4. Install Sensing Element (401, 402)
CAUTION: IF NEW SENSING ELEMENT IS BEING INSTALLED, CHECK THAT PART NUMBER IS IDENTICAL TO THE ONE THAT WAS REMOVED.
A. Carefully begin to unroll sensing element and locate in approximate position.
CAUTION: SENSING ELEMENT SHALL NOT BE TWISTED, PULLED, OR CLAMPED UNDER TENSION. DO NOT STRAIGHTEN ACCEPTABLE KINKS, BENDS, OR DENTS AS A FATIGUE FAILURE WILL RESULT. SENSING ELEMENT MUST ALWAYS BE ROLLED OR UNROLLED FROM COIL; NEVER PLAY OFF SIDE OF COIL.
B. Remove protective cap from end fitting at one end of sensing element and loosely install end fitting in applicable flange fitting. Bend element to contour of clamps and loosely install other end fitting (Fig. 401).
C. Install silicone rubber bushings on element so that each is centered on mounting clip and slit of each bushing faces outside of nearest bend.
D. Install bushings in each mounting clip. Mounting clips and bushings must fit element snugly.
NOTE: If old sensing element has been left in position as reference, it should be removed at this time.
NOTE: Overheat sensing elements M370 and M371 may have short silicone tubes installed over the elements in critical locations to prevent false overheat annunciation. The tube is slit to fit easily over the element, and it must be secured within the mounting clips and with lacing tape. It is important to position the slit away from the bend in the element.
E. Tighten jamnuts on end fittings. Torque jamnut 50 to 60 pound-inches and lockwire jamnut to flange fitting and end fittings.
NOTE: Check that end fitting hex is inside hex retainer on flange fitting prior to tightening jamnut.
F. Retrace sensing element, taking up and providing slack as necessary.
NOTE: Elements shall clear structure by a minimum of 0.50 inch except at mounting clips. As much clearance as possible is desired from units that are displaced by torque or vibrate. Double check all bends and clearance after securing element. On airplanes incorporating SB 26-1060 which replaced one sensor mounting bracket and modified the route of the sensor, maintain a minimum clearance of 1.0 inch between the sensor and APU bleed air ducts.
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May 01/99 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 26-18-11 Page 403
G. Deleted
H. Install electrical connectors on end fitting and lockwire to flange fitting.
I. Check electrical bond between element connector shell and primary structure per 20-22-01. Resistance should not exceed 0.005 ohm.
J. Test wing and lower aft body overheat detection system (Ref 26-18-0 A/T).
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26-18-11 Page 404 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Oct 20/90
K19126
5E2 M370/M371 Silicone Tube Installation (Typ)
May 01/99 Figure 402 26-18-11
Page 405
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
WING AND LOWER AFT BODY OVERHEAT DETECTION SENSING ELEMENT - ADJUSTMENT/TEST
1. General
A. Attachment of test equipment should be made by using a wire end fitting between the element end fitting and test equipment. Attach the test leads to the center contacts, or the center contacts and outer shell of the wire end fittings. Use of the wire end fittings reduce the possibility of damage to the electrical contact surface and provide a positive attach point for test equipment during test. Extreme care must be taken during the tests to keep end fittings free from dirt and other foreign substances. Replace the electrical connector or protective caps upon completion of the tests.
2. Sensing Element Test
A. General
(1) Sensing loop should be stabilized at ambient temperature prior to test. Replace elements that fail test.
CAUTION: FOR SENSING ELEMENTS NOT IN THE STRUT AREA, OR NOT IN THE WING LEADING EDGE; DO NOT USE A MULTIMETER ON THE SENSOR ELEMENTS IF THE ELEMENT TEMPERATURE IS ABOVE 155°F (68°C). IF THE TEMPERATURE IS BELOW 155°F (68°C), BUT ABOVE 70°F (21°C), LIMIT METER USE TO 5-SECOND APPLICATIONS WITH NO MORE THAN 2 APPLICATIONS PER MINUTE. IF THESE REQUIREMENTS ARE NOT FOLLOWED, DAMAGE TO THE SENSOR ELEMENT MAY OCCUR.
CAUTION: FOR SENSING ELEMENTS IN THE STRUT AREA, OR IN THE WING LEADING EDGE; DO NOT USE A MULTIMETER ON THE SENSOR ELEMENTS IF THE ELEMENT TEMPERATURE IS ABOVE 300°F (149°C). IF THE TEMPERATURE IS BELOW 300°F (149°C), BUT ABOVE 70°F (21°C), LIMIT METER USE TO 5-SECOND APPLICATIONS WITH NO MORE THAN 2 APPLICATIONS PER MINUTE. IF THESE REQUIREMENTS ARE NOT FOLLOWED, DAMAGE TO THE SENSOR ELEMENT MAY OCCUR.
(2) Equipment and Material
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