side-slip for x-wind

[navajo]

I have flew a king air with 2 guys who are doing a side-slip from ~300 feet until the ground to compensate for x-wind instead of doing it on the flair. I don't have any multi-engine book to confirm it but can someone give me references that say you cannot, or you shouldn't do that with a King Air, or any multi-engine?

[Rockie]

I don't know about a king air, but sideslip for a crosswind landing is an approved technique in every airplane I've ever flown (except an F-18) up to and including an A340. A quick glance at the B777 FCTM says it's approved for it too. Obviously within limits of course due to engine or wing strike risk. The initial approach is flown by crabbing into the wind then initiating the sideslip late in the approach. Starting it at 300 feet is excessive especially in a small airplane.

[Hedley]

Generally if someone starts sideslipping at that height,
they are doing it to lose energy, not for alignment at
touchdown.

[MichaelP]

I would imagine the sideslip method in an Airbus 340 is extremely risky.
And what about the 737 CFM56?

In China one of our DA40's had a wing strike the ground and I see one of our DA20's with similar damage.
With Diamonds the other method is prefered!

One of the incompetencies in the training business is the inability and ignorance of many instructors of the crab and kick it straight method.
Even in the Cessna I taught both methods and you'll be surprised at how many pilots chose the crab method over the wing down method.

If we only teach one method then we are not doing our job 100% only 50%.

A slip is always a slip. It is a drag manoeuvre to lose height.
Smart pilots glide in the crab and then decide which method they use for the final crosswind adjustment when the runway/field is made.

For wide track gear and wings with less ground clearance I prefer the crab. The wing down 'side' slip works well with Cessnas with narrower tracks and a lot of wing clearance.

When I was taught to fly in the Cessna 150 I learned crab as the prefered method and wing down slipping as an exercise.
The objective was to teach you to fly aeroplanes and not just the C150!
The crab works for all aeroplanes, the wing down side slip is risky for some.
Off an ILS to minimums are you really going to put the aeroplane into a slip? Or are you better off learning to kick it straight and retain the stabilised approach through the last 200 feet, 20 seconds or so?

[mcrit]

I just looked in the C90 POH and there is nothing that prohibits a sideslip, or a forward slip either. Now, doing it from 300' to touch down may not win you points for style, but it's allowable.

[Shiny Side Up]

Generally if someone starts sideslipping at that height,
they are doing it to lose energy, not for alignment at
touchdown.

One of the incompetencies in the training business is the inability and ignorance of many instructors of the crab and kick it straight method.
Even in the Cessna I taught both methods and you'll be surprised at how many pilots chose the crab method over the wing down method.

Personally I prefer side slipping, though to be honest few pilots do either method very well. Very, very few know about using a slip to bleed off energy as Hedley mentions above, most I find are over dependant on using the flaps for what they percieve is this purpose.

I would note too that the crab and kick method is not without its risks as well. It requires fairly precise timing at the very last moment, and still requires a good ability and understanding of slipping the aircraft to accomplish well - which is where many pilots fail at the activity as they believe that the method means that they don't have be able to slip well to accomplish it. This often leads to some tire screeching side loaded landings, which many will accept until the poor airplane finally gives in and peels the rubber off and takes a trip to the weeds. Hedley often points out how tolerant the humble Cessna is of these landings.

As a side note the only airplane I've flown that requires you to land it in a crab is the Ercoupe, but then you don't really have the option to slip anyways. The gear are also designed to handle it. As a side note I discovered that Ercoupes have done rocket assisted take offs the other day - how cool is that?

[MichaelP]

The crab method sounds worse than it is. The timing actually does not have to be that precise as if you kick it off too early it takes time for the aeroplane to accelerate to the crosswind speed.
Be too late and yes you can side load the gear, but at least this is both wheels (or all three in a proper aeroplane).

This often leads to some tire screeching side loaded landings

In many thousands of landings I've done with people using the crab kick it straight (with a little aileron to keep the wings level) method, I have yet to hear screeching tyres!
Sure you hear them screech when an airliner lands, but straight or not straight the screech is always there for such aircraft.
But in a little aeroplane? I've never heard them screech!

Like all things, teach it right the first time!

The won wing lo Chinese landing does put a side load on one wheel. People who think there is no side load when landing on one wheel need to draw a vector diagram!
All the landing loads are absorbed by one leg using this method.
But it is easy in the aeroplanes people know best here, the Cessna trainers.

[Hedley]

Very, very few know about using a slip to bleed off energy as Hedley mentions above

Surely you jest.

