Emergency Arrestor Hook
Between the engines of the Tornado and running along the underside of the airframe to a point where the under fuselage pylons sit is an emergency arrestor hook. Thanks to Bob Owbridge who served in the RAF as s a Ground Equipment Tech we have a description of the procedure. The photographs in the article show the portable used on the 1/2 length runway at Duxford to catch the F-111 which is now on display.
"I was in the RAF as a Ground Equipment Tech for a number of years, during that time I was stationed at RAF Leeming with 11, 23 and 25 Sqn's operating the Tornado F3, during that time I was on the Airfield Arrestor team and used the following equipment to slow or stop aircraft in trouble due to things like hydraulic failure."
"The main way to stop an aircraft was by the RHAG's (Rotary Hydraulic Arrestor Gear) which consisted of a cable running across the runway held off the ground by flat rubber grommets reinforced with a steel wire, this was attached to a 'tape' made of a thick woven canvas, the tape could be raised from the control tower by an End Sheave, the other end of the tape was wound round a drum by an electric motor and held under tension be a break away lever, one each side of the runway, the drum was in turn directly attached to a rotor fitted with several veins which acted against a set of stators and surrounded by antifreeze/water solution in a tank. When the Aircraft took the cable the break levers let go and the tape payed out, using the stater and rotor in the tank to slow the Aircraft safely. If the aircraft was able to reach the end of the tapes it would be moving so slowly the drums would simply full stop the Aircraft with a jolt. In all my engagements I only ever witnessed this once."
Alternately we had a set of PRHAG's Portable Rotary Arrestor Gears's. These were large trolleys which could be dropped off either side of a temporary runway, lowered to the ground and staked out using many 6' Alluminium stakes hammered into the ground, this system was different from the RHAG's in that it used a set of vertically mounted drums braked by a set of B52 breaks, the tape and cable were the same but although available end sheaves were seldom used. The main benefit of this system is it always payed out the same amount of tape, the harder and faster the Aircraft hit it the more breaking force was applied.
In Gibraltar only a CHAG Chain Arrestor Gear was used, I never witnessed this equipment but it was made up of a cable and grommets attached to a large chain laid out either side of the runway, as the chain payed out the increasing weight slowed the Aircraft,
Finally a Barrier was fitted at each end of the runway which ATC could raise if the Aircraft was authorized to use it, two stanchions with a wire stretched between them (higher than the cockpit of the Aircraft held up a net tied with nylon string of various breaking strains, the Aircraft shot under the wire and the net enveloped the whole thing, the net was attached to wires that lead to four brake units, these stopped the aircraft with minimal damage.