ce415_lec_2_4
TRANSCRIPT
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Aircraft Characteristics
Type of Propulsion
Size of Aircraft
Minimum Turning Radius
Minimum Circling Radius Speed of Aircraft
Capacity of Aircraft
Aircraft Weight and Wheel Configuration Jet Blast and Noise
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Type of Propulsion Propeller driven Piston Engine (P)
Thrust is generated by propeller which is powered by gasoline fed
reciprocating engine (Cesna Aircrafts) Turbo Prop (TP)
Thrust is generated by propeller which is powered by turbine engine. Itsturbine uses almost all the engine's energy to turn its compressor andpropeller, and it depends on the propeller for thrust, rather than on thehigh-velocity gases going out of the exhaust. (ATR, Dornier)
Turbo Jet (TJ) Dont depend on propeller for thrust. Thrust is directly obtained from
turbine engines (Concorde)
Turbo Fan (TF)
Similar to turbo jet, but with a small fan attached to the turbine engine.The fan causes more air to flow around (bypass) the engine. Thisproduces greater thrust and reduces specific fuel consumption. Thispropulsion system is the most efficient. (most of the present dayprincipal transport aircrfats Airbus, Boeng, McDonnell-Douglas)
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Turbo Prop
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Turbojet
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Turbo Fan
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Size of Aircraft Wing span
Distance between two wing tips. Determines separation clearance
between two parallel taxiways, size of gates, turning radius, etc. Fuselage length
The overall length of aircraft from tip of nose to the tail. Determines sizeof gate, turning radius, etc.
Height
Determines the vertical clearances required in hangar and other serviceareas
Wheel base Centre to centre distance between nose gear and landing gear.
Determines the minimum turning radius
Wheel tread / Outer main gear wheel span The centre to centre distance between the two landing gears is wheel
tread. The outer to outer distance between the two landing gears isouter main gear wheel span.
These dimensions effect the minimum turning radius, width of taxiway,etc.
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Size of Aircraft (B-747)
Height
Wing span
Fuselage Length
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Minimum Turning Radius This dimension is important for establishing the
geometry of movement of the aircraft. The exact position of the aircraft adjacent to theterminal building and the path of the aircraft atother locations is determined based on the
turning radius. Turning radius is a function of nose gear turning
angle (caster angle). The maximum turningangle varies between 600 800.
However, while working out minimum turningradii, moderate caster angle (50) is used tominimize the wear and tear of nose gear.
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Determining Minimum Turning Radius
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Minimum Circling Radius
This is the minimum radius with which
aircraft can take turn in space.
Depends on type of aircraft, air traffic
volume, weather condition, etc. Determines the spacing between two
airports
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Typical Values for MinimumCircling Radii
Small general aviation aircrafts
operating under Visual Flight Rules Bigger aircrafts operating under
Visual Flight Rules
Piston Engine aircrafts operatingunder Instrument Flight Rules
Jet Engine aircrafts operating under
Instrument Flight Rules
1.6 km
3.2 km
13 km
80 km
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Speed of Aircraft Speed of aircraft is measured either with respect
to ground (termed as cruising speed or groundspeed) or relative to wind (termed as air speed)
Speed of aircraft is reported in Nautical Miles per
hour (1 nautical mile = 1.85 km) Approach speed, touchdown speed, exit speed
and allowable deceleration values determine the
location and design of exit taxiways.
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Aircraft Weight Operating Empty Weight (OEW)
Weight of aircraft excluding payload and fuel, but including crewand necessary gear required for flight
Zero Fuel weight (ZFW) The weight above which all additional weight must be in terms of
fuel, so that, when the aircraft is in flight, the bending momentsat the junction of wing and fuselage do not become excessive.
Payload This is the total revenue producing load: passengers + baggage
+ mail + cargo
Maximum Structural Payload The maximum payload the aircraft is certified to carry.
Theoretically, Maximum Structural Payload = ZFW - OEW Actual payload often is less than this as much of space is
occupied by seats, etc.
