# AD 53-12-01: Horizontal Stabilizer Spar

- Type: Airworthiness directive
- Status: Current
- Products: Hiller UH-12, UH-12A and UH-12B
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Rotorcraft
- Registered aircraft: 57 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/E73FED9C6105CDEB86256A38005F0A1B.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/53-12-01

## The airworthiness directive

53-12-01 HILLER: Applies to All UH-12, UH-12A, UH-12B, HTE-1, HTE-2, H-23A and H-23B Helicopters Incorporating Horizontal Stabilizers With Short Spar Inserts or Without Spar Inserts.

Compliance required as indicated below.

Replacement of the horizontal stabilizer assembly, P/N 37001 on the above helicopters has been found necessary to prevent fatigue failure of the stabilizer spar. (Hiller Service Bulletin No. 26 covers this procedure.)

  (a) Stabilizer assemblies P/N 37001-9 incorporating short spar inserts (5.75 inches) must be removed from service when they have accumulated 300 hours total time. The replacement stabilizer is identified as 37001-14 and incorporates a long spar insert.

  (b) Stabilizer assemblies P/N 37001-7 (without spar insert and identified as 37001) must be removed from service when they have accumulated 1,600 hours total time. The replacement stabilizer is identified as 37001-12 and incorporates a long spar insert.

  (c) Stabilizer assemblies P/N 37001-12 and -14 incorporate long spar inserts (10.29 inches). Attachment to the aft bulkhead socket is made by two AN 174-17 bolts. The total service life of these assemblies is not limited.

## Affected data sheets (2) (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 1 of 2 models: UH-12B

## 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: 57 (57 by airframe model, 0 by engine model)
- Makers: Hiller 53, Hiller-Heli-Cab 1, Hiller-Helicopter Rep SVC 1, Hiller-Tri-Plex Ind.Inc. 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-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-Yehnert UH-12](https://openairdocs.org/model/hiller-yehnert-uh-12): 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-Heli-Cab UH-12B](https://openairdocs.org/model/hiller-heli-cab-uh-12b): 1 aircraft (airframe model)

All 7 models: https://openairdocs.org/ad/53-12-01/models.md
Every aircraft: https://openairdocs.org/ad/53-12-01/aircraft.md

Its text cites no advisory circulars or STCs.

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