Wing down during final approach.

[tecman]

Chuck, I've been enjoying reading the thread, which I picked up on only recently. One perspective I didn't see mentioned was that of someone flying some of the new-generation VLA or LSA aircraft. I fly one of these quite a lot, as well as the usual GA stuff. It's a classic lightweight (<600 kg) low-wing, low wing loading, low stall speed design, with good demonstrated cross-wind capability (22 kt). I also fly in a windy locality, with strong gusting winds being the norm for much of the year.

The first thing in this scenario is that care is going to be needed regardless of the landing technique you choose: a little aeroplane, needing slow approach speeds in strong gusting winds means you're going to be busy. I'm happy to fly either wing-down or crabbed approaches but I find that in the worst conditions, with the x/w at maximum demonstrated or beyond, a crabbed approach works best. The crab angle is essentially instantly adjustable and I find the aircraft is particularly easy to land using a late transition to wing down and rudder as required to keep straight. That aside, with the gusts being a fair component of the stall speed, and disdaining excess approach speed, I feel safer flying final with no crossed controls (even though I know the safety margins are high in the approach and landing configuration).

Having said all that, I love flying the classic flapless taildraggers with a wing-down approach, probably just because I can. Also, being a lazy type it just seems as though when you're using some slip to adjust the approach anyway, why not use it for drift offset? Just a preference and not meant to be consistent with the LSA situation.

Finally, I only saw one other reference to a crab on final with a bit of wing down. I've flown with quite a few bush pilots who do this but I've also observed that quite a few others do it instinctively, which I think is no bad thing.

[3 Point]

Hi tecman,

An excellent post; I absolutely agree with your comments. Different techniques employed for different situations as appropriate. Not a "one size fits all" mentality!

Happy landings

3 Point

[Pace]

3 point

I agree too! you should use whatever method suits you and the aircraft but you should do that because it is a choice not because you are frightened of or feel incapable of dealing with other methods.
In that case you would be better going up with an instructor on a windy day and hammering out the approaches until you are comfortable handling the aircraft near the ground in all conditions and methods.

Only then choose which method you like best!

Pace

[phiggsbroadband]

Hi Tecman... you quote..
'with the x/w at maximum demonstrated or beyond, a crabbed approach works best. The crab angle is essentially instantly adjustable'


Whilst you probably do this instinctively, I would still like to ask...How do you instantly adjust the crab angle.. With aileron? or with rudder? Or perhaps you haven't really thought about it too deeply, and just got on with it.


I am still sitting on the fence here, and will continue to fly finals with a partial rudder input. It doesn't look as alarming as a full crab or a full side-slip. (and in a C172 you should not side-slip with flaps down.)

[Pace]

Phiggbroadband

With this discussion you would think the crab is unique to an approach to landing?
Unless you are flying on a windless day you are crabbing all the time to maintain a track from A to B usually at altitude in far stronger winds than you get on the approach.

Ok for most the autopilot does that for you on those long legs you have it in nav mode so the poor autopilot and FD does the job for you but think about it
All you would do in a crab to land is what you would do for the earlier flight maintaining a track.

You would certainly not fly crossed controls leg A to B so that your heading and track are then the same regardless of a 50 kt X wind from the right at altitude!!! All the while accepting the extra drag that configuration would incur and the lower airspeed! Why change that down the approach ?

The only issue occurs when you need to change from the crab to align with the runway to land so the aircraft does not touch down sideways but really you are talking the last 10 feet that last 10 feet may require crossed controls then again if you get it right it won't.

the poor old autopilot will even do that for you down the ILS until you disconnect at maybe 200 feet.

it all smacks at an inability to deal with those last 10 feet!
I could equally ask you how do you fly on a 70 mile leg from A to B with a changing crosswind from the right while trying to maintain a track? Cross controls?

Pace

[tecman]

Phiggs,

I do it as coordinated turns but don't forget they are very small turns. Typically, you're correcting with small heading deviations about a mean offset, so talking about a coordinated turn might be a bit academic - but that's what I'm aiming for.

Incidentally, the 'crab + last minute wing down and straight with rudder' is referred to in Australia as the 'combination' method but I don't know if that's the terminology used elsewhere.

As i mentioned I'm in no way alarmed by the wing down method but just wanted to give a vote to the crab at the VLA/LSA end of the scale. I might say that while I've never found the timescales to make the requisite small crab adjustments an issue in any aircraft, the bug smasher is a delightfully responsive aircraft and demands/rewards good technique. Probably not a great IFR platform, of course.

