# AD 94-26-07: Fuel Control Governor Drive

- Type: Airworthiness directive
- Status: Current
- Products: Honeywell International TPE331-10, TPE331-10A, TPE331-10B, TPE331-10G, TPE331-10GR, TPE331-10J, TPE331-10N, TPE331-10R, TPE331-10U, TPE331-10UA, TPE331-10UF, TPE331-10UG and 23 more
- Effective: April 18, 1995
- Published: April 3, 1995, 60 FR 16782–16785
- Issued as: Final rule, request for comments
- Superseded by: Nothing supersedes this AD
- Product type: Engine
- Amendment: 39-9178
- Docket: 94-ANE-46
- Registered aircraft: 704 may be affected, by airframe or engine model (OpenAirDocs)
- Official PDF: https://openairdocs.org/files/sha256/aa/d0/aad0a02378b57bc58b89c639b674f6b2ba90db2b90c3c8c8977f81fc1a557bbb (from https://www.govinfo.gov/content/pkg/FR-1995-04-03/pdf/95-7908.pdf)
- Federal Register: https://www.federalregister.gov/documents/1995/04/03/95-7908/airworthiness-directives-alliedsignal-inc-tpe331-series-turboprop-engines
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/9649AC2AE50462A786256843005DE0F2.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/94-26-07

## Summary

This document publishes in the Federal Register an amendment adopting Airworthiness Directive (AD) 94-26-07 that was sent previously to all known U.S. owners and operators of AlliedSignal Inc. TPE331 series turboprop engines by individual letters. This AD requires an amendment to the Emergency Procedures section of the applicable FAA Approved Airplane Flight Manual (AFM) for each applicable engine installation in an aircraft, and initial and repetitive dimensional inspections of the fuel control drive shaft splines for wear, or replacing the affected fuel controls with alternate fuel controls. This amendment is prompted by reports of excessive wear of the internal fuel control drive splines in fuel controls, which can result in loss of fuel control governor drive. The actions specified by this AD are intended to prevent an uncontained engine failure, damage to the aircraft, or loss of aircraft control.

## The airworthiness directive

94-26-07 AlliedSignal Inc.: Amendment 39-9178. Docket 94-ANE-46.

Applicability: AlliedSignal Inc. Models TPE331-3, -5, -6, -10, -11U, and -12 series turboprop engines with fuel control assembly Part Numbers (P/N) 897770-1 through 897770-8 and 897780-1 through 897780-11 installed in accordance with AlliedSignal Inc. Service Bulletin (SB) No. TPE331-73-0217, dated July 9, 1993. These engines are installed on but not limited to Mitsubishi MU-2B series (MU-2 series) Solitaire/Marquise, Construcciones Aeronauticas, S.A. C-212 series, British Aerospace (BAe) Jetstream 3101 and 3201 (31 and 32) series, Fairchild SA226 and SA227 series (Swearingen Merlin and Metro series), Twin Commander Models 680, 690, 695 (Jetprop Commander), Short Brothers and Harland, Ltd. SC7 (Skyvan), Dornier 228 series, Beech Model B-100 series aircraft, and Ayres S-2R series aircraft.

Compliance: Required as indicated, unless accomplished previously.

To prevent failure of the fuel control governordrive from excessive wear of the internal fuel control drive splines, which can result in loss of aircraft control, accomplish the following:

  (a) Amend the applicable FAA Approved Airplane Flight Manual (AFM) to provide interim emergency procedures to flight crews, within 20 calendar days after the effective date of airworthiness directive (AD), by adding the following to the Emergency Procedures section. This may be accomplished by inserting a copy of this AD into the AFM:

"Inflight: in the event of an uncommanded engine torque and turbine temperature increase, or if engine power fails to respond when the power level is retarded, shut down the affected engine as soon as possible consistent with the safe operation of the aircraft.

Warning: be aware that the affected engine with a failed fuel control governor drive will typically exhibit an increase in power, and if the accepted "dead foot--dead engine" logic is employed, the wrong engine could be shut down because the malfunction will result in an increase in forward thrust from the affected engine. Use caution and monitor cockpit engine indications to aid in identifying the failure mode and the malfunctioning engine.

During Ground Start: if an engine exhibits rapidly increasing RPM above idle values, immediately terminate the start.

