Figure 13.18. Bizjet payload-range capability

speed and altitude is 0.73 lb/hr/ lb. The fuel flow per engine = 0.73 × 563 = 411 lb/hr; for two engines, it is 822 lb/hr.

From the initial and final cruise weight, the fuel burned during cruise is 3,460 lb. This results in a cruise time of 3,460/(2 × 411) = 4.21 hr (252.5 min) of cruise time in which the distance covered is 4.21 × 0.68182 (the conversion factor from feet to miles) × 677.7 = 4.21 × 462 = 1,945 miles = 1,688 nm.

This mission range just satisfies the requirement of 2,000 nm. The block time for the mission is 5.38 hours and the block fuel consumed is 4,923 lb (2,233 kg). On landing, the return taxi-in fuel of 20 lb is taken from the reserve fuel of 600 lb. The total onboard fuel carried is therefore 4,923 + 600 = 5,523 lb.

The payload-range graph is shown in Figure 13.18. A summarized discussion of the Bizjet design is in Section 13.7.

The fuel tank has a larger capacity than what is required for the design payload range. The payload can be traded to increase the range until the tanks fill up. Further reductions of payload make the aircraft lighter, thereby increasing the range.

13.6 Aircraft Performance Substantiation: Military Aircraft (AJT)

Military aircraft certification standards are different from civil aircraft standards. There is only one customer (MOD) requirement and the design standards vary among countries based on defense requirements. The safety issues are similar in reasoning but differ in the required specifications. It is suggested that readers obtain the regulatory MILSPECS from their respective Ministry or Department of Defense – they are generally available in the public domain. In this book, the procedure to substantiate performance capabilities is the same as for civil aircraft, covered in detail in the previous section.

13.6.1 Mission Profile

The fuel load and management depends on the type of mission. Military aircraft mission profiles are varied. Figure 13.19 shows a typical, normal training profile used to gain airmanship and navigational skills in an advanced aircraft.