The U.S. aircraft register, updated daily
Approved modifications · supplemental type certificate · current · issued

ST09992SC

Replace existing production installed S-225 series Mach Airspeed Indicators with REVUE THOMMEN AG Type 5C18.22.65K.00.0 Mach Airspeed Indicators. Held by Underwood - Instrument Services, INC.. Last revised June 11, 2002. System: instruments and avionics.

What it applies to

Kind of product
Aircraft
Design holder
Learjet Inc.; Learjet Inc.; Learjet Inc.; Learjet Inc.; Learjet Inc.; Learjet Inc.; Learjet Inc.; Learjet Inc.; Learjet Inc.; Learjet Inc.; Learjet Inc.
Models
24, 24A, 24B, 24D, 24F, 25, 25A, 25B, 25C, 25D, 25F
Type certificates
A10CE, A10CE, A10CE, A10CE, A10CE, A10CE, A10CE, A10CE, A10CE, A10CE, A10CE
On this site
Learjet 24 16 registered
Learjet 25 23 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.