioning wasn't too reliable, so it was often locked in open position, particularly from late 1941 on.
Sometimes doors were retained, but it was more usual to remove them and to replace them with tissue covers of many different shapes.

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