MARKET OVERVIEWS: UAV ENGINES

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Introduction

Reliability, endurance, weight, size and fuel are the keydrivers in the development of UAV power plants. As moremission types are found for UAVs in both the civilian andmilitary arenas, the need for continuous development ofengine technology and fuel efficiencies becomes ever morecrucial. Military persistent surveillance missions are set toextend into weeks or months rather than the currentmissions lasting just a few days at the most. Thetelecommunications industry is looking into UAVs as areplacement for Low Earth Orbit (LEO) satellites for its ownrelay needs which would also require missions lasting muchlonger than current endurance capabilities. Reliability is akey requirement for the operation of UAVs in controlledairspace, which is itself a prerequisite for the UAV industryto realise its full market potential.

The military would prefer to extend the use of heavy enginefuels (HFEs) for their UAV systems, especially on board ship,not just for safety reasons but also to simplify the logisticsof fuel supply. Diesel-powered engines are one routetowards a solution, as is the use of kerosene-based jet fuelssuch as the JP-4/5/8 types. The US Army is spending a lot oftime and money on its goal to use JP-8 fuel on all of its landand air-based weapon systems. As part of this effort,Northrop Grumman announced in June 2004 that it hadcompleted successful tests of a US Army RQ-5A HunterUAV with a new heavy fuel engine.

Mini and micro UAVs are stretching the imaginations ofthose involved in electric motor development, particularly inbattery and fuel cell technology. Boeing technicians at theAdvanced Unmanned Systems unit of the Phantom WorksIntegrated Defense Advanced Systems (IDeAS) haveintegrated fuel cells onto some of their UAV designs and aredeveloping a hybrid system combining fuel cells and withsolar panels manufactured by Boeing Spectrolab. BoeingResearch and Technology Europe in Madrid, Spain, createdin 2002, is working on a parallel project to develop fuel celltechnology for commercial aircraft applications. Teamedwith Intelligent Energy (UK), Diamond Aircraft (Austria),Advanced Technology Products (USA) as well as the Spanishcompanies Sener and Aerlyper, the project will integratefuel cells onto a Diamond Super Dimona motor-glider intime for test flights in 2005. Although this project is lookingfor alternative solutions for commercial aircraft auxiliarypower units (APUs) the resulting technology will inevitablyfeed back into the UAV industry.

Solar power technology is being proven by companies suchas AeroVironment with their Helios and Pathfinder Plusaircraft and nuclear power has even been suggested as asolution for the larger HALE UAVs.

The market will dictate which of the future solutions willeventually win out in each of the UAV categories, but whocurrently supplies the UAV engine market and whatdevelopment activity is taking place?

Europe

Europe has a very successful record in the supply of UAVengines around the world. General Atomics has beenselecting piston engines developed in Austria by theBombardier subsidiary, Rotax Aircraft Engines for manyyears. The Altus UAV, from which the Predator, Gnat and I-Gnat are derived, uses a Rotax 914 air/liquid-cooled,horizontally opposed four-cylinder four-stroke piston engineas does the I-Gnat and RQ/MQ-1Predator. Predator B and itsAltair and Mariner versions however, are equipped with theHoneywell TPE-331-10T turboprop engine. Rotax AircraftEngines has also achieved much success elsewhere and hassupplied its engines to the French Sperwer/Ugglan UAVdeveloped by Sagem of France and in service with theCanadian, Dutch, Swedish, French, Danish and Greekarmies. A Rotax 914 was selected by IAI/Malat for theirHeron MALE UAV, by EADS for the Eagle 1 MALE UAV andby the Science Applications Industrial Corporation (SAIC)for their Vigilante 502 VTOL UAV improved version of the496.

