COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
Mitsubishi MU-2 Series Aeroplanes
AD/MU-2/42 Autopilot/Electric Trim Switch Standardisation 13/89
Applicability: All model MU 2 equipped with any manual electric trim system and/or any autopilot other than Bendix.
Requirement: 1. Modify the control yoke in the affected model airplanes as follows:
- For MU 2B-35 model aircraft equipped with a King KFC 300 automatic flight control system (AFCS) and a Sperry manual/electric pitch trim system, in accordance with Bendix/King Certification Bulletin No. CB10, KPN 006-0712- 00.
b. For MU 2B-36 model aircraft equipped with a Sperry SPZ-200 AFCS and a MAI manual/electric pitch trim system, in accordance with MHI Kit - Sperry SPZ-200AP Disengagement Drawing, 035A-985006.
2. Configuration check. Visually verify that:
- The autopilot disconnect and trim disconnect/interrupt functions are combined on one button mounted on the outboard control wheel grip, and is so oriented that it is easily activated by the pilot/copilot.
b. The autopilot disconnect and trim disconnect/interrupt button is properly and legibly labelled to indicate functions.
c. The button is red in colour.
d. There are no other red buttons nearby that could be mistaken for the autopilot disconnect.
e. The autopilot circuit breaker is properly labelled.
3. Pitch Trim Disconnect/Interrupt Functional Check.
With the manual electric pitch trim system armed, press the trim button to cause the manual pitch trim wheel to rotate. Verify that when each of the following operations is performed, the manual pitch trim wheel stops moving:
- disconnect/interrupt switch is fully depressed;
b. The master electric power switch is positioned to “OFF”;
c. The radio master switch is positioned to “OFF” (if installed and so configured); (not applicable to MU 2B aircraft equipped with Sperry SPZ-500 autopilots); or
d. The electric trim circuit breaker is pulled. (On some MU 2B aircraft without an electric trim circuit breaker, the autopilot circuit breaker/switch is used to disconnect the system in lieu of the electric trim circuit breaker.)
COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
4. Autopilot Disconnect Functional Check. With the autopilot system engaged, verify:
- That the autopilot system can be overpowered by pushing or pulling on the control yoke; and
b. That, while overpowering the autopilot, the manual pitch trim wheel stops moving and the autopilot disconnects when each of the following operations is performed:
- The disconnect/interrupt switch is depressed;
ii. The master electric power switch is positioned to “OFF”;
iii. The autopilot master switch or the radio master switch or the engage/disengage switch on the autopilot controller (as appropriate), is positioned to “OFF” (On some MU 2B aircraft not equipped with an autopilot master switch beside the controller, the radio master switch must be used to disconnect the system in lieu of the autopilot master switch.);
iv. The autopilot circuit breaker is pulled; or
v. When the “GA” go-around switch on the left power lever is depressed on MU 2B aircraft equipped with Sperry SPZ 500 autopilot.
Note 1: It is very important that the manual pitch trim wheel stops moving after each of the operations of paras 3 or 4b is accomplished.
Note 2: FAA AD 88-21-01 refers.
Compliance: Prior to 31 March 1990.
Background: This AD resulted from a request by the National Transportation Safety Board (US) who while investigating a number of fatal MU 2B accidents, concluded that pilots were becoming confused in the operation of the interrupt/disconnect switches for the electric pitch trim and autopilot systems.
Overview
The Civil Aviation Regulations 1998, enacted by the Commonwealth of Australia, aim to ensure the safety and efficiency of civil aviation in Australia. Within this legislation, Part 39 - 105 Civil Aviation Safety Authority Schedule of Airworthiness Directives addresses specific safety concerns related to aircraft operations. One such directive, AD/MU-2/42, was introduced to address the problem of pilot confusion with the operation of the interrupt/disconnect switches for the electric pitch trim and autopilot systems in Mitsubishi MU-2 Series Aeroplanes. The directive was prompted by recommendations from the National Transportation Safety Board (US) following several fatal MU 2B accidents. The policy objective of AD/MU-2/42 is to standardise the autopilot and electric trim switch operations in MU-2 series aircraft, thereby enhancing flight safety and reducing the risk of pilot error. The directive requires modifications to the control yoke, configuration checks, and functional checks of the autopilot and pitch trim disconnect/interrupt systems to ensure they are easily identifiable and correctly operational.
Scope and Application
The Civil Aviation Regulations 1998, specifically Part 39 - 105, outlines the Civil Aviation Safety Authority's Airworthiness Directives for ensuring the safe operation of aircraft in Australia. This legislation applies to all model MU-2 aeroplanes equipped with any manual electric trim system and any autopilot other than Bendix, ensuring these aircraft meet specific safety standards to prevent accidents related to the confusion of autopilot and electric trim switch operations. This directive mandates modifications to the control yoke and specific operational checks to ensure that the autopilot disconnect and trim disconnect/interrupt functions are clearly identifiable and easily activated by the pilot or copilot. The directive also requires configuration checks to verify the proper labelling and colour-coding of critical switches and the absence of similar red buttons that could cause confusion. Furthermore, functional checks must be performed to ensure the system responds correctly to various operational commands, such as disconnecting the autopilot and stopping the manual pitch trim wheel movement under specified conditions. The directive extends its applicability through subordinate instruments, ensuring compliance with international standards such as those referenced by the Federal Aviation Administration (FAA).
Key Provisions
The Civil Aviation Regulations 1998, Part 39 - 105, under the Civil Aviation Safety Authority’s Schedule of Airworthiness Directives, mandates specific modifications for Mitsubishi MU-2 series aeroplanes, particularly those equipped with certain autopilot and electric trim systems. Section 1 of the directive requires modifications to the control yoke and configuration checks, ensuring the autopilot and electric trim systems are clearly marked and function correctly. This includes combining the autopilot disconnect and trim disconnect/interrupt functions on one button, ensuring it is easily identifiable and not confused with other controls.
These modifications must be made in accordance with specific technical bulletins and drawings provided by the manufacturers, such as Bendix/King Certification Bulletin No. CB10, KPN 006-0712-00, for MU 2B-35 models, and MHI Kit - Sperry SPZ-200AP Disengagement Drawing, 035A-985006, for MU 2B-36 models. The directive also mandates a configuration check to verify that the combined button is properly labelled, coloured red, and uniquely identifiable. Additionally, it requires functional checks to ensure that the autopilot and trim systems disconnect properly when specific switches are operated.
The obligations imposed by this directive are stringent, demanding that aircraft owners and operators adhere to precise technical standards to ensure the safety of the aircraft and its occupants. They must ensure that the autopilot and electric trim systems are modified as specified, and that all checks are conducted and documented properly. This includes verifying that the autopilot can be manually overpowered and that the trim wheel stops moving when the appropriate switches are operated.
Failure to comply with these airworthiness directives can result in significant legal consequences. The directive must be adhered to by 31 March 1990, and non-compliance could lead to enforcement actions by the Civil Aviation Safety Authority. Potential penalties may include fines, suspension of airworthiness certificates, or other regulatory actions. The directive was issued in response to fatal accidents investigated by the National Transportation Safety Board (US), highlighting the critical importance of proper system operation to prevent pilot confusion and ensure flight safety.