Funny Clouds

[Maddie]

Hello All.

I flew over from Dublin to Birmingham, early this afternoon. About 13 minute before touchdown, the seatbelt sign came on and we encountered one very sharp jolt to the aircraft, accompanied by screams from many paxs including myself. It was all over in about 10 seconds thankfully. However, what I noticed was that there was a lot of vertical shaped clouds around. The best way I could describe them is like a 99 icream.

I travel usually about twice a week and have been for almost 4 years now, however, I have never noticed clouds like this before.

Has anybody any idea what type of clouds they were and whether they contributed to the short sharp turbulence.

Many thanks.

Maddie

[RingwaySam]

From Wikipedia;

Vertical Clouds (Family D)

These clouds can have strong up-currents, rise far above their bases and form at many heights.


Sam

[PAPI-74]

Possibly Towering Cumulus (TCU) which can be either visable or imbedded in other cloud. They have isolated up currents in the middle and cold downdraughts towards the edge.
If the pilot had his weather radar on, they should paint (show up on the screen) and he would ask ATC for haeding changes to avoid.
13 mins before touchdown means you were below 10'000 feet and in busy airspace. If the cloud was assessed as a low risk, it may be ok to clip it or reduce speed and just fly through it.
I personally will always try and avoid TCU due to the level of Icing and Turbulance associated but this can happen anywhere to the side as well.
Have a look at cloudappreciationsociety.org

[TightSlot]

Possibly... you crossed the wake of another aircraft?

[Hartington]

I had the same thought as TightSlot. Many years ago I was riding in a 757 jumpseat at a lower altitude (probably 4/5k) on approach to LHR when we hit a single violent jolt and the captain commented it was probably a wake.

[Maddie]

Hi All

Thank you so much for your replies. You will never know how much it helps me when I am flying. I am genuinely still very nervous and fly out of necessity not for pleasure.

Can I just ask one further question if we cross the wake of another plane, can that be dangerous? Is that the same concept as 'dirty air' and maybe I have the wrong term here. I am thinking of the plane crash that happened close to New York just after 9/11. There is something at the back of my mind that a contributory factor to that accident was the fact that the airplane took off very quickly after another very large jet and that it encountered severe turbulence from the wake of the previous plane.

My apologies if I am completely on the wrong track.

[Rainboe]

Maddie, I have been a prof pilot for over 36 years and nearly 20,000 flying hours. I have flown through numerous wakes. Over that time they have become recognised as a risk for smaller aeroplanes following larger ones at low altitude and speed, and ATC have guidelines to follow about separating flights which are adequate. At altitude and speed, they are no problem whatsoever, but the sudden jolt can surprise people. I have flown up the core of a vortex following a 747 in a medium jet- again, no problem. The accident you refer to would have been no problem- what caused the structural failure was a seriously misguided pilot reaction to it overstressing the aeroplane- the Airbus would have flown through unscathed, so it is unfair to assume that a vortex encounter caused the accident. Those of us that have learnt how to properly handle such an encounter would have had no problem, and that is how almost every pilot would have hadled it, and out of that accident, I think those peculiar handling techniques are no longer an issue.

Whilst they may feel unpleasant, they are no more than small boats reacting to larger vessel wakes- a few seconds rocking and no more risk than that.

[DrKev]

they are no more than small boats reacting to larger vessel wakes- a few seconds rocking and no more risk than that

Bravo! As close as is possible to the perfect analogy. Understates the discomfort to the passengers but sums up the situation beautifully. Well done! :D

[strake]

I'm not sure if Rainboe ever was a PPL or whether he just metamorphosed onto the flight deck:) However, if he can remember that far back, perhaps he can recall the simple pleasure gained from executing a perfect rate 1 360 and proving it with the little bump...?

[Maude Charlee]

If you encounter your own wake in still air in a 'perfect' rate 1 360, then you must have descended, as that is where your wake will be after 2 mins. :} So, not perfect at all then. ;)

As for wake encounters, crossing another aircraft's wake is very much like driving too quickly over a speed hump, whereas being caught up in a preceeding aircraft's wake is an altogether more unpleasant experience as it can last for several seconds and is similar to turbulence associated with convective clouds/weather. Think what it must be like to be inside a giant cocktail shaker. :ooh:

[strake]

Well, gosh..there you are then. There's me thinking that I was doing so well all those years ago and believing my instructor and now you've gone and burst my bubble, so to speak, maude charlee. Mind you, I have also managed to bump a few times on renewals as well so hmmm...
Eager and young, eyes riveted to the horizon over the firewall of my Robin HR waiting for the bump. Perhaps I can console myself by suggesting that it was summer so maybe not still air or maybe, in truth, I was going round a bit quicker than I thought...:)

[RingwaySam]

Just found this on YT about Wake Turbulence, quite amazing what it can do.

http://www.youtube.com/watch?v=6VwjLtRleCk

[skydriller]

Eager and young, eyes riveted to the horizon over the firewall of my Robin HR waiting for the bump. Perhaps I can console myself by suggesting that it was summer so maybe not still air or maybe, in truth, I was going round a bit quicker than I thought...

Dont think Ive ever felt the "bump" while doing anything as shallow as a rate one.......however, in the CAP-10, my aeros instructor reckons Im doing OK if we "bump" while doing full power turns or when looping....:ok:

...So strake, I think they must have been abit quicker than rate one turns eh?:E

Regards, SD..