RUNWAY

# Runways and connecting taxiways should be arranged so as to-

(a) Provide adequate separation between air craft in the air traffic pattern.
(b) Least interference and delay in landing, taxing and takeoff operations.
(c) Provide the shortest taxi distance possible from terminal area to the end of runway.
(d) Provide adequate taxiway so that landing aircraft can exit the runway as quickly as possible.

# Runway-

(1) Runway Classification

(2) Runway Configuration
(3) Runway Number
(4) Runway Orientation
(5) Runway Obstruction
(6) Runway basic length
(7) Runway corrected length
(8) Runway geometric standard
(9) Runway lighting, marking, signing
(10)Runway pavement design
(11)Runway drainage (Airport drainage)

#Runway Classification:

(1) On the basis of runway marking:

(a) Basic Runway: Runway no. & centre line marking.
(b) Non precision runway: Runway number, centre line, threshold number.
(c) Precision runway: Runway number, centre line, threshold, touchdown zone & aiming point.
(2) On the basis of length: A, B, C, D, E
(3) On the Basis of strength (ICAO): 1, 2, 3, 4, 5, 6, 7
(4) On the basis of use:
(a) Military use
(b) Public use
(c) Public & Military use.
(5) On the basis of precision approach:
(a) Visual
(b) Non precision instrument
(c) Precision instrument

# Runway Configuration:

The term “runway configuration” refers to the number and relative orientations of one or more
runways on an airfield. Many runway configurations exist. Most configurations are combinations of
several basic configurations. The basic configurations are (1) single runways, (2) parallel runways, (3)
intersecting runways, and (4) open-V runways.

(1) Single Runway

This is the simplest of the runway configurations and is shown in Fig. 1. It has been estimated that the
hourly capacity of a single runway in VFR conditions is somewhere between 50 and 100 operations per
hour, while in IFR conditions this capacity is reduced to 50 to 70 operations per hour, depending on the
composition of the aircraft mix and navigational aids available.

Figure 01: Single Runway

(2) Parallel Runways

The capacities of parallel runway systems depend on the number of runways and on the spacing
between the runways. Two, three, and four parallel runways are common. The spacing between parallel
runways varies widely. For the purpose of this discussion, the spacing is classified as close, intermediate,
and far, depending on the centerline separation between two parallel runways. Close parallel runways
are spaced from a minimum of 700 ft (for air carrier airports) to less than 2500 ft. In VFR conditions,
close parallel runways allow simultaneous arrivals and departures, that is, arrivals may occur on one
runway while departures are occurring on the other runway. Aircraft operating on the runways must
have wingspans less than 171 ft (airplane design groups I through IV, see Table 6-2) for centerline
spacing at the minimum of 700 ft. If larger wingspan aircraft are operating on these runways, the
centerline spacing must be at least 1200 ft for such simultaneous operations.
 Figure 2: Example of parallel runway configuration: Orlando International Airport

(3) Intersecting Runways

Many airports have two or more runways in different directions crossing each other. These are referred
to as intersecting runways. Intersecting runways are necessary when relatively strong winds occur from
more than one direction, resulting in excessive crosswinds when only one runway is provided. When the
winds are strong, only one runway of a pair of intersecting runways can be used, reducing the capacity
of the airfield substantially. If the winds are relatively light, both runways can be used simultaneously.
The capacity of two intersecting runways depends on the location of the intersection (i.e., midway or
near the ends), the manner in which the runways are operated for takeoffs and landings, referred to as
the runway use strategy, and the aircraft mix. The farther the intersection is from the takeoff end of the
runway and the landing threshold, the lower is the capacity. The highest capacity is achieved when the
intersection is close to the takeoff and landing threshold. Figure .3 provides an example of intersecting
runways with the intersection closer to the runway thresholds.
Figure 3: Intersecting Runways
(4)Open-V Runways

Runways in different directions which do not intersect are referred to as open-V runways. This
configuration is shown in Fig. 4. Like intersecting runways, open-V runways revert to a single runway
when winds are strong from one direction. When the winds are light, both runways may be used
simultaneously. The strategy which yields the highest capacity is when operations are away from the V
and this is referred to as a diverging pattern. In VFR the hourly capacity for this strategy ranges from 60
to 180 operations per hour, and in IFR the corresponding capacity is from 50 to 80 operations per hour.
When operations are toward the V it is referred to as a converging pattern and the capacity is reduced
to 50 to 100 operations per hour in VFR and to between 50 and 60 operations per hour in IFR.

