Crosswind landings

[RetiredBA/BY]

What is the current teaching/ practice of the RAF for crosswind landings, particularly on large jets, eg Voyager, Sentry, A400 etc?

[charliegolf]

First, stow your camera?:E

CG

[Onceapilot]

Obviously, it will be appropriate to the type. You finish with etc, but I guess you mean large aircraft generally? FWIW, the TriStar was approved by Lockheed for drifted or wing-down, up to 30kts x component in most conditions. However, RAF SOP taught wing-down. :)

OAP

[Onceapilot]

VP,
Lockheed cleared either landing with drift applied or, wing down TD. "Kicking-off" drift is not a generally approved commercial transport technique. The wing down technique was approved with a limitation of 8 degrees of roll at TD, sufficient for a correctly applied aligned landing with 30kts across. However, the technique was not easy to master. Of course, A/L did it perfectly! And, so did some of us pilots! :ok: :D

OAP

[Onceapilot]

TriStar 500 wing pod clearance is 2'11". Don't think an RAF TriStar pod was ever scraped, despite routinely working into windy places. :cool:

OAP

[Onceapilot]

https://www.facebook.com/XinhuaNewsAgency/videos/239088153429356/UzpfSTU5NTYzNTU0NjoxMDE1NjAxMDU3MTE5MDU0Nw/?comment_id=10156011027185547&notif_id=1540055670638499&notif_t=comment_mention

Intersting!

Yep. You try teaching it to a 150hrs TT Tyro! :eek:

OAP

[MPN11]

Ahh ... the link finally worked ... I had deleted the original post!

A good bootful of rudder at touchdown [and afterwards!].

[RetiredBA/BY]

Once a pilot is wrong. I did my Boeing conversion at Seattle and they approved my crab, push off drift technique, hold wings level or slightly into wind, as did my conversion with BOAC onto the VC 10. The Boeing training manual said that wing down or crab was recommended x wind technique. It’s what I taught as a CFS approved RAF. QFI.( and as a Boeing TC) and what we did on the V aircraft ( underwing tanks and refuelling pods) and Canberra. ( wingtip tanks)

My x wind technique was taught to me as an RAF stude and for the rest of my career, I used the crab , push off drift in the flare to land aligned with the runway..

Landing with drift appplied was not considered good airmanship to say the least.

I ask the question as I recently saw a video of B 757 ( on which I have a lot of command time) being landed in a 40 knot x wind with no attempt to remove the drift angle. it looked truly awful.

I wondered what was being taught, is acceptable, these days.

Informed comment from those up to date?

[Onceapilot]

Retired BA/BY is wrong! :ooh: Are you incapable of reasoned dialogue? Who mentioned Boeing, VC10 or your crab? :)

OAP

[Onceapilot]

Or Canberra's? :confused:

OAP

[Onceapilot]

Where are you BA/BY? Do you want to slag a fellow CFS Flying Instructor again? Or, do you want to talk about flying aircraft TWICE the MTOW of your resume? :mad:

OAP

[Bill Macgillivray]

I thougt that the original question referred to current RAF teaching - not specific aircraft types. All my RAF career (Many types and QFI) was the "crab" technique. Seemed to work, still here after some 20k hours!
Bill

[Onceapilot]

I thougt that the original question referred to current RAF teaching - not specific aircraft types. All my RAF career (Many types and QFI) was the "crab" technique. Seemed to work, still here after some 20k hours!
Bill
It was referrenced to large jets. Agree, my experience of Flying training and FJ was crab (drift corrected) to align in the flare. However, most decently large modern aircraft have approved operating standards that are very specific and are further defined by operator/company SOP's.
Would be glad to hear comments from other RAF big jet SOP's? :ok:

OAP

[H Peacock]

Wing-down will always work, ensuring you land with no lateral drift, but it does mean a podded engine may be too close to the ground. Conversly, if you elect to crab, then unless you get it exactly right you're either going to land with lateral drift (ie you kicked the drift off too soon) or you'll still be crabbed off (ie kicked the drift off too late).

