Learn what the GPWS “DON'T SINK” warning means after take-off or go-around, how pilots respond, and how it differs from SINK RATE and PULL UP.
In real-world aviation, the “DON’T SINK” warning means the ground-proximity warning system has detected excessive altitude loss shortly after take-off or during a go-around. Pilots should immediately arrest the descent, apply the required thrust, establish a safe climb and follow the aircraft operator’s published GPWS response procedure.
When does GPWS say “DON’T SINK”?
GPWS or EGPWS normally calls “DON’T SINK” when an aircraft loses too much altitude during a flight phase in which it should be climbing away from the ground. On many transport-aircraft systems, this function is known as Mode 3: excessive altitude loss after take-off or go-around.
The system typically evaluates pressure-altitude loss together with height and flight-phase logic. Exact alert envelopes differ between aircraft, GPWS versions and operator configurations, so there is no universal trigger height or permitted loss.
It is not a general instruction never to descend. It is a phase-specific alert saying that the aircraft’s flight path is inconsistent with a safe climb. It can sound over flat terrain because it detects altitude loss, not only terrain directly ahead.
How should pilots respond to a “DON’T SINK” warning?
The immediate task is to correct the flight path; diagnosing the cause comes after the aircraft is climbing safely. The aircraft’s checklist, operating manual and company procedure always take priority over generic guidance.
- Arrest the altitude loss. Apply a decisive but controlled pitch correction and use reliable attitude, airspeed and vertical-speed references. Do not pull so aggressively that the aircraft approaches a stall.
- Set the required thrust. Confirm that the commanded power has actually been produced. During a go-around this commonly means selecting the prescribed go-around thrust and verifying that TOGA and the associated guidance modes are working as intended.
- Control the configuration. Check that speedbrakes or spoilers are retracted and that gear and flap changes follow the aircraft’s normal schedule. Premature flap retraction or an improvised configuration change can deepen the sink.
- Confirm a positive climb. Cross-check the altimeter, vertical-speed indication, radio altimeter, airspeed and flight-mode annunciator where fitted. If the autopilot or flight director is commanding an unsafe path, follow the aircraft-specific procedure rather than blindly chasing its guidance.
- Escalate when required. If terrain clearance remains doubtful, or the alert develops into “PULL UP” or another urgent terrain warning, execute the prescribed terrain-avoidance manoeuvre immediately. Our explanation of how PULL UP changes the required response covers that more urgent case.
A normal go-around and a terrain-escape manoeuvre are not interchangeable. The latter may require maximum available performance and takes priority over an ATC instruction, but its exact pitch, automation and configuration actions are aircraft-specific.
How is “DON’T SINK” different from “SINK RATE” and “PULL UP”?
“DON’T SINK” concerns altitude loss after take-off or go-around, while “SINK RATE” concerns an excessive rate of descent near the ground and “PULL UP” demands a more urgent terrain response.
| Alert | What it indicates | Basic response |
|---|---|---|
| DON’T SINK | Excessive altitude loss after take-off or during a go-around | Correct the flight path and regain a safe climb |
| SINK RATE | Excessive descent rate close to the ground, often on approach | Reduce the descent rate or go around if the approach is unstable |
| PULL UP | An urgent GPWS or EGPWS terrain threat | Perform the aircraft’s immediate terrain-escape manoeuvre |
Alerts can follow one another as the situation worsens. Crews therefore respond to the most urgent active warning and the priorities defined in their aircraft procedures.
What commonly causes a “DON’T SINK” warning?
Most alerts follow a genuine loss of climb performance or an unintended descent during the departure or missed-approach phase.
- Insufficient thrust: go-around power was not selected, the autothrottle entered an unexpected mode, or an engine did not produce the commanded thrust.
- Low airspeed or poor pitch control: the aircraft settles after rotation or loses energy while being pitched too steeply.
- Windshear or a downdraught: the surrounding air mass causes rapid altitude loss despite apparently correct control inputs. Any dedicated windshear warning must be handled under the approved windshear procedure.
- Configuration drag: extended speedbrakes, inappropriate flap or gear handling, or an out-of-trim condition prevents the expected climb.
- Go-around mode confusion: the crew initiates a go-around but the flight director, autopilot or thrust system remains in an approach or altitude-capture mode.
- Excessive bank: a steep turn close to the ground reduces the vertical component of lift and can produce a sink.
Can “DON’T SINK” be a false warning?
A nuisance or erroneous alert is possible, but pilots treat the warning as valid until the flight path is safe and the cause is understood. Visual contact with the ground alone is not a reason to ignore unexplained altitude loss.
The classic “DON’T SINK” function is driven chiefly by sensed altitude loss and take-off or go-around phase logic, rather than simply by a terrain database. Faulty air-data inputs, incorrect phase detection or a system fault can therefore produce an inappropriate alert. An intentional low-level manoeuvre may also enter the alert envelope even though the system is operating correctly.
Why does “DON’T SINK” sound in a flight simulator?
In a flight simulator, the warning usually means the simulated GPWS believes the aircraft is in a climb-away phase while its vertical path has become negative. Add-on implementations vary, and some use much simpler logic than certified real-world equipment.
- Check the flight-mode annunciator: confirm that the go-around mode actually engaged rather than assuming a button press selected it.
- Check power: a hardware throttle axis may override the autothrottle, or the engines may not have reached commanded thrust.
- Check configuration: look for extended spoilers, excessive flap drag, landing gear or incorrect trim.
- Check airspeed and weather: low energy, a steep turn, windshear or a strong downdraught can create a real sink.
- Consider the aircraft’s GPWS model: simplified gauges may retain the wrong flight phase after a touch-and-go or react differently to radio height and scenery elevation.
Altitude callouts are separate from these protective alerts, a distinction explained in our guide to GPWS warnings and callouts in the default FSX 737. During simulator practice, use the same priority as a real crew: restore a safe climb first, then inspect the automation, configuration and warning logic.