Operation Grapple 'Y'

Report on the Bombing Phase at Christmas Island
by

Officer Commanding No.49 Squadron

Introduction

1.     This operation consisted of dropping a thermo nuclear weapon of the megaton range from a true altitude of 46,000 feet on to a selected target off the S.E. promotary of Christmas Island in the South Pacific.

2.     The weapon was required to be aimed at the visual target by means of the T.4. bombsight, and the moment of release being automatically delayed to allow the weapon to overshoot the visual target by 1½ statute miles. The weapon itself being fused to explode some 53^.5 seconds after release at an approximate altitude of 8,500 feet.

3.     In the event of cloud cover making a visual drop impractical, the weapon was to be dropped by information supplied by the Mk.7 Gun laying radar equipped with an E.M.I. plotting table. The information being fed through to the I.L.S. tracking indicator in the aircraft, and time of release given verbally by H.F. control.

4.     In support of this operation, the squadron was also required to fly to Christmas Island special radio active material by means of a Valiant operating as a fast courier slipping crews at Goose Bay, Travis and Honolulu. To ensure the success of this phase of the operation, reserve Valiant aircraft were previously positioned at Goose Bay and Travis.