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Aircraft Weight Contd. Maximum Ramp Weight
This is the maximum total weight of the aircraft authorised for ground
maneuver Maximum Structural Takeoff Weight
The maximum weight of the aircraft authorised at brake release fortakeoff. It excludes taxi and run-up fuel and includes, OEW, payloadand trip and reserve fuel.
Thus, the difference between ramp weight and takeoff weight isnominal.
Maximum Structural Landing Weight This is the weight for which the landing gear is designed. The total
weight of the aircraft can not exceed this while landing. Maximumstructural landing weight is less than the maximum structural takeoff
weight as aircraft loses weight en route by burning fuel. In case of abortive takeoff, the fuel is jettisoned so as not to exceed the
maximum structural landing weight
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Gear Configuration Aircrafts are supported by a nose gear and two main
landing gears located on the wing area on each side.
The distribution of the load between the main gears andthe landing gear depends on the type of aircraft and thelocation of the centre of gravity of the aircraft
However, for pavement design it is normally assumedthat 95% of the weight is supported on the two landinggears.
Maximum ramp weight is used while working out the
distribution of load for pavement design purposes.
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Gear Configurations
Single wheel Dual wheel
Dual-in-tandem
Double dual-in-tandem
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Gear Configuration Contd. Single wheel
Small aircrafts (Douglas DC-3)
Dual wheel
B 737, B 727 Dual-in-tandem
A300, A310, A320, B701, B720B, B757, B767
Double Dual-in-tandem
B747A, B747B
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Payload Vs Range Range of an aircraft is the maximum distance it can fly satisfying the
norms relating to reserve fuel and the maximum weight
characteristics. When the aircraft is loaded to its maximum structural payload (PA),the fuel tanks can not be completely filled to satisfy the requirementof maximum structural takeoff weight limiting the range (say to RA).
In order to maximise the range (say to RB), the payload has to be
reduced (say to PB) giving way for additional fuel filling the fuel tankscompletely. When the aircraft is not on a passenger flight, the requirements of
reserve fuel will not apply. The range worked out by consideringmaximum trip fuel and reserve fuel under zero payload is termed asferry range (RC).
The payload vs range curves are given by the manufacturer. Thesecurves are useful in the planning of airport.
Using these curves the exact weight characteristics of the aircraftscan be obtained by knowing their scheduled operations.
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Typical Payload versus Range Curve
0
5000
10000
15000
20000
25000
30000
35000
40000
0 1000 2000 3000 4000 5000 6000 7000
Range, Nautical miles
Payload,
kg
(RA, PA)
(RB, PB)
(RC, PC)
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Weight characteristics of an aircraft
34232 kgFuel capacity
25878 kgMaximum structural payload
56982 kgOperating empty weight
82860 kgZero fuel weight
89892 kgMaximum structural landing weight
99880 kgMaximum structural takeoff weight
Reserve fuel requirement: 1.25 hr in en route service
Average route speed: 869 km/hr
Average fuel burn rate: 6.43 kg/km
Prepare payload versus range relationship
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Other Aircraft Characteristics Capacity of aircraft determines the facilities with in and
adjacent to the terminal building. It also determines the
range of the aircraft Noise created by the aircraft influences the decisions on
airport layout and capacity. The noise contours are superimposed on the land use
map of the airport to get a noise footprint. Thesefootprints are used in optimizing the runway layoutsminimizing the adverse effect on the surroundingcommunities.
Jet blast of aircraft influences the design of blast pads atrunway ends and the parking configurations adjacent tothe terminals.
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Basic Runway Length Basic runway length is the length of runway
required based on the imposed performancerequirements of the critical aircraft understandard conditions
Basic runway length has to be determined forthe following three general cases Normal landing case
Normal Takeoff case
Engine failure case Continued takeoff
Aborted takeoff (Engine failure accelerated stop)
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Runway Components The three basic components of runway are:
Full strength pavement (FS)
Clearway (CL) Stopway (SW)
Full strength pavement should support the full weight of
the aircraft Clearway is a prepared area beyond FS, clear of
obstacles (max slope is 1.25%), allowing the aircraft toclimb safely to clear an imaginary 11 m (35) obstacle.
