The heating elements of the pitot heat are powered by which of the following?

• A. Compressor discharge air
• B. 26 VAC
• C. 115 VAC
• D. 28 VDC

Answer: (D)

The heating elements of the pitot heat system are powered by 28 VDC. This is the correct choice because pitot heat is used to prevent ice formation on the pitot tube, essential for accurate airspeed readings in aircraft. The use of 28 VDC is standard in many aircraft electrical systems for various heating elements, as this voltage is compatible with the electrical architecture of the aircraft and provides sufficient power for heating without causing damage to sensitive components.

Other options do not apply here. For instance, while 115 VAC is commonly used for other types of aircraft systems, it is not utilized for pitot heat, as high AC voltages are typically not suitable for these specific applications. Compressor discharge air is a source of pneumatic power but is not used for electrical heating elements. Finally, 26 VAC does not align with the standard voltage ratings typically found in aircraft heating systems and thus is not the correct power source for pitot heat.