Part 121 operator instructing flight crew to ignore Ground Proximity Warning System warnings

Thank you for your letter of 8 January 2026 regarding REPCON RA2026-00003 in relation to ‘Part 121 operator instructing Flight Crew to ignore Ground Proximity Warning System warnings for low gradient (non-normal) departures in [Location]’. [Operator] takes all safety related matters seriously and has carefully considered the items set out in the provided REPCON. Our response to the matters raised in the REPCON is set out below.

Flight Operations Newsletter Article and [Manual Supplement] Guidance

The reporter references [aircraft type newsletter] on [date], which the relevant section is reproduced in its entirety (de-identified) below:

Enhanced Ground Proximity Warning System (EGPWS) alerting - [Location]

Evidence based training [x] Cyclics feature a ‘low gradient climb’ that is, engine failure on departure from [Location]. This exercise was switched to runway [x1] as EGPWS warnings were occurring when runway [x2] was used. Consideration around this situation reaffirmed EGPWS behaviour in low gradient climb situations - the system is programmed for normal operations - that is, two engines. In an engine out situation, the EGPWS system does not recognise the loss of an engine and will continue to alert based on two engine terrain separation margins. It is acceptable to disregard the EGPWS warning in this situation as the CDP ensures terrain separation – this should be pre-briefed as a contingency. A note has been added to the [Manual Supplement] entry for [Location]:

‘ALL RWY [xx]: In the event of a low gradient climb (for example engine failure), an EGPWS caution or warning level message may be generated when flying the runway CDP in close proximity to terrain. Flight Crew should verify position, and continue to track via the engine out procedure to ensure terrain/obstacle clearance, as actual aircraft performance has been analysed and determined satisfactory.’

These alerts may occur until the CDP is redesigned with a view to preventing these ‘nuisance’ alerts.

As detailed in the newsletter article, this information was placed in the [Operator] [Manual Supplement] (within [electronic flight bag]), which is the formal channel to advise Flight Crew of Threats and Considerations at each airport, and the current relevant extract is as follows:

'ALL RWY [xx]: In the event of a low gradient climb (for example engine failure), an EGPWS caution or warning level message may be generated when flying the runway CDP in close proximity to terrain. Flight Crew should verify position and continue to track via the engine out procedure to ensure terrain/obstacle clearance.'

EGPWS and low performance climb requirements

The EGPWS issue for [Location] departures was highlighted to Flight Crew in a recent simulator recurrent session which involved an engine failure on departure. The EGPWS utilises various aircraft inputs and an internal database to warn Flight Crew of potential conflicts with obstacles or terrain. In this specific case of a departure from RWY [x2] in [Location], as the aircraft turns on the CDP the obstacle field of view is expanded into the turn and may trigger an EGPWS alert during low performance climb scenarios (such as a significant loss of thrust, or an engine failure). This is due to an inherent limitation in EGPWS design, where the same normal all-engine performance terrain buffers are applied to the low performance climb scenario. The EGPWS is unable to detect a reduced performance climb and adjust to reduced terrain margins for the non-normal case.

The obstacle clearance requirements are detailed in Part 121 (Australian Air Transport Operations – Larger Aeroplanes) Manual of Standards (MOS) 2020, Chapter 9 – Performance. These specify that the net take-off flight path following an engine failure at V1 (maximum speed at which a rejected takeoff can be initiated in the event of an emergency) must clear obstacles by 35 ft (or 50 ft when there is a change in aeroplane heading). [Operator 1] [department] conduct analysis of these requirements for the most critical configuration and conditions to ensure that the calculated maximum aircraft take-off weight meets these requirements. A CDP chart is produced defining a containment area and procedure (that is, acceleration and thrust reduction heights) to ensure these requirements are met.

Spurious EGPWS alerts during low performance climb scenarios are applicable to all operators departing from [Location], including the local operator [Operator 2] who [Operator] consulted with extensively prior to providing any guidance to Flight Crew. The [Operator] [manual supplement] text mirrored the guidance provided to [Operator 2] Flight Crew.

The guidance to [Operator] Flight Crew is specific to the [Location] departure case from the runway [xx] departure direction, specifying that EGPWS alerts may be generated in reduced performance climb non-normal situations, as these are based on larger terrain buffers than required under Chapter 9 of Part 121 MOS. This must be pre-briefed prior to departure such that all Flight Crew have a shared understanding of the management of this situation. Further, prior to disregarding any alert, Flight Crew must verify their position confirming that it is within the defined requirements of the CDP. [Operator] only permit an alert to be disregarded in this specific scenario with these specific considerations. This is not permissible for departure at another airport or situation. [Operator] train Flight Crew to react to all aircraft warnings as per the applicable aircraft manuals and procedures in all other cases. Given the rarity of an engine failure in modern jet aircraft, and that EGPWS warnings are not guaranteed to occur in all low performance climb events, [Operator] deem it highly unlikely that a normalisation of deviance would occur as it would be highly unlikely Flight Crew would face such a scenario. For normalisation of deviance to occur, Flight Crew would need to be exposed to regular and repeated non-standard operations which is not the case in this situation.

Future Considerations

[Operator] [department] is considering modification of the CDP to delay the initial turn in the CDP, to prevent the possible EGPWS alert for the specific [Location] [runway x2] departure case. This is a current project which would mean this topic and discussion would be an interim consideration for Flight Crews.

Further, [Operator] is considering addition of the [x2] runway identifier to the [manual supplement] guidance (rather than generically stating all [xx] departures as per the current text), as further investigation has deemed this the only critical departure runway. This would further limit disregarding EGPWS alerts only to this specific runway departure in [Location], reducing crew exposure.

Conclusion

[Operator] does not agree with the reporter’s comments suggesting that terrain impact is imminent following an EGPWS alert in the [Location] runway [xx] departure case. The guidance to Flight Crew has been carefully considered including advice from the local operator, and [Operator] [department]. Further, [Operator] does not consider there to be a possibility of a normalised deviation given there is no other guidance for disregarding EGPWS alerts other than in this one specific (and highly unlikely) case, with the requirement pre-briefed and the aircraft position verified prior to disregarding any alert. [Operator], however, remains committed to working with the relevant stakeholders including Flight Crew, in management of this issue. We thank the ATSB for forwarding the reporter’s concerns and are willing to provide any further information should this be required.