GPWS aural "SINK RATE" on B737
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GPWS aural "SINK RATE" on B737
Hello
My question is: The 737 QRH manuevers section lists "SINK RATE" as a GPWS caution. It is stated that the action from crew is to correct flight path, airplane configuration or airspeed.
In the note text below the list the text states: "If a terrain caution occurs when flying under daylight VMC , and positive visual verification is made that no obstacle or terrain hazard exists, the alert may be regarded as cautionary and the approach may be continued" Do you see the SINK RATE as a terrain caution? If yes, my issue is that the SINK RATE (and some of the other aural alerts) are accompagnied by the visual PULL UP in red. And for the GPWS warning you have to do the pull up maneuver, it is not stated whether it is for the visual PULL UP and the aural PULL UP or if just the visual indication is enough, in the latter case you can't continue an approach where SINK RATE has been given.
Any thoughts?
My question is: The 737 QRH manuevers section lists "SINK RATE" as a GPWS caution. It is stated that the action from crew is to correct flight path, airplane configuration or airspeed.
In the note text below the list the text states: "If a terrain caution occurs when flying under daylight VMC , and positive visual verification is made that no obstacle or terrain hazard exists, the alert may be regarded as cautionary and the approach may be continued" Do you see the SINK RATE as a terrain caution? If yes, my issue is that the SINK RATE (and some of the other aural alerts) are accompagnied by the visual PULL UP in red. And for the GPWS warning you have to do the pull up maneuver, it is not stated whether it is for the visual PULL UP and the aural PULL UP or if just the visual indication is enough, in the latter case you can't continue an approach where SINK RATE has been given.
Any thoughts?
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The only time you are required to carry out the terrain avoidance manoeuvre is when you hear an aural pull up, the pull up on the displays is not the trigger however it should be grabbing your attention.
EGPWS uses cautions and warnings via a combination of aural and visual displays; aural and visual should not be considered separate.
Cautions, 'amber level' alerts are intended to aid awareness and trigger corrective action as necessary; the words 'caution' and 'alert' are often interchanged.
Warnings, 'red level', require immediate action.
'Terrain' represents a particular threat and has related cautions and warnings, 'sink rate' is a terrain related caution and thus requires corrective action. If a 'sink rate' caution progresses to a 'pull up' warning, then pull up.
Any caution represents an unexpected situation, being somewhere or having done something not previously considered; thus always act.
A 'pull up' warning from any source or in combination with cautions is always actioned as a red level action.
IMHO any note which introduces an exception - day, VMC, etc, adds to the complexity of operations. Who and how are these judged, added workload, more time ... the same time as required to pull up.
I recall a CFIT accident in the Southern Med where the aircraft was VMC above cloud and the PM reported being visual with distant high ground (mistaken land mark); there was intermittent vertical contact with the sea. GPWS commanded a 'pull up', the crew hesitated and the aircraft hit the top of high ground still climbing.
This scenario was replicated in the simulator and evaluated by twelve senior line pilots from different airlines, they had some expectation of a warning. Six of them did not clear the hill; indecision, slow response, slow pitch rate, low pitch angle.
Fortunately EGPWS provides greater alerting times and a graphic display, but there are still situations requiring prompt action without distracting exceptions.
http://www.icao.int/safety/fsix/Libr...plus%20add.pdf
Add to the above, the crew who declared 'visual' with the field and descended early, they didn't see the radio mast - no obstacle mode fitted; but a transiting senior captain in the cabin did at eye level.
A few choice words during the debrief.
Cautions, 'amber level' alerts are intended to aid awareness and trigger corrective action as necessary; the words 'caution' and 'alert' are often interchanged.
Warnings, 'red level', require immediate action.
'Terrain' represents a particular threat and has related cautions and warnings, 'sink rate' is a terrain related caution and thus requires corrective action. If a 'sink rate' caution progresses to a 'pull up' warning, then pull up.
Any caution represents an unexpected situation, being somewhere or having done something not previously considered; thus always act.
A 'pull up' warning from any source or in combination with cautions is always actioned as a red level action.
IMHO any note which introduces an exception - day, VMC, etc, adds to the complexity of operations. Who and how are these judged, added workload, more time ... the same time as required to pull up.
I recall a CFIT accident in the Southern Med where the aircraft was VMC above cloud and the PM reported being visual with distant high ground (mistaken land mark); there was intermittent vertical contact with the sea. GPWS commanded a 'pull up', the crew hesitated and the aircraft hit the top of high ground still climbing.
This scenario was replicated in the simulator and evaluated by twelve senior line pilots from different airlines, they had some expectation of a warning. Six of them did not clear the hill; indecision, slow response, slow pitch rate, low pitch angle.
Fortunately EGPWS provides greater alerting times and a graphic display, but there are still situations requiring prompt action without distracting exceptions.
http://www.icao.int/safety/fsix/Libr...plus%20add.pdf
Add to the above, the crew who declared 'visual' with the field and descended early, they didn't see the radio mast - no obstacle mode fitted; but a transiting senior captain in the cabin did at eye level.
A few choice words during the debrief.
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If descending into an area that you are unfamiliar with in IMC or night, keep an eye on the radio altimeter. In most cases just before a GPWS "Pull Up" warning sounds, the radio altimeter will come "alive" and show rapidly decreasing RA height. If you take immediate emergency climb action right away without waiting for the aural "Terrain Pull Up" warning, you may save a couple of hundred feet and that may save your skin. We practice this in the simulator and it works.