How on earth would they fly an aircraft without flaps?

I frequently use a 90 degree (knife edge) sideslip on
short final (legally). What's the big deal?

I'm not sure anyone here knows who Gene Soucy
is, but a favorite technique of his, is to snaproll on
final to lose energy.

[Rockie]

I would imagine the sideslip method in an Airbus 340 is extremely risky.

It's one of the recommended techniques and isn't risky at all provided you remain within the limits of the airplane. This chart is from the 330, but the 340 isn't dramatically different. You can see that at a typical touchdown attitude of 5-7 degrees, the wingtip contacts the ground at around 20 degrees of roll with the bogie tilted and the oleo extended. That reduces to around 17 degrees with the bogie level and oleos compressed. The engine doesn't hit until the pitch reduces to around 3 degrees and at a bank angle of 18 degrees.

[Shiny Side Up]

Surely you jest.

How on earth would they fly an aircraft without flaps?

I wished that I jested Hedley, though rremember the type of pilots I most encounter, those exersising their PPL privelidges. Who knows how they would land an airplane without flaps? The point is moot because none of them usually ever will. When I do insurance checks rides with renter pilots, without fail their weakest point is slipping.

The won wing lo Chinese landing does put a side load on one wheel. People who think there is no side load when landing on one wheel need to draw a vector diagram!

Not debating that it doesn't, just saying that both methods of landing the aircraft are valid, as you would proponent the crab-kick method, I would proponent the sideslip method, and hold that both are good ways to do it. Both have the potential if done wrong to put undue stress on the gear. For example the one time I saw a poor 172 peel off two of its three tires, the pilot described to me how he was fully intending on using the crab-kick method you described to land in the crosswind. He timed it... poorly. My runway also has plenty of evidence of similarly poorly timed crab-kicks - though obviously not to as drastic of result.

That being said I've seen airplanes rolled into balls as plenty of evidence that the pilot didn't know how to do a slip landing either.

But it is easy in the aeroplanes people know best here, the Cessna trainers.

Its also fairly easy to accomplish in your favoured Diamond trainers, Pipers, Grummans and Beeches (though the Musketeer with its trailing spring gear is a bit easier to do a crab-kick in).

[Hedley]

I personally don't allow an aircraft to touch down until
it's aligned with the direction of travel, but perhaps I am
a bit old-fashioned.

I might very well be tarred and feathered for mentioning
this, but ...

Ever landed with a crosswind on an icy runway? No big deal,
we've all landed on frozen lakes at one point or another. You
can line up the axis of the aircraft with the direction of travel,
but you don't really need to bother, because it's going to
weathervane into the crosswind on rollout anyways.

During the winter, with a crosswind on a runway which is
50% bare and dry and 50% polished ice, during the rollout
the aircraft will alternately weathervane on the ice, then
straighten out on the pavement again.

Which got me thinking ... (I know, bad idea) ...

What happens if you simply land a light nosewheel
trainer crabbed, with a crosswind? Initially, because
of the lift generated, there isn't that much weight on
the tires, but there is enough friction to straighten
the aircraft out, generally with a bit of honking and
whining from both the tires and the instructor in the
right seat.

The center of mass is ahead of the main gear, after
all. If it wasn't, it would be on it's tail on the ramp.

And, the center of mass after touchdown nicely
pulls the aircraft straight, in the direction of travel.

Now, I'm not saying it's pretty. Or even a good
idea. It's surely lacking in style. But maybe it's
better than wrecking the aircraft.

You decide.

[MichaelP]

The way I look at it is I crab (a bit of a misnoma since the ball's in the middle), a far as I know I can comfortably kick it straight and then I slip as necessary.
Usually as you get into the flare some of the crosswind has reduced leaving the necessity for only one or the other of these techniques.

In the forced approach situation the crab is the better glide!

There is a PANIC factor to all of this and many of the things we teach, and this is developed from instructors who are less than competent and from heresay.
If you instill a fear in a pupil for something that fear stays with them for life, including their future lives as instructors themselves.

Here I instill the fear of the scraped wingtip in the Diamonds. It's too easy. I have photo evidence to back this up!

I read the stuff above about the A330 and it's all well and good but those wings flex with the downloads on landing and so you need to consider the vertical decelleration and it's effect on depressing those pods!
The A340 has two spare hair dryers out there right?

I am not a proponent of one method, but I am a proponent of teaching both for like many things we do, the more tools we have the better we are able to cope with particular situations and different aircraft.