Figure 4: Example of open-V runways: Jacksonville International Airport

# Runway number:

Runway number is the number printed on the runway landing surface. Indicate the WCB by dropping
last digit of WCB. It helps the pilot & Aircraft personal to find safely and correctly. Each letter is about 60
ft long so that the pilot can see it from top.

0-9 → 00

10-19→01

20-29→02

180-189→18

300-309→30

# Runway Orientation

The orientation of a runway is defined by the direction, relative to magnetic north, of the operations
performed by aircraft on the runway. Typically, but not always, runways are oriented in such a manner
that they may be used in either direction. It is less preferred to orient a runway in such a way that
operating in one direction is precluded, normally due to nearby obstacles. In addition to obstacle
clearance considerations, which will be discussed later in this chapter, runways are typically oriented
based on the area’s wind conditions. As such, an analysis of wind is essential for planning runways. As
a general rule, the primary runway at an airport should be oriented as closely as practicable in the
direction of the prevailing winds. When landing and taking off, aircraft are able to maneuver on a
runway as long as the wind component at right angles to the direction of travel, the crosswind
component, is not excessive.

The FAA recommends that runways should be oriented so that aircraft may be landed at least 95
percent of the time with allowable crosswind components not exceeding specified limits based upon
the airport reference code associated with the critical aircraft that has the shortest wingspan or slowest
approach speed. When the wind coverage is less than 95 percent a crosswind runways recommended.

ICAO specifies that runways should be oriented so that aircraft may be landed at least 95 percent of the
time with crosswind components of 20 kn (23 mph) for runway lengths of 1500 m more, 13 kn (15 mi/h)
for runway lengths between 1200 and 1500 m, and 10 kn (11.5 mi/h) for runway lengths less than 1200
m [1, 2].

Once the maximum permissible crosswind component is selected, the most desirable direction of
runways for wind coverage can be determined by examination of the average wind characteristics at the
airport under the following conditions:

1. The entire wind coverage regardless of visibility or cloud ceiling

2. Wind conditions when the ceiling is at least 1000 ft and the visibility is at least 3 mi
3. Wind conditions when ceiling is between 200 and 1000 ft and/or the visibility is between ½ and 3 mi.

The first condition represents the entire range of visibility, from excellent to very poor, and is termed
the all weather condition. The next condition represents the range of good visibility conditions not
requiring the use of instruments for landing, termed visual meteorological condition (VMC). The last
condition represents various degrees of poor visibility requiring the use of instruments for landing,
termed instrument meteorological conditions (IMC).

The 95 percent criterion suggested by the FAA and ICAO is applicable to all conditions of weather;
nevertheless it is still useful to examine the data in parts whenever this is possible.

# The Wind Rose

The appropriate orientation of the runway or runways at an airport can be determined through
graphical vector analysis using a wind rose. A standard wind rose consists of a series of concentric circles
cut by radial lines using polar coordinate graph paper. The radial lines are drawn to the scale of the wind
magnitude such that the area between each pair of successive lines is centered on the wind direction.

Figure 5: The Wind Rose

A typical wind rose polar coordinate system is shown on the left side of Fig. 7. The shaded area indicates
that the wind comes from the southeast (SE) with a magnitude between 20 and 25 mi/h. A template is
also drawn to the same radial scale representing the crosswind component limits.
# Basic Runway length: It is the length of runway under the following assumed conditions at the airport.

(i) Airport altitude is at sea level.

(ii) Temperature at the airport is standard (15°C)
(iii) Runway is leveled in the longitudinal direction.
(iv) No wind is blowing on runway.
(v) Aircraft is loaded to its full loading capacity.
(vi) There is no wind blowing enroute destination.
(vii) Enroute temperature is also standard.

