How to Identify Pitot-Static System Failures During Flight

The Pitot-static system is very important for the safety of the aircraft and those onboard. The system is involved in powering instruments like: the airspeed indicator, altimeter, and vertical speed indicator (VSI).

When it comes to general aviation aircraft, this system is more prone to failures because of its lack of redundancy compared to larger, more complex aircraft.

Sometimes failures are caused by ice, debris, or often human oversight. Having a malfunction in the Pitot-static system can cause misleading instrument readings and that may put you in a dangerous situation.

That’s why learning about the system, recognizing signs of failure, and preparing for these scenarios are important and what we'll cover in this article.

SUMMARY

• The Pitot-static system powers flight instruments and is vulnerable to failures in general aviation aircraft because of environmental factors and human oversight.

• Recognizing failures involves learning the distinct symptoms caused by blocked Pitot tubes or static ports.

• Pilots can manage risks during failures by activating Pitot heat, using an alternate static source, and cross-checking other instruments.

• Regular pre-flight inspections, system maintenance, and preparing a failure response plan are the best ways to prevent Pitot-static issues.

Signs of Pitot-Static System Failures

It's important for pilots to be able to recognize a failure and that starts with understanding how the Pitot-static system works. The system relies on two pressure sources:

1. The Pitot tube for dynamic pressure (used by the airspeed indicator).

2. Static ports for static pressure (used by the altimeter and VSI).

Blockages that are in either of these component result in distinct symptoms. Let's cover these in the table below.

Okay, let's clarify these:

• A blocked Pitot tube only affects the airspeed indicator.

  Example: a completely blocked Pitot tube will cause the airspeed to behave like an altimeter, increasing as you climb and decreasing as you descend. If the drain hole is still open, airspeed will read zero.

• A blocked static port impacts multiple instruments. The altimeter and VSI will freeze, the airspeed indicator will show incorrect values depending on whether you’re above or below the altitude where the blockage occurred.

Common Causes of Pitot-Static Failures

The Pitot-static system can be vulnerable to a variety of external factors, and even small oversights can lead to malfunctions:

• Environmental Conditions

  Mud daubers or other insects can block the Pitot tube. There can also be ice and rainwater which can clog static ports, usually in winter.

• Human Oversight

  Pitot covers left on or tape accidentally covering static ports after washing the aircraft are pretty common pre-flight mistakes.

• Wear and Tear

  Over time, dirt or debris can accumulate in the system. This causes blockages that are not always immediately noticeable.

Actions Pilots Can Take During Failures

If a failure occurs mid-flight, first, try your best to stay calm and rely on your knowledge of the system. Take a deep breath and then begin to troubleshoot. Here are some steps to consider:

1. Activate Pitot Heat--If this is equipped in your aircraft, turn on the Pitot heat to clear ice from the Pitot tube.

2. Switch to Alternate Static Source--Many aircraft are equipped with an alternate static source. Activating it can restore functionality to the altimeter and vertical speed indicator.

3. Cross-Check Instruments--Use other instruments like GPS ground speed or known power settings to estimate airspeed and altitude.

4. Break the VSI Glass--As a last resort, breaking the vertical speed indicator glass can create a new static pressure reference. 

Preventing Pitot-Static Failures

The best way to avoid a Pitot-static failure is through thorough preparation and performing regular maintenance.

Pre-Flight Inspection

During your walkaround, check for obstructions in the Pitot tube and static ports. Tissues or gentle suction can help detect and remove water blockages.

Routine Maintenance

Clean the system regularly and replace components as needed. Make sure that Pitot and static covers are removed before flight.

Test Pitot Heat

Always check the Pitot heat function during pre-flight, especially in cold weather.

Make a Plan

When it boils down to it, preparation is the main key to handling pitot system failures. Before your next flight, try to quiz yourself:

• How would your instruments behave if the Pitot tube were blocked?

• Do you know when to activate the alternate static source?

• What adjustments should you make to your landing minimums?

Having a clear plan makes sure that you’re ready for any scenario. Remember, Pitot-static failures are more common than engine failures, and preparation can make all the difference.

Frequently Asked Questions

• How can I tell if my Pitot tube is blocked?
  If the airspeed indicator doesn’t increase during takeoff or behaves like an altimeter during climb and descent, the Pitot tube is likely blocked.

• Can a blocked static port affect my airspeed indicator?
  Yes. If the static port is blocked, the airspeed indicator will show lower speeds above the blockage altitude and higher speeds below it.

• What is the alternate static source?
  It’s an alternative air pressure source that bypasses the static port, often drawing air from the cabin to restore instrument functionality.

• Is breaking the VSI glass safe?
  Breaking the VSI glass is a last-resort option to restore static pressure and should only be done when other solutions are unavailable.

FAA's Pilot's Handbook of Aeronautical Knowledge The FAA Pilot's Handbook of Aeronautical Knowledge covers a broad knowledge base that pilots need throughout their initial and recurrent training. This handbook is intended for pilots preparing for Remote, Sport, Private, Commercial, or Flight Instructor Pilot Certificates.

Takeaway

The pitot-static system is an important tool and even if you never face a failure, practicing these steps will make you a better pilot. Plan for the unexpected and avoid thinking "it won't happen to me", be prepared for anything and review various safety methods you could perform during your flight. If you're a student in training, your flight instructor will likely run some scenarios with you to test how you handle losing one of your instrument panels. So, keep learning and planning.

For more tips on aviation safety and systems, check out our Pitot-Static System Guide.

Fly safe and stay prepared!

Interested in Aircraft Instruments?

Our guides are designed to help!

• Pitot-Static System: How does it work?

• How it Works: Airspeed Indicator (Extensive Guide)

• Aircraft Vertical Speed Indicator (VSI): How Does it Work?

• The 4 Types of Airspeed: How Each Works (Complete Guide)

• The Complete Guide to Aircraft Instruments [More Than Just the 6-Pack]

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