What is the main concern when the standby magnetic compass is used with powered equipment?

When using the standby magnetic compass in conjunction with powered equipment, the primary concern revolves around altered accuracy. The standby magnetic compass functions by detecting the Earth's magnetic field to determine direction. However, the operation of powered equipment can generate electromagnetic interference, which can distort the magnetic field around the compass. This interference causes the compass readings to be less reliable, potentially leading to navigation errors if the user is relying heavily on the compass for directional information during flight or boating.

Other potential issues, such as increased weight or higher fuel consumption, are not directly influenced by the use of a standby magnetic compass. Similarly, while having powered equipment could arguably impact navigation capabilities in various ways, it does not inherently decrease these capabilities as more reliable instruments and systems usually exist to compensate for any difficulty presented by magnetic interference.