notajet1In the PurePower engine, the intake fan is separated from the turbine by a gearbox so both can run at optimal speeds. (Handout/ Bombardier)

When politicians and activists talk about Porter Airlines’ plan to fly “jets” out of Toronto’s downtown airport, they show a fundamental misunderstanding of the technology on Bombardier Inc.’s CSeries aircraft, according to the executive who developed the plane’s engine.

An ultra-high-bypass-ratio geared turbofan, to be exact. Nearly 30 years in the making, the technology is not yet available on commercial planes but will be very shortly on both the Airbus A320neo and Bombardier’s CSeries.

The difference between Pratt & Whitney’s PurePower engine, as it’s called, and a typical jet engine is “fundamental,” according to Webb.

In the PurePower engine, the intake fan is separated from the turbine by a gearbox so both can run at optimal speeds. (In this case, the fan moves at about one-third the speed of the turbine. In a conventional jet, the fan and turbine are attached and move at the same speed.)

Because most of the thrust generated by a turbofan comes from the slow-moving air passing through the extra-large fan, less fuel is burned and less noise is generated compared with a typical jet engine.

As a result, noise is reduced by 50 to 75 per cent compared with existing engines and fuel burn is cut by up to 16 per cent.

“I think that as people start to understand this and see the difference in this class of aircraft that heretofore was not in existence, it’ll begin to change their perspectives,” said Webb, who was the chief engineer on the program and has worked with Bombardier on the CSeries since Day 1.

In fact, Webb said Porter’s existing Q400 turboprop is actually louder than the CSeries, in the sense that it makes a lower-frequency noise and can be heard at a greater distance. Bombardier confirmed recently that the CSeries is “the quietest in-production commercial jet in its class.”

The CSeries’ engine noise has been central to the debate around whether Porter should be allowed to fly the aircraft out of the Billy Bishop Toronto City Airport, which is located on an island just south of the city’s heavily populated downtown waterfront.

Earlier this month, Transport Minister Marc Garneau tweeted that Ottawa will not re-open the tripartite agreement that governs the airport, nixing Porter’s plan to add the CSeries to its fleet. Written in 1983, the tripartite agreement bans jets and sets a strict noise limit on the airport’s operations. Although the CS100 — the version of the plane that Porter wants to fly — complies with the noise decibel ceiling, it won’t be allowed to fly because of Garneau’s interpretation of the agreement.

“I guess the question I have about that recent government rejection from the minister of transport is, did he actually hear the aircraft?” Webb asked.

Garneau did not immediately reply to a request for comment, but spokesman Jean Proulx said in an email last week that he’s simply sticking to the Liberals’ election promise. “The Liberal Party of Canada made a promise during the election not to reopen the tripartite agreement and we will keep that promise,” Proulx wrote. “The existing tripartite agreement strikes the right balance between commercial and residential interests, environmental and cultural challenges, including the evolution of the waterfront.”

Pending the approval of its plan, Porter had placed a conditional order for 12 CS100 aircraft with options for 18 more, a deal worth more than US$2 billion at list prices if all options were exercised. That order will likely now be cancelled.

Porter wasn’t the only airline planning to take advantage of the PurePower engine’s quietness to fly out of an urban airport, however. The CSeries’ launch operator, Swiss International Air Lines, is based at Zurich Airport, which has a strict curfew that bans flights between 11:30pm and 6am.

And U.K.-based startup Odyssey Airlines, which has a firm order for 10 CS100 aircraft, plans to begin flying out of London City Airport next year.

“It’s a great aircraft for a highly populated, dense area,” Webb said.

Kristine Owram, National Post