AD 2020-05-26 Airworthiness Directives; The Boeing Company Airplanes

Models named: 787-8. Read the applicability below — it usually turns on serial or part numbers too.

This AD applies to The Boeing Company Model 787-8 airplanes, certificated in any category, line numbers 6, 11, 17, 19, 20, 21, 23, 25 through 30 inclusive, and 32 through 38 inclusive.

Comply with this AD within the compliance times specified, unless already done.

Within 12 months after the effective date of this AD: Do a one-time leak (functional) test of the strut upper spar areas for the left and right wing struts, by doing the actions specified in paragraphs (g)(1) through (5) of this AD. A review of airplane maintenance records is acceptable in lieu of this test if it can be conclusively determined from that review that the leak test was previously accomplished and successfully completed. (1) Put a plug in the strut forward drain outlet (this drain outlet is labeled as “pylon strut”). Put an empty container below the strut forward drain outlet to collect water drained through this outlet. (2) Apply 381 to 387 fluid ounces (11.3 to 11.4 liters) of water in 2.5 to 3.5 minutes, to the systems tubing shroud (area between the forward and mid-vapor barriers). (3) Make sure that no leakage occurred after doing the action specified in paragraph (g)(2) of this AD. (4) Remove the plug from the strut forward drain outlet and make sure that the water is drained through the strut forward drain outlet only. (5) After 3 minutes from accomplishing the action specified in paragraph (g)(4) of this AD, measure the water collected in the container, and do the applicable actions specified in paragraphs (g)(5)(i) through (iii) of this AD. (i) If leaks were found, do corrective action before further flight using a method approved in accordance with the procedures specified in paragraph (h) of this AD. (ii) If no leaks were found and less than 354 fluid ounces (10.5 liters) of water is collected in the container, do corrective action before further flight using a method approved in accordance with the procedures specified in paragraph (h) of this AD. (iii) Before further flight after accomplishing any corrective action required by paragraph (g)(5)(i) or (ii) of this AD, repeat the actions specified in paragraphs (g)(1) through (5) of this AD until successful completion of the test ( i.e., no leaks are found and 354 fluid ounces (10.5 liters) of water or more is measured in the container). Note 1 to paragraph (g): Additional guidance for performing the leak (functional) test can be found in Boeing 787 Aircraft Maintenance Manual (AMM), 54-65-01, Strut Spar—Upper—Functional Test.

This AD was prompted by a report of failure of a wing strut leak test due to a missing bolt on the firewall. The FAA is issuing this AD to address a hole in the firewall, which could allow flammable fluid to leak from the strut compartment to the engine compartment when the drainage provision is overwhelmed. Flammable fluid leakage into the engine compartment could result in an uncontrollable engine fire and consequent structural failure of the wing.

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