Kidde's APDs are being offered to satisfy customers who prefer the pneumatic operating principle and/or are having problems with the design of existing pneumatic detectors in service.
The APD was initially developed by Aerosafe International (Richmond, California) by an engineering staff that had acquired a wealth of experience in pneumatic fire and overheat detection. The objective was to use their 100+ years of cumulative knowledge of metal hydrides and materials engineering experience to overcome the shortcomings of existing pneumatic detection technology. The APD is the successful result of that effort.
In 1995, Kidde purchased the pneumatic detector product line from Aerosafe, and thus acquired the APD technology, manufacturing equipment and key personnel. APDs are now being produced at our Wilson, North Carolina facility.
Many aircraft manufacturers and operators who use pneumatic detection are changing to the Kidde APD in order to eliminate nuisance false alarms caused by exposure to the rigors of the aircraft engine environment. Still others are switching because, although they may not actually experience false alarms, the replacement rate for the older type of pneumatic detector is higher than desired (the failure mode is a dramatic change in pressure switch alarm set point, resulting in inability to meet original calibration requirements).
The APD was designed to eliminate the problems described above. After exhaustive laboratory testing to environments far in excess of those required by Federal Aviation Administration (FAA) TSO C11e, and subsequent good in service experience, the APD has become the standard by which pneumatic detectors are judged. All APDs are fully qualified to MIL F 7872C and meet FAA TSO C11e approval requirements.