Crosswind "legalities"

[FullyFlapped]

Yesterday, the wind at my (now single runway) home airfield was blowing 70 degrees off the runway, at 5 knots more than my POH shows as the "maximum demonstrated crosswind".

Now, I know that the book shows a *demonstrated* value rather than an absolute maximum, and I know full well that the plane can handle 5 knots above this value (I've done it without problems a few times).

But what is the legal status of this figure ? Is it *legal* to fly above the POH number - even if not advisable ? Or is it a complete no-no ? And where do I stand on insurance if I do fly under these circumstances ?

FF :ok:

[High Wing Drifter]

Well I passed my CPL skills test landing in a 20kt crosswind in an aeroplane with a max demonstrated of 17kts. Of course, if I hadn't recognised and announced the situation I would have failed. But I think it is an example that the demonstrated is not a limit.

I belive, the demonstrated could simply be the highest crosswind that the test pilot had the opportunity to fly. Therefore I would be very suprised if such a situation would compromise your insurance.

[2Donkeys]

The maximum demonstrated crosswind is not limiting in the case of most flight manuals. Whilst your insurer will require you to obey such limits as G limits and others, figures such as the max demonstrated crosswind are informational only.

However... some clubs and syndicates do define maximum crosswind components, and insurers will sometimes specify that the aircraft should be operated in accordance with Syndicate/Club rules. If you find yourself outside the crosswind number under those circumstances, your insurance might be at risk.

2D

[bookworm]

I belive, the demonstrated could simply be the highest crosswind that the test pilot had the opportunity to fly.

It doesn't even have to be that. It has to be at least 20% of stall speed in landing configuration.

The key points is that, not only is the value advisory, the manufacture is not required even to determine a limiting value.

[dirkdj]

The demonstrated crosswind component is nothing more than the demonstrated strength of the landing gear if the pilot would be making a landing without any crosswind compensation.

Nothing to do with aerodynamic limitations.

[IO540]

dirkdj

It can't be quite that, because if the rudder has insufficient authority at Vs then the aircraft will go off the runway, at both takeoff and landing.

Also, the side forces on the landing gear can vary over a wide range depending on how long one keeps the aircraft on one wheel after landing; the longer the better.

It's true that it is just a demonstrated figure.

However, the test pilot might have been exceptionally skilled. The TB20 for example has a max demo xw speed of 25kt. I can tell you that you have to be bl**dy good to land it at a real 25kt xw. And I mean real 25kt, not what one usually gets at airfields which is a "25kt" reported xw from an anemometer at the top of a tall pole, with the actual surface wind (at say 2-3ft off the runway) being far less.

[Rod1]

An interesting coincidence

TB20 25kn
Robin DR400 22Kn
MCR-01 20Kn
B Pup 25kn

All the above are European

Most US aircraft are 15 –17kn (I know there are exceptions)

So, either the European test pilots are better than the US guys, or the US has stronger product liability laws…..

Rod1

[High Wing Drifter]

This article agrees with my definition of demonstrated:
http://www.aopa.org/asf/publications/inst_reports2.cfm?article=3651

The Wassmer Europa also has a 25 kt demonstrated crosswind.

[M14P]

DirkDJ's assertions are not correct.

As far as IO540 describes a 25kt wind is one that is measured at 30ft (or 10 metres).

Whilst Bookworm mentioned the lower certification criteria the actual value will be the lower of two values - either the highest windspeed at which controllability was not an issue (TPs assume the 'net pilot') or the highest value witnessed (often seeked out) during the certification period.

Some aircraft have a gusting value also.

The Bulldog, for example, has a 35kt limit :ooh: but the gear is extremely sensitive to side loading :ouch:

A very fine reason for crosswind limitations being 'demonstrated' (and therefore somewhat woolly) is that in strong or gusty wind conditions the actual tower wind value may not be terribly close to that of the touchdown zone wind. This is especially true if the tower is using a 10 minute average.

If you plan as if it is a 'hard' value and fly what you feel comfortable with then it is unlikely that you will end up foul of any insurance implications.

cheers

m

[bookworm]

Whilst Bookworm mentioned the lower certification criteria the actual value will be the lower of two values - either the highest windspeed at which controllability was not an issue (TPs assume the 'net pilot') or the highest value witnessed (often seeked out) during the certification period.

I don't think it even has to be that:

23.233 Directional stability and control

(a) A 90 degree cross-component of wind velocity, demonstrated to be safe for taxiing, takeoff, and landing must be established and must be not less than 0.2 Vso.

23.1585 Operating procedures.

(a) For all airplanes, information concerning normal, abnormal (if applicable), and emergency procedures and other pertinent information necessary for safe operation and the achievement of the scheduled performance must be furnished, including--
...
(2) The maximum demonstrated values of crosswind for takeoff and landing, and procedures and information pertinent to operations in crosswinds;

The value recorded for the purposes of 23.1585 is the maximum value that was demonstrated for the purposes of 23.233. There is no requirement that this is the highest value witnessed.

[Malcolm G O Payne]

The maximum demonstrated cross-wind is just that. The strongest crosswind experienced by the test pilots during the test flying of the aircraft. As an instance the Cessna 152 has a lower cross-wind limit than the 150. If you operated outside the demonstrated limits and had an accident your insurance company may use it as an excuse not yo pay out.

[Rod1]

So the Demonstrated crosswind figure depends in the winds over the test flight period, the liability laws in the country of test and the skill of the test pilot. Not very scientific is it?

I know of at least 5 aircraft, which have been written off, or very seriously damaged, attempting to land in crosswinds substantially higher than the figure in the manual, all received full payment on the insurance. On one occasion the crosswind was over 40k with a 17-knot DCC.