Of the various RAF ME types I've operated I've used both techniques, or even a blend of them (ie a bit of wing down but also some crabbing). The geometry of the tailwheel types requires them to be flown accurately aligned and with absolutely no lateral drift - so had to be flown wing-down, but also to a relatively low crosswind limit. The tricycle types will always yaw themselves straight after touchdown if you've not got it right, but it can feel very uncomfortable and can't do the gear much good.

Dont think I've ever seen a modern airliner using the wing-down technique.

[Onceapilot]

The tricycle types will always yaw themselves straight after touchdown if you've not got it right, but it can feel very uncomfortable and can't do the gear much good.
No. With a crosswind they will still experience aerodynamic Yaw forces into wind after TD. Large commercial aircraft have limiting structural strengths that have to define the landing technique. Many seem to certify the full drifted landing as the worst case. See video of X-wind certification landing tests.

OAP

[H Peacock]

OAP. I agree about the aerodynamic forces (yaw) always being present at touchdown, but I'm referring to just the CofG v undercarriage geometry.

[itsnotthatbloodyhard]

"Kicking-off" drift is not a generally approved commercial transport technique.

OAP

Interesting. It’s certainly approved on the B747s, B767s and A330s I’ve been flying for the last 20 years. Not only approved, but strongly preferred by my outfit. (Although ‘squeezing off’ might be a better description than ‘kicking off’.)

[Onceapilot]

Interesting. It’s certainly approved on the B747s, B767s and A330s I’ve been flying for the last 20 years. Not only approved, but strongly preferred by my outfit. (Although ‘squeezing off’ might be a better description than ‘kicking off’.)


Interesting. I would be interested what it says in your operating manuals under "Crosswind landings", or "Crosswind landing technique". Maybe you can explain what your A/L does? Cheers

OAP

[Onceapilot]

OAP. I agree about the aerodynamic forces (yaw) always being present at touchdown, but I'm referring to just the CofG v undercarriage geometry.
Yes. :ok:

OAP

[BEagle]

I once had to defend a TriShaw pilot who'd alarmed some REMF FJ Wg Cdr at MPA by 'large bank angles near the ground' on the final approach. Having spoken with ATC and obtained a tape, although the PAR was poorly flown, the final approach attitude was clearly due to the ex-Hercules pilot using the 'wing down' technique in the usual MPA crosswind, which was alien to this FJ Wg Cdr. In fact I'd been on board the TriShaw at the time and the landing seemed entirely routine from a passenger's point of view.

Anyone who 'kicks off' the drift or uses 'bootfulls' of rudder deserves a good kicking themselves! One merely aligns the aeroplane with the runway at the same rate which one uses to initiate the flare. Once down, into wind control column and forward pressure helps - although FBW aircraft may have some control laws of their own, I guess.

But if an A380 can cope with 40-50 kt crosswinds using the wing down crab technique, I'd have thought that pilots of smaller aircraft should also be able to manage the technique:

https://youtu.be/Rdi-hnFrmag

[H Peacock]

Beagle, my understanding of 'kicking off the drift' simply refers to the action, not the finesse! If you don't kick off the drift ie use your feet on the rudder, how else do you do it??

[BEagle]

'Kicking' implies a sudden sharp input. Entirely unnecessary - just use a squeeze of rudder to align the aeroplane with the RW as you flare. Exactly as in that A380 video.

Modern aircraft probably compensate for the rolling moment which develops if a large yawing rate is used in swept wing aeroplanes.

[deltahotel]

Boeing 757/767 Flight Crew Trg Manual allows wing down (max25 kts xwd), crab followed by rwy alignment and crab only up to the ac xwd limitation which for the 757 is 40 kts. Not pretty, but legit. My RAF experience was ‘kicking off the drift’ for most ac and wing down for C130. The 75/76 doesn’t compensate for the roll due to yaw.

