Piasecki HUP Landing Gear

An aircraft's landing gear is often inaccurately depicted in a model aircraft kit for various reasons, but primarily due to reliance on a museum example that does not have properly inflated struts. Helicopter landing gears are even more likely to be incorrectly represented on a model particularly when they involve multiple small struts for which proper alignment features (or adequate illustration in the assembly instructions for that matter) are provided.

The Piasecki HUP main landing gear is an example. It consists of a main shock strut that is mounted upside down (the piston extends out of the top of the strut) with lateral and fore/aft loads reacted by two small fixed struts attached to the bottom of the strut and the bottom of the fuselage.

Note that in this illustration, I relied on Piasecki drawings that showed too long an outer cylinder relative to the total length of the strut.

When the strut is properly serviced, on the ground there will be 2.1 inches of chrome-plated piston above the cylinder and the top of the chrome will be 12.44 inches from the attach point of the strut on the fuselage.

 Also note that when the HUP is off the ground, the wheels drop down about 11 inches to provide the shock absorption of a high sink-rate landing.