Glossary of Terms

The nomenclature used in the following sections is presented in Tables A.1 and A.2.

A.3 Overall Aircraft

The initial calculation is of the helicopter drag which, together with the weight, will allow the thrust and forward tilt of the main rotor to be determined.

Table A.1 Rotor

Main

Tail

Thrust

Tm

Tt

Blockage factor

B-m

Bt

Tip speed

VTM

VTt

Number of blades

Nm

Nt

Blade chord

Cm

Ctl

Rotor radius

rm

RT

Disc tilt

gS

Thrust coefficient

CTM

Ctt

Advance ratio

am

At

Advance ratio component parallel to disc

mxM

AxT

Advance ratio component perpendicular to disc

fizM

Downwash

2iM

2iT

Profile drag coefficient

CD0M

CD0T

Induced-power factor

kiM

kiT

Induced power

PiM

PiT

Profile power

PPM

PPT

Parasite power

PPARAM

Total power

PTOTM

PTOTT

Drag @100 velocity units

D100

Auxiliary power

Paux

Transmission loss factor

TRLF

Helicopter weight

W

Helicopter drag

D

Table A.2 Overall helicopter

Drag can be specified in several ways; however, the method described here uses the drag force at a reference speed of 100 units (D100) at ISA sea-level air density as a basis. (This calculation can be readily adapted to any other specification of drag.) The drag of the helicopter is then calculated by factoring the D100 value with the square of the forward speed and linearly with respect to the air density, as follows:

s (A1)

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