Tornado reversionary loft was a "manual" aiming technique, i.e. no computing involved, and was really only intended to ensure that a WE177 landed on the correct side of the FLOT. It went something along the lines of:
Pilot:
Fly precisely at pre-nominated speed and height.
Nav:
Set up a marker ring ("cursor" in the terminology) on the radar display at a pre-calculated distance ahead of the aircraft
Identify the target using the radar
Tell pilot to steer left or right until tracking directly towards target
Give a countdown such that the pilot begins pulling up as the target crosses the cursor (3-2-1-Pull)
Pilot:
Pull up at precisely 3g
As pre-nominated climb angle is reached, press the weapon release button whilst continuing 3g pull
Recover
Both:
Wince as score in excess of 1000 feet duly reported.
The opposite of Rev Loft was Auto Loft, where the target position was input into the aircraft computer and automatic weapon aiming calculations determined the point at which the weapon was released. The target position could be updated using the radar during the attack. A countdown to pull-up and azimuth steering commands were shown in the HUD, which the pilot could follow manually or let the autopilot do the business (e.g. during terrain following radar ops). Just before pull-up the autopilot would be disconnected, the pilot would follow the HUD flight director pull-up command manually, and the weapon release button would be held down. The computer would continually recalculate the bomb throw as the flightpath angle increased and the airspeed decreased, and when this met the range to target the weapons would be released automatically. At a guess, about 10% ended in DHs and good crews were able to score consistently within 100ft. The prime sources of error were probably the accuracy of the target mark on the radar, the accuracy of the aircraft's height in the bomb aiming solution, and crosswinds (because there was no lateral compensation for crosswind in the aiming solution; this meant that aircraft tracked directly towards the target at release, so as the bombs slowed down they drifted slightly downwind).