Noise or Emissions – We Can Do Without Both

GreenAirOnline, a web report on mainly airline attempts to promote environmentally-friendly flying, has two not-unrelated stories in today’s edition.

Noise abatement is a major issue for British airports, especially those in the southeast, according to the first story.  Kate Jennings, Head of Aviation Policy Implementation at the Department for Transport, says the government recognizes that it is a “particularly contentious issue.”

Even though noise has been reduced for individual flights, flight frequency has increased and measured noise footprints don’t always match the perceived noise levels that drew public complaints, Ms. Jennings reported.

“That’s why at an ICAO (International Civil Aviation Organizaton) and political level we need to keep the pressure on to identify ways of further reducing noise and there needs to be an intelligent debate on the trade-offs between emissions and noise,” she told the recent UK Airport Operators Association (AOA) Environment Conference in London.

British airports have been practicing several approaches to cutting both emissions and noise, including continuous taxiing – coordinating ground control with the aircraft to enable as many aircraft as possible to taxi directly and without stops and holds to their designated takeoff or gate destination.  Reduced engine taxiing (RET) allows pilots to use fewer engines to taxi, saving fuel burn.  Fixed Electrical Ground Power (FEGP) allows providing electrical power to the aircraft without the use of the auxiliary power unit (APU), saving fuel and cutting down noise.

As reported before in the blog, both fuel burn and noise can be reduced by landing-gear driven taxiing.  This need is being addressed by WheelTug, a multi-national endeavor producing an in-wheel motorized system for Boeing 737s, mirroring the functions of at least three other organizations providing such equipment for Airbus 320s.

Alitalia has reserved 100 of the systems for its A320 aircraft, becoming the “launch customer” for the WheelTug. Being able to taxi backwards and forwards without tow tug or the use of engines will enable “up to an 80% reduction in the fuel consumption for aircraft ground movements, with a significant reduction in cost, noise, and environmental impact,” according to Alitalia.  El Al Israel, Israir, and Jet Airways have also signed letters of intent with WheelTug.

WheelTug uses the aircraft’s APU, unlike the Airbus unit, which uses a special fuel-cell power system to drive the nose wheel.  The system is isolated from other aircraft systems, though, and does not use the bus system than connects other electrical and electronics devices on the airplane. It is meant to be intuitive in use and should lessen pilot workloads during taxiing.

The Prague Airport testing video is fascinating, showing the enormous torque and surprising traction the two Chorus motors bring to the 130,000 pound aircraft.  According to the Chorus web site, the wheel hub motors possess 10 times the power to weight of other AC induction motors and run on 30-percent less current, allowing use of a smaller, lighter controller (built in Kansas, incidentally).  They make the 737 with their nose gear into a series hybrid, giving proportional much great “fuel” mileage during taxiing than the normal two-jets burning vast quantities of expensive fossil fuel.