Page 90 - Planning and Design of Airports

62 Airp o r t Pl anning

payload and fuel. The OEW of an aircraft is considered for the design
of aircraft that may occupy maintenance hangars, aircraft storage facil-
ities, or any other areas that are not intended to support the weight of
an aircraft when loaded with fuel or payload.
The zero fuel weight (ZFW) is the OEW of an aircraft plus the
weight of its payload. The ZFW is the weight of the aircraft at which
all additional weight must be fuel, so that when the aircraft is in flight,
the bending moments at the junction of the wing and fuselage do
not become excessive. The payload is a term which refers to the total
revenue-producing load. This includes the weight of passengers and
their baggage, mail, express, and cargo. The maximum structural pay-
load is the maximum load which the aircraft is certified to carry,
whether this load be passengers, cargo, or a combination of both.
Theoretically, the maximum structural payload is a difference between
the zero fuel weight and the operating empty weight. The maximum
payload actually carried is usually less than the maximum structural
payload because of space limitations. This is especially true for pas-
senger aircraft, in which seats and other items consume a considera-
ble amount of space.
The maximum ramp weight is the maximum weight authorized for
ground maneuver including taxi and run-up fuel. As the aircraft taxis
between the apron and the end of the runway, it burns fuel and con-
sequently loses weight.
The maximum gross takeoff weight is the maximum weight author-
ized at brake release for takeoff. It excludes taxi and run-up fuel and
includes the operating empty weight, trip and reserve fuel, and pay-
load. The difference between the maximum structural takeoff weight
and the maximum ramp weight is very nominal, only a few thousand
pounds for the heaviest aircraft. The maximum gross landing weight
actually varies with certain atmospheric conditions (namely, air density,
which is a function of field elevation and ambient air temperature).
This is due to the fact that at times of low air density (such as at high
elevations and/or high temperatures), an airplane of a given weight
may simply not have the engine power to get takeoff, while at the
same weight it may be able to at a higher air density, found at lower
elevations and/or lower air temperatures.
The maximum structural takeoff weight (MSTOW), is typically
designed as the maximum gross takeoff weight for an aircraft operat-
ing at sea level elevation at a temperature of 59°F (15°C). It is also the
maximum weight that the aircraft’s landing gear can support. The
MSTOW is the standard design weight measurement used in airport
planning and design.
The maximum structural landing weight (MLW) is the structural
capability of the aircraft in landing. The main gear is structurally
designed to absorb the forces encountered during landing; the larger
the forces, the heavier must be the gear. Normally the main gears of
transport category aircraft are structurally designed for a landing at a