Crosswind Flaps
 

Hi all, been away from the forum for a while, actually flying!

I have searched for threads on this, which i thought would be a hot topic here but all i can find is biz jet techniques,.. a little outside of my price range!

I was flying a nice 172N on the weekend in slight crosswind that stiffened as i continued my familiarisation circuits (hadn't flown the 172 in a while).

Now i must be out of practice in crosswinds because i made a few what can be described as alarming landings. At first i thought it was the extra speed on the aproach so i slowed to 65 KIAS this helped some what but the touch downs were still very hard and my directional control was still hopeless.

I'm using the sideslip trick i was taught nose into wind kick straight at the flare, into wind wing down, that wheel to touch first.

I'm wondering if it was my use of 20-30 deg flap on the approach???
I tried a flapless as i do practice these every now and then and that approach was better and the roll out much more straight.

What i found i was having trouble was is the touchdown, it was always fairly 'positive' (the flare being nearly forgotten keeping the right wing down) and i had a real job keeping the aircraft on the center line, or infact vaguely in the middle... i got pretty close to the edge on one circuit and a dab of right brake brought the nose down alarmingly, so much so i was worried about a prop strike.

I was using RWY 16 wind was 20-30 deg off the nose and not more than 10-15 knts which to my mind is a xwind of 6ish knots.

Any advice is helpful especially on the use of partial or full approach flap.

Yes i have booked to go out next weekend with an instructor. i think i need it.

I was taught, assuming the runway length was sufficient, to not use full flap when there was a significant crosswind. This technique has worked well for me as the airports I use typically have long runways for the type I fly, so use half flap in these conditions.

The main thing to bear in mind is that the landing roll will be longer - and human factors being what they are you can end up focussing on the crosswind and how best to deal with it and overlook runway length / the fact that the aircraft will float longer if not using usual landing flaps.

Paul.

Flyingkiwi, there are arguments for and against using reduced flap, it can tend towards a holy war.. however: Given a crosswind component you quote at 6kts, you really shouldn't need to be considering less flap. I would suggest it's just a handling hiccup that will most easily be fixed with a little assistance from someone on board who can watch what you're doing.

For my part, I wouldn't recommend sorting out the cross control during the flare - I either get into the slip before the flare, or flare and use slip as required during the hold off. That might be a matter of terminology.

Kiwi,

The 172 was certified to wording like this:

Directional stability and control.

(a) There may be no uncontrollable ground or water looping tendency in 90 degree cross winds, up to a wind velocity of 0.2 VS0, at any speed at which the airplane may be expected to be operated on the ground or water.
(b) A landplane must be satisfactorily controllable, without exceptional piloting skill or alertness, in power-off landings at normal landing speed, without using brakes or engine power to maintain a straight path.
(c) The airplane must have adequate directional control during taxiing.

You'll notice first of all that there is no reference there to flap position. Therefore the technique required to achieve this requirement can be specified, and commonly manufacturers seem to suggest lesser flap settings for crosswinds, but with no numbers attached to the recommendation. However, unless the Flight Manual makes a reference to "avoid", "not approved", "prohibited", "maximum" etc. with respect to flap use, it's pretty well up to your preference.

I have previously posted here that my personal preference in every aircraft other than a Twin Otter, is full flaps for every landing, unless you've had a flap system failure. My personal preference may not be right for everyone, and that's fine. Though, if it were my plane, a pilot who could not demonstrate a full flap landing in the "demonstrated" crosswind value for the plane, would not be taking it solo.

When I flight test a plane with an external modification (often tail booms), I am specifically looking for a weathervaning affect that the mod might have on the crosswind capability. I will fly in the maximum appropriate crosswind I can manage, and always use the maximum recommended flap setting. I have never had a problem. I do agree that taildraggers are more challenging in this regard, and I do shy away from high crosswinds when flying taildraggers.

The most extreme tests I have done like this were in two different Cessna Grand Caravans, one in a direct crosswind of 19 gusting 25 knots, the other in 35 gusting to 40 knots, 45 degrees off the runway heading. Both mods introduced more tail aft of the C of G, so more weathervaning was likely. Though I did have to apply and hold full rudder a few times to keep straight, there was no problem maintaining control in either test.