[H Peacock]

'Kicking' implies a sudden sharp input. Entirely unnecessary -

oh dear me. The entire aviation world understands the concept of 'kicking off the drift' except Beagle!

[BEagle]

Only that part of the 'aviation world' which persists in using incorrect descriptions!

[doubletap]

Always found offsetting the Cockpit from the centreline a tadge during the approach helped prevent the usual dick-dance trying to regain it during the rollout. BTW, some B737 variants had 5° of castor built into the mains which (unofficially) tolerated a small amount of crab angle during touchdown

[Duchess_Driver]

oh dear me. The entire aviation world understands the concept of 'kicking off the drift' except Beagle!

Sorry, but I am with BEagle on this. When instructors teach, especially when teaching someone whose “mother” tongue is not the same as yours it is vital that there is no ambiguity in what is being described. I’ve seen it so many times - a student being told to “push forward on the stick” resulting in an aggressive “bunt” or agricultural handling.

Back on topic... Boeing testing the triple...

https://m.youtube.com/watch?v=ljOxo0s33sI

[Onceapilot]

Boeing 757/767 Flight Crew Trg Manual allows wing down (max25 kts xwd), crab followed by rwy alignment and crab only up to the ac xwd limitation which for the 757 is 40 kts. Not pretty, but legit. My RAF experience was ‘kicking off the drift’ for most ac and wing down for C130. The 75/76 doesn’t compensate for the roll due to yaw.


Thanks for that DHotel. The usual mix, with certified limit using fully drifted landing it seems? Can you comment on 75/76 Autoland, does it not use ALIGN (which is wing down) and what x-wind limit?

OAP

[Onceapilot]

Thanks for the Vid DD! B747 and B777 doing fully drifted TD's, not aligning in the flare, maybe a hint of heading in the right direction on TD in one of those.:) Again, would be interested what the Makers certification for X-wind limit landings is? I guess, fully drifted to TD?

OAP

[deltahotel]

OAP. A/L xwd limit 25 kts. The align mode is a sub mode initiated about 500’ which adds some wing down (max aob 2deg) if the crab exceeds 5deg, so a bit of both really. Very rare for lo vis to have much in the way of windiness so i’ve not seen a lot of this going on.

As as for terminology ‘kicking....etc’ is a bit of shorthand and I sort of take the view that no one is going to be using this forum as a definitive teaching aid for technique.

dh

[RetiredBA/BY]

OAP has got the wrong end of the stick, I was NOT slagging anyone off, just trying to have a reasonable discussion.
I related some of my experience to show I was not a 200 hr ppl and was trained by some of the very best quality organisations including the manufacturer of the aircraft I mentioned. ( although I have also operated the 767, quite a bit heavier than the 75). Decrab worked on that too!

I WAS however disagreeing with his statement, paricularly after discussing the issue with close relative, a former Airbus and now 787 training captain.

It it is interest that in “Handling the Big Jets” D P Davies describes removing the drift angle of a crabbed approach ( by pushing it off NOT “kicking “ his words) by co-ordinating the rudder input with aileron to keep the wings substantially level, particularly for podded engines.

Can we not not keep the discussion polite and objective?

[Onceapilot]

OAP. A/L xwd limit 25 kts. The align mode is a sub mode initiated about 500’ which adds some wing down (max aob 2deg) if the crab exceeds 5deg, so a bit of both really. Very rare for lo vis to have much in the way of windiness so i’ve not seen a lot of this going on.

dh

An interesting mixture on the 75/76 then, even with A/L limited to 25kt x-wind using a mix of crabbing and wing down. Cheers

OAP

[ORAC]

https://www.youtube.com/watch?v=TCUHQ_-l6Qg

[Mogwi]

Don't understand the problem; just turn the runway into wind - or land across it! Second bit works in the Tiger as well.

