Acceleration responsive monitor

Apparatus for monitoring the acceleration of an aircraft moving on the ground, which includes a linear accelerometer rigidly secured to the aircraft with its sensitive axis along a fore-and-aft axis of the aircraft and, nominally horizontal, first circuit means operable to null the output of the accelerometer while the aircraft is at rest and including a first amplifier responsive to the output of the accelerometer to develop a first current and a second amplifier operable when the aircraft is at rest to develop a second current equal and opposite to the first current, a gyroscope operable to determine the attitude of the sensitive axis of the accelerometer relative to a horizontal plane, second circuit means responsive to the output of the gyroscope and operable to correct said output for pitch movements of the aircraft while the aircraft is moving on the ground, summation means operable to combine the first and second currents and the output of the second circuit means, correction means operable to reduce the output of the summation means by an amount dependent upon the aerodynamic drag resistance of the aircraft at any instant, and indication means operable to provide an indication of the corrected output of the summation means.