Page 108 - Planning and Design of Airports

78 Airp o r t Pl anning

D A
P a

Payload E

B
P b

C
R d R a R e R b R c
Range
FIGURE 2-8 Typical relationship between payload and range.

fuel, represents the farthest distance, R , an aircraft can fly if its fuel
b
tanks are completely filled at the start of the journey. The correspond-
ing payload that can be carried is P . To travel the distance R , the
b b
aircraft must take off at its maximum structural takeoff weight.
Therefore to extend the distance of travel from R to R the payload
a b
has to be reduced in favor of adding more fuel. Point C represents
the maximum distance an aircraft can fly without any payload.
Sometimes this is referred to as the ferry range and is used, if neces-
sary, for delivery of aircraft. To travel this distance R , the maximum
c
amount of fuel is necessary, but since there is no payload, the takeoff
weight is less than maximum. In some cases the maximum structural
landing weight may dictate how long an aircraft can fly with a max-
imum structural payload. If this is the case, the line DE represents
the trade-off between payload and range which must occur since the
payload is limited by the maximum structural landing weight.
The shape of the payload versus range curve would then follow the
line DEBC instead of ABC. Payload versus range depends on a
number of factors such as meteorological conditions en route, flight
altitude, speed, fuel, wind, and amount of reserve fuel. For perform-
ance comparison of different aircraft in an approximate way the pay-
load range curves are usually shown for standard day, no wind, and
long range cruise.
The actual payload, particularly in passenger aircraft, is normally
less than the maximum structural payload even when the aircraft is
completely full. This is due to the limitation in the use of space when
passengers are carried. For computing payload, passengers and their
baggage are normally considered as 200 lb units.
The aircraft manufacturers publish payload versus range dia-
grams in aircraft characteristics manuals for each aircraft which may
be used for airport planning purposes. These diagrams are most