If you are busy, here’s the condensed version: If you operate a turbine business aircraft and reliability is a key metric, unless you have 24/7 maintenance on the airport, you need an A&P on your staff.
If there is a service center at home station and they provide quality service and are knowledgeable about your aircraft model, it can be cost effective to have the service center perform the maintenance rather than employ a full-time maintenance person. Especially if that service center operates around the clock, or close to it. If you don't fall under that scenario, here are three reasons for having an A&P on your staff.
No one knows your aircraft better than your own A&P. That person gets to know the maintenance that was performed, the issues that the aircraft may have had in the past, and who/where to get the answers when maintenance questions arise. This is important in keeping the aircraft reliable and ready for flight when needed.
The in-house A&P understands your mission. Being your employee, she is fully dedicated to keeping your aircraft airworthy and safe. You will not get a better level of service than having a great employee as your A&P. They can earn back their salary in getting one critical mission off the ground on time.
When your aircraft is in for heavy maintenance, you're A&P is also your advocate in keeping the aircraft maintenance on time and within budget. While a good service center makes every effort to get the job done on time, the personal attention from your A&P will make that much more likely to happen.
The older and more complex your aircraft, the more critical it is to have the A&P on your staff. As with any aircraft, there may be minor issues that can delay your departure. The A&P being immediately available will enable a high level of dispatch reliability. In-house maintenance staff gives you the dedicated response on your schedule and is there to serve just you.
One of our clients has a 30+ year-old twin turboprop. Their limited budget includes a skilled A&P. Their dispatch reliability is in excess of 95% and their downtime due to unscheduled maintenance is far lower than you'd expect from an old aircraft. The maintenance manuals for their plane have notes and annotations representing the years of accumulated knowledge on how to maintain their aircraft. In these and many other cases, having the A&P on staff provides a level of skill and knowledge that enables the operator to maximize the utility of their aircraft.
I've heard from a number of operators that their A&P's salary was paid for at the first major inspection. Having the A&P on staff is cheap insurance for an on time departure. This further enables the executives to conduct their business in the most efficient manner.