CFM Fuel and Oil Filter Delta Pressure Switch

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CFM Fuel and Oil Filter Delta Pressure Switch

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979199501

Arm Proposed Switch Configuration Current Double Throw Proposed Single Throw Run contact eliminated Introduction Logistics • CFMI/Boeing/Honeywell laun

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February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 1
Fuel and Oil Filter Delta Pressure
Switch
February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 2
Fuel and Oil Filter Delta Pressure Switch
Background / Status
Numerous QA07985 field removals  MTBUR = 42,000 Hrs
36 VIN QA07995 units received @ vendor  MTBUR = 54,000 Hrs
 Calculation uses total time accumulated by Switches introduced on
production engines only  Very pessimistic
 Using time accumulated by all switches delivered to customers
 MTBUR > 80,000 Hrs
Reliability Increasing
February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 3
Investigations
Old Design : QA07985
 85% removals failure modes corrected in VIN QAO7995
– SB 73-042 issued Jan 2000
– Introduced on aircraft delivered since Mar 2000
 15% with no fault duplicated and assumed to be due to micro-switch
erratic indications due to temperature, and vibrations
New Design : QA07995 - 36 units received @ vendor
 5 units (14%) found with contact resistance value out of ATP limit
– Only one high enough to cause switch disagree fault
 21 units (58%) tested and No Fault Found
 No mechanical failure identified
 10 units pending testing
Root Cause Suspected to Be Intermittent Indication
Inherent to Micro-switch Technology
Fuel and Oil Filter Delta Pressure Switch
February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 4
Corrective Action
• Aircraft DDG revised to allow for one (1) flight dispatch allowance prior fuel filter
replacement, provided:
 Fault verified to be in warning system
 No contamination found at filter drain plug
• QA07995 field implementation on-going
• QA07995 failures root cause status
 System tests (accelerated life testing ) with harness and EEC card
– Tests completed with 6 field switches but no failure duplicated
• One hermetic and 3 reed switch prototypes passed engineering qualification
tests
 Go-ahead decision when current design failure root cause will be
demonstrated
• Switch disagree fault logic change under evaluation
 Switch fault to illuminate light at the end of the flight
– No change in the clogging logic
 If launched will be implemented in 7BO software expected by end of 2002
Fuel and Oil Filter Delta Pressure Switch
February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 5
Background / Status
VIN QA07656 - Same technology as the Fuel Filter DP Switch
• 35 reported oil filter bypass light illumination over last 12 month
 12 cases Switch fault reported, and switch replaced
 13 cases NO switch fault reported, but switch replaced
 8 cases NO switch fault reported, and no switch replacement reported
• 34 occurred on ground / 1 in-flight and ground
• 94 units received @ vendor last 24 month  MTBUR = 90,000 Hrs
 72 with contact resistance values above ATP limit
– 34 high enough to set switch disagree fault
• Additional finding
 Crack initiation at red wire solder joint (not separated) on 3 returned units
due to heat shrinkable sleeve being too close to solder
Fuel and Oil Filter Delta Pressure Switch
February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 6
Corrective Action
• Switch assembly procedure to be revised to move red wire heat shrinkable
sleeve away from solder
 Reduce stress applied to the red wire
• Fuel switch disagree fault logic change may be applied to the oil filter system
 Switch Fault to illuminate light at the end of the flight
– No change in the clogging logic
 If launched, will be implemented in 7BO software expected by end of
2002
Fuel and Oil Filter Delta Pressure Switch
February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 7
Summary
• Fuel filter DP switch new design, and oil filter DP switch reliability
increasing towards expectations
• No short term solutions for remaining FFDPS, and OFDPS erratic
indications/ high contact resistance
 Issue inherent to micro-switch technology
• Hermetic and reed switch prototypes could be evaluated if current
design failure root cause demonstrated
• Switch disagree fault logic implementation being evaluated
 In 7BO software (if launched) expected by end of 2002
Fuel Filter DP Switch Reliability Increasing
Oil Filter DP Switch Reliability Meeting Expectations
Fuel and Oil Filter Delta Pressure Switch