This invention relates to a hard landing indication system that will provide a quantitative assessment that a hard landing did or did not occur at the last landing of an airplane. A hard landing can cause structural damage to an airplane. An airplane that has been declared to have a hard landing must be grounded until an inspection of the structure has been made to determine if repairs are required.

A process and device for detecting on an aircraft an overshoot of design loads at the level of a structural part of the aircraft. The detection device includes a speed measuring device for measuring an effective speed of the aircraft. A first comparator compares the measured effective speed with a maximum speed relating to the current flight configuration of the aircraft. A vertical load measuring device measures a vertical load factor of the aircraft, and a second comparator compares the measured vertical load factor with a limit value of the vertical load factor. An inspection determining device determines whether a structural inspection needs to be performed at the level of the structural part, based of the results of the first and second comparisons.

Methods and apparatus to design a wheel of a multiple-axle vehicle are disclosed. A disclosed method analyzes fatigue damage values of wheels, each to be installed at a number of axle positions on a vehicle, and includes determining for each wheel a fatigue damage value for each of a plurality of critical locations at the wheel during an installation and determining whether at least a subset of total fatigue damage values at critical locations for each wheel installation exceeds a respective threshold total fatigue damage value.

The present invention is embodied in an apparatus and method for generating fatigue spectra on a chosen aircraft for which a Finite element model is available and for which a library of external load summations at key interfaces and key fundamental parameters are available from an aeroelastic analysis. The fatigue spectra generation system of the present invention represents a profile of stresses endured by the aircraft due to numerous events, such as ground and maneuver events, occurring during the life of the aircraft. The system calculates a total stress based on load and unit conditions associated with outside events by factoring up the unit conditions to derive individual stresses for each event and by summing all unit conditions.

The system and method of this invention determines stress within the load bearing members of an aircraft, machine or structure in order to improve their design, safety and efficiency as well as enhancing their operation. Load or stress is calculated from signals generated in fasteners fitted with piezoelectric crystals. Rather than indirect stress indication through approximations from accelerometers, optical fibers, position sensors, strain gages and the like, this invention calculates load or stress from sensors installed directly into load bearing elements. This invention can perform stress indicating function in machines and structures such as, but not limited to, aircrafts, buildings, bridges, power generating stations, ships and engines.