Pitot-Static System Errors

How the Pitot-Static System Works

The pitot-static system uses two main sources: the pitot tube (measuring total pressure) and static ports (measuring static pressure). These feed information to instruments such as the airspeed indicator, altimeter, and vertical speed indicator.

Common Pitot-Static System Errors

Errors arise mainly from blockages or leaks in the pitot tube or static ports. These can be caused by ice, dirt, insects, or mechanical failure. Pitot tubes are typically electrically heated to prevent ice formation, but static ports may or may not be heated depending on aircraft type.

Blocked Pitot Tube Symptoms

• If the pitot tube is blocked but the drain hole is clear, the airspeed indicator reads zero.
• If both the pitot tube and drain hole are blocked, the airspeed indicator acts like an altimeter, showing changes as altitude changes but not actual airspeed.

Static Port Blockage

• If the static port is blocked, all three instruments (airspeed, altimeter, VSI) are affected:
  • Airspeed indicator gives erroneous readings (overreads in descent, underreads in climb).
  • Altimeter freezes at the value where the blockage occurred.
  • VSI remains at zero regardless of actual rate of climb or descent.

Causes of Pitot-Static Errors

• Ice formation (if heating fails or is not switched on)
• Blockage by foreign objects (insects, dirt)
• Mechanical damage
• Leaks in the system

Recognising and Managing Failures

Pilots must be alert to unusual instrument behaviour, especially during icing conditions or after suspected bird/insect strikes. Proper use of pitot/static heat and regular inspections are key to prevention.