Capt.Fantastic From United States of America, joined Aug 1999, 649 posts, RR: 0 Posted (3 years 3 months 1 week 4 days 15 hours ago) and read 7140 times:
Have a look at this video clip. I have never seen a takeoff in such conditions - It is a 767 departing HKG in a typhoon I believe. Could someone kindly translate the description of this video, or at least give some more info -- Anyone know the airline? The crosswind must have been extremely strong, given aileron / spoiler displacement. wow!
swiftski From Australia, joined Dec 2006, 2701 posts, RR: 2 Reply 1, posted (3 years 3 months 1 week 4 days 15 hours ago) and read 7111 times:
Quoting Capt.Fantastic (Thread starter): The crosswind must have been extremely strong, given aileron / spoiler displacement.
There are inboard and outboard double-slotted fowler flaps. The ailerons are neutral for most of the clip, which actually suggests not very much crosswind.
FLY2HMO From , joined Dec 1969, posts, RR: Reply 2, posted (3 years 3 months 1 week 4 days 15 hours ago) and read 7059 times:
Damn that was rough. Didn't almost lift off until after the aiming points. Funny to see the spoilerons twitching so much.
Otherwise looked pretty standard to me, must have been a left crosswind hence the deflection on that wing, standard procedure for a plane in the ground is to "bank" into the wind.
Halophila From United States of America, joined Aug 2005, 623 posts, RR: 2 Reply 3, posted (3 years 3 months 1 week 4 days 15 hours ago) and read 7005 times:
I have to say that given the conditions, I would probably have asked to not fly that day at the gate. That looked horrendous. At the very least the airline would have had to have bought a new seat cover.
I remember the Singapore Airlines 747-400 accident in Taipei was taking off during a typhoon as well. I'm not saying that was involved in the accident, but wanted to say that its probably common operations.
MSYPI7185 From United States of America, joined Oct 2007, 699 posts, RR: 0 Reply 4, posted (3 years 3 months 1 week 4 days 12 hours ago) and read 6747 times:
Interesting video.
I do not think I would have wanted to be on that flight!! I thought they would never get off that runway, was making me nervous just watching the video.
As the old saying goes, if you have a long enough runway it will eventually fly.
DocLightning From United States of America, joined Nov 2005, 16831 posts, RR: 57 Reply 5, posted (3 years 3 months 1 week 4 days 11 hours ago) and read 6626 times:
Quoting FLY2HMO (Reply 2): Damn that was rough. Didn't almost lift off until after the aiming points. Funny to see the spoilerons twitching so much.
GFFgold From Indonesia, joined Feb 2007, 443 posts, RR: 0 Reply 6, posted (3 years 3 months 1 week 4 days 10 hours ago) and read 6507 times:
Looks a bit rough, however pilots who operate long-term in typhoon prone regions usually have lots of experience dealing with such conditions. HKG experiences a lot of typhoon weather in the course of a year and I guess people learn to deal with it - though when conditions are really bad the airport shuts down. Similarly, pilots in Northern Canada routinely deal with snow and ice that would terrify your average CX jockey and those who fly in tropical monsoon conditions are used to landing in conditions that might be considered marginal elsewhere.
motopolitico From United States of America, joined Dec 2005, 212 posts, RR: 0 Reply 7, posted (3 years 3 months 1 week 3 days 18 hours ago) and read 5732 times:
Was the pilot looking to actively kill lift until he had reached a certain groundspeed, so that the a/c wasn't forced off the ground prematurely by a gust? Is that the profile of a typhoon, gustiness? After rotation, it seems as though the control surfaces are oscillating wildly. Is this some form of PIO? How did the engines not get swamped? How did the a/c not glaze over into a sheet of ice as it climbed to altitude? That pilot had balls of solid rock.
spacecadet From United States of America, joined Sep 2001, 3255 posts, RR: 14 Reply 8, posted (3 years 3 months 1 week 3 days 18 hours ago) and read 5579 times:
A few years ago the 747 I was flying on from NRT-JFK took off at the tail end of a typhoon; it wasn't as bad as this but I know from that experience that typically the airports in typhoon-prone areas of the world only seem to close during the very worst of the storm. In this country you would never even think about taking off during a hurricane, but they do it in other parts of the world all the time. What's a little wind and rain?
I'm tired of being a wanna-be league bowler. I wanna be a league bowler!
YYZALA From Canada, joined Nov 2009, 152 posts, RR: 0 Reply 9, posted (3 years 3 months 1 week 3 days 17 hours ago) and read 5442 times:
Quoting spacecadet (Reply 8): In this country you would never even think about taking off during a hurricane, but they do it in other parts of the world all the time. What's a little wind and rain?
