Operating Information Letter Honeywell International 

1944 E. Sky Harbor Circle 

Phoenix, AZ 85034

1 of 3 OI331-18R4 

 May 26, 2009

PLEASE DISTRIBUTE TO ALL AFFECTED FLIGHT CREW MEMBERS AND 

MAINTENANCE PERSONNEL 

TO: All Owners/Operators, Airframe Manufacturers, Distributors, 

Sales and Service Organizations, and Field Service Representatives 

APPLICATIONS: All TPE331 Series Engines equipped with Woodward Fuel 

Control Units, except TPE331-14/15 series engines. 

PURPOSE: The purpose of this OIL is to inform operators of single-engine 

aircraft only, of the probable engine responses following a loss 

of drive between the engine driven fuel pump and fuel control 

governor system. This OIL does not apply to multi-engine 

aircraft. Reference OI331-12R6 for multi-engine operation. 

WARNING 

This OIL is intended to inform the operator of the probable engine responses

following a loss of drive between the engine driven fuel pump and fuel control 

governor system. Subsequent handling of the engine and control of the aircraft must be performed/maintained per the aircraft’s Pilot Operating Handbook (POH), Aircraft Flight Manual (AFM) or Manufacturer’s Operating Manual 

(MOM), whichever is appropriate. 

DISCUSSION

Engine response following a loss of drive between the engine driven fuel pump and the fuel control 

governor system is dependent on the phase of operation (ground engine start, ground or flight operations) and whether the fuel control is in compliance with one of three engine model specific bulletins 

(TPE331-A73-0254, TPE331-A73-0262 and TPE331-A73-0271). If the fuel control installed on the 

engine is not in compliance with one of the applicable service bulletins, a loss of drive between the 

engine driven fuel pump and fuel control governor system will result in a condition where the fuel 

control underspeed governor will increase fuel flow along the acceleration schedule until reaching 

the maximum fuel flow stop setting. The fuel flow increase will result in a rapid, uncommanded, uncontrolled increase in fuel flow to the engine. Service Bulletins TPE331-A73-0254, TPE331-A73-

0262 and TPE331-A73-0271 implement an improved overspeed governor mechanism in the fuel 

control assembly that will limit fuel flow if loss of drive occurs between the fuel pump and the fuel 

control assembly. Fuel flow in the modified controls is limited to approximately 180 pph, which 
Honeywell International Operating Information Letter 1944 E. Sky Harbor Circle 

Phoenix, AZ 85034

2 of 3 OI331-18R4 

 May 26, 2009

represents a low flight idle, minimum power condition. There will be no response to power lever 

movements. 

ENGINE RESPONSE FOLLOWING A FUEL CONTROL DRIVE FAILURE DURING

DIFFERENT PHASES OF OPERATION

 ENGINES WITH FUEL CONTROLS THAT ARE NOT IN COMPLIANCE WITH 

SERVICE BULLETINS TPE331-A73-0254, TPE331-A73-0262 AND TPE331-A73-0271: 

- During ground engine starts (with the propeller ON the start locks). 

WARNING 

- END – 

During ground engine starts (with the propeller ON 

the start locks), the engine will experience a rapid 

uncommanded, uncontrolled acceleration to an 

overspeed condition sufficient to cause an 

uncontained separation of high speed rotating 

components. 

- If an engine exhibits rapidly increasing RPM above normal idle values, immediately 

abort the engine start. 

- During ground or flight operation (with the propeller OFF the start locks), the engine 

will experience a rapid uncommanded, uncontrolled increase in RPM, torque and/or turbine 

temperature (the engine may exceed RPM, torque and/or turbine temperature limits) and 

increased forward thrust. Reverse thrust will not be available. 

- In the event of a rapid uncontrolled fuel flow increase with a subsequent increase in 

RPM, torque and/or turbine temperature, and if engine power fails to respond when the 

power lever is retarded, shut down the affected engine as soon as possible consistent 

with safe operation of the aircraft. Do not move the power lever aft of flight idle. 
Honeywell International Operating Information Letter 1944 E. Sky Harbor Circle 

Phoenix, AZ 85034

3 of 3 OI331-18R4 

 May 26, 2009

WARNING 

The onset of the conditions listed above is rapid, uncommanded and 

uncontrolled. Honeywell recognizes the numerous combinations of 

engines, propellers and airframes to which OI331-18R4 is applicable. 

Therefore, Honeywell cannot assess which of the conditions listed above 

will be present or the severity to which they will be present for each 

installation. Honeywell strongly recommends that the aircraft owner 

consult the holder of the Type Certificate or Supplemental Type Certificate 

for their aircraft in order to evaluate the extent to which these conditions 

will exist. 

CAUTION 

If an engine exhibits an uncontrolled fuel flow condition, never retard the 

power levers aft of flight idle.

CAUTION 

If an engine has been shut down in flight or on the ground as a result of 

exhibiting a rapid uncontrolled increase in RPM, torque and/or turbine 

temperature, do not attempt a ground start until after inspecting the fuel 

control drive in accordance with the applicable Service Bulletin or 

Maintenance Manual. 

 ENGINES WITH FUEL CONTROLS THAT ARE IN COMPLIANCE WITH SERVICE 

BULLETINS TPE331-A73-0254, TPE331-A73-0262 AND TPE331-A73-0271: 

- During certain high altitude ground engine starts (with the propeller on the start locks), 

the modified fuel control may provide fuel flow that is sufficient to cause the engine to accelerate to an overspeed condition and cause an uncontained separation of high speed rotating components. Initiate an emergency shutdown of the affected engine before the engine 

speed exceeds 105.5 percent RPM.

- During ground or flight operation (with the propeller off the start locks), the engine will 

not respond to power lever movements. Fuel flow will be limited to approximately 180 pph, 

which represents a low flight idle, minimum power condition.

Note: As with any document that has been revised, as OI331-18 has, discard any and all revisions 

prior to OI331-18R4. Apply only the information communicated in OI331-18R4. 

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