Yes, the reaction forces should always be derived from statics. The starting point, however, are "prescribed" load factors. The source of those factors is, fundamentally, the FAA design and certification requirements. Somewhat equivalent to those are test standards such as DO-160, but I will put that aside for now because most of those tests are dynamic - and I don't think that's what you're asking about.
Back to the static loads: the monitor is destined to be installed in an aircraft. Items of mass, no matter what they are, must be restrained in a manner to prevent them from coming loose and posing a threat to the occupants of the aircraft under all conditions, including maneuvers, gusts, emergency landings, and so on. Obviously, the video monitor must not break loose! The FAA has defined what load factors apply to each situation, some subject to analysis by the aircraft designer, but in all cases you can use a "safe" value that will ensure you have a structure strong enough. The load factor will be multiplied by the weight of the unit. That will be the load, in a specific direction. Now the reaction forces can be derived from simple statics, and stress analysis will give you margin of safety, provided you know the strength of the mounting tray and hardware. If you don't know the strength of the hardware, then you're using the wrong hardware. Or maybe you skip detailed stress analysis by carrying out load tests (which is a good option if done systematically and observed carefully).
It's not really that simple, but that's where you have to start. If you know that your equipment is going to be installed in one specific aircraft, and no others, then you may want to research the aircraft's type design data, which will tell you its certification basis, and look up the design requirements from that section of the FAR's. There you will find the load factors I mentioned. Maybe that sounds easy, but it actually contains a large number of non-obvious steps to be taken. So I should step back a bit.
It sounds like this research process has already been done by your colleagues, they just haven't taken the time to show you yet. Hopefully what I've explained is enough to help you find what you need in the previous test plans. In time you will become more familiar with the terminology which will help a lot. If not, you're welcome to ask more questions.
There is a much more comprehensive explanation in FAA Advisory Circular 43.13-2b, should you care to look that up. It can be downloaded from the FAA website. Even if you are not in the USA, the process is the same in any other jurisdiction I know of (Europe, Canada, Australia, etc.).
STF