What a silly comment to make. Regardless of nationality, everyone wants to live. Pilots know the limitations of their aircraft and therefore will or will not take off based on those limitations. If all the performance values are in the clear, why not takeoff? Just because YOU don't deem it safe does not mean the flight is not safe.
P.S. The airline is Aeroflot. Has been posted and discussed many times.
BlatantEcho From United States of America, joined Sep 2000, 1870 posts, RR: 1 Reply 10, posted (3 years 3 months 1 week 3 days 17 hours ago) and read 5247 times:
JBirdAV8r From United States of America, joined Jun 2001, 4459 posts, RR: 22 Reply 11, posted (3 years 3 months 1 week 3 days 17 hours ago) and read 5159 times:
In addition to being used as speedbrakes and for lift dump on touchdown, spoilers are often used in conjunction with ailerons to roll the aircraft.
Next time you fly commercially, watch the wings as you taxi to the runway. As the crew checks the flight controls, you'll generally notice at least a few of the spoilers come up with the ailerons.
JBirdAV8r From United States of America, joined Jun 2001, 4459 posts, RR: 22 Reply 12, posted (3 years 3 months 1 week 3 days 17 hours ago) and read 5097 times:
Quoting Halophila (Reply 3): I have to say that given the conditions, I would probably have asked to not fly that day at the gate. That looked horrendous. At the very least the airline would have had to have bought a new seat cover.
I remember the Singapore Airlines 747-400 accident in Taipei was taking off during a typhoon as well. I'm not saying that was involved in the accident, but wanted to say that its probably common operations.
While typhoons and hurricanes sound terrifying in name, the bottom line is that they're still storm systems. Safe flights are made all the time around certain parts of these systems. The wind in that video may not have even exceeded 30kt...it's just very hard to tell in the video. Although I am intrigued by what seemed to be quite a long takeoff roll...but again, that doesn't mean anything negative in and of itself.
Typhoon conditions generally are not the "sole" reason for an aircraft accident. The SQ accident, IIRC, happened when the crew attempted takeoff on a closed runway. The typhoon was a contributing factor insofar as the rain was heavy and reduced visibility; still, the accident shouldn't have happened.
GimliGlider From Germany, joined Jun 2006, 90 posts, RR: 0 Reply 13, posted (3 years 3 months 1 week 3 days 17 hours ago) and read 5018 times:
Quoting motopolitico (Reply 7): Was the pilot looking to actively kill lift until he had reached a certain groundspeed, so that the a/c wasn't forced off the ground prematurely by a gust? Is that the profile of a typhoon, gustiness? After rotation, it seems as though the control surfaces are oscillating wildly. Is this some form of PIO? How did the engines not get swamped?
When you're on the ground in just about everything from a 172 to a 767, SOP (and good judgment) is to hold ailerons into the wind on takeoff. As you accelerate, you slowly let out the input until you have no deflection at rotation. This, as you said, effectively 'kills lift' on the windward side.
The control surface movement is likely an attempt to correct for wind and turbulence. PIO is overcompensation or overcorrection, and it doesn't look like that's happening here.
"You could attach that to your house and still go 0-60 in 5 seconds..."
HotelDJRomeo From Canada, joined Dec 2009, 159 posts, RR: 0 Reply 14, posted (3 years 3 months 1 week 3 days 16 hours ago) and read 4867 times:
Quoting swiftski (Reply 1): There are inboard and outboard double-slotted fowler flaps. The ailerons are neutral for most of the clip, which actually suggests not very much crosswind.
While flaps are partially extended for takeoff, the ailerons and in-flight spoliers are anything but neutral.
This graphic helps to illustrate the various control surfaces on a wing:
When an aircraft is on the ground and being hit with a crosswind, the upwind wing will generate more lift than the downwind wing. Obviously you don't want the aircraft to roll during takeoff (or during roll-out after a landing), so by turning the ailerons into the wind it works to counteract the imbalanced lift casued by the crosswind. When the aircraft is moving slowly you may start with the ailerons all the way over into the wind; as it accelerates (i.e. headwind component increases) the amount of crosswind correction required decreases.
In the video posted the in-flight spoilers and aileron on the left wing are up, so we're looking at the up-wind (left) wing.
(PS: Conversely if you have a quartering tail-wind, you turn the ailerons away from the wind)
avek00 From United States of America, joined Oct 2004, 4092 posts, RR: 18 Reply 15, posted (3 years 3 months 1 week 3 days 16 hours ago) and read 4828 times:
But for the lack of PTVs I thought the airline involved was SQ.
