【事件背景】
针对装配BMC软件版本S4.3(PN LIE27L70418AAAP)及以后版本的A320NEO飞机，空客注意到由于AIR BLEED维护信息导致的运行中断逐渐增多，这些AIR BLEED维护信息中，有的带有相关故障信息，有的没有故障信息。
【解决方案与建议】
与“OHDS LOOP INOP”相关的“AIR BLEED”维护状态:
Wing loop: SB 36-1074 (Sep 2017) / MOD 161023 (Sep 2017)
作为最终修复，APU继电器监控逻辑将被更新，以避免在启动APU继电器测试时与BMC之间的不同步，从而导致显示APU继电器故障的虚假II类维护消息。此逻辑更改将包含在软件BMC 4.4中(参见TFU 36.11.00131)。
单独“AIR BLEED”维修状态(无相关故障信息)：
TSM 36-00-00-810-805-A Incorrect Air Bleed Generation for CFM engines
class 3 messages
ground reports
previous leg reports
PFR history in past months
DFDR data with all bleed parameters (P/B positions, valves positons, pressures values)
Last check date:29-APR-2024
ANNEX:
Applicability:
A320neo family fitted with BMC S4.3 (PN LIE27L70418AAAP) and next
Background
On A320FAM neo, Airbus have observed an increase number of Operational Interruption (OI) due to “AIR BLEED” Maintenance Status with or without associated Fault Message (F/M) with BMC SW 4.3.
The aim of this ISI article is to list the mitigations/solutions of the main identified contributors of “AIR BLEED” Maintenance Status associated with or without F/M.
Solution / Recommendation:
“AIR BLEED” Maintenance Status associated with “OHDS LOOP INOP”:
The gold plated connectors have been introduced in production and on in-service aircrafts to prevent the OHDS LOOP INOP fault messages:
APU loop: SB 36-1071 (Aug 2017) / MOD 161010 (May 2017)
Pylon loop (CFM): SB 36-1072 (Aug 2017) / MOD 161978 (Sept 2017)
Pylon loop (PW): SB 36-1073 (Aug 2017) / MOD 161979 (Apr 2018)
Wing loop: SB 36-1074 (Sep 2017) / MOD 161023 (Sep 2017)
Refer to TFU 36.22.00.030
“AIR BLEED” Maintenance Status associated with “(DRIFT) DIFF PRESS XDCR (18HAX)/ SENSE LINE” (PW only):
SB 36-1084 (Dec 2020) / MOD 166564 (Sep 2020) introduce a new DPS sense line orientation, similar to CFM installation
Note: Cleaning/Leak check of DPS sense line and functional test of the DPS are recommended during SB embodiment and during troubleshooting before considering DPS removal
Refer to TFU 36.11.00.117
“AIR BLEED” Maintenance Status associated with “RELAY-APUBV CMND (22HV)/(21HV)”
As mitigation, TSM tasks 36-11-00-810-B27(B28)-A (CFM) // 36-11-00-810-992(993)-A (PW) have been updated since Nov. 2021
As final fix, the APU relay monitoring logic will be updated to avoid the desynchronisation between BMCs at the time to initiate the APU relay test which leads to spurious class II maintenance message indicating APU relay failures. This logic change will be included in the software BMC 4.4 (refer to TFU 36.11.00131)
Refer to ISI 36.12.00012
Orphan “AIR BLEED” Maintenance Status (without F/M)
If orphan AIR BLEED maintenance status is experienced, please refer to the following TSM tasks:
TSM 36-00-00-810-804-A Incorrect Air Bleed Generation for PW engines
TSM 36-00-00-810-805-A Incorrect Air Bleed Generation for CFM engines
For Flight phases 1/2/9/10 (on Ground), if “orphan” confirmed following TSM task, the phenomenon is considered as per design due to interface with CFDIU (ATA-45).
For other Flight phases, investigation has been launched since 2018 to identify the root cause. Several contributors are at the origin of orphan AIR BLEED, some of them has been identified and will be corrected in the software BMC 4.4
For other contributors, the investigation is still on going. Airbus would appreciate being provided with the following data for both BMC units:
class 3 messages
ground reports
previous leg reports
PFR history in past months
DFDR data with all bleed parameters (P/B positions, valves positons, pressures values)
Additional note:
BMC S4.3 is in production since 2017 and retrofitted via SB 36-1078 mandated by EASA AD 2019-0094 with 36 months compliance time from AC date of manufacture. As a matter of fact, since end 2020, every BMC HW should be fitted with BMC 4.3.
Nevertheless, this ISI article is also applicable for:
- BMC S4.1 (PN LIE3AL70418AAAM)
- BMC S4.2 (PN LIE39L70418AAAN)
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