Weapon Bay Door Actuator

The weapon bay door actuators are driven by a motor and provide a very high (approximately 15:1) gear ratio in a very tight and compact unit. The actuators comprise of a number of earth and output lugs in series. A central sun shaft is driven by a motor. The sun is surrounded by and meshes with a number of planet gears that also mesh with the lug outer ring gears.

GTO were asked to optimise the design of the actuator lugs when subjected to Ultimate and Proof loads derived from a combination of high "g" manoeuvres and wind loading on the open doors.


The acceptance criteria were:

That the lugs should not fail under Ultimate loading. Local yielding is allowed, however plastic strains should not exceed 1.5% for that particular material. Permanent deformation should be less than 30 microns to avoid malfunction of the gears.

That there should be no noticeable yielding of the material under Proof loading.
GTO developed a solid system model of the actuators with non-linear spring and gaps to represent the internal gears. The lugs were optimised for minimum mass using HyperWorks. This was followed by an ABAQUS full non-linear analysis including plasticity and contact to predict stresses and plastic strains under ultimate loads.

GTO successfully optimised and verified the design of the actuator lugs.