AD/Premier/5 Cabin Altitude and Barometric Pressure Switches (Cth)

AIRWORTHINESS DIRECTIVE

For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.001(1) of CASR 1998.  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.

Hawker Beechcraft (Raytheon) 390 Series Aeroplanes

AD/PREMIER/5 Cabin Altitude and Barometric
Pressure Switches 12/2008 DM

Applicability:	Model 390 aeroplanes, serial numbers RB-1 and RB-4 through RB-238 inclusive.
Requirement:	1.    If not previously accomplished, modify the cabin barometric pressure switch and cabin altitude high switch installations in accordance with Hawker Beechcraft Mandatory Service Bulletin SB 21-3899, original issue, dated May 2008.
2     Perform a functional test of the switches and related systems in accordance with Part I - Ground Test Method in Paragraph 3 of the Accomplishment Instructions of SB 21-3899, original issue.
Note 1:  If, before the effective date of this Directive, the flight test method in Part II of the Accomplishment Instructions of SB 21-3899, original issue, was carried out, then the Requirement 2 functional test is not required provided it was done after the Requirement 1 modification was accomplished.
3.    The flight test method described in Part II of the Accomplishment Instructions of SB 21-3899, original issue, is prohibited.
Later revisions of the above SB, approved by the United States Federal Aviation Administration (FAA) as an Alternate Method of Compliance (AMOC) to FAA AD 2008-21-04, are considered acceptable for compliance with the equivalent Requirements of this Directive.
Note 2:  FAA AD 2008-21-04 Amdt 39-15688 refers.
Compliance:	For Requirement 1 - Within 25 hours time-in-service (TIS) after 20 October 2008 (the effective date of this Directive) or within 30 days after 20 October 2008, whichever occurs first.
For Requirement 2 - Before further flight after the Requirement 1 modification of the cabin barometric pressure switch and cabin altitude high switch installations is accomplished.
For Requirement 3 - After the effective date of this Directive.
This Airworthiness Directive becomes effective on 20 October 2008.

Background:

The FAA has received reports of occurrences of incorrectly connected barometric switches.  Additionally, the terminal used on the switches may be inadvertently dislodged while performing aeroplane maintenance in the pedestal area.

This Directive requires the modification of the cabin barometric pressure switch and cabin altitude high switch to prevent them from becoming incorrectly connected or inadvertently disconnected, which may result in no CABIN ALT HI annunciation in the cockpit and no automatic deployment of the cabin oxygen masks.  This failure could lead to incapacitation of the crew due to hypoxia with possible inability to control the aeroplane.

Charles Lenarcic
Delegate of the Civil Aviation Safety Authority

10 October 2008