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

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

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.