What is the best method for testing the pitot heat in an aircraft?

The best method for testing the pitot heat in an aircraft is to ensure that the ammeter is showing negative. This is because the pitot heat system draws a significant amount of electrical current when it is activated. When the pitot heat is turned on, it should create a load on the electrical system that the ammeter can detect. A negative reading typically indicates that the system is drawing power correctly, which suggests that the pitot heat is functioning as intended. This method allows the pilot or technician to verify that the system is operational without having to physically inspect the pitot tube or test the temperature gauge under potential flight conditions.

While other options may seem like valid checks, they do not provide direct confirmation of the pitot heat system's performance. For example, audible alarms typically relate to other systems, examining the pitot tube for ice is a post-operation concern rather than testing functionality, and verifying the temperature gauge reading may not accurately reflect the system's operation due to lag or calibration issues. Thus, monitoring the ammeter provides a clear, immediate indication of the pitot heat's activation and operational status.