1. 1% downslope = 10% more runway

2. 2% upslope = 8 mph tailwind

3. 10 knot headwind reduces stopping distance by 150'

4. 10 knot tailwind increases stopping distance by 500'

5. 10% speed increase = 21% landing distance increase.

6. 50' extra altitude at threshold adds 1000' to landing distance.

7. "Duck unders" from 50' adds 4 to 8 kts. and up to 400' additional rate of descent.

8. Total length of strip means little; obstructions can halve the total usable distance.

9. Each 1000' of density altitude increases ground roll 25%.

10. A 700 fpm climb at sea level becomes 140 fpm at 11000'. At 80mph, in level terrain, that puts you 315 agl at 3 miles.

11. An eighth inch of frost increases takoff distance 50%.

12. To determine ruway lengh: 70 mph x seconds x 1.5 (70 x 12 x 1.5 = 1260'; use 2-way average in wind).

13. At 80 mph and 1000fpm, you need 710 horizontal feet for every 100 feet of obstruction. (to clear a 50' obstacle by 50', an additional 1000' of runway is needed)

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