The TPE331-10T Engine Conversion

For Commander Models 690A, B, 840, & 900




The Science of Evolution

Introduced in 1965, the 575 shp TPE331 engine evolved into the -1 and -1 Century series engines rated at 715 shp.
Still occupying the same frame size, the compressor was uprated in 1969 to create the first member of the 840 SHP family, the TPE331-3. The TPE 331's evolution continued a year later with introduction of the flat-rated versions of the -3, the -5 and the -6. The TPE331-5 was the engine placed on the turbine Aero Commander.

In the mid -70s, the -8 engine appeared. While the takeoff thermodynamic rating only increased modestly over the 840 SHP series, the altitude performance was greatly enhanced.
The increased demand for altitude performance fostered the development of the 1,000 shp -10 engine, certified in 1978.
A product of evolution, the TPE 331-10T engine has earned a reputation of significant performance and reliability. The engine has been installed on a variety of executive, regional, utility, agricultural and military aircraft throughout the world.

The most popular and highest performing conversion using 10T power has been the Twin Commander 690A, 690B, 840, & 900 models.

An engine rental pool is maintained for owners who want to operate while engines are being serviced. (subject to availability)

High Performance Machine


The 10T Twin Commander Hallmark

  • 300+ KTAS

  • Full power to 16,000 feet

  • 3,500 FPM initial rate of climb, greater than 2000 FPM to FL200

  • 12 minutes to FL290

  • Increased fuel efficiencies

  • Increased range

Prototyped in 1993, and debuting during the 1993 NBAA show, the 10T Twin Commander was introduced to rave reviews. The 10T Commander makes a good plane a great one.

Over ninety 10T modified Twin Commander aircraft are now flying. Current conversion levels exceed one delivered 10T aircraft per month!


Twin Commander

For All The Right Reasons...

Aircraft Performance
Increasing operator capabilities and margins of safety.

Unequaled in its Class
Today's highest performing, most desirable turbo-prop in its class.

A protected investment, reduces annual operating costs.
Over 79% reduction in scheduled HSI/GBI maintenance.

Today's technology and efficiencies--modular design.

Flexible intervals and multiple TBO options.

Retrofit Options
Customized to meet an operator's current needs.

A warranty to match an operator's overhaul choice.

Service and Support
Worldwide, on demand factory support from Twin Commander and Honeywell.

Aircraft Performance

The availability of additional horsepower at all flight levels translates into markedly improved aircraft performance in virtually all flight missions from sea level to cruise altitudes. The ability to climb faster to more fuel efficient altitudes provides an additional benefit on even short stage lengths that might have formerly dictated lower cruise altitudes.

Speed: 300+ KTAS
Climb: 717.5 shaft horsepower to 16,000 feet. 3,500+ fpm through 20,000 feet.

Your 10T Commander is capable to FL 230 in 8 minutes, or FL 290 in only 12 minutes from brake release. This remarkable climb performance gets you above weather fast, keeps you above slower traffic, and departs high, hot locations with unmatched capability.

Unequaled In Its Class

Aircraft Performance Flight Test Data
Flight Test Data (690A) TPE331-5 TPE331-10T
Thermodynamic Shaft Horsepower 840 minimum 1,000 minimum
Flat Rate Torque To 6,000 ft 16,000 ft
Cruise Speed 276 KTAS 300+ KTAS
(ISA, 9,000 lb, 96%, 20,000 ft)

Unequaled In Its Class -
Measured against other turboprops in its class, 10T powered Twin Commanders are unrivaled in overall speed, climb and operating costs.

Turbo Commander 690A 10T MOD Conquest II King Air C90B Cheyenne IIXL
Pratt & Whitney
Pratt & Whitney PT6A-135
Shaft HP 1,000 625 550 620
Common TBO (Hrs) 5,000 3,000 3600 3600
Takeoff Perform SL ISA BFL (ft) 1,833 2,465 2,706 2,940
Max Range (N-Miles) (NBAA IFR Reserves) 1,424 1,566 1,120 1,282
Normal (FPM)
2,824 2,435 2,003 1,750
Engine Out (FPM) 1,003 715 554 470
Normal Cruise TAS 300+ 287 240 255



A decision for a 10T powered Twin Commander is a low risk, high return investment.

