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Following diagram is showing mission profile with different phases with mission segment fuel fraction as shown. If crew weight is 150kg, payload of 600kg and empty fraction of 0.495. Determine gross weight of the aircraft.(a) 4430kg(b) 39810kg(c) 4431lb(d) 38910lbThe question was asked during an interview for a job.I need to ask this question from Conceptual Sketch Sizing topic in chapter Conceptual Sketch Sizing of Aircraft Design

Answer» CORRECT choice is (a) 4430kg

Easy explanation: Given crew WEIGHT = 150kg, payload weight = 600kg

Fuel weight fraction Wf / W0 = 1.06[1 – Wx/W0],

Now from fuel fraction method,

Wx / W0 = MULTIPLICATION of each phase fraction

= 0.975*0.98*0.96*0.8*0.96*0.97

= 0.6833

Now,

Wf / W0 = 1.06 * [1 – (Wx / W0)] = 0.3357

Empty weight fraction We / W0 = 0.481

Gross weight of aircraft is,

W0 = Wcrew + Wpayload + Wfuel + Wempty

By re-arranging,

W0 = Wcrew + Wpayload / [1 – (Wf/ W0) – (We / W0)]

= 150 + 600 / [1-0.3357-0.495] = 4430kg


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