B737 NG winglets & fuel burn
I've been flying the B73NG with winglets for a while. We are still using non-winglet fuel burn calculations. I do not know why short haul a/c are fitted with winglets; is it fuel burn or takeoff/landing performance plus time to CRZ? I saw that Air France had Airbus's without winglets and was told that they were not necessary for short sectors.
Anyway, I have not noticed any fuel saving with winglets over the non-winglet expected fuel burn. So, what is their use on short-haul ops? If it allows better takeoff performance it might allow great assumed temp reductions, thus better engine maintenance. If it allows greater RTOW's then there is a benefit in payload; sector fuel saving does not seem to be the case. Does anyone know the real reason some airlines fit them; and does anyone know what sector length is necessary to see a fuel saving?