AIRPORT CAPACITY & DELAYS
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AIRPORT CAPACITY & DELAYS
Efficient movement of A/C and passengers between A/Ps is
highly dependent on two key characteristics of an A/P’s ops
Demand for service by
A/C operators &
passengers
Capacity at the A/P,
both in airspace & local
environment
If air traffic demand exceeds A/P or airspace capacity, delays will occur,
causing expense to air carriers, inconvenience to passengers, and
increased workload for the ATC system, A/P employees
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AIRPORT CAPACITY & DELAYS
• Throughout the late 1990s, the overall increase in demand for air
transportation in the US resulted in a growing number of A/Ps that
suffered from delays resulting from demand exceeding capacity
• Within the entire system, over 550,000 air carrier ops suffered from at
least 15 mins of delay each during the year 2000, the year of greatest
delays in the history of commercial aviation
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A
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Reasons for Delay
• There are a number of potential specific reasons for any given A/C to
experience delay
• Majority of flight delays occur because of adverse weather. Other
delays are attributed to equipment, runway closures, and excessive
volume or demand
P
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&
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DEFINING CAPACITY
• Capacity is defined as the practical max number of ops that a system
can serve within a given period of time
• A/P capacity is measured in A/C ops per hour. A single runway at an
airport might have an operating capacity of 60 ops per hour, meaning,
over the course of an hour, the A/P will be able to serve approx 60 A/C
takeoffs and landings
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DEFINING CAPACITY
• There are two commonly used definitions to describe A/P capacity:
throughput capacity and practical capacity
Throughput Capacity
• Defined as the ultimate rate at which A/C ops may be handled
without regard to any small delays that might occur as a result of
imperfections in ops or small random events
• Throughput capacity does not take into account the small probability
that A/C will take longer than necessary to take off, or a R/W close for a
very short period of time
• Throughput capacity is the theoretical definition of capacity and is the
basis for airport capacity planning
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DEFINING CAPACITY
Practical Capacity.
• Number of ops that may be accommodated over time with no more
than a nominal amount of delay, usually expressed in terms of
maximum acceptable average delay
• Such minimal delays may be a result of two aircraft scheduled to
operate at the same time, despite the fact that only one R/W is
available for use, or because an A/C must wait a short time to allow
ground vehicles to cross
• FAA defines two measures of practical capacity to evaluate the
efficiency of airport operations. Practical hourly capacity
(PHOCAP) and Practical annual capacity (PANCAP) are defined
by the FAA as the number of operations that may be handled at an
airport that results in not more than 4 minutes average delay during
the busiest, known as the peak, 2-hour operating period, hourly and
annually, respectively.
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Capacity varies considerably based on a
number of considerations
Utilization of R/Ws
Type of A/C operating, known
as the fleet mix
Percentage of takeoff and
landing ops being performed
FAA
regulations
which
prescribe the use of runways
Ambient climatic conditions
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Physical Characteristics and Layout of R/Ws, T/Ws, & Aprons
are basic determinants of the ability to accommodate various types
of A/C & the rate at which they can be handled. Also important is the
type of equipment, such as instrument landing systems
Configurations of A/P R/Ws may be placed in the following
categories:
• Single runway
• Parallel runways
• Open-V runways
• Intersecting runways
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Single Runway
• Single R/W can accommodate up to 99 ops per hour for smaller A/C
& approx 60 ops per hour for larger commercial service A/C during fair
weather conditions (VMC)
• Under poor weather conditions (IMC), the capacity of a single R/W
configuration is reduced to between 42 to 53 ops per hour, depending
primarily on the size of the A/C using navigational aids that may be
available
• In general, A/P capacity is usually greatest in VMC, whereas IMC, in
the form of fog, low cloud ceilings, or heavy precipitation, tends to
result in reduced capacity
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Parallel Runway
• Parallel R/W configuration (two or more R/Ws) increases R/W
capacity depending primarily on the distances between the parallel
R/Ws
• For two parallel R/Ws separated by at least 4,300 ft, total R/W
