AIRWORTHINESS DIRECTIVE
On the effective date specified below, and for the reasons set out in the background section, the CASA delegate whose signature appears below repeals Airworthiness Directive (AD) AD/B737/294 Amdt 1 and issues the following AD under subregulation 39.001(1) of CASR 1998 and subsection 33(3) of the Acts Interpretation Act 1901. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.
Boeing 737 Series Aeroplanes
AD/B737/294 Amdt 2
Flightcrew Oxygen Masks
19/2013
 
Applicability:
Boeing Model 737-100, -200, -200C, -300, -400, -500, -600, -700, -700C, -800 and
-900 series aeroplanes.

Requirement:
1.    Revise the Cabin Pressurization procedures in the Normal Procedures section of the AFMs for Model 737-100, -200, -200C, -300, -400, -500, -600, -700, -700C,
-800, and -900 series aeroplanes to include the following procedure:
"For normal operations, the pressurization mode selector should be in AUTO prior to takeoff."
2.    Revise the Emergency Procedures section of the AFMs for Model 737-100, -200, -200C, -300, -400, and -500 series aeroplanes, or the Non-Normal Procedures section of the AFMs for Model 737-600, -700, -700C, -800, and -900 series aeroplanes, as applicable, to include the following procedure:
"WARNING HORN - CABIN ALTITUDE OR CONFIGURATION
RECALL
Condition: An intermittent or steady warning horn sounds:
•  In flight an intermittent horn indicates the cabin altitude is at or above 10,000 feet
•  On the ground an intermittent horn indicates an improper takeoff configuration when advancing thrust levers to takeoff thrust
•  In flight a steady horn indicates an improper landing configuration.
If an intermittent horn sounds in flight:
OXYGEN MASKS AND REGULATORS..............on, 100%
CREW COMMUNICATIONS.................................Establish

 
 
 
Do the CABIN ALTITUDE WARNING OR RAPID DEPRESSURIZATION checklist.
If an intermittent horn sounds on the ground:
Assure proper aeroplane takeoff configuration.
If a steady horn sounds in flight:
Assure proper airplane landing configuration.”
Method To Revising the AFM
The AFM revisions specified in requirements 1 and 2 of this AD may be done by inserting a copy of this AD into the AFM.
When statements identical to those specified in requirements 1 and 2 of this AD have been included in general revisions of the AFM, then the general revision(s) may be inserted into the AFM, and the copy of the AD may be removed from the applicable revised sections of the AFM.
Optional Action for Certain Requirements of AD/B737/208, AD/B737/216 and AD/B737/255.
If any of the following optional actions are taken, make a notation to the effect in the compliance summary for the appropriate AD.
For Model 737-100, -200 and -200C series aeroplanes: Using the phrase, “If the intermittent cabin altitude/configuration warning horn sounds in flight:” in place of the phrase, “If the cabin altitude warning horn sounds:” in the revisions to the “Cabin Altitude Warning or Rapid Depressurization” procedure is acceptable for compliance with AD/B737/255.
For Model 737-300, -400 and -500 series aeroplanes: Using the phrase, “If the intermittent cabin altitude/configuration warning horn sounds in flight:” in place of the phrase, “If the cabin altitude warning horn sounds:” in the revisions to the “Cabin Altitude Warning or Rapid Depressurization” procedure is acceptable for compliance with AD/B737/208.
For Model 737-600, -700, -700C, -800 and -900 series aeroplanes: Using the phrase, “If the intermittent cabin altitude/configuration warning horn sounds in flight:” in place of the phrase, “Condition: The cabin altitude warning horn sounds.” in the revisions to the “Cabin Altitude Warning or Rapid Depressurization” procedure is acceptable for compliance with AD/B737/216.
Note:  FAA AD 2006-13-13 Amdt 38-14666 dated 15 June 2006 refers.
 
 
Compliance:
Within 60 days after the effective date of this AD.
Revising the AFM as per the approved FAA AMOC Letter 130S-09-134a dated
28 April 2009 is an alternate means of complying with requirement 2 of this AD.

 
The effective date of this Amendment is 27 September 2013.

Background:
This AD results from reports that aeroplanes have failed to pressurize, and that the flight crews failed to react properly to the cabin altitude warning horn.  The issuing of this AD to prevent failure of the aeroplane to pressurize and subsequent failure of the flight crew to recognize and react to a valid cabin altitude warning horn, which could result in incapacitation of the flight crew due to hypoxia (lack of oxygen in body) and consequent loss of aeroplane control.
Amendment 1 removed the word “RECALL” from the AFM amendment detailed in Requirement 2 and placed that word on the second line of the AFM.
Amendment 2 allows the revising of the AFM as per the approved FAA AMOC Letter 130S-09-134a dated 28 April 2009 as an alternate means of complying with requirement 2 of this AD.
Amendment 1 of this AD became effective on 26 October 2006.
The original issue of this AD became effective on 28 September 2006.

Peter Nikolic
Delegate of the Civil Aviation Safety Authority
4 September 2013