By Larry Dignan
Posting in Aerospace
Honeywell and Safran, a French aerospace company, said they will launch a joint venture to create an electric taxiing system for airplanes in a move t...
Honeywell and Safran, a French aerospace company, said they will launch a joint venture to create an electric taxiing system for airplanes in a move that will save money, fuel and carbon emissions.
The companies said the electric taxiing system will use an airplane's Auxiliary Power Unit (APU) generator to power motors in the main wheels without using primary engines while on the ground.
Under the joint venture's plan, the Honeywell-Safran system will be installed on new aircraft and retrofitted on existing planes starting in 2016. The two companies appear to be a good fit since Honeywell specializes in auxiliary power units and Safran makes landing gear systems.
Safran explained how the system works on its Web site:
From the technical standpoint, each powered wheel in the main landing gear is equipped with an electric motor-reduction gearbox-clutch assembly to drive the wheel. The aircraft’s own auxiliary power unit, or APU, provides the electrical power needed by the motor. The APU is actually a gas turbine/generator unit, generally located in the fuselage tail, that provides the electrical power needed to start the jet engines, power air conditions and supply electricity for other onboard systems, mainly on the ground when the jet engines aren’t operating. With this new system, we can also do away with the tractors that tow the aircraft after the doors are closed at the loading gate. In other words, the aircraft taxis using only electric power until just a few minutes before takeoff – and then again after landing, right after it leaves the runway.
Among the key benefits of this electric taxiing system:
- Airplanes will be able to push back from the gate and go faster.
- Fuel costs and related equipment costs such as tugging, brake wear and carbon emissions taxes will decline.
- Airlines will save "several hundred thousand dollars" per aircraft a year.
The two companies said that they will initially focused on narrow-body aircraft, which are used for short-range flights and are generally more sensitive to fuel costs.
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Jun 19, 2011
Lufthansa has developed an airplane tug that cradled the planes front wheels to lift them for towing instead of pulling on the landing gear, which reduced stress on the landing gear. They had been using it for years when I read about it in the 1990???s. They used it for noise reduction reasons at the Frankfort airport. Planes no longer ran their engines to taxi when night flights landed. At that time the fuel savings was considered a minor bonus compared to ending the noise complaints.
"The aircrafts own auxiliary power unit, or APU, provides the electrical power needed by the motor. The APU is actually a gas turbine/generator unit, generally located in the fuselage tail," -------------------------------------------------------------------------- The plane's own wheels could be used during 'braking' to generate energy to be stored and resupplied to assist in Taxiing, Auxiliary power, etc... Thus, relieving some of the load needed by the APU.
...is that they don't go very fast, and using them for taxing would require many more of them plus an operator for every plane on the runway, the cost of which would likely cancel out any fuel savings.
To use the landing gear in this fashion would introduce harsh stresses that today's gear are NOT built to handle. Remember, their main function is one of safety, to let the craft reliably land safely. Future gear designs might change to accommodate such a concept, but regenerative braking would also imply that the power was coming from (heavier-weight) batteries of some kind. Weight is always of primary concern, to an aircraft design.
This only makes sense if the apparatus required is light enough. Remember that it costs fuel to carry weight. Motor technology may have come far enough to create an electric motor that can move a plane weighing over 50 tons that weighs less than 200 pounds. But the batteries required for a regenerative system capable of powering that motor would likely weight tons; The fuel required to fly that extra weight would be far more than any saved in taxiing.
I saw nothing in the article, and nothing on Safran's web site about regenerative braking. It appears as if they are using a simple, geared-down electric traction motor. The added weight to the aircraft would be the motors, gearboxes, and the additional wiring.
Pretty conclusive statement there Mr John... guess you've done the math on the companies' behalf? LMAO