Interestingly, the Caravan flight testing required me to also demonstrate zero flap landings (wind not a factor) last week. The touchdown speed was about 30 knots higher (full flare not possible, 'cause of mod), and a bit alarming, compared to full flap landings.

I encourage you to just keep practicing crosswind landings, and keep using the greatest flap settings you can feel comfortable with. You'll find that your confidence grows faster than you'd expect. You'll only get better if you push yourself a bit. Know that the aircraft can do it, when you apply the skill. A 172 will land nicely in at least 10 knot direct crosswind, with full flaps, quite happily.

Personally, and a bit like a "fraidy cat", I would simply rather be going more slowly should something bad happen, and the more flap I have out, the slower I'm going!

I think part of the problem with flight training is "one size fits all" pronouncements.

The characteristics of the aircraft have a large effect on the handling and so the amount of flap used should reflect both the aircraft and the conditions. Cessna's, particularly ones with 40 deg of flap, and loaded towards the front of the CG envelope tend to want to adopt a flat attitude in flare until they get quite slow and need a lot of up elevator to get a satisfactory nose high touchdown. If the wind is gusty they trying to transition into the nose high attitude without ballooning and while managing the drift can be hard for new pilots. Assuming a reasonably long runway, my experience teaching has been that using 10 deg of flaps makes it much easier for the student. The naturally more nose high attitude makes the flare easier to judge, the extra 5 to 10 knots makes the controls more responsive, and as soon as the wheels touch the nose can be lowered and you get a good transfer of weight from the wings to the wheels.

However this is for Cessna's. For Grummans I teach full flap for every landing as the flaps are relatively ineffective and the landings work just as well as partial flap ones.

For Pipers I teach full flap except for crosswinds that are near, at, or over the POH demonstrated max crosswind component value, where I recommend 2nd stage flaps.

All airplanes are different and for some more extreme examples like a forward CG C182 with 40 deg flaps or a Comanche/Twin Comanche, I would say a max flap max crosswind landing is demonstrating potentially poor pilot decision
making by not respecting the handling peculiarities of the aircraft.

Couple of factors. Flap down reduces landing speed by a few knots. Those few knots reduce control effectiveness, albeit only slightly. This matters when the wind is gusty and/or near the limit of what you can handle as a crosswind.
Flap down also moves the centre of lift (in a spanwise context) more toward the fuselage. Maybe a few inches. The area of the wing with the flap down produces more lift (and drag, but that's beside the point) as the outer wing section. This has the effect of slightly reducing aileron effectiveness.

All this should not matter for a x/w of 6 knots in a 172. If the crosswind was above the demonstrated component, or very gusty up to that component, then it starts to matter. (And then available length/performance considerations need to be made.)

The most important thing is to keep flying the aircraft until it's below minimum flying speed. If the x/w is of variable strength, that means that during the hold-off you are continuously altering the bank angle and required rudder to keep the aligned with the runway and not drifting off to one side or another. At the same time you need to keep flying the aircraft, holding off for a reasonably smooth touchdown at close to normal landing speed. It's a busy time. It's tempting to try and put the aircraft down at the earliest opportunity. Don't. Once the aircraft has touched down, it's tempting to lower the nose, as it's been trained into a lot of pilots that "that's what you do in a crosswind". Don't. Keep the controls positioned to let the nose come down when it's ready. Keep the aileron and rudder inputs as they would need to be for handling the crosswind, as though you were still airborne.

That's how the instructor who kindly corrected my initially poorly learned crosswind technique* taught me, and it's served me rather well since.

My 2p.

(Flare and kick it straight just prior to touchdown, wings level, put the nose down. This technique will bust a nosewheel, sooner or later.)

Me myself I tend to use full flaps for C172 x-wind unless the crosswind is stiff. I don't think the flap setting would have had much influence on the 6 kts x-wind landing the OP asked for advice about. Simply, x-wind requires that you are current in the technique, something that is quickly lost with too long time on the ground. So just keeping practicing and it will get back to you.