If an engine has been shutdown inflight as a result of exhibiting an uncontrolled increase in torque and turbine temperature, do not attempt a ground start until the fuel control is inspected in accordance with the applicable service bulletin.

During Reverse Operation: if an engine suddenly develops forward thrust, immediately terminate reverse thrust. If necessary, shutdown both engines in order to maintain directional control."

  (b) For AlliedSignal Model TPE331-11U engines:

  (1) Conduct initial and repetitive dimensional inspections of the fuel control drive shaft splines for wear in accordance with the compliance times and procedures described in AlliedSignal Alert Service Bulletin (SB) No. TPE331-A73-0221, Revision 2, dated October 10, 1994. The initial inspection compliance times start upon the effective date of this priority letter AD.

  (2) Prior to further flight replace with a serviceable part those fuel controls with drive shaft splines that do not meet the return to service criteria specified in AlliedSignal Alert SB No. TPE331-A73-0221, Revision 2, dated October 10, 1994.

  (3) Replacement of fuel controls in accordance with the procedures described in AlliedSignal SB No. TPE331-73-0224, dated August 17, 1994, or Revision 1 of that SB, dated September 8, 1994, with alternate fuel controls constitutes terminating action to the AFM amendment specified in paragraph (a) of this AD, and the inspections specified in paragraph (b)(1) of this AD.

  (c) For AlliedSignal TPE331-3, -5, -6, -10, and -12 series engines:

  (1) Conduct initial and repetitive dimensional inspections of the fuel control driveshaft splines for wear in accordance with the compliance times and procedures described in AlliedSignal Inc. Alert SB No. TPE331-A73-0226, dated October 10, 1994. The initial inspection compliance times become effective upon the effective date of this AD.

  (2) Prior to further flight replace with a serviceable part those fuel controls with drive shaft splines that do not meet the return to service criteria specified in AlliedSignal Inc. Alert SB No. TPE331-A73-0226, dated October 10, 1994.

  (3) Replacement of fuel controls in accordance with the procedures described in AlliedSignal Inc. SB No. TPE331-73-0228, dated September 16, 1994, with alternate fuel controls constitutes terminating action to the AFM amendment specified in paragraph (a) of this AD, and the inspections specified in paragraph (c)(1) of this AD.

  (d) For the purpose of this AD, specific driveshaft operating hours as referenced in AlliedSignal Alert SB No. TPE331-A73-0221, Revision 2, dated October 10, 1994, and AlliedSignal Inc. Alert SB No. TPE331-A73-0226, dated October 10, 1994, may be calculated using fuel control time tracking based on engine operating hours.

  (e) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Los Angeles Aircraft Certification Office. The request should be forwarded through an appropriate FAA Maintenance Inspector, who may add comments and then send it to the Manager, Los Angeles Aircraft Certification Office. NOTE: Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the Los Angeles Aircraft Certification Office.

  (f) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the aircraft to a location where the requirements of this AD can be accomplished.

  (g) The actions required by this AD shall be done in accordance with the following SB's:

Document No. Pages Revision Date AlliedSignal Inc. Alert SB No. TPE331-A73-0226

1-8

Original

October 10, 1994 Woodward SB No. WG64050 1-13 Original October 3, 1994 Total pages: 21.

AlliedSignal Inc. Alert SB No. TPE331-A73-0221 1-3 4 2 Original October 10, 1994 June 27, 1994 Woodward SB No. WG64047 1-12 4 October 3, 1994 Total pages: 16.

AlliedSignal Inc. SB No. TPE331-73-0224 1 2 3-4 1 Original 1 September 8, 1994 August 17, 1994 September 8, 1994 Total pages: 4.

Woodward SB No. WG4044 1-3 Original June 28, 1993 Total pages: 3.

NOTE: The Woodward SB's are attached to the AlliedSignal Alert SB's.

Document No. Pages Revision Date AlliedSignal Inc. SB No. TPE331-73-0228

1-10

Original

September 16, 1994 Total pages: 10.

