ORDFan From United States of America, joined Jun 2007, 378 posts, RR: 0
Reply 6, posted (4 years 4 months 1 week 3 days ago) and read 20753 times:
Honestly, I've never been one to "ooh" or "aah" over the whole wingflex thing -- really, it's just form following function. I think ground effect, as well as the extra-long raked wingtip, may exaggerate the flex when the aircraft is on approach or departure, because from the looks of some of the air-to-air videos/photos that have been posted recently, there doesn't seem to be an inordinate amount of wingflex in-flight, especially when viewed relative to the A330, which is another slender-winged twin that displays a fair bit flex in some photos.
In this 2008 article, Jon Ostrower estimates about 10 feet of flex in-flight. Does anyone know if this has proven to be accurate? And if so, how does it compare to other widebody twins today (A330, 777, 767)?
vikkyvik From United States of America, joined Jul 2003, 10350 posts, RR: 26
Reply 11, posted (4 years 4 months 1 week 2 days 23 hours ago) and read 19567 times:
Quoting JBirdAV8r (Reply 8): If anything the wing flex should be greater in cruise flight, owing to higher speed and greater lift produced by the wing.
No matter what your speed, if you're in steady, level flight, the wing is going to be producing the same amount of lift. The lower speed is compensated for by a higher lift coefficient (read: higher AOA).
Quoting airbazar (Reply 7): I would think that not much wing flex, if any, takes place in stable flight. You need significant load to flex it like taking off, landing, and turning.
The weight of an airplane is a significant load! There's actually probably slightly less load during a climb, as the engines are providing a bit of the force countering gravity.
JBirdAV8r From United States of America, joined Jun 2001, 4491 posts, RR: 21
Reply 12, posted (4 years 4 months 1 week 2 days 23 hours ago) and read 19250 times:
Quoting Tristarsteve (Reply 10): How can you have greater lift in the cruise?
Then the aircraft would be climbing.
The plane is lighter in the cruise than at take off, so to fly level you must have less lift.
Guess I oversimplified it and made a boo-boo. Lift varies directly with speed, and increases with angle of attack (to a certain point), among other things. My point is that the wings will flex as they are producing lift. As you go faster, ceteris paribus, the wings produce more lift. Obviously in cruise, angle of attack is quite a bit lower than on takeoff; the net effect of lower alpha and greater velocity is just enough lift to maintain steady-state, level flight. Also you have the complicating factor of high-lift devices (flaps and slats) for takeoff and landing.
Being "lighter in the cruise than at take-off" has little to do with your situation. It's airspeed and angle of attack (and air density, viscosity, etc.) A lighter aircraft will need a smaller angle of attack, everything else equal, to maintain steady-state flight.
[Edited 2010-08-18 11:43:25]
Edit again: I can't seem to convey my thoughts in a correct manner today....
Quoting JBirdAV8r (Reply 12): Guess I oversimplified it. Lift varies directly with speed, and increases with angle of attack (to a certain point), among other things. My point is that the wings will flex as they are producing lift. As you go faster, ceteris paribus, the wings produce more lift. Obviously in cruise, angle of attack is quite a bit lower than on takeoff--meaning the wings produce more lift with less speed. Also you have the complicating factor of high-lift devices (flaps and slats) for takeoff and landing.
MadameConcorde From San Marino, joined Feb 2007, 10937 posts, RR: 37
Reply 14, posted (4 years 4 months 1 week 2 days 22 hours ago) and read 18418 times:
A very pretty wing and engine picture there!
Seeing that beautiful elegant aircraft doing a flyover at Farnborough was a real pleasure!
I certainly hope to be on board the first commercial flight with Captain Masami Tsukamoto and ANA.
He looks like a really nice man and I am sure it must be a lot of excitement for him flying his new aircraft.
There was a better way to fly it was called Concorde
BMI727 From United States of America, joined Feb 2009, 15836 posts, RR: 27
Reply 15, posted (4 years 4 months 1 week 2 days 22 hours ago) and read 18305 times:
Quoting JBirdAV8r (Reply 12): Lift varies directly with speed, and increases with angle of attack (to a certain point), among other things.
For the record, it isn't exactly directly with speed, but that is a fair assumption to make here for the purposes of simplification.
Quoting JBirdAV8r (Reply 12): Obviously in cruise, angle of attack is quite a bit lower than on takeoff; the net effect of lower alpha and greater velocity is just enough lift to maintain steady-state, level flight.
Furthermore, efficiency dictates that at cruise the aircraft have the lowest angle of attack possible. This is because induced drag varies with the lift coefficient which is determined by alpha.