Austria’s neighbour, Germany, has several UAV enginemanufacturers; most notably Hirth-Engines, a unit ofGöbler-Hirth Motoren KG, Limbach Flugmotoren GmbH &Co KG and Rolls-Royce Deutschland. The SAIC Vigilante496 mentioned above is powered by a Hirth F 30horizontally opposed four-cylinder two-stroke pistonengine. The Swiss RUAG Ranger in service with the SwissAir Force and the Finnish Defence Forces has a Hirth F 31 in-line air-cooled two-stroke engine which was specificallydeveloped for the aircraft and a sister engine, the Hirth27006-R05 from the 2700 series was selected for theKamov Ka-137 VTOL multipurpose UAV. In April 2004Göbler-Hirth Motoren KG announced that it had enteredinto an agreement with Orbital of Australia to use its air-assist DI on a new range of two-stroke engines which arebeing designed to operate with heavy fuels. Orbital’s air-assist DI allows spark ignition engines to operate onkerosene-based fuels and a Hirth engine equipped with theOrbital system was displayed at the Australian InternationalAirshow at Avalon in March 2005.

The Bombardier/EADS CL-289 recoverable surveillance UAV,which has been in service with the French and Germanarmies since the early 1990s and has been used verysuccessfully in the Balkans, is powered by the T117 single-

UAV Engines

shaft axial turbojet, designed and manufactured by KHDLuftfahttechnik. The engine, although no longer inproduction, is capable of using JP-4 and JP-8 fuels. BMWRolls-Royce, now Rolls-Royce Deutschland acquired KHD in1990. Another notable German UAV engine manufacturer,Limbach Flugmotoren, based in Königswinter, specialises intwo- and four-stroke piston engines for small pleasureaircraft including ultra-lights. The company is activelypromoting their expertise for UAV applications and the L275E two-stroke engine powered the EADS DCS Foxtactical UAV (in service, but no longer in production) andthe L 550 four-cylinder, two-stroke engine is fitted to theKentron Seeker II reconnaissance, target location andartillery fire correction UAV.

French UAV engine industry is based around Microturbo’sTRI 60 and TRS 18 turbojets. Designed under contract tothe French Government’s Direction des Recherches etMoyens d’Essais, the single shaft turbojet TRI 60 has beenused in subsonic missiles as well as UAVs including targetdrones and is compatible with JP-4/5/8/10 fuels. The IndianLakshya target drone, currently being modified to carryimaging sensor packages for surveillance roles, was fittedwith the TRI-60-5 turbojet. The TRS 18 turbojet engine,originally designed to offer self-launch and climbcapabilities to gliders, has since been adopted by theultralight and UAV industries and powers the Galileo Mirach150 low altitude deep penetration medium-range tacticalUAV. Microturbo better known for its fast jet and missilewas acquired by the French engine manufacturer Snecma in2000. In early 2005 Snecma announced that it was tomerge with Sagem and is expected to trade under the newname Safran.

The United Kingdom boasts one of the most prolificmanufacturers of UAV engines in the world, UAV Engineslimited (UEL), thanks mainly to its association with , whichis a 100% subsidiary of the Israeli UAV manufacturer, ElbitSystems Silver Arrow. Originally known as Norton MotorsLtd, the company was subject to a management buyoutand was renamed Alvis UAV Engines. In 1994 it wasrenamed UAV Engines following its acquisition by the Elbitsubsidiary, Silver Arrow. The company is renowned forproducing Wankel-type engines with exceptionally highpower to weight ratios. Its AR 731 single rotor air-cooledengine has been installed on various target drones andUAVs, most significantly the Silver Arrow Hermes 450,AAI/IAI Pioneer and AAI Shadow 200 and is said to have thehighest power to weight ratio of any rotary engine. Thewater-cooled AR 801 has also been used to power the SilverArrow Hermes 450 as well as the AAI Shadow 600 and amodified version produced by Teledyne Continental Motorsof the US provided the power to the R4E SkyEye built byBAE Systems in the US.

Meggitt Defence Systems of the UK produces the MDS 342Hurricane piston engine originally known as the WAE 342when it was produced by Weslake Aeromarine Engines Ltd.This horizontally-opposed, two-stroke engine has beenwidely used over the years and is currently installed on theUK’s BAE Systems Phoenix battlefield surveillance and target

acquisition UAV as well as the Sagem Crecerelle in use bythe French Army. The company also produces the MDS 520Tempest air-cooled four-cylinder two-stroke engine with allmajor components of new design but with the samemounting points of the MDS 342.

