winglet penalties
Join Date: Jan 2005
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The winglets increase the longitudal stability of the acf.
So you need more rudder input on eg xwind.
Less span dominated ground effect (less drag reduction) so you
might wan't to flare a tad sooner.. (in theory anyway)
M
So you need more rudder input on eg xwind.
Less span dominated ground effect (less drag reduction) so you
might wan't to flare a tad sooner.. (in theory anyway)
M
Join Date: Mar 1999
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As mentioned, the wingspan is usually longer. Continental had a rash of problems stemming from this when the 738W was introduced, from gate compatibility issues to actual taxi incidents involving A/C damage.
Join Date: May 2006
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Aero drag - increased frontal area?
Actually, this has been puzzling me - when retrofitted to sailplanes, winglets have typically shown a benefit at low airspeeds, higher angles of attack (predictably), but show a performance deficit in the higher end of the speed range, due, as I understand, to increased aero drag.
So,
1) why are they so prolifigate on airliners? (which don't generally fly too slowly)
2) Why are they getting so long - virgin blue's 737's are sporting very tall ones - where's the benefit in the huge height?
Cheers!
Actually, this has been puzzling me - when retrofitted to sailplanes, winglets have typically shown a benefit at low airspeeds, higher angles of attack (predictably), but show a performance deficit in the higher end of the speed range, due, as I understand, to increased aero drag.
So,
1) why are they so prolifigate on airliners? (which don't generally fly too slowly)
2) Why are they getting so long - virgin blue's 737's are sporting very tall ones - where's the benefit in the huge height?
Cheers!
Join Date: Jan 2006
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The greater wingspan 4’8” really does not pose a problem at the larger airports. The -800 utilize the same gates as B-757s B-767s which have significantly greater wingspans. The entry points and alleys leading to the gates also reflect the extra berth required to accommodate larger aircraft.
At smaller airports with tighter ramp areas greater vigilance is required no matter the type of aircraft to ensure proper clearances.
Marshallers have been known to lead a crew onto stand and oops there goes a wing tip into a service truck. The same on push back, when wing walkers are just not paying attention to what’s going on.
At smaller airports with tighter ramp areas greater vigilance is required no matter the type of aircraft to ensure proper clearances.
Marshallers have been known to lead a crew onto stand and oops there goes a wing tip into a service truck. The same on push back, when wing walkers are just not paying attention to what’s going on.
Join Date: Jun 2006
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Winglets are a way of increasing wing aspect ratio without actual wing span increases. Typically you get about 70% of the effective aspect ratio increase of the winglet length. As we know from our flight theory, induced drag is inversely dependent on aspect ratio. Therefore you will get a induced drag reduction using winglets.
As induced drag is highest at low speed, clean config, at cruise winglets have less benefit and when you design them you have to balance up the net reduction in induced drag at lower speeds with the increase in skin friction drag which is a function of wetted area and greatest at high speed. So there is no straightforward 'perfect' winglet solution and this is why they all look different (747-400 vs A310) or there are non at all (777)!
Then of course there are all the control issues raised by the other guys...
Hope that helps
As induced drag is highest at low speed, clean config, at cruise winglets have less benefit and when you design them you have to balance up the net reduction in induced drag at lower speeds with the increase in skin friction drag which is a function of wetted area and greatest at high speed. So there is no straightforward 'perfect' winglet solution and this is why they all look different (747-400 vs A310) or there are non at all (777)!
Then of course there are all the control issues raised by the other guys...
Hope that helps
Join Date: Apr 2006
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Just touching on that stand issue, Gatwick struggles at the best of times with domestic arrivals and departures, with stands in short supply and with high usage rate. I know that Ryanair with their winglets have reduced their ability to use at least one stand, which may one day end up with them having to coach passengers in from the park.
Small price to pay given the advantages of winglets but just one to add to the equation.
Small price to pay given the advantages of winglets but just one to add to the equation.
