Crosswind Limits
 

My aircraft POH says, "a pilot of average skill should be able to safely land in a 15kt crosswind", and a placard inside the aircraft says, "maximum demonstrated crosswind 16kt". Nowhere is the word "limit" used.

Does this mean that it's down to the pilot's judgement? Or would an insurance company drop you like a hot potato if you had an 'incident' during a landing outside the crosswind limit?

Yes it is down to pilot skill and judgement and no it would not invalidate your insurance if you prang it during a landing with a 17kts X-wind.

It is not a lmitation.

IF my memory serves me well manufacturers only have to demonstrate that their mount is able to be landed with a crosswind component of at least 0.3Vs.

Nowt more nowt less.

That is why some STOL aeroplanes have a ridiculously low demonstrated crosswind, their stall speed is low so 0.3 * is going to be very low.

Maule = 12 mph.

They easily handle a lot more.

if it is not in the Limitations section of the POH, it is not a limit.

The factory test pilot was required to demonstrate a safe landing under available crosswind conditions using NO crosswind compensation (= very ugly). The test proved that the landing gear is strong enough to handle idiot pilots.

Thanks chaps. I've landed it with 16kt cross a number of times and the aircraft feels well within its capability. Always worth knowing the facts which are, as usual, at odds with clubhouse propaganda.

The C152 POH says there is a DCC of 12kts but it is not considered to be a limitation. From personal (supervised by a FI) experience it can be landed safely in a much greater crosswind than that - NOT that I would set out to do that, it's just good to know that, should the need arise, it can be done. :ok:

Agree on that count. When I was a student I (with instructor) landed a 152 in 25kt cross. It squirmed a bit, but no major problems.

I didn't know that. I assume this means a crabbed approach without kicking out the crab when you touch down? Ouch!

Does remind me of something else though. Apparently a 747, because of the outboard underwing engines, can't use the wing-down technique to land in a crosswind. So the recommended crosswind technique is exactly what's written above - no crosswind technique whatsoever. Just plonk it on the runway like you normally do, with up to 45 degrees of crab. The gear is strong enough to survive this, and since the main gear is behind the center of gravity, it will ensure the plane aligns itself with the flightpath/runway anyway. Videos on youtube, search for "fantastic video of crosswind landings"

Quite so, there was a little accident at Heathrow a while ago when in the middle of the flare a 747's outboard engine struck the ground. It is very easy to do I understand because the wings are so flexible and it only takes 8 degrees of contol deflection to put the engine on the ground when touching down.

Not all big jets can do that though....the MD11 apparently responds very badly to being plonked down still in the crab.

Like this :eek:

http://www.aviationpics.de/appr/slip747.jpg

Is that the Korean Air 747 that can be seem touching down on one wheel on YouTube?

It's a tough little nut isn't it? :) I know it's not all that popular in some circles, but I really enjoy flying it. It won't be that long before it's considered a "Classic" and then they'll all want to fly it. :E

I don't believe that's the case, Dirk. The test pilot isn't required to find a limit, but there's nothing in AC23-8 to suggest that the test pilot cannot use standard techniques for crosswind.

This came up a while back and I posted a link and some extracts here.
http://www.pprune.org/forums/showpos...6&postcount=18

The crosswond is demonstrated using both the crab and the forward slip techniques.

If the test pilot finds that one technique is unsuitable for the average pilot then the expected technique will be put in the flight manual.

The aircraft undercarriage must be capable of withstanding certain sideloads etc as per FAR-23 or CS-23 as appropriate. This may not be part of the flight test programme if the certifying authority accept an alternative method of demonstrating compliance.

The maximum crosswind demonstrated during test flying of the aircraft is specified in the flight manual. If you choose to use a higher figure then feel free to be a test pilot. However, please check your insurance for the small print about using the aircraft for development testing.

When you have demonstrated the higher crosswind, please let the manufacturer know......they will either amend the flight manual or recomend that you have the aircraft checked due to undercarriage side load limitations.

I wonder which? ;)

Regards,

DFC

I love it!

Should result in all sorts of .. .. ..

:)

Stands back and waits.

How does a properly executed wing-low landing put sideload on the undercarriage again?

Not so - the correct technique for low wing airliners is to use rudder to ease off the crab at the last moment (ie in the flare) whilst using aileron to prevent wing drop. Failure to squeeze off the drift places an uncomfortable load on the undercarriage - even if it not damaging in the short term, it's not good for fatigue in the long term.

I say this as a pilot of low wing jet airliners!

As for maximum demonstrated crosswind, whilst it may be LEGAL to exceed it, it's probably not SMART. As it is the maximum demonstrated, no-one can say for certain what the actual maximum safe crosswind is. Therefore, any excursion beyond the demonstrated maximum is a journey into the unknown.

Think about it this way - juggling with chainsaws is legal - but is is SMART for the average person to do it?

