Landing Field Length (Bizjet)
The landing weight of a Bizjet is 15,800 lb (wing-loading = 48.92 lb/ft2) and with full flap extended, it is CLmax = 2.2. Therefore:
The average velocity from a 50-ft height to touchdown = 168 ft/s. The distance covered before brake application after 6 s (may differ) from a 50-ft height:
Sgtd = 6 x 168 = 1,008 ft
An aircraft in full braking with pB = 0.4, all engines shut down, and the average CL = 0.5, CD/CL = 0.1. Equation 13.2 for average acceleration is based on
0. 7Vtd = 110.6 ft/s; then:
q = 0.5 x 0.002378 x 110.62 = 14.54
a = 32.2 x [(-0.4) – (CLq/48.92)(0.1 – 0.4)]
= 32.2 x [-0.4 + (0.15 x 14.54/48.92)]
= 32.2 x [-0.4 + 0.0445] = -11.45
The distance covered during braking, SG0Land = (158 x 79)/11.45 = 1,090 ft. The landing distance SGLand = 1,008 +1,090 = 2,098 ft.
Table 13.16. Bizjet takeoff field length with 8-degflap setting
V1 is too close to Vstall but is acceptable. If required it can be raised by a few knots. * If required, V2 can be higher than 1.2Vstall.
** If required, Vr and Vlo can be at higher speeds.
Table 13.17. First – and second-segment climb performance
Note: Aircraft flap and undercarriage extended, engine at takeoff rating (one engine inoperative). (Use drag polar Figures 9.2 and 9.12 to obtain drag.)
Multiplying by 1.667, the rated LFL = 1.667 x 1,548 = 3,597 ft, within the requirement of 4,400 ft. As expected, this is less than the BFL at an 8-deg flap. This is not always the case because at a 20-deg flap setting, LFL > BFL.