CAO 20.7.4.4.1(d) says we must use no wind to calculate landing weight but landing charts have allowances for wind in them????

Does this mean we can use forecast wind conditions for runway length but not landing weight?

You stress in the book that whenever you use a forecast to determine landing weight you have to use nil wind. It would be a pretty short flight if you were using ambient conditions ??

Hi Graeme,

You cannot use the wind at the destination if you are making a go/no-go decision on whether you could land at the destination e.g. during flight planning. In the exam, if they ask you to calculate the landing distance required and provide a wind, they expect you to use it as they are testing your ability to use the charts.

The reg is there to prevent pilots planning to land somewhere based on some forecast wind which may not actually materialise when they finally get there.

Cheers,

Rich

Thanks Rich, that clears the exam bit up, but I'm still confused about real life.
If you can't use wind in a go/no go situation, when would you use it?

It might not seem terribly useful considering the restrictions placed on the use of wind by the Australian regs but we would be missing some important data on our aircraft if we didn't have a way of seeing how it performs on landing under different conditions. The landing charts do still give the manufacturer an opportunity to provide comprehensive performance information to the pilot.

Cheers,

Rich

Ok, I think I've got it.
At the planning stage, we have to assume nil wind, but can use the longest runway.
On arrival, you can then pull out your landing charts, draw some very accurate lines and decide whether to use the shorter into wind runway or the longer crosswind one. Or ask your phone to do the calculation for you of course.
That bit makes sense.

Now to make sense of the rest of real life!!!

There is no reason why you wouldn't still calculate your landing distance with the forecast wind for your own information anyway. You are just not allowed to use those results which use forecast wind to determine whether the runway is long enough.

By the way, you DO have to consider forecast wind if you are assessing the need for an alternate. If the forecast wind exceeds the crosswind capabilities of your aircraft you will need to take that into consideration.

Simple principle: always assume worst case.

For example, if you need that 30 kt headwind to land safely in the length available, you have to assume the wind won't be there and then do the maths to check if the strip is long enough.

On the other hand, if the forecast mentions a 30 kt wind right across the runway and this crosswind will exceed the crosswind capabilities of your aircraft, you must assume the wind will be there when you arrive. You could still fly to the destination and see what it is really like but you must have fuel available for a Plan B in case the winds end up being as strong as predicted.

Cheers,

Rich

Also if you check CAO 20.7.4.4.1 you will note that it is in a subsection headed TAKE-OFF WEIGHT LIMITATIONS. So if you are using a landing chart for the purpose of establishing a take-off weight you should use no wind. That is, your take-off weight is going to be limited by the landing weight at the destination.

This makes sense because you don't want to put yourself in a situation where the only way you can land legally is with a certain wind component on the runway when you cross the fence. That would be asking too much.

Subsection 5 below that says that if you wish to establish a landing weight under specified conditions you do use the wind. 5.5.1(a).