preamble attached >>>
ADs updated daily at www.Tdata.com
2020-16-51 THE BOEING COMPANY: (EMERGENCY) Project Identifier AD-2020-01032-T.
(a) EFFECTIVE DATE

    This emergency AD is effective upon receipt.

(b) AFFECTED ADS

    None.

(c) APPLICABILITY

    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.

(d) SUBJECT

    Air Transport Association (ATA) of America Code 36, Pneumatic.

(e) UNSAFE CONDITION

    This AD was prompted by four recent reports of single-engine shutdowns
    caused by engine bleed  air 5th stage check  valves stuck in the  open
    position.  The FAA  is issuing  this AD  to address  corrosion of  the
    engine bleed air 5th stage check valves for both engines, which  could
    result in  compressor stalls  and dual-engine  power loss  without the
    ability  to  restart,  which  could  result  in  a  forced off-airport
    landing.

(f) COMPLIANCE

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

(g) DEFINITION

    Any  airplane that,  for 7  or more  consecutive  days,  has not  been
    operated in flight is considered to be in “storage.”

(h) INSPECTIONS AND CORRECTIVE ACTIONS

(1) For any airplane that is in storage on or after the date of receipt of
    this AD, and any airplane that, as of the date of receipt 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.

(i) MINIMUM EQUIPMENT LIST RELIEF FOR CERTAIN AIRPLANES

    For airplanes that have operated  10 or fewer flight cycles  since the
    most recent  period of  storage prior  to receipt  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.

(j) SPECIAL FLIGHT PERMIT

    Special flight permits may be issued in accordance with 14 CFR  21.197
    and 21.199 to  operate the airplane  to a location  where the airplane
    can be inspected,  provided one engine’s  engine bleed air  high stage
    valve has  been locked  closed. This  option is  only available if the
    operator’s FAA-approved Minimum Equipment List allows dispatching  the
    airplane with one  engine’s engine bleed  air high stage  valve locked
    closed.

(k) ALTERNATIVE METHODS OF COMPLIANCE (AMOCS)

(1) For  Boeing  Model  737-300, -400,  and  -500   series  airplanes, the
    Manager, Los  Angeles ACO  Branch, FAA,  has the  authority to approve
    AMOCs for this AD, if requested  using the procedures found in 14  CFR
    39.19. In  accordance with  14 CFR  39.19, send  your request  to your
    principal  inspector or  local Flight  Standards  District  Office, as
    appropriate. If  sending information  directly to  the manager  of the
    certification  office,  send  it  to  the  attention  of  the   person
    identified in paragraph (l)(1) of this AD. Information may be  emailed
    to: 9-ANM-LAACO-AMOCRequests@faa.gov.

(2) For Boeing Model 737-600,  -700, -700C, -800, -900, and  -900ER series
    airplanes, the Manager, Seattle ACO Branch, FAA, has the authority  to
    approve AMOCs for this AD, if requested using the procedures found  in
    14 CFR 39.19. In  accordance with 14 CFR  39.19, send your request  to
    your principal inspector or local Flight Standards District Office, as
    appropriate. If  sending information  directly to  the manager  of the
    certification  office,  send  it  to  the  attention  of  the   person
    identified in paragraph (l)(2) of this AD. Information may be  emailed
    to: 9-ANM-Seattle-ACOAMOC-Requests@faa.gov.

(3) Before  using  any  approved AMOC, notify  your appropriate  principal
    inspector, or lacking a principal inspector, the manager of the  local
    flight standards district office/certificate holding  district office.

(4) An AMOC that  provides an acceptable level  of safety may be  used for
    any repair, modification, or alteration  required by this AD if  it is
    approved by The Boeing Company Organization Designation  Authorization
    (ODA) that  has been  authorized by  the Manager,  Seattle ACO Branch,
    FAA,  to  make those  findings.  To be  approved,  the repair  method,
    modification  deviation,  or   alteration  deviation  must   meet  the
    certification  basis   of  the   airplane,  and   the  approval   must
    specifically refer to this AD.

(l) RELATED INFORMATION

(1) For Boeing Model 737-300, -400, and -500 series airplanes, for further
    information  about  this   AD,  contact  Serj   Harutunian,  Aerospace
    Engineer,  Propulsion  Section,  FAA,  Los  Angeles  ACO  Branch, 3960
    Paramount  Boulevard,  Lakewood, CA  90712-4137;  phone: 562-627-5254;
    fax: 562-627-5210; email: serj.harutunian@faa.gov.

(2) For Boeing Model 737-600,  -700, -700C, -800, -900, and  -900ER series
    airplanes, for  further information  about this  AD, contact Rajendran
    Mohanraj,  Aerospace Engineer,  Propulsion Section,  FAA, Seattle  ACO
    Branch, 2200  South 216th  St., Des  Moines, WA  98198; phone and fax:
    206-231-3621; email: rajendran.mohanraj@faa.gov.

Issued on July 23, 2020.  Lance T. Gant, Director, Compliance & Airworthi-
ness Division, Aircraft Certification Service.
PREAMBLE 

FAA Aviation Safety

EMERGENCY AIRWORTHINESS DIRECTIVE
www.faa.gov/aircraft/safety/alerts/

DATE: July 23, 2020

AD #: 2020-16-51

Emergency Airworthiness Directive (AD) 2020-16-51 is sent to owners and operators of The Boeing Company Model 737-300, -400, -500, -600, -700, -700C, -800, -900, and -900ER series airplanes.

Background

This emergency AD was prompted by four recent reports of single-engine shutdowns due to engine bleed air 5th stage check valves being stuck open. Corrosion of the engine bleed air 5th stage check valve internal parts during airplane storage may cause the valve to stick in the open position. If this valve opens normally at takeoff power, it may become stuck in the open position during flight and fail to close when power is reduced at top of descent, resulting in an unrecoverable compressor stall and the inability to restart the engine. Corrosion of these valves on both engines could result in a dual-engine power loss without the ability to restart. This condition, if not addressed, could result in compressor stalls and dual-engine power loss without the ability to restart, which could result in a forced off-airport landing.

FAA’s Determination

The FAA is issuing this AD because the agency evaluated all the relevant information and determined the unsafe condition described previously is likely to exist or develop in other products of the same type design.

AD Requirements

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.

Authority for this Rulemaking

Title 49 of the United States Code specifies the FAA’s authority to issue rules on aviation safety. Subtitle I, Section 106, describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the Agency’s authority.

The FAA is issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701, General requirements. Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

Presentation of the Actual AD

The FAA is issuing this AD under 49 U.S.C. Section 44701 according to the authority delegated to me by the Administrator.