Push back to the future

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Tractors are under increasing technical pressures to accommodate stringent emission control standards introduced in Europe and North America. Airside International investigates the latest advances in towbar and towbarless technology.

  It is a blinding statement of the obvious to suggest that tow tractors are a vital and integral element in the ground support equipment (GSE) industry, covering a number of different categories.  Aircraft push back and towing vehicles are typically used for moving small, narrow-bodied aircraft with a Maximum Takeoff Weight (MTOW) of up to 30 tons, medium-sized aircraft (MTOW up to 120 tons) and wide-bodied aircraft with an MTOW in excess of 150 tons.

Like other aspects of ramp vehicles, the tractors are increasingly under technical pressures to accommodate the stringent emission control standards being introduced in Europe and North America. This influence has led to the introduction of electric/hybrid/CNG/LPG-operated types in addition to traditional diesel-powered tow tractors that still tend to predominate.

Future market prospects for manufacturers seem to be positive, despite the economic woes of the West. Economic activity and its stimulation of the market in Asia/Pacific, parts of the Middle East and increasingly the emerging economies of sub-Sahara Africa, is healthy with good future prospects. In North America and Europe, replacement of older, less efficient equipment is a continuing market stimulus.

A major change in technology came with the introduction of towbarless tractors (TBLT), an interesting option for prospective customers to consider, although it is likely that customers still view a new purchase in the light of cost of ownership, safety, efficiency, performance and maintenance costs tailored to their particular needs. In practical terms, customer choice reflects individual operational requirements.

For push backs, conventional tractors are most efficient when a customer services just one aircraft type. This benefit is reduced when applied to a wider range of types, due to the requirement for different types of tow bars.

A major attraction of TBLTs is that they offer flexibility and a tighter turning radius that can prove a boon on congested ramps. One major carrier decided to standardise on TBLTs, following a tow bar failure under tow that led to damage to two aircraft.

It’s all a question of choice tempered by operational requirements and the wide and ever-increasing range of vehicles that are currently on the market.

However, technology continues to advance and automation is very much the pace setter in aviation.

Mototok International GmbH developed a high tech wireless remote controlled helicopter and aircraft tug featuring radio remote control. The system enables the movement of the aircraft to be controlled at every conceivable collision point around the aircraft and can be used for almost all aircraft quickly and without conversion. Electric motors, driven by high performance, maintenance-free GEL batteries, with high cycling capability and regulated and controlled by two high-performance microprocessors, provide the necessary driving forces.

TaxiBot is a joint development by IAI’s Lahav Division and Airbus of a pilot-controlled semi-robotic towing system. Last year, they conducted an operating test with a B747-400, at Frankfurt International Airport. The TaxiBot Dispatch Towing system, designed by IAI, allows aeroplanes to taxi to and from the airport gate to the runway without the need to operate their jet engines. It is powered by a diesel engine and has electrically driven wheels.

The TaxiBot programme was launched in mid-2008, with the contribution of a Lufthansa LEOS Krauss-Maffei TPS-1 that became IAI’s base vehicle for the TaxiBot demonstrator. From the start of the programme, Lufthansa LEOS supported the TaxiBot team consisting of IAI, Airbus, TLD and Ricardo. Work is continuing to develop a TaxiBot prototype vehicle for narrow body aircraft, such as the A320 and B737 families.

The following listing is representative of what is currently available and it is processed in alphabetical order, to avoid unintended suggestions of superiority.

Bliss-Fox Ground Support Equipment, part of the NEPEAN Transport Group, is an Australian company that has been supplying ground support equipment for over 40 years. The Company has developed a suite of tractors including the F1-500 54 – 70 tonne, the F1-300 27 – 45 tonne and the F1-80 9 -12 tonne, as well as a uniquely designed TBLT for the push back, tow, or hanger movements of empty or fully laden commercial aircraft including A300, A310, A330, A340-300/600, B767, B777 B747-400.

Typically, the F1-500 version is designed for both push back and extended towing of aircraft up to 600 tonnes (A380-800F). Drop-in ballast easily transforms the tractor from a standard 54 tonnes for A340 & B747 up to 70 tonnes for A380-800F with no obstruction to the operators’ line-of-sight. The F1-500 features a 360kW (483 hp) diesel Engine with 1990 Nm (1468 Ft/lbs) of torque. This tractor is built on the Company’s exclusive, integral perimeter frame chassis, which is guaranteed for life.

Charlatte is a member of the Fayat Group of companies and is a manufacturer of battery-powered electric airport ramp vehicles. The Company developed the CPB35E, an 80V AC electric powered push back tractor.  The unit offers the advantages of electric power for push back operations, including quiet ramp operation, no smoke or fumes and limited maintenance.

Power for the main drive is supplied by two, 35 hp (26 kw) AC motors. The unit uses four-wheel drive and has excellent visibility with a maximum speed of seven mph (11.3 km/h) when empty. Drawbar capacity is 24,000 lb (10,880 kg). The unit is suitable for push back operations on aircraft ranging from 737s to 757s.

