There are times when a pilot has to think fast and it is not reasonable to perform complex calculations in the cockpit. Of course it is always better to plan thoroughly on the ground before you depart, but the following rules-of-thumb should be known by all pilots .
1. Landing in gusty conditions.
If you find yourself landing in gusty conditions, it is preferable to approach faster than usual. This gives you more control authority and protection against windshear. To calculate your approach speed, you should add half of the gust factor to your normal approach speed. For example, if the wind is 7kts gusting 17kts, the gust factor is 10kts. Therefore you should add five knots to your approach speed.
2. The effect of weight on take-off and landing.
A 10% increase in weight will increase your landing distance from 50ft by 10%. It will also increase your take-off distance to 50ft by 20%.
3. Calculating a sensible approach speed.
In the absence of specific instructions in the pilot's operating handbook, a good rule-of thumb for calculating final approach speed is 1.3xVso. So if the stalling speed is 50kts, you should add 30% and approach at 65kts. Remember that Vso is the stall speed with flaps deployed and landing gear extended (think so= stuff out).
4. The effect of a tailwind on take-off and landing.
Tailwinds should be avoided during take-off and landing where possible, but if they are unavoidable, remember that a tailwind of 10% of your lift-off speed will increase your take-off distance to 50ft by 20%. It will also increase the landing distance from 50ft by 20%.
5. Estimating crosswind component.
Performing trigonometry whilst flying in the circuit is probably not viable unless you are extremely talented. Instead, the crosswind clock is a simple method for estimating the crosswind component.
Consider the difference between the runway heading and the wind direction. Reference this number on the crosswind clock and you can estimate how much of the wind makes up the crosswind component.
For example, on approach to runway 26, you are advised that the wind is 290/18. You can see that there is a 30° difference between the runway heading (260°) and the wind direction (290°). Referencing 30° on the crosswind clock shows that the crosswind component is half of the wind speed. Therefore the crosswind component is 9kts. If the wind direction is between one of the quarters, for example 40° off runway heading, then you can make an estimate, or round up to the nearest quarter (45°).
If you know the crosswind component, you can judge whether it is within the aircraft's limitations and select the appropriate approach configuration. Where the wind is more than 60° off runway heading, you may assume that it is entirely crosswind.
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