Mog

[Onceapilot]

Hello BA/BY,
So good of you to return to your topic. I agree that you should keep your discussion polite and objective. :)
Now, instead of rudely referring to me (or anyone else) in the third person, as you still are, may suggest you are less rude and use the second person when addressing a forum member?
Cheers

OAP

[Onceapilot]

ORAC
B52, all the main gears can align with the runway. You probably know! ;)

OAP

[BEagle]

The crosswind landing gear function is checked whilst taxying in the B-52. It felt weird to be moving diagonally across the RW at Barksdale whilst looking directly ahead when I experienced it!

[MPN11]

The port outrigger apparently on the grass adds an extra dimension. I assume B-52s prefer 200ft wide runways.

[57mm]

Never needed any of that kicking off drift nonsense in the F4.....

[ORAC]

Never needed any of that kicking off drift nonsense in the F4..... Just followed the grooves in the concrete from the last landing.....

[deltahotel]

VP. Morning.

Hope I haven’t contributed to confusion. Mr Boeing’s FCTM for 75/76 does indeed allow all three techniques (wing down, crap n kick, crab alone). I’m guessing your experience is 4 jet which is likely to be more problematic than my 2 jet. All that being said, our company teaching ( and my pref) both sim and ac is crab and straighten. If the ‘kick’ is a touch too early then maybe a little wing down to keep on the cl. There is also the ‘throw it on the rwy like a sack of spuds’ technique which has served me well on the grounds that 150T of Boeing at 150kts is a lot of inertia!

Finally for accuracy and clarity any aob applied for A/L is removed when ‘rollout’ engages at 5’radio, but i’m usually so pleased to have got that far that I don’t really notice that bit.

rgds

[pontifex]

When I trained in Canada (1956) I was taught the wing down technique. It worked a treat, particularly on Harvards (a well known beast). Back to the UK, where the QFIs considered Canadian trained students to be incompetent, I was forced to use the "kick of drift" method. I always prefered the former. And so it continued until, as a TP at Boscombe, I was tasked to investigate X wind landing techniques for Nimrods going into Stanley and C130s in really tough conditions. There was no doubt that the wing down method was the best. I subsequently flew the Lanc. Previous OCBBMS's told me horror stories of truly awful Xwind landing experiences using the RAF "KOD". Not surprisingly I elected to us wing down and I can honestly say that the heart rate never flickered! The Lanc also made me realise that, using wing down, the aircraft always reached terra firma with the controls exactly as required for the roll out whereas with KOD you touch down any old how. I subsequently taught civilian students wing down and they took to it like ducks to water. As I am sure readers will understand this is my pet subject. SORRY!

[Fareastdriver]

As a passenger who used to fly in the smoking area down the back of a 747 the wing down technique was by far the preferred option.

The alternative lurch sideways when a pilot kicked off drift just before touchdown would empty your glass of wine slightly before one had planned to.

[heights good]

Only that part of the 'aviation world' which persists in using incorrect descriptions!

You reallly must need some long therapy if your constant need to be correct over an almost universally accepted term is so strong! It is draining to read in most of your posts.

Can I suggest the following link to help you explore your defensive and inhibitory emotions.

Sent with love, not for an argument or requiring any reply....

https://www.hilaryjacobshendel.com/what-is-the-change-triangle-c18dd

[RetiredBA/BY]

Thank you for your replies, v interesting!

I have discussed the issue with an ex Concorde and DC10 colleague, crab, push off drift approved on both types.

So, OAP, it is a fact that, having covered Boeing , Airbus, MacD and Concorde, all of which approve crab and drift removal I think, contrary to your statement that it IS a generally approved technique in commercial airliner ops!

No idea what you are talking about, first, second or third person nonsense. ( and if you are ex RAF Tristar. I doubt if you have flown one at twice the weight of a 767 ER, it’s only 65 k lighter than the 1011)

However, the question was what is the RAF teaching, seems it’s mixed.

I still remember an interesting discussion at Boeing . They explained that the crosswind limit was the maximum DEMONSTRATED during certification by them, and the aircraft controllability was almost certainly able to handle greater limits.

