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Winter operation tips for your aircraft tractor

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The truth about snow tires  

Eagle Tug Ice TowSnow tires will not increase your traction on anything but un-compacted snow. With snow tires, you  will experience a 15 percent to 20 percent loss in traction on dry pavement. You will also experience a loss of traction on ice because the surface area of the snow tire is approximately 20 percent smaller than a standard tire. Snow tires excel only in un-compacted snow.

Instead of purchasing expensive snow tires that will offer inferior performance in most conditions, you might consider having your existing tires “siped.” The siping process puts tiny cuts across the tread increasing the tire’s gripping edges while not reducing the footprint.  Additionally, siped tires offer greater traction on slippery hangar floors and allow for a longer tire lifespan.

Traction tips for aircraft pushbacks: 2-wheel drive and All Wheel Drive (AWD) tractors:

  • Sipe tires.
  • Reduce air pressure in pneumatic tires from 60 PSI to as low as 25 PSI. NOTE: Restore air pressure to 60 PSI as soon as weather emergency ends.
  • When pushing with AWD tractors, make sure the towbar is level or slightly downhill toward the tractor.
  • When pushing with 2-wheel drive (rear drive) tractors, towbar should be level or slightly downhill toward the aircraft.
  • When pushing aircraft on ice or icy snow with AWD, a wheel may lose traction (wheel spin). To stop wheel spin, apply the brake gradually with left foot until wheel spin stops and holds. While continuing the pushback, coordinate the left foot brake pressure and the right foot accelerator to maintain a smooth pushback.
  • On ice or snow, use chains or cables. NOTE: If the use of chains is prohibited, traction cables serve the same function as chains, but are much easier to mount and cause only mild abrasion to surfaces.
  • Keep fuel tank full.
  • Apply a light braking action at the start of the pushback to lock up the front end.
  • Don’t “jump or jerk” the unit at the start of the push. Gently increase the RPM until breakaway.

Pushback Tug Capacity vs. Aircraft Pushback Resistance

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Eagle Tow Tug TractorWhat Size Tug Do I Need: Pushback Tractor Capacity vs. Aircraft Pushback Resistance

Let me first begin by stating that I am no mathematician or physicist, in fact I am far from either…

However, I do receive many inquiries from customers who have a difficult time selecting the proper aircraft tug for their exact application.  So for my first several posts I want to focus specifically on aircraft pushback tractors (and will provide more GSE info in the future).

Correctly matching your tug’s drawbar pull rating (DBP) to the aircraft’s maximum take-off weight (MTOW) will reduce pushback and towing incidents. The following information will serve as a good guide in providing the proper towing equipment for your ramp operations as it is a common subject in the aircraft handling world.

The International Air Transportation Association (IATA) in a Toronto meeting summary memorandum titled “Push back communications” stated that 87% of ramp accidents occur during aircraft push back. 82% of those accidents involve the nose gear. 

The conclusions were:

  • Better training of the pushback procedures to pushback personnel are required.
  • Improved communications with the cockpit by the pushback tractor operator are required.
  • Proper pushback tractor and towbar capacity for the size of aircraft being moved will result in elimination of towbar and nose gear damage.

IATA Airport Handling Ground Support Equipment Specification AHM 955: “Functional Specification for an Aircraft Tractor.”

Paragraph 1.4 states ”There shall be four categories of tractors defined in accordance with the maximum aircraft weight.”

  • Category 1 – aircraft less than 50,000 kg. (110,000 lb.)
  • Category 2 – aircraft less than 150,000 kg. (330,690 lb.)
  • Category 3 – aircraft less than 260,000 kg. (573,196 lb.)
  • Category 4 – aircraft more than 260,000 kg. (573,195 lb.)

Paragraph 3.7 states “The minimum tractor weight for each class as defined in paragraph 1.4 shall be”:

  • Category 1 – 4,000 kg. (8,800 lb.)
  • Category 2 – 12,000 kg. (26,455 lb.)
  • Category 3 – 18,000 kg. (39,683 lb.)
  • Category 4 – 40,000 kg. (88,184 lb.)

Category 2, 3 or 4 tractors, generating 300% to 1000% greater DBP when pushing Category 1 aircraft can greatly increase pushback issues caused by excessive power. Aircraft pushback incidents therefore increase because the towbar and nose gear are not rated to absorb the excessive power of these larger tugs.

The Category 1 tractor has pushback power protection limits as follows:

  • Tractor’s drive wheel(s) will slip and lose traction when the Category 1 DBP traction weight (8,800 lb.) is exceeded.
  • The torque converter will stall at 8,000 lb. DBP to protect the towbar and/or aircraft nose gear.

*These protections are not available when using Category 2, 3 or 4 tractors to push Category 1 aircraft.

Basically stated, using the correct tug for the weight of the aircraft you are moving is essential; as you may find yourself purchasing an aircraft nose gear that far exceeds the cost of a new tractor…

AERO Specialties is dedicated to providing equipment to safely handle your GSE requirements. To make things simpler we have compiled a list of the proper pushbacks for the majority of the aircraft in operation around the world.  Don’t hesitate to ask if you require verification or advice.

Your comments are invited and greatly appreciated!

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