The abandoned Cessna Citation Hemisphere

Summary

The Cessna Citation Hemisphere project was stopped in 2018 due to engine performance problems at Safran Aircraft Engines.
Safran Silvercrest engines showed reduced performance during altitude testing; alternative engines are being considered.
Hemisphere was intended to be the largest aircraft in the Citation family, with a cruise speed of Mach 0.9, and revised engine options were also considered.

Cessna Citation Hemisphere was a business jet design announced in November 2015 by Cessna, a Textron Aviation company, as a new member of its Citation family. Although it was scheduled to enter service in 2019, the program was canceled in April 2018 due to several delays, notably in the development of the engines by French manufacturer Safran Aircraft Engines.

Cessna Citation Hemisphere

Proposed general features

capacity: 12 passengers
Hull diameter: 102 inches (260 cm)
power plant: 2 × Safran Silvercrest turbofans, 12,000 lbf (53 kN) thrust each

The Cessna Citation Hemisphere was introduced at the 2015 National Business Aviation Association (NBAA) convention and offers the widest cabin in its class. The Hemisphere was designed to work alongside the Citation Longitude and is expected to offer significantly more in terms of capacity and passenger comfort.

As Forbes reported, Textron Aviation has said it has put its flagship business jet program, Citation Hemisphere, on hold due to concerns about Safran’s Silvercrest engines, which the engine maker said lacked the power and performance needed to operate the twin-engine fixed-wing aircraft.

The two partners worked together for several months to conduct extensive testing (on test engines) to determine performance and integrate it into the planned Citation airframe. According to Brad Thress, Senior Vice President of Engineering at Textron Aviation, as reported by Safran,

“We worked closely with Safran to understand the development phases of the Silvercrest engine. Throughout our review, we remained confident that the Silvercrest was the best choice for the hemisphere, and we are pleased with Safran’s continued commitment to delivering it on time and on target.”

textron_citation_hemisphere_mockup_thumbnail_bjt

Photo: Textron Aviation

The Silvercrest engine showed reduced performance during altitude testing due to pressure losses in the high pressure (HP) compressor. The reduced performance was associated with cruise attitudes due to its axial-centrifugal architecture.

While Safran worked to resolve the engine issues, Textron considered an alternative option for the engines. A competing engine called the Pratt & Whitney Canada PW800 was considered. The PW800 series offers higher performance but could be adapted to the requirements of the Citation Hemisphere.

Cessna Citation Hemisphere proposed power plants	Safran Silvercrest turbofans	Pratt & Whitney Canada PW800 turbofans
Type	Double coil	Double coil
length	74 inches (190 cm)	105.8 inches (269 cm)
diameter	42.5 (108cm)	50 inches (130 cm)
compressor	4 low pressure stages, 4 high pressure blisks + 1 centrifugal stage	24-blade, one-piece single-stage fan, 2-stage LP and 8-stage HP compressor
turbine	1 high pressure, 4 low pressure stages	2-stage HP and 5-stage LP turbine LP: max. 6,240 rpm, HP: max. 24,043 rpm
Maximum thrust	53 kN (12,000 lbf)	68.63 kN (15,429 lbf)
Bypass ratio	5.9:1	5.5:1
Thrust-to-weight ratio	5	4.92

Which is the most commonly flown Cessna Citation variant?

Before this year, the Citation Excel aircraft series was the most frequently flown business jet in the world for over 15 years.

What could the Citation Hemispheres look like?

The Cessna Citation family is known for its mid-size jets designed for the 8-12 passenger market. The largest jet in the series is the Citation Longitude, which also has a seating capacity of 8-12 passengers. The existing Citation Longitude jets are powered by two Honeywell HTF7700L turbofan engines, each producing approximately 7,600 lbf (34.1 kN).

Photo: Textron Aviation

Comparing the desired engine power (2x 12,000 lbf/53 kN) for the proposed Citation Hemisphere, the jet could have been the largest business jet in the Citation family. Although the stated seating capacity was 12, it could have offered plenty of space for comfortable, luxurious seats and generous storage space.

Operational capabilities

Proposed features

Travel speed: 516 knots (594 miles per hour, 956 km/h) Mach 0.9
Range: 4,500 NM (5,200 miles, 8,300 km)
Cabin height: 5,000 feet (1,500 m)

Comparing the Citation Hemisphere’s proposed cruise speed to that of the existing Longitude, it is significantly higher. The Citation Longitude has a maximum operating speed of Mach 0.84 (483 knots, 556 m/h, 895 km/h). The Hemisphere’s cruise speed could be as high as Mach 0.9 (516 knots, 594 m/h, 956 km/h), which is equivalent to Bombardier’s large business jets, including the Global 6000 and 7500.

A Bombardier Global 7500 flies over Dubai.

Bombardier Global 7500 vs. Gulfstream G700: Which aircraft is better?

The competition between these two powerful competitors is fierce.

Not the only one affected by the Silvercrest engines

The Citation Hemisphere is not the aircraft affected by the lack of performance and compatibility of the engines manufactured by Safran. French aircraft manufacturer Dassault Aviation canceled its Falcon 5X program because of the Silvercrest engines. However, the company relaunched the design as the Falcon 6X with PW812D engines from Pratt & Whitney Canada.

Photo: Dassault Aviation

Notably, Textron Aviation has put the Citation Hemisphere program on hold rather than canceling it entirely. This means the company can rework the existing engine and aircraft combination and also consider other engines for the design. The company can also rework the existing design with a different set of engines.