777 vibration on take off?
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From: Europe
777 vibration on take off?
Last week as a pax, just after rotation , the a/c nose was raised on take off then followed by strong vibrations for 4-5 seconds . Climb angle remained constant. Did not think much of it , but the same occurred on the return leg ( different crew, diff tail number but same airline )
Occasionally you do have this buffet but not as strong and not as long as these 2 times. Are certain 777 models known to have this ? or is this a new "flex take off" procedure ? or this particular airline training ?
Just curious .
On both cases runway length was not an issue , nor was obstacle to clear or temperature ( One of the legs was out of SIN early morning)
On all aircraft I do fly myself, I ( and was trained to) slightly lower the nose after rotation to gain a few knots just to avoid this. Or is the margin between buffet and actual stall so big on the 777 wing that this is a non-issue ?
Occasionally you do have this buffet but not as strong and not as long as these 2 times. Are certain 777 models known to have this ? or is this a new "flex take off" procedure ? or this particular airline training ?
Just curious .
On both cases runway length was not an issue , nor was obstacle to clear or temperature ( One of the legs was out of SIN early morning)
On all aircraft I do fly myself, I ( and was trained to) slightly lower the nose after rotation to gain a few knots just to avoid this. Or is the margin between buffet and actual stall so big on the 777 wing that this is a non-issue ?
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From: GPS L INVALID
Buffet after rotation should never be felt on any modern transport aircraft, out of curiousity - where along the fuselage did you sit? I'm thinking you felt the wheels rotate for a brief amount of time until they were stopped...
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From: The Winchester
"777 pre-stall buffet on take off" 
Before the newspapers get hold of this I'd very much suggest it wasn't any such thing.
I'd very politely and very much suggest
it's nothing aerodynamic at all and much much much much more likely to be nose wheel "shimmy" (a wobble/vibration as the wheel(s) spin downs) or something else gear/tyre related.
It's not that uncommon on many types, even the biggies, and yes, you do get it sometimes on the 777. If it happens it will be much more pronounced at higher rotation speeds.
Before the newspapers get hold of this I'd very much suggest it wasn't any such thing.
I'd very politely and very much suggest
it's nothing aerodynamic at all and much much much much more likely to be nose wheel "shimmy" (a wobble/vibration as the wheel(s) spin downs) or something else gear/tyre related.It's not that uncommon on many types, even the biggies, and yes, you do get it sometimes on the 777. If it happens it will be much more pronounced at higher rotation speeds.
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From: The Winchester
Unlikely that this situation happened though.
the same occurred on the return leg
....So I'll very much stick with the noise/rumble being shimmy or of similar origin.....
(Edit to add: A couple of points:
The OP mentions SIN. Without wishing to offend the locals 02C/20C at SIN isn't the smoothest runway in the world and it can certainly give the nose gear a good work out at higher speeds, and often makes for a noisy first few seconds after liftoff
Secondly many operators use or are moving to the use of "improved climb" for take-off performance, which may well mean increased ground speeds before rotate than under previous methods. That in turn may well lead to an increase in gear noise levels during retraction).
Last edited by wiggy; 19th February 2016 at 08:54.
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From: Europe
Hey, I was not fishing for sensationalism! Nose wheel shimmy could indeed explain it. Did not think of that possibility . I was seating up front in C, well before the wings so indeed that could be it.
The vibrations were quite strong and really feeling like buffet, so that was what came up to my mind first since the angle of climb after rotation was steep.
The vibrations were quite strong and really feeling like buffet, so that was what came up to my mind first since the angle of climb after rotation was steep.
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From: The Winchester
Hey, I was not fishing for sensationalism!
Anyhow hopefully we've got to the bottom of it all.
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From: Europe
Yes I realized that already and wanted to remove the words "pre stall buffet by :' vibrations " on the header but apparently once posted you cannot edit it it. Only the Mods can , so if one read this , you can do it for me .Thanks
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From: what U.S. calls ´old Europe´
Probably more a poorly balanced main wheel tire, than nose wheel shimmy.
