Despite Few New Aircraft Types, Business Aviation Propulsion Booms

With only a few notable exceptions, the development of all-new business aviation aircraft has plateaued in recent years as the major manufacturers focus on satisfying solid order backlogs with well-honed models and developing updated derivatives to fill out product ranges.

But behind the scenes, the supporting propulsion providers, including a new series of ambitious startups, are busier than ever. Big industry players like GE Aerospace, Honeywell, Pratt & Whitney and Rolls-Royce are in ramp-up mode on major platforms, while a set of innovative newcomers are fighting to penetrate the lower echelons of the business and general aviation sector with a variety of alternative, more sustainable propulsion systems.

GE Aerospace is expanding production of Passport engines to support Bombardier as the Canadian manufacturer assembles the initial batch of ultra-long-range Global 8000 production models. Due to enter service later this year, the Global 8000 will feature a range of 8,000 nm (9,200 mi.) at a long-range cruise speed of Mach 0.85, allowing it to connect city pairs such as London-Perth, Australia, and Singapore-
Los Angeles.

Although mechanically identical to the Passport variant powering the Global 7500 sister model since 2018, the engine incorporates software changes to the full-authority digital engine control system, which includes a throttle push to enable cruise speeds up to Mach 0.94. The same change will also be available via a supplemental type certificate on the Global 7500.

GE, meanwhile, received in February the long-awaited FAA certification of its clean-sheet 1,300-shp Catalyst turboprop, which powers Textron Aviation’s Beechcraft Denali. Launched in 2015 to compete with Pratt & Whitney Canada’s ubiquitous PT6, the path to meet more modern requirements for FAR Part 33 regulatory approval has been tougher and more rigorous than expected. Certification has involved an extensive effort covering more than 8,000 test hours, 23 engines and over 190 component tests.

The Catalyst, which is the first all-new centerline turboprop to be developed in the 21^st century, is expected to enter service on the Denali utility aircraft in 2026.

In other sectors of GE’s business jet portfolio, the engine-maker last year marked the 20^th anniversary of its HF120 joint venture with Honda for the HA-420 HondaJet. Engine production continues for the very light jet, of which over 250 aircraft are in service. However, for its follow-on light jet—the HondaJet Echelon—Honda Aircraft has selected the Williams International FJ44-4C turbofan.

Assembly of the first new Echelon aircraft, which will seat up to 10, is underway at Honda’s manufacturing facility in Greensboro, North Carolina. Launched in 2023, the larger cabin jet is due to enter service in 2028.

Despite the close links between GE Aerospace and Honda, the selection of the Williams engine for the Echelon was not wholly unexpected. The secretive Michigan-based engine maker’s popular FJ33/FJ44 engine family already powers the bulk of the existing light business jet aircraft in the sector including the Cessna Citation CJ family, the Cirrus Vision Jet, Beechcraft Premier I and the Pilatus PC-24.

Honeywell also continues to grow its presence in the business jet power sector and is developing a suite of advanced high-pressure core and low-pressure spool technologies to form the basis for a next-generation derivative of its best-selling HTF7000 family for the 2030s. In the meantime, it expects to more than double the fleet of HTF7000 engines over the next decade as the super-midsize/midsize business jet sector continues to thrive.

Having passed the 10 million flight hour milestone in 2024, the HTF7000 fleet continues to accumulate almost 2,000 flight hours per day with around 3,300 engines now powering aircraft ranging from the Bombardier Challenger 3500/350 and Gulfstream G280 to the Cessna Citation Longitude and Embraer Praetor 500/600.

Originally envisaging an eventual production run close to 8,000 engines over the life of the program, Honeywell may see these numbers increase under the terms of a strategic agreement announced in December 2024 with Bombardier covering the supply of avionics, propulsion and satellite communications technologies. Although not specified, the agreement is believed to include development of an HTF7000 variant for a long-rumored Challenger 650 replacement­­—more details of which may emerge later this year.

For its next-generation development work, Honeywell has focused on engine efficiency improvements and testing with sustainable aviation fuels (SAF) through its own internal R&D work, as well as through the U.S. FAA’s long-running Continuous Lower Energy, Emissions and Noise (Cleen) program.

Having evaluated a compact combustor, an advanced turbine blade outer air seal and high-pressure (HP) compressor under Cleen, Honeywell is continuing its HP core work, but under the latest phase of the program is adding new project areas covering studies of a compact high-work, high-lift, low-pressure (LP) turbine and a highly efficient fan module.