[Shiny Side Up]

Now, I'm not saying it's pretty. Or even a good
idea. It's surely lacking in style. But maybe it's
better than wrecking the aircraft.

To be honest Hedley, I'm not sure what you're getting at here. Yes you could do this, but there are better methods of doing so. It also depends on your view of what "wrecking the aircraft" is. Two destroyed tires, a bent firewall and a wrecked oleo certainly in my books was more than "just lacking in style".

And yes you can get away with more lapses in ability on slippery runways, grass runways and hell, even gravel runways. There is a reason they used to be airfields, rather than runways, because in the budding days of flying bringing the airplane down somewhere in a mile by mile square (just avoid the windsock in the middle) was all one could hope for. I hope in a hundred years we've come a little farther than that.

[Hedley]

I'm not sure what you're getting at here

Simply realism. Tailwheel aircraft, biplanes, radial engines
and the pilots that can fly them, all belong in museums.

Stick and rudder skill is unnecessary, and frankly passe.

The question remains, how low is the common denominator
when it comes to landing a nosewheel aircraft?

Try the touchdown-in-a-crab method, in a light nosewheel
trainer on dry pavement, and get back to me. It surely
will not result in blown tires, busted oleo, wrinkled firewall, etc.

I have had it demonstrated to me many times by student
pilots, and all it results in is perhaps slightly higher than
normal tire wear (shrug).

[iflyforpie]

It is good to learn as many ways to land in a crosswind as we can so we are able to adapt and improvise to each new situation or aircraft (closed loop) instead of simply learning by wrote and not knowing why we do things the way we do (open loop).

That being said, I prefer the crab and kick method, with a little roll into the wind, for landing most aircraft. Surface winds are always less than the ones at 100 feet, and the natural and coordinated control inputs during a crab help you keep a stabilized approach.

Sure there is timing involved to make it pretty, but is the flare any different? Continuously slipping is fun for horsing around, but uncomfortable for passengers.

[mcrit]

I've always found for a light trainier and a beginning pilot a combination of crab and slip works. Hold a crab all the way down final. When it comes time to start the flare use the rudder to kick the a/c straight with the direction of travel and the ailerons to control lateral movement. Heavier a/c and higher time pilot you can start to just kick straight in the flare.

[Shiny Side Up]

The question remains, how low is the common denominator
when it comes to landing a nosewheel aircraft?

Try the touchdown-in-a-crab method, in a light nosewheel
trainer on dry pavement, and get back to me. It surely
will not result in blown tires, busted oleo, wrinkled firewall, etc.

Oh, we're here again. I ain't going to argue with the idea that training on a tailwheel aircraft is viewed as superior, lord knows that dead horse has been beaten around here. I also won't argue that yes, indeed you can get away with landing a nose dragger in this fashion. In fact you can get away with it quite a bit before the day it decides to bite you. Just like you can get away with a lot of things before they do. But then I don't need to tell you this.

Is it really too shocking that there's people out there that are pushing to do it right rather than just good enough? The job is hard enough than to have experienced pilots like yourself advocating to do otherwise.

[Rockie]

I read the stuff above about the A330 and it's all well and good but those wings flex with the downloads on landing and so you need to consider the vertical decelleration and it's effect on depressing those pods!
The A340 has two spare hair dryers out there right?

It's not a problem. 10 degrees of bank when sideslipping for a crosswind landing is a lot, but it's still well below strike territory. Some manufacturers recommend using the crab and kick straight at the last second method above a certain crosswind component though. I don't like it personally because it can destabilize what was a good approach up to that point. In a really long airplane you can move the cockpit sideways around 20 feet suddenly using that method which can be a bit uncomfortable, and it has some inertia behind it unlike a cessna so I prefer doing things more slowly and a little farther back.

[sakism]

1 - Crab until short final.
2 - Apply powers so more power is on upwind engine to align aircraft with runway, and at the same time
3 - Add aileron into wind to prevent drift.
4 - Land.

[Rockie]

1 - Crab until short final.
2 - Apply powers so more power is on upwind engine to align aircraft with runway, and at the same time
3 - Add aileron into wind to prevent drift.
4 - Land.

That's an odd way to do it. Doesn't your airplane have a rudder?

[navajo]

That being said, I prefer the crab and kick method, with a little roll into the wind, for landing most aircraft. Surface winds are always less than the ones at 100 feet, and the natural and coordinated control inputs during a crab help you keep a stabilized approach.

Sure there is timing involved to make it pretty, but is the flare any different? Continuously slipping is fun for horsing around, but uncomfortable for passengers.

