What occurs when the environmental control system in an aircraft fails?

When the environmental control system in an aircraft fails, the thermal regulation loss indeed poses a significant risk to the cockpit environment, making it unsafe for both the pilot and crew. This system is crucial for maintaining appropriate temperatures, particularly at high altitudes where external temperatures can be extremely low. Without proper thermal regulation, the cockpit can become uncomfortably hot or cold, leading to impaired performance, increased workload, and potential hypoxia due to a lack of oxygen. Managing cockpit conditions is vital for safe aircraft operations, hence the failure of this system directly impacts safety.

The other options, while they may describe issues that can occur in various scenarios, do not directly relate to the consequences of an environmental control system failure. For instance, inundation with water is not a typical result of such a failure; flight instruments functioning might be unaffected as they rely on power rather than temperature control; and an automatic emergency landing could occur due to many reasons but is not an immediate consequence of just an environmental control system malfunction.