AlliedSignal Inc. SB No. TPE331-73-0217

1-10

Original

July 9, 1993 Total pages: 10

This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from AlliedSignal Inc., Aviation Services Division, Data Distribution, Dept. 64-3/2102-1M, P.O. Box 29003, Phoenix, AZ 85038-9003; telephone (602) 365-2548. Copies may be inspected at the FAA, New England Region, Office of the Assistant Chief Counsel, 12 New England Executive Park, Burlington, MA; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

  (h) This amendment becomes effective April 18, 1995, to all persons except those persons to whom it was made immediately effective by priority letter AD 94-26-07, issued December 13, 1994, which contained the requirements of this amendment.

## Rule preamble

### Supplementary information

On December 13, 1994, the Federal Aviation Administration (FAA) issued priority letter airworthiness directive (AD) 94-26-07, applicable to certain AlliedSignal Inc. TPE331 series turboprop engines, which requires an amendment to the Emergency Procedures section of the applicable FAA Approved Airplane Flight Manual (AFM) for each applicable engine installation in an aircraft, and initial and repetitive dimensional inspections of the fuel control drive shaft splines for wear, or replacing the affected fuel controls with alternate fuel controls. That action was prompted by reports of excessive wear of the internal fuel control drive splines in fuel controls, Part Numbers (P/N) 897770-1 through -8, and 897780-1 through -11. In two instances the spline wear resulted in loss of fuel control governor drive. If this occurs, the underspeed fuel governor increases fuel flow, while the overspeed governor is inoperative and cannot limit engine speed.

The FAAhas determined that the most serious consequence of a loss of fuel control governor drive is during reverse thrust when the engine suddenly develops uncommanded forward thrust causing an asymmetric thrust condition on a twin-engine aircraft. Another serious consequence of a loss of fuel control governor drive is during engine start when rapid engine acceleration beyond normal idle speed could result in rotor speed sufficient to cause an uncontained turbine separation. During flight, when the propeller is in propeller-governing mode, the result will be uncommanded increased engine torque and turbine temperature. These conditions, if not corrected, could result in an uncontained engine failure, damage to the aircraft, or loss of aircraft control.

The FAA has reviewed and approved the technical contents of the following service bulletins (SB): AlliedSignal Inc. Alert SB No. TPE331-A73-0221, Revision 2, dated October 10, 1994, applicable to model TPE331-11U engines, that describesprocedures for dimensionally inspecting fuel control drive shaft splines; AlliedSignal Inc. SB No. TPE331-73-0224, dated August 17, 1994, and Revision 1, dated September 8, 1994, applicable to model TPE331-11U engines, that describe procedures for replacing affected fuel controls with alternate fuel controls; AlliedSignal Inc. Alert SB No. TPE331-A73-0226, dated October 10, 1994, applicable to certain TPE331-3, -5, -6, -10, and -12 series engines, that describe procedures for dimensionally inspecting fuel control drive shaft splines; and AlliedSignal Inc. SB No. TPE331-73-0228, dated September 16, 1994, applicable to certain TPE331-3, -5, -6, -10, and -12 series engines TPE331 engines, that describe procedures for replacing affected fuel controls with alternate fuel controls.

Since the unsafe condition described is likely to exist or develop on other engines of the same type design, the FAA issued priority letter AD 94-26-07 to prevent an uncontained engine failure, damage to theaircraft, or loss of aircraft control. The AD requires an amendment to the Emergency Procedures section of the applicable FAA AFM for each applicable engine installation in an aircraft. This amendment to the applicable AFM describes conditions inflight, during ground start, and during reverse thrust operation that might indicate loss of fuel control governor drive, and provides required procedures for engine shutdown. These AFM changes have been coordinated with the FAA Directorate responsible for the certification of the aircraft involved.

In addition, this AD requires either initial and repetitive dimensional inspections of the fuel control drive shaft splines for wear, or replacing the affected fuel controls with alternate fuel controls. Replacement with the alternate fuel controls constitutes terminating action to the repetitive inspections. The actions are required to be accomplished in accordance with the service bulletins described previously.

Since it was found that immediate corrective action was required, notice and opportunity for prior public comment thereon were impracticable and contrary to the public interest, and good cause existed to make the AD effective immediately by individual letters issued on December 13, 1994, to all known U.S. owners and operators of AlliedSignal Inc. TPE331 series turboprop engines. These conditions still exist, and the AD is hereby published in the Federal Register as an amendment to Section 39.13 of part 39 of the Federal Aviation Regulations (14 CFR part 39) to make it effective to all persons. Comments Invited

Although this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications should identify the Rules Docket number and be submitted in triplicate to the address specified under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in responseto this notice must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 94-ANE-46." The postcard will be date stamped and returned to the commenter.

