SA00622LA

Installation of an electronic digital engine tachometer horizon model P-1000. Held by Horizon Instruments INC, which holds 23 approved modifications in all. Last revised January 14, 2002. System: engine.

What it applies to

Kind of product: Aircraft
Design holder: Air Tractor Inc.; Air Tractor Inc.; Air Tractor Inc.; Air Tractor Inc.; Air Tractor Inc.; Air Tractor Inc.; Air Tractor Inc.; Ayres Corporation; Ayres Corporation; Ayres Corporation; Ayres Corporation; Ayres Corporation; Ayres Corporation; Ayres Corporation; Ayres Corporation; Ayres Corporation; Ayres Corporation; Ayres Corporation; Ayres Corporation; Weatherly Aviation Company Inc.; Allied Ag Cat Productions Inc.; Allied Ag Cat Productions Inc.; Allied Ag Cat Productions Inc.; Allied Ag Cat Productions Inc.
Models: AT-401B, AT-501, AT-401A, AT-401, AT-250, AT-300, AT-301, 600-S2C, S-2C, S-2B, S2R-R1340, S2R-R3S, S2R, 600 S-2D, 600 S2D, S2R, S2R-R1340, S2R-R1820, S2R-R3S, 620, G-164, G-164A, G-164B, G-164C
Type certificates: A17SW, A17SW, A17SW, A17SW, A9SW, A9SW, A9SW, 2A7, 2A7, 2A7, A3SW, A3SW, A3SW, A3SW, A4SW, A4SW, A4SW, A4SW, A4SW, A26WE, 1A16, 1A16, 1A16, 1A16
On this site: Ag-Cat Corporation G-164 5 registered
Air Tractor Inc AT-301 84 registered
Air Tractor Inc AT-401 68 registered
Ayres Corporation S-2 244 registered
Snow 600 7 registered
Weatherly Aviation Co Inc 620 29 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.