I probably fit the example that many of you describe above. Undoubtedly, my age is less than the duration of many of your engineering careers.
I was hired to run a mfg. plant, not something too many recent graduates are prepared to deal with. For a time, I felt nigh unethical for taking a job that I felt unprepared for. (engineering degree sans management courses)
I'd guess that the technical knowledge requirement probably depends on the type of project. It's not too smart to have Mr. Civil Greenie head-up work on a bridge project or watershed dam or something similar.
That said, the message I got from the leadership that hired me is that a young (inexperienced) person is less biased going into a management project; no bad habits to unlearn. Sometimes ignorance serves to simplify. Also a young (inexperienced) person cannot just "do it myself!" if a team member is lazy or inefficient. That manager will ride, err... motivate everyone, because he knows he couldn't get it done otherwise!
Also, having a a young (inexperienced) person at the head often creates a team dynamic immediately, as then the team members are almost certain to all share one thing in common at that point: utter disgust "that such a young, wet behind the ears, babyface is leading
my project!" I'm really not joking there, I've seen it!
Probably the number one motivating factor to hire young or inexperienced is economics. It's cheaper to hire an unknown with potential (that may or may not fail) than to go after a veteran with 20+ years experience carrying a large overhead with him (that may or may not fail). Unwise logic? Maybe, but its reality in some low-margin industries!
If the team is put together properly, there will be several members who serve to oversee that all the calcs check out, all the "i"s are dotted, and that efficient and compliant design is achieved. That doesn't always fall soley on the guy at the top of the pile.
Very few of my posts to these fora are technical in nature- reason being, I have almost nothing to offer and much to learn. (and I do, from many of you people!) A heartfelt thank you for sharing your insight and knowledge.