Emergency Operations
Authority and communication
91.3 gives the pilot in command authority to deviate from any rule in an emergency, and requires a report on request. Declare the emergency, squawk 7700, and remember aviate, navigate, communicate. Minimum fuel is a fuel state, not an emergency; declare a fuel emergency if the landing may be jeopardized. Know 7600 for lost communication and 7500 for unlawful interference.
Equipment failures
Have a plan for vacuum or electrical failure (partial panel), pitot-static failure (airspeed and altitude errors; the VSI is the first to react), alternator failure, and loss of gyros. In icing, act early: request a different altitude or routing rather than waiting; know that freezing rain implies supercooled large droplets. For smoke or fire, know the electrical and heating sources and the checklist order.
Lost communications
91.185 sets the rule. Route: last assigned, then vectors, then expected route (giving precedence to the route in a radar environment), then the filed route. Altitude: the highest of the last assigned altitude, the minimum IFR altitude for the segment, or the altitude ATC advised to expect. Time: leave the clearance limit at the EFC time; if none was given, leave on arrival and proceed to a fix from which an approach begins.
Worked example
Last assigned 6,000; MEA on the route 4,000; ATC said expect 8,000 at the fix. In lost communications you fly 8,000.
Trap: selecting the lowest or the last assigned altitude on a lost-communication question, and assuming the clearance limit may be departed immediately without regard to EFC.