Re: Why do we always re-engineer our aircraft??
If you accept the main differences between the “air vehicle” and the “aircraft” are engines, avionics and weapons then;
a. Rolls Royce are excellent, quite apart from supporting UK industry and political factors.
b. As above, most UK avionics (except, in my experience, EW). Buying US sourced kit is easy, supporting it (80% of through life costs) is a nightmare.
c. I admit limited experience on weapons but what I have done has largely been governed by security aspects (as are airborne radars and to a lesser extent comms).
Interoperability – MoD has no real policy on, and cannot afford to be, interoperable with anyone other than UK forces, and even then that is merely an unfunded aspiration.
Functionality – The US routinely adds, and more importantly removes, functionality at the drop of a hat and usually without telling anyone. France is also notorious for this (Lynx, Gazelle, Puma). If we follow, we incur expensive, unnecessary and unplanned mods; if not, we fall behind and need to separately maintain an “old” build standard which is quickly obsolescent. To do that, we need master drawings, source code etc.
Standardisation – There is very little you can buy from the US that will simply plug and play in UK aircraft. They build to their standards, not ours.
Related to the above, we will always be a minor user to almost any US defence supplier and at the bottom of the food chain when it comes to buying spares, design changes etc.
Supportability – The first thing in any User Requirement for aircraft to be flown off CVS/RFA/SUS/DUS is “On Board Commonality”. They simply don’t have the space to carry rafts of spares, so we specify kit which is common to our aircraft, as far as possible. For example, until recently the 3 main aircraft on a CVS (SHAR, Merlin, AEW) required only two (huge) ATE suites. A third could not be squeezed in, so regardless of who wins any competition for the kit, they are directed to use one or other of these suites. If you look at the fit on these aircraft, you’ll see that in many cases the same kit, or variants thereof, is in at least two of them or capable of being tested on the same ATE. This is why Merlin has a mixture of avionics spanning the 70s, 80s and 90s. Its avionic fit hasn’t changed much since it was determined in 1983-ish. The downside is that much of it is now very old as the air vehicle part of the programme slipped a decade or so.
Obviously there is much more to this and I have simplified it somewhat, but I hope this helps. People do think about these things, but the common denominators are always politics and money.