I tend to agree I wouldn’t like to fly in severe turbulence. On the other hand I would expect that forecasting turbulence is similar to forecasting ice. I doubt it is possible to reliably predict the intensity. Does such wind really imply severe turbulence directly? I would think with stable laps rate and without sudden significant changes in wind speed and/or direction with altitude the air can be perfectly smooth 1000 ft above relatively flat terrain. Can be obviously different story over mountins and in unstable air mass.
@Flyer59 I’d love to hear some of those reports if you can share them.
Hi Honza,
My report of one of such encounters was here (analysis and photos further down).
Severe turbulence is unsafe by definition since it implies loss of control of the aircraft. Moderate implies temporary loss of control.
Turbulence will be where it will be but you can control the effect it has on you, by flying high enough.
At low level, for example, where I am based (EGKA) anytime the SFC wind is say 15-20kt, you can forget a scenic local flight (usually that means going around the Isle of Wight, or to Beachy Head – both along the coast) with “new to flying” passengers unless you can get above 3000ft. If you go inland, the base of Class A is 2500ft so a flight around the Gatwick zone is very rough. It will also be very rough on hot summer days, due to the rising air. Most people won’t enjoy it at all. Along the coast the base of CAS is 5500ft or more so you can get into smooth air but then you don’t see as much.
Over mountains, I have crossed the Alps many times and only once did I feel anything! I have done it with winds at my altitude of up to 30kt, but by flying at say FL180, versus the peaks being at FL110-120, there was nothing there. On the one occassion, it was quite gentle “waves” during the crossing and even Justine was fine with it. I have crossed the Pyrenees down the middle a number of times and once with 40kt of wind and there was zero turbulence at FL180 or so. Prior to my first trip down there I heard from a load of self appointed pilot forum one line tossing pompous experts (“young man, there are MOUNTAIN WAVES there and you need only one of those and you are DEAD” kind of crap, on UK’s main chat site which I hung out on for 10 years before setting up EuroGA with David) and as a result of that we flew to Wangen-Lachen and sat there for a few days (mostly in p1ssing rain and eating £20 sandwiches) until the wx over the Alps was nice. By the following year I realised I had been fed a load of crap, so went straight from Shoreham, over the Alps, to Trieste in N Italy. All this was VFR so limited access to CAS (meaning “zero” in Swiss Class C, so crossing the Alps at FL129). Sigmets? I have never looked at a Sigmet in my life. I look at the MSLPs and on that one it’s blindingly obvious the Alps are a no-go, but it isn’t due to winds 
So, in summary, I have never seen wx over the Alps where the wind would be too strong for the operating ceiling of the TB20 i.e. the quickly reachable FL190 but the flight would still be in nice VMC. Obviously, there are people who cross them 500ft above the peaks (I have heard some scary stories) and they will be very vulnerable to even light winds, say 10kt. Remember that if your operating ceiling is FL120 and you are at FL110, then your ability to deal with any downdraught is approximately zero…
Flyer59 wrote:
Do not fly into severe turbulence. Never. I have some reports from pilots who did, and they all regretted it …
I’m one of those who got into severe turbulence over mountains. Not something I care to repeat – ever. Losing control is scary, to put it mildly.
@honza: I would have cancelled that flight as well for the same reasons you mention.
Peter wrote:
“young man, there are MOUNTAIN WAVES there and you need only one of those and you are DEAD” kind of crap
Well, waves need the right conditions. They aren’t always there (although sailplanes pilots would love that). For one, the direction wind is blowing matters. Waves aren’t usually really dangerous in themselves, they won’t drive you into a range (issues with them usually involve IMC). And they are as smooth as silk. As long as you go along with them for a ride. However, where there are waves there are rotors and you might want to avoid those bad boys. Those can definitely kill you. You won’t encounter them flying high up. What you might encounter is a breaking wave. Nothing to trifle with either, they can be powerful enough to tear off tails, etc. It’s usually easy to spot a wave (and the large ones would show on satellite images), but they don’t always show (again, you need the right conditions).
Since i live close by the Alps, i hear many reports about turbulence, especially on many nice and sunny days when we have winds from the south and southwest.
Of course you don’t feel much in FL180 – but try flying to Innsbruck or Zell am See on the weong day – and you will not try again for some time.
I am very careful with turbulence. Passengers can get extremely scared by it. In 1999, on a sunny day, my (then) girlfriend got so scared on a flight from Split to Munich that she started crying. I didn’t feel too well too, and i was really glad when it was over. That was in FL120, i think. And that one was problem rather between moderate and severe, my guess at least. Psychologically it’s worse over mountains.
Aviathor wrote:
Severe turbulence is unsafe by definition since it implies loss of control of the aircraft. Moderate implies temporary loss of control.
Actually, the definition of moderate turbulence says that the aircraft is under control the whole time. In severe turbulence, the aircraft may be out of control briefly. If control is lost altogether, the turbulence is extreme.
The rule of thumb, and I would subscribe to it as it is promulgated by pilots operating in the Rockies, is if the wind at ridge height is above 25 knots, climb to clear the area by roughly half the height of the mountains (AGL), above the main peaks. This is probably at or below MEA for airways in the Alps.
Sparky Imeson’s Mountain flying bible is worth reading.
The FAA put out some useful short films, see below.
The rule of thumb, and I would subscribe to it as it is promulgated by pilots operating in the Rockies, is if the wind at ridge height is above 25 knots, climb to clear the area by roughly half the height of the mountains (AGL), above the main peaks. This is probably at or below MEA for airways in the Alps.
That translates to ~FL150 for most of the “middle” Alps (terrain to ~FL100) which is pretty well what I have been doing, and it worked for me. The airway MEAs are FL140-160.
Thanks for posting that movie… I was expecting a very young Clint Eastwood in there
