Force effects reference

The force pipeline ships with thirteen effects. Each runs as a separate sub-model feeding into a summing stage, after which a master gain and the master arm gate decide what actually reaches the stick. This page documents each effect: what it simulates, what telemetry drives it, and what you should hear / feel when it fires correctly.

1. Centring spring

Telemetry: G-load, airspeed, pitch/roll trim positions, control deflection
Output: Spring coefficient + centre offset, both axes
Key sliders: Base, G-gain, min clamp, max clamp, deadband

The force pulling your stick toward neutral. Stiffness grows with load factor, matching how a real stick behaves under G. Deadband widens at low airspeeds so the stick doesn't feel sticky at dead-centre on the ramp. The centre offset is shifted by elevator and aileron trim so a trimmed aircraft feels neutral when the stick is at the trimmed position.

2. Airspeed-loaded pitch force

Telemetry: Indicated airspeed, elevator deflection
Output: Constant force on the pitch axis
Key sliders: Pitch gain

Pushing or pulling the stick at cruise should feel like pushing against air. Force scales with airspeed squared and with how far the elevator is deflected from trim.

3. Airspeed-loaded roll force

Telemetry: Indicated airspeed, aileron deflection
Output: Constant force on the roll axis
Key sliders: Roll gain

Same idea as the pitch force but on the roll axis. Tuned independently because most airframes have asymmetric pitch-vs-roll authority.

4. Rate damping

Telemetry: Body-axis rotation rates (p, q)
Output: Opposing constant force proportional to rate
Key sliders: Rate-damping gain

Subtracts from the commanded pitch and roll forces in proportion to the current angular rate. This is what makes a sharp stick input decay back toward the trim point instead of ringing around it. Think viscous damping.

5. Autopilot back-drive

Telemetry: Autopilot-on, AP commanded pitch/roll
Output: Spring centre shift toward AP command
Key sliders: Back-drive gain, rate limit

When the autopilot is engaged, the centring spring's centre tracks the AP's commanded deflection, rate-limited so it moves at a plausible speed. Grab the stick while AP is on and you'll feel it resist in the direction the AP is demanding.

6. Runway rumble

Telemetry: On-ground, ground speed, surface type enum
Output: Continuous periodic force
Key sliders: Rumble gain

Scales with ground speed and the surface-type enum. Grass and gravel are roughly 1.5–1.9× a paved runway; ice is about 0.3–0.5×. Fires only when on-ground is true.

7. Touchdown thump

Telemetry: On-ground (transition)
Output: Single impulse
Key sliders: Thump gain

A single, firm impulse the moment the on-ground flag flips to true. Tuned so a greaser feels softer than a firm arrival, but not by much — it's a fixed amplitude multiplied by the vertical speed at touchdown.

8. Brake shudder

Telemetry: Brake pedal deflection, on-ground
Output: Continuous low-frequency rumble
Key sliders: Brake-shudder gain

Amplitude scales with brake pedal pressure. Gated on-ground so airborne braking doesn't fire it.

9. Gear bumps

Telemetry: Ground speed, on-ground
Output: Repeated short impulses
Key sliders: Bump gain, frequency

Separate from the continuous runway rumble — these are discrete “taxiway seams and paint” bumps. Tuned to feel natural under 40 kt; above that, the continuous rumble dominates.

10. Aero buffets (stall / overspeed / Mach / spoiler / turbulence)

Telemetry: AoA, stall warning, overspeed warning, spoiler handle, airspeed, G-load rolling stddev
Output: Periodic force with a randomised envelope
Key sliders: One gain per sub-effect

This is really five sub-effects sharing a buffet generator.

Stall buffet. Builds progressively as AoA crosses a low threshold and saturates at the sim's stall warning.
Overspeed buffet. Triggers on the sim's overspeed flag. Sharper frequency than stall.
Mach buffet. Fires at high altitude + high Mach; useful on jets.
Spoiler buffet. Scales with spoiler handle position times airspeed.
Turbulence overlay. Uses rolling standard deviation of G-load as a turbulence proxy, feeding a low-amplitude broadband jitter.

11. Engine rumble

Telemetry: Per-engine RPM percent, combustion flag
Output: Continuous periodic force
Key sliders: Engine-rumble gain

Scales with per-engine RPM percent — a four-engine aircraft with one engine dead produces 75% the rumble of one with all four running. Gated by the engine's combustion flag so shutting an engine down silences its share.

12. Reverse-thrust rumble

Telemetry: Reverse-thrust engaged flag, ground speed
Output: Continuous low-frequency rumble, scaled by ground speed
Key sliders: Reverse-rumble gain

Rollout feel after touchdown with reversers deployed. Tapers off below ~30 kt.

13. Mechanical one-shots

Telemetry: Gear handle position (transitions), flap handle index (transitions)
Output: Single impulse per transition
Key sliders: Gear-deploy gain, flap-step gain

A gear-deploy shudder fires on any gear-handle move. A flap-step shudder fires on any non-zero step — both extension and retraction. (Early v1 fired only on extension; a bug that we fixed on the port.)

Safety gate: stale-telemetry watchdog

Not a user-tunable effect but important to know: if telemetry stops flowing (sim crashed, unplugged the network cable, whatever), every dynamic force fades to zero over a short ramp and stays there until the stream resumes. No stuck forces, no last-known-state zombies.

Combined output

All thirteen effects sum into two outputs — a pitch force and a roll force — plus the spring parameters. Master gain is applied last. The Dashboard shows the final summed output; the small effect-active badges below the force bars let you see which effects are actually contributing at any instant.