In the mid 1990s the UK Ministry of Defence funded aproject by Bernard Hooper Engineering (BHE) of Shropshire,England, to develop the SPV580 UAV engine in order tomeet future needs for low mass, advanced UAV engines.The stepped piston engine, which comes in both air- andliquid-cooled versions, uses two banks of paired cylindersoffering the advantages of both two- and four-cycleengines and eliminating the disadvantages particularlyproblems associated with lubrication. The SPV580 has alsobeen subjected to research work on the feasibility of usingheavy fuel, notable kerosene JET A-1. Results of this studywere presented at the Institute of Mechanical EngineersConference on UAV propulsion systems in April 2005. TheObserver short-range demonstrator UAV developed byQinetiQ and Cranfield Aerospace Limited uses a BernardHooper 88-H twin-cylinder two-stroke engine which wasalso used on the RAE X-RAE 2 UAV.

Elsewhere in Europe, a company with 19 years experiencein the production of two-stroke piston engines is the Italianfirm Zanzoterra Engines. Its latest model the 498ia opposedtwo-cylinder, two-stroke, boxer, injection engine produces39 HP at 6700 rpm, weighs 18.6 Kg and is specificallydesigned for the UAV market for UAVs such as theAeronautics Aerostar and the ATE Vulture.

Russian-built UAVs are powered by engines designed andmanufactured by the Klimov Corporation, Samara Machine-Building Design Bureau and Soyuz. The Pchela UAVs areinstalled with the Samara P-032 horizontally-opposed, air-cooled two-cylinder two-stroke engine. The single-shaftturbojet UAV engine built by the Klimov Corporation of StPetersburg known as the TR3-117 is used on the Tu-143Reis and Tu-243 Reis-D UAVS and the Tu-141 Strihz UAV ispowered by the Soyuz R-9A-300 non-afterburning axialturbojet, which is a variant of the Tumansky-designed RD-9engine.

Asia and the rest of the world

In Japan, the Yamaha Motor Co designed and makes the24cc, water-cooled, horizontally opposed, 2-cylinder pistonengine for the RMAX Type IIG VTOL UAV, which is the latestin the Yamaha series of what are primarily agriculturalvehicles, but which are being modified to carry sensorpayloads for surveillance capabilities. The company claimsthat because the engine is water-cooled it is particularlyeffective in high altitude areas especially in the hot sun. FujiHeavy Industries has developed a Fuji Robin three-cylinder,water-cooled two-stroke engine for its RPH-2 VTOL UAV.

Propulsion systems for Chinese UAVs are supplied byBeijing University of Aeronautics and Astronautics (BUAA)

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with their WP11 reverse-engineered version of the TeledyneContinental J69-T-41 used to power the Chang Hong high-altitude multi-purpose UAV, which itself is a reverseengineered version of the Teledyne Ryan (NorthropGrumman) 147H (AQM-34N). The Xian ASN-104 and ASN-105B reconnaissance/surveillance UAVs are reported to bepowered by the Xian HS-510 which was originallydeveloped by the South Aero-Engine Company (SAEC) atZhuzhou with the Xian-206 short-range multi-role UAV alsohaving a Xian-built SAEC derived, air-cooled four cylindertwo-stroke piston engine. A two-stroke, air-cooled pistonengine, the 40 F, designed by the Nanjing Research Institutefor Simulation techniques (NRIST) for use on mini UAVs isreported to be developed and is now available. The enginehas a diaphragm carburettor, capacitor-discharged magnetoignition and both manual and electric starting.

North America

The US has a well-established UAV engine manufacturingbase, with well-known global brands like Pratt & Whitneyand the not so high profile companies like Herbrandson andDeltaHawk Diesel Engines.