Pratt & Whitney also continues to bolster its presence in the longer-range business jet market with expanded production of the PW800. The engine continues in production to support Gulfstream Aerospace’s G500/G600 large-cabin business jets, deliveries of which passed the 300^th milestone in late 2024. Based on the same core as the company’s PW1000 geared turbofan family, the PW812D variant is also due to enter service later this year on Dassault’s new Falcon 6X.

Pratt & Whitney also expects to step up assembly of the PW800 through this year in anticipation of new production for the smaller Gulfstream G400, which made its first flight in August 2024. Pratt is providing the PW812GA variant, which received its type certification from Transport Canada Civil Aviation in September 2022. The timetable for certification of the G400, meanwhile, remains uncertain, though currently seems likely to be targeted toward the end of this year or early in 2026.

The latest variant of Pratt’s popular PW500 series, the PW545D, is set to debut later this year on Textron Aviation’s Citation Ascend business jet with certification of the midsize aircraft expected in the coming months. The engine, which received Transport Canada certification in May 2024, has powered the development aircraft for more than 200 flights and 600 flight hours. The Ascend was announced in May 2023 at the European Business Aviation Association Conference and Exhibition. Around 4,700 PW500-series engines are in service powering a range of Cessna Citation and Embraer jets.

For Rolls-Royce, the near-term focus is on the Pearl 10X, initial deliveries of which have been completed to Dassault for installation on the prototype Falcon 10X ultra-long-range business jet. Flight tests of the engine, which is based on Rolls-Royce’s Advance2 high-pressure demonstrator core, were completed on the company’s Boeing 747-200 flying testbed in October, following a campaign that logged 2,300 hr. at speeds up to 0.9 Mach and altitude up to 45,000 ft.

Selected by Dassault in 2021, the Pearl 10X made its first run in 2022 and is due to enter service on the new aircraft in late 2027. Featuring a blisked titanium fan and four-stage low-pressure turbine, the engine’s high-pressure compressor incorporates six stages of titanium blisks while the two-stage turbine is shroudless. Additive layer-manufactured tiles are also incorporated into the engine’s low-emissions combustor. To date, Rolls has built three ground test and certification engines in the program, as well as the two flight-test units, both of which have been refurbished for the upcoming Falcon 10X flight-test program.

Rolls-Royce is also stepping up production of the Pearl 700, which received FAA approval (as the BR700-730) for the Gulfstream G700 and G800 ultra-long range business aircraft in September 2023. Developed like the Pearl 10X at the Rolls-Royce Center of Excellence for Business Aviation Engines in Dahlewitz, Germany, the Pearl 700 also incorporates the Advance2 engine core with a new low-pressure system.

First deliveries of the Pearl 700-powered Gulfstream G700 began to Qatar Executive in April 2024, while deliveries of the initial G800 are expected to begin imminently following FAA and EASA certification this April. The G800 replaces the BR725-powered G650, production of which ended in February 2024 with the completion of the 598^th aircraft. Rolls-Royce marked the delivery of the 1,000^th BR725 to Gulfstream for the G650 production line in September 2022.

Supersonic and Startups

As interest in long-range, higher-speed business jets show no sign of slacking, one potential outrider seeking a possible role in the sector is Boom Supersonic­—a Colorado-based startup that is developing the Overture supersonic airliner and the Symphony engine with which to power it.

The Boom-led engine partnership includes Standard Aero, Florida Turbine Technologies (FTT), a unit of Kratos, and an additive manufacturer—Colibrium Additive—owned by GE Aerospace. It is targeting assembly of the first core this summer following completion of the final design review in early April.

Targeting an initial thrust level of around 35,000 lb.—though this is widely expected to increase—the two-spool, 3:1 medium-bypass turbofan engine will be equipped with a single-stage 72-in.-dia. fan and be optimized for prolonged supersonic operation with an air-cooled, single-stage high-pressure turbine and three-stage low-pressure turbine. The Symphony’s compressor will be made up of a six-stage high-pressure unit and a three-stage low-pressure section, while the engine’s mixed compression supersonic inlet, diffuser and exhaust design is devised to meet Chapter 14 noise levels.

Although aimed principally at Overture, a Mach 1.7 88-seat airlier, Boom founder and CEO Blake Scholl says the engine is attracting interest from unidentified parties keen to see a supersonic business jet developed. The overall characteristics of the engine’s operating cycle may well suit some potential high-speed business jet concepts, as it is designed with sufficient thrust to accelerate the Overture through the sound barrier and cruise supersonically without afterburners. The engine’s design optimizes the core for top-of-climb performance in supercruise, while the fan is optimized for noise reduction during takeoff.