capacity is double that of the capacity of a single R/W
• However, if the lateral separation is less than 4,300 ft, then under
IFR ops, reduces capacity
• If the parallel R/Ws are separated by less than 2,500 ft, the A/F
must operate as a single R/W configuration under IFR
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Open-V Runway
• Open-V R/W configuration describes two
R/Ws that are not aligned in parallel with each
other; yet do not intersect each other at any
point on the A/F
• R/W oriented into the prevailing winds is
known as the primary R/W, other R/W is
identified as the crosswind runway
• During low wind conditions, both R/Ws may
be used simultaneously. When A/C operate
outwardly from the V, the R/W configuration is
said to be used for diverging ops
• Takeoffs are allowed simultaneously during
divergent ops
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Open-V Runway
• When the R/W configuration is used in a converging manner, landings
tend to be handled simultaneously
• R/W capacity is greater when ops are performed under divergent ops
• Under divergent ops total R/W capacity can reach nearly 200 ops per
hour for smaller A/C & 100 ops per hour for commercial service A/C
• Under convergent ops, capacity rarely exceeds 100 ops per hour for
smaller A/C and frequently less than 85 ops per hour for commercial
service A/C
• When winds are sufficiently strong or when IFR ops are in effect, only
one R/W in the open-V configuration is typically used, reducing capacity
to that of a single R/W configuration
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Intersecting Runway Configuration
• This configuration describes two R/Ws that are not aligned in
parallel with each other and intersect each other at some point on the
A/F
• R/W oriented into the prevailing winds is known as the primary R/W
• Intersecting R/W is identified as the crosswind runway
• During low wind conditions and operating under VFR, both R/Ws
may be used simultaneously in a highly coordinated manner
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Land and Hold Short Operations (LAHSO)
• Under certain specific conditions, A/C may land simultaneously and
independently on intersecting R/Ws
• These ops, known as LAHSO (land and hold short ops), may be conducted
with approval from the FAA and only when there is sufficient R/W length on
each R/W before the intersection of the two R/Ws for each A/C to land and
stop before reaching the intersection
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• Another significant factor in determining A/P capacity is the
consideration of the volume of demand and characteristics of the A/C
• For any given level of demand, the varying types of A/C with respect
to speed, size, flight characteristics, and even pilot proficiency will in
part determine the rate at which they can perform ops
• The distribution of arrivals and departures (grouped or uniformly
spaced, also determine A/P’s operating capacity
• Tendency of traffic to peak in volume at certain times is a function of
the flight schedules of commercial air carriers using an A/P
• For example, at A/Ps that serve as hubs for major air carriers, high
volumes of A/C all arrive in banks and all depart a short time later, after
passengers have transferred from one flight to another to complete
their travel
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• FAA categorizes A/C types by their max T/O weights (MTOW)
• A/C with MTOW less than 41,000 lbs are considered category A/B
or small A/C, A/C with MTOW between 41,000 and 255,000 lbs are
considered category C or large aircraft, and aircraft with MTOW
greater than 255,000 lbs are considered category D or heavy A/C
• For the purposes of estimating R/W capacity, an A/P’s fleet mix is
defined by the percentage of small, large, and heavy A/C that perform
takeoff and/or landing ops over a given period of time on the R/W
Aircraft Fleet Mix Categories
Aircraft Fleet Mix Category
Maximum Takeoff Weight
A, B (Small)
<41,000 lb
C (Large)
41,000–255,000 lb
D (Heavy)
>255,000 lb
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• Capacity of a R/W handling only T/Os (departure capacity)
• Amount of time the A/C requires to start from initial position at the
beginning of the R/W to the time it leaves the R/W environment
allowing another A/C to depart is called an A/C’S runway occupancy
time (ROT)
• Shorter an A/C’s ROT, the greater the number of A/C that can use
the R/W over time, and hence the greater the capacity of the R/W
• In general, smaller and lighter A/C (fleet mix cat. A & B) tend to
require smaller ROT for T/O than larger or heavier A/C (fleet mix cat. C
& D)
• ROTs for departing A/C ranges from approx 30 secs for small A/C to
approx 60 secs for larger and heavier A/C
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• Capacity of a R/W handling only landings (arrival capacity) is a
function of ROT of arriving A/C
• In addition, velocity at which the A/C travels while on approach to the