Pratt & Whitney supplied the JT15D-5C turbofan engine forthe X-47A Pegasus UAV demonstrator aircraft which hassince been incorporated into the US Air Force/Navy/DARPAJoint Unmanned Combat Air Systems (J-UCAS) program.This work has coincided with the US Government initiativeon Integrated High Performance Turbine Engine Technology(IHPTET) which includes the Joint Technology DemonstratorEngine (JTDE) project. As part of the JTDE, P&W wereawarded a 3-year contract in mid-2003 by the US Naval AirSystems Command to develop and demonstrate a broadrange of turbine engine technologies for potential use in USNavy and Air Force UAVs. The US$12.7 m contract willintegrate the advanced technologies into its PW800 engineand will focus on high temperature lightweight materials.This demonstrator will also serve as one of P&W’s baselineconfigurations for the US Government’s Versatile AffordableAdvanced Turbine Engine (VAATE) program which isstarting just as the IHPTET program winds down with thecompletion of the final large military demonstrator enginein June 2004.

Pratt & Whitney also supply the PW2005-55 turboshaftengine for the TR911D demonstrator version of the BellEagle Eye VTOL UAV, the earlier demonstrator, TR911X,having a Rolls-Royce Corporation 250-C20Rturboshaft/turboprop. The Rolls-Royce Corporation’s AE3007H single-stage two-shaft turbofan originally developedby Allison to power airliners and business jets was selectedto power the Northrop Grumman RQ-4A Global Hawk.Another well-known manufacturer of turbofan engines,Williams International, supplied the F112 turbofan which isbeing used on the X-50 Canard Rotor Wing also known asthe Dragonfly.Piston-engines for UAVs produced by the CalifornianHerbrandson Engines Company have been used to power

the ill-fated US Army Lockheed Aquila UAV (Dyad 280B)and the Dyad 290B two-cylinder two-stroke engine isinstalled on the DRS Sentry. According to Herbrandson, thecompany has operated spark-ignition two-stroke engineson JP-5/8 fuels since 1987. Another North Americanpiston-engine manufacturer, originally based in Canada, isQuadra Aerrow which specialises in model aircraft two-stroke, air-cooled engines. The company merged with USEngines Inc in February 2004 to form USQ Aero Inc basedin Pennsylvania in the US. It has retained its UAV enginebusiness line which supplies engines for the BAIAerosystems Exdrone and Dragonfly DP VTOL UAV series ofDP3, DP4-X, and DP5-X used initially in the film industry butnow also equipped with imaging payloads for surveillanceand reconnaissance roles, as well as being trialled as aweapons platform with the Australian company MetalStorm. Live firings of the 40 mm weapon are expected inmid 2005 following the cancellation of the scheduled livefiring in March 2005.

Diesel engine development for UAV applications is takingplace at DeltaHawk Diesel Engines who have partneredwith TRG Helicorp limited of New Zealand to develop adiesel-powered engine based on its DH160V4 for the TRGSnark 3 Unmanned Combat Air Vehicle (UCAV). Flight testsare due in 2005 to test the engine which, according toDeltaHawk’s President Diane Doers will have an estimated30% greater range over a standard gasoline engine.

Sonex Research Inc has successfully applied for a patent forits Sonex Combustion System (SCS) consisting of a startingsystem and modified combustion chamber design forconverting two-stroke gasoline engines for JP-5/8 heavyfuels. This followed a 10-month US$744,246 contractawarded to Sonex by DARPA in late 2002 to develop aheavy fuel conversion process for an existing six-cylinder,spark-ignited, four-stroke gasoline UAV engine using itsSonex Controlled Auto Ignition (SCAI) system and aUS$165,000 DoD contract awarded in 2003 to convert twolightweight, two-stroke, spark-ignited gasoline engines tostart and operate on standard military kerosene-based fuelsbased on its patented SCS system.

Finally, the Southwest Research Institute (SwRI), a not forprofit research and development organisation, wasawarded a 24-month contract to design and develop aheavy fuel UAV engine by the US DoD. The air-cooledengine features a two-stroke IDI combustion process withpositive displacement external scavenging.

Engine suppliers worldwide, like all other organisationsinvolved with the development of UAV systems are havingto adapt existing technologies and develop new ideas tomeet the global demand for UAVs with enhancedefficiencies, longer endurances, lighter material and morecapable systems. These demands will never cease but so farthe industry is developing the technologies and solutions inline with expectations.