Well, trying to take these one at a time...
Originally Posted by
IAN-UK
Always good to hear from an expert.
But just wondered what parameters could define the scale of turbulence if not intensity and duration.
Well, strap yourself in for the bore fest - if you were talking to an aeronautical design engineer, you'd be into discrete or continuous turbulence/gust models with velocity gradients, 1-cosine profiles and...zzzz. These are basically all about how the aircraft structure experiences accelerations, and what these do in terms of basic strength of the aircraft and how it flexes and bends. Whereas aircrew are generally (in the US at least) directed to categorise turbulence anecdotally by strength and how often it is felt (Light, Moderate, Severe / Occasional, Intermittent, Continuous). This is typically about bumpiness (light chop), or deviations from speed or altitude. A good rule of thumb is that moderate turbulence has you pushing against your straps and unsecured objects get knocked around, whereas severe turbulence is where you’re forced against your straps and unsecured articles are thrown around. Extreme turbulence is where you momentarily lose control of the aircraft, and potentially damage the airframe. In theory the authorities ask aircraft manufacturers to expect this sort of level only once in every 70,000 flying hours.
Originally Posted by
henkybaby
How do these to match? Is it a serious incident with hospitalisations or was it not very comfortable for a few seconds?
Just wondering. Also spoke to the pilot on my DOH-AMS flight (a very British Nigel) and he said that he would be very surprised if they hit a mountain wave on that course, as there are hills but no mountains on the northerly approach.
Apparently mountain waves are what makes even the most experienced pilot a bit nervous.
It was both – if you were strapped in, it was momentarily unpleasant. Those standing or walking around were thrown around however, and for them it was far worse obviously.
Mountain waves are scary, especially in light aircraft, more because the vertical speed of the air mass can quickly exceed your ability to climb when in the downward element of the wave – i.e. you are forced down. This isn’t generally an issue for large aircraft, because they have far more excess thrust, and fly fast enough to clear the area quite quickly.
Originally Posted by
VivoPerLei
Being a math and physics person, when I start gripping the seat rests I immediately start trying to solve the problem in my head. There must be a technical way of reducing the effects of turbulence on aircraft flight. Right?
There’s a very simple way to do so, and that’s to reduce the energy you enter turbulence with – in other words, to slow down. The aircraft has a nominated speed (determined by the manufacturer for the aircraft type when it’s first designed) at which it will in principle optimally ride turbulence. The nearest analogy I can give is that it’s a bit like driving over a speed bump quickly or slowly – if you go fast it’s quite jarring. If you slow down, you still move around, but it’s less rough (subjectively speaking).
Originally Posted by
simonrp84
It was a convective storm that caused this issue, not mountain waves.
Quite possible – I was relating that the only time I have felt similar conditions was in mountain wave. The episode was shortly after Top of Descent, as we were about to descend in to the undercast. Convective activity is quite possible therefore, especially if we were unlucky enough to catch the edge of the ‘hammer’. That being said, you’d normally spot these areas on the weather radar. We were a little way south of Clermont Ferrand, which I recall has some smallish (circa 5000ft?) hills.
Anyway, well handled by the crew, and the Captain was especially good about reassuring folk. A very considered approach.