A calculator may be used. Show intermediate steps in calculation.
For all questions, show the detailed steps of your calculations and derivations, and state
the assumptions made for the equations you are using Continued overleaf
Page 2 of 3.
Q1 A helicopter has a main rotor speed of 260 rpm, and a main rotor radius R=5.90m. The gross take-off weight is 30kN. The blades have an average drag coefficient of CD=0.01, and the rotor solidity =0.08. The distance between the axis of the main and tail rotor is x=7.5m. The helicopter is powered by two turboshaft engines with maximum
continuous power at sea level of P0=1,150kW, each.
(a) Calculate the tail rotor thrust required to trim the helicopter in hover.
(b) Assume that due to a failure in the flight control system there is an impulsive
excess of tail rotor thrust. What happens to the helicopter? Discuss whether the
worst-case scenario is during hover or level flight.
(c) The altitude lapse rate for the engine power is a function approximated by
P(z)=P0 (/sl)1.35. Estimate the hover ceiling of this helicopter rotor, neglecting
the effects of profile and tail rotor power.
Q2 Write a MatlabTM computer program to calculate induced power in level flight. Assume a UK rotor thrust coefficient of CT=0.005, ISA sea-level conditions, and flight at
advance ratio = 0.1. The ki of the rotor can be assumed to be 1.15. The rotor tip-speed
in hover is 220m/s, and the rotor radius is 12m.
You are allowed to make further assumptions if necessary.
