JaggySnake From United Kingdom, joined Oct 2012, 6 posts, RR: 0 Posted (8 months 1 week 5 days 2 hours ago) and read 3692 times:
Hi guys,
I've only just bought a membership to this place, yet like many of my classmates, I could probably credit my degree to the help of these forums!!
Anyway I'm on an internship (for my final year thesis) at an MRO doing a study of blended winglets, in particular, the installation of the Aviation Partners' product onto the 767-300ER.
I am interested to hear some views from current Flight Crew on any effects the installation of winglets has on the handling characteristics of the plane.
I have already spoken to a UA test pilot who was recently performing the post-mod test flight on one of their a/c and he suggested that there is little noticeable difference to the way the a/c handles following winglet installation. He did however admit that he wasn't the best person for me to ask as he does not exclusively fly the 767s.
I'm thinking that by adding these devices - they're really quite substantial on the 767-300 - there could be an increase to the dihedral effect of the wing adding some extra roll damping. As the effective aspect ratio is increased, the Mean Aerodynamic Chord is perhaps shifted towards the tips slightly? Combining that with the presumed aftwards shift of the longitudinal centre of gravity due to the winglet's weight, are there any performance implications upon take-off/landing which are at all noticeable?
I ask here as I have so far been unable to find any evidence to back-up these ideas.
I'm expecting you guys to come back and say that any differences are negligible, and I'm perhaps being optimistic in that I'm looking for anything that will add depth to my report, but any help on this issue would be greatly appreciated.
tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80 Reply 1, posted (8 months 1 week 4 days 10 hours ago) and read 3481 times:
Quoting JaggySnake (Thread starter): I'm expecting you guys to come back and say that any differences are negligible, and I'm perhaps being optimistic in that I'm looking for anything that will add depth to my report, but any help on this issue would be greatly appreciated.
One way to look at it is that, if the difference *weren't* negligable, the FAA et. al. would require either additional training or a new type rating. So far as I know, that hasn't happened.
DocLightning From United States of America, joined Nov 2005, 16932 posts, RR: 57 Reply 2, posted (8 months 1 week 4 days 10 hours ago) and read 3458 times:
Quoting tdscanuck (Reply 1): One way to look at it is that, if the difference *weren't* negligable, the FAA et. al. would require either additional training or a new type rating. So far as I know, that hasn't happened.
I thought that the winglets knocked a few Kt off the maximum allowable crosswind in a landing/takeoff.
tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80 Reply 3, posted (8 months 1 week 4 days 4 hours ago) and read 3394 times:
Quoting DocLightning (Reply 2): I thought that the winglets knocked a few Kt off the maximum allowable crosswind in a landing/takeoff.
If so, that's almost guaranteed to be due to available test data rather than an actual aerodynamic limitation...maximum allowable crosswind is just maximum demonstrated...the OEM's knock themselves out trying to find this highest crosswind you can while you've got an FAA-authorized test pilot onboard but you don't always get what you want. At some point, you give up being on wind watch because you've got a number that's good enough.
N243NW From United States of America, joined Jul 2003, 1502 posts, RR: 21 Reply 5, posted (8 months 1 week 3 days 4 hours ago) and read 3167 times:
Quoting DocLightning (Reply 2): I thought that the winglets knocked a few Kt off the maximum allowable crosswind in a landing/takeoff.
My airline actually queried Aviation Partners Boeing about this (why the 30kt value for the 757 and 29kt value for the 767 remain unchanged), and the response was that APB was able to better the non-winglet Boeing figures with the wingleted aircraft during flight test (remember, they're demonstrated values, not limits!). For this reason, APB considered the effects of winglets negligible on crosswind behavior.
TWA772LR From United States of America, joined Nov 2011, 783 posts, RR: 1 Reply 8, posted (8 months 5 days 11 hours ago) and read 2621 times:
What effect would winglets have on a crosswind landing/takeoff? Would they disrupt the aircraft in anyway? Didn't that used to be one of the theories of the CO DEN crash?
There's nothing like the smell of Jet-A in the morning. It smells like... VICTORY!!!
DocLightning From United States of America, joined Nov 2005, 16932 posts, RR: 57 Reply 9, posted (8 months 4 days 5 hours ago) and read 2336 times:
Quoting N243NW (Reply 5): My airline actually queried Aviation Partners Boeing about this (why the 30kt value for the 757 and 29kt value for the 767 remain unchanged), and the response was that APB was able to better the non-winglet Boeing figures with the wingleted aircraft during flight test (remember, they're demonstrated values, not limits!). For this reason, APB considered the effects of winglets negligible on crosswind behavior.
Couldn't Boeing use these results to alter the maximum allowable crosswind for the 767 type?
N243NW From United States of America, joined Jul 2003, 1502 posts, RR: 21 Reply 10, posted (8 months 4 days 1 hour ago) and read 2273 times:
Quoting DocLightning (Reply 9): Couldn't Boeing use these results to alter the maximum allowable crosswind for the 767 type?
There would likely be no real benefit, considering that these conditions are so rarely encountered. Also, Boeing probably wouldn't increase the aircraft's book values without doing the necessary testing themselves, for liability reasons.
tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80 Reply 11, posted (8 months 3 days 16 hours ago) and read 2200 times:
Quoting DocLightning (Reply 9): Couldn't Boeing use these results to alter the maximum allowable crosswind for the 767 type?
There is no maximum allowable crosswind, only max demonstrated. To count as "demonstrated" the OEM has to have done it with an FAA or AR pilot onboard and instrumentation to provide the data backup, and analysis to show that the with-winglet value is applicable to the without-winglet airplane. It's entirely possible that whatever APB did did not meet that threshold.
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