# Wing Group Mass

Consider a 10% composite secondary structure; that is:

kmat = (0.9 + 0.9 x 0.1) = 0.99

It has no slat, making ksl. = 1, and without a winglet, kwl = 1. For the spoiler, ksl = 1.001, and for a wing-mounted undercarriage, kuc = 1.002.

SW = 30 m2, nult = 4.125, b = 15 m, AR = 6.75, X = 0.375, fuel in wing, MWR = 1,140kg, Л = 14°, t/c = 0.105, and Vd = 380knots = 703.76kmph = 195.5m/s. The load factor n = 3.8.

Equation 8.21 becomes:

Mw = 0.0215 x 0.99 x 1.002 x 1.001 x (9,500 x 4.125)0 48 x 29078

x 6.75 x (1 + 0.375)0 4 x (1 – 1,140/9,500)a4/(Cos14 x 0.105a4)

Mw = 0.0213 x 1.003 x 160.2 x (13.8 x 6.75 x 1.136) x 0.88a4/(0.97 x 0.406) Mw = 3.42 x 105.8 x 0.95/(0.3977) = 351.8/0.3977 = 864 kg

8.11.1 Empennage Group Mass

For a H-tail, a conventional split tail has a kco„f = 1.0. Consider a 20% composite secondary structure; that is:

kmat = (0.8 = 0.9 x 0.2) = 0.98

MTOM = 9,500 kg, nuit = 4.125, Sht = 5.5 m2 (exposed), AR = 3.5, X = 0.3,

Л = 16°, t/c = 0.105, and VD = 380 knots = 703.76 kmph = 195.5 m/s.

Mht = 0.02 x 0.98 x (9,500 x 4.125)0484 x 5.50 78 x 3.5 x (1 + 0.3)°’4/(Cos16 x 0.10504)

= 0.0196 x 167.1 x 3.8 x 3.5 x 1.11/(0.961 x 0.406) = 47.7/0.39 = 124kg

For a V-tail (T-tail), kconf = 1.1. Consider a 20% composite in a secondary structure; that is:

kmat = (0.8 + 0.9 x 0.2) = 0.98

MTOM = 9,200kg, nuit = 4.125, Svt = 3.5m2(exposed), AR = 2.0, X = 0.5,

Л = 20°, t/c = 0.105, and VD = 380 knots = 703.76 kmph = 195.5 m/s Mvt = 0.0215 x 0.98 x 1.1 x (9,500 x 4.125)0484 x 3.5078 x 2 x (1 + 0.5)04/ (Cos20 x 0.10504)

= 0.02318 x 167.1 x 2.66 x 2 x 1.176/(0.94 x 0.406)

= 23.877/0.382 = 63 kg

Figure 8.5 provides the graphical solution. It reads i/Wf = 0.02 (top line corresponding to span, b = 49.2 ft). Therefore, wing weight i = 22,000 x 3.8 x 0.021 = 1,756 lb = 800 kg, a difference of about 6%.

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