[itsmeduncan]

I know this article is focused on noise, but the most important part about this engine is the efficiency. The fuel savings alone from having the high pressure section running at peak RPM in any situation is incredible. Billions and billions of dollars in fuel savings for a modern fleet.

Think of it as an orbital reduction gear more than a transmission that allows two different sections of the same axel to spin at differen speeds.

Checkout fuel burn vs. other engines. [1] The maintenance cost ratios across an entire fleet versus the fuel savings make it an absolute no brainer for regional fleets.

Source: My father a DER at MTU Aero Engines who developed the geared turbofan with Pratt & Whitney. DERs develop and sign off repairs in accordance with FAA regulations. He was also certified is EASA repairs.

1- http://en.m.wikipedia.org/wiki/Pratt_&_Whitney_PW1000G

Edit: Double the

[unwind]

In this context, I think "DER" means Designated Engineering Representative (http://www.faa.gov/other_visit/aviation_industry/designees_d...). I had no idea, so I had to look it up.

[itsmeduncan]

That is correct. The short story here is the FAA simply can't keep up with the innovation so they certify a group of people that can certify a repair as safe, and effective. It can than be used, while the FAA eventually full approves the change. The DER assumes full responsibility for the repair, and it's safeness. There have been stressful Christmas eves when approving the duct taping of a loose part of a V2500 so a plane full of troops can make it home for Christmas. Don't worry, it was a single flight one direction approval (but it happens all the time)