Cowl Thermal Anti-ice Valve Reliability

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February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 1
Cowl Thermal Anti-ice
Valve Reliability
February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 2
Amber NCTAI Light on During Takeoff and Climb
Customer/Fleet Concern
• Several operators have reported amber COWL ANTI-ICE light
coming on during takeoff and climb
 The amber COWL ANTI-ICE light comes on when the
duct pressure down stream of the NCTAI valve is too
high
• Valve repair facility has reported a significant number of
NCTAI valves being returned for COWL ANTI-ICE light on
Cowl Thermal Anti-ice Valve Reliability
February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 3
Engine Nose Cowl Thermal Anti-ice System
Cowl Thermal Anti-ice Valve Reliability
February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 4
NCTAI Valve Regulator Worn
• Repair facility found that over pressure was caused by a worn
reference regulator in the NCTAI valve
• Wear caused by dynamic instability in the regulator
• Instability caused continuous regulator poppet cycling at 250
- 300 Hz. This cycling also causes the valve to “buzz”
• The regulator poppet and seat wears until they will not seat
causing the NCTAI valve to regulate too high
Cowl Thermal Anti-ice Valve Reliability
February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 5
NCTAI Valve Regulator Worn
Wear Wear
Wear
Wear
Very Heavy Deep Wear
Virtually No Wear Wear
Different views of poppet. The poppet is worn all around
Housing split in two to expose the bore. One half has very heavy wear, the other half has virtually no wear.
February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 6
Reference Regulator Will be Replaced
Corrective Action
• Honeywell has tested the NCTAI valve with the reference regulator
used on the pre-cooler valve, bleed air regulator and high stage
regulator for 737-300-900 airplanes
 Valves that buzzed with the original regulator would not buzz
with the new regulator
• Honeywell and Boeing are processing a change to use the
reference regulator from the bleed air regulators and pre-cooler
valve
• Using standard flow, service bulletin is scheduled for release in
August 2002. We will expedite introduction of the improved valve
as much as possible
Cowl Thermal Anti-ice Valve Reliability

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Cowl Thermal Anti-ice Valve Reliability

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