Why do Aerospace Engineering students have to turn things in on time?
peterjohns From Germany, joined Jan 2009, 208 posts, RR: 2
Reply 24, posted (4 years 4 months 1 week 2 days 19 hours ago) and read 12918 times:
Quoting JBirdAV8r (Reply 12): My point is that the wings will flex as they are producing lift. As you go faster, ceteris paribus, the wings produce more lift.
I think you are mixing up some things.
The lift produced by the wings equals the weight of the aircraft. Always. In climb it increases a little (fractions) and vice versa in descend.
Now I´m talking Airbus/Boeing not Raptor F22.
If the lift would increase with the speed- the aircraft would climb. It doesn´t. Why? AoA, and trim through the stabilizer.
So, let us agree that the lift of any fixed aircraft wing is always the same than the weight of the aircraft.
The flex of the wing comes from the wingload. Complete different thing. The wingload usually maximizes just before touchdown at slowest speeds. (That´s where you will also encounter the max. wakes)
: I believe this is for the engine cowl and wing anti-ice. These areas get mighty hot.
: With the exception of gravity effects weighing down the wing in level flight, the flex would basically be about the same since the wing will produce
: Thats the first thing I noticed. That engine is HUGE!
: Whatever, you guys... UAL747 is right. It is in a turn. Look closely at the reflection of the Fuselage on the engine nacelle... There is sky between
: It doesn't reduce wingflex. However, without a point of reference behind you to show the aircraft really IS in a turn, a lower wing in a turn will ma
: Take off is not the limiting load condition on the wing. The greatest loads the wing will see will be during severe turbulance or an emergency contro
: I think logically, with the weight of the plane completely off the wing (in 90 deg bank, no elevator) there will be much less flex. If the wings are
: Well, I understand. Consider this though, that abnormal attitudes in turbulance/high winds or pulling out of a dive actually "add weight" to the plan
: All this talk of wing flex - or lack thereof - in the original poster's post and no one stopped to think for a moment that perhaps the photo is a resu
: This just isn't right. The wing will flex less because there is less force. The force is less because the wings are holding up a lighter plane. For s
: Yeah, it almost looks too far forward. Its uncomfortable to look at, as it looks fragile. Not sure why but it just does. These types of planes are de
: It doesn't bother me as I am sure Boeing has taken all needed precautions for it to be 100% safe, wind tunnel testing and all that. What would bug me
: Enough with the geek-speak!!! Let's just take in the beauty of that view!
: I think we all need to consider that it looks like the image is a wide angel image as well. I took a similar picture out the wing from about the same
: Did you get invited on board the B-787 on one of the test flights? If this is the case, I hope you will post some of your pictures.
: I thought that was what I just said? My use of the term "work" is wholly appropriate for this discussion, a decidedly non- physics/engineering topic.
: I second that. Did any one see the pic in Randy's blog with the 787 and the Model 40? Thats COOL. Dan in Jupiter
: The nacelle inlet lips are typically aluminum. Even though the air entering the inlet is hot (the duct leading to the lip is probably titanium), the
: I think it's Glacier Peak but you could be right. Either way, I agree it's looking north as the aircraft heads east
: That peak in the distance make me think the near peak may not be Mt Baker. A friend suggest the fore ground my be Mt. Adams or Hood. bikerthai
: I was referring to the peak in the distance (as I thought you were in your ogiginal post). Whatever it is, the picture's beautiful as is the airplane
: Awesome picture! I am falling more and more in love with this aircrat everytime I see it. Great shot.
: Not on one of the test flights, the plane was here doing hot weather testing in Yuma, and it was on the ground when I took it. Heres the link to the
: That peak in the foreground is neither Mt. Hood or Mt. Adams. My guess is it's the Wenatchee National Forest under the engine, looking north towards
: All depends on angle of attack and speed...the angle of bank isn't relevant. Thank you! That's driving me crazy. It *is* really far forward. You have
: Oh you got to go inside the plane! Fantastic! Nice picture gallery! I love the 787! Such a beautiful aircraft!
: I believe it is relevant. How much would the wings flex if the 787 were to be flying level, but inverted (if it were possible, of course)? You'd witn
: Depends on the angle of attack & speed. Angle of bank (including inverted) isn't relevant. See above. The above statement would be partly true *i
: Leave it to Airliners.net to totally hijack a thread to talk about techinical aspects.
: Dynamic loads experienced during severe turbulence, or the other upset conditions that I mentioned previously will cause wing loads to greatly exceed
: It's 2.5g limit, so 3.75g ultimate including the safety factor.
: It's a thread about wing flex...wasn't really any other way it could have gone. No, they won't. The reason severe turbulence and upset conditions cau