That's exactly what I think. I think the sideslip technique is just too uncomfortable for passengers, and like you said, the winds are never the same at 100 feet than on the ground, especially at night! And I just don't trust the airplane on a sideslip in a gusty and turbulent environment, maybe it's just an impression...

And correct me if I'm wrong, but ultimately, when you will touch the ground using the "crab until the end, bringing the nose centered with the runway and lower the wing", you will be in the same configuration than if you were doing that sideslip from 300 feet, therefore I don't understand why some people are saying it's more risky to touch the ground not aligned with the runway, when you have to correct the sideslip all the way down anyway.

[iflyforpie]

1 - Crab until short final.
2 - Apply powers so more power is on upwind engine to align aircraft with runway, and at the same time
3 - Add aileron into wind to prevent drift.
4 - Land.

Might be great for a steady cross-wind; but you will have to be a throttle monkey if there is any adjustment to do. Most engines won't respond fast enough anyways.

I suppose you could use it to reduce your rudder inputs and make small adjustments with rudder, but what happens when you reduce power to land? Better be johnny-on-the-spot with the rudder. If you have to use the rudder at some point anyways, why not use it all the time?

[Big Pistons Forever]

If the pilot has the handling skills to properly fly the wing down method than I would suggest they could also effectively execute the crab and kick it straight method..and vice versa. Therefore what method you choose becomes a personal preference. Personally I use the wing down mehod on everything from a 7AC champ to the DC6. From an instructor view point I intial teach only the wing down method because I have found students find it easier and it builds on the initial landing fundamentals of using the flight controls to keep the aircraft aligned with the runway heading and centred in the middle of the runway. For advanced PPL and CPL training I teach a blended method of crab to about 100 ft AGL with a smooth transition to a wing down with the aircraft pointed straight down the runway. The bigger issue IMO is to ensure that the students gets any kind of practical experience. Once the student gets good at into wind landings I try to use a crosswind runway whenever the opportunity presents itself. This does not seem to be the practice at many FTU's and some have IMO ridiculously low allowable X-Wind school limits. For CPL students I want to see him/her land at or near the demonstrated x-wind wind speed for the aircraft type.

[MichaelP]

The maximum demonstrated crosswind was for a pilot of average ability...
That was 35 years ago.
The practice of some schools these days is to treat their students as idiots with a less than average ability.
For many people they will try to be what they are expected to be. Treat them as stupid from the start and they might behave stupid.
Treat them as intelligent people and they will progress in a better way.
Of course there are some stupid people, but let's not treat everyone this way.

[LousyFisherman]

If the pilot has the handling skills to properly fly the wing down method than I would suggest they could also effectively execute the crab and kick it straight method..and vice versa.

I use the side slip because with my (lack of) skill I have troubles co-ordinating the transition from the crab to the slip just before the flare. I would much rather do the transition long (300-500 feet) before the flare, then I can concentrate on flaring and losing energy properly. In low crosswind situations I practise the crab and kick but I am still very amusing to others at those times.

Very, very few know about using a slip to bleed off energy as Hedley mentions above

Surely you jest.
How on earth would they fly an aircraft without flaps?

This is because of how slips are taught. For example, at my ex-school forward slips were only taught above 2000 feet AGL, to use them below that was discouraged, to use them on final was a no-no. One of the common student discussions was what are forward slips used for as no practical use was ever demonstrated. And when you do use them, you get criticized.

On forced approaches I try to stay very high relative to my desired field, then from about a 1000 feet away I forward slip until it appears I will drill into the ground at the front edge of the field, exit from the slip, flaps down, and ease in. 99% of the time i have the correct airspeed but I am still 50-100 feet too high. With my skill level I figure that is pretty good, The school and just about all the instructors were appalled at this and would only recommend me for my test when I demonstrated multiple times that I could do forced approaches without the slip. Of course it is not a true forced approach so whenever a student is low they "warm the engine". Top quality training that!

So in an energy short environment I, and others, are being taught to waste energy early. Doesn't make sense to me ????

On the other hand, my tester was quite happy with my forced approach and once I was in the slip and he saw the trajectory called that part of the test over and gave me a 4. I think we were still above 500 feet AGL.

Flaps, I only use them on my 150 for short field stuff, they usually get more use during the walkaround then they do in the air.

Knife edge slips, they didn't teach me that, details please Hedley.

Edited for MichaelP
Approach speed is 55-60KIAS without flaps in my POH, so thats what I do them at