Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
DC9 Flaps/Slats VS. 717 Flaps/Slats  
User currently offlineBR715-A1-30 From , joined Dec 1969, posts, RR:
Posted (11 years 4 months 3 weeks 3 days 1 hour ago) and read 4805 times:

I have noticed on the 717, that when the Pilots Lower the Flaps/Slats, they don't make that loud "KERPLUNK" Sound. But on the DC9, They make that sound and drop suddenly. Has anyone else noticed this, and why are they different, when the wing is basically the same?

4 replies: All unread, jump to last
 
User currently offlineI LOVE EWR From United States of America, joined Jan 2002, 852 posts, RR: 7
Reply 1, posted (11 years 4 months 3 weeks 3 days ago) and read 4750 times:

Hmmmm....let's think about this for a little bit. I am by no means an expert on the DC-9 vs. the 717 Flaps/Slats and I have never thought about it on my 20 years on earth but here it goes.

Maybe just maybe its because the DC-9 Technology is about 40 years old and the average age of the DC-9 is older than I am? I would think that a DC-9 has a lot more wear and tear than a 717 would thus making a few creaky old parts in the Hydrallic lines. Speaking of Hydrallics I bet the 717 has a MUCH more efficent hydrallic system, thus the noise differences.


User currently offlineAirplanedude From Germany, joined Apr 2003, 15 posts, RR: 0
Reply 2, posted (11 years 4 months 3 weeks 1 day 21 hours ago) and read 4600 times:


Uuuuuuuuuuuuuuuuuhhhhhhhhh..........

not beeing familiar with Boeing stuff too much, I'm just making a guess.

Here are the little bits of what I have memorized on Boeing / MD. Please, do not quote me on that, and if there are any eyperts out there who know better, I'd be glad to be educated.

OK, here's my guess:

DC-9 use afaik a drooped hinge-type High lift surface support and guidance mechanism. Meaning the flap surfaces are attached to a pivot arm. And that's why they seem to drop immediately.

Boeing 707-220 uses afaik arc tracks to deploy the flaps, whereas I do not know exactly how these are driven (Pinion/Rotary Actuator/Linear Actuator/... Anyone?) These will -most likely- move the flaps differently than a drooped hinge system does, the circular path they move along is not dependant to the length of a pivot arm (=Circle radius). Such an arc track could almost have "any" shape or radius. Hence, the movement of the flaps would look different.´Sound may be different depending on what kind of power drive is used.

Boeing 727 for instance uses a track-carriage type surface guidance and support mechanism. As well, Flap surfaces do not move on a circular path. The move somewhat more linear. Again, sound depends on type of power drive.

What the 717 does, I have no clue.

Anyhow, I'd say it is more a matter of the mechanical part of the flap system architecture and design that decides about the way the flap surface movement looks to a spectator, and as well it depends on the design and architecture of the power drive system what it sounds like. I would not say it is necessarily only a matter of aircraft age (=technology level). A hydraulic piston-actuated system will always sound different from a track-carriage system using hydraulic motors.......


Cheers,

Airplanedude


User currently offlineCritter From United States of America, joined Jan 2000, 267 posts, RR: 2
Reply 3, posted (11 years 4 months 3 weeks 3 hours ago) and read 4496 times:

The thud that you hear is coming from the slats not the flaps. The thud is actually the slat tracks bottoming out on the mechanical stops. All of the slats are connected together through cables and bolts. Thus the left side and the right side reach there collective end at the same time.......result...a loud thud. As to the difference in sound from B717 to DC-9.......I am not sure. The system is essentially the same, unless Boeing placed some sort of dampener on the control drum. It has been awhile since I had my hands on a B717 or DC-9 for that matter, so my memory is a little rusty.


critter


User currently offlineAirplanedude From Germany, joined Apr 2003, 15 posts, RR: 0
Reply 4, posted (11 years 4 months 2 weeks 6 days 14 hours ago) and read 4575 times:


Like I said, just making a guess.  Wink/being sarcastic Never heard it myself, and never had the opprtunity to be aboard a DC-9.

Critter:
Interesting. I have barely no knowledge or information on 717 high lift (esp. Slat) actuation. Let me ask you some questions, if you do not mind.

-All of the slats are connected together through cables and bolts.
Are you talking about some sort of slat panel interconnection? Or are you referring to the power drive or some special means to accomplish synchronisation of the left and right slat panels? Or is the power drive accomplished shafts?

-For slat actuation, what kind of actuation mechanism is used? Rack-pinion sort of beast or more something like a linkage-system? Linear actuators or Rotaries? Pistons?


Would be glad if you could take the time to explain.

Cheers,

Airplanedude


Top Of Page
Forum Index

Reply To This Topic DC9 Flaps/Slats VS. 717 Flaps/Slats
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
Slats & Krueger Flaps posted Tue Jul 12 2005 18:15:03 by DH106
Difference Between Flaps And Slats? posted Fri Apr 1 2005 17:36:42 by JAM747
Why Slats And Flower Flaps? posted Sun Mar 27 2005 18:45:55 by Nikrc
Flaps/slats Warnings posted Thu Mar 28 2002 23:51:21 by 2912n
Re: 757 Flaps/Slats posted Fri Nov 16 2001 11:47:43 by Blackbird
Flaps/Slats 757/767 posted Wed Oct 24 2001 22:37:02 by Blackbird
Aerodynamic Effects Of Gaps In Slats/flaps posted Thu Jul 26 2001 23:34:53 by Modesto2
Slats/Flaps During Takeoff? posted Tue Jul 17 2001 10:31:14 by SUDDEN
DC-10 / MD-11 Flaps/slats Question posted Wed Jan 17 2001 04:03:31 by Blackbird
Flaps Landing Vs Flaps Takeoff posted Fri Oct 29 2004 01:23:19 by Flybynight

Sponsor Message:
Printer friendly format