Stop way is a paved surface that allows an aircraftoverrun to take place without harming the vehiclestructurally (cannot be used for takeoff)
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Stopway
Direction of operation
Departure end
of runway
Stopway
Source: FAA AC: 150/5300-13 (1989)
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Clearway
Direction of operation
Departure end of runway
Maximum Upward
Slope (1.25%)
150m
ClearwayLength
Clearway
Source: FAA AC: 150/5300-13 (1989)
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Runway ComponentsEach runway end has to be considered individually for
runway length analysis
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Nomenclature FL = field length (total amount of runway needed)
FS = full strength pavement distance CL = clearway distance
SW = stopway distance
LOD = lift off distance
TOR = takeoff run
TOD = takeoff distance
LD = landing distance
SD = stopping distance D35 = distance to clear an 11 m (35 ft.) obstacle
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Normal Landing Case Pilot approaches with proper speed and crosses the threshold of
the runway at a height of 15m
The demonstrated distance to stop an aircraft should be within 60%
of landing distance
LD = 1.667 * SD
FSland = LD
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Normal Takeoff Case The length of runway depends on
Lift off distance (LOD) Distance to reach a height of 35 feet (~11 m) (D35)
Take of Distance (TOD) is taken as 1.15 times the D35
The entire length of TOD need not be of full strength pavement.
The regulations permit the use of Clearway at the end of fullstrength pavement
Clearway Length (CL) = 0.5(TOD-1.15LOD)
The full strength runway, which is TOD-CL, is alsotermed as Take off Run (TOR)
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Normal Takeoff Case
RELATIONSHIPS:
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Engine Failure Continued
Takeoff Case Engine failure continued takeoff
TOD and LOD will be longer than those in normaltakeoff case
TOD is taken as D35 with no percentage applied
Regulations permit the use of clearway at the end Length of Clearway (CL) is half the difference
between TOD and LOD
FS = TOR = TOD-CL
FL = FS + CL
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Engine Failure Aborted
Takeoff Case The length of runway should be sufficient to
bring the plane to a stop
The distance required by an aero plane foraccelerating, decelerating and coming to a stop,in such a situation, is termed as Distance to
Accelerated Stop (DAS) For piston engine aircrafts, full strength
pavement is used for the entire DAS
For turbine engine aircrafts, regulations permitthe use of Stopway for portion of DAS beyondTOR.
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Engine Failure Case
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Example Problem Determine the runway length requirements according to the
specifications for a turbine powered aircraft with the following
performance characteristics: Normal Landing:
SD = 2540 m
Normal Takeoff:
LOD = 2134 m
D35 = 2438
Engine Failure Continued Takeoff:
LOD = 2500 m
D35 =2774 m
Engine Failure Aborted Takeoff:
DAS = 2896 m
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Solution Normal landing:LD = 1.667*SD = 1.667*1524 = 2540 m
Normal takeoff:
TOD = 1.15 (D35) = 1.15*2438 = 2804 mCL = 0.5(TOD-1.15LOD) = 0.5(2804-1.15*2134) = 175 m
TOR = TOD CL = 2804 -175 = 2629 m
Engine failure take off:
TOD = D35 = 2774 mCL = 0.5(TOD-LOD) = 0.5(2774-2500) =137 m
TOR = TOD CL = 2774 137 = 2637 m
Engine failure aborted take off:
DAS = 2896 m
Summary:FL =max (LD, TOD, DAS) = 2896 m
FS = max (TOR, LD) = 2637 m
SW = (DAS FS) = 259 m
CL = FL (FS+SW) = 2896 2896 = 0
259 m2637 m259 m
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Environs at the Airport Basic runway length is valid under the following
assumed conditions at the airport Altitude is at sea level
Temperature at the airport is standard
Runway is level in the longitudinal direction No wind is blowing on runway
Aircraft is loaded to its full loading capacity
No wind is blowing en route to the destination En route temperature is standard
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Corrections to Basic Runway Length
The basic runway length is corrected for
the actual conditions at the airport
The following corrections are applied:
Correction for elevation Correction for temperature
Correction for gradient
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Correction for Elevation High altitudes reflect low air densities, resulting in lower output of
thrust.
