What are the different station numbering
system used in aircraft
numbered in inches from a reference or zero point known as the reference datum.
Aircraft Numbering System is the number of a station tells how many
inches it is from station 0. The reference point is called the datum.
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These systems are used to locate specific wing frames, fuselage
bulkheads, or any other structural member of an aircraft. Several types of
systems are used. Listed below are the numbering systems.
Key points:
Airframe reference data, reference datum line,
aircraft body, fuselage station numbers, body water lines, body buttock lines,
buttock line, wings station numbers, panel numbering, locating access panels,
Cartesian coordinates, reference datum line
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Reference
Datum Line
This is an
imaginary vertical plane located at or near the nose of the aircraft. It is
from this line that all horizontal distances are measured.
Note: Station
numbering are used on large aircraft like transports or tankers:
AIRCRAFT
BODY (FUSELAGE) STATION NUMBERS,
We must have a
starting point when using station numbers. The reference datum line is the
starting point. The reference datum line is near the nose of the aircraft. The
aircraft stations are numbered in inches fore or aft of this line. Most aircraft
components can be located by a station number that specifies the number of
inches the component is located from the reference datum line, as shown in
Figure 1-44. If the component is on the wing the wing station number shows the
number of inches to the right or left of the aircraft centerline that the
component is located.
Figure 1-44,
Fuselage Station Numbers and Water Line Numbers
BODY
WATER LINES,
The reference
for water lines is at some point below the fuselage and is called 0 water line.
Horizontal, parallel lines are then drawn and numbered. The numbers tell how
many inches the lines are from 0 water line.
BODY
BUTTOCK LINES (BUTTOCK LINE),
The body buttock
line is a vertical line is drawn through the center of the fuselage. This line
is called 0 (zero) body buttock line. As illustrated in Figure 1-45, it divides
the fuselage station in half. A series of body buttock lines is then drawn
parallel to the 0 line. They are numbered in the same way as fuselage stations.
A negative number indicates those on the left of the centerline and a positive
number indicates those on the right of the centerline.
Thus, for
components in the main fuselage of the aircraft, these three numbers are
sufficient to exactly define its position in the aircraft. However, if the
component is found along or inside one of the wings, another number is
required. This number is called the wing station (WS) number and is measured
along either wing, beginning at the centerline of the aircraft and moving
outward along the wing. This is also measured in inches.
Figure 1-45, Body
Buttock Lines
WINGS
STATION NUMBERS,
The wings,
nacelle, and tail surfaces are also divided into stations as shown in figure
1-46. Body buttock lines measure horizontal distances at these stations and
vertical distances are measured by water lines.
Figure 1-46,
Wing Station Numbers
Panel
Numbering
LOCATING
ACCESS PANELS,
The best way to
find aircraft components is to first find the access panel or door that will
provide access to the different components. The access panels or doors are
numbered differently on different aircraft. On some aircraft, the access panels
on the left have odd numbers and those on the right side have even numbers. On
other aircraft, the access panels on the right side have an ”R” associated with
the number, while the numbers on the left side have an ”L.” There are other
numbering systems, so you must refer to the –2 TO for the specific aircraft to
find a list of access panels and doors.
Each access door is
numbered and the numbers are listed to show the component to be found behind
each panel or door. See Figure 1-47. Normally, the –2 TO will show which panel
you must open or remove to do a task. Then all you should do is refer to the –2
TO to find out where the panel is located. Not all the components can be found
by locating the access door. Some aircraft parts and components must be found
by the use of aircraft station numbers
Figure 1-47,
Aircraft Panel
CARTESIAN
COORDINATES,
Cartesian
coordinates are used to pinpoint the location and placement of each part on the
airplane, from attachments to major assemblies, using the X, Y, and Z-axis for
planes of reference. See
Figure 1-48.
Figure 1-48, Cartesian coordinates