length at any temperature below 120°F ambient.
NOTE: Element length in inches may be determined from vendor sensing element part number of subtracting 35500 from first five digits of vendor part number.
(c)
Test insulation resistance by connecting multimeter across center conductor and outer shell at either element or fitting. 1) Using R x 1 scale, insulation resistance shall be 50 megohms or greater at any
temperature below 120°F ambient.
(d)
Deleted
(e)
Connect wire end fittings D840 and D842 to sensing element on ceiling of main wheel well. Lockwire end fittings to sensing element.
B. Sensing Element Wire End Fittings Test
(1)
Equipment and Material
(a)
Deleted
(b)
Megohm Bridge, General Radio Model 544B
(c)
Wire End Fitting 35303-11, Fenwal Incorp., Ashland, Mass.
(2)
Prepare Sensing Element Wire End Fittings for Test
(a)
Disconnect wire end fitting D840 and D842 on ceiling of main wheel well.
(b)
Remove compartment overheat control module on rack E3-2 in electrical/electronic equipment compartment.
(c)
Connect wire end fittings to D840 and D842.
(3)
Test Sensing Element Wire End Fittings and Airplane Wiring
(a)
Test insulation resistance by connecting megohm bridge across center conductor and outer shell at wire end fitting D840. 1) Insulation resistance shall be 50 megohms or greater at 500 volt DC when
measured at any temperature below 120°F ambient.
(b)
Deleted.
(c)
Repeat step (a) and (b) for wire end fitting D842.
(4)
Restore Airplane to Normal Configuration
(a)
Remove wire end fittings from D840 and D842.
(b)
Connect wire end fittings from D840 and D842 to sensing element on ceiling of main wheel well. Lockwire end fittings to sensing element.
(c)
Install compartment overheat control module on rack in electrical/electronic equipment compartment.
NOTE: The wire end fittings are to be used for attachment of test equipment to the airplane wiring during test procedures.
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Feb 20/86 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 26-17-11 Page 503
WHEEL WELL OVERHEAT DETECTION SENSING ELEMENT – INSPECTION/CHECK
1. General
A. Physically check each sensing element and electrical connector to determine whether and faults have occurred to make the element unacceptable.
2. Wheel Well Overheat Detection Sensing Element Check
A. Check Wheel Well Overheat Detection Sensing Element
(1)
Check that all diameter variation have smooth contours and that no abrasions or wear spots are deeper than 0.002 inch.
(2)
Check that no section of element has a diameter of less than 0.070 inch.
NOTE: Smoothly contoured dents and kinks which have not reduced tubing diameter beyond acceptable limits are not cause for replacement.
CAUTION: DO NOT ATTEMPT TO STRAIGHTEN ANY ACCEPTABLE DENT OR KINK, AS STRESSES SET UP IN TUBING MAY CAUSE A POSSIBLE FAILURE.
(3)
Check for any radial marks (nicks or gouges) that are more than 0.005 inch deep or extending more than 50% across seal face of end of electrical connectors.
NOTE: These gouges would prevent an adequate water vapor seal from being made when connectors are mated.
(4)
Check for dirt or other foreign substances on seal face of end connectors.
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WING AND LOWER AFT BODY OVERHEAT DETECTION SYSTEM -DESCRIPTION AND OPERATION
General
A. The wing and lower aft body overheat detection system provides overheat detection along the engine bleed air ducts in the left and right wing, along the auxiliary power unit (APU) bleed air duct from the APU installation to the air conditioning distribution bay, and along the ceiling of the air conditioning distribution bay (Fig 1). The detection system is an electrical, heat sensing system that responds to an overheat condition by activating warning lights.
B. Airplanes with Boeing M237 compartment overheat accessory unit:
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