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Swept Wings And Winglets At Low Speeds?  
User currently offlineKaitak744 From United States of America, joined Jul 2005, 2373 posts, RR: 3
Posted (6 years 6 months 3 weeks 3 days 23 hours ago) and read 4353 times:

Quick question:

I noticed Cessnas and other small planes do not have swept back wings or winglets. Is it because those two design features offer little to no advantages at low speeds?

thanks

10 replies: All unread, jump to last
 
User currently offlineFredT From United Kingdom, joined Feb 2002, 2185 posts, RR: 26
Reply 1, posted (6 years 6 months 3 weeks 3 days 22 hours ago) and read 4343 times:

Swept wings are only useful as you accelerate into the mach numbers.

Winglets are not worth the effort for most GA aircraft. You are not span limited, they would add to maintenance and cost and the aircraft are from an aerodynamical standpoint poorly finished anyway, meaning it'd be like putting jewelry on a pig. Hoerner tips or other lift-enhancing wing tip devices, which do effectively the same thing, are not uncommon though. This is especially true in STOL applications.

If you look at the more modern GA aircraft, such as the Diamond range, where more attention has been paid to aerodynamical detail, you also find winglets incorporated into the basic design.

[Edited 2008-02-11 00:13:03]


I thought I was doing good trying to avoid those airport hotels... and look at me now.
User currently offlinePilotpip From United States of America, joined Sep 2003, 3150 posts, RR: 11
Reply 2, posted (6 years 6 months 3 weeks 3 days 7 hours ago) and read 4246 times:

The stall charateristics also have a HUGE roll in the reason that a wing design is chosen. Rectangular wings stall at the root first which is desireable in a training aircraft because the ailerons maintain some effectiveness. Swept wings stall outboard and you have some other issues which are undesirable in trainers.

One of the primary selling points of the early citations was that they were very simple from a systems standpoint. You could jump from a kingair into a citation with minimal training.

Everything in aviation is a tradeoff.



DMI
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 3, posted (6 years 6 months 3 weeks 3 days 4 hours ago) and read 4222 times:



Quoting Kaitak744 (Thread starter):
I noticed Cessnas and other small planes do not have swept back wings or winglets. Is it because those two design features offer little to no advantages at low speeds?

Winglets would work, but increasing the span is much easier and more effective.

Quoting Pilotpip (Reply 2):
Swept wings stall outboard and you have some other issues which are undesirable in trainers.

Swept wings only stall outboard if you've screwed up your washout. All of today's swept-wing commercial airliners stall at the root.

Tom.


User currently offlinePilotpip From United States of America, joined Sep 2003, 3150 posts, RR: 11
Reply 4, posted (6 years 6 months 3 weeks 3 days 2 hours ago) and read 4200 times:



Quoting Tdscanuck (Reply 3):
Swept wings only stall outboard if you've screwed up your washout. All of today's swept-wing commercial airliners stall at the root.

Interesting. I've never heard that. Then again, the PLI, shaker and pusher should help prevent any of the above from happening.



DMI
User currently offline57AZ From United States of America, joined Nov 2004, 2550 posts, RR: 2
Reply 5, posted (6 years 6 months 3 weeks 3 days 2 hours ago) and read 4194 times:



Quoting FredT (Reply 1):
Winglets are not worth the effort for most GA aircraft.

Generally true, though they are effective for the larger cabin class twins. You'll find quite a few Cessna 400s with them now as they provide a much better MTOW and increase the average cruise speed by several knots. I have only recently seen some Piper twins being fitted with after market winglet mods, but again these are cabin class airplanes. Winglets won't make a hoot of difference for the single engine, non cabin class birds.



"When a man runs on railroads over half of his lifetime he is fit for nothing else-and at times he don't know that."
User currently offlineMir From United States of America, joined Jan 2004, 21571 posts, RR: 55
Reply 6, posted (6 years 6 months 3 weeks 3 days 2 hours ago) and read 4190 times:



Quoting 57AZ (Reply 5):
Winglets won't make a hoot of difference for the single engine, non cabin class birds.

They do look cool though. I like the way that I can look out the side window of a DA42 and almost imagine that I'm flying an MD-11.  Smile

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offline57AZ From United States of America, joined Nov 2004, 2550 posts, RR: 2
Reply 7, posted (6 years 6 months 3 weeks 2 days 15 hours ago) and read 4133 times:



Quoting Mir (Reply 6):
They do look cool though

That's true-our 414A was one of the first to receive the winglet mods. IIRC, the mods did add slightly to the total wingspan by about four feet. Winglet mods are also expensive for older birds-something like $60k ballpark.



"When a man runs on railroads over half of his lifetime he is fit for nothing else-and at times he don't know that."
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 8, posted (6 years 6 months 3 weeks 2 days 13 hours ago) and read 4105 times:



Quoting Pilotpip (Reply 4):

Quoting Tdscanuck (Reply 3):
Swept wings only stall outboard if you've screwed up your washout. All of today's swept-wing commercial airliners stall at the root.

Interesting. I've never heard that. Then again, the PLI, shaker and pusher should help prevent any of the above from happening.

The shaker is electronically simulating what used to happen on real fly-by-wire (direct cable linkage) aircraft...vortex shedding from the wing root would impinge on the elevators and shake the control column.

A tip stall is very dangerous because you lose aileron authority. If you look at a modern large commercial airliner wing you'll see fairly significant twist...the angle of attack is higher at the root. This has a double benefit; it prevents tip stalls, and it moves the wing loading inboard which is structurally more efficient.

Tom.


User currently offlineFredT From United Kingdom, joined Feb 2002, 2185 posts, RR: 26
Reply 9, posted (6 years 6 months 3 weeks 2 days 12 hours ago) and read 4099 times:



Quoting 57AZ (Reply 5):
Winglets won't make a hoot of difference for the single engine, non cabin class birds.

Thank you for pointing out an inaccuracy in my previoys post. I should have written "spam cans" when I wrote "GA aircraft". GA is a lot bigger than the SEPs I had in mind when typing.  Smile

Quoting Tdscanuck (Reply 8):
A tip stall is very dangerous because you lose aileron authority.

Not to mention that the tips are aft of the center of the wing lift, meaning a tip stall can give a nose up tendency... ouch!



I thought I was doing good trying to avoid those airport hotels... and look at me now.
User currently offline57AZ From United States of America, joined Nov 2004, 2550 posts, RR: 2
Reply 10, posted (6 years 6 months 3 weeks 2 days 10 hours ago) and read 4074 times:



Quoting FredT (Reply 9):
GA is a lot bigger than the SEPs I had in mind when typing.

Yes. GA encompasses everything from the single engine two/four seaters up to 747s operated under Part 91.



"When a man runs on railroads over half of his lifetime he is fit for nothing else-and at times he don't know that."
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