[Desert185]

For those of you who aspire to only fly light aircraft VFR/VMC and like the slip all the way down final, regardless of turbulence or high density altitude, and if slipping works for you, don't change a thing.

For those of you who aspire to fly something larger or more sophisticated while IFR/IMC with an autopilot, you had better learn how to fly final in a crab and make the landing transition to a slip.

That's about as simple as I can put it.

[dash6]

Surely,if using the crab method,you end up transitioning to wing down in the flare you've mis-timed it? As you (smoothly) apply rudder to align with the runway,aileron is used as required to maintain wings level? Parking...front in. Easier to load from the trolley.

[FullWings]

I use both techniques, depending on what I'm flying and the conditions.

Landing gliders with their long spans close to the ground I crab until the last second then gently align the fuselage with the direction of landing whilst keeping the wings level. On the 777-2/300, by about 150-200' above the TDZ I'll have transitioned from crabbing to aligned with the runway in a stable sideslip. If the cross component exceeds about 25kts, I'll take c.25kts worth with wing down and get rid of the rest with a de-crab in the flare. In the Cub, there is nothing more joyous than landing on one main wheel 1/2kt above the stall and rolling out in a straight line with the wing gently coming back up - shame that it doesn't happen that way very often!

The benefits from a wing-down approach in a large/long aircraft, assuming that the airframe geometry will let you, are: a) tracking down the centreline and not having to guess how far upwind you need to place yourself to be aligned when de-crabbing and b) if you misjudge the flare and float a bit or are caught by a gust, you have time to sort it out, rather than being drifted downwind off the centreline. Having a bit of extra drag helps to keep the engines in the rapid response range, especially with a tail component.

In crosswinds, unless you just put the aircraft down on the runway with no adjustment whatsoever apart from flaring (and there are conditions where that is the right thing to do), you are using a variant of the wing down method. It might be better named the "very late wing down technique". It may not be a balanced/stable slip but a slip it is: witness the crossed controls.

[Chuck Ellsworth]

We should start a new thread on how to land as this has morphed into a how to land thread.

I started this thread to ask why so many pilots side slip all the way down the final approach.

[FullWings]

Chuck,

Your OP:

There are a lot of pilots who use the wing down sideslip method to keep their airplane tracking the runway center line on the final approach to landing.

Which is probably correct, given circumstances and aircraft limitations.

Do they fly their cross country tracks using the wing down side slip method to maintain the desired track?

I suspect not.

I started this thread to ask why so many pilots side slip all the way down the final approach.

Not so sure about that. Never seen it myself unless they're too high, the final approach is extremely short or they are "top ruddering" round onto final where it's natural to continue with a slip?

We should start a new thread on how to land as this has morphed into a how to land thread.

Don't hold back...

[foxmoth]

I started this thread to ask why so many pilots side slip all the way down the final approach.

Well, reading through the thread I would say that actually not that many DO side slip all the way down, it would seem to me that most crab to 300' or less and then either kick straight for landing (what I would describe as a FULL crab technique landing), or transition at some point to wing down, many actually doing so as they kick straight in the flare.
There are some on the thread that seem to say crab is the ONLY technique that is right and IMHO these are as wrong as those that say that wing down is the only technique, I have been flying 40 years now and never had a problem with crosswinds, personally I prefer wing down because from the time you set the aircraft up like that you point the nose straight down the runway and it stays there until you are at a speed to turn off. I CAN fly crab, and indeed teach it because I like my students to know how to do BOTH methods, I also fly LARGE (360 seat) aircraft, but still prefer wing down ON LANDING. I can accept though that others prefer crab and you should stick to what suits you and the aircraft you are flying.

[Pace]

Fox MOTH

I must admit to alway using the crab and cannot genuinely remember a bad or overly heavy landing in the past 15 years.( genuine )
Nevertheless I will try your technique when I get the jet out of maintenance ! If I mess up and blot a 15 year personal record I am going to blame you

Pace

[Chuck Ellsworth]

, it would seem to me that most crab to 300' or less

Not meaning to be pedantic but I am trying to remember if I was ever stabilized on an instrument approach in IMC and at three hundred feet destabilized from balanced flight controls to a sideslip in preparation for landing on a runway I still can't see.

[Smokey Lomcevak]

The ways I see it, in a x-wind condition, a landing will require a side-slip into wind if one is to avoid side-loading the landing gear. It therefore becomes simply a choice regarding when one introduces this slip angle - during the final approach ("wing down method") or during the flare ("crab method"). I would therefore suggest that a crabbed approach with a flare that aligns the aircraft with the runway, with opposite aileron to maintain wings level is only a partial solution. Any X-wind condition will then blow the aircraft downwind, creating side-load at touch down. Lowering the into wind wing, and side slipping against the relative airflow would be the only way to maintain the aircraft trajectory parallel to the runway axis. So we find ourselves in a condition that is essentially the same as our "wing down" approach.

