Bomber Command Operational Research Branch on Memo 281 dated Nov 1963, stated that the Yellow Sun and Blue Steel could be released in level flight after a popup manoeuvre at 300kts EAS. The Yellow Sun could also be released at flight path angles of 10 to 20 degrees above the horizontal. In level flight the minimum release altitude was 11,000 ft. For the Yellow Sun it was 9,500 ft in a 10 degree climb and 8,400 ft in a 20 degree climb.
The level release at 11,000 ft was called a 2E and the release in the climb was called a 2H. The time of bomb fall for the Blue Steel was considerably less but the forward throw was considerably more than the YS2. The release in the climb case was not considered as they did not think they would get clearance.