docs(autotune): fix fixed-wing autotune docs to match actual behavior

[sensei-hacker]

The fixed-wing AUTOTUNE documentation no longer matched the current implementation in src/main/flight/pid_autotune.c. A user reported confusion after their rates changed significantly during an AUTOTUNE flight, which they didn't expect based on the docs.

Changes
Corrected the pre-flight parameter table: roll_rate/pitch_rate/yaw_rate are described as fixed limits AUTOTUNE respects, but by default (fw_autotune_rate_adjustment = AUTO) AUTOTUNE actively rewrites them while flying. Documented all three fw_autotune_* settings that control this.
Removed the claim that AUTOTUNE sets P and I gains - that formula (P/I/D derived from FF) was removed from the code in 2021 (9dcf985, "Don't change P, I and D during autotune"). AUTOTUNE only ever tunes FeedForward gain and, conditionally, rate.
Added yaw to the flying instructions - the code tunes yaw identically to roll/pitch (own FF, own rate, own minimum rate floor), but the doc only described roll/pitch maneuvers.
Documented the flight-mode dependency: rate is tuned in ACRO/HORIZON but not ANGLE mode (FF still is), and AUTOTUNE has no effect at all - not even FeedForward - while flying in MANUAL mode (pid.c:881).

[qodo-code-review]

PR Summary by Qodo

Fix fixed-wing AUTOTUNE docs to match current tuning behavior

📝 Documentation 🕐 10-20 Minutes

AI Description

• Document that AUTOTUNE tunes FF on all axes, never P/I gains.
• Clarify when/why AUTOTUNE rewrites roll/pitch/yaw rates during flight.
• Add yaw and flight-mode constraints, including MANUAL-mode no-op.

High-Level Assessment

The PR correctly aligns the documentation with current AUTOTUNE behavior (FF-only tuning, conditional rate adjustment, and MANUAL-mode no-op). For a docs-only fix, this direct rewrite is the most effective approach; alternatives like partial notes or addendums would likely preserve confusion.

Files changed (1) +20 / -11

Documentation (1) +20 / -11

Autotune - fixedwing.mdAlign fixed-wing AUTOTUNE docs with actual tuning logic +20/-11

Align fixed-wing AUTOTUNE docs with actual tuning logic

• Updates the AUTOTUNE description to reflect that it tunes FeedForward on roll/pitch/yaw, never P/I gains. Clarifies that rate tuning depends on flight mode and 'fw_autotune_rate_adjustment', and adds missing guidance about yaw maneuvers and MANUAL-mode having no effect.

docs/Autotune - fixedwing.md

[qodo-code-review]

Code Review by Qodo

🐞 Bugs (1) 📘 Rule violations (0) 📜 Skill insights (0)

1. LIMIT rate can rebound 🐞 Bug ≡ Correctness

Description

The docs say fw_autotune_rate_adjustment=LIMIT "only ever lowers" rates, but the implementation
can also increase a previously-lowered rate again (while still capping it at the initial rate).
Users may therefore still observe roll_rate/pitch_rate/yaw_rate increases during a LIMIT
autotune flight, contradicting the doc.

Code

docs/Autotune - fixedwing.md[27]

+fw_autotune_rate_adjustment | Controls whether/how AUTOTUNE changes `roll_rate`/`pitch_rate`/`yaw_rate` while tuning. `AUTO` (default) raises or lowers rates to match what the plane can achieve. `LIMIT` only ever lowers them, never above what you started with. `FIXED` leaves rates untouched - use this if you want AUTOTUNE to tune FeedForward only

Evidence

In the fixed-wing autotune algorithm, maxRateSetting is adjusted both upward and downward based on
rateFullStick. In non-AUTO modes (including LIMIT), the final applied rate is constrained to a
maximum of MAX(initialRate, minRate), which allows increases back up to the initial rate even if
the rate was previously reduced.

src/main/flight/pid_autotune.c[214-224]
src/main/flight/pid_autotune.c[118-123]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

## Issue description
`docs/Autotune - fixedwing.md` currently states that `fw_autotune_rate_adjustment=LIMIT` "only ever lowers" the rates. In the code, rate adjustment can step up or down by 10 dps based on measured capability; in LIMIT mode it is merely *capped* at the starting rate (and can rise back toward that cap).

## Issue Context
This is documentation-only, but it can still mislead users who choose LIMIT expecting a strictly one-way decrease.

## Fix Focus Areas
- docs/Autotune - fixedwing.md[27-27]

Suggested wording example:
- Replace "LIMIT only ever lowers them" with something like "LIMIT will not increase rates above the starting values (but may raise a previously-lowered rate back up to that cap)."

ⓘ Copy this prompt and use it to remediate the issue with your preferred AI generation tools

---

[qodo-code-review]

1. Limit rate can rebound 🐞 Bug ≡ Correctness

The docs say fw_autotune_rate_adjustment=LIMIT "only ever lowers" rates, but the implementation
can also increase a previously-lowered rate again (while still capping it at the initial rate).
Users may therefore still observe roll_rate/pitch_rate/yaw_rate increases during a LIMIT
autotune flight, contradicting the doc.

Agent Prompt

## Issue description
`docs/Autotune - fixedwing.md` currently states that `fw_autotune_rate_adjustment=LIMIT` "only ever lowers" the rates. In the code, rate adjustment can step up or down by 10 dps based on measured capability; in LIMIT mode it is merely *capped* at the starting rate (and can rise back toward that cap).

## Issue Context
This is documentation-only, but it can still mislead users who choose LIMIT expecting a strictly one-way decrease.

## Fix Focus Areas
- docs/Autotune - fixedwing.md[27-27]

Suggested wording example:
- Replace "LIMIT only ever lowers them" with something like "LIMIT will not increase rates above the starting values (but may raise a previously-lowered rate back up to that cap)."

ⓘ Copy this prompt and use it to remediate the issue with your preferred AI generation tools