Date of Award
Master of Science
W. Lewis, R. B. Richards
This study investigates a modification to the T-45 Goshawk that releases brake pressure when the aircraft is on the catapult of an aircraft carrier, preventing the pilot's inadvertent brake application in the cockpit from applying the brakes at the wheel. The modification arose from numerous incidents of Student Naval Aviators inadvertently actuating the brakes during catapult shots, ultimately causing the tire(s) to explode. The subsequent landings with blown tires have proven extremely hazardous resulting in at least three catastrophic mishaps in four years of operational training. The modification takes a radical departure from conventional naval aviation wisdom concerning the pilot's control of brakes, because it inhibits hydraulic pressure from actuating the brakes. This system effectively removes the pilot's pedal input to the brake system during a catapult launch, when brake application is undesirable.
The problem of inadvertent braking on the catapult results mainly from cockpit ergonomics in the T-45. Specifically, the fulcrum of the brake pedal sits too close to the floor beneath, preventing the pilot from executing normal catapult procedures conducted in the fleet, where he slides his feet to the deck for the catapult launch. The alternative solutions included a "Toe-bar" and minor adjustments to the brake pedal height and deck plate location within the limits of the aircraft's major structure. The "Toe-bar" was a reference point at the mid-point of the brake pedal, under which the pilot placed the toe of his boot. It effectively placed the pilot in a position that prevented him from applying sufficient moment to actuate the brakes. The "Toe-bar" was implemented in fleet T-45 aircraft, and produced moderate success at preventing blown tires on the catapult. It has ergonomic issues of its own however, since it places the pilot in an extremely uncomfortable position that is potentially hazardous in an ejection scenario. The other modifications were found unsuitable, particularly for larger pilots during early cockpit mock-up testing.
This study provides an analysis of the causes of blown tires on the catapult, the human factors involved with alternative ergonomic solutions, the method of testing the brake release solution, and a psychological discussion of the transfer of training concerns regarding students transitioning to fleet aircraft after flying the T-45 with brake release incorporated.
The author concluded that the brake release system will successfully prevent pilot brake application from resulting in blown tires on the catapult, but discovered one correctable ground handling deficiency with the prototype system as it was installed in the T-45.
The author made three recommendations:
• The Navy should incorporate the brake release system in the T-45 after correcting the ground handling deficiency.
• The Navy should incorporate the brake release system in future fleet aircraft
• The Navy should research whether the blown tire problem exists in fleet aircraft, and pending the results modify existing fleet aircraft with the brake release system.
Parker, Donald J., "An investigation into brake release on the catapult : a non-ergonomic solution to an ergonomic problem in the T-45 Goshawk. " Master's Thesis, University of Tennessee, 2000.