Some of the comments on this business simply beggar belief!
Imagining any security hazard from allowing access to the flight deck under such circumstances indicates not just a shortfall in but a complete absence of understanding of both the nature and appreciation of the risks involved in non crew access to the light deck.
Suggesting its better to get CC to read a checklist is better/safer/more desirable than having a pilot - even a PPL - in the second seat is hard to comprehend - how could it possibly be better to have a non pilot there than a pilot, even if he is not qualified on type? I cannot think of a single reason.
Suggesting that said pilot needs to be qualified and current on type again beggars belief. Why? You'd turn away a type rated man because he was not current? Holy sheet! You'd turn away a Dash 7 FO if that was all you had to pick from? I can't understand that. Especially if you put a cabin crew in the seat instead - that would be crazy!
Even a PPL understands the use, importance and protocols of checklist use, cabin crew don't. I know this is an old chestnut but surely getting someone with no knowledge to participate in a checklist is more hazardous than using someone who has some knowledge? Personally I think it's far - vastly - more likely to end in confusion if you use CC than if you do it on your own if there's no one else to help. But give me a PPL over that - at least he knows about lookout, can listen to RT, read an altimeter, identify a runway etc.
Oh - and why "only" 2 pilots Newark to Frankfurt? I take it some of the opinions here aren't from pilots - can't think why they are posting here in that case. Buddy, ever heard of Ryanair, Easyjet etc? They fly 5 days per week with duties 30% longer than that - with 2 pilots. As do scores of other airlines.
Haven't some people just let rampant paranoia and out-of-context "security" dogma take over their judgment? Scary.
Isn't all this just the most basic airmanship?
Oops! Bugger! I said it again. I'll get my coat...