Weight saving in aircraft
Saving weight is what life is all about when you start the original design process of any aircraft. This applies whether the aircraft is one powered by rubber that you wind up as a kid or is the next generation airliner or combat aircraft. Unless you are totally ruthless about weight the resulting aircraft will be hopelessly out performed by any competitors.
Judging the weight benefits and penalties in the design stage is where the skill comes in. Once you have an aircraft to ground test and later flight test then we start to get the benefit of hindsight as to whether the design choices were flawed.
While it is NOW as obvious as the balls on a dog that the 787 battery choices have produced more penalties than benefits criticising the original choice on the lines of “everybody knows those things are trouble etc” is easy but does not reflect what went on at the paper design stage. I am quite sure one of the battery people might well have preferred NiCads (or whatever) but I am also sure another guy wanted more weight in the bracket that the main gear is fixed to. Detailed designers are conservative people who do not want their part of the design to let down the team.
Enter the chief designer. If he allowed every designer to have his conservative choice they would probably have to strengthen the hangar floor. So where does he draw the line? – because it is HE who has to draw it. If he does not push towards the dodgy end of the spectrum we would never have got the continually better aeroplanes that the world has seen for the last 100 years.
Working on a VTO aircraft in the early 60s I asked the chief designer why on earth the cockpit had to be so low because it was going to ruin the rearwards view and he replied “to save aluminium on the fuselage sides”. At the time I thought he was wrong. Later I understood his problem and where he was coming from.