The regulations adopted herein will not have substantial direct effects on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES."

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

Adoption of the Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:

PART 39 - AIRWORTHINESS DIRECTIVES 1. The authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89.

39.13 - [AMENDED] 2. Section 39.13 is amended by adding the following new airworthiness directive:

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS E4WE](https://openairdocs.org/tcds/E4WE): Honeywell Aerospace US LLC; names 35 of 48 models: TPE331-10UGR, TPE331-10J, TPE331-10UK, TPE331-12B, TPE331-5A, TPE331-10UG, TPE331-12UA, TPE331-10UR…

## Registered aircraft it may apply to (OpenAirDocs)

Matched by airframe and engine model; the AD's applicability may narrow it by serial number, part number or equipment.

- Aircraft: 704 (0 by airframe model, 704 by engine model)
- Makers: Cessna 129, Mitsubishi 108, Fairchild 69, Ayres 53, Swearingen 52, Rockwell International 51, Construcciones Aeronauticas 25, Gulfstream AM Corp Comm Div 24, General Atomics Aero Systems 22, Beech 21

Models with the most aircraft:

- [AiResearch TPE331 series](https://openairdocs.org/engine/airesearch-tpe331-series): 492 aircraft (engine model)
- [Honeywell TPE331-SER series](https://openairdocs.org/engine/honeywell-tpe331-ser-series): 28 aircraft (engine model)
- [Garrett TPE331-12B](https://openairdocs.org/engine/garrett-tpe331-12b): 19 aircraft (engine model)
- [Honeywell TPE331-10 series](https://openairdocs.org/engine/honeywell-tpe331-10-series): 17 aircraft (engine model)
- [Honeywell TPE331-10](https://openairdocs.org/engine/honeywell-tpe331-10): 13 aircraft (engine model)
- [Honeywell TPE331-10R](https://openairdocs.org/engine/honeywell-tpe331-10r): 13 aircraft (engine model)
- [Garrett TPE331-11U](https://openairdocs.org/engine/garrett-tpe331-11u): 12 aircraft (engine model)
- [Honeywell TPE331-10N](https://openairdocs.org/engine/honeywell-tpe331-10n): 11 aircraft (engine model)
- [Alliedsign TPE331-12UHR](https://openairdocs.org/engine/alliedsign-tpe331-12uhr): 10 aircraft (engine model)
- [Garrett TPE331-10N](https://openairdocs.org/engine/garrett-tpe331-10n): 8 aircraft (engine model)
- [Honeywell TPE331-11U](https://openairdocs.org/engine/honeywell-tpe331-11u): 8 aircraft (engine model)
- [Garrett TPE331-5](https://openairdocs.org/engine/garrett-tpe331-5): 7 aircraft (engine model)
- [Garrett TPE331-10](https://openairdocs.org/engine/garrett-tpe331-10): 7 aircraft (engine model)
- [Garrett TPE331-10 series](https://openairdocs.org/engine/garrett-tpe331-10-series): 7 aircraft (engine model)
- [Garrett TPE331-6](https://openairdocs.org/engine/garrett-tpe331-6): 6 aircraft (engine model)
- [Garrett TPE331-10R](https://openairdocs.org/engine/garrett-tpe331-10r): 5 aircraft (engine model)
- [Garrett TPE331-12UHR](https://openairdocs.org/engine/garrett-tpe331-12uhr): 5 aircraft (engine model)
- [Honeywell TPE331-10U](https://openairdocs.org/engine/honeywell-tpe331-10u): 4 aircraft (engine model)
- [Honeywell TPE331-12UHR](https://openairdocs.org/engine/honeywell-tpe331-12uhr): 3 aircraft (engine model)
- [Honeywell TPE331-6](https://openairdocs.org/engine/honeywell-tpe331-6): 3 aircraft (engine model)

All 40 models: https://openairdocs.org/ad/94-26-07/models.md
Every aircraft: https://openairdocs.org/ad/94-26-07/aircraft.md

No proposed rule in this release led to it. Its text cites no advisory circulars or STCs.

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