Airworthiness Directive · Amendment 39-21204 · Pneumatic
The Boeing Company Airplanes
This AD applies to all The Boeing Company Model 737-300, -400, -500, -600, -700, -700C, -800, -900, and -900ER series airplanes, certificated in any category.
The FAA is adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-300, -400, -500, -600, -700, -700C, -800, -900, and -900ER series airplanes. An emergency AD was sent to all known U.S. owners and operators of these airplanes. This AD requires inspections of the engine bleed air 5th stage check valve on each engine, and replacement of the engine bleed air 5th stage check valve if any inspection is not passed. This AD was prompted by four recent reports of single-engine shutdowns due to engine bleed air 5th stage check valves being stuck open. The FAA is issuing this AD to address the unsafe condition on these products.
Any airplane that, for 7 or more consecutive days, has not been operated in flight is considered to be in “storage.”
(1) For any airplane that is in storage on or after the effective date of this AD, and any airplane that, as of the effective date of this AD, has been operated for 10 or fewer flight cycles since returning to service from the most recent period of storage: Before further flight, do the inspections specified in paragraphs (h)(1)(i) and (ii) of this AD on the engine bleed air 5th stage check valve on each engine. If any engine bleed air 5th stage check valve fails any inspection, replace that engine bleed air 5th stage check valve before further flight. For each engine bleed air 5th stage check valve that passes both inspections specified in paragraphs (h)(1)(i) and (ii) of this AD, do the actions specified in paragraph (h)(2) of this AD on that engine bleed air 5th stage check valve before further flight.
(i) Rotate the flapper plates by hand at least 3 times. If the flapper plate moves smoothly, without signs of binding or sticking, from the fully closed position to the stop tube using gravity force alone, the engine bleed air 5th stage check valve has passed this inspection.
(ii) Measure the clearance between the flapper bushings at both locations on each engine bleed air 5th stage check valve. If the clearance between the flapper bushings is a minimum of 0.004 inch (0.102 mm) at both locations, the engine bleed air 5th stage check valve at that location has passed this inspection.
(2) For each engine bleed air 5th stage check valve that passes the inspections specified in paragraphs (h)(1)(i) and (ii) of this AD, do the inspections specified in paragraphs (h)(2)(i) through (iii) of this AD before further flight on the engine bleed air 5th stage check valve on each engine. If any engine bleed air 5th stage check valve fails any of the inspections specified in paragraphs (h)(2)(i) through (iii) of this AD, replace that engine bleed air 5th stage check valve before further flight.
(i) Do a general visual inspection of the flapper bushings for signs of cracks, fractures, and missing bushing heads. If the flapper bushings do not show any signs of cracks, fractures, or missing bushing heads, the engine bleed air 5th stage check valve has passed this inspection. Signs of corrosion are not a cause for replacing the engine bleed air 5th stage check valve if the engine bleed air 5th stage check valve did not fail any of the inspections specified in paragraph (h)(1) of this AD.
(ii) Using only hand pressure, try to rotate the flapper bushings in the flapper plates. If the bushings do not rotate in the flapper plate, the engine bleed air 5th stage check valve has passed this inspection.
(iii) Do a general visual inspection of the check valve for signs of the flappers rubbing against the valve body. If the flappers do not show any signs of rubbing against the valve body, the engine bleed air 5th stage check valve has passed this inspection.
For airplanes that have operated 10 or fewer flight cycles since the most recent period of storage prior to the effective date of this AD, as an alternative to compliance with paragraph (h): If allowed by the operator's FAA-approved Minimum Equipment List, the airplane may be dispatched with one engine's engine bleed air high stage valve locked closed. Thereafter, within 5 additional flight cycles, inspect the engine bleed air 5th stage check valve on both engines as required by paragraph (h) of this AD.
