AD/ERJ-170/12 Inertial Reference Unit Improvement (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.

Embraer ERJ-170 Series Aeroplanes

AD/ERJ-170/12 Inertial Reference Unit Improvement 11/2007

Applicability:	All ERJ-170(  ) aircraft models.
Requirement:	If not previously accomplished, remove the wiring connections from pins 51 and 52 in the electrical connectors of both Inertial Reference Units (IRU) in accordance with the procedures in Embraer Service Bulletin 170-34-0019 original issue dated 26 February 2007, or later revision approved by the Brazilian Agência Nacional de Aviação Civil (ANAC).
Note:  ANAC AD 2007-08-03 refers.
Compliance:	Within the next 18 months after the effective date of this Directive.
This Airworthiness Directive becomes effective on 25 October 2007.
Background:	The ANAC has advised of reports of IRU failures which lead to an erroneous flight path angle (FPA) indication on both primary flight displays, with no alert to this condition to the crew.  On ERJ-170 aircraft, FPA is considered as important as pitch and bank angle for piloting purposes.
Since this condition affects flight safety, this Directive requires wiring changes which will improve IRU functionality.

Charles Lenarcic
Delegate of the Civil Aviation Safety Authority

7 September 2007