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Engine In A Box: Extending Operational Capabilities

In light of rising fuel prices, Jim Kroeger, director of engineering for propulsion at Honeywell Aerospace, examines the role of the powerplant in minimising operational costs.

As fuel costs spiral, aircraft operators continue to feel the pinch. UBS Investment Research analysts recently calculated that business jet flight activity is down 11 per cent globally because of fuel costs while the NBAA estimates that up to 25 per cent of a turbine operator’s costs is fuel. And, at a time when many of the world’s largest defence departments are cutting spending by as much as 50 per cent, the challenge of maintaining air-based operations remains prominent in the military sector too.

To combat the problem of spiralling fuel costs, original equipment manufacturers (OEMs) and their component suppliers have focused on incremental advances through technology right across the airframe, in a bid to improve efficiency and extend operational capabilities. The search for the “holy grail” of performance and efficiency has become the primary competitive battleground among most suppliers.

But nowhere is this battle raging stronger than in the powerplant market — a component that has a huge impact on the performance, efficiency, and operational flexibility of an aircraft. Whether it’s a single-prop light aircraft or a heavy lift helicopter, the objective of the operator is the same – to do more with less or, in other words, extend operational capabilities through the lowest possible operational cost and longest effective lifecycle.

For engine manufacturers, the first place to focus attention is on fuel consumption. The objective is to get the specific fuel consumption (SFC) as low as possible without sacrificing on required levels of thrust. This was one of Honeywell’s main objectives when we developed the CTS800 engine for the US Military’s RAH-66 Comanche attack helicopter. The customer needed a high performance helicopter but one that could offer significant fuel efficiency gains over the existing fleet — as a result the CTS800 efficient engine was designed in collaboration with Rolls-Royce under the Light Helicopter Turbine Engine Company (LHTEC) partnership to offer the lowest SFC for a turboshaft engine in its size class, consuming only 0.46 lbs of fuel/ lbs of power. Since 2004, the CTS800 has found use in other applications including the AgustaWestland AW159 Wildcat, due to enter service with the British Army and Royal Navy from 2014.

These fuel savings can come from a number of areas within the engine architecture. At Honeywell, we have been looking at the use of forward-swept lightweight blisks, developed with NASA, to increase bypass ratios without increasing engine size. We’ve also been experimenting with various thermal barrier coatings on our HTF-series of business jet engines to enable operation at higher temperatures without significant additional weight gain.

It’s not just fuel consumption where engine manufacturers can innovate out a proportion of the operational costs, however. One of the other major cost centres for both civil and military operators is unplanned engine maintenance. The reliability of an engine is clearly a vital purchasing influencer and the costs associated with unplanned grounding due to component failure can be significant.

Traditionally, the objective has always been to make maintenance costs as predictable as possible by scheduling servicing at a set number of flight hours. The objective of engine manufacturers is typically to extend this service interval as far as possible — in the case of our HTF7000-series engines on a fixed interval maintenance programme, operators must inspect the hot section at 3,500h and the cold section at 7,000h, and we expect to increase those numbers several hundred hours further in the next couple of years.

The HTF7350, announced at this year’s EBACE (European Business Aviation Convention & Exhibition), is the latest addition to our HTF-series and will power Bombardier’s new super midsize business jet, the Challenger 350. It features Honeywell’s Single Annular Combustor for Emissions Reduction (SABER) combustor, which significantly reduces NOx and unburned hydrocarbon emissions. With SABER, NOx emissions are 25 per cent lower than International Civil Aviation Organisation (ICAO) requirements. Improvements in fuel delivery and the engine control unit (ECU) deliver 7,323 pounds of thrust per engine, enabling the Challenger 350 aircraft to perform a direct climb to 43,000ft. The HTF-series has now clocked over 1.5 million flight hours with a dispatch reliability of 99.9 per cent.

More and more customers are opting for an “on-condition” maintenance model — that is, the replacement and servicing of engines as required. This is being achieved on Honeywell’s HTF7000 series of engines through the use of designs that are easier and faster to service, and by the use of advanced digital imaging equipment. Additionally, advances in on-board health monitoring systems such as those on Honeywell’s F124/F125 turbofan engines are in use today on a number of military aircraft.

Proactive prevention of failure can save operators a substantial amount of operating cash over the lifecycle of the engine and crucially reduce unplanned grounding — an issue that our military customers in particular strive to avoid. To tackle this problem, many operators are now taking health monitoring beyond only the powerplant. Our Health Usage Monitoring System (HUMS), for example, was developed to maximise the predictability of helicopter maintenance beyond just the engine. HUMS provides critical component diagnosis and prognosis at over 35 points along the drive-train, from engine to blades. A study on the AH-64 Apache helicopter has shown that HUMS can reduce mission aborts by 30 per cent, maintenance test flights by 20 per cent and deliver an up to 10 per cent reduction in scheduled maintenance.

A grounded aircraft is 100 per cent cost with no return and consequently reduced maintenance time is extremely important for our military and business aviation propulsion customers. In order to get an aircraft back in the air as quickly as possible, most modern engines feature a modular design, allowing easy access to their components on the tarmac. In fact, line replaceable units (LRUs) in most Honeywell turbofan engines can be replaced in minutes rather than hours using only common engineer hand tools.

As fuel prices continue to set the tone for the aviation industry, the role of the powerplant in minimising operational costs is becoming all the more pivotal. At the same time, this has to come without sacrificing performance — efficiency aside, our HTF7250G engines still need to be able to take a Gulfstream G280 from runway to FL410 in less than 20 minutes, and enable it to cruise at Mach .80 for over 3,600 nautical miles. There is no trade-off and consequently the need to do more with less is not only defining the business model of fleet operators around the world — it’s shaping an exciting new era of engine development for the aviation industry.

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