SH657NW
Installation of Allison 250-C18A, -C18C, -C20, -C20B engine and related changes. Held by Siam Hiller Holdings INC, which holds 27 approved modifications in all. Last revised May 15, 2009. System: engine.
What it applies to
- Kind of product
- Aircraft
- Design holder
- Bell Helicopter Textron; Bell Helicopter Textron; Bell Helicopter Textron; Bell Helicopter Textron; Bell Helicopter Textron; Bell Helicopter Textron; Bell Helicopter Textron; Bell Helicopter Textron; Bell Helicopter Textron; Bell Helicopter Textron
- Models
- 47G-2A, 47G-2A-1, 47G-3B, 47G-3B-1, 47G-3B-2, 47G-3B-2A, 47G-4, 47G-4A, 47G-5, 47G-5A
- Type certificates
- 2H3, 2H3, 2H3, 2H3, 2H3, 2H3, 2H3, 2H3, 2H3, 2H3
- On this site
- Bell 47 478 registered
- The FAA's record
- On the FAA's site
What an approved modification is
A supplemental type certificate is the FAA's approval of a change to a certified design: a new engine or propeller, avionics, an autopilot, floats, a parachute, a larger fuel tank, an ice-protection kit. The company holding it may sell the kit and the paperwork to owners of the listed models; the modification then becomes part of that aircraft's record. The FAA's list says what was approved and for which models, not how many aircraft carry it.
Source: FAA supplemental type certificates (Dynamic Regulatory System). Register counts from the FAA register of October 20, 2026.