TOWPLANE HOOK DESIGN AND OPERATIONAL TESTS

Abstract

As a result of tow pilots observations that the release mechanism could not be operated under load, a study was made of the characteristics of these mechanisms. With the operational system tested, the tow pilot would not be able to release his hook at towline tensions exceeding 225 lb. A reasonable maximun release load at the cockpit is 35 lb with a towline tension of 900 lb at an angle of 30 degrees from the horizontal. The basic hook with no allowance for the mechanism between the hook and the cockpit exceeds reasonable release load limits for towline tensions exceeding 435 lb. The release load at the hook can be reduced by: (a) increasing the mechanical advantage, (b) reducing friction, (c) reducing the hook stability. By the proper combination of relieving the hook release load and reducing the friction between the hook and the cockpit the hook can be made to release with reasonable force.