The 5AT technical specifications have been outlined by David Wardale as follows:
- Maximum axle load: 20 metric tons (same as BR Class 5MT).
- Engine weight in working order: 80 ~ 90 metric tons (the load on the leading bogie will be determined at the detail design stage, hence precise weight cannot now be given).
- Adhesive weight: 60 metric tons.
- Tender weight, full supplies: 80 metric tons.
- Overall engine and tender weight, full supplies: 160 - 170 metric tons.
- Overall length over buffers of engine and tender: 22.1 metres (72 feet 6 inches).
- Tender capacity (assuming oil fuel): fuel 7 metric tons, water 46.3 m3 (10,200 gallons).
- Coupled wheel diameter: 1880 mm (6 feet 2 inches, same as BR Class 5MT).
- Boiler pressure: 2100 kPa (305 psi).