I remember one particular instance though when the crosswind was right at, or even above, the demonstrated. I was using F30 and did feel I was running out rudder authority during the late part of the flare. Perhaps taken by a sudden gust, but felt like I couldn't push the nose fully aligned. Since then I use lesser flap settings when it's a good breeze across.

To each their own…

Hi Tarq57,

just so i'm clear your saying the crab and kick approach is not the best?

I was taught fly nose into the wind kick it straight as you round out, flare, wing down into wind. easier said than done for me at the moment, it is indeed a busy time.
I found that a moment of 'head in the cockpit' doing 50+ down the runway and cleaning up the flaps was enough to nearly cause a prop meets tarmac issue

I'd also like to point out i'm slightly new to tarmac runways too and their unforgiving nature, which obviously didn't help.

No, the crab, then kick and wing down with the kick technique is the better one. I believe it is the mostly taught (and probably best) one, too.

I was taught to keep the wings level and just rely on the timing of the kick a nanosecond before touchdown to align the a/c with the runway. (Which is fine if you always know exactly when touchdown is imminent; it only takes a gust to ruin the landing.)

The "other" historical way was sideslipping all the way down final, staying aligned with the runway from a long way out.

The current method is a combination of those two. The timing of when to kick it straight doesn't need to be precise. I found it seemed to be best when done at the same time as the round-out was commenced, or maybe just prior.

If you're busy during touchdown, that is not the time to be faffing around with flaps.
Don't worry, it will come with practice. You'll get to relish it. Maybe even love it. Few things are as rewarding as a crosswind landing done well in adverse conditions. And some days you can be on top of your game and just the way the wind gusts/swings, end up with a thumper.

The kick it straight in the flare sets you up for some interesting arrivals if your not spot on.

But the again taking the drift off at 500ft isn't the best plan either.

Personally I would start easing the crab out at about 50ft so that I am cross controls as I begin to flare.

On the subject of what stage of flaps to use I have always used the full lot right up to the demonstrated xwind without an issue.

Frankly flyingkiwi that is hardly a cosswind and whatever technique you use flapless or not is irrelevant as you should be able to produce a reasonable landing in any of these configurations.

Sorry to be harsh but i suspect you are either a little rusty with landings in a little cross wind or just need more time on type.

If you are sideslipping, i.e. wing down, the aircraft should already be straight! If you are crabbing, with the nose into wind there is no side-slip, the difference between track and heading being drift.You should not kick anything, maintain directional control with the rudder, you only need to align the wheels with the runway just before they touch it.

If you have a strong X wind (not 6 kts) the last thing you want is the aircraft drifting sideways over the runway before you touch down, full or land flap is put there to provide additional drag at that critical moment to minimise the time spent floating sideways, why throw it away by reducing flap settings and increasing the landing distance.

This is a shortened version of a paper I once wrote for professional airline pilots. It is based on painful experience gained in the north of Scotland where operations in winds of 60+ knots were not uncommon

An immense amount of harm has been done to pilot confidence for decades by training establishments of the RAF and some commercial schools which continue to teach the so-called "kick off drift" method of crosswind landing. For those of us steeped in the technique at a formative stage it may be difficult to accept - but this was a blind alley in the history of aviation.
It is understandable that crosswind landing finesse need not command a high priority in military aircraft, but the method gained respectability in commercial aviation in the heyday of such aircraft as the Viscount when it was considered that there was a risk of touching the inboard prop in a wing-down situation.

Leaving aside the use of the word 'kick' (which should have little place in the vocabulary of a professional airline pilot ) this technique requires a measure of fine judgement often acquired at the cost of some heart-stopping moments along the way. Its most notable drawback is that, if misjudged, it leaves the aircraft drifting downwind in a highly vulnerable state. Once the line of inertia departs from runway centre-line, the possible consequences on a slippery surface are obvious.

There is a better way!

