RWY/ACFT LCN - LOAD CLASSIFICATION NUMBER RWY/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. FNobre 02Feb2013
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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.
FNobre 02Feb2013
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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
Pavement thickness:FNobre 02Feb2013
HOW TO FIND AIRCRAFT ESWL / LCN :EXAMPLEHOW TO FIND AIRCRAFT ESWL / LCN :EXAMPLE