I used my crab technique on my conversion in Seattle , they were happy with that and signed me off.

They also explained that that a fully crabbed landing was acceptable because less skilled line pilots might do it! The structure could handle it.

However, because it it could be done didn’t mean it SHOULD be done if a smoother technique, such as wing down, crab /drift removal could be used.

I am more than happy to take the word of the manufacturer’s test and training pilots !

Anyway I think we have put the issue to bed.

Thank you for your replies.

[SASless]

I thought all RAF landings were Crab landings.:E

[sycamore]

On the naughty step,,,,SAS

[heights good]

I thought all RAF landings were Crab landings.:E

:p :p :p

Made I chuckle... a lot!

[heights good]

In some the smaller types none of those techniques were used, it all rather... redundant.

Just point into wind, reduce speed to zero and land..... once the skids/wheels are on, disembark pax or shutdown. Simples! ;)

[wiggy]

Comments about the F4 and drift..agreed :E

747 and crab vs. Wing low....wing low really not liked in the flare where/when I flew it outboard engines, pod clearance in the flare etc ...

FWIW from current 777 FCTM...

”Crosswind Landing Techniques-Three methods of performing crosswind landings are presented. They are the de-crab technique (with removal of crab in flare), touchdown in a crab, and the sideslip technique.”

Touchdown in full crab approved for slippery runways.
Sideslip with zero crab allowed in up 28 knot crosswind.
Dry crosswind limit 45 knots (removal of crab in flare)...

[H Peacock]

Dry crosswind limit 45 knots (removal of crab in flare)...

So why do the RAF always seem to put such a crap limit on the max crosswind for most types - invariably 25kts? Hugely limiting on flying in the windy UK! Or is it simply the way it is with risk adversity moving ever higher up the list?

[Easy Street]

The fins of modern airliners seem proportionally larger than those of older in-service types like E-3 and RJ. But are modern RAF transport aircraft like Voyager and C17 so limited? 25kts sounds more like a limit associated with fast jets or trainers, possibly with small fin/rudder or external stores.

[Chris Scott]

Must beg the forbearance of you military and ex-military types for one of my occasional intrusions into your forum. But, as you seem to be talking about the comparatively banal task of landing transports, I reckon we've all been playing the same ball-game. Like RetiredBA/BY, since retirement I've been surprised by the increasing prevalence - judging from videos taken from near the approach lights - of guys making no noticeable attempt to de-crab. The Boeing video (https://www.pprune.org/military-aviation/614707-crosswind-landings-2.html#post10291927) from Duchess Driver shows four landings, of which only the third shows a full de-crab. The fourth shows a partial de-crab with the simultaneous introduction of a little wing-down. When test pilots refrain from de-crabbing, they would no doubt tell us they were simply demonstrating that the L/G can cope with the sloppiest technique on a dry runway...

Plenty of good stuff here, but I'll take this one for discussion:

Wing-down will always work, ensuring you land with no lateral drift, but it does mean a podded engine may be too close to the ground. Conversly, if you elect to crab, then unless you get it exactly right you're either going to land with lateral drift (ie you kicked the drift off too soon) or you'll still be crabbed off (ie kicked the drift off too late).

Agreed, except that, as well as PPPP-PP, practice helps. Unfortunately, the long-haulers don't get much of that.

Of the various RAF ME types I've operated I've used both techniques, or even a blend of them (ie a bit of wing down but also some crabbing). The geometry of the tailwheel types requires them to be flown accurately aligned and with absolutely no lateral drift - so had to be flown wing-down, but also to a relatively low crosswind limit. The tricycle types will always yaw themselves straight after touchdown if you've not got it right, but it can feel very uncomfortable and can't do the gear much good.

Agreed, although Onceapilot has a point (https://www.pprune.org/showthread.php?p=10291644).

Dont think I've ever seen a modern airliner using the wing-down technique.

Evidently not a 'plane-spotter!

