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Just what the title states; I was browsing photographs and it struck me how aircraft tails typically 'stand' atop the fuselage. A few aircraft (think it dates to the 40s-50s) have a tail that projects both up-and-down from the fuselage.

Why do aircraft not have tail projecting downwards? Is it merely because a bad landing would render the aircraft incapable of flight until repairs were effected, or is there a scientific reason other than monetary?

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It would make it pretty difficult to take off. As it is modern airlines almost scrape the tail on the ground during takeoff. –  John Rennie Feb 12 '12 at 15:08
    
A better place for aviation questions is probably airliners.net/aviation-forums/tech_ops –  nibot Feb 12 '12 at 15:53
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-1: This is off-topic; it's not physics. –  nibot Feb 12 '12 at 16:06
    
@JohnRennie has it exactly right. In fact, some aircraft like this learjet have tailfins underneath just to try to get more aerodynamic area underneath the tail while still allowing it to rotate on takeoff without endangering the tail. –  Mike Dunlavey Feb 13 '12 at 0:58
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closed as off topic by Qmechanic, nibot, dmckee Feb 12 '12 at 20:21

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1 Answer

up vote 2 down vote accepted

During takeoff, aircraft rotate from a horizontal attitude to a climb attitude. This is one reason the fuselage tends to taper towards the aft of the plane, and why the vertical stabilizer (tail) doesn't extend downwards: it would hit the runway.

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Landing too...the typical approach is in a on a 2--4% descent, but with a angle of attack rather more than that. It insures that the rear wheels come down first. –  dmckee Feb 12 '12 at 16:59
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Some aircraft eg UAVs do - they are light enough that they can have long thin undercarriages to allow the tail to clear the ground –  Martin Beckett Feb 12 '12 at 17:09
    
@dmckee: Jets land one way, slower prop planes land another. In a Cessna 172, you are encouraged to practically stall it onto the ground, very nose-high. That way, when you touch, you won't bounce because your lift is gone. Stalling a jet is very poor form. You land much flatter. Then to kill lift you have spoilers (big top panels that pop up) to get your weight onto the wheels as quickly as possible. –  Mike Dunlavey Feb 13 '12 at 1:20
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