Propwash tuning: practical D and feedforward

Propwash is the quad fighting its own turbulent air in hard turns, dives, and quick reversals. The prop disc moves through messy airflow, especially when throttle drops while the frame is still pitched hard. Pilots feel it as sink, bounce, rear washout, or a vague "it won't stay on the line." It is not always "too much P" and almost never fixed by copying someone's PID screenshot from Discord.

When NOT to propwash-tune

Propwash tuning: practical D and feedforward: When NOT to propwash-tune

Situation	Real issue
Problem only on one corner	Bent prop, weak motor, loose arm
Bad everywhere including hover	Mechanical or base tune, Betaflight basics
Motors scorching	Heat / amp margin, lighter props, not more D
New heavy GoPro mount, no retune	Mass and resonance changed, remount or accept tradeoff
Only in DVR, fine in goggles	Camera mount flex, camera angle

Propwash tuning assumes a quad that hovers clean and only misbehaves in aggressive maneuvers. If hover is wrong, fix hover first.

What propwash looks like in logs

In Blackbox, propwash often appears when:

Throttle decays during a hard turn or flip exit
Setpoint changes fast but gyro lags in the recovery phase
D-term spikes if you already run high D, heat follows

Zoom to one power loop or split-S. If the ugly section does not overlap stick movement and falling throttle, you might be chasing the wrong problem.

Symptom map

Feel	Direction to explore
Nose drops in fast descent	Throttle/mix habits; I term on pitch; tune after camera tilt
Oscillation in turn exit	D term or filtering; motor heat, hot climate
Sluggish correction, "mush" in flips	Feedforward up slightly; check over-filtering
Wash on quick reversals	Mechanical props; then FF and D together cautiously
Bounce after flip	D low or P high; also check prop bite and battery sag
Rear sinks in tight corner	Throttle management; pitch FF/I; not always PID

Pilot input matters: propwash is physics plus tune. Dropping throttle too early in a corner guarantees sink, no FF saves bad timing.

Maneuver-specific notes

Maneuver	Feel	Fix order
Power loop	Rear sink on exit	Throttle carry; then pitch FF/D
Split-S	Late roll catch	Roll FF, not yaw P
Quick 180	Wash on reversal	Props; small roll FF; no mid-roll throttle chop

Log one maneuver per session, not power-loop and split-S fixes in the same afternoon.

Bad habit	Looks like	Fix first
Chop throttle in corner	Sink, rear wash	Carry throttle longer
Full idle in drop	Mush	Feather, not zero

D-term in propwash

More D can calm oscillations in propwash recovery, it opposes rapid rate changes. But D adds noise sensitivity and motor heat. In Indian summer, aggressive D on a noisy gyro is how you touch-test ESCs.

D change	Good when	Bad when
Small +D on pitch/roll	Clean gyro, bounce on exit	Already hot motors, noisy raw gyro
-D	Fine buzz after turns, heat	Sloppy overshoot everywhere
+D without filter check	Never	Always, pair with filter review

Pair D changes with filter review, not blind +10 on all axes. RPM filter may let you run useful D with less heat if telemetry is solid.

Feedforward

FF pushes the quad toward stick intent faster, it anticipates setpoint change instead of waiting for error to build. Helps tracking in flips, snappy freestyle, and quick roll reversals.

FF change	Good when	Bad when
Small +FF on roll/pitch	Sluggish snap, lag in logs	Already twitchy, noisy build
-FF	Oscillation on stick starts	Mush everywhere
Large +FF	Rarely	Masks bad P; worsens noise

Too much FF feels twitchy and can worsen noise, especially on lightweight 3" rigs. FF is not "free snap."

I-term note: heavy I on pitch can fight dives, sometimes less I helps propwash in downward lines, sometimes you need I for camera-heavy noses. Change I only when logs show sustained offset, not momentary wash.

Process

Propwash tuning: practical D and feedforward: Process

1. Confirm hover and cruise are acceptable
2. Log ONE maneuver, power loop or hard 180
3. Fix mechanicals (props, bolts, mounts)
4. Small FF bump OR small D bump, not both large at once
5. Same battery class, same spot, A/B same line
6. Stop after 2–3 changes per session, fresh eyes tomorrow

Rates interaction: high super rates demand faster tracking: FF often matters more than another P point. See rates and expo presets before blaming PID.

Common mistakes

Copying "propwash tune" PID with different weight, props, or filters
+15 D and +15 FF in one save
Tuning propwash on pack 1 with a full battery, voltage sag changes line 2
Ignoring throttle technique in dives
Adding P when the issue is recovery oscillation (often D/filter)

When to stop

If the quad tracks well on 80% of your lines and only washes on absurd camera-tilt dives, stop. Perfect propwash-free freestyle on 5" is a gradient, not a checkbox.

If nothing improves after conservative FF/D and filters are sane, try slightly lighter props or accept that your motor KV / load is at the edge for that style.

Workflow after a crash

Hard hits change props and motors, propwash feel often drifts before hover feel does. After a session ender, see tuning after a crash before a propwash PID binge.

India field note

Afternoon heat pushes battery sag harder than cool morning packs, humid air is actually less dense than dry air at the same temperature, so monsoon humidity is not the propwash knob. A tune that cleared propwash on a fresh 6S at 28 °C may need conservative D or shade between packs at 40 °C, not necessarily more PID. Fly the same test line when validating.

If three conservative changes on the same line show no improvement, stop, check motor load or mechanicals. Propwash at amp headroom limits is physics, not a missing PID point.

Quick session checklist

□ Hover clean, motors cool
□ One test line named (e.g. "left power loop")
□ One knob per save, FF or D, not both large
□ DVR or Blackbox on that line only
□ Motor temp before next change

Magic numbers from forums are starting points for their weight and props, not yours. One maneuver, one knob, one log. Propwash tuning is iterative and boring; that is why it works.