Personal experience.
We were in a Boeing 707 in VFR conditions on top of active thunder-storms. At the first jolt of a strong updraft we disconnected the autopilot. The second updraft pitched the aircraft into a 20-25 nose high attitude. There was little or no increase in g, or zoom in altitude! The aircraft's momentum carried it along on its projected flight path, in this attitude. Because we had a visual horizon we were able to ease the nose back down to the horizon and continue on course, without further incident.
Northwest 705 accident.
The crew were flying a Boeing 720B, 8 feet shorter than a 707. (A shorter moment arm to oppose a pitchup). They were climbing up to their altitude, trying to avoid the heavy turbulence in an active thunderstorm area. The aircraft was pitched up into a 30-35 degree nose high attitude by a strong updraft. Due to the strong vertical updraft, the application of forward pitch control had little effect in changing the aircaft's attitude. The crew then applied full nose down horizontal stabilizer trim, with minimum effect. Upon exiting the pitchup and returning to a normal relative wind condition the position of the flight controls pitched the aircraft over into a steep dive, and it broke up in the air.
NASA says that an updraft can extend up to 15 miles in diameter.
The members of the CAB investigation team could not understand why the crew held the flight controls in the nose down position for such a long time period.
Both gyro's nose down stops showed severe impact damage.
Last edited by wsherif1; 7th Jan 2005 at 06:33.