R/W (A/C’s approach speed), & FAA regulations requiring that A/C
remain at least a given distance behind one another while on approach
to landing (longitudinal separation), are determining factors in arrival
capacity
• In general, smaller and lighter A/C tend to travel at lower approach
speeds than larger and heavier A/C. However, larger A/C create the
need for greater longitudinal separations. As a result of these
characteristics, estimating arrival capacity becomes important analysis
of the various types of aircraft, known as the fleet mix
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• When two aircraft are on approach to a R/W, the longitudinal
separation required between the two A/C is determined by the weight
categories of the A/C in front (lead A/C, & lag A/C)
• As long as both A/C are airborne on approach, these longitudinal
separations must be maintained
• Only exception to this rule is when operating under VFR, small A/C
are required to maintain sufficient separation so that the lag A/C does
not touch down on the R/W before the lead A/C has landed and
cleared the R/W
• Primary reason for these standards is to prevent lag A/C from
experiencing severe wake turbulence as a result of very rough airflow
emanating from the lead aircraft’s wings
Required Longitudinal Separations for Arriving Aircraft to a Single
Runway When Performing under IFR (Distances in Nautical Miles)
Lead/Lag
Small
Large
Heavy
Small
3 NM
3 NM
3 NM
Large
4 NM
3 NM
3 NM
Heavy
6 NM
5 NM
4 NM
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• Delay is defined as the duration between the desired time that an
operation occurs and the actual time the operation occurs
• When A/C depart and arrive “on time,” according to their respective
schedules, A/C is said to have experienced no delay. If an A/C
actually departs an hour after its scheduled departure time, that A/C
is said to have suffered 1 hour of delay
• This delay may have been the result of any number of factors such
as
• A mechanical repair may have been required
• Luggage may have been slow in being loaded
• Weather may have required the A/C wait until conditions
improve
• A/C was one in a large number of A/C that were scheduled to
depart during peak time of day when the capacity of the airfield
was insufficient to accommodate such high demand
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• As Figure show, some amount of delay is often experienced by A/C,
even when levels of demand are significantly less than capacity
• These delays are usually nominal, created as the result of thin
instances of two A/C wishing to operate within very close intervals of
time, or minor operational anomalies
• As demand nears capacity, delays tend to increase
Practical
Capacity
Increase
AVERAGE
DELAY
(minutes)
Throughput
Capacity
Congestive Delay
(Typical 9 minutes)
Maximum Acceptable Delay
(Typical 4 minutes)
DEMAND (Number of Operators)
Increase
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• FAA defines the maximum acceptable level of delay as the level of
demand, in relation to throughput capacity, that will result in A/C
delays of no more than 4 minutes per operation
• Congestive delay occurs when demand is sufficiently close to
throughput capacity to result in an average of nine or more minutes
of delay per A/C operation
• As demand reaches throughput capacity, delays can reach
several hours per operation (weather)
Increase
AVERAGE
DELAY
(minutes)
Practical
Capacity
Throughput
Capacity
Congestive Delay
(Typical 9 minutes)
Maximum Acceptable Delay
(Typical 4 minutes)
DEMAND (Number of Operators)
Increase
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Strategies employed to reduce delays fall into two categories: increasing
system capacity and managing system demand
• Increasing capacity includes addition of new infrastructure (additional runways,
terminal facilities, and ground access roads)
• Provision of technologies and policies to make existing infrastructures operate
more efficiently. For example, it reduces the amount of processing time required at
any given facility to allow more operations over a given period of time.
• Managing demand focuses more on changing the behavior of system users that
in turn will lead to better use of existing system capacity.
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Creating New Airport Infrastructure
Development of new A/Ps & construction of new R/Ws & R/W extensions at
existing A/Ps offers the greatest potential for increasing aviation system
capacity
Converting Military Airfields
• Conversion of military air bases to civil aviation A/Ps can contribute to an
increase in commercial aviation system capacity by allowing the conversion
of closed military A/Fs to civilian use
• Most of the military A/Fs are already designed to accommodate heavy
A/C, with R/WS up to 13,000 ft in length
• Many of these A/Fs are located in the vicinity of congested metropolitan
A/Ps where the search for major new A/Ps has been under way
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