Expert: Ray Wilkinson - 12/11/2006

Question
weight of armament carrying capability of vertical take  off aircraft such as a harrier vertical lift aircraft

Answer
Hi Edward

The Harrier's engine produces 21750 lbs of thrust (9860kg), and it has a dry weight of 5940kg, leaving 3920kg of available thrust to lift fuel and weapons load. However, its rated take-off weight for VTO is only 8600kg, to allow some extra for accelerating vertically, and some safety margin, which leaves only 2660kg for fuel and weapons. Allowing for, say a tonne of fuel for any reasonable sortie, that gives a typical maximum weapons load of about 1660kg.

In a rolling take-off, the engine does not have to produce enough thrust to lift the entire weight of the aircraft, and this increases the maximum take-off weight to 14060kg. Allowing for the same fuel load, this increases the maximum weapons load to 8120kg. To get the aircraft off the ground in as short a distance as possible, especially to allow operation off the deck of small aircraft carriers, the Navy devloped a method of using a ramp known as a ski-jump. This gives some of the benefits of VTO with the same take-off weight as for a rolling take-off.

Another issue is that of vertical landing, which is necessary for carrier operations. The Harrier can land with the same weapons load as for VTO, but it must be reasonably symmetrical. I was involved in weapons trials of Sea Eagle missile on Sea Harrier in the early 1980s. Sea Eagle is a heavy missile, and the Sea Harrier can carry two on under-wing stations. However, if one is fired the other must be either fired or jettisoned before the aircraft can land, as the weight asymmetry is too much.

I hope this answers your question.

Regards

Ray