Cessna: Blue sky thinking on electrical power

Cessna has an interesting idea for how to better generate power or other services onboard a turbofan-powered business aircraft that is becoming more-electric.

In a patent application the Wichita-based company filed for a couple of months ago, it proposes to add -- either during production or for retrofit -- a turbine wheel specifically installed to spin up a generator to supply electrical, hydraulic, or other power to an aircraft.

According to the filing, the services turbine would be separate from both the low- and high-pressure turbine sections, and could be place at a various locations throughout the engine. The application shows the new turbine as the last stage in the engine, just forward of the exit nozzle.

Interesting thought. Cessna says its beneficial for many reasons, including:

• A free-turbine generator allows the engines to be designed for optimal efficiency and operating characteristics, since electrical load isn't tied to high- or low-pressure spools
• The optimization results in a free-turbine generator that costs and weighs less than the conventional spool-connected generator arrangement which requires the combination of a generator and an accessory gearbox
• The aircraft electrical system cost and weight can be reduced without the need for a power conditioning unit, the need for which is eliminated by the ability to maintain the speed of the free-turbine generator such that power output is substantially constant
• The free-turbine generator can provide significantly much more electrical power than can be provided from generators attached to either the high or low pressure spools.

Those are the positives? Any thoughts on the negatives? For one, an extra turbine could add to maintenance costs, though most costs are borne by the hot sections of the engine that are forward of the location Cessna suggests...

Read the entire patent application below.