SA155RM
Installation of Singer SKK-1000 doppler navigation system, SKQ-601 dead reckoning computer, and Sperry C-12 compass system. Held by Learjet INC, which holds 538 approved modifications in all. Last revised March 7, 2002. System: instruments and avionics.
What it applies to
- Kind of product
- Aircraft
- Design holder
- Twin Commander Aircraft Corporation
- Models
- 685
- Type certificate
- 2A4
- 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.