Increased Aircraft Value
An investment in the 10T conversion immediately translates into higher market value for Turbo Commander aircraft.

Reduced Hot Section Costs
Extended major inspection intervals reduce maintenance.

Improved Fuel Efficiencies
The 10T has shown up to 7% overall reduced fuel burn over -5.

Cost Cap On First Hot Section Subsequent To Modification
A guaranteed cost cap on maintenance, up to $195,000 lower than maintaining -5 engines.

2 Year Warranty On Turbine Components
AlliedSignal warranties are designed to meet your needs.

Factory Backed Program
A program backed by the engine and aircraft manufacturer guarantees maximum protection of your investment.

High Power Engine Design

TPE331-10T power on the 690 series Commander Aircraft means responsive, reliable flying. A geared propeller driven by a single-shaft power section utilizing dual centrifugal compressors and three axial turbines allows for a compact, low weight, and high power design.

High Technology Cooled Turbine Components
Effective cooling increases component life and reliability.

ITT Replaced By EGT
By virtue of replacing the ITT with an EGT system, 10Ts offer cost benefits through improved reliability.

Improved Thermodynamics
Due to its high thermodynamic rating, 10T engines will operate at less than 72% of rated power at full throttle operation.

The 10T's modular hot section components and factory-initiated enhancement programs result in lower maintenance costs. Additionally, 10T operators can count on reduced downtime by utilizing Honeywell & Twin Commander Aircraft Corporation's Factory Authorized Service Centers.

Flexible Major Maintenance Intervals
Maintenance programs to fit an operators needs.

Factory Developed And Supported Aircraft STC
With an average of 1 conversion a month, the 10T powered Twin Commander is a proven design.

The Retrofit Options


The TPE331-10T conversion program allows for two retrofit options, providing choices in converting Twin Commander aircraft.

Option 1: Overhaul and Modification

Developed for operators nearing overhaul expiration on the -5 engine. However, it may be accomplished at any point in the engine's life with resultant overhaul service bulletin modification standards and warranty benefits.

* Overhaul and Major Inspection Interval Options
Option A Option B **
Hot Section
Hot Section & Gearbox
1,800 hrs.
3,600 hrs.
5,400 hrs.
2,500 hrs.
5,000 hrs.

Option 2: Engine Continued Time Modification

This option makes 10T engine performance available without waiting for the -5 engine to reach its schedule overhaul interval.

* Overhaul and Major Inspection Interval Options
Option A Option B
Hot Section
Hot Section & Gearbox
1,800 hrs.
3,600 hrs.
5,400 hrs.
2,500 hrs.
5,000 hrs.

* Desired overhaul option must be declared at the time of modification to allow for the appropriate log book entries to be accomplished.

** Greatest cost reductions

Warranty Details

Honeywell offers warranty options for 10T conversions.

Overhaul / Conversion

Twenty-four months from date of shipment or twelve months from date of initial operation whichever occurs first for defects in material and workmanship. Additionally, the turbine section will be covered for twenty-four months from the date of initial operation.

Continued Time/Conversion Warranty

Twelve months from date of initial operation on power section and gearbox for defects in material and workmanship; thirty days from initial operation on line replacement items. Additionally, the turbine section will be covered for twenty-four months from date of initial operation.

* Refer to Honeywell Engines Warranties for detail as applicable.

The TPE331 is a turboprop engine utilizing a two stage centrifugal compressor, an annular combustion chamber and three stage axial turbine with an integral gearbox. Horsepower ratings vary from 575 to 1200 horsepower depending upon engine model and installation.