What does a pilot need to do when they have a communication failure on a SID?

When a pilot experiences a communication failure while on a Standard Instrument Departure (SID), the appropriate action is to fly the SID as published until unable. This procedure is based on the principle that the pilot should continue to follow the predetermined routing and altitude profile, which is designed to ensure safety and maintain standardization in the flow of traffic departing from an airport.

Following the published SID allows the pilot to remain in compliance with air traffic procedures, ensuring that they remain predictable in their flight path. This is crucial because the SID is designed to provide safe separation between departing aircraft and to integrate into the broader airspace structure.

While it might seem reasonable to consider other options, maintaining the last assigned altitude without following the SID could lead to inefficient or unsafe flight paths. Returning to the departure airport or reporting the failure to a control tower is also not feasible because, in cases of communication failure, the pilot would typically not have the ability to communicate effectively. Therefore, adhering to the published SID until it becomes impossible to do so is the most appropriate and safe response in this scenario.