Planes always create turbulence whether they’re descending or not. I see no reason to think they’d create more turbulence because they’re descending, assuming they maintain the same speed.
Big iron drivers, do big heavy slippery airliners or bizz jets that cruise at .89 Mach or some such, which may be just under the never exceed speed, try to maintain that speed down hill that close to the wall? Or do they? Slightest bobble could make you a test pilot pretty quick???
IMO, they do not maintain the same speed and since the total angle of attack will likely be less than level flight, if they don’t drag a foot, I would think the over all clear air turbulence created would be less.
YMMV
Well sure, but if they’re consuming less fuel to generate the same turbulence the energy’s coming from somewhere else.
There’s a big difference between how medium and bigger planes are flown to how light planes are flown. It’s partly due to how they are designed, tested, and certified and partly due to the jet engine factor.
In a light plane, as I know you know, the airspeed indicator typically has a big yellow arc that terminates at the red Vne line. The basic concept is that you only fly in the yellow range in smooth conditions and you never ever go over the never exceed line. Most light planes I’ve flown don’t have the power to cruise in the yellow arc so you typically only enter it on the descent, and then only if it’s a nice day.
Large turboprops and jets aren’t like that. There is no yellow arc and the red line is not a never exceed speed but a max operating speed (Vmo), it is also not a fixed mark but a striped “barbers pole” that is defined by indicated airspeed at low altitude and Mach number at high altitude, in other words it moves. The difference is subtle but significant. Any speed up to and including the barbers pole is fine even in light turbulence (something wouldn’t do in a light plane). In moderate turbulence you would slow down a bit but really only to avoid inadvertently busting the barbers pole and for passenger comfort. In severe turbulence you fly your turbulence penetration speed which is designed to give adequate margin over both your stall speed and Vmo.
The consequence of busting Vmo is pretty much nothing. The horn goes, you slow down and carry on, you write an incident report later so that the safety department don’t get upset at you for not reporting (they find out because all flight data is downloaded and monitored for things such as overspeeds).
So, to answer your question, there’s nothing technically stopping you from cruising and descending with the airspeed needle a hair off the barbers pole. The speed you actually cruise and descend at will be dictated by company SOP. Our SOP is to cruise for fuel conservation unless we are late in which case we can increase to the barbers pole and we descend at 280 knots indicated which gives a 25 knot buffer on the pole or if ATC want us to go faster we can go up to 290 knots. A big limit for us though is the autopilot is not particularly precise and descending at 290 can have the speed getting close to or exceeding Vmo at times. But as I say it’s not a big deal, you just slow down.
In the Dash 8 it was standard to fly the barbers pole all the way down to the circuit.
As for wake, a descending aeroplane is, regardless of speed, creating less lift than when it is level and so it would have less wake anyway.
A sideslip, and definitely not something you’d do in anything other than an honest life or death emergency in a big aeroplane. In a little one, particularly biplanes with no flaps and limited forward visibility it is often standard for the approach and landing.
For all normal operations in a big aeroplane, if you can’t get the descent angle you need using gear, flaps, and airbrake/spoilers, then you need to go around and have another go at it.
That swirling, tumbling air doesn’t continue to swirl an tumble forever and ever. Viscous dissipation means that 100% of this motion eventually gets converted to heat. If you believe that this doesn’t happen, then you need to explain where this energy ultimately ends up.
Thanks for all the other comments - however I take exception to this one. A plane is always creating just as much lift as it weighs, except in the brief transition from level to descent. When it’s on a steady descent it’s still creating just as much lift as it weighs. It will weigh less on descent than takeoff because it’s carrying less fuel.
It’s my understanding that the wake turbulence (especially wingtip vortexes) are mostly dependent on the angle of attack, so are greater at slow speeds.
I was in one commercial flight where we made one go-around, then the controller stuck us back on approach ahead of another plane back in the distance, but we were too high for a normal approach. The pilot did S-turns on approach to lose the altitude. Like you said, he did not side-slip.