RWY/ACFT LCN - LOAD CLASSIFICATION NUMBERRWY/ACFT LCN - LOAD CLASSIFICATION NUMBER

At some airports the bearing strenght of runway pavement is defined by Load Classification Number (LCN) / Load Classification Group (LCG). The LCN /

LCG has to be determinated for a given aircraft and compared with the specific runway LCN / LCG. Normally, (Pré-arranged exceptions may be allowed by

airport authorities) the PCN / LCG of an aircraft should be equal or below that of the runway on which a landing is comtemplated.

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The Load Classification Number (LCN) method is the former official ICAO method of evaluating

pavement. This method is based on a comparison of two numbers (AIRBUS):

1 - Aircraft LCN (function of landing gear geometry, aircraft weight, CG position, tire pressure and

pavement characteristics)

Aircraft LCN can be obtained in the ACAP (Airport Characteristics for Airport Planning) in section 7-6 for flexible pavements and section 7-8 for rigid pavements.

2 - Pavement LCN

Pavement LCN are published by airport authorities and are available through different sources

(AIP´s, Jeppesen, etc.).

The LCN method uses the notions of ISWL (Isolated Single Wheel Load) and ESWL (Equivalent

Single Wheel Load).

LCN METHODLCN METHOD

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For aircraft having one wheel on each leg, the) Isolated Single Wheel Load (ISWL) is

defined as follows:

ISWLISWL

ISWL = (Aircraft Gross weight) x (% load on main Gear)

2*

*Were 2 accounts fot the number of legs

In the specific case of aircraft having one wheel on each leg, aircraft LCN is the same for rigid and

flexible pavements.

Multi-wheeled legs introduce a complication into the LCN system because of spreading of the load

outside the conditions in which the system was developed. However, this difficulty is solved by

introducing the concept of Equivalent Single Wheel Load (ESWL).

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According to ICAO Aerodrome Design Manual Doc 9157, Ed.1965 – paragraph 4.1.3 “Evaluation

of Aircraft”:

“The ESWL of a particular group of two or more relatively closely spaced wheels is the Isolated

Single Wheel Load which, operating at the same tire pressure as the wheels in the assembly,

produces critical effects in a particular aerodrome surfacing, base, subbase and subgrade,

equivalent to those produced by the group of wheels”

ESWLESWL

Aircraft LCN are different for flexible and rigid pavements in this case.

A310, A319 and A320 have multi-wheeled legs, and use the concept of ESWL instead of ISWL.

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Unless other figures are provided, aircraft LCN are calculated using a “worst case scenario” i.e. at

MRW, max aft CG, standard tires inflated as recommended by the manufacturer.

LCN (and ESWL) can be determined using charts available in the ACAP in section 7-6 for flexible pavements and section 7-8 for rigid pavements.

LCN / ESWL CALCULATIONLCN / ESWL CALCULATION

Note: In order to calculate the aircraft LCN, the following information must be met:

- The pavement thickness for flexible pavements;

- The radius of relative stiffness for rigid pavements.

However, when these parameters are not available, it is common practice to use:

- A standard thickness of 20 inches for flexible pavements.

- A standard radius of relative stiffness of 30 inches for rigid pavements.

Example:

Aircraft type: A319-133 CJ

Max. Ramp Weight: 75500Kg

Tires: 46 x 16 – 20 or 46 x 17 R20

Tire pressure: 14.8 bar

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HOW TO FIND AIRCRAFT ESWL / LCN :EXAMPLEHOW TO FIND AIRCRAFT ESWL / LCN :EXAMPLE

DATA:

Aircraft type: A319-133 CJ

Max. Ramp Weight , MLW, MZFW: 75500Kg, 62500kg, 58500kg

Aircraft Weight variant code: WV002

Tires: 46 X 17 R20

Tire pressure: 13.8 bar ( 200 psi )

Aircraft code: Z

Pavement thickness Flex/Rigid: 20 or 30

Lets take a look how to get all values at the Airbus ACAP (Aircraft Characteristics for Airport Planning)

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ACAP ( AIRCRAFT CHARACTERISTICS FOR AIRPORT PLANNING) :EXAMPLE

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ACFT TYPE/ MRW,MLW / WEIGHT VARIANT:EXAMPLE

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ACFT CODE :EXAMPLEACFT CODE :EXAMPLE

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ACFT TIRES & PRESSURE :EXAMPLEACFT TIRES & PRESSURE :EXAMPLE

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FLEXIBLE PAVEMENT PCN & ESWL :EXAMPLE

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RIGID PAVEMENT PCN & ESWL :EXAMPLERIGID PAVEMENT PCN & ESWL :EXAMPLE

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RESULT ESWL / LCN :EXAMPLERESULT ESWL / LCN :EXAMPLE

DATA:

Aircraft type: A319-133 CJ

Max. Ramp Weight , MLW, MZFW: 75500Kg, 62500kg, 58500kg

Aircraft Weight variant code: WV002

Tires: 46 X 17 R20

Tire pressure: 13.8 bar ( 200 psi )

Aircraft code: Z

Pavement thickness Flex/Rigid: 20 or 30:

Flexible Pavement:

ESWL: 21500Kg

LCN: 76

Rigid Pavement:

ESWL: 23000Kg

LCN: 81

LET´S CONFIRM THIS VALUES (EXAMPLE FLEX PAVEMENT) ON JEPPESEN AIRCRAFT ALINEMENT CHART

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JEPPESEN ACFT ALIGNMENT CHART JEPPESEN ACFT ALIGNMENT CHART

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WHITE FLEET ESWL / LCN WHITE FLEET ESWL / LCN

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2300081215007646x17 R20 / 13.9 , 200759001256A319-133 WV002 (Code Z )

2300081215007646x17 R20 / 13.9 , 200759002675A319-115 WV002 (Code Z )

2300081215007646x17 R20 / 13.9 , 200759002440A319-115 WV002 (Code Z )

2400087220008046x17 R20 / 14.4 , 20977900426A320-211 WV007 (Code N )

2300080220006846x17 R20 / 13.8 , 20073900548A320-214 WV008 (Code J )

2300083250008546x17 R20 / 14.8 , 215157900494A310-304 WV005 (No code)

Tires & Pressure (Bar-Psi)MRW(Kg)MSNAircraft Name

ESWL (Kg)LCNESWL (Kg)LCN

Rigid (30mm)Flexible (20mm)

AIRCRAFT LCN / ESWL

Values at max possible Main Gear Load