SPW-3
Modification of Hamilton Standard4A2-V5 propeller governor to NWP-D18 on aircraft with Pratt & Whitney R-985 engines. Held by Northwest Propeller INC, which holds 2 approved modifications in all. Last revised January 1, 1960. System: propeller.
What it applies to
- Kind of product
- Propeller
- Design holder
- Hartzell Propeller Inc.
- Models
- HC-B3Z
- Type certificate
- P-907
- 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 8, 2026.