Emergency landing dynamic conditions: a comparison with accident impact conditions

Abstract

Emergency landing dynamic conditions for small airplanes include two tests to demonstrate that seat/restraint systems of small airplanes provide protection against occupant injuries to the head, chest and spine during the principal impact of a crash sequence. The dynamic conditions for these two tests were derived from accident data for small helicopters and test data for small airplanes; accident data for small airplanes were not available before the derivation of these dynamic conditions but were available shortly after. The purpose of this study is to compare the emergency landing dynamic conditions with the helicopter accident data and airplane test data accessible before the derivation of these dynamic conditions and with the airplane accident data accessible after. The conclusion resulting from this study is that supplementary accident data for small airplanes need to be collected and the correlation of prescribed emergency landing dynamic conditions with observed accident impact conditions needs to be evaluated.

Keywords:

• small aircraft
• aircraft accident reconstruction
• emergency landing conditions
• helicopter accident data
• airplane test data
• airplane accident data

Acknowledgements

The author thanks Dr Michael S. Boldrick of Boldrick Systems for reviewing the paper and preparing it for publication.

Notes

All reported values of rotation, acceleration, velocity and velocity change are numerical values. All reported values of acceleration are peak values.

Additional, correlative accident and test data are discussed in the Technical Data Review section of [17].

The number of initial conditions under the design curve was obtained in the present study by summing the initial conditions shown under the survivability envelope of [2].

The majority of accident helicopters were nearly – but not completely – level at impact.

The forward and vertical components of velocity change along the test airplanes were calculated in the present study using the peak values and time durations of the forward and vertical components of acceleration along the airplanes summarised in Table I of [1].

The biaxial comparison of the present study is a more rigorous description of the relation between crash landing conditions and airplane accident conditions than the uniaxial comparisons of [14]. The correlation ascribed between crash landing conditions and airplane accident conditions is, as a result, smaller in the present study than in [14].