Backstop device, and method for testing the operational integrity of a backstop device.

摘要

This invention provides an improvement in a no-back device having a ball screw connected to a variable load of reversible polarity (±L) and having a portion penetrating a housing. The device includes a braking mechanism acting between the housing and the ball screw for producing a force that resists movement of the ball screw in the direction of an "aiding" load, but does not substantially resist movement of the ball screw in the direction of an "opposing" load. The improvement broadly includes: a first spring acting between the housing and the braking mechanism for exerting a first preload force (F1) on the braking mechanism for simulating the application of an external load on the ball screw in one of the directions; whereby the apparent operational integrity of the no-back device may be checked when no external load is applied to the ball screw. In use, the apparatus performs the steps of: providing a first spring; causing the first spring to exert a first preload force (F1) on the braking mechanism; determining the actual torque (Ta) required to move the ball screw while the aircraft is on the ground; comparing the actual torque with a theoretical torque (Tt) required to move the ball screw; and inferring that the no-back device is not operating correctly if the actual torque is less than the theoretical torque; thereby to test the apparent operational integrity of the no-back device when the aircraft is on the ground.