Find out why FLCH causes a steep climb, how speed and thrust drive pitch, and which settings stop abrupt pitch-up or an autopilot stall.
In flight simulators, FLCH can command a steep climb because it uses pitch to maintain selected airspeed while climb thrust is applied. A low speed target, engagement above that target, light aircraft weight or excess thrust makes the autopilot raise the nose sharply; FLCH does not hold a fixed vertical speed.
This is general autopilot behaviour across Microsoft Flight Simulator, X-Plane, Prepar3D and FSX. The label may be FLC, FLCH or LVL CHG, while the exact thrust logic depends on the aircraft: some systems command thrust automatically, whereas others expect the pilot to set power.
What makes FLCH pitch up so aggressively?
The selected airspeed is FLCH mode's main pitch reference. If the aircraft is flying faster than the selected speed when FLCH engages, the autopilot may pitch up to exchange speed for altitude until it reaches that target.
Once the speed stabilises, available excess power determines the climb rate. Strong climb thrust, low altitude and a light aircraft can produce a high nose attitude and climb rate while the selected speed remains steady. Our detailed explanation of FLC pitch-to-speed logic covers the underlying mode behaviour.
| What you see | Likely cause | What to check |
|---|---|---|
| Immediate pitch-up after engaging FLCH | Selected speed is below actual speed | Compare the speed window or bug with indicated airspeed |
| High climb rate with stable airspeed | Excess thrust, low altitude or light weight | Confirm power setting, payload and fuel load |
| Pitch change near the IAS/Mach transition | The speed reference or target changed | Verify whether the system is controlling IAS or Mach |
| Airspeed falls below target while pitch keeps increasing | Wrong active mode, insufficient thrust or faulty add-on logic | Read the Flight Mode Annunciator and check thrust status |
How do I stop a steep climb in FLCH?
- Read the Flight Mode Annunciator. Confirm that FLCH, FLC or LVL CHG is genuinely active. If the display shows vertical speed, take-off guidance or another pitch mode, changing the FLCH settings will not correct it.
- Compare actual and selected airspeed. A target well below the present speed commands deceleration through pitch. Select an appropriate climb speed within the aircraft's operating and configuration limits; do not select an artificially low speed to reduce the climb rate, because that usually increases pitch.
- Check who controls thrust. In a jet with coupled autothrottle, confirm that the expected climb-thrust mode is active. In aircraft where FLC controls only pitch, set the recommended climb power manually. Also check that a physical throttle axis is not overriding the automated command.
- Verify configuration and loading. Confirm that gear and flaps follow the intended climb schedule and that payload, fuel and centre-of-gravity entries are plausible. A lightly loaded aircraft at high power will climb more aggressively than a heavy one at the same selected speed.
- Select the appropriate vertical mode. If you need a specific rate rather than maximum available climb performance, use vertical-speed mode with a safe speed margin and active thrust monitoring.
- Disconnect if the pitch becomes unsafe. Lower the angle of attack, establish a safe airspeed and power setting, then re-engage automation only after the aircraft is stable.
Changing the selected altitude alone will not soften the climb. That setting tells FLCH where to level off, not how quickly to get there.
Should I use FLCH or vertical-speed mode?
Use FLCH when maintaining climb speed matters more than holding a particular climb rate; use vertical-speed mode when the required rate is the priority and sufficient speed margin is available.
- FLCH/FLC/LVL CHG: pitch targets airspeed, while vertical speed becomes the result of thrust, weight and atmospheric conditions.
- Vertical speed: pitch targets the selected climb rate, so airspeed can decay if available thrust is insufficient.
- VNAV: use it when the aircraft must follow an FMS climb profile and altitude constraints, provided the route and performance data are correctly configured.
The division of responsibility varies between aircraft, so check our explanation of how airspeed control and autothrottle work together. Do not switch to vertical speed merely to hide a low-speed problem; that mode may keep demanding the selected climb rate while the aircraft approaches a stall.
Is a steep FLCH climb normal?
A steep FLCH climb is usually normal when the airspeed settles on target, the expected pitch and thrust modes remain annunciated, and no low-speed or angle-of-attack warning appears. A high vertical speed by itself does not indicate a fault.
Investigate the aircraft or add-on when airspeed continues falling below the target, pitch or trim oscillates, thrust behaves unexpectedly, or the problem appears only under time acceleration. Control-binding conflicts, unrealistic loading, an incorrect aircraft state and incomplete autopilot modelling are common simulator-specific causes.
If the stall warning activates, disconnect the autopilot, reduce angle of attack and apply appropriate thrust rather than waiting for FLCH to recover. Our guidance on diagnosing an autopilot climb that approaches a stall explains the next checks.