Originally Posted by
Dan Winterland
the 747 up to F20 on both Classic and 400.
Allowed, but "not recommended" for F25 and F30 on the 744. I've done it on occasion, but it does give a significant descent rate along with a lot of rumble from the turbulence. Not a lot of practical-use situations (e.g., speed restricted, intercept glide path from above)...