Skilled exponents of the Kick-off-Drift system apply into-wind aileron simultaneously with the rudder input. The Controlled-Slip technique merely moves the timing of this crossing of the controls further back along the approach path. The B757/767 autopilot (which is capable of a very polished demonstration) initiates the side-slip at 500' radio. However, it should be remembered that side-slip involves a performance penalty - and there may well be windshear below 500'. It can be easier for the human pilot to stabilise the situation approaching the threshold - when the wind is more representative of that on the runway.

The Full Programme :-

1) Ensure the aircraft is tracking along extended runway centre-line. Thus, even if the pilot takes no corrective action at all, the wreckage of a tricycle undercarriage aeroplane will continue to track along line of inertia (i.e. down runway centre-line). Clearly last-minute attempts to get on centre-line cause the line of inertia to deviate from runway heading with possible serious consequences.
(If Kick-Off-Drift goes wrong and the nose is pushed down in a desperate attempt to retrieve the situation, a nosewheel-first landing will almost inevitably cause damage to large aircraft)
2) Remember that strong winds do not necessarily require more power than normal. In the 90 degree crosswind situation there may even be a tail-wind on finals. Use normal flap settings.

3) If landing from an instrument approach, resist the temptation to align the aircraft with the runway on going visual. The consequent rapid downwind drift makes it extremely difficult to accomplish step 1) above.

4) On short finals, smoothly co-ordinate an application of into-wind aileron with downwind rudder. Once the aileron input is made, this becomes a new datum position. See-sawing of the ailerons must be avoided at all costs as this is known to have given rise to go-arounds in the past.
Notice that the control inputs required are modest - and (because of the secondary effect of opposite rudder) the ensuing bank is even more modest. Thus the technique is more correctly described as ‘aileron-into-wind’ rather than 'wing-down'.

5) Having achieved a stabilised crossed-controls flight regime, a normal landing technique becomes possible. Flare as usual and close the throttle(s) smoothly. Even if the aircraft does not touch down immediately, the crossed controls ensure that it continues to track centre-line.

This is the greatest advantage of the technique.

6) A common fault is to centralise the ailerons in the flare. On swept-wing aircraft in particular this allows the upwind wing to lift. For the reasons stated above, into-wind aileron must be maintained right through the flare and landing run - particularly if the runway is wet and/or limiting.


Finally :-

It must be recognised that this technique is not instinctive. Do not rely on playing it by ear close to the ground in conditions which may change rapidly. Remind yourself beforehand of the specific aileron and rudder inputs required on the day.

But - although this was written with the swept-wing B767/757 in mind - the method works for any aircraft from the Tiger Moth upwards. (Airbuses require adaptation). Tailwheel aircraft should be landed on mainwheels only with a gradual lowering of the tailwheel/skid - but the technique permits tricycle-geared aircraft to make a normal flare - thereby removing the risk of vulnerable propellers touching the ground or nosewheels being damaged.
In aircraft without lift-dump the flaps can be retracted on touchdown to kill lift and curb any tendency to become partially airborne again!

turn of phrase whopity.

In stead of easing the crab out gradually its a more positive alignment to the runway track.

As said previously this can go round and round in circles.

Some aircraft seem to prefer decrabing and flying crossed controls and others seem to prefer kicking,easing,applying rudder just before touch down. Just like some its better to pitch for airspeed instead of point and power.

All the light aircraft I have flown seem to work well with taking the crab out just before the flare. The just before touch down in my experence does work but has a much higher chance of folk not quite getting it right. The set the rudder and hold it and control the slip with roll seems to have better results. I don't like those that say that the plane should be flown all down the approach cross controls which is just plane stupid.

The main problem with most tricycle pilots is that they don't use the rudder enough in all stages of flight and when they do use it they don't have the same controlled touch that they do with the stick. The taildragger/glider pilots don't seem to have the same problems and seem to be much more coordinated with thier control inputs.

I still cant believe a 6 k xwind is producing reams of discussion about correct technique and in depth debate (as interesting at that might be, and not that I care about a little thread drift).

However I do think (and really meant in the best spirit) while the posts will undoubtedly stand you in good stead in stronger xwinds if the OP is struggling with 6 k the best advice, is the advice they have already taken - go and do a few flights with an instructor.

