Re: No. of wheels and runways

Date:         29 Nov 97 15:40:01 
Organization: University of Nevada System Computing Services
References:   1 2
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FWIW, here's an extract (P. 5) from the legend of a US FAA
Airport/Facility Directory.  It appears that the matter of aircraft weight
vs. runway strength is delt with by engineering coordination between
aircraft manufacturers, aircraft operators, and airport operators.  There
doesn't appear to be a *reg* per se (but then, I'm only a pilot and
therefore may not be privy to such things).  Anyway, here's what a pilot
can determine from an A/FD:


Runway strength data shown in this publication is derived from available
information and is a realistic estimate of capability at an average level
of activity.  It is not intended as a maximum allowable weight or as an
operating limitation.  Many airport pavements are capable of supporting
limited operations with gross weights of 25-50% in excess of the published
figures.  Permissible operating weights, insofar as runway strengths are
concerned, are a matter of agreement between the owner and user.  When
desiring to operate into any airport at weights in excess of those
published in the publication, users should contact the airport management
for permission.  Add 000 to figure following S, D, DT, DDT, AUW, etc., for
gross weight capacity:

	S--Single-wheel type landing gear, (DC-3), (C-47), (F-15), etc.
	D--Dual-wheel type landing gear, (DC-6), etc.
	T--Twin-wheel type landing gear, (DC-6), (C-9A), etc.
	ST--Single-tandem type landing gear, (C-130).
	SBTT--Single-belly twin tandem landing gear (KC-10).
	DT--Dual-tandem type landing gear, (707), etc.
	TT--Twin-tandem type (includes quadricycle) landing gear
	    (707), (B-52), (C-135), etc.
	TRT--Triple-tandem landing gear, (C-17)
	DDT--Double-dual-tandem landing gear, (E4A/747).
	TDT--Twin-delta-tandem landing gear, (C-5, Concorde).
	AUW--All up weight. Maximum weight bearing capacity for any
	     aircraft irrespective of landing gear configuration.
	SWL--Single Wheel Loading.  (This includes information submitted
	     in terms of Equivalent Single Wheel Loading (ESWL) and Single
	     Isolated Wheel Loading).  SWL figures are shown in thousands
	     of pounds with the last three figures being omitted.
	PSI--Pounds per square inch.  PSI is the actual figure expressing
	     maximum pounds per square inch runway will support, e.g.,
	     (SWL 000/PSI 535).

Quadricycle and dual-tandem are considered virtuallly equal for runway
weight bearing consideration, as are single-tandem and dual-wheel.
Omission of weight bearing capacity indicates information unknown.

The ACN/PCN System is the ICAO method of reporting pavement strength for
pavements with bearing strengths greater than 12,500 pounds.  The Pavement
Classification Number (PCN) is established by an engineering assessment of
the runway.  The PCN is for use in conjunction with an Aircraft
Classification Number (ACN).  Consult the Aircraft Flight Manual or other
appropriate source for ACN tables or charts.  Currently, ACN data may not
be available for all aircraft.  If an ACN table or chart is available, the
ACN can be calculated by taking into account the aircraft weight, the
pavement type, and the subgrade category.  For runways that have been
evaluated under the ACN/PCN system, the PCN will be shown as a five part
code (e.g. PCN 80 R/B/W/T).  Details of the coded format are as follows:

(1)  The PCN NUMBER--The reported PCN indicates that an aircraft with an
ACN equal or less than the reported PCN can operate on the pavement
subject to any limitation of the tire pressure.

(2)  The type of pavement:

(3)  The pavement subgrade category:

(4)  The maximum tire pressure authorized for the pavement:
     W--High, no limit
     X--Medium, limited to 217 psi
     Y--Low, limited to 145 psi
     Z--Very low, limited to 73 psi

(5)  Pavement evaluation method:
     T--Technical evaluation
     U--By experience of aircraft using the pavement

NOTE:  Prior permission from the airport controlling authority is required
when the ACN of the aircraft exceeds the published PCN or aircraft tire
pressure exceeds the published limits.
Whew!  Just for fun, here's some real-world examples (can you tell I've
got *alot* of time on my hands? :) :

KLAX S-175, D-225, DT-400, DDT-900
KSFO S-60, D-200,DT-355,DDT-710
KDEN S-100, D-200, DT-380, DDT-850
KLAS S-23, D-220, DT-633


LTC. Paul Mayer, CAP  UNLV, Las Vegas, NV
ATP, AGI, IGI; former YR F/O (DHC-6-300) and now
Just a Japanese 221 student at UNLV