I know that the insurance question is always raised when this subject is discussed, but is their anybody on the BBS who had not been paid because they crashed whilst landing in a strong crosswind? I think this may be a myth invented by a CFI one day when he lost the argument about it being a limit!

Rod1

[Gertrude the Wombat]

I don't care what the DCC is.

I don't even care what it says in the club flying order book - someone has sneakily increased it to 15 kts in a recent revision, but my performance (dual) with a (gusty) 14 kts crosswind a couple of years ago was sufficiently frightening (to the instructor!) that I'm staying on the ground in those conditions.

[Say again s l o w l y]

The myth about the strength of the landing gear is just that, a myth.

As has been pointed out, the C150 and 152 have different demonstrated crosswind values (12 and 17kt if my memory serves correctly. It has been 2 years since I went near one of them thank goodness!) this difference was subscribed potentially to the difference between tecniques for crosswind landings between the test pilots. Since they are virtually identical airframes, there is no difference in the strength of the landing gear.

I have often flown a/c well outside of the cross wind limits and I have instilled in me, my own set of personal limits. The worst being a 40 kt gusting crosswind at night.......... In driving rain.....(Basically the sort of time you find out that adrenaline is brown in colour! Don't do it, it's neither big or clever.)

For the club, I insist on people at different stage of training having different limits, for example a first solo is not allowed in any more than 5kts of x-wind, whereas a PPL is allowed upto the limit as procribed in the book, but this is not an absolute limit to ensure that there can be no potential insurance snafu's in case of an accident.

The word "demonstrated" is an advisory limit, the Yanks use it since they are worried about someone sueing them for loss of control at a lower wind speed and then insisting that the a/c should of been controllable despite the obvious lack of pilot skill rather than a/c malfunction or design causing any problems.

[FullyFlapped]

Errr .... OK, so I think the concensus is that the value is not legally binding, and that if I tawse it up when landing in a higher cross wind than the book specifies as "max. demonstrated crosswinf limit", I'll have no insurance problems ?

FF :ok:

[S-Works]

If you thought you were going to mess it up at a higher figure then its time to impose a lower limit on yourself?

I fly out of a strip that allthough it has 2 runways in the winter we can only use one so we regularily fly in very stiff crosswinds. The 152 I own is easily controllable at 25kts at 90d to the runway and I have put it down a couple of times approaching 30kts. But I fly 350plus hours a year and have over 1000hrs in that particular plane if I was in something new I would work up the experiance over time.

The twin is very sensative and exceeding the limits has the potential to pull the undercarriage off as has happened to someone in it this year!

[FlyingForFun]

As has been pointed out, the C150 and 152 have different demonstrated crosswind values Hmm. I don't have the manuals to hand, but I'm 90% certain that they both have cross-wind limits of 12kts. At least, that's what I've been teaching for the last 18 months, so if I'm wrong it's very worrying for me! I'd better check when I get into work tomorrow.....

And I also believe that the C152 manual explicitly states that this is not considered to be limiting, as does the C172 manual (although the limit for the C172 is 15kt). I think the C150 manual says the same, but I'm not so certain.

FFF
--------------

[FullyFlapped]

Bose-X

If you thought you were going to mess it up at a higher figure then its time to impose a lower limit on yourself? Gosh, why didn't I think of that ?

Where precisely did I suggest that I'm stupid enough to attempt something which I think is beyond my own personal limits ? I was simply asking for advice relating to views taken by insurance companies in relation to landing accidents with respect to the POH figures.

You have a fair few hours : have you never experienced anything unexpected which has the potential to ruin your day ?

Anyway, it's the season of goodwill and all that, so I'll just put your comment down to a rush of blood to the head ... mind you, I thought those posh headsets were supposed to be comfy ... ;)

Merry Christmas!

FF :ok:

[S-Works]

Blimey FF have you got PMT?

It was a question hence the question mark at the end of it!!!

I did not suggest at all that you were stupid, I think you might have been a little over sensative!!!

And yes I get my day ruined a lot, landed back in the dark no wind and full flap the other day and bumped all over the place and nearly off the runway. What possessed me to use full flap is beyond me! I have done that same arrival hundreds upon hundreds of times in the dark and never needed full flap.

A moments lapse can be embarrassing but at least my passenger was good humoured about it!:O

[FullyFlapped]

Bose-X,

PMT ? Nah, unless it means Post Marvellous Tandoori, which is what I've just had ! ;)

No offence taken, old bean.

So are those headsets really that comfy ?

FF :ok:

[homeguard]

There appear to be many variations as to the actual meaning of 'demonstrated crosswind component'. However i've always understood it to generally mean this; the crosswind component within which the average pilot in current practice may reasonably be expected to land the aeroplane safely.

This is a qoute from a Linda Pendleton article on the 'avweb' website;

Federal Aviation Regulations require that all airplanes certificated after 1962 have safe ground handling characteristics with a direct crosswind component of 0.2 Vso. If your airplane stalls at 50 knots in the landing configuration, it must have a demonstrated crosswind component of at least 10 knots. (0.2 x 50 = 10) Many airplanes do better than the minimum. The Cessna 172R Skyhawk, for example, lists a demonstrated crosswind component of 15 knots.

Direct qoute from the Cessna Skyhawk Owners Manual;

"The maximum allowable crosswind velocity is dependant upon pilot capabilty rather then airplane limitations. With average pilot technique, direct crosswinds of 15mph can be handled with safety".

[High Wing Drifter]

From the Seneca 3 PoH:

"The demonstrated crosswind velocity is the velocity of the crosswind component for which adequate control of the airplane during takeoff and landing was actually demonstrated during certification tests."

[S-Works]

FF, yes they are REALLY that good! Thousand hours on the current set and still going strong!