Forward Slip in a Crosswind Landing?

5 Answers

1. 
   

   
   

   Kris Kortokrax on Jul 27, 2012

   Stop and think a minute. When you touch down, you will want a wing lowered into the wind. If in your scenario, you lowered the left wing with a right crosswind, at some point you will need to reverse and lower the right wing.

   If you lower the downwind wing, you will also be drifting away from your intended flight path.

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2. 
   

   
   

   Joe on Jul 28, 2012

   Well it seems as though essentially it shouldn’t matter which way the manuever is performed. If it is done in calm winds the pilot is not expecting a change in his ground track (not counter balancing the force of the winds). During a side slip and crab the aircraft is using the force of the wind to maintain the same track across the ground as it approaches the runway.
   There are two scenarios:
   1) The pilot is crabbing into the wind as he approaches the runway (most likely scenario). He already has his nose pointed into the wind and thus a transition into a forward slip would seem to be to just lower the left wing and apply right rudder. This would be the “smoothest” transition in my opinion.
   2) The pilot is already in a side slip approaching the runway. In this scenario it would make sense that the low wing is already low and it would require just the right inputs of rudder and maintaing the original wing low attitude.
   In either case a forward slip is intended to produce a straight ground track and will therefore be blown by the wind. I suppose the best position of the aircraft would be to have the wing already lowered on the side from which the wind is blowing so that the transition to a side slip (since we’re close to the ground) would be a bit more effortless.
   In either case I was wondering if there is any element of safety to consider. Since on taxi, takeoffs, and essentially landings we want the wing low on the windward side as to not get blown off the runway I suppose this would be idea.

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3. 
   

   
   

   Bob Watson on Jul 30, 2012

   I know that on a calm day, I would typically do a forward slip with right rudder and left aileron so as to put the runway into better view from the pilot’s seat (I fly side-by-side aircraft).
    
   If there’s a crosswind, I try to set the side slip up about 1/2 mile from touchdown because that’s where I start slowing down. If I can’t use the slip to maintain runway alignment a 1/2 mile out, then it’ll be even harder near the runway when I slow down further (unless the wind drops at the surface). So that gives me a 1/2 mile warning that I might need to go around.
    
   If I’m high and want to slip some more to lose altitude under those conditions, I’ll just cross the controls a bit more than needed to maintain runway alignment. The down-side to that is I might already be putting everything I have in just to maintain runway alignment in which case I need to come up with another idea. The up-side, of course is that it’s a pretty gentle maneuver to ease the pressure of the controls and reduce the forward slip to get back ito the regular, crosswind-correction for landing.
    
   Going the opposite way as I think was described by the original poster, would mean lots of cross-controled maneuvering close to the ground, which would seem a bit less safe and certainly more disruptive to any passengers who might be on board. I suppose you could still make it work, but why, when there’s a smoother and easier way?

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4. 
   

   
   

   Nathan Parker on Jul 30, 2012

   “Or in other words, should the nose be pointed into or away from the direction from which the wind is coming from?”
   The more important question is where do you want the relative wind coming from.  The direction of the relative wind tells you which way the airplane is moving in relation to the body of air in which it’s flying.  When you have a crosswind, the airplane always needs to move towards the direction where the wind is coming from, regardless of where the nose is pointing.
    
   In your scenario, there are three tactics to keep the relative wind coming from the east, which is needed to counteract the crosswind:
    
   1)  You can point the nose into the wind with neutral rudder (crabbing), or
   2)  You can have the aircraft pointed roughly towards the runway and slip to the right, or
   3)  You can have the airplane pointed roughly away from the runway and slip to the left.
    
   Only tactics 2 and 3 provide you with the increased descent rate you want, but only tactic 2 gets you to the runway.

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5. 
   

   
   

   Peter Black on Jan 01, 2018

   Hi. ‘My first post. I see this is an old thread, so I’ve no idea if this response will ever be read.

   I’ve thought a lot about forward slips to a x/w landing (to bleed off excess altitude), and the question: “Should the upwind or downwind wing “lead” the airplane toward the runway?” FAA literature seems to suggest “upwind”, i.e., a right bank forward slip if the x/w is from the right; but I’m not certain whether I agree:

   ROLL (not bank), in the absence of rudder-input induces a yaw OPPOSITE to the direction of roll, commonly called adverse yaw. “Adverse” suggests a “bad” yaw, but adverse yaw can be very beneficial.

   However, YAW in the absence of aileron input, causes PROverse roll, (a term not seen in dictionaries) that is, IN the direction of the yaw. So, if you think about it (and try it in the air), the forward slip can MUCH more easily be entered by rolling the airplane first — fairly briskly — without any rudder application until you’ve achieved the desired amount of bank; With a simultaneous rudder and aileron application, you are effectively asking the airplane to both roll right and roll left at the same time — with the left-rolling moment being caused by the left rudder. Simultaneous application of rudder and aileron makes for a “wallowing” entry into a slip. Roll first.

   By the way, if we END a forward slip by rolling out ONLY — and using NEUTRAL rudder, the adverse yaw on the rising wing will yaw that wing backward, until we stop rolling at the original 0-bank crab toward the threshold. In Joe’s question, above, any heading deviation (NOT TRACK DEVIATION) caused by the rudderless roll into the forward slip, will be undone by the rudderless roll-out from the forward slip…whether it is banked right or left. And I think this means that, whether we roll left or right into a forward slip, there will be no variation in the airplane’s track toward the runway, assuming we started with an appropriate degree of crab.

   Yet, with reference to Joe’s scenario above, logic says: If your right wing is down for altitude loss, you’ll need a smaller change of bank to convert to the side-slip needed for landing. Nonetheless, I find that I prefer my altitude-loss forward slips to be banked AWAY from the x/wind. The conversion to the side-slip seems smoother that way, even with the switch from a left bank to the right bank. But the FAA-AFH suggests I teach the other way. So I do. Go figure!

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