How Do Towbarless Tugs Work?
BY
MARK FINLAY
PUBLISHED 2 DAYS AGO
How towbarless tugs work.
Photo:
Michael Pereckas via Wikimedia Commons
Often called
pushback tugs because they are used to push aircraft away from the
gate, these tugs are low-profile
tractors. Many modern airliners can move backward using
reverse thrust, but the noise, damage to the terminal building, and injuries to staff due to flying debris do not make it worth it. Using reverse thrust also risks sucking unwanted debris into the engines, which may cause damage and increase maintenance.
A conventional tug with a tow-bar. Photo:
Jamesshliu via Wikimedia Commons
Before we get into how towbarless tugs work, let's first look at all pushback tugs. While small light aircraft can be moved using human power, modern jet airliners weigh thousands of pounds, meaning you need a heavy, powerful tractor to move the plane. Constructed with a low profile so that they can fit underneath the aircraft, pushback tractors typically weigh up to 54 tons.
Conventional tugs use a tow bar
Conventional pushback tugs use a metal tow-bar connected to the tug and the nose landing gear of the plane. To avoid the landing gear being overstressed when the aircraft is pushed back, the tow bar has a shear pin that will snap and disconnect it from the plane.
Because the pilots cannot see what is behind them, the ground handlers control the pushback and steering. On some aircraft, a bypass pin is installed to temporarily disconnect the nose gear wheels from the aircraft steering mechanism. Once the pushback is complete, the ground handler will hold the pin in the air to show the pilots that it has been removed.
Towbarless tugs slide under the nose wheel and lift
Unlike the tow-bar tractors we mentioned above, towbarless tugs do not use a tow-bar. Rather than connecting themselves to the nose gear they lift the nose landing gear wheels off the ground using hydraulics. Doing this saves all the time involved in attaching the tow bar to the plane and the tractor. It also frees up the ramp by removing the complexity of where to store the tow bars.
Because of how it works, towbarless tractors do not need to be as big as traditional tractors as the aircraft nose wheel provides the necessary weight and downward force. Also, unlike a tug that needs a tow-bar, a towbarless tractor does not, as it has a single pivot point rather than two. This allows for a more straightforward and more precise pushback.
In recent years, more airlines are moving away from diesel-powered tugs and using
electric towbarless tugs for aircraft pushback's. Not are electric tugs more environmentally friendly, but they also allow the tugs to be used in indoor spaces like aircraft handers as there are no fumes to worry about.
TaxiBots could be the future
Looking to the future, the Lahav Division of Israel Aerospace Industries has developed a semi-robotic towbarless tug it calls a "TaxiBot." Rather than push the aircraft back from the gate, the TaxiBot transports the plane from the gate to the runway (taxi-out phase). After landing (taxi-in phase), the TaxiBot meets the aircraft as it departs the runway and takes it to the gate. Using a TaxiBot would eliminate the need to burn fuel taxiing to and from the runway, potentially saving airlines billions of dollars. The TaxiBot has a driver who ensures that the planes nose wheel is lifted correctly but after that the pilots in the aircraft control it from the cockpit.