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Old 25th January 2003 | 13:14
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Kingy
 
Joined: Dec 2002
Posts: 321
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From: Bristol and Forest of Dean
Book Worm

You also neglect the wind in your assessment. A headwind makes matters worse still. Imagine an aircraft that rotates at 60 knots taking off into a 25 knot headwind. It will reach an IAS of 30 knots almost immediately in the take-off roll, but has a very long way to go before it gets airborne.
Ok, if I understand this correctly you are saying a headwind on takeoff makes take off distance Longer!

You are in effect getting the first 25kts for free and the aircraft would only need a 35kt ground speed to become airbourne. Granted these 35 kts may not be gained as fast as the first 35kts in a nil wind situation, but remember the drag from the undercarriage also increases with the square of the speed so there is a drag saving to be had.

Once airbourne the aircraft will climb at a steeper angle into wind and this will help obstacle avoidance - but that's another thread..

Reading the air accident reports I can't recall one where a light aircraft ran off the end of the strip into a stiff headwind!

Kingy
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