View Full Version : Demostrated Limit

3rd Feb 2004, 18:10
Within the limits sections of our Flight Ops Manuals are
'Maximum crosswind demonstrated'
for both takeoff & landing.

Do you read this as a limit not to be exceeded?

If this figure is exceeded & an incident or accident follows, where do we stand legally?

Mark 1
3rd Feb 2004, 20:24
As I understand it, this isn't imposed as a limit for several reasons.

It cannot be determined exactly as wind will vary by height, location, time etc., so the pilots observed wind may vary either way from a reported wind.

Upto the limit of being able to roll out in a straight line using available control forces, the requirement is one of pilot skill in transitioning from a crabbed or wing down approach to a touchdown without appreciable sideways drift. Thus a more experienced and skilled pilot may reasonably attempt a higher crosswind than a less skilled pilot.

So it comes down to airmanship and judgement (not to forget SOPs of course)

4th Feb 2004, 05:57
I think the legal term for where you stand is 'the dock'.

The book for the aircraft I fly actually states crosswind limits for dry, wet and contaminated runways.

If the destination weather includes a crosswind exceeding this, then two alternates are required.

I believe private pilots occasionally end up with their insurers refusing to pay out in case of accidents under these circumstances the argument being that whilst it is not prohibited, it is reckless, ill-advised, imprudent, unwise or irresponsible to operate outside of the known parameters of the aircraft.

I hope some-one can provide a more detailed reply.

4th Feb 2004, 18:30
The test to establish the ’demonstrated’ crosswind requires landings on each end of a runway with a measured wind at 90 deg. Where the manufacturer does not find that the control of the aircraft was limiting then a ’demonstrated’ value is published. Rarely, where the limit is found then the limiting value is published.

For those aircraft in which I demonstrated the crosswind performance, the control limit was not found. However it was decided not to look for any higher crosswind as the general conditions were such that the approach turbulence would have detered most pilots – difficulty in lining up, and if that failed the repeated windshear warnings should have reinforced the need to go around / divert.

Yet some national authorities approve operators to fly to limits 5 kts above those flown by the manufacturer. Take care, treat demonstrated values in mature aircraft as limiting, use a lower personal limit, and reduce these values further on wet runways. Seek your management’s support in stating that the manufacturer's demonstrated values (or less) are the company’s never exceed limits and that decisions to divert at any time based on pilot judgement are not critisised.

The pilot is always the first at the scene of an accident and as such the first in the firing line, legal or otherwiswe.