Subject: INSTALLATION, INSPECTION, AND
MAINTENANCE OF CONTROLS FOR
GENERAL AVIATION RECIPROCATING
AIRCRAFT ENGINES
Date: 6/06/00
Initiated By: ACE-100
AC No: 20-143
Change:
1. PURPOSE. A review of service history on engine control installations indicates that a
significant percentage of the problems are related to maintenance. Of the control system problems
related to maintenance, approximately 75 percent of the problems with these systems result from lack
of proper maintenance of airplane manufacturer installed engine controls. The other 25 percent of the
service problems originate from a lack of maintenance of the engine manufacturers’ throttle, mixture,
and propeller governor levers/linkages. Most airplane or engine maintenance manuals lack detailed
information on inspection and installation of engine controls. Therefore, this advisory circular (AC)
presents information regarding the inspection, maintenance, and installation of engine controls with
emphasis on the airframe portion of these systems. It provides guidance to design and maintenance
personnel to reduce the number of airplane accidents and incidents related to the loss of engine power
control. This material is neither mandatory nor regulatory in nature and does not constitute a
regulation. This AC is provided to supplement, but not replace the procedures in the manufacturers'
maintenance manuals. Where the content of this AC differs from, or conflicts with, the
manufacturer's maintenance manual, instructions contained in the manufacturer's manual take
precedence over the guidelines provided in this AC.
2. RELATED REGULATIONS. Title 14 Code of Federal Regulations (14 CFR) Part 21,
§ 21.50. Airplane airworthiness regulations are specified in 14 CFR Part 23, §§ 23.1141, 23.1143,
23.1147, 23.1149, and 23.1529, and the corresponding Civil Air Regulations (CAR) under Part 3.
Engine airworthiness regulations are specified in 14 CFR Part 33, §§ 33.4, 33.15 and 33.19, and their
corresponding CAR under Part 13. Propeller airworthiness regulations are specified in 14 CFR Part
35, § 35.4, and the corresponding CAR under Part 14. Inspection requirements can be found in 14
CFR Part 43, appendix D, and § 43.15(c).
3. BACKGROUND. Current 14 CFR design rules require throttle and mixture controls on
single reciprocating engine-powered airplanes that will allow continued safe flight and landing in the
event of a control separation at the engine fuel metering device. The current rules (§§ 23.1143(g) and
23.1147(b)) are not applicable to older airplanes. This AC has been prepared to address proper
