# AD 81-09-09: Combustion Heaters - Type: Airworthiness directive - Status: Historical - Products: Stewart-Warner Combustion Heaters - Effective: May 8, 1981 - Superseded by: [AD 2017-06-03](https://openairdocs.org/ad/2017-06-03) - Product type: Appliance - Amendment: 39-4102 - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/48D1D38B25AEAFEA86256A390068429C.0001 - DRS record last changed: August 7, 2025 - Page: https://openairdocs.org/ad/81-09-09 ## The airworthiness directive 81-09-09 STEWART-WARNER (SOUTH WIND DIVISION): Amendment 39-4102. Applies to Model Series 8240, 8253, 8259, and 8472 marked as meeting the standards of FAA TSO-C20, installed in aircraft certificated in all categories. Compliance required as indicated. To prevent a hazardous condition caused by deterioration of the combustion heater, accomplish the following: A. For combustion heaters having 250 hours or more time in service after the effective date of this AD, conduct the 250 hour inspection in accordance with the manufacturer's service manual (see Note 2) within the next 50 hours of combustion heater operation, unless already accomplished within the last 200 hours of heater time, and thereafter at intervals not to exceed 250 hours of combustion heater operation. Also, along with the above inspection, a general inspection of the combustion heater installation must also be accomplished including at least the following: 1. Inspect ventilating air and combustion airinlets and exhaust outlet correcting restrictions and insuring attachment security. 2. Inspect drain line and insure it is free of obstruction. 3. Check all fuel lines for security at joints and shrouds, correcting those showing evidence of looseness or leakage. 4. Check all electrical wiring for security at attachment points, correcting conditions leading to arcing, chafing or looseness. B. For combustion heaters having 1000 hours or more time in service after the effective date of this AD, overhaul the combustion heater in accordance with the manufacturer's service manual (See Note 2) within the next 50 hours of combustion heater operation, unless already accomplished within the last 950 hours of heater time, and thereafter at intervals not to exceed 1000 hours of combustion heater operation. An overhaul consists of complete disassembly, cleaning, repair, reassembly and test as outlined in the appropriate service manual. Note 1 - In complying with this AD, if the owner or operator cannot document combustion heater operative time, the aircraft time must be used. Note 2 - The following is a list of combustion heaters covered by this AD and the appropriate service manual. Methods of inspection or overhaul other than those contained in the manufacturer's service manuals must be approved by the Chief, Engineering and Manufacturing Branch, FAA Great Lakes Region. Models Service Manual Number 8240 Series 09-998 or P.M. 35710 8259 Series (Appropriate usage is shown in Manual or Manual Supplements) 8253 Series P.M. 20688 8472 Series 09-1015 This amendment becomes effective May 8, 1981. ## Registered aircraft it may apply to (OpenAirDocs) No registered aircraft matched the models it names. ## Related documents - [AD 2017-06-03](https://openairdocs.org/ad/2017-06-03): Heating System · Meggitt 921, 930, 937, 940, 944, 945, 977, 978, 979, 8240, 8253, 8259, and 8472. Effective May 5, 2017. Supersedes this AD Its text cites no advisory circulars or STCs. ## NTSB investigations that cite this AD (2) From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. - [NTSB CEN12FA290](https://openairdocs.org/ntsb/CEN12FA290), May 11, 2012: Cessna 401 (N9DM), Chanute, KS, substantial damage, 4 fatal. Probable cause: The malfunction of the cabin heater, which resulted in an inflight fire and smoke in the airplane. Contributing to the accident was the pilot’s lack of understanding concerning the status of the… - [NTSB IAD02LA020](https://openairdocs.org/ntsb/IAD02LA020), Dec 17, 2001: Cessna 401A (N4062Q), Martinsburg, WV, substantial damage. Probable cause: the owner/mechanic's failure to comply with an Airworthiness Directive, which resulted in a cracked fuel supply line and subsequent in-flight fire. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.