CASA has issued warnings of potential problems surrounding the usage of transponders and the maintenance of autopilots.
The regulator says that a number of older transponders fitted to aircraft are causing false short-term conflict alerts to appear on air traffic control consoles, with new terminal area radar equipment at Coolangatta and Melbourne airports detecting anomalies with the mode A code they transmit.
With new radar equipment being installed at other major airports including Brisbane, Sydney and Perth through this year, CASA says the problem of false conflict alerts must be addressed.
“The new radar equipment is detecting uncommanded and random changing of the mode A code, caused by variations in the pulse shape and the relative amplitudes of the data pulses,” CASA explains. “Problems are mainly being found with transponders that use electron tube technology, such as the Bendix/King KT76A, Narco AT150 and ARC RT859.
“This problem is being addressed through changes to an airworthiness directive that requires additional maintenance to transponder systems and up-to-date advice on how to perform additional tests on transponders. Aircraft owners and operators who are notified of an anomaly caused by their transponder are advised to get the equipment serviced as soon as possible.”
The airworthiness directive covering this issue, originally published by CASA in December 2010, sets out the tests required to be performed on all transponders and the timeframes that must be met.
To read the airworthiness directive on transponder tests click here.
To find out how to perform the tests click here.
CASA has also reminded aircraft owners, operators and maintainers to make sure safety features on autopilots are maintained properly and continue to operate as required.
Safety features built into autopilot systems, such as the option to disengage the autopilot quickly and positively so it doesn’t interfere with control of the aircraft, can be rendered defective if the required overpower forces don’t remain within specified tolerances, causing the safety mechanisms to fail to operate.
“Regular inspections should be made of autopilots to ensure that each part of a servo is capable of performing its intended function,” CASA advises. “Inspections should include looking at the condition of lubrication where applicable, as a lack of attention to lubrication seems to be the cause of many defects in automatic pilot servos.
“Care should also be taken when replacing autopilot servos as many appear similar yet operate very differently.”
Click here to read CASA’s advice on autopilot maintenance.