# Determination of BRL:

Generally 3 cases are considered

1. A normal takeoff where all engines are available and sufficient runway is required to accommodate
variations in liftoff techniques and the distinctive performance characteristics of these aircraft

2. Takeoff involving an engine failure, where sufficient runway is required to allow aircraft to continue
the takeoff despite the loss of power, or else brake to a stop

3. Landing, where sufficient runway is required to allow for normal variation in landing technique,
overshoots, poor approaches, and the like

Figure 6: Declared distances, balanced field concept

Aircraft operators estimate a required field length (FL) for each operation. The field length is generally
made up of three components, namely, the full-strength pavement (FS), the partial strength pavement
or stop way (SW), and the clearway (CL).

Normal takeoff case:

FL1 = FS1 + CL1max

Where

TOD1 = 1.15(D351)

CL1max = 0.50[TOD1 − 1.15(LOD1)]

TOR1 = TOD1 − CL1max

FS1 = TOR1

Engine-failure takeoff case:

FL2 = FS2 + CL2max
Where
TOD2 = D352
CL2max = 0.50 (TOD2 − LOD2)
TOR2 = TOD2 − CL2max
FS2 = TOR2

Engine-failure aborted takeoff:

FL3 = FS + SW
Where
FL3 = DAS
Landing case:
FL4 = LD (2-10)
Where
LD =SD/0.60

FS4 = LD

To determine the required field length and the various components of length which are made up of full-
strength pavement, stop way, and clearway, the above equations must each be solved for the critical
design aircraft at the airport. This will result in finding each of the following values:

FL = max [(TOD1), (TOD2), (DAS), (LD)]

FS = max [(TOR1), (TOR2), (LD)]
SW = [(DAS) − max (TOR1, TOR2, LD)]

Where SW min is zero.

CL = min [(FL − DAS), (CL1max), (CL2max)]

Where CL min is zero and CL max is 1000 ft.

If operations are to take place on the runway in both directions, as is the usual case, the field length components must exist
in each direction.
Example Problem 2-1 Determine the runway length requirements according to the specifications of FAR 25 and FAR
121 for a turbine-powered aircraft with the following performance characteristics:
Normal takeoff:
Liftoff distance = 7000 ft
Distance to height of 35 ft = 8000 ft
Engine failure:
Liftoff distance = 8200 ft
Distance to height of 35 ft = 9100 ft
Engine-failure aborted takeoff:
Accelerate-stop distance = 9500 ft
Normal landing:
Stop distance = 5000 ft

Solution:
For a normal takeoff
TOD1 = 1.15 D351 = (1.15) (8000) = 9200 ft
CL1max = 0.50 [TOD1 − 1.15(LOD1)] = (0.50)[9200 − 1.15(7000)] = 575 ft
TOR1 = TOD1 − CL1max = 9200 − 575 = 8625 ft

For an engine-failure takeoff

TOD2 = D352 = 9100 ft
CL2max = 0.50 (TOD2 − LOD2) = 0.50(9100 − 8200) = 450 ft
TOR2 = TOD2 − CL2max = 9100 − 450 = 8650 ft
For an engine-failure aborted takeoff DAS = 9500 ft

For a normal landing

LD= SD/0.60= 5000/0.60=8333 ft
.
The actual runway component requirements become
FL = max [(TOD1), (TOD2), (DAS), (LD)]
= max [(9200), (9100), (9500), (8333)] = 9500 ft

FS = max [(TOR1), (TOR2), (LD)]

= max [(8625), (8650), (8333)] = 8650 ft

SW = [(DAS) − max (TOR1, TOR2, LD)]

= (9500) − max [(8625), (8650), (8333)] = (9500 − 8650) = 850 ft

CL = min [(FL − DAS), CL1max, CL2max]

= min [(9500 − 9500), 575, 450] = 0 ft

# Correction of BRL for elevation, temperature and gradient:

(1) Correction for Elevation: (ICAO, FAA) 7 % increase for the increase of 300 m elevation above
MSL.
(2) Correction for temperature: (ICAO, FAA) 1% increase for the increase of 1°C rise of airport
reference temperature above the standard atm. Temperature.
Airport ref. temp.= Ta + (Tm-Ta)/3
Where,
Ta = Mean of average daily temperature for hottest month.
Tm = Mean of maximum daily temperature for same month.
Standard temperature at elevation higher than MSL = 15° - 0.0065* Elevation (m)
*Increase of (1) + (2) ≤ 35 % of BRL
(3) Correction for gradient :
FAA recommended that runway length after having corrected for the elevation and temperature
should further increase at the rate 20% for every 1% effective gradients.