IMO, the (roughly-speaking) three dry-runway techniques - [1] wing-down; [2] slight (late) wing-down during de-crab, and [3] wings-level (full) de-crab - are chosen as appropriate to the aircraft type.
Looking back on a short-list of various types, the following are my suggestions.
Heron [3] or [2], but minding the upwind prop.
C-47: [1], and wheel it on.
Dart Herald: [1], but avoiding wheel-barrowing and ensuring downwind wheels firmly on the ground before using any downwind brake :O .
VC10: [2]. Although the only limiting factor was the outboard flaps, I never saw [1] demonstrated, and perhaps the tanker guys will comment, pod-wise;
B707-320 (JT3D turbofans): [3], due to outboard engine nacelles, but no doubt the experts could use [2]. The later KC-135s with CFM-56 engines presumably stick with [3]?
BAC1-11: [1] or [2].
A310: [2], bank slightly limited by engine nacelle;
DC-10: [2], although the auto-land adopted [1] at 138'R - but only enough for a 20-knot crosswind, if memory serves. Cockpit needed to be well upwind of the centreline prior to de-crab.
A320: [2], although - being FBW - the manufacturer recommended [3], claiming that the zero roll-rate command from the side-stick would prevent the upwind wing rising during de-crab, and that crossed controls were not recommended. But [2] works very well. I imagine the A330-200/Voyager (with similar FBW) would be comparable?

[captainsmiffy]

The A380 requires the crab technique but, bizarrely, the aircraft decrabs around the cockpit - more or less. God alone knows what the FCS does to achieve this. Previous types, for me, had me sat over the grass before a decrab and the cockpit was at the end of a long arc as you de-crabbed. My turbo-prop time was on a high wing and lent itself well to the wing down method, although one ex RN chief pilot of mine professed much alarm at this technique, claiming never to have heard of it before when I demonstrated it, whereas I was taught it on the Bulldog from the word go. I used to teach this method on light singles and had much success with low hour pilots....the 380 geometry would not allow this though.

[DCThumb]

oh dear me. The entire aviation world understands the concept of 'kicking off the drift' except Beagle!

The terminology IS important.

In the 90s the USAF lost a C130 doing asymmetric training because the training Captain told the Co pilot to ‘boot the ball’ - which he did leading to fin stall and the loss of all on board.

The worst landing I have experienced in a large aircraft came when an inexperienced FO read the OM which said words to the effect of ‘kick off the drift’. As he flared he did just that! We dropped like a brick, bounced (despite ground spoiler deployment) before settling on the runway. Easyjet at the hold even transmitted a disparaging comment!

To answer the original quote, though. The RAF do not have a standard teaching, the technique deemed appropriate for each type, whether by the OEM or Handling Sqn, is taught. So for the Herc, which has to be landed straight due to undercarriage design, it is wing down. For Sentry, Sentinel etc, it is crab.

[Fly26]

De-crab in the flare, adjusting aileron into wind is what’s primary on the 737-800 for what it’s worth with a 40kt x-wind landing limit Wet/Dry. I guess the P-8 would be similar...

[H Peacock]

But, as you seem to be talking about the comparatively banal task of landing transports,..

Hey, CS, that's probably the only bit of handling an airline driver gets these days!

DCT - The 'concept' is a far removed from the actual airborne instruction/brief! If you tell a co who perhaps doesn't know better (not an RAF co then) to 'boot the rudder' then more fool you for not anticipating his possible mis-interpretation.
So why do you have to use wing-down in the Herc; if you correctly kick off the drift in the flare you still land straight and with no drift (the whole point of this thread is it not - apart from the do nothing option and land without aligning to the runway orientation)

[DCThumb]

Hey, CS, that's probably the only bit of handling an airline driver gets these days!

