winglet penalties
 

Ok there are lots of good things about winglets but what about the penalties?

Weight is one, what are the other penalties?

My head hurts....:\

In some cases, the wingletted airplane cannot fit in the same hangar as the n0n-wingletted version.

u might loose something like 1 or 2 knots of x-wind capability.
and u might loose those winglets on narrow stands/taxiways. or they tangle up in other planes elevators.

they also take longer to slow down on approach

Could be a problem in a strong x-wind, if the winglets break up the airflow around the ailerons.

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

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.

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!

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

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.