Originally Posted by
slats11
Can anyone advise what happens to barometric pressure within a strong updraft at typical cruise levels. I have not come across a definitive answer to this. Some articles describe increased barometric pressure, Others describe a reduced barometric pressure (which is assumed to be the explanation for the high apparent rate of "climb" reportedly seen in this incident).
Just wondering what pressure difference (if any) the static ports see as you enter a strong updraft.
The plane is obviously pushed up by the updraft. But it would be confusing if the static ports sensed increased pressure. At the same time as the plane was being pushed up, the altitude would decrease and the AP would presumably increase pitch and power to recover this lost altitude.
According to research I have read which tends to be biased toward effects on the ground, the air pressure is lower in the updraft than ambient and higher in the downdraft. However, the changes don't appear to be significant enough to provide alarming changes perhaps a few millibars (HPA). I would be more concerned about sudden temperature changes that may fox the ADIRU algorithms for Mach No. and could cause a sudden overspeed indication. Those more knowledgeable in that area could perhaps jump in. However, I have heard of aircraft systems taking emergency overspeed protection action on OAT changes.
The severe updraft itself could have been up to 10,000fpm (100Kts) if you add that to a sudden protection initiated nose up pitch so uncommanded and unexpected by the crew - things could have got suddenly quite exciting. The cold airframe could have hit liquid rain in the updraft which could immediately freeze on the very cold aircraft surfaces and static and pitot ports. I presume at the same time ECAM would have 'helpfully'
been alerting to several urgent issues with alarms going off (overspeed then stall and pressure instrument failure?) this could have been followed by the aircraft at high pitch flying into a downdraft of 10,000fpm down - all of this IMC. Not a pretty thought.
This is why the advice is not to fly near or into severe storms.