Therefore, higher the altitude the longer the runway required.
The increase in runway length with altitude is not linear and it varieswith weight and temperature.
The rate of increase at higher altitudes is higher than at loweraltitudes.
ICAO, however, recommends that the basic runway length shouldbe increased at the rate of 7% per 300 m rise in elevation above
mean sea level. There is exception for high temperature and high altitude areas,
where the increase could be up to 10%.
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Correction for Temperature
Higher temperatures reflect lower air densities resultingin lower out put of thrust.
Therefore, higher the temperature the longer the runwayrequired.
The increase in runway length with temperature is notlinear.
The rate of increase at high temperatures is greater thanat lower temperatures.
ICAO, however, recommends that the base runway
length after having been corrected for elevation, shouldbe further increased at the rate of 1% for every 1oC riseof airport reference temperature above the standardatmospheric temperature at that elevation.
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Airport Reference TemperatureIf,
T1 = Mean of the mean daily temperaturesfor the hottest month
T2= Mean of the maximum dailytemperatures for the hottest month
Then, airport reference temperature (T) is
found out asT = T1 + (T2T1)/3
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Standard Atmospheric
Temperature The standard temperature at mean sea
level is 15o
C. The temperature gradient of the standard
temperature from the mean sea level to
the altitude at which the temperaturebecomes -15.5oC is 0.0065oC per metre.
The temperature gradient becomes zero at
the elevation above the altitude at whichthe temperature is -15.5oC.
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Check for Correction The total correction in basic runway length
for elevation and temperature should notexceed 35%.
If this correction exceeds 35% furtherchecks are needed using model studies.
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Correction for Gradient If the runway is on gradient, the aircraft
has to overcome the grade resistance. More runway length is required to achieve
the required speed for liftoff.
Studies indicate that the runway lengthvaries linearly with the gradient.
Airport design criteria limits the runwaygradient to a maximum of 1.5%
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Effective Gradient For applying correction to runway length for
gradient, FAA uses effective gradient. Effective gradient is defined as the maximum
difference in elevation between the highest and
the lowest points of runway divided by the totallength of runway.
Effective gradient = (h4 h3)/L
L
h1 h2 h3
h4
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Correction for Gradient FAA recommends that the runway length
after having been corrected for elevationand temperature should be furtherincreased at the rate of 20% for every 1%
effective gradient.
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Example Problem Determine the actual length of runway to be provided for the following data
Basic runway length: 1500 m
Elevation of the runway: 110 m +MSL Mean of average daily temperatures for the hottest month: 18oC
Mean of maximum daily temperatures: 30oC
The construction plan includes the following data:
-0.31800 - 2100
-0.51500 18001.0900 1500
-0.3300 900
0.50 300
Gradient (%)Station to Station
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Solution Correction for elevation = (7/100)(110/300)(1500) = 38.50 m
Corrected length = 1500 + 38.50 = 1538.50 m
Correction for temperature:
Standard temperature = 15 0.0065110 = 14.2850C
Airport reference temperature = 18+(30-18)/3 = 220C
Correction = 1538.5(22-14.285) (1/100) = 118.7 m Corrected length = 1538.5 + 118.7 = 1657.2 m
Check for elevation and temperature correction
Increase in runway length = (1657.2-1500)/(1500/100) = 10.48%
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Solution Contd. Correction for gradient
Station 0 300 900 1500 1800 2100
Elevation 100 101.5 99.7 105.7 104.2 103.3
Effective gradient = [(105.7 99.7)/1657.2] 100 = 0.362%
Correction = 1657.2 (0.362 20)/100 = 120 m
Corrected length = 1657.2 + 120 = 1777.2 m
Actual runway length at the airport = 1780 m.