We have a simple rule at our FTO - we treat the maximum demonstrated as a limit. Full stop, no questions. That way we all know where we stand.

Unless the nose is pointing straight ahead down the runway and there is absolutely NO side drift there will be sideload on the gear. Have you ever carried out a perfect x-wind landing where this has been the case (no side drift, nose pointing exactly ahead)?

During certification according to FAR part 23 the applicant is not required to demontsrate the emptying of the ashtrays during flight (nor, for that matter on the ground). There's no reference to the procedure in the AFM. Do I become a 'test pilot' when I attempt this manoeuvre? ;)

Doesn't the maximum demonstrated crosswind for landing just depend on the wind strength on the day that part of the certification was undertaken?

You make it sound like it's the holy grail or something. I learnt at, and am now based at Leeds, so yes, I have thanks. I know a lot of people are terrified of crosswinds, but one adapts to one's surroundings. A lot of GA fields have the luxury of multiple runways and some PPLs have never had to deal with a crosswind landing, but as with everything it's all about practice. During my training I did several circuit sessions which consisted of flying along 3ft above the runway for 1000m or so at 60kt in a 14kt xwind, wing down, anchored to the centreline, before doing a touch and go.

I flew recently with a friend who learnt at Sherburn. As we headed back towards Leeds I had a listen to the ATIS and the surface wind was 260/14 for runway 32. The whole concept of flying sideways on final, then landing left wheel, right wheel, then nosewheel was completely alien to him.

Not saying I'm any better or worse a pilot than anyone else, but I know how to land with a crosswind. It's a handy skill, maybe more people should learn it :rolleyes:

Hah, that question killed me on my flight test.
"So can we land at this airport?"
"No, there is a crosswind of 19, the aircraft can only maintain 15kts."
"Actually, that's just what the maximum demonstrated was, I'm sure by the time you finish your commercial license you can do a 19kt crosswind landing."

As of today, I've tried a few times, max I can hold is a 17kt in a 172M model and it isn't fun either.

"So can we land at this airport?"
"No, there is a crosswind of 19, the aircraft can only maintain 15kts."

However a reply of:

"No, there is a crosswind of 19, I have decided that for the time being my personal limit is 15"

would be fine. (As long as you'd thought up, in advance, your answer to the obvious next question: "so, if you knew you weren't going to be able to land, why did you take off then".)

(Having said which I did take off the other day knowing full well that I wasn't going to attempt the landing due to the crosswind. It was an IMC lesson, and I did tell the instructor before we started that I wasn't going to take off unless he did the landing, so no problem.)

Bookworm,

This info comes from a Beech engineer who was present during certification of the BE35, he is dead now unfortunately. The demonstrated crosswind landings need to be done in front of official observers to count.

I have done landings myself at twice the demonstrated crosswind component of my aircraft but I have more than average time on type. It took more than average skills to do that and I am not sure I want to try it again.

For us taildragger guys, it is preferable to do one of these 'perfect' landings rather than ground loop. It always helps to have lots of practice, tugging gliders has given me this opportunity. I'm currently working on my instrument rating in an Arrow and it lands fine in crosswind too, just have to remember to kick the rudder out before the nosewheel touches down.

-- IFMU

Have you ever carried out a perfect x-wind landing where this has been the case (no side drift, nose pointing exactly ahead)?

Yes, thousands of them, in fact that is what I strive for on every X/wing landing.

And generally I succeed in touching down pointed straight down the runway with no sideways drift.

"We have a simple rule at our FTO - we treat the maximum demonstrated as a limit. Full stop, no questions. That way we all know where we stand."


Sounds like an idea in theory, but if the rental pilot leaves with a light crosswind, and returns to a stronger one, do you send him away?

Then there are those of us for whom the max demonstrated crosswind is limiting... In Sweden, max demonstrated is the legal max limit. Sensible or not, inconvenient as it is, that's what the law says... *shrugs*

Oh, it was the ground part of the flight test. The runway length also wasn't the best to try a 19kt crosswind for a first either.

Never mind the perfect wing down landing with no drift.

Jack up one side of your aircraft so that the main wheel on that side is clear of the ground and tell me that there is no side-load on the other main wheel. Now lift the aircraft clear of the ground in that attitude and drop it from 6 inches and tell me that there was no side-load. That is not even close to the requirements.

While personal limits are good, commercial pilots are expecetd to be able to fly to the limits imposed by the flight manual and the ops manual. having an FTO ops manual with an approved crosswond limit of 17Kt and saying to the examminer that while the manual says 17, my personal limit is 12 without further realistic justification on a CPL flight test will not go down well.

Perfectly acceptable and very commendable however as a PPL because no one is going to be paying you to perform to a certain standard.

Regards,

DFC

DFC,

OK, I've just done exactly that. Here is the main body of the letter (with my details removed):-

Customer Services
Cessna Aircraft Company
P.O. Box 7706
Wichita KS 67277

11th November 2007

Dear Sir/Madam,

I am the owner of a UK-based XXXXX, and I would very much appreciate your advice.

