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Indentation On B747 Horizontal Stabilizers  
User currently offlinefaz777 From Australia, joined Aug 2011, 14 posts, RR: 0
Posted (2 years 5 months 2 weeks 6 days 22 hours ago) and read 3019 times:

Hi,

Interested at the reason there is an indentation around the insertion point for the horizontal stabilizer into the main aircraft body.

best demonstrated in this picture
http://www.airliners.net/photo/573755/M/

could it be improved airflow? i imagine the air towards the back of the aircraft would be more turbulent?

noticed similarities on other aircraft but the 747 looks to have the largest.

thanks all.

5 replies: All unread, jump to last
 
User currently offlinePapaChuck From United States of America, joined Aug 2010, 136 posts, RR: 0
Reply 1, posted (2 years 5 months 2 weeks 6 days 22 hours ago) and read 3013 times:

The horizontal stabilizer moves as one complete unit to provide pitch trim. In order to remain flush with the fuselage throughout the full range of motion, the fuselage is flattened in that area. It appears to be concave in comparison to the curved fuselage around it, but I believe it is indeed flat.

PC



In-trail spacing is a team effort.
User currently offlineRoseflyer From United States of America, joined Feb 2004, 9817 posts, RR: 52
Reply 2, posted (2 years 5 months 2 weeks 6 days 22 hours ago) and read 3004 times:

Quoting faz777 (Thread starter):


could it be improved airflow? i imagine the air towards the back of the aircraft would be more turbulent?

As mentioned, this is where the stabilizer rotates for trim control. It is mostly flat. The fuselage tapers behind this area, so there is no need for it to be flat. There is 1-2 inches of clearance between the stabilizer and fuselage skin.

Quoting faz777 (Thread starter):

noticed similarities on other aircraft but the 747 looks to have the largest.

The 747 stabilizer is the biggest and moves the most.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlinefaz777 From Australia, joined Aug 2011, 14 posts, RR: 0
Reply 3, posted (2 years 5 months 2 weeks 6 days 22 hours ago) and read 2997 times:

Thanks alot!

makes perfect sense, didn't realise the stabilizer was indeed a moving part by itself.


User currently offlineLH707330 From United States of America, joined Jun 2012, 848 posts, RR: 0
Reply 4, posted (2 years 5 months 2 weeks 6 days 21 hours ago) and read 2983 times:

Area ruling. Almost all aircraft have that pinch there. Take one of those snap-fit models and remove the tail feathers, that will make it more obvious.

Quoting PapaChuck (Reply 1):
It appears to be concave in comparison to the curved fuselage around it, but I believe it is indeed flat.

I think it is concave down to the mount, and the stabilizer swings through a swept-shape indent for +/-15 degrees for trim.


User currently offlinePapaChuck From United States of America, joined Aug 2010, 136 posts, RR: 0
Reply 5, posted (2 years 5 months 2 weeks 6 days 21 hours ago) and read 2960 times:

I must correct myself. Seems to be that area ruling is quite a common theme:


View Large View Medium
Click here for bigger photo!

Photo © Benjamin Freer


View Large View Medium
Click here for bigger photo!

Photo © Derek Morrison



Even with a slight concavity, it's still a fairly easy shape to make the horizontal stab fit flush with.

PC



In-trail spacing is a team effort.
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