212,
I went to War in Huey's and Chinooks....neither were built to the later UTTAS Spec....and we saw the results.
Those lessons were what was the driver behind that new Spec.
In doing a small research project re the ways my Army Flight School Classmates died in Vietnam....the words "burns", "burned", "post crash fire", "caught fire and crashed" figured way too often.
One example of sensitive a helicopter can be to a single 7.62 round can be.....on the Chinook each flight control Servo (Jack) on each rotor head has two hydraulic lines separated by armor plate to prevent both lines being severed with a single bullet.
An aircraft in my unit....took several hits to include one round the severed on of the lines a Servo and dented the other.....had not that armor plate been there we would have lost an aircraft, the five man crew, and the twenty odd passengers.
That demonstrated the value of armor but also difficulties in determining what the design should be to afford sufficient protection.
Protection of systems comes not only from the installation of armor (with serious weight being added) to something as simple as the way hydraulic lines and other systems components are routed and installed which adds much less weight.
One look at a Blackhawk rotor head and push pull tubes and all of the lugs they are connected to....compared to a Huey and you can see immediately what the difference is due to the Spec.
The Blackhawk fuel tank drop test that had to be met is probably the most telling difference between the Huey Spec and the BlackHawk Spec.
I can offer first commentary on what the results of being hit by 7.62 and .51 Caliber rounds can be and what some of the results can be.
The Army and Sikorsky spec'd, designed, tested, and fielded a first class combat helicopter in the UH-60 Blackhawk.....and have improved that design since its first days.
I love the Huey....and after flying. other helicopters I described my late flying in the Huey as being like dancing with an old Girl Friend.
If I were to have to go to War again....my choice of horses would not be anything else but the Blackhawk if the choices were the same candidates the MoD is looking at to replace the Puma.