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Airport Configuration Airport configuration is defined as the number
and orientation of runways and the location of
the terminal area relative to the runways. Number of runways depends on air traffic
volume.
Orientation of runways depends on the directionof wind, size and shape of the area and land useand airspace use restrictions in the vicinity ofairport.
The terminal building should be located so as toprovide easy and timely access to runways.
Analysis of Wind for
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Analysis of Wind for
Orienting Runways Runways are oriented in the direction of
prevailing winds.
The data on the parameters of wind namely,intensity (speed), direction and duration areessential to determine the orientation ofrunways.
High intensity winds perpendicular to thedirection of runway cause wobbling effect andcause problems during landing and takeoff of
aircrafts. Smaller aircrafts are particularly effected bythese crosswinds.
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Analysis of Wind Cross wind component
The component of wind intensity perpendicular to the centre line
of runway is termed as cross wind component. Allowable cross wind component
This is the maximum cross wind component that is safe foraircraft operations. This depends on the size of aircraft, wing
configuration and the condition of the pavement surface. ICAO guidelines on cross wind component
18.5 km/hr1500
ACW Component (km/hr)Runway Length (m)
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Analysis of Wind Wind coverage
The amount of time in an year during which the cross wind component
is less than the allowable cross wind component FAA specifies that the system of runways at an airport should be
oriented in such a way to give at least 95% wind coverage.
If it is not possible to achieve the specified wind coverage with onerunway, a cross wind runway should be provided to achieve the same.
Calm Period
Percentage of time during which wind intensity is less than a small
value of wind speed (say 6.5 km/hr) which will not effect the operations.
Wind rose
A diagram where in the direction, duration and intensity are graphicallyrepresented.
Typical Wind Data for Wind Rose
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Typical Wind Data for Wind Rose
(Source: Horonjeff and Mckelvey,1993)
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Collection of Wind Data The wind information that is used in the analysis should be latest
and should accurately represent the situation. Preferably, wind data for the last 10 consecutive years should be
collected for carrying out the analysis. Wind data records for durations less than 10 years may be utilized
with caution. In some instances, it may be highly desirable to obtain and
assemble wind information for periods of particular significance. Indian Meteorological Departmentis the source for the collection of
wind data in India. FAA specifies that the wind summary for the airport site should be
formatted with the standard 36 wind quadrants and usual speedgroupings (0-4; 4-7; 7-11; 11-17; 17-22; 22-28; 28-34; 34-41; 41-47;over 47 knots)
At least 16 wind quadrants and suitable speed groupings should beused.
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Collection of Wind Data In the absence of wind data for a site, it is permissible to
develop composite wind data using wind information
obtained from two or more nearby recording stations.However, the terrain between the site and the recordingstations should be plain or rolling for developing thecomposite wind data.
In extreme cases, wind data should be collected for atleast one year at the site and the composite wind datafor the site should be prepared my merging the data fromnearby recording stations and augmented with personal
observations. Airport development should not proceed until adequate
wind data are acquired
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Wind Rose Construction
(Source: Horonjeff and Mckelvey,1993)
Graphical Representation of Wind
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Graphical Representation of Wind
Parameters
CWC
CWCV cos
Vsin
V V/
V/ cos
V/sin
Completed Wind Rose
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p
(Source: Horonjeff and Mckelvey,1993)
Wind Coverage of E-W Runway
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g y
(Source: Horonjeff and Mckelvey,1993)
WindCoverage =90.8 %
Wind Coverage of CW Runway
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(Source: Horonjeff and Mckelvey,1993)
Wind Coverage =84.8 %
Additional Wind
Coverage = 5.8%
Wind Coverage of the Runway System
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g y y
(Source: Horonjeff and Mckelvey,1993)
Wind Coverageof the runwaysystem = 96.6 %