# AD 78-20-12: Aircraft Tires - Type: Airworthiness directive - Status: Current - Products: Cessna 336, 337, T337B, T337C, T337D, T337E, T337F, T337G, T337H, T337H-SP, Aircraft Tires, 200 and 6 more - Effective: October 5, 1978 - Superseded by: Nothing supersedes this AD - Product type: Appliance - Amendment: 39-3312 - Registered aircraft: 765 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/06BCDC8C488D718186256A320069C3F9.0001 - DRS record last changed: January 21, 2026 - Page: https://openairdocs.org/ad/78-20-12 ## The airworthiness directive 78-20-12 FIRESTONE AIRCRAFT TIRES: Amendment 39-3312. Applies to all Firestone size 18x5.5 Mach I, 10 Ply rating part number 00490, serial numbers having the first four numbers 0677, to be replaced by Firestone tire part number 00518 or other approved tire installed on, but not limited to, Lear Jet Models 23, 24, 25; Beech Models 99 series, B100, 200; Swearingen SA 226-TC and Cessna Models 336/337 or T-337 series aircraft. a) Inspect for serial numbers having the first four numbers 0677 P/N 00490. b) Replace with Firestone tires having serial numbers outside of this subject group or with Firestone tire P/N 00518 or with any other tire approved for these aircraft. Obliterate TSO markings on tires identified in this AD to prevent future use on aircraft. This amendment is effective October 5, 1978, as to all persons except those persons to whom it was made immediately effective by the airmail letter dated September 6, 1978, which contained this amendment. ## Affected data sheets (6) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS A6CE](https://openairdocs.org/tcds/A6CE): Textron Aviation Inc.; names 9 of 19 models: 337, T337B, T337E, T337H-SP, T337F, T337G, T337D, T337C… - [TCDS A10CE](https://openairdocs.org/tcds/A10CE): Learjet Inc.; names 2 of 29 models: 24, 25 - [TCDS A14CE](https://openairdocs.org/tcds/A14CE): Textron Aviation Inc.; names 2 of 12 models: B100, 99 - [TCDS A24CE](https://openairdocs.org/tcds/A24CE): Textron Aviation Inc.; names 1 of 37 models: 200 - [TCDS A2CE](https://openairdocs.org/tcds/A2CE): Textron Aviation Inc.; names 1 of 1 models: 336 - [TCDS A8SW](https://openairdocs.org/tcds/A8SW): Ontic Engineering and Manufacturing Inc.; names 1 of 4 models: SA226-TC ## 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: 765 (765 by airframe model, 0 by engine model) - Makers: Beech 462, Cessna 278, Learjet 15, Swearingen 8, Fairchild 1, Gates Lear Jet 1 Models with the most aircraft: - [Beech 200](https://openairdocs.org/model/beech-200): 234 aircraft (airframe model) - [Beech 23](https://openairdocs.org/model/beech-23): 147 aircraft (airframe model) - [Cessna T337G](https://openairdocs.org/model/cessna-t337g): 118 aircraft (airframe model) - [Beech B100](https://openairdocs.org/model/beech-b100): 58 aircraft (airframe model) - [Cessna 337](https://openairdocs.org/model/cessna-337): 50 aircraft (airframe model) - [Cessna 336](https://openairdocs.org/model/cessna-336): 35 aircraft (airframe model) - [Beech 99](https://openairdocs.org/model/beech-99): 23 aircraft (airframe model) - [Cessna T337H](https://openairdocs.org/model/cessna-t337h): 23 aircraft (airframe model) - [Cessna T337B](https://openairdocs.org/model/cessna-t337b): 19 aircraft (airframe model) - [Cessna T337C](https://openairdocs.org/model/cessna-t337c): 15 aircraft (airframe model) - [Swearingen SA226TC](https://openairdocs.org/model/swearingen-sa226tc): 8 aircraft (airframe model) - [Cessna T337D](https://openairdocs.org/model/cessna-t337d): 7 aircraft (airframe model) - [Learjet 24](https://openairdocs.org/model/learjet-24): 7 aircraft (airframe model) - [Cessna T337E](https://openairdocs.org/model/cessna-t337e): 6 aircraft (airframe model) - [Learjet 23](https://openairdocs.org/model/learjet-23): 6 aircraft (airframe model) - [Cessna T337F](https://openairdocs.org/model/cessna-t337f): 5 aircraft (airframe model) - [Learjet 25](https://openairdocs.org/model/learjet-25): 2 aircraft (airframe model) - [Fairchild SA226-TC](https://openairdocs.org/model/fairchild-sa226-tc): 1 aircraft (airframe model) - [Gates Lear Jet 25](https://openairdocs.org/model/gates-lear-jet-25): 1 aircraft (airframe model) All 19 models: https://openairdocs.org/ad/78-20-12/models.md Every aircraft: https://openairdocs.org/ad/78-20-12/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.