PearlPilot

I still don't get it, about the definitions. Side slip is also known as the "down-wing method" while the forward slip is known as the "crab" method. On a crab you are "sideways" so shouldn't the crab be named as a side slip, because your longitudinal axis is parallel in the down-wing method, so name it as "forward slip."?

unemployedagain

sideslip uses opposite aileron and rudder while forward is the difference of the wing correction angle as compared to track, no inputs just correcting for wind with a heading change to course.

rickair7777

Both are aerodynamically the same thing, which is a slip. The difference is in what they are used for and the order in which you make the control inputs...

In a forward slip, your puropse is to hang as much fuselage in the breeze as possible to create drag and bleed energy. You start by apply full rudder and then add enough opposite aileron to keep your desired track.

With a sideslip, your purpose is to fly the airplane on (and aligned with) centerline in a crosswind. You first apply enough aileron to offset the crosswind, then you apply the required rudder to keep the fuselage aligned with centerline.

RomeoSierra

Remeber that you will touch down one wheel at a time when landing using the sideslip in a crosswind landing. Try doing soft field landings in a crosswind to master the slideslip.

Ewfflyer

Better yet, only do 1-wheel touch and goes(assuming you fly a cessna). I've done it a few times in a piper, but definately much harder to do with the wider and longer wheelbase. Usually a good 10-15kt steady wind works well

ryan1234

Call me crazy, but I just think that doing one wheel touch and goes puts a lot of bad pressure on that one landing gear, especially if it's just the slightest bit gusty.

I could just never really understand all of the logic in not side loading the gear (when every take-off in a single does), yet landing on one gear. I've seen many students and ever other pilots drop it in on one gear trying to keep it corrected for x-wind (maybe a fixed gear might take it - but what about when you transition to a retract?)

UAL T38 Phlyer

Touching-down on a single-gear (and then lowering the other wheel) is not an undue-stress on the gear, whether it is fixed, retract, a 172, or an airliner. (Trying to do a single-wheel touch-and-go is probably beyond a beginner's capability)

Depends on the airframe, but in some airplanes (A-320, as I recall) you did wing-low during a max-crosswind landing. 747, more crab---the problem there was not dragging an outboard engine if the wing was too "down."

The issue is the direction of the touchdown loads. Gear, especially most retracts with oleo stuts, can take significant vertical impacts. And they can obviously take big aft-loads....that's what the brakes do. But sideways loads put the strain on the mechanism that makes it retract or stay in the locked position--generally, the weakest part of the gear. In fighters, the issue is often the tires...side-loads can peel the tire off the rim when heavy-weight.

As to your comment that sideloads exist on takeoff: not really, unless you are weaving. If you are tracking straight down the runway, don't confuse aerodynamic sideload on the fuselage (which is relatively small) with inertia sideload that you get at the moment of touchdown, if crabbing. That load can be huge.

Personally, I like wing-low and minimal side-loads where the airplane Manual allows it.

NoyGonnaDoIt

One thing (among others ) to clarify: A "crab" is not a slip and has nothing to do with a slip. A crab is =coordinated= straight and level flight.

Don't worry about the names of the two slips. I've heard people try to explain why they are called what they are and you can go nuts trying to figure it out.

rickair pretty much nailed the explanation: a slip is a slip - aerodynamically, they are all the same. What the slip is called is related to what the slip is being used for, with a "forward" slip used to lose altitude and a "side" slip used for landing in a crosswind.

NoyGonnaDoIt

You mean that you think sliding sideways across the runway on two wheels puts less pressure on the gear than moving straight ahead on one?

UAL T38 Phlyer

Excellent point above, and agreed with the rest that followed. Don't worry about the semantics of what to call it. "A rose by any other name..."