As the saying goes: 'it is better to have and not need, than to need and not have.' Many pilots have a reluctance to declare a 'pan' or a 'mayday' and then find themselves in a worsening situation. There is a catch 22 situation. Pilots don't declare emergency situations because they feel that the dispatch of emergency services isn't justified for thier particular problem. Most Atco's dispatch the emergency services due to the knowledge that pilots are often reluctant to declare a formal emergency. The sistuation could be solved if pilots would declare formal emergencies or just admit that they were getting into difficulty, then controllers wouldnt have to 'second guess' the pilots and the true servicability of their aircraft in flight.
TS