AOPA has submitted formal comments to the FAA on a proposed airworthiness directive to update the inspection requirements for Meggitt (Troy) Inc. combustion heaters installed primarily in Cessna and Piper aircraft.
AOPA supported and endorsed the position of the Twin Cessna Flyer organization on the proposal and suggested modifications to make the AD more effective, including extending a requirement to inspect the heaters after two calendar months to 12-calendar months.
On Aug. 20, the FAA published a notice of proposed rulemaking to modify requirements of a 1981 AD to add inspections based on the calendar to its provisions—calling for the combustion heater inspections to be carried out within the next 10 hours in service, or two months, whichever occurs first.
Other proposed requirements include a pressure decay test, component inspections, and a prohibition on repairing the combustion tube.
The FAA said it was revisiting the original AD as the result of a fatal aircraft accident, "and reports we received that the heater was malfunctioning," said the NPRM.
AOPA, supporting comments from the Twin Cessna Flyer organization, agreed that the imposition of an inspection based on the calendar is "consistent" with how the FAA has handled heater concerns in other instances.
"However, the initial two month or 10 hours of operation inspection threshold is too short," wrote Tom Kramer, AOPA manager of regulatory affairs. "AOPA recommends the FAA extend the inspection threshold period to 12 months or 10 hours."
AOPA added that the detailed inspection requirements outlined in the AD "appear to be appropriate," and would "greatly enhance" inspections.
AOPA sought clarification from the FAA on language requiring a complete overhaul following the failure of a pressure decay test. "A situation may arise in which component parts had been replaced very recently, prior to the PDT failure. As written, the failure would prompt a complete overhaul of the entire heater, including those component parts recently installed. A more conservative approach would be to require replacement of the combustion tube, resulting in an equivalent level of safety," Kramer wrote.
AOPA agreed with the Twin Cessna Flyer organization that the FAA had underestimated the number of affected airframes under the proposed AD.
The FAA has estimated costs of individual inspections at $425, with additional costs of up to $6,000 to overhaul a defective heater and related parts, or $255 to remove the heater.
The heaters were previously sold under the Stewart Warner South Wind Corp., and Stewart Warner South Wind Division brands.