# AD 58-02-03: Carburetor Mixture Control Removal - Type: Airworthiness directive - Status: Current - Products: Hiller UH-12, UH-12A, UH-12B, UH-12C and UH-12D - Superseded by: Nothing supersedes this AD - Product type: Aircraft, Rotorcraft - Registered aircraft: 117 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/9649EFCFB77F44BE86256A38005F3ABB.0001 - DRS record last changed: May 30, 2024 - Page: https://openairdocs.org/ad/58-02-03 ## The airworthiness directive 58-02-03 HILLER: Applies to UH-12 Series Helicopters Equipped With Marvel- Schebler Automatic Altitude Compensating Carburetor Model MA-4-5AA (Aircooled P/N 19588). Compliance required by June 1, 1958. With a Marvel-Schebler Model MA-4-5AA carburetor installed, it is possible to start and run the engine with the carburetor mixture control in the idle cutoff position if the throttle is partially or fully opened. However, as soon as the throttle is fully closed, the idle cutoff will operate and shut off the engine. Therefore, it would be possible to start the engine, take off, and fly with the mixture in idle cutoff, as long as the throttle is never closed. The first time the throttle is closed, however, as in autorotation, an immediate engine stoppage would occur. To prevent inadvertent engine stoppage in flight due to failure to place the carburetor mixture control in the "ALT.COMP" position before takeoff, the following measure is necessary: Delete the carburetor mixture control from the cockpit and secure the carburetor setting at "ALT.COMP" at the carburetor. Hiller will issue a service bulletin covering this subject. Appropriate FAA approved Helicopter Flight Manual revision required. ## Affected data sheets (3) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS 6H1](https://openairdocs.org/tcds/6H1): Siam Hiller Holdings Inc.; names 2 of 2 models: UH-12, UH-12A - [TCDS 6H2](https://openairdocs.org/tcds/6H2): Siam Hiller Holdings Inc.; names 2 of 2 models: UH-12C, UH-12B - [TCDS 4H10](https://openairdocs.org/tcds/4H10): Siam Hiller Holdings Inc.; names 1 of 1 models: UH-12D ## 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: 117 (117 by airframe model, 0 by engine model) - Makers: Hiller 106, Hiller - World Helicopters 2, Hiller-Osborn 2, Hiller-Felt 1, Hiller-Heli-Cab 1, Hiller-Helicopter Rep SVC 1, Hiller-Stanley 1, Hiller-Tri-Plex Ind.Inc. 1, Hiller-Trident Helicopters 1, Hiller-Yehnert 1 Models with the most aircraft: - [Hiller UH-12B](https://openairdocs.org/model/hiller-uh-12b): 35 aircraft (airframe model) - [Hiller UH-12C](https://openairdocs.org/model/hiller-uh-12c): 31 aircraft (airframe model) - [Hiller UH-12D](https://openairdocs.org/model/hiller-uh-12d): 22 aircraft (airframe model) - [Hiller UH-12A](https://openairdocs.org/model/hiller-uh-12a): 16 aircraft (airframe model) - [Hiller UH-12](https://openairdocs.org/model/hiller-uh-12): 2 aircraft (airframe model) - [Hiller - World Helicopters UH-12C](https://openairdocs.org/model/hiller-world-helicopters-uh-12c): 2 aircraft (airframe model) - [Hiller-Osborn UH-12D](https://openairdocs.org/model/hiller-osborn-uh-12d): 2 aircraft (airframe model) - [Hiller-Yehnert UH-12](https://openairdocs.org/model/hiller-yehnert-uh-12): 1 aircraft (airframe model) - [Hiller-Stanley UH-12C](https://openairdocs.org/model/hiller-stanley-uh-12c): 1 aircraft (airframe model) - [Hiller-Felt UH-12C](https://openairdocs.org/model/hiller-felt-uh-12c): 1 aircraft (airframe model) - [Hiller-Helicopter Rep SVC UH-12B](https://openairdocs.org/model/hiller-helicopter-rep-svc-uh-12b): 1 aircraft (airframe model) - [Hiller-Tri-Plex Ind.Inc. UH-12B](https://openairdocs.org/model/hiller-tri-plex-ind-inc-uh-12b): 1 aircraft (airframe model) - [Hiller-Trident Helicopters UH-12C](https://openairdocs.org/model/hiller-trident-helicopters-uh-12c): 1 aircraft (airframe model) - [Hiller-Heli-Cab UH-12B](https://openairdocs.org/model/hiller-heli-cab-uh-12b): 1 aircraft (airframe model) All 14 models: https://openairdocs.org/ad/58-02-03/models.md Every aircraft: https://openairdocs.org/ad/58-02-03/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.