Find out why your aircraft will not descend when you reduce power in a flight simulator, with clear fixes for autopilot, trim and excess airspeed.
Reducing power does not command a descent in a flight simulator; it removes thrust. If the aircraft is trimmed nose-up, the autopilot is holding altitude, or it has excess airspeed, it may stay level briefly, slow down, or pitch up instead. Lower the nose, cancel altitude hold if appropriate, stabilise the target airspeed, and retrim.
Why doesn't reducing power automatically lower the nose?
Less thrust changes the aircraft's energy balance, not its selected flight path. In steady level flight, thrust roughly balances drag and lift roughly balances weight. After a power reduction, a fixed-wing aircraft can remain close to level for several seconds while losing airspeed.
The pilot or autopilot can also maintain altitude by increasing angle of attack. That exchanges airspeed for lift until the aircraft is allowed to descend or reaches a stall. Do not keep raising the nose merely to stop a descent; monitor airspeed and lower the nose before the aircraft becomes too slow.
Power changes can produce different pitching reactions according to thrust-line position, engine location, propeller slipstream and trim. There is no universal rule that pulling the throttle must make every aircraft's nose drop immediately. Our explanation of how pitch, power and trim work together covers this relationship in more detail.
How do I start a controlled descent?
To begin a controlled descent, establish a descent attitude and use power and trim to stabilise the desired airspeed and flight path.
- Check who is controlling the aircraft. Look at the autopilot mode annunciator and confirm that altitude hold, autothrottle or an AI flying aid is not opposing your input.
- Verify that engine power actually decreased. Watch the relevant engine indications, not only the cockpit lever. With a constant-speed propeller, RPM may remain governed while manifold pressure falls; turbine aircraft may use N1 or EPR where fitted.
- Lower the nose slightly. Use the horizon or attitude indicator to establish a modest descent attitude. Avoid a large push that creates an overspeed.
- Capture the target airspeed. Use pitch to correct the developing airspeed trend and power to refine the descent rate or path. Pitch and power remain coupled, so expect to make small adjustments to both.
- Retrim the aircraft. Trim away sustained control pressure only after the attitude and speed are close to correct. Trim should not be used as the primary descent control.
- Confirm the result. Cross-check the altimeter, vertical-speed trend and airspeed. A vertical-speed indicator can lag, so do not chase its first movement.
During an approach, configuration and runway path also matter. Our guidance on coordinating engine power with the approach path explains when to adjust power rather than keep pushing the nose down.
What if the autopilot is holding altitude?
An autopilot in ALT or ALT HOLD mode will actively prevent the commanded descent. When power is reduced, it normally pitches up to preserve altitude, causing airspeed to fall; an active autothrottle may instead restore power.
On most systems, turning the selected-altitude knob to a lower value does not by itself start the descent. Select the lower altitude, engage the appropriate vertical mode, set a sensible target, and verify the active mode on the annunciator.
| Mode | What it controls | Main risk or requirement |
|---|---|---|
ALT | Maintains altitude with pitch | Reducing power can cause severe airspeed loss rather than descent |
VS | Maintains selected vertical speed | Airspeed may not be protected; monitor it continuously |
FLC or FLCH | Uses pitch to target airspeed while changing altitude | Requires a lower selected altitude and appropriate thrust |
VNAV | Follows a calculated vertical profile | Needs a valid route, constraints and an active descent path |
Exact mode logic varies between aircraft and add-ons. Treat the flight-mode annunciator as the source of truth, rather than assuming that a button press was accepted.
What should I check if it still will not descend?
A power-off aircraft cannot remain level indefinitely in still air, so a persistent refusal to descend points to a control, configuration, weather or simulator-state issue.
- The power lever moves but engine output stays high. Disengage autothrottle or AI assistance, check for duplicated throttle-axis assignments and confirm that you moved the throttle rather than the propeller or mixture control.
- The nose rises while airspeed falls. Check for altitude hold, excessive nose-up trim or an autopilot servo still controlling pitch. FSX users can follow our steps for diagnosing trim settings and duplicate assignments.
- The aircraft descends only shallowly at idle. A clean, efficient aircraft can retain energy for a long time. If a steeper descent is required without excessive airspeed, use approved drag devices or configuration changes within their operating limits.
- The aircraft floats near the runway. Excess approach speed and ground effect are usually responsible. Do not force it onto the runway; stabilise earlier or go around if the remaining distance is inadequate. See our guidance on controlling the landing descent and flare.
- The vertical-speed indicator remains near zero. Check whether the altimeter is actually decreasing and allow for instrument lag or display filtering.
- The altitude is completely frozen. Check for active pause, slew mode, replay mode or an instructor position-freeze function.
- A light aircraft remains level at very low power. Strong rising air, thermals or ridge lift can support it. Move away from the lift or increase the commanded descent while keeping a safe airspeed.