Page 119 - Planning and Design of Airports

88 Airp o r t Pl anning

SW = [(DAS) − max (TOR , TOR , LD)]
1 2
= (9500) − max [(8625), (8650), (8333)] = (9500 − 8650) = 850 ft

CL = min [(FL − DAS), CL , CL ]
1max 2max
= min [(9500 − 9500), 575, 450] = 0 ft
The above regulations, as illustrated in Example Problem 2-1, are
applied at all airports, in the form of declared distances for each run-
way [1, 9]. Declared distances are the distances that are declared
available and suitable for satisfying the takeoff run, takeoff distance,
accelerate-stop distance and landing distance requirements of air-
craft. Four declared distances are commonly reported for each run-
way. They are the takeoff run available (TORA), takeoff distance
available (TODA), accelerate-stop distance available (ASDA), and
landing distance available (LDA).
The takeoff run available (TORA) is the runway length declared
available and suitable for the ground run of an aircraft during take-
off. For Example Problem 2-1, the TORA would be 8650 ft. The takeoff
distance available (TODA) is the takeoff run available plus the length
of any remaining runway and clearway beyond the far end of the
takeoff run available. For Example Problem 2-1, the TODA would be
9500 ft. The accelerate-stop distance available (ASDA) is the amount of
runway plus stopway declared available and suitable for the accel-
eration and deceleration of an aircraft during an aborted takeoff. For
Example Problem 2-1, the ASDA would also be 9500 ft. The landing
distance available (LDA) is the runway length available and suitable
for landing an aircraft. For Example Problem 2-1, the LDA would be
8650 ft.
It is apparent that both the takeoff distance and accelerate-stop
distance will depend on the speed the aircraft has achieved when an
engine fails.
Since, for piston-engine aircraft, full-strength pavement was nor-
mally used for the entire accelerate-stop distance and the takeoff dis-
tance, it was the general practice to select V , so that the distance
1
required to stop from the point where V was reached was equal to
1
the distance (from the same point) to reach a specified height above
the runway. The runway length established on this basis is referred to
as the balanced field concept or balanced runway and results in the
shortest runway. For turbine-powered aircraft, the selection of V on
1
this basis will not necessarily result in the shortest runway if a clear-
way or a stopway is provided.
From an airport planning perspective, it is not typical to design a
runway’s full-strength pavement, stopway, and clearway based on a
given aircraft. Rather, for each individual aircraft operation, a V
1
speed is selected which best accommodates the runway on which it
will be operating.