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Sir Thomas
10th Mar 2009, 23:03
Hi guys,
Anybody know the LCN for an RJ100?
Thanks!
ST

safetypee
11th Mar 2009, 00:22
IIRC it depends on the type of tyre fitted - high or low pressure; then again there may have been a dual use version. Unfortunately I do not have reliable figures for any of these options.

Sir Thomas
11th Mar 2009, 13:27
Thanks a lot!

OverRun
12th Mar 2009, 03:55
Well, I had to pull some very old textbooks out to calculate this one from basic principles, since I couldn’t find it in any aircraft manuals. Last night, I even found the UK relationship between ESWL and LCN, as well as that of ICAO. As I say below: it is imperative that the user distinguishes between the ICAO standard LCN and the United Kingdom LCG/LCN system.


RJ100 @ max weight 46,039 kgs on 1100 kPa tyres.
Flexible (bitumen) pavement (not concrete or rigid)
Assumption 1: C subgrade (low strength) and pavement t = 24 inches
Assumption 2: B subgrade (medium strength) and pavement t = 20 inches

ICAO METHOD
Assumption 1 (low strength sgde): ESWL = 37750 lbs. LCN = 54
Assumption 2 (medium strength sgde) ESWL = 34500 lbs. LCN = 51

UK METHOD
Assumption 1 (low strength sgde): ESWL = 37750 lbs. LCN = 48
Assumption 2 (medium strength sgde) ESWL = 34500 lbs. LCN = 44

I checked the ICAO method figures with the Super Connie and the 717 at similar weights and tyre pressures and got similar numbers.

One of the difficulties in using the LCN system of pavement ratings is that quantification of allowable aircraft gross weights not only depends on the airplane characteristics, but also pavement thickness (t) for flexible pavements and radius of relative stiffness for rigid pavements. A resulting effect of this feature is that the airplane LCN is dependent upon pavement factors, and consequently it changes from pavement to pavement. This requires that the airplane LCN be published only in the form of a set of charts, and not as a table as is ACN, due to the many combinations of aircraft characteristics and pavement thickness or radius of relative stiffness.

Another system of pavement ratings is the United Kingdom practice, referred to as Load Classification Group (LCG). This system also contains LCN numbers that, although called the same as the ICAO standard LCN, contain values that are different due to a different method of calculation. This requires that when the LCN method is published by an airport authority as a pavement rating, it is imperative that the user distinguishes between the ICAO standard LCN and the United Kingdom LCG/LCN system.

PS - thanks NF for the donation of the old ICAO manuals to my library - wouldn't have done it without them :)