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Warnings and Alerts

OnSpeed provides three types of warnings in addition to the normal AOA tone progression.

Stall Warning

What you hear: Rapid high-pitched pulsing (1600 Hz) at 20 pulses per second — a continuous buzz.

When it sounds: AOA exceeds the stall warning threshold for the current flap setting (approximately 90% or more of the wing's maximum lift capability).

What to do: Unload for control — reduce AOA immediately. Ease forward pressure, add power, reduce bank angle. The wing is at or near its aerodynamic limit and cannot produce more lift. The only recovery is reducing the demand on it.

Never ignore the stall warning

The stall warning is the most critical safety feature of the system. It sounds even when audio is muted (if IAS is above the mute threshold). Always respond immediately. Do not attempt to "pull through" a maneuver when the stall warning is active.

Stall Warning in Muted Mode

If you've pressed the mute button to silence normal tones, the stall warning still sounds — but only if both conditions are met:

  1. AOA is above the stall warning threshold
  2. IAS is above the mute-under-IAS setting (default: 25 knots)

The IAS check prevents false stall warnings on the ground or during taxi in windy conditions.

Stall Warning and Maneuvering

The stall warning activates at the same AOA regardless of airspeed, bank angle, or G-loading. This means it will activate at a higher airspeed in a steep turn than in wings-level flight — exactly when you need it. The airspeed at which the stall warning sounds is not fixed; the AOA at which it sounds is.

Vno Overspeed Chime

What you hear: A distinct chime, repeating at a configured interval (default: every 3 seconds).

When it sounds: IAS exceeds your aircraft's Vno (max structural cruising speed).

What to do: Reduce power and/or adjust pitch to bring airspeed below Vno. Operating above Vno in turbulence risks structural damage.

Configuration

  • Vno Speed: Set to your aircraft's published Vno (knots)
  • Chime Interval: How often the chime repeats (default: 3 seconds)
  • Chime Enabled: Can be disabled if not desired

G-Limit Warning

What you hear: A G-limit warning tone.

When it sounds: The measured G-loading exceeds the configured positive or negative G-limit.

What to do: Relax back pressure (for positive G) or push forward (for negative G) to return within the G-limit envelope.

Relationship to Maneuvering Speed

Maneuvering speed (VA) is the speed below which the airplane will reach its aerodynamic limit (stall) before exceeding its structural G-limit. In fractional-lift terms, VA occurs when fractional lift equals the reciprocal of the airplane's G-limit:

  • Normal category (3.8G): VA corresponds to ~26% fractional lift
  • Utility category (4.4G): VA corresponds to ~23% fractional lift
  • Aerobatic category (6.0G): VA corresponds to ~17% fractional lift

Below these lift fractions (higher airspeeds), it is possible to reach the structural G-limit before the aerodynamic limit. The G-limit warning protects against this.

Configuration

  • Positive G-Limit: Set to your aircraft's maximum positive load factor (e.g., +3.8G for normal category, +6.0G for aerobatic)
  • Negative G-Limit: Set to your aircraft's maximum negative load factor (e.g., -1.52G for normal category)
  • Over-G Warning Enabled: Can be disabled if not desired

Audio Test Tones

During the AUDIOTEST sequence, you'll hear various tones including:

  • "OnSpeed enabled" announcement — played on power-up
  • Calibration mode tone — indicates calibration wizard is active
  • Calibration saved tone — confirms calibration data was saved
  • Data mark tone — brief tone when a data mark is placed in the log

These are not warnings — they're system status indicators.

Unexpected Audio Behavior

If you hear tones when you shouldn't (e.g., in cruise) or don't hear them when you should (e.g., on approach):

  1. Check calibration — poor calibration can put setpoints at the wrong AOA values
  2. Check flap detection — if the wrong flap position is selected, the wrong setpoints are active
  3. Check sensor biases — drift in pressure biases can shift the AOA reading
  4. Check for moisture — water in pneumatic lines causes erratic pressure readings

See Troubleshooting for detailed diagnosis steps.