DCT - The 'concept' is a far removed from the actual airborne instruction/brief! If you tell a co who perhaps doesn't know better (not an RAF co then) to 'boot the rudder' then more fool you for not anticipating his possible mis-interpretation.
So why do you have to use wing-down in the Herc; if you correctly kick off the drift in the flare you still land straight and with no drift (the whole point of this thread is it not - apart from the do nothing option and land without aligning to the runway orientation)



The C130 crosswind technique is the most reliable method of landing straight - any sideways force on landing damaged the ‘shelf brackets’ on the undercarriage. It makes absolute sense. Why risk someone misjudging the flare and damaging the aircraft, when they can get it straight pointing down the runway first? With a high wing, there is no disadvantage to it. The touchdown order is often one side mains, nosewheel then opposite mains! It’s what you get used to!

[Chris Scott]

Yes HP, I was simply acknowledging that some posters on here may regard crosswind landings as one of their less-demanding tasks.

As captainsmiffy and DCThumb have said, the wing-down technique lends itself so well on most high-wing transports (of which there remain a wide variety. in civil and military service). It was great on the Herald. The only question is: at what height do you best transition into the sideslip? I would suggest that it needs to be done early enough to get the feel of it, but not so early that your downwind leg starts to tremble with the effort as you come over the threshold...

[SASless]

One teaching method I used in the western part of the USA was to have the Student fly along a barbed wire fence....as out west those section lines can go for hundreds of miles and if one flies the north/south lines....you always had a cross wind.

Then when they returned to the airfield....lining up and maintaining a track along the runway was a piece of cake to them.

That worked for crabbing or slipping (wing low) methods.....and going back and forth between the two.

[mahogany bob]

The Sentry,in my opinion,was a 'bitch' to land in a X/wind ( hence perhaps the low limit of 13 kts on a wet r/w ! ).

After a lot of poor (hairy)) efforts I learnt a few basics as follows:

1. Plan ahead - get precisely lined up early.
2. Fly - by rote - ie 50ft gently check the rate of descent - 20ft power off SLOWLY and at the same time gently push off the drift and apply max aileron into wind- to avoid a pod scrape.

Definite no no's were blagging it at the last moment with large corrections ( too much momentum ) and kicking off too much drift resulting in getting the wrong side of the wind.

Happy landings

[ExAscoteer]

So why do you have to use wing-down in the Herc; if you correctly kick off the drift in the flare you still land straight and with no drift (the whole point of this thread is it not - apart from the do nothing option and land without aligning to the runway orientation)

While the MLG on the Herc will withstand large vertical accelerations, any significant sideways thrust at touchdown is liable to damage it at best and knock it off at worst. Hence the wing down technique.

[5aday]

Best x wind aeroplane ever- 747.400. Drift remains on up to 40knots across and better if very slighty damp. (GRU)
Worst xwind aeroplane ever - DHC6 Twin Otter. Land across the runways into a taxiway if you can . (Unst)
Best twin jet B737-17R from Maersk Air on contaminated runways in Varga, Lulea, Umea, and the old Funchal (at night)

[LOMCEVAK]

A few thoughts to add:

One of the main aerodynamic characteristics of interest is 'sideforce' which is the lateral force generated by sideslip; just think of the fuselage as a wing on its side. If you fly a wings level crabbed approach and then yaw the aircraft through the drift angle just prior to touchdown you generate sideslip, and the resulting aerodynamic force will generate a lateral acceleration across the runway. If the sideforce characteristics are strong, ie. a lot of aerodynamic force per degree of sideslip, a large lateral displacement across the runway will occur and at touchdown the landing gear will experience large sideways loads. In a tailwheel aircraft with the c.g behind the mainwheels any such lateral velocity will result in a tendency towards directional divergence, better known as a ground loop!

In a wing down approach the drift angle equals the angle of sideslip that is needed to align the fuselage with the runway. The bank angle required to maintain constant heading for a given sideslip angle is a function of the sideforce characteristics discussed above, the greater the aerodynamic sideforce produced, the greater the bank angle required. Therefore, high sideforce characteristics increase the possibility of a wing tip or wing-mounted engine pod strike on the runway. The bottom line is that, irrespective of technique, if sideforce characteristics are high then the crosswind limit will probably be low.

