Declaring, or not declaring your emergency, the following from Eldorado's post
Flying past Amarillo once, IFR, I heard a Southwest airline declare an an emergency while enroute, with engine problems. From that moment on, all the pilot had to do was fly the airplane. The controllers were providing vectors, frequencies, altitudes, I do believe the pilots hardly had to look for or at the approach plate. I don’t know what impressed me more, the pilots willingness to ask for information on the approach without looking it up or the controllers willingness to provide what was asked for or what they thought might be helpful. This was when paper plates were all that was available, and Amarillo was not the destination. Again, I doubt the pilots were more concerned with flying and troubleshooting, let the controllers provide frequency, courses, altitudes, etc.
My first event was a fire in the radio stack of a C172, near RDU. I described my problem, they gave me every assistance that they could have, and my sons in the back seat, unaware of the problem, were excited to see 2 fire trucks, an ambulance, and a red station wagon pacing us on the grass beside the runway. 5 airliners were lined up on the taxiway for departure, and at least one landing had been waved off to give me an immediate landing.
The second, again in a C172, The engine went violently rough, so bad it broke all the copper ground bond straps across the engine mounts. I called Maguire AFB advised the problem, they waved off a 4 engine transport they had just cleared to land, and gave me cleared to land. I requested vectors to the nearest civilian airport, which was Miller, we calculated that at my current loss rate, I would arrive at 3 to 4 thousand feet, and they gave me vectors all the way. Altitude is a very valuable asset, I was at 8,000 feet when this started out.
Third, Pensacola, Florida, the seal on the crank let go, and covered the plane with dirty oil. I notified the tower, they radar vectored me to the outer marker, and gave distance out as I made an ILS approach using the frequency they provided. No other planes inconvenienced.
I have had only one experience where I had an in flight problem, that ATC did not treat me just the same as an air carrier plane. There has never been any papers to fill out.
The moral here is fully advise ATC what your problem is, and they will do all they can to get you safely to the ground. Note that I did not declare and emergency, nor did they make it one. We just worked together to find what I needed to get safely on the ground. If they did not give me what I needed, I would declare an emergency, but that was never necessary.