User:Rahosi/sandbox
{{multiple issues|citation style=March 2011|external links=March 2011|orphan=March 2011|refimprove=March 2011|wikify=March 2011}}
WheelTug is an electric motor system that turns aircraft into a hybrid vehicles for forward & reverse gate, apron & taxiing operations without the use of main engines. Another such system is Safran's EGTS
WheelTug is a fully integrated ground propulsion system for aircraft which puts a high torque electric motors into the hubs of the nose wheels to allow for backwards movement without the use of pushback tugs and to allow for forward movement without using the aircraft's engines. WheelTug will drive the aircraft with power supplied by the onboard APU (Auxiliary Power Unit). Two versions are being designed. One for the Boeing 737NG & the other for the Airbus A320 with delivery expected in 2015.
Impact on Gate Operations[edit]
Safety[edit]
Two of the main risk sources for accidents and injuries at the gate are pushback errors and engine intake/blast.
Pushback errors can damage the plane and the pushback tug [1] or can injure or kill the tug operator. Collisions with the tug can take aircraft out of operation for days and have a cascading effect that adversely affects the flight and passenger schedules for the rest of the day, while smaller accidents include tow bar hookup where the tug operator risks injury to their hands or fingers.
Jet Blast behind the engines and the area in front of the engines (Intake Danger Zone) are eliminated in the gate area. When no physical gate exists and passengers disembark onto the open tarmac, then with certain aircraft configurations it is normally necessary to let the engines cool down before a hatch is opened to disembark passengers.
As many of the risk factors (tug collisions, jet blast, jet intake) will be eliminated, it is expected that WheelTug equipped aircraft will have reduced insurance premiums.
Start Times[edit]
Many airports have some form of engine noise curfew.[1] If a 6:15AM noise curfew is in effect, a WheelTug equipped aircraft will be able to back itself out of the gate and then queue up for the runway, warming up their engines for at 6:15AM for immediate takeoff.
Upon receiving clearance from the tower, pilots in WheelTug equipped aircraft can back away from the gate immediately instead of waiting for the tug to arrive. Standard tug pushback first requires the hook-up of the tow bar to the front landing gear, then the push, and then engine warm up. A WheelTug equipped B737 can save 120-150 seconds during pushback by changing the standard pushback process and transferring engine warm up from 'after the pushback' to 'prior to' entering the runway for takeoff.
Impact on Tarmac and Runway Operations[edit]
Fuel Taxi Margin[edit]
Presently, aircraft taxi by using one or more of the main engines, and therefore need to carry the fuel for taxi both to and from the runway, plus an extra amount for either expected or unexpected delays. Additional extra fuel is often carried 'just in case,' or in cases where there is a known or expected delay, and this can add several hundred pounds of weight to the plane and to its takeoff weight. With WheelTug eliminating the engines fuel consumption during all but the preflight warm-up and post flight cool-down period, the needed taxi fuel margin is reduced to just the fuel needed for APU operation.
Time Savings[edit]
In May 2004, a Performance Review Commission report prepared by the University of Westminster[2] put the cost of 'long' delays (of over 15 minutes) weighted by aircraft types and the known distribution at 72 Euros.
The Air Transport Association (ATA) calculated and reported the "Annual and Per Minute Cost of Delays to U.S. Airlines" as $38/hour/passenger and while Dr. Andrew Cook and Graham Tanner[3] calculated 0.36 Euros (2008).
Environmental Impact[edit]
CO2 emissions are reduced from both the aircraft's engines and the pushback tug's engine, to only the onboard APU. With only the APU being used to power the aircraft as it taxies to and from the runway, engines will be not be generating noise until it the warm up period begins before takeoff or the cool down period ends after landing.
Impact on Overall Maintenance[edit]
F.O.D. (Foreign Object Damage)[edit]
Engines suck in not only what is directly in front of them, but also items blown in from natural (wind) or unnatural (other aircraft) sources. WheelTug reduces the amount of FOD caused to the engines by limiting their operating times to only the 'warm up' and 'cool down' period
Studies on FOD have broken the per flight cost of into both ""direct" and "indirect" costs. The per flight direct cost of FOD is calculated at $26[4] by considering engine maintenance spending, tire replacements, and aircraft body damage. The per flight indirect cost of FOD includes a total of 31[5] individual categories, and when added, then the cost of FOD increases by a multiple of up to 10x.[6]
Brakes[edit]
Since standard aircraft taxi is controlled by playing the engines against the brakes, WheelTug will eliminate a significant amount of brake wear as the in-wheel motor will control movement and acceleration. Replacing brakes will become less frequent.