Startups seeking to bring alternative and sustainable forms of propulsion to aviation have taken something of a beating financially in recent months, with the list of failed or insolvent companies growing as they struggle to secure additional funding.

As a result, the future of electric and hydrogen propulsion is in the hands of a smaller group of startups that are better positioned, financially and technically, to succeed. And, despite challenges and delays, those companies remain on a trajectory to introduce new forms of propulsion later this decade.

The ubiquitous Cessna Caravan single-turboprop utility aircraft remains the favored launch platform for battery-electric, hybrid-electric and hydrogen-electric propulsion retrofits. But interest is expanding to the Beechcraft King Air turboprop twin and light helicopters such as the Robinson R44 and R66.

Spanish/Australian startup Dovetail Electric Aviation plans to fly its all-electric Caravan late this year. The company has developed its own DovePower electric propulsion system (EPS) and DovePack energy storage system for Part 23 regional aircraft, aiming for service entry in 2027.

Other developers appear to be converging on 2027 as a likely date for market introduction. These include electric propulsion pioneer MagniX, which is working to certify its magni650 EPS with the FAA and electrify the De Havilland Canada DHC-2 Beaver with Canada’s Harbour Air Seaplanes by 2027. U.S. regional Surf Air Mobility has pushed its plans for electric Caravan conversions back to 2027.

A similar picture is emerging for hybrid- and hydrogen-electric conversions as startups work to certify their systems. Ampaire with its AMP-H570 hybrid powertrain and ZeroAvia with the ZA600 hydrogen fuel-cell powertrain are aiming for certification on the Caravan by end-2026, but that could slip into 2027.

Dovetail plans to fly a hydrogen-electric powerplant on the King Air in 2026, and the popular twin-turboprop is also a target for conversion to hybrid-electric power by Ampaire. Australian startup Stralis Aircraft, meanwhile, plans to fly a Beech Bonanza hydrogen-electric testbed in 2026 as a step toward certifying a retrofit for the Beech 1900D regional turboprop by the end of the decade.

At the same time, the helicopter market is drawing increased attention. MagniX has launched an electric engine family specifically aimed at light helicopters such as the Robinson R44 as well as light fixed-wing aircraft. Helistorm is a high-speed EPS, operating at 6,000-7,000 rpm and producing 330 kW peak power.

As with the Caravan, the popularity of Robinson’s R44 and R66 makes them prime targets for propulsion retrofits. Unither Bioelectronique on March 27 made the historic first piloted flight of a hydrogen-electric-powered helicopter, a modified R44, and is working toward certification of a liquid-hydrogen fuel-cell-powered R66 in 2028, for zero-emission transport of organs for human transplants.

Under a U.S. Army small-business contract, startup Hydroplane is working with Enstrom Helicopter to power a light helicopter with a larger version of a hydrogen fuel-cell powertrain under development to reengine general-aviation aircraft, beginning with a Piper Cherokee testbed now in ground testing.

As for clean-sheet programs, they tend to be longer, and the certification challenges greater. Ranging from all-electric training aircraft through nine-seat electric seaplanes to hydrogen-electric business jets, these new design efforts are tending to aim for certification and delivery by the end of the decade. For these new aircraft projects, there is still time to make adjustments as understanding of the technology and certification hurdles matures. An example is French startup Beyond Aero’s redesign of the BYA-1 hydrogen-electric business aircraft to improve safety and performance.

The 700-bar gaseous hydrogen tanks have been moved from the lower fuselage to the wing tips and fuselage sides. All six fuel tanks are now located above the wing spars, so the structure protects the tanks in case the aircraft lands with landing gear up.

Fuel cells are more efficient than turbine engines, but at 59% efficiency, generating 1 megawatt of power requires the removal of 1 megawatt of waste heat. This requires large radiators. Beyond Aero had doubled the power of the BYA-1’s fuel cells to 2.4 megawatts to eliminate heavy booster batteries, but the fuselage-encircling air intake generated too much drag. The redesign uses airflow from the ducted electric propulsors to cool the fuel cells.

Beyond Aero’s redesign is an example of the fluid nature of the alternative propulsion. With battery performance improving at a lower rate than projected five years ago, more startups are looking at hybrid- and hydrogen-electric propulsion for longer ranges.

But the simplicity and efficiency of battery-only powertrains continue to have appeal for smaller aircraft flying shorter ranges and, across the industry, it looks likely that all three forms of more sustainable propulsion will be certified and enter service this decade.