Bombardier says the final results of a five-year wind-tunnel test program have validated the CSeries airliner's aerodynamic design and support the manufacturer's predictions that...

The final results of a five-year wind-tunnel test program have provided further validation of the Bombardier CSeries airliner’s aerodynamic design, according to Bombardier Aerospace.

Bombardier says the results from the three-phase wind-tunnel test program also support the company’s design predictions that the CSeries family, optimized specifically for the growing 100-to-149-seat market, will deliver a step-change in fuel efficiency.

Wind-tunnel testing has also contributed to allowing Bombardier to achieve optimal integration of Pratt & Whitney’s ultra-high-bypass ratio Pratt & Whitney PurePower PW1500G engine with the CSeries airframe, Bombardier says. The PW1500G is a member of the new Pratt & Whitney PurePower PW1000G geared-turbofanengine family, which will also power the Airbus A320neo family, the Mitsubishi MRJ and the Irkut MS-21.

This photograph shows a Bombardier CSeries wind-tunnel model undergoing high-speed tests at a facility in Germany

The PW1500G will offer a bypass ratio of 12 to 1 – that is, 12 times as much cool air will be pushed back round the outside of the engine by the fan to produce thrust as the amount of air entering the engine’s core to be compressed and combusted to drive the turbine stages, which drive the fan. The PW1500G’s 12:1 bypass ratio is believed to be the highest yet achieved by any commercial turbofan engine.

Begun more than five years ago, during the early stages of the conceptual-design phase for the CSeries family, the wind-tunnel test program progressed through the aircraft’s subsequent definition and detailed-design phases.

Validation of the CSeries aircraft’s aerodynamic design included extensive use of state-of-the-art computational fluid dynamics (CFD) analysis. The CFD techniques were made possible through the use of contemporary super-computers that Bombardier says are significantly more capable – and 100,000 times faster – than computers available when the aircraft currently serving the 100- to 149-seat market were designed.

The CFD tools permitted the minimization of interference drag on the airfame and engines and also facilitated the design of the engine nacelle and thrust reverser, according to Bombardier Aerospace.

To simulate actual flying conditions, Bombardier conducted its CSeries wind tunnel tests with more than 20 sophisticated scale models over more than 4,500 testing hours at facilities in Canada, France, Germany, the Netherlands, the United Kingdom and the United States.

“Simulated conditions during the wind tunnel tests closely correlate to real world flying conditions and the resulting data were used to improve and validate final CSeries aircraft design and systems,” says David Tidd, vice president, CSeries integrated product development for Bombardier Commercial Aircraft.

The Bombardier CS100 is the smaller of the two Bombardier CSeries versions announced to date and will typically seat from 110 to 124 passengers

“This latest achievement for the CSeries aircraft represents the most extensive and complex wind tunnel testing that Bombardier has ever conducted; it marks another key advance in the jetliner’s development,” adds Tidd.

The scale models of CSeries jetliners used in the testing were equipped with precise instrumentation to measure air flow, including as many as 700 pressure-sensitive ports over the wings, fuselage and tail. The models included moving parts, such as wing flaps and leading edge slats, which could be repositioned to reflect actual flying events.

Some models were equipped with miniature air-driven turbine engines to gauge the interference between the engine airflow and the aircraft’s wings. The largest of the models, at 13.7 per cent scale, had a wingspan of approximately 4.5 metres (15 feet).

Using the scale models and the environmental conditions possible in the wind tunnels, Bombardier engineers were able to simulate the aerodynamics of the CSeries aircraft in various flight scenarios such as landing, take-off and cruising at high altitudes.

Bombardier estimates that, compared with existing 100-to-149-seat jets, the CSeries family will offer a 15 per cent cash operating cost advantage and a 20 per cent fuel-burn advantage, based on a 500-nautical-mile North American operating environment.

The manufacturer says the CSeries will also offer greatly reduced noise and emissions over existing jets; and superior operational flexibility, exceptional airfield performance and a range of 2,950 nautical miles (5,463 kilometers). It will also provide passengers with widebody-style seating in a single-aisle aircraft.

Bombardier has booked firm orders for a total of 133 CSeries jetliners, including 61 Bombardier CS100s (typically offering 110 to 124 seats) and 72 Bombardier CS300s (which will typically offer 125 to 149 seats). The CSeries program has also booked options and purchase rights for an additional 129 aircraft.