Turbulence penetration speed

[Fursty Ferret]

A transient overspeed in the cruise is a non-event bar a tech log entry. A stall or pre-stall buffet is a totally different kettle of fish and will require a lot more paperwork, as well as being far more risky. It's believed that several 787s have been through the sound barrier with zero ill effects other than new underwear required for the flight crew.

[lederhosen]

It will depend on the aircraft and the airline, but over many years on the 737 my experience was that in most cases of turbulence it was pretty simple to set a speed in the middle of the allowable range. If the weight and altitude meant that the range was a bit tight you asked for descent to a lower level. Maybe I was lucky but I cannot ever remember coming close to pre stall buffet. Whereas in the days when fuel was a lot cheaper cruising often at Mach .81 we would regularly go into overspeed. Whilst it was no big deal it was a lot easier to keep off the safety pilot's radar by dialling the Mach back a bit.

[FullWings]

I think the key here is Severe turbulence. In my entire airline career, I have only encountered it twice, once in a 737 and later in a 777. The second instance had the stall warning and overspeed going off simultaneously and the instruments very difficult to read, so the speed was only really an average, over which I had almost no control at all until it was over.

Some fly around at turbulence speeds a lot, just in case, and some have never felt the need. I was exposed to the whole spectrum of opinion so probably fall more into the latter camp. If I had a report from an aircraft in front of Severe, then I would get everyone sat down and the speed appropriate, assuming I couldn’t avoid it laterally or vertically. Rest of the time I put it somewhere in the middle where it generates the least paperwork...

[sonicbum]

Originally Posted by felixthecat

No, it was light to moderate at worst.
My FCOM Limitations makes no distinction with severe turbulence it states “ The turbulence penetration speed is 290-310KIAS/.82-.85M, whichever is lower”

So in the case of turbulence in my case, or in your case severe turbulence you would accelerate to the turbulence penetration speed? Where would that be referenced?

Many thanks

Don’t know what type you are flying, but considering the usual range of Vs1g across the modern narrow/wide body airliners currently flying around the globe, in order to g-buffet or g-stall the aircraft at 270 kias you would need to hit a g-load close to or more likely exceeding the airplane structural limitation, which would mean more than severe turbulence. We are obviously talking about medium to low altitude handling, I.e. well within the subsonic regime.

[safetypee]

When discussing possible stall and speed excursion, neither is likely to be a classic, textbook event. If at all, only a transient, which may not be noticed amongst the features of a severe turbulence encounter.
It is important to remember that flying constant attitude is the primary task in wind-shear, not stall or overspeed recovery.

For info:-
https://research.reading.ac.uk/scena...-warmer-world/

A reminder to reconsider the basis of judgements about turbulence; any past experience or training may not be a good guide in future operations.

[alrabgi]

Captain

Originally Posted by felixthecat

This is a question I thought I knew the answer too….

During a training detail, in the the decent I was around 270kts. I was quite happy since the turbulence limitation on type was 290-310KIAS /.82 -.85M.
I was told that I had to speed up to the turbulence penetration speed….ie 290-310kts.

This didn’t make sense to me and when I queried it later on the ground I was told that that is the penetration speed. I had never though about turbulence speed being an issue if you were below it and had a large margin on minimum stall speed. I have always though of it as a structural maximum speed. It still doesn't seem correct to me but I am often wrong……could someone please explain this to me and point me in the direction of a reference to an explanation of this situation.

Many thanks

in jet aircraft best speed to fly in turbulence halfway between Vmin Vmo mmo
at max wight max alt speed penetration will be halfway now if lower alt or wight speed margin will increase so you will have lower speed to fly in turbulence speed which protect you from high and low speed stall and passenger convenience