# AD 52-01-08: Collective Pitch Incidence Arms

- 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- Superseded by: Nothing supersedes this AD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/7C4B780EA1A1BFFD86256A38005F067A.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/52-01-08

## The airworthiness directive

52-01-08 HILLER: Applies to All Models UH-12, -12A and -12B Helicopters, Serial Numbers 104 and Up. (Incorporating Chrome Plated Main Rotor Blade Incidence Arms P/N 31114-1.)

Compliance required not later than the next 25-hour inspection, or not later than February 1, 1952, whichever occurs first and also as noted below.

As a precautionary measure to preclude possible serious danger which could result from failure of the main rotor blade collective pitch incidence arms (P/N 31114-1), the following should be accomplished:

  (a) Inspect all main blade incidence arms (P/N 31114-1) to determine if chrome plated arms are installed.

  (b) If chrome plated arms are installed, remove and magnaflux or magnaglow inspect each arm for possible minute cracks in the circumferential area of the flange radii.

  (c) If the arm has had 100 hours service and cracks are not found, the part may be reinstalled and further compliance with this Note is not required. If the arm has lessthan 100 hours service, it must again be inspected at 100 hours or not to exceed 125 hours of service. If cracks are found in any arm, it must be replaced immediately.

  (d) This Note also applies to spare and replacement chrome plated arms which should be inspected at 25 and 100 hours service as indicated above.

(Hiller Helicopter's Mandatory Service Bulletin No. 20 covers this same subject.)

## 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/52-01-08/models.md
Every aircraft: https://openairdocs.org/ad/52-01-08/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.