The POH for my aircraft state that it has a demonstrated crosswind landing velocity of 21 knots. Three days ago, I was forced to execute a landing with a crosswind component of around 28 knots.

I executed a crabbed approach followed by a wing-low landing, touching down the right main wheel first, then the left and finally the nose wheel having centralized the rudder. This seemed to work perfectly and is a technique I have used many times.

However, I have been advised by someone who claims to have vast knowledge and experience that I should inform you of this occurrence, as he feels that you will either wish to modify the POH for the aeroplane, or that you will now advise me to have the aircraft checked for “under-carriage side load limitations”.

Are either of these comments correct ? Or is what I did (as I believe) perfectly OK, because the demonstrated capability which is contained in the POH is not intended to be a limitation ?

I understand that any comments which you might make will be on a “without prejudice” basis, but I really would be grateful if you could help clarify this matter.

Many thanks,

----------------------------

I will publish the reply.

FF :ok:

Did you have official FAA experts witnessing the landing?

I have written similar letters to the other Wichita based aircraft company several years ago and am still waiting for reply.

POH's are written by engineers, then rewritten by the marketing department, then completely rewritten by the legal department.

I get the impression that most manufacturers "Demonstrated Crosswind Landing Limits" are erring on the side of caution. Presumably for product liability and insurance reasons. There are some aircraft with landing gear known to be at risk of side loads, yet the majority seem to handle landings at greater than these demonstrated figures without problems. I would have thought the sensible thing for designers to do is make the control authority the limiting factor. The other thing mentioned in this thread is training. I did mine at a school with multiple runways, so coping with crosswinds was not something I got that much experience of. Having operated from a single runway for 15 years now, my knowledge is considerably greater. I personally feel that a bit more training should be carried out with respect to short/narrow/crosswind runways. How many times have we read accident reports where the pilots first experience of small airfields was unfortunately not a very pleasant one?.

Good call. Look forward to reading that :)

I certainly always get the impression that the xw "limit" was more about how far the test pilot was prepared to push the aircraft during testing and the level of wind at the time (apparently the Tristar's autoland would be certified for a 35+ xw if they had found such a wind at the time) rather than a true reflection of how good the aircraft is. The Bulldog for example has a demonstrated figure of 35 which is insane for a light aircraft, but part of that is surely that the test pilot on the day had the 'luxury' of a 35 knot wind and was maybe a little bit braver than your 'average' test pilot.

The PA28 can take more than 17knots (as I discovered doing solo circuits during my PPL :=). But the Cub I would never, ever push beyond its limit.

I also learned at an airfield with, in my case, three runways but I had an excellent FI who ensured that I got plenty of crosswind landing practice by waiting until there was no other traffic in the circuit then requesting a runway change. Multiple runways doesn't have to equal poor training.

True, but currency is so important with crosswinds. During my PPL I went through a phase of the wind often being near the 17k demo for the plane (at a single runway airfield) and soon became an expert at crosswind landings...then after my PPL I went a while without facing a serious crosswind. Then I had a check ride to fly the club's almost brand new Archer and was faced with a 17k crosswind...I really struggled and to my embarrasment the instructor said to me "I have control...just let me show you how to make this easier". In short I had got rusty in only several months.

Multiple runways I think do lead to less crosswind currency.

But don't you find it more fun to land with a crosswind?
I always request a runway for a crosswind if possible.

I'll admit...I do relish the challenge.

My home airfield is single runway so most of the time the question doesn't arise anyway. Landing away I usually just take the runway I'm given...mostly because circuit traffic dictates that but also because funnily enough taking the runway that is NOT facing into wind doesn't usually occur to me!

It's alright for you lot, I don't have the luxury of a rudder to kick the drift off! Come to think of it I don't have an elevator or ailerons either...

I discovered many years ago that is possible to land a flexwing microlight on tarmac in a 15 gusting 25kt - 90degree crosswind. I still remember the faces peering out of the club house as I taxied (very carefully) towards the apron.

Later the same day, having enlisted several helpers to de-rig my machine and put it in a hanger, I accepted the offer of a trip back to base with the farmer who owns the grass strip I use. Not by road, but in a PA18 Cub! After a particularly bumpy flight he got it into the 300 x 10 yd runway on the 3rd attempt. By this time our local Airport was reporting gusts up to 31kts. I believe the Cubs POH doesn't mention a specific crosswind limit, but leaves it up to the pilots discretion.

I don't fly in those sort of conditions nowadays.
Old pilots, NOT bold pilots??

In the POH for the PA18-135 I fly it states 10 knots as the max demo xw...I did once hear someone claim to have landed one in 20 knots...but after a friend of mine ground looped one in almost still air conditions I won't be pushing my luck ;).