ITman quote,, A Boeing with similar problems..?
A LOT Polish Airlines Boeing 767-300, registration SP-LPA performing flight LO-2 from Chicago O'Hare,IL (USA) to Warsaw (Poland) with 206 passengers and 10 crew, was enroute at FL330 about 9nm eastsoutheast of North Bay,ON (Canada) about 70 minutes into the flight (Jun 19th 22:02L, Jun 20th 02:02Z), when the airplane encountered "severe turbulence at high speed" and started to deviate signficantly from assigned altitude. The crew reported later, that their airspeed had become unreliable and requested to divert to Toronto,ON (Canada). During descent towards Toronto the crew reported, that airspeed had returned to be normal and requested to hold to reduce weight. No ambulances were needed. While in the hold and descending, the crew was ordered to stop descent at 16000 feet, the crew was however unable to comply and reported, the airspeed problems had reoccured. The airplane proceeded directly for a safe landing on runway 23 73 minutes after the onset of problems and taxied to a gate.
At the time of the incident air traffic control reported continuous light chop (light turbulence) on all altitudes above FL300, later changed to severe turbulence at FL330 reported by a 763.
The Canadian TSB reported on Jun 22nd, that the airplane was enroute at FL330 near North Bay, when it experienced a sudden and uncommanded overspeed condition, stick shaker and illumination of the left and right hand engine electronic control (EEC) caution lights. The aircraft descended to FL280 before the situation was resolved. The airplane diverted to Toronto, where it landed without further incident. The TSB has dispatched investigators to the site.
Boeing, Airbus, Lockheed, Douglas, Gulfstream etc. etc..it doesn't matter who builds it. Every aircraft designed, with all equipment operating perfectly, will experience sudden air data and aerodynamic screwiness if running into bona fide severe turbulence, especially at high altitude. In this case, and uncommanded overspeed condition, a stick shaker (associated with an underspeed/high AOA) condition, and possible engine problems (EECs also use air data). If that aircraft had been at FL350 or FL370 (where it's aerodynamic margins were even smaller) and transited into the same level of turbulence, the situation would have been even dicier, especially if there is a sudden temperature change(s) (as there often is, affecting mach number and performance) associated with the area of shearing and/or vertical gusts. Sudden temp changes only compound the problem of airspeed control when trying to stay between narrow buffet margins.
The severe turbulence was unreported until that particular aircraft encountered it, and when it did there was no malfunction of systems at the time. The event, however, apparently caused one that recurred later, which is no suprise. There's no mention of icing, or malfunctioning/frozen pitot-static sources.
But there doesn't need to be, and there usually isn't, when similar events occur.
The pilots also reported that the aircraft was unable to hold assigned altitude (and one must assume this means the autopilot rate of response or pitch trim limits to turbulence-induced deviations were exceeded), but it doesn't say whether the A/P remained engaged throughout the event, was disengaged by the pilots and the recovery hand-flown, or disengaged itself (as designed if exceeding internally-designed parameters) for the descent. It sounds like the crew did a good job managing the recovery through a quick descent as the situation at altitude became aerodynamically untenable.
If the ongoing assumption that there could have been a pitot heat/ADIRU/etc malfunction on AF447s is acceptable to this thread, then I submit that a no-malfuction scenario is as much of a possiblity, if not moreso, given the area of weather in which the aircraft was lost.
Encountering ice-accrual of any significance that would exceed sublimation at FL350 outside a CB is an anomaly, with the coincidence of malfunctioning pitot heat making it a factor even more unlikely. On the other hand, the possibility of encountering moderate-to-severe turbulence in, around, or over developing hard-to-detect CBs (especially in a large, dynamic, steady state area of them where dissipating cells and ITCZ conditions feed developing ones) isn't, given the limitations of airborne weather radar.