In 2011, Curtiss-Wright Flow Control Company acquired the assets of Douglas Equipment Ltd. Douglas, a supplier of aviation support vehicles, became part of Curtiss-Wright’s Flow Control Segment.

The TBL-600, incorporating the latest CanBus electronic control technology TBLT, has been designed for handling aircraft ranging from the Airbus A310/Boeing B767 up to and including the Airbus A380. The Douglas Tugmaster type DC10-44 conventional aircraft towing tractor can be ballasted from 25 tonnes to 43 tonnes, giving it the capability of handling aircraft up to a B747.

Similarly, the DC5-42 conventional tractor can be ballasted from 5 tonnes to 7 tonnes and is designed for push back and towing operations with regional type aircraft, with maximum ramp weights up to approximately 50 tonnes.

The Eagle XL Series tractors were designed by Eagle Tugs to move all “single-aisle” commercial aircraft. The XL Series feature standard All Wheel Drive (AWD) power trains, providing safe, controlled traction in all weather conditions, as well as All Wheel Steering for superior manoeuvrability. The XL Series is available in either diesel or electric power trains to meet customer needs. The Eagle TT and eTT series aircraft tractors also feature AWD. Typically, the eTT-8 model is an all wheel drive all wheel steer electric tractor and it is the only type in the world at this weight class. Since 1969, Eagle Tugs has specialised in military and business aircraft applications. The Company enjoys global sales and has a distributor (ASR) in England. The TT and eTT aircraft tractors are also backed by a three-year/3,000-hour warranty.

            FRESIA SP offers a range of tow tractors for all types of aircraft. These are the SP100 from 14 up to 18 tons weight, SP200 from 20 up to 25 tons weight, SP300 50 from 43 up to 55 tons weight and the Company flagship SP 300 60/70 from 60 up to 70 tons weight, which can handle any aircraft up to the A 380.

To ensure optimum customer choice, various configurations and options are available. The Company claims a number of technical advantages, including both front and rear axles mounted on leaf spring suspensions. In addition, it manufactures its own “over-engineered” heavy-duty axles. To further ensure reliability, a third central differential is installed, between the axles, which provides stress release on the wheels and greatly reduces tyre wear. Four wheel, twin-calliper, disk brakes ensure maximum stopping capability and facilitate maintenance.

The advent of the A380 presented something of a technical challenge for airport ground services. GHH Fahrzeuge rose to the occasion with the AM500-XL, a modified version of the well-proven AM500.  The AM110R2 and AM210 TBLT’s range now covers Embraer 170/190 aircraft.

A new designed tow bar tractor TT15, with a tractive force of 120kN, making it suitable for handling aircraft up to 150 ton maximum taxiing weight, is also available.

In 2007, GHH Fahrzeuge signed a partnership agreement with a Chinese partner, Weihai Guangtai Airport Equipment Co., Ltd. More recently, GHH Fahrzeuge combined sales and service activities with Weihai Guangtai. The new sales and service company for the European market, GSE Europe GmbH, is responsible for all customer related activities of both companies.

The heart of all Goldhofer AST-tractors is the maintenance-free pick-up device that enables quick and safe handling of aircraft. During the towing procedure, the pick-up device is continuously controlled and monitored by sensors and any malfunctions are displayed to the driver. This enables action to be taken immediately in case of problems. The patented cardanic suspension of the pick-up device ensures that the total pick-up device can accommodate the movement of the nose-gear, without inducing additional forces during cornering.

The Goldhofer control-engineering concept, which is programmed “in-house”, offers safety and service convenience with the individual modules being exchanged via pluggable connections.  A Goldhofer Overtorque Indication System for the nose-gear has been developed in accordance with the aircraft manufacturer’s specifications and ARP 5284 guidelines.

The TBLT AST-1 X series is said to set new standards in moving wide-bodied jets. With constant development of the successful AST-1F/L, the aircraft range has been extended upwards. This means the AST-1 X tractor is now able to efficiently move all current aircraft from the A300 / B767 right through to the A380 / B747-8 in the 400t to 600t MTOW class.

   Harlan offers hybrid and electric towing tractors with 5000 lb drawbar pull. Hybrid tractors charge the electric battery while running on diesel.

The Expediter TBLT family has been designed, by JBT AeroTech, for push back and maintenance tow for a wide range of aircraft. Expediter 160 is for push back only or push back and maintenance tow versions to handle narrow body aircraft from A320 and B737s to A300 and B767s. Expediter 300 is push back only to handle narrowbody and widebody aircraft from A318 and B737s to A340 and B777s. Stepping up a gear, the Expediter 400 is for push back and maintenance tow to handle widebody aircraft from the A310 and B767s up to A340 and B747s. The big hitter is the Expediter 600, intended to handle aircraft from A310 and B767 to the B747 and A380.

The Expediter TBLTs have a stable design to prevent jack-knifing, automated aircraft selection and pickup to reduce the potential of operator error; PLC diagnostics help to identify maintenance issues and a 15 year or 30,000 hour life.

