Airworthiness Directives; Kelly Aerospace Power Systems B-Series Combustion Heaters Models B1500, B2030, B2500, B3040, B3500, B4050, and B4500 (Formerly Owned by JanAero Devices, Janitrol, C&D, FL Aerospace, and Midland-Ross Corporation)

The FAA is superseding Airworthiness Directive (AD) 96-20-07, which applies to certain B-Series Combustion Heaters Models B1500, B2030, B3040, and B4050 that are installed on airplanes. AD 96-20-07 currently requires you to repetitively test (pressure decay) the combustion tube and overhaul any heater that does not pass any test. AD 96-20-07 also requires you to repetitively test the operation of the combustion air pressure switch and replace any combustion pressure switch that does not pass one of the tests. As a terminating action for the repetitive test requirements of AD 96-20-07, you could install a new ceramic-coated combustion tube and an improved design combustion air pressure switch. This AD is the result of reports that the new ceramic-coated combustion tubes are subject to the same distress as the non-ceramic coated combustion tubes. Consequently, this AD retains the repetitive testing requirements of AD 96-20-07, removes the terminating action for the combustion tube, and adds Models B2500, B3500, and B4500 to the applicability section. We are issuing this AD to prevent combustion by-products (carbon-monoxide exhaust) and fuel leakage from the combustion heaters caused by failure of the combustion heater system. This failure could result in fire or explosion in the airplane and possible carbon monoxide poisoning of the crew and passengers in the cabin.