2012. március 13., kedd

Rules of thumb (not just) for the bush II.

Aborting takeoff
On takeoff roll 70% of flying speed should be reached at 50% of the length of the runway or the takeoff should be rejected. The reason: acceleration is not linear.

Crosswind component
Not as tricky as most of the pilots think. If wind is 15 degrees to the runway, the crosswind component is 25% of the wind velocity (at 10 kts wind the cross component is 2,5 kts). If the wind is at 30 degrees, the crosswind is 50% wind speed (10 kts wind 5 kts component). If the wind has a 45-degree to the runway, the crosswind component 75% of the wind (7.5 kts at 10 kts wind). In case the wind is 60 degrees or higher you can calculate that the crosswind and total wind are equal. 
Descent planning
Sometimes we just forget about it, then just fall out of the sky with popping ears and unhappy passengers. If you plan ahead normally a three-degree descent gives aproximately 300 feet per nautical mile (the exact number is 318, but 300 is easier to use). Dividing the altitude to be lost by 300 should be a piece of cake. Say you are approaching an airfield at 3,000 feet and you want to know when to start a comfortable descent. You want to lose is 3,000 feet, which when divided by 300 results in 10. So start your descent 10 nm out. (And this gives a rough estimate for other altitudes too: 1500 feet would be 5 nm, 6000 feet would be 20 nm out, and so on). 
Descending, but how fast? 
To determine rate of descent for the 3 degree path, simply multiply your groundspeed by 5. At 120 knots, your rate of descent would be 600 feet per minute (5x120=600). If the descent should be initiated at 20 nm to lose 6,000 feet and your groundspeed is 120 knots  (which is 2 nm/minute), then 20 nm will take 10 minutes. And there you go 10 minutes at 600 feet/minute means you’ll lose that 6,000 feet.
Happy landings

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