In the Fixed Third-Person View (activated by pressing F9 three times while undocked), it is not possible to turbo.

Since it is possible to turbo in all three other views, this seems to be a bug.

I often try to switch between views while turboing, but because of this bug, it is very difficult to switch between views and turbo at the same time.

-- DekuDekuplex Ornitier

That view is meant for taking pictures, not actual flight--you can't control your ship in that mode. I bet you could get your ship to turbo if you used a turbo lock bind, though.

Actually, this is because of a bug (and one that I discovered!). Back in the good old pre-beta days, turboing in fixed third-person view didn't drain any energy. Because they were unable to track down the reason this happened, the devs just removed turbo in that view. For some reason, they never put it back in.

PS: No, turbo-lock won't help.