Engines[edit]
Engine maintenance is partially dependent upon the total numbers of hours the engine operates. For taxi times of 23 minutes on each end of the flight, with multiple flights in a single day, a Boeing 737NG equipped with a WheelTug can save hours of engine operation time and reduce the frequency of the plane being taken out of service. Another factor that affects engine maintenance is the Foreign Object Damage (FOD) to the engines which creates nicks and dings on the turbine blades. To remove nicks and dings, and to return the blades to a more aerodynamically efficient shape, the blades are 'blended;' however the blending process does not return them to their optimal shape, and therefore engine efficiency decreases. WheelTug's reduction of FOD will slow the degradation of engines efficiency over time .
Landing Gear and Aircraft Frame[edit]
As a standard pushback tug has its own inertia (separate from the aircraft), pushback tugs impart a shock to the landing gear as the tug and tow bar move with their own inertia before the aircraft moves. As WheelTug's motor is inside the wheel hub of the landing gear itself, all starts are smooth and there is no shock to the landing gear or airframe.
WheelTug Design[edit]
A thumbwheel or rocker type switch in the cockpit will allow for simple operation by the pilot. The inverter/controller in the electronics bay will be independent of the rest of the planes command and control system, and will log position with a GPS module and record other operational information to provide the aircraft owner with additional data for analysis. The motor and gearing will fit within the wheelhub and WheelTug Plc has said its engineers have now designed a solution that also achieves five key design requirements:[2]
- Do not increase the wheel/tire assembly spin-up loads during landing.
- Avoid changes to existing landing gear major components, such as the piston/axle assembly.
- Enable aircraft tire changes as quickly and as easily as is done currently.
- Prevent inadvertent engagement. Unless the aircraft is on the ground, and the pilot has explicitly powered-up the WheelTug system, the motors must not engage with the wheels.
- Match the motor and wheel speeds before engagement, to eliminate the need for a clutch.
As tire changes involve removing the wheel, then depending upon the economic model used (WheelTug sale or lease), the WheelTug wheel can either be rated for the FAA minimum wheel mileage rating requirement or produced as a 'high end' wheel. If produced at the minimum rating, then its replacement cost can be folded into the cost of the lease.
History[edit]
Proof of Concept Test[edit]
Boeing Phantom Works and Chorus Motors test WheelTug Concept on an Air Canada 767 in June 2005 at the Evergreen Air Center at Pinal Air Park in Marana, Arizona. [3] [4]
Electric Load Measurement[edit]
WheelTug Limited and Co-Operative Industries complete an Electrical Load Measurement (ELM) on a B737NG in January 2010 at Hartsfield-Jackson International Airport in Atlanta, GA to confirm sufficient power. [5]
Data Gathering Tests in Prague[edit]
Tests were conducted at Prague Airport in November 2010 in snowy and icy conditions. [6] [7]
In Wheel Electric Drive System Test on Boeing 737NG[edit]
Tests were conducted at Prague Airport in June 2012. [8] [9]
Strut Swing Tests on Boeing 737NG and Airbus A320[edit]
Tests were conducted in Istanbul & Panama in November 2013. [10] [11]
Partnering Companies[edit]
Co-Operative Industries Aerospace to develop and supply the wire harness for the Boeing 737NG for WheelTug. [12]
Dynetic Systems, Inc. to become responsible for designing the Chorus motors for WheelTug’s electric nose-wheel drive system for aircraft. [13]
Endeavor Analysis to provide structural and strength analysis work for the landing gear connected to the WheelTug system. [14]
ICE Corporation to design, develop and build the controllers for the aircraft on-ground electric drive system being developed by WheelTug plc.[15]
Newport Aeronautical Development, Inc. to assist it in meeting FAA standards for a supplemental type certificate covering Boeing 737-600, -700, -800 and -900 aircraft.[16]
Parker Hannifin partner for developing, testing, certificating, producing and supplying the physical nose wheels.[17]
Prague Airport to actively assist WheelTug with the development support during testing and certification.[18]
Resource Group to develop software for WheelTug and to become a significant shareholder. [19]
Travel Service Airline to provide access to aircraft in connection with the design, development and testing of the WheelTug system. [20]
References[edit]
- ^ Raquel Girvin (2009). "Aircraft noise-abatement and mitigation strategies" (PDF). Elsevier Ltd.
- ^ University of Westminster (May, 2004). "EVALUATING THE TRUE COST TO AIRLINES OF ONE MINUTE OF AIRBORNE OR GROUND DELAY" (PDF). European Organisation for the Safety of Air Navigation (EUROCONTROL).
{{cite web}}: Check date values in:|date=(help) - ^ Dr. Andrew Cook and Graham Tanner (Sept, 2009). "The challenge of managing airline delay costs" (PDF). University of Westminster.
{{cite web}}: Check date values in:|date=(help) - ^ "The economic cost of FOD to airlines" (PDF). Insight SRI Ltd. March 2008.
- ^ "The economic cost of FOD to airlines" (PDF). Insight SRI Ltd. March 2008.
- ^ "The economic cost of FOD to airlines" (PDF). Insight SRI Ltd. March 2008.