 Starting in the summer of 1942 the TRE development team began experimenting with systems to project the display onto the windscreen , and by October had combined this with an image of the existing <unk> Mk . II gyro gunsight to produce a true head @-@ up display known as the Automatic Pilot 's Indicator , or API . A single example was fitted to a Beaufighter and tested through October , and numerous modifications and follow @-@ on examples were trialled over the next year . 
