Page 163 - Aeronautical Engineer Data Book

136 Aeronautical Engineer’s Data Book
Approach distance
S air � V 2 obs – V 2 TD obs� (L/D)
= + h
2g
where V obs = speed at obstacle, V TD = speed at
= obstacle height, and L/D =
touchdown, h obs
lift-to-drag ratio.
Landing ground roll
2
(W/S) � A (C – µ BRK C L �
D
= ln 1–
S gnd
g (C D –µ BRK C L ) ((F/W)–µ BRK C Lm s )
9.2 Aircraft range and endurance
The main parameter is the safe operating range;
the furthest distance between airfields that an
aircraft can fly with sufficient fuel allowance for
headwinds, airport stacking and possible diver­
sions. A lesser used parameter is the gross still
air range; a theoretical range at cruising height
between airfields. Calculations of range are
complicated by the fact that total aircraft mass
decreases as a flight progresses, as the fuel mass
is burnt (see Figure 9.3). Specific air range (r)
is defined as distance/fuel used (in a short
time). The equivalent endurance term is
specific endurance (e).
General expressions for range and
endurance can be shown to follow the models
in Table 9.2.

Mass

Total mass Unusable and
reserve fuel
Initial mass m 0 Initial fuel mass Fuel m = m(t) Final mass m 1

or
Engines + structure + payload
Distance m = m(x)
Fig. 9.3 Range terminology