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

For deceleration:

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

knot

ft/s

Vstall @20,600 lb

106.4

179.6

V1 decision speed

109

183.8

V2 = 1.2Vstall at 35-ft height*

128.2

216.5

Vlo at 1.12Vsten**

119.17

201.15

VR at 1.1 Vstall**

117

197.6

Vmu at 1.01 Vr (lower than Vlo)

118.2

199.5

Vmc at 0.94 V1

102

172.2

BFL (ft) (TOFL requirement 4,400 ft)

3,800

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

1st Segment Climb

2nd Segment Climb

35- to 400-ft altitude

400- to 1,000-ft altitude

Pave = 0.00235 lb/ft3

Pave = 0.00232 lb/ft3

0.5pSW = 0.3795

0.5pSW = 0.3747

Flap (deg)

8

20

8

20

MTOM (kg)

20,680

20,680

20,680

20,680

Vstall (ft/s) (knot)

179.6 (106.4)

168.4 (99.8)

179.6 (106.4)

168.4 (99.8)

V2 = (ft/s) (Mach)

216.50 (0.194)

202.08 (0.181)

216.50 (0.194)

202.08 (0.181)

qSw

17,788

15,497.4

17,563

15,301.4

Cl

1.16

1.33

1.177

1.35

CDdean (see Figure 9.2)

0.075

0.100

0.076

0.101

ACD „one „eng

0.003

0.003

0.003

0.003

A CDflap

0.013

0.032

0.013

0.032

ACD-u/c

0.022

0.022

CDlstseg

0.113

0.157

0.092

0.135

Drag (lb)

2,010

2,433

1,616

2,081

Thrust Available (lb)

2,740

2,750

2,740

2,750

Gradient (%)

+ve

+ve

5.4

3.24

FAR

Meets

Meets

Meets

Meets

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.

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