What occurs if the SPDS is in FLT mode while on the ground?

When the SPDS (Signal Processing and Data System) is set to FLT mode while the aircraft is on the ground, the system is essentially in a state that's intended for flight operations, which is not suitable for ground conditions. This can lead to inadvertent transmissions as the system may attempt to send out signals or messages that are meant for airborne operations. This can create confusion and potentially interfere with ground communications or the operations of ground services that rely on clear signal processing.

In contrast, the other options would imply more severe failures or operational impacts that are not directly related to the SPDS's mode in relation to ground operations. While ground communication not being available might seem plausible, the primary issue centered around FLT mode is the risk of unintended transmissions occurring during a time when the system should be inactive or in a ground-appropriate mode.