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FUEL COSTS are an airline’s worst enemy. Over the past fifteen years rising global demand and political unrest at main suppliers have seen the commodity jump to an average of 40% of an carrier’s overall costs. That fact is concerning since fuel is a volatile cost, prone to sharp rises and falls in price over short periods of time, making even the soundest of budgets unreliable. Thus efforts to curb this risk are growing, the latest product of these efforts is the ability to taxi without using engines or a tug.

WheelTug, a subsidiary of Chorus Motors, has developed a small but powerful electric motor installed in the nose-gear that draws energy from the APU. Able to provide enough torque to get an aircraft moving, it can also taxi at standard speeds with a full passenger load. The company successfully trialled the system on a Boeing 737-700 this summer, as can been seen here.

WheelTug claim that savings on a Boeing 737-800 of roughly 95,000 gallons, or by accountants estimates; $500,000 per year. They go on to mention other advantages; reduced engine wear, environmental benefits and less dependability on airport staff (no need for pushback tugs).

With merits come detriments. The WheelTug device adds approximately 300lbs to overall weight, which over the course of an entire flight results in higher fuel burn and hence reduced range. And while engine maintenance will be reduced, the device itself will bring its own reliability issues to airline operations.

The first five airlines to commit to the new technology, with El Al planning to be the first to fit the device in mid 2013

WheelTug are not alone in the engine-less taxi field, hot on their heels are Messier-Bugatti who are working closely with Airbus to incorporate their taxi system into the main landing gear of the A320neo. Unlike WheelTug, Messier-Bugatti benefit from established relationships in the industry, having designed numerous landing gear components for both Boeing and Airbus.

Whilst very much in its infancy, this technology shows the most promise since the advent of blended winglets, now a common sight on Boeing aircraft and soon to be introduced on the A320 family. As was the case with winglet technology,  engine-less taxiing has a great chance of being the next major trend to be adopted by airlines worldwide.

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8 thoughts on “The new winglet

  1. Savings are claimed to be 50% plus higher in the latest WheelTug Video, http://youtu.be/tvHwaFwQ_LY

    Typically the 300lb weight of the WheelTug system weighs no more than, and often less than, the weight of the taxi-in fuel that would otherwise have to be carried during the flight. Thus WheelTug is typically weight neutral or better and not detrimental to fuel burn.

    WheelTug will prevent most of grit and other FOD damage to the blades. On new & nearly new engines, blade blending will be avoided with WheelTug installed. WheelTug will minimise this progressive 0.5% loss in in-flight fuel performance that would otherwise happen over a period of time.
    (On some short routes, engines run longer on the ground than in the air.)

  2. Just to make my previous system weight comment clearer.

    Pilots load extra taxi fuel to avoid returning to the gate in case of unexpected taxi delays. They normally carry this fuel in flight. WheelTug reduces this weight and is thus weight neutral or better.

  3. actually there is some 2-5,000 lbs of fuel planned for taxiing and take off, and cannot be carried into the airk because of weight limitations.

    • wuzafan is not correct. The amount of fuel set aside for taxi is not a real limitation except when the airplane is loaded to its maximum weight limits. Then the limits are Max Taxi Wt [actual max allowable wt at engine start] vs Max Takeoff Wt [assumed max allowable wt at brake release].

      For Boeing airplanes the typical difference between the two numbers is:

      737 – 500 lbs
      747 – 3000 lbs
      757 and 767 – 1000 lbs
      777 – 2000 lbs

      The problem is when there is a long line for takeoff which uses trip fuel on the ground

      Several decades ago there was a 747-200 operator with a MTOW of 775000 lbs that was allowed extra fuel above the 778000 lbs max taxi limit only at Honolulu so they could taxi from the terminal all the way out to the reef runway and still take off at 775000 lbs

      The wheeltug’s net fuel saving is the difference between engine fuel that would have been used to taxi to the runway minus APU fuel used to power the wheeltug until the engines are started.

      Left unanswered in this article is whether the APU can be used to start the engines [electrical and pneumatic] while electrical power is being drawn for the wheeltug

    • It’s called Maximum Ramp Weight or Maximum Design Taxi Weight and is always a bit higher than Maximum Takeoff Weight (MTOW). The aircraft must reduce to MTOW for takeoff in compliance with regulations.

      But 300 lbs is Boeing’s passenger design allowance (on their marketing PR) plus 90 pounds. If you removed two passengers from a Dublin-Madrid flight, you’d loose €52 direct revenue potential on that single flight. Operated four times weekly, 52 weeks would amount to €10,816 ($14,085) direct loss, excluding additional ancillary charges. (Bit of a simplistic view, may need some rework.) It still pales in comparison the $500,000 gain WheelTug claims. It’s a nice solution.

  4. Paulo, takeoff weight = empty weight + payload + fuel. Any or all of those parameters can be changed as needed provided that the sum does not exceed the certified MTOW limitation.

    Dublin-Madrid [784 nm, 1452 km] is well within a 737’s max range so the airplane’s takeoff weight would be below its MTOW. No one would get left behind – just add a bit more trip fuel for the same payload to be carried in an airplane with 300 lbs higher empty weight.

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