Had it on two following legs on a Qantas Jumbo (out of FRA, out of SIN). You could see the galleys/toilets above the wheel wells moving in resonance... And it clearly matched the landing gear retraction cycle, which includes braking the wheels at a certain pont, when all the vibration suddenly stopped. Slight vibration could be felt during take-off and landing run at higher speed, but it clearly went extreme just with the wheels off the ground.
Also felt it (to a much lower extent) in the nose of a KLM 747 with a more gradual spindown of the wheels and end of the vibration (also including a fading of the vibartion frequency) after retraction.
Had it on two following legs on a Qantas Jumbo (out of FRA, out of SIN). You could see the galleys/toilets above the wheel wells moving in resonance... And it clearly matched the landing gear retraction cycle, which includes braking the wheels at a certain pont, when all the vibration suddenly stopped. Slight vibration could be felt during take-off and landing run at higher speed, but it clearly went extreme just with the wheels off the ground.
Also felt it (to a much lower extent) in the nose of a KLM 747 with a more gradual spindown of the wheels and end of the vibration (also including a fading of the vibartion frequency) after retraction.
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From: Australia
Vibes from the nose gear tyres contacting the snubbers during gear retraction can vary widely depending on tyres and/or snubber condition vs speed.
On retraction, main gear wheels are braked hydraulically, nose wheels are braked by two heat resistant pads rubbing against the tyres.
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From: Oxford, UK
ATC watcher, you can remove your posts yourself, or the entire thread that you have started, don't have to ask the mods to do it. I had to do it once to one of mine!
PS. Did you fly a pegasus glider? I did 3 diamonds in mine!
PS. Did you fly a pegasus glider? I did 3 diamonds in mine!
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From: PA
maui,
There are plenty of articles about the issue, and some fixes from Boeing. This issue was on the 777, especially the 300, but others have noted the same issue.
The auto gust modal suppression system on the tail causes a flutter that was so bad it was making crew and passengers sick in the back...
I believe it was new ANZ aircraft that were in the news...
Older thread on the issue...
B777-200 lateral oscillation in turbulence [Archive] - PPRuNe Forums
There are plenty of articles about the issue, and some fixes from Boeing. This issue was on the 777, especially the 300, but others have noted the same issue.
The auto gust modal suppression system on the tail causes a flutter that was so bad it was making crew and passengers sick in the back...
I believe it was new ANZ aircraft that were in the news...
Older thread on the issue...
B777-200 lateral oscillation in turbulence [Archive] - PPRuNe Forums
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From: UK
I'm not familiar with the 777 flavour, but slats tend to come before or with flaps, and I can't imagine performing a clean departure.
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From: australasia
Underfire.
OK I have heard of some hypersensitivity to some minor gust suppression induced oscillation. But I do believe you referred to "tail flutter", which is an entirely different kettle of fish.
Still haven't heard of "tail flutter"
M
OK I have heard of some hypersensitivity to some minor gust suppression induced oscillation. But I do believe you referred to "tail flutter", which is an entirely different kettle of fish.
Still haven't heard of "tail flutter"
M
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From: The Winchester
maui
Yep likewise.
There were stories from some down the back that the 777 did something "odd" in the cruise that made them feel ill ("hypersensitive"). I believe that may well have been blamed on gust suppression, but I've never heard of or experienced it causing anything like the symptoms described by the OP.
LlamaFarmer
Correct.
OK I have heard of some hypersensitivity to some minor gust suppression induced oscillation.
There were stories from some down the back that the 777 did something "odd" in the cruise that made them feel ill ("hypersensitive"). I believe that may well have been blamed on gust suppression, but I've never heard of or experienced it causing anything like the symptoms described by the OP.
LlamaFarmer
Correct.
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From: england
Although I don't think it's relevant to this situation, I think the auto slats extend the slats from the mid position (which they'd be at with take off flap settings) to the fully extended position if an impending stall is detected
