Airworthiness directives › 2022-24-09
AD 2022-24-09 Airworthiness Directives; The Boeing Company Airplanes
Models named: 737-100, -200, -200C, -300, -400, -500, -600, -700, -700C, -800. Read the applicability below — it usually turns on serial or part numbers too.
Applicability*9
This AD applies to all The Boeing Company Model 737-100, -200, -200C, -300, -400, -500, -600, -700, -700C, -800, -900, and -900ER series airplanes, and Model 737-8, 737-9, and 737-8200 airplanes, certificated in any category.
Compliance
Comply with this AD within the compliance times specified, unless already done.
Required actions
(1) At the latest of the times specified in paragraphs (g)(1)(i) through (iii) of this AD, perform a functional test of the cabin altitude pressure switches having part number 214C50-2, using an adapter as specified in figure 1 to paragraph (g) of this AD, or an equivalent adapter, and matching hose to connect to the cabin altitude warning switch. Repeat the functional test thereafter at intervals not to exceed 2,000 flight hours. If, during any functional test, any cabin altitude pressure switch fails to activate at an altitude of between 9,000 and 11,000 feet, replace the switch before further flight. (i) Within 2,000 flight hours since the last functional test of the cabin altitude pressure switches. (ii) Prior to the accumulation of 2,000 total flight hours on the airplane. (iii) Within 90 days after the effective date of this AD. (2) Adapters are considered to be equivalent as long as the mating side with the switch meets the specifications in either paragraph (g)(2)(i) or (ii) of this AD: (i) Greater than or equal to 0.265 inch (0.673 cm) X 7/16-20-UNJF-3A and less than or equal to 0.438 inch (1.113 cm) X 7/16-20-UNJF-3A for the flareless end; or (ii) Less than or equal to 0.5 inch (1.27 cm) total with greater than or equal to 0.265 inch (0.673 cm) X 7/16-20-UNJF-3A thread for AN4 flared end. BILLING CODE 4610-13-P ER22DE22.004 ER22DE22.005 Note 1 to paragraph (g): Additional guidance for performing the functional test required by paragraph (g) of this AD can be found in Boeing 737-200 Aircraft Maintenance Manual (AMM) 21-33-11/501, Boeing 737-300/400/500/600/700/800/900/7/8/8200/9 AMM 21-33-00/501, 737CL AMM TASK CARD 31-026-01-01, 737CL AMM TASK CARD 31-010-01-01, 737NG AMM TASK CARD 31-020-00-01, and 737MAX AMM TASK CARD 31-020-00-01, and other approved maintenance procedures.
Unsafe condition
This AD was prompted by reports of latent failures of the cabin altitude pressure switches, and the determination that using certain adapters while performing a functional test may lead to false failures of the cabin altitude pressure switches. The FAA is issuing this AD to address the unexpectedly high rate of latent failure of both pressure switches on the same airplane, which could result in the cabin altitude warning system not activating if the cabin altitude exceeds 10,000 feet, resulting in hypoxia of the flightcrew, and loss of control of the airplane.
Affected ADs
This AD replaces AD 2021-14-20, Amendment 39-21647 (86 FR 38214, July 20, 2021) (AD 2021-14-20).
Read the original on the Federal Register →
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The directive text above is reproduced from the Federal Register, a work of the United States government and in the public domain. The separation into applicability, compliance and required actions is TrackAD's.*1