I am defining the airport facilities as the strength of its pavements and the sophistication of its passenger and baggage loading and aircraft handling provisions.

To illustrate the effect of pavement strength on design, I have taken two representative sizes of aircraft, 50 000 lb (23 Mg) and 300 000 lb (136 Mg) AUW, and shown in Fig. 1 the effect on undercarriage volume of meeting various values of load classification number (LCN) with appropriate variations of tyre pressure and wheel spacing. The smaller machine has twin wheels while the larger has a four-wheel, twin-tandem bogie. The advantage to the designer of being able to work to a high LCN lies not only in the reduced undercarriage stowage volume, but undercarriage weight itself is saved if the wheels can be closely grouped together.