LEKTRO pioneered the TBLT market when it first developed the TBLT tug back in 1967. The Company combined its TBLT design with state-of-the-art battery power resulting in a most efficient and environmentally-friendly tow tractor. LEKTRO likes to say that it has a tractor for every purpose. It now offers five “families” with towing capacity ranging from single engine trainers to Boeing 737 (180,000 lbs.) The next model currently in design will be capable of handling up to 250,000 lbs.

Regardless of the type or weight class of the aircraft, with the nose wheel cradled at the front of the tug, LEKTRO eliminates all but one pivot point. This reduces turn limit damage and gives the vehicle its renowned manoeuvrability. The LEKTRO TBLT can also be used to raise the nose of an aeroplane, lowering the tail when moving it into a hangar that would otherwise be too small.

The SCHOPF product range for civil aviation and military deployments includes a complete range of aircraft tow tractors from the F59 up to the F396-fleet, which represents 70 per cent of A380 push backs worldwide, as well as diesel/hybrid tractors of the ROFAN brand. The Company also produces a remotely controlled TBLT push back tractor for aircraft of up to 100 metric tons weight. SCHOPF PowerPush is said to be the only one of its kind, reducing labour costs by up to 70 per cent.

In conclusion, Trepel’s versatile trio of tugs offer a broad choice. The CHALLENGER 160 is a conventional aircraft tractor that is capable of handling push back and maintenance towing of aircraft size up to a fully loaded Boeing B767. The hydro-pneumatic front axle suspension provides best possible driving comfort for the operator. The liftable power pack compartment minimises downtime of the tractor, reduces maintenance costs and is common to all three vehicles.

The CHALLENGER 430 can handle similar towing of aircraft up to a fully loaded Boeing B777. The mechanical lock-up clutch of the new generation of power shift transmissions reduces fuel consumption when moving at higher speed.

The CHALLENGER 700 is in the major league capable of handling up to a fully loaded Airbus A380. It also features the mechanical lock-up clutch.

Other manufacturers active in the tow tractor sector include KAMAG products such as TowBear and the Disabled Aircraft Recovery and Transport System. The TowBear aircraft tow tractor, the latest generation of conventional aircraft tractors, has been developed in very close co-operation with airlines, ground handling companies and service personnel. The dead weight of the TowBear TT can be changed by using the ballast weights that are located on top and inside of the tractors and allow an easy and quick adaptation of the tractor weight to individual requirements.

The Little Big Tug Company Ltd. (LBTC) based in UK, specialises in the rent, hire or lease of tow tractors and also claims to be the first company to specifically design and build a heavy aircraft towing and push back tractor for the global rental market. LBTC set out to build one of the cleanest, quietest and strongest tractors in its class. The result, the 2003 T80 aircraft towing / push back tractor, achieves these goals. All LBTC’s tractors are certificated by British Airports Authority (BAA), with a 20-year operating life.

NMC-Wollard Inc offer the Model 140 and ModelA low profile, dual purpose and low centre of gravity tow tractor, ideal for corporate and regional jet applications. An 8,000 to 14,000 DBP tow tractor has proven itself in many corporate and regional jet applications including push back and cargo hauling. This model can be powered with gas, diesel, LPG or CNG.

Lynco Tugger Corp highlights its Hydra-Tug whose pulling power lies in its hydrostatic system and its weight distribution. The hydrostatic drive system is powered by a four-cylinder, gasoline, LPG or diesel engine. The hydraulic motors on the front drive wheels are coupled with specially designed gear reducers to produce more power per engine horsepower than conventional tugs. The Model 6KD has a level drawbar pull of 4,000lbs while the Model 12KD can cope with up to 9,600lbs.

PT United Tractors Pandu Eng (PATRIA) was founded in Indonesia in 1983, initially to serve local needs. It is now an established organisation serving a number of ground service requirements. There are now two types of Patria aircraft towing tractors, PDT 50T with maximum drawbar up to 5000kg and PDT 60T with maximum drawbar up to 6000 kg.

Trowin Industries Inc offers two push back tractors, the Mk VI and Mark VII. The Mark VI low profile push back tractor is available as 16,000 & 35,000 lb DBP. Powered by a Cummins 4BTA3.9, 3.9 ltr four-cylinder turbo-diesel engine as standard or Ford ESG-4.2 ltr V-6 EFI industrial petrol engine. The Mark VII is in the 40,000 & 60,000 lb DBP class and also has a choice of diesel or petrol engine.

TUG Technologies Corp TUG Model MR-10 has a very low profile to ensure greater visibility in all directions for safe operation. The Model MR tow tractor is offered in an 8,000 DBP weight package as well as a 10,000 DBP package.  Two diesel engine choices are available: the Deutz BF4M2011 and the Kubota V3600-T-E3B.

The VOLK EFZ 100 N, from VOLK Fahrzeugbau GmbH, is an electric push back tractor with a towing capacity/MTOW (IATA) of 100,000 kg (220,000 lbs). It features welded steel construction with hydraulic power steering with a height and tilt-adjustable steering column and AC power steering pump. The drive comprises two 80 Volt AC motors which deliver a maximum torque of more than 1,000 Nm, on wheel gears with an electronic differential lock, guaranteeing optimal traction during poor weather conditions. The batteries have a capacity of 1.550 Ah.