Airline Tow Tractor - Baggage/Cargo Factors for Design Consideration
The following methods for the determination of Tractive Effort (TE), Drawbar Pull (DBP), Gross Vehicle Weight (GVW), Engine Torque (T), Engine Brake Horsepower (BHP), and Braking Capacity are presented for the purpose of assisting potential buyers and users of airline baggage/cargo tow tractors in the evaluation of their towing requirements and the capabilities of the various vehicles as offered by the equipment manufacturers.
In this analysis, exception is taken to the more prevalent tractor DBP/GVW formulas (generally used by ATA, SAE, equipment manufacturers, etc.) which were developed primarily for application to aircraft tow tractors. These tractors differ from the smaller baggage/cargo two tractors in that the former utilizes a four-wheel drive traction system and the latter uses only a two-wheel (rear) traction system. In the case of the four-wheel drive system, all of the tractor GVW can be applied for traction purposes (with a consideration for friction and slippage). This is not the case for the two-wheel drive tractor where, for the most part, only portion of the tractor GVW supported by the rear drive wheels can be utilized for traction. This generalization is modified by weight transfer and hitch height as developed in detail in this document. Other factors are also relevant to towing performance and will be discussed in this analysis.