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Published: 29 July 2011
Effective: 29 July 2011

ATA Chapter: 31

Subject:

Concern that older EGPWS software versions may result in unannunciated loss of EGPWS function.

Applicability:

Honeywell MK XXII Enhanced Ground Proximity Warning Systems (EGPWS) installed on helicopters

Applicability:           

All operators and maintainers of Honeywell MK XXII Enhanced Ground Proximity Warning Systems (EGPWS) installed on helicopters.

Purpose:      

This Continuing Airworthiness Notice (CAN) is issued to inform operators and maintainers of helicopters fitted with Honeywell MK XXII EGPWS that there is a concern that older EGPWS software versions may result in unannunciated loss of EGPWS function. The loss of EGPWS function will reduce the desired or expected protection from inadvertent controlled flight into obstacles or terrain.

Background:          

The Honeywell MK XXII EGPWS system is designed for use on helicopters fitted with a radio altimeter. The EGPWS uses the radio altimeter signal to indicate transition from on-ground to in-flight which enables the “look-ahead” predictive warnings and cautions of the EGPWS. With certain older EGPWS software versions the predictive warnings and cautions of the “look ahead” features are not activated and there is no annunciation of the degraded operational condition of the EGPWS to the flight crew. Honeywell have issued updated software which corrects this problem.

Recommendation:

The CAA recommends that operators and maintainers of Honeywell MK XXII EGPWS installed on helicopters contact Honeywell and the STC holder to arrange the installation of the appropriate software per the instructions in Honeywell Service Bulletins ATA Numbers 965-1590/1595-34-36 and 965-1595-34-22 as applicable (Honeywell publication numbers D201009000034 and D201006000021). Failure to install the updated software could result in less than desired or expected protection from inadvertent controlled flight into terrain or obstacles.

For further information about the subject of this CAN refer to FAA Special Airworthiness Information Bulletin (SAIB) No. SW-11-31R1 dated 18 July 2011. A copy of the FAA SAIB can be obtained from http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgSAIB.nsf/MainFrame?OpenFrameSet(external link)