New Chinook engine offers advantages for future operations (Studio)

Brought to you in partnership with Honeywell Aerospace

With the US Army’s CH-47 Chinook helicopter expected to remain in service at least until the 2050s, the construction of the new T55-714C helicopter engine is crucial.

Developed by defence company Honeywell Aerospace, the 714C is a modernisation of the earlier T55-714A engine fitted to the US Army’s CH-47 Chinook helicopters and will bring significant performance improvements when introduced.

TJ Pope, senior director of military turboshaft engines for Honeywell Aerospace, told Studio that the first complete T55-714C engine configuration is being built and, following a series of testing and verification phases, will be ready for production in 2024.

‘At the moment, we are constructing our compressor rig testing and lab iterations of engine components. We are also constructing a more capable test cell in our facility to be able to handle the increased horsepower of the engine for production and maintenance and repair and overhaul (MRO) capabilities down the line,’ he said.

Following the completion of lab testing in 2020, the first installation on a Chinook will begin in the autumn of 2021, with further flight testing on Chinooks at Fort Eustis in 2022. 

Development of the 714C is a company-funded effort from Honeywell, which invested in the engine in anticipation of the future needs of the US Army’s Chinook fleet in an era of Great Power Competition and potential conflict with a near-peer adversary. 

Pope explained that the helicopters are estimated to be around until at least the 2050s, during which time the demands on the platform will increase. 

The Chinooks will need to provide more capability for operations at longer ranges in hot and high conditions, in the maritime environment, and for transporting heavier payloads. 

To meet these expectations, the 714C will operate in the 6,000 horsepower class, which is four times the amount of the original T55 engine installed on the first Chinook helicopters when they entered US service back in 1961 and is 22% more than that the current 714A engine. 

It can attain a high horsepower through the development of a new compressor module that was redesigned to allow increased power output and improve fuel consumption. This new component is at the heart of the 714C upgrade and allows the engines to run at a higher cycle pressure, thus providing a more efficient output. 

The improvements in the compressor module design came from Honeywell’s HTF 7000 turbofan development in the commercial sector.

Pope said that Honeywell had leveraged the lessons from this work for the T55. The compressor has been built with more robust materials to achieve the high cycle pressures available and a 25% improvement in reliability and 40% longer compressor life cycle. 

The 714C will increase the lift capacity of the Chinook to 21,000lb while adding only a negligible increase in weight and maintaining the existing size of the engine.

According to Pope, compared to the 714A, the dimensions of the ‘C’ version have changed by just half an inch and by maintaining the form and structure of the ‘A’ version, it doesn’t require structural changes to the CH-47 aircraft. 

‘That was a very high priority goal of these exercises, to pack more power and more efficiency into the same footprint to minimise the customer impact. It doesn’t require new plumbing; it uses the existing aircraft engine cell and can be a drop-in upgrade,’ he explained. 

The only modification is a new wire to the cockpit for a pilot indicator because of additional anti-ice functionality that is being included. Furthermore, the hydromechanical assembly is being moved from the bottom of the engine to sit on the top to facilitate easier maintenance.

As yet, there is no US Army programme of record for the purchase of new engines for the Chinook fleet, but there is a need for enhanced capabilities. With the introduction of the T55-714A still underway, Pope said the ‘predominant source’ of 714Cs in the short-term would be modifications to convert the ‘A’ to the ‘C’ engine. 

In the long-term, Pope expects the production of new 714C engines should Boeing select it for its new CH-47 Chinook Block II variants in the next two years.

Further into the future, Honeywell is looking to develop a 7,000 horsepower-class variant of the T55 engine. Pope said it would have a common compressor with the 714C, so the focus will move to ‘build a new centreline’ around that by enhancing components in the other half of the engine by introducing technological enhancements with ‘new materials and design methodologies’.

Meanwhile, Honeywell has established a new MRO facility in Phoenix, co-locating it with its existing T55 production line. Pope explained that this was necessary to ‘reduce operational strain’ and meet additional demands from the US Army to support the Chinook, which has experienced an increase in operational tempo over recent years.

He added that co-locating the MRO and production facilities offered ‘synergies’ between the two parts of the business, allowing for the rapid and seamless transfer of staff from one to the other to meet any spike in demand. 

‘It’s the same engine and the same skill sets. And so those folks can go back and forth between those two facilities so that we can optimise operationally how we manage both our front end on the production side.’