Airworthiness Directive · Amendment 39-18400 · Air distribution system
The Boeing Company Airplanes
This AD applies to all The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes, certificated in any category.
We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD was prompted by a determination that a repetitive test is needed to inspect the components on airplanes equipped with a certain air distribution system configuration. This AD requires doing repetitive testing for correct operation of the equipment cooling system and low pressure environmental control system, and corrective actions if necessary. This AD also requires, for certain airplanes, installing new relays and doing wiring changes to the environmental control system. We are issuing this AD to detect and correct latent failures of the equipment cooling system and low pressure environmental control system, which, in combination with a cargo fire event, could result in smoke in the flight deck and/or main cabin, and possible loss of aircraft control.
At the applicable times specified in paragraph (g)(1) or (g)(2) of this AD, do a test for correct operation of the smoke clearance mode of the equipment cooling system and low pressure environmental control system, and do all applicable corrective actions, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-26A1137, dated May 22, 2014. Do all applicable corrective actions before further flight. Repeat the test thereafter at intervals not to exceed 9,000 flight hours.
(1) For airplanes other than those identified in paragraph (g)(2) of this AD: At the applicable times identified in paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-26A1137, dated May 22, 2014, except as required by paragraph (i) of this AD.
(2) For airplanes having line numbers 4923, 4924, and 4926 and subsequent: Before the accumulation of 9,000 total flight hours.
For Group 1 airplanes identified in Boeing Alert Service Bulletin 737-26A1137, dated May 22, 2014: Before or concurrently with accomplishing the initial operational test required of paragraph (g) of this AD, install new relays and do wiring changes to the environmental control system, in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-26-1122, Revision 1, dated August 13, 2009. When the actions required by this paragraph are done, the installation and changes specified in paragraph B. “Concurrent Requirements” of Boeing Special Attention Service Bulletin 737-26-1122, Revision 1, dated August 13, 2009, must also be done. However, operators should note that Boeing Alert Service Bulletin 737-28A1206, dated January 11, 2006, is not required by this AD.
Where paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin 737-26A1137, dated May 22, 2014, specifies a compliance time “after the original issue date of this service bulletin,” this AD requires compliance within the specified compliance time after the effective date of this AD.