In the real world, of course, the more mass an aircraft possesses, the less it will be influenced by that momentary crosswind during the flare. Thus less upwind wing down will be required, so long as a touchdown follows promptly. In a lighter aircraft it becomes more of an issue because the xwong component at flare time will have more of an effect.

I appreciate that I'm looking at this rather academically, and absolutely eliminating gear side loading may not be necessarym- it is simply a case of controlling it within readable levels.

The 737 has been mentioned about its ability to withstand side loaded landings with a crab angle still present. I seem to remember being told that this was as a result of its inability to lower the upwind wing sufficiently without banging the new high-bypass engines fitted to the 300 onwards whilst still maintaining the rather squat landing gear.

I suppose my point is that, whilst this topic seems to come up with some regularity, the two approaches are not that dissimilar, and ought to result in the same outcome - a landing in the slipped condition. I would also suggest that the phrase 'maintaining into wind aileron to stay wings level' is not enough. Academically speaking, it would still result in a side loaded landing, and the object of de-crabbing in the first place was to avoid that.

2 cents etc..

[foxmoth]

Pace,
if you read my post you will see that I am NOT advocating wing down for you,as you say, you would probably screw it up and bend your aircraft! I am merely stating what most people seem to do reading the thread, what I prefer, and that you should not be so pedantic that crab is the only way!

Chuck,
Also not reading I think, I did not say that I would transition AT 300', just that most do that somewhere between 300' and roundout. Personally, including in a large aircraft, I would hold the crab until roundout, then straighten, lowering the into wind wing at the same time, the amount of wing down being dependant on wind and aircraft type, even with crab you destabilise at this point with the kick straight. Most Tailwheel vintage aircraft it would be a slipping approach anyway to see better (the forward/side slip bit I think is a North American thing, do not really get that distinction here in UK). Teaching is where I would be getting the student to set up wing down at around 300' - and actually is an argument for your original post of doing it from a long way out - you would then be flying a STABLE wing down approach all the way down, but as has been said, not comfortable and really unnecessary, in a light aircraft 300' gives plenty of time for a student to set it up and be stable for landing - and of course you do not then de stabilise in the flare with large rudder inputs!

[Prop swinger]

dash6, Smokey,

You don't need to transition to wing down to stop any sideways drift. If you hold the crab throughout the round out & hold off the aircraft will continue to track down the runway. As the nose rises to the landing attitude you feed in rudder to align the fuselage with the runway.

Applying rudder will not change the direction of travel of the aircraft, certainly not in the couple of seconds it takes for the aircraft to run out of energy & touch down. Crosswind or not, the aircraft will continue to track down the runway after you put in the rudder. The only thing you need to do with the ailerons is keep the wings level.

[BBK]

There seem to be broad groups contributing to this thread. There's the "I may use crab and/or wing down. What ever works on the day, is recommended by the manufacturer, whatever is mandated by SOPs. In short a flexible approach that gets the job done etc etc!".

versus

"Crabbing is the only way.....".

Fly safe y'all.

BBK

[Pace]

Foxmoth

I never said crab was the only way! I said the wing down/crossed controls is used by a small percentage of pilots while the vast majority use the Crab.
(proof of the pudding?)
I also expressed a concern that SOME may use the crossed control method because they are insecure handling winds and transitioning from crab to landing straight. I stated that if you are confortable with all manner of landings and happen to choose the crossed controls then Fine.

I dont know what your PAX are like but mine do not like wings going up or down But can get a nice look at the runway through the sidewindows in the crab

Pace

[foxmoth]

I never said crab was the only way! I said the wing down/crossed controls is used by a small percentage of pilots while the vast majority use the Crab.
(proof of the pudding?)
I also expressed a concern that SOME may use the crossed control method because they are insecure handling winds and transitioning from crab to landing straight. I stated that if you are confortable with all manner of landings and happen to choose the crossed controls then Fine.

OK Pace, well it has certainly felt at times that you were advocating crab as the only way, happy to hear otherwise! Whilst you may be correct in that a majority use crab, I would say that this is because of the trend to tricycle gear and the fact that many instructors ONLY teach crab having learnt on Pa28/38 and getting worried about touching the wing (not really a problem unless you take it to extremes) - I could of course be totally wrong!
Again if you read my posts you will see that I DO often use crab on the approach - but transition to a wing down in the flare, so my pax also get a nice sideways view!