CE560 Captain questions the evaluation methods of a Maintenance Controller when the Captain is asked to send a picture of a damaged nose tire via email.

Narrative

I discovered a chunk of rubber missing from the nose tire during preflight. Per Company procedures I call Maintenance Control to report the problem. Maintenance Controller Mr. X (normally a Citation X controller) took my call. The Excel controllers were apparently too busy at the time to take my call. He asked me to take a picture of the tire and send it to him. He did not ask me to send a write-up as I would normally expect. I complied and took the picture and sent it in via email. I also added in the email that I would also be sending in the discrepancy. My discrepancy was worded as follows: 'Evaluate nose tire for chunk of rubber missing.' I received a voice mail from Controller Mr. X asking me for additional information about the size of the missing chunk in order to deffer the tire and continue on in this condition. He also mentioned maintenance manual references for allowances to continue in such a condition. I did not answer this voice mail because by that time I had received a message stating maintenance had been initiated on the aircraft. First; I do not believe it is appropriate to request pictures in a scenario as described above. This is because it pressures the crew to accept a maintenance evaluation via the photograph. This is contrasted with a scenario that a controller asks for the write-up and a picture to help pinpoint the discrepancy. I do not believe that was the intent in this situation. Second; I do not believe it is safe (or permissible) to deffer a single wheel aircraft such as the Citation Excel. Controller Mr. X may have believed this was allowed since he is used to working Citation X aircraft that have dual tires. I believe when the situation was passed to the Excel maintenance controllers; they realized this was not permissible and initiated maintenance on the aircraft. Third; I do not believe it is in the interest of safety to use maintenance manual reference in conversations with pilots. The maintenance manual is a reference for the trained eye of a mechanic. If the discrepancy is within the limits of the maintenance manual; then the mechanic can note this in the corrective action and return the aircraft to service. Pilots may not correctly apply the limits prescribed in the maintenance manual and continue to fly the aircraft in an unsafe condition. Photos should only be requested by maintenance control along with a request for a written discrepancy report via normal methods.