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The moment at which a wheel of a landing aircraft touches the ground, the wheel meets great resistance to forward motion. As the undercarriage absorbs almost none of this longitudinal impact, the tire begins to smoke, while the oleo strut undergoes spin up and spring back. Most people are unaware that this phenomenon represents the technological limits of current suspensions. For the wheel to absorb forward impact, it must be given longitudinal stroke. We have created a new type of undercarriage, containing a crank element and adequately gives the longitudinal stroke (1),(2). We clarified the new undercarriage with basic dynamical analysis and computer simulations using an aircraft model with 1 degree of freedom. This simulation showed that when given specific freedom of circular motion, the wheel will accelerate in two stages after landing. Consequently, the sliding friction work on the tire is reduced by a maximum of about 47.4%.

The author proposes a new principle of suspension system. First, a new shock isolation method prevents sudden sharp jolts and enables a body to continue in motion as before, by transforming linear motion into circular motion. This method reduces abrupt deceleration and impact force. Next, we examined the gravity spring action of a pendulum as a new vibration isolation method. Because the pendulum generates longitudinal vibration, it has isolation effect against the longitudinal vibration input. Application of this new principle to aircrafts, automobiles, motorcycles, and even to bicycles and wheelchairs, overcomes the limitations of current technology. This study focused on two as-yet-unresolved safety problems of aircraft undercarriages. One is acceleration impact on the wheels; the other is collision with an obstacle on the runway.

When an aircraft wheel touches the stationary runway at high speed, great force from the forward direction suddenly pushes on the tires and landing gear. The widely used vertical shock absorber, known as an oleo strut, is unable to buffer this forward shock. This results in smoking and severe wear of aircraft tires on landing. Therefore, in contrast to automobiles, expensive aircraft tires need to be replaced frequently, adding considerably to maintenance and transportation costs. We first presented new technology for solving this problem during the international conference 2001WAC, and in further detail in 2003WAC. We proposed a new type of landing gear that uses a crank element to absorb horizontal shock from the forward direction. The next focus of attention was the problem of increased weight, resulting from introduction of the crank element. Computer simulations using a basic model of the landing gear showed a 62.1% decrease in the maximum bending moment.