Landing Field Length (AJT)

Keeping a reserve fuel of 440 lb (200 kg), the landing weight of an AJT is 8,466 lb (wing-loading = 42.26 lb/ft2) and at full flap extended, CLmax = 2.2. Therefore:

Vappr — 1-2Vstall@land — 160ft/s

VtD = 1.1Vstall@land = 146 ft/s

The average velocity from a 50-ft altitude to touchdown = 153 ft/s. The distance covered before brake application after 6 s from a 50-ft altitude:

SG_TD = 6 X 153 = 918 ft

For an aircraft in full braking with qB = 0.45, all engines shut down, and average Cl = 0.5, Cd/Cl = 0.1.

Equation 13.2 for average acceleration is based on 0.7 VTD = 107.1 ft/s. Then: q = 0.5 x 0.002378 x 107.12 = 13.64

Deceleration, a = 32.2 x [(-0.45) – (CLq/42.26)(0.1 – 0.45)] = 32.2 x [-0.45 + (0.15 x 13.64/42.26)] = 32.2 x [-0.45 + 0.0484] = -12.93 ft/s2.

The distance covered during braking, SGLand = (146 x 73)/12.93 = 824 ft. The landing distance SGLand = 918 + 824 = 1,742 ft. Multiplying by 1.667, the rated LFL = 1.667 x 1,742 = 2,904 ft and is expected to be less than the TOFL at an 8-deg flap setting (but not always). This is within the specification of 3,600 ft.

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