Testing Site Suitability; Verifying An Existing Swinging Base - barfield SC 063 User Instruction Manual

2. TESTING SITE SUITABILITY

Before actually attempting to check and calibrate an Aircraft Compass, the area to be used
should be tested. It is recommended that the area be as far as possible from any magnetic
disturbance. Suggested distances are 50 feet from the Aircraft being swung and 100 feet
from any buildings, large items of machinery, power lines, fences, etc. However, the area
could appear to meet all of these requirements, but be unusable because of the steel mesh
in the ramp or underground cables or pipelines.
satisfactory, proceed as follows:
A. Assure that the area is at least 100 feet in diameter or adequate to accommodate
dimensions of aircraft being tested.
B. Check that from any point within the chosen area, a prominent object, at least a mile
distant, can be observed.
C. Remove all magnetic personal items that could affect the Compass.
D. From at least 8 points approximately equidistant on the perimeter of the chosen 100
foot diameter, observe the distant object(s) and note the Sight Compass reading(s).
E. If all reading(s) are consistent within 1 degree, the area is satisfactory for Compass
swinging. However, the area should be rechecked frequently for possible magnetic
charges.
In general an area can be checked for Compass swinging suitability by taking bearings with
the SC 063 from random positions within the area in question on an object at least a mile
distant. If all bearings are the same, the area is suitable for use.

3. VERIFYING AN EXISTING SWINGING BASE

To check an existing base, the operator aligns himself successively with the marked lines on
the base, (standing at least 50 feet from the base) and sights along the line being checked
with the SC 063 hand held Sight Compass. If the bearings taken agree with the markings
on the base, or the markings plus or minus 90 degrees (in cases where the aircraft wheels
are placed on the line), the base is satisfactory. If a constant difference between the
measured bearings and the markings of the lines exists, the lines on the base should be
redrawn. If the difference varies, the base is unsuitable for use.
56-101-01200, Rev. D
September / 9 / 2010
SC 063 INSTRUCTION MANUAL
To ascertain if the chosen area is
OPER.
Page 10 of 20