One of the other differences between a yawed, decrab landing and a wing down landing is that the former is a short term, transient manoeuvre following a 'normal' approach but the latter is a stabilised, steady state manoeuvre with sideslip applied. Therefore, if a wing down approach is stabilised early there may be drag generated, which will require more thrust than on a zero sideslip approach, and there may be a pitching moment requiring a different pitch trim setting and making the flare feel different. Therefore, a wing down approach may not be the same to fly as one flown in no crosswind.

The F4 was flown crabbed to touchdown because it had an aileron-rudder interconnect and very high lateral stability (apparent dihedral effect). If you had a crosswind from the right and flew a crabbed approach, if you applied left rudder to 'kick off drift' the aircraft would have a tendency to roll left and the large right stick input to prevent the roll would displace the rudder to the right, thereby reducing the left rudder input that you had made to align the aircraft with the runway.

In an aircraft with strong lateral stability such as the B747, it will roll markedly as you kick off drift. This will then require aileron firstly to stop the roll rate and then to correct the bank angle back to wings level. The combination of these two responses may result in full lateral control being inadequate. A good technique in aircraft with such a characteristic is to lower the into-wind wing slightly before the rudder is applied so that as the wing rises you can use aileron to arrest the roll rate and, if you judge it correctly, the bank stabilises at wings level.

On a wet, low friction runway, in a strong crosswind an aircraft may drift laterally across the runway due to the low sideways friction of the tyres attempting to oppose this. Therefore, landing with the crab applied gives an inertial vector which is straight down the runway, thereby reducing any tendency to drift downwind once on the ground.

It is all a compromise and in some aircraft more than one technique may work. Try to decide what is best for you and your aircraft. And beware of old, historical Pilots' Notes because the recommended technique may have been a 'standardisation' from the period and not necessarily the optimum technique.

[CharlieJuliet]

Best technique I found doing several landings on a day with a 45 kt crosswind was wing down. The big advantage was that this was a stable condition and on touchdown there was no worry about drifting downwind. Any thoughts?

[stilton]

Our flight manual guidance for both
the 757 and 767 when first delivered
was to maintain the crab angle throughout
touchdown on wet runways to reduce downwind drift on rollout



Dry runway recommendation was to
align just before touchdown by pushing
off drift with the rudder


No ‘kicking’ !



An unfortunate term to describe very
poorly what should be a smooth, deliberate
input




Furthermore some pilots will take the
expression seriously!

[Chris Scott]

A few thoughts to add:
In an aircraft with strong lateral stability such as the B747, it will roll markedly as you kick off drift. This will then require aileron firstly to stop the roll rate and then to correct the bank angle back to wings level. The combination of these two responses may result in full lateral control being inadequate. A good technique in aircraft with such a characteristic is to lower the into-wind wing slightly before the rudder is applied so that as the wing rises you can use aileron to arrest the roll rate and, if you judge it correctly, the bank stabilises at wings level.
Thanks for neatly elaborating the technique listed as [2] in my earlier post (https://www.pprune.org/showthread.php?p=10293959). Never quite got to fly the B747, but lowering the wing immediately before de-crabbing certainly works well on the A320, on which I got more crosswind practice than on other swept-wing jets, and on which the wing-down technique is probably impracticable because of its FBW.

On a wet, low friction runway, in a strong crosswind an aircraft may drift laterally across the runway due to the low sideways friction of the tyres attempting to oppose this. Therefore, landing with the crab applied gives an inertial vector which is straight down the runway, thereby reducing any tendency to drift downwind once on the ground.
Yes, although I suggest that partial de-crab is still advisable, unless you are unfortunate enough to have to land on an icy runway. The FCOM of at least one type, IIRC, suggests half de-crab on a wet runway?

[Bill Macgillivray]

Thought that this was the "Military Aviation" posting page?

[LOMCEVAK]

The cross wind landing techniques and laws of aerodynamics are the same for both civilian and military aircraft!