# AD 90-06-03 R1: Exhaust Heater/Muffler Assembly - Type: Airworthiness directive - Status: Current - Products: Cessna 172, 172A, 172B, 172C, 172D, 172E, 172F (USAF T-41A), 172G, 172H (USAF T-41A), 172I, 172K, 172L and 7 more - Effective: March 27, 1991 - Superseded by: Nothing supersedes this AD - Product type: Aircraft, Small airplane - Amendment: 39-6927 - Docket: 90-CE-10-AD - Registered aircraft: 20,676 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/C75D48AE26F0BD0C86256A340062036D.0001 - DRS record last changed: May 30, 2024 - Page: https://openairdocs.org/ad/90-06-03-R1 ## The airworthiness directive 90-06-03 R1 CESSNA: Amendment 39-6528 as revised by Amendment 39-6927, Docket No. 90-CE-10-AD. Applicability: Model 172 airplanes (serial numbers 36216 through 36769) that have not been modified with Cessna Service Kit SK-172-10 or SK-172-10A, certificated in any category. Compliance: Required within the next 25 hours time-in-service after the effective date of this AD, unless already accomplished. To prevent cracking of the exhaust heater/muffler that could result in dangerous carbon monoxide levels, accomplish the following: (a) Inspect the exhaust heater/muffler assembly for cracks in accordance with the procedures as outlined in the applicable Cessna Service Manuals, or the following: (1) Remove and disassemble the exhaust heater/muffler assembly by removing the shroud assembly. (2) Visually inspect the exhaust heater/muffler, Cessna Part Number 0550157-32, for cracks, or submerge the muffler in water and pressure test at 5 pounds p.s.i.NOTE 1: Particular attention should be given to the cylindrical surface that contains the heat transfer pins. (3) If cracks, breaks, or any leakage is found in the exhaust heater/muffler area, prior to further flight, replace the exhaust heater/muffler with an airworthy part. (b) Modify the airplane by the installation of Cessna Service Kit SK-172-10A. NOTE 2: Cessna Service Letter (SL) 170/172-11, dated February 3, 1958, and Cessna SL 170/172-13, dated April 7, 1958, contain information that pertains to the subject of this AD. (c) Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a location where the requirements of this AD can be accomplished provided that the cabin air control remains in the "OFF" position. (d) An alternate method of compliance or adjustment of the compliance time that provides an equivalent level of safety may be approved by the Manager, Wichita Aircraft Certification Office, Mid-Continent Airport, 1801 Airport Road, Room 100, Wichita, Kansas 67209. The request should be forwarded through an appropriate FAA Maintenance Inspector, who may add comments and then send it to the Manager, Wichita Aircraft Certification Office. (e) All persons affected by this directive may obtain copies of the documents referred to herein upon request to the Cessna Aircraft Corporation, P.O. Box 7704, Wichita, Kansas 67277; or may examine the service letters at the FAA, Central Region, Office of the Assistant Chief Counsel, Room 1558, 601 E. 12th Street, Kansas City, Missouri 64106. Airworthiness Directive 90-06-03 R1 revises AD 90-06-03, Amendment 39-6528. {{Amendment 39-6528 supersedes AD 58-08-02.}} This amendment (39-6927, AD 90-06-03 R1) becomes effective on March 27, 1991. ## Affected data sheets (2) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS 3A12](https://openairdocs.org/tcds/3A12): Textron Aviation Inc.; names 18 of 18 models: 172F (USAF T-41A), 172M, 172Q, 172R, 172K, 172G, 172A, 172L… - [TCDS 3A17](https://openairdocs.org/tcds/3A17): Textron Aviation Inc.; names 1 of 12 models: 172RG ## Registered aircraft it may apply to (OpenAirDocs) Matched by airframe and engine model; the AD's applicability may narrow it by serial number, part number or equipment. - Aircraft: 20,676 (20,676 by airframe model, 0 by engine model) - Makers: Cessna 19,438, Textron 1,238 Models with the most aircraft: - [Cessna 172M](https://openairdocs.org/model/cessna-172m): 3,574 aircraft (airframe model) - [Cessna 172N](https://openairdocs.org/model/cessna-172n): 3,138 aircraft (airframe model) - [Cessna 172S](https://openairdocs.org/model/cessna-172s): 1,915 aircraft (airframe model) - [Cessna 172](https://openairdocs.org/model/cessna-172): 1,805 aircraft (airframe model) - [Textron 172S](https://openairdocs.org/model/textron-172s): 1,238 aircraft (airframe model) - [Cessna 172P](https://openairdocs.org/model/cessna-172p): 1,111 aircraft (airframe model) - [Cessna 172K](https://openairdocs.org/model/cessna-172k): 1,026 aircraft (airframe model) - [Cessna 172L](https://openairdocs.org/model/cessna-172l): 858 aircraft (airframe model) - [Cessna 172H](https://openairdocs.org/model/cessna-172h): 780 aircraft (airframe model) - [Cessna 172G](https://openairdocs.org/model/cessna-172g): 722 aircraft (airframe model) - [Cessna 172F](https://openairdocs.org/model/cessna-172f): 717 aircraft (airframe model) - [Cessna 172R](https://openairdocs.org/model/cessna-172r): 683 aircraft (airframe model) - [Cessna 172E](https://openairdocs.org/model/cessna-172e): 617 aircraft (airframe model) - [Cessna 172D](https://openairdocs.org/model/cessna-172d): 471 aircraft (airframe model) - [Cessna 172RG](https://openairdocs.org/model/cessna-172rg): 445 aircraft (airframe model) - [Cessna 172A](https://openairdocs.org/model/cessna-172a): 435 aircraft (airframe model) - [Cessna 172B](https://openairdocs.org/model/cessna-172b): 413 aircraft (airframe model) - [Cessna 172C](https://openairdocs.org/model/cessna-172c): 362 aircraft (airframe model) - [Cessna 172I](https://openairdocs.org/model/cessna-172i): 353 aircraft (airframe model) - [Cessna 172Q](https://openairdocs.org/model/cessna-172q): 13 aircraft (airframe model) All 21 models: https://openairdocs.org/ad/90-06-03-R1/models.md Every aircraft: https://openairdocs.org/ad/90-06-03-R1/aircraft.md Its text cites no advisory circulars or STCs. --- 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.