Who Says a Jet Can't Be Cheap?

[cluttonfred]

Does anyone know if anything ever came of these efforts by Gerry Merrill and others to produce a turbofan optimized for low speed, low altitude and low cost? Luc van Bavel, you must know more!

http://www.airspacemag.com/flight-today/tiny_turbines.html

Cheers,

Matthew

 

[Machdiamond]

That was a good article, I think I missed it when it was published. I don't know the status of that project.
There is a similar aircraft available on the market now: http://www.sonexaircraft.com/subsonex/
-Luc

 

[cluttonfred]

Thanks, Luc. For me the most interesting bit in the article was the concept of optimizing the performance of a small turbofan for speed and altitudes more usually associated with pistons and props.

Conventional wisdom holds that jet engines burn too much fuel at low altitudes to be suitable for light aircraft. Jets, it's said, are efficient only above 30,000 feet or so, where light airplanes fear to tread. "That's bullshit," says Merrill flatly. Sure, every jet flying today gulps prodigious amounts of fuel when going low and slow. But that's because they were all designed to run high and fast. The secret, Merrill says, is to simply optimize the configuration of an engine's turbines, compressors, and fan for, say, 250 mph at 15,000 feet instead of 500 mph at 40,000 feet. "It's not rocket science," he says. "My engine technology and materials are basically 1960s. The breakthrough is conceptual."

It's a compelling argument, but it makes you wonder, if that's all there is to it, why hasn't anyone else done just that?

 

[Machdiamond]

Merrill is correct. Above 270-300 knots and contrary to popular wisdom, a turbofan powered aircraft will burn less fuel than a similarly performing turboprop. I am talking about real flight test data, this is not a hypothesis. The turbofan acquisition and maintenance cost will also tend to be lower than the turboprop, by a factor of two in some cases.

So yeah, that's (almost) all there is to it. Why this marketspace hasn't been addressed yet is a very long story with its share of twists, blood, tears and nutcases.

-Luc