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Old 31st August 2007 | 21:30
  #44 (permalink)  
Ashling
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Joined: Nov 2003
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From: Over the Moon
AirRabbit, no one is trying to insult anyone here. Bit direct at times but just healthy banter.

You have still not addressed my observation about your definition of the straight and level attitude. In your first post you said.

It is whatever attitude that is the “level flight” attitude for that airplane, in that configuration, and at that airspeed. What airspeed? The airspeed you have upon completing the flare.
If you select that attitude it is too high. Why ?

Remember Boeing ask you to flare 2-3 degrees from your approach attitude.

Take a calm day. 3 degree glide at a constant Vref +5, constant power and landing config. Now we raise the nose 3 degrees (max Boeing recommend) in order to flare and we will have selected the straight and level attitude for that config at Vref +5. However in reality we know the speed will have decreased in the flare so our nose attitude will in reality be too low for straight and level if we only raise it 3 degrees. Boeing assume Vref at the end of the flare so we have lost 5kts of speed which Boeing equates to 1 degree of nose attitude. So if we want the straight and level attitude at the speed at the completion of the flare, as you recommend, we will have to raise the nose by another degree. That will mean we will have raised the nose 4 degrees overall, from the approach attitude, which is too much.
Why is this significant.

a. its nice to get it correct

b. tailstrike. In a 800 the tail bangs at just over 9 degrees oleos extended. Boeing assume a landing attitude of anywhere between 4 and 7 degrees depending on weight, flare etc. So if you flare 4 degrees you may have just over a degree of grace or put another way just over 5kts of grace. Not so much then.

I would appreciate it if you could address this concern over your definition of the attitude.

Cheers
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