The aircraft, wheels and brakes department at British Airways plc (Middlesex, United Kingdom) is responsible for the repair and overhaul of aircraft brake units on the Boeing 737, 747, 757, 777 and Airbus A319, A320 and A321 aircraft.
The brake springs are a critical part of the brake unit because they apply the correct amount of pressure to stop the aircraft. “The brake springs must be tested on every one of each planes’ overhauls,” says Lionel Fearon, product support engineer at British Airways. Overhauls involve the plane being stripped down, which usually takes place after every 3,000 landings.
The brake springs are subjected to a compression test to ensure the pistons extend and retract and that these safety-critical components perform correctly. Tests were previously performed on a manual test system; however, the engineers at British Airways found they required a more sophisticated motorized test system to produce more accurate results and reduce the time taken to carry out the test.
When using the manual test system, the operator had to wind a handle to compress the spring while looking for a digital reading. The operator then had to correlate this against another reading before manually calculating whether the spring was within specification. Because it was difficult to keep the compression speed constant this did not give accurate results and also was very time consuming.
Improving the ProcessTo help British Airways obtain more accurate test results, combined with a more efficient testing process, Mecmesin (Sterling, VA) supplied a MultiTest 5-x console-controlled force testing system, fitted with a 5-kilonewton loadcell. The MultiTest 5-x expedites the testing process by compressing springs in less than 30 seconds, through the touch of a button.
It is able to give more accurate and consistent results than a manual tester because the speed of the test can be preset, giving a greater degree of repeatability during the measurement process. After the spring has been compressed, the system displays a pass or fail icon on the screen to show whether or not it has met the required specification. If the spring has failed, the tester indicates the parameter it failed against. The screen also displays additional characteristics such as length and rate.
Mecmesin also set up the MultiTest 5-x so every individual spring has its own test routine, required in the component maintenance manual. The system is programmed to compress about 24 different types of brake spring, each with its own characteristics. Each program is identified by the type of aircraft and its spring. For example, an operator can set up the MultiTest 5-x to test the spring of a Boeing 777, select the program for that aircraft and automatically test the spring to the aircraft’s specification.
These stored, automated test routines, combined with the one-button ease of use and automatic display of pass/fail messages, have reduced test times by 75%, providing significant cost savings and increasing efficiency.
“Use of the MultiTest 5-x has simplified and accelerated the testing of the aircraft brake unit springs,” says Fearon. “Having input the parameters per the component maintenance manual into the unit, we are able to test a spring at the touch of a button and have a near instantaneous result without ambiguity.”