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Horizontal Stabilizer Travel Area  
User currently offlineVidens From Argentina, joined Mar 2004, 133 posts, RR: 0
Posted (11 years 9 months 2 weeks 1 day ago) and read 3507 times:

I have noticed that most airliners have a flat area on the fuselage to allow the horizontal stabilizer to move up and down.
My question is:
Why is that area flat so much in front of the actual travel area of the stabilizer?

Travel? Why would i travel if I can watch it on TV?
5 replies: All unread, jump to last
User currently offlineInvictus From Germany, joined Aug 2004, 64 posts, RR: 0
Reply 1, posted (11 years 9 months 2 weeks 21 hours ago) and read 3400 times:

HUH? What are you talking about dude?  Confused

The captain of my soul.
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 66
Reply 2, posted (11 years 9 months 2 weeks 18 hours ago) and read 3319 times:

View the thing from above. The fuselage is a cone at this point - the diameter is greater forward of the horizontal stab and smaller aft of it. Of course the recess is going to be greater where the cone is larger. The horizontal stab rotates but any point of it stays in a plane parallel to the aicraft centerline.

This came up here recently because a passenger made a big fuss and refused to board one of our planes because it had this big "dent" and no one would do anything about it. She was referring to this recess to allow the stab to pivot.

Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineJHSfan From Denmark, joined Apr 2004, 469 posts, RR: 2
Reply 3, posted (11 years 9 months 2 weeks 9 hours ago) and read 3271 times:

Hey Videns

Unfortunately you have not made any reference to a picture. That would have been a help.

But take a look here:

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Click here for bigger photo!

Photo © Normando Carvalho Jr.

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Photo © Dale Coleman
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Photo © Enio Beal Jr.

I guess part of the mechanism for adjusting the horizontal stabilizer is located in front of the stabilizer (inside the fuselage).
If you take a closer look at the 777 and the 747 then this area seems smaller than on the A320 and the 737. Since the big planes have a bigger fuselage then there is (almost) enough room inside the tail cone for the mechanism.
On the smaller planes the tail cone has a bigger dent above and below the stabilizer to create enough space inside the cone for the mechanism. The reflection above the stabilizer (starting at the windows) on the A320 clearly illustrates this dent.
Part of the reason for this big surface could be the need for smoothness to reduce aerodynamical resistance from the tail.

Yours in realtime

Look at me, I´m riding high, I´m the airbornmaster of the sky...
User currently offlineQantasA332 From Australia, joined Dec 2003, 1500 posts, RR: 22
Reply 4, posted (11 years 9 months 2 weeks 9 hours ago) and read 3266 times:

The 'dented' surface around the horizontal stabilizer's trim path has nothing to do with fitting the mechanisms that move the stabilizer. Rather, the depression simply forms a smooth and continuous plane for the control surface to move on - if it weren't there, the front and back of the stabilizer would sort-of stick out, due to the tapering of the tail.


User currently offline320tech From Turks and Caicos Islands, joined May 2004, 491 posts, RR: 5
Reply 5, posted (11 years 9 months 2 weeks 2 hours ago) and read 3243 times:

QuantasA332 is correct (of course). On the A320, the mechanism for operating the stab is called the THS (Trimmable Horizontal Stabilizer) Actuator. The THS Actuator is mounted on the front spar of the stab. It's quite compact, and does not require any change to the fuselage profile.

The primary function of the design engineer is to make things difficult for the manufacturer and impossible for the AME.
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