6 k of cross wind is not a cross wind and should be a non event.

:)

Nor indeed in the vocabulary of a professional flying instructor-arses are for kicking, not rudder pedals.

The 318 & 321 certainly didnt, very easy even in max xwind-Airbus technology doesnt suit pilots who over control, as U tube vdeos shew!

Ouch no! Get some forward elevator on and get the nosewheel on straight away and dump flap straight away(essential in high wing a/c) in a light aircraft esp in high winds. xwinds generally produce more localised gusty conditions over the runway as they blow over the obstructions to the side of the runway. The crosswind landing is the one landing where you havent finished landing until you clear the runway.

Not mentioned so far but wind is measured at 10 metres agl, a 6 knot crosswind is only going to be about 3-4 knots on the runway.

Bad technique in a light a/c in strong croswind-wind on max into wind aileron once the noswheel is on.

Quote:
A common fault is to centralise the ailerons in the flare. On swept-wing aircraft in particular this allows the upwind wing to lift. For the reasons stated above, into-wind aileron must be maintained right through the flare and landing run

There you were supporting my thesis and you go and spoil it! Are you suggesting that the ailerons should be centralised in the flare? Even on a light a/c that would allow the upwind wing to lift and also defeat the purpose of ensuring adhesion to the tarmac on the upwind side - and build in bad habits for the future.
As I indicated in the earlier post, have demonstrated this technique on a variety of light aircraft. In particular those which have the most Xwind problems - the taildragggers (due to the innate weather-cocking tendency allied to blanking of the rudder as the tail comes down).

There is more than one way to skin a cat. But before we go on to skin another cat, answer this one, was the landing OK? If it was just firm, that will do just fine as long as it was in the right place at the right speed.

For a 172, I used to muck about a fair but on crosswinds but eventually settled for a standard, drift corrected approach and shortly before landing used to apply aileron onto wind and a squeeze of rudder to maintain the centreline. This should mean that the aircraft is banked slightly into wind. Then when flaring, keep bank the applied as you land the first wheel and the aircraft tracking correctly with the rudder. Eventually the other main wheel will land followed by the nose. Just take your time and fly the speeds. From recollection a typical approach speed was something like (43 x 1.3 + 1/2 wind) which would have given you a speed of just under 65 kts. But the the secret is to look out of the window. That will give you all the clues you need for tracking and flaring.

Don't mess about with flaps and throwing the nosewheel on the ground. If you have allowed the aircraft to land properly and hold the ailerons into wind you'll find it just won't want to fly.

PM

With my cats now safely in the house....

To support what piltdown has said, Cessnas have lots of control available to land and hold the plane on only one mainwheel with the wing lowered into a crosswind. This control remains available to to point where the wing will no longer carry the weight, and the plane settles on on its own.

My nosewheel is not lowered to the ground until the full up elevator control can no longer hold it off - ever. As long as the elevator is able to hold the nose off, the rudder is effective enough to control direction, and more so, than the nosewheel.

The following photo was taken with about a 15 knots crosswind carefully chosen to be about 60 degrees off the nose to the left. Full flaps used. The aircraft was being held stable in this attitude, at about 45 MPH. Were it to be on pavement, there would be some mainwheel chirping, as the mainwheel is also sideslipping across the surface. I'm certainly not suggeting that this degree of wing low is necessary, but it is possible in a 150/172

http://i381.photobucket.com/albums/o...t/IMG_2465.jpg

Why would you want to be flying an aircraft above the runway waiting for the speed to drop below its minimum flying speed in strong, gusty winds with shear?

Landing an aircraft has NOTHING to do with stall speed. Landing an aircraft at the slowest speed possible does.

In certain wind conditions the last thing you may want is to be anywhere near the stall speed landing.

On days with windshear approaching the flair you may want more control authority, more speed and less drag.

You can use less flap taking a higher stall speed and higher speeds.
As stated landing has nothing to do with stall speed! An aircraft can be flown on and in certain situations flying on is better than sinking on near the stall!

Pace