Accurately Measuring Aircraft Fuel Levels with Tank Gauge Sticks

Measuring Fuel Quantity Accurately With Tank Gauge Sticks

Knowing how much fuel is in an aircraft's fuel tanks is critical for safe and efficient operations. While modern airliners rely on advanced electronic fuel quantity indication systems, many smaller general aviation aircraft still use simple tank gauge sticks as a backup or even primary means of measuring fuel levels.

What Are Tank Gauge Sticks?

A tank gauge stick, also referred to as a fuel dipstick or fuel measuring stick, is a long pole marked with calibration lines to show the quantity of fuel present in an aircraft's fuel tank when dipped into the tank. They provide a simple, low-tech, and reliable way to directly measure the depth of fuel inside a tank which can then be cross-checked against charts to determine volume.

Why Tank Gauge Sticks Are Still Used

While they are old school devices, fuel measuring sticks actually have some advantages over electronic fuel quantity systems:

• They are inexpensive, have no electronics to fail or maintain
• Provide a directly measured backup to electronic indicators which can malfunction
• Essential for validating fuel load and distribution in aircraft limited to basic instrumentation

For these reasons tank gauge sticks are still mandated equipment on many general aviation aircraft to this day. They are required by regulators to meet minimum equipment list (MEL) and other standards for basic backup instrumentation.

Using Tank Gauge Sticks Properly

While deceptively simple, using a manual fuel measuring stick correctly does require some technique and understanding on the part of the aircraft mechanic or pilot:

Consider Aircraft Angle

When inserted into the tank, the measurement markings on the stick assume the aircraft is in a normal level attitude. Allowance must be made if the aircraft is not level when taking a measurement.

Check for Contamination

The stick should be visually inspected for any residual fuel or contamination left over from previous use before being dipped to ensure an accurate reading.

Understand Temperature Effects

The density of aviation fuel changes with temperature, meaning the volume of fuel needed to reach a particular height mark on the stick will vary depending on how warm or cold it is. Charts are used to correct for this.

Read Marks at Eye Level

When removed from the tank, the fuel level is read off the stick by sighting the fuel marking horizontally across at eye level rather than from above or below where parallax error can affect accuracy.

Maintaining and Storing Tank Gauge Sticks

Fuel measuring sticks may be low tech but they are precision instruments that must be handled with care to maintain accuracy:

• Keep sticks clean and damage free
• Wipe dry and store protected after use
• Periodically inspect and verify calibration
• Replace if lost or damaged

The Future of Tank Gauge Sticks

Though firmly entrenched as essential backup devices, the days could be numbered for direct reading manual fuel measurement using dipsticks and charts. More aircraft are doing away with them in favor of easier electronic density compensation tanks which automatically determine volume from fuel height and temperature.

However for many smaller planes limited to basic instrumentation, the simple fuel stick will remain an important part of the pilot's toolkit for the foreseeable future.

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FAQs

What are tank gauge sticks used for?

Tank gauge sticks are used to physically measure and determine the quantity of fuel in an aircraft's fuel tanks. They serve as a backup to electronic fuel gauges.

How does reading fuel level on a tank gauge stick work?

The stick is marked with calibrated lines that indicate fuel volume when the wet fuel line is sighted horizontally at eye level. Allowance must be made for aircraft angle and fuel temperature.

Should tank gauge sticks be cleaned and maintained?

Yes. Tank gauge sticks should be kept clean, damage-free, and have their calibration periodically verified to ensure accuracy.

Are tank gauge sticks required equipment on aircraft?

Many general aviation aircraft must carry functional fuel measuring sticks to meet minimum equipment regulations for backup fuel quantity indication.