First, one has to distinguish between uncoordinated turn vs uncoordinated straight flying, the physics of stalls and spins are not the same 
Second, you are not turning while in slip on final tracking runway heading, third, how the heck you plan to land or taxi in gusty cross winds 100% crabbing? or land if flaps fails?
There could be some caveats on fuel asymmetry (heard Robins suffer from this, it’s also documented in Moooneys) or enveloppe protection (not sure what happens when you sideslip Cirrus or A320 as far as their ASI/AoA start to show erratic values)
If the engine fails and you have to bring it in tight farm fields, one will be glad to bring it steep on max flaps + sideslip, not sure how much the sideslip helped but the aircraft was unscratched and I can still write comments in EuroGA
I find slips on final an extremely handy thing and do use them fairly frequently.
I was certainly taught then in my ppl (in the UK) but had heard about the french aversion to them.
My instructor told me that slips is easy and not problematic on high wing planes such as cessna and cubs, because extrados will not to be masked by airflow. and then stall. On low wing, it is will be masked and have more tendency to stall.
But I’ve been advised to have a bit of speed and preferably no flaps.
It basically differs from instructors and relation between you and him.
The second technic is of course a lighter slips with roughly 30 R and L turns to dissipate more energy. On the cub, you gain about 1000fpm.
Slips are one of my favourite manouvres and Ive done them in every type I’ve flown (with one exception but that waas because it was a 2 million quid aeroplane….)
greg_mp wrote:
My instructor told me that slips is easy and not problematic on high wing planes such as cessna and cubs, because extrados will not to be masked by airflow. and then stall. On low wing, it is will be masked and have more tendency to stall.
Well, the POH for the Cessna 172 cautions about side slips with flaps extended as that can lead to some instability in pitch. (Slips with flaps extended is not prohibited as the pitch instability can be managed by the pilot, but it should not come as a surprise.)
johnh wrote:
No problem, I asked him if it was OK to slip (“glissade”) and he said yes. So I entered it as I always have and was taught by numerous instructors: left aileron, right rudder, blended to enter the slip. He grabbed the controls and muttered all sorts of imprecations about spins and how dangerous it was.
Woha… some things must have massively changed in France. I did see some very interesting demonstrations of “glissades” by people who definitly learnt to fly in France on the SE210. Used it quite a lot with my Cessna as well, no FI ever told me not to. We also slipped the Senecas at the time. Never tried it with the Mooney but it should work as well.
After all the word “glissade” is French…
Maybe they have unlearned it in the transition to Airbus philosophy. Mind, I wonder if one can side slip an Airbus or if the protections get their underwear into a twist. Must try that at some stage if I get the chance.
I think maybe the point is as an instructor would you teach side slips, or “Ss” to lose height during your approach to landing or alternatively would you teach the stabilised approach and go round when not stable. This all being for PPL students, not those doing more advanced training eg aerobatics.
As I explained, some years ago and following studies of accidents during landung, (which I am still trying to find) the DGAC advised against side slip training at the PPL stage.
This has nothing to do with crosswind training and the crab technique which is taught at PPL level whenever the opportunity arises.
Remember in France the vast majority of airfields consist of one runway so you have 2 QFU,’s reciprocal one to the other and therefore crosswind landings are a common necessity.
Mind, I wonder if one can side slip an Airbus or if the protections get their underwear into a twist
My understanding you can just as much as you can fly it out of balance on single engine, you can sideslip an A320 above it’s Vmca as long as the sensor data is reliable and of course in crosswinds
At slow speeds it’s bad to sideslip, so enveloppe protection may kick in 
That doc is great, thanks !
Ohhh yea. Thanks @Ibra. Great doc.
