Turbulence speed again:
BOAC:
- err - those two don't quite join up! Is M.65 acceptable? M.82? As long as you have the right N1's of course......................
NB For youngsters - N1's do NOT provide buffet boundaries.
Think about what severe turbulence implies. Airspeed variations of maybe 30 knots! I find it quite irrelevant to talk about a "target" airspeed in such a situation. One should be happy to see a speed in the normal range and react only to an unacceptable airspeed trend (note that it's not the "trend vector" indication that is being referred to, but the general meaning of the word, development/change). That would mean a trend were it would likely be predictable that it would take you outside the normal range.
So depending on altitude and what the trend is, I would say that both the number you mention may be acceptable.
For the record I never experienced severe turbulence in the Boeing. Neither did Boeing during the test flights:
"The maximum degree of turbulence encountered at the pilot’s station during certification flight tests was evaluated as moderate."
So you are pretty much on you own. Do what you have to do to survive (remember with severe turbulence, aircraft may be temporary out of control).
With climb and descent you have the luxury that you can trade altitude to absorb the speed variations, hence it makes sense to choose an airspeed that is in the approximately center of the speed band. In level flight you don't have that luxury, which Boeing acknowledges with their described technique in the FCOM1 and FCTM.
Anyway, again the point is that .76 is not a magical speed that will give you a smoother ride in level flight in light turbulence.