474218 From United States of America, joined Oct 2005, 6340 posts, RR: 10 Reply 16, posted (3 years 3 months 1 week 3 days 16 hours ago) and read 4819 times:
Quoting swiftski (Reply 1): The ailerons are neutral for most of the clip, which actually suggests not very much crosswind.
The left ailerons are in fact up.
Quoting swiftski (Reply 1): The ailerons are neutral for most of the clip, which actually suggests not very much crosswind.
The left ailerons are up from the start of the video.
Quoting FLY2HMO (Reply 2): Funny to see the spoilerons twitching so much.
Quoting JBirdAV8r (Reply 11): In addition to being used as speedbrakes and for lift dump on touchdown, spoilers are often used in conjunction with ailerons to roll the aircraft.
The ailerons on the left wing are up during the entire takeoff roll. When the flaps are extended the spoilers work in conjunction with the ailerons (up ailerons up spoilers/down ailerons down spoilers). At liftoff the ailerons and spoiler retract then modulate up and down through the remainder of the video. All the above indicate taking off in a very strong crosswind.
Zeke From Hong Kong, joined Dec 2006, 7727 posts, RR: 73 Reply 17, posted (3 years 3 months 1 week 3 days 16 hours ago) and read 4702 times:
Quoting Capt.Fantastic (Thread starter): Could someone kindly translate the description of this video, or at least give some more info
Basically it says that the airport was closed, and 11 aircraft were given the option at pilots discretion to attempt a takeoff, 9 out of the 11 aircraft took off, 2 returned to the gate.
Quoting Capt.Fantastic (Thread starter): The crosswind must have been extremely strong, given aileron / spoiler displacement. wow!
Yes, excessive, I would think it would have made a mess of the performance calculations.
Quoting swiftski (Reply 1): The ailerons are neutral for most of the clip, which actually suggests not very much crosswind.
No.
Quoting Halophila (Reply 3): I have to say that given the conditions, I would probably have asked to not fly that day at the gate.
Same, in fact our airline would have grounded all of our aircraft, diverted incoming aircraft, and delayed departures.
Quoting GFFgold (Reply 6): Looks a bit rough, however pilots who operate long-term in typhoon prone regions usually have lots of experience dealing with such conditions. HKG experiences a lot of typhoon weather in the course of a year and I guess people learn to deal with it - though when conditions are really bad the airport shuts down.
HKG based pilots do have a lot of exposure to the seasonal conditions in HKG, and are also well aware of the low level windshear that gets generated around the airport with any significant wind over the surrounding terrain.
Quoting GFFgold (Reply 6): Similarly, pilots in Northern Canada routinely deal with snow and ice that would terrify your average CX jockey and those who fly in tropical monsoon conditions are used to landing in conditions that might be considered marginal elsewhere.
Our minimas are the same for landing in snow or in heavy rain. CX pilots see their fair share of cold Wx in China, Japan, Europe, and North America.
Quoting GimliGlider (Reply 13): When you're on the ground in just about everything from a 172 to a 767, SOP (and good judgment) is to hold ailerons into the wind on takeoff. As you accelerate, you slowly let out the input until you have no deflection at rotation. This, as you said, effectively 'kills lift' on the windward side.
Reduces, but i think the larger issue is the impact on takeoff performance. Those spoilers being extended the way they are I would think would invalidate any RTOW calculation.
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Aaron747 From Japan, joined Aug 2003, 7656 posts, RR: 28 Reply 19, posted (3 years 3 months 1 week 3 days 16 hours ago) and read 4633 times:
Quoting swiftski (Reply 1): The ailerons are neutral for most of the clip, which actually suggests not very much crosswind.
Totally wrong. How can you say that? Even at rotation the ailerons still had around 5 degrees of deflection. And if there was minimal crosswind, why were such large control inputs needed immediately when airborne? Crazy.
Quoting Zeke (Reply 17):
Same, in fact our airline would have grounded all of our aircraft, diverted incoming aircraft, and delayed departures.
CX clearly has a commitment to safety with such measures. Obviously it's possible to depart safely in these conditions but is it advisable? No. Even with the 12,000 foot runways at VHHH, it's not worth the risk. With that kind of wind and driving rain, there are no guarantees for getting stopped on the runway easily no matter when in the roll the abort happens.
Quoting Zeke (Reply 17): and are also well aware of the low level windshear that gets generated around the airport with any significant wind over the surrounding terrain.
That would be the greatest concern of mine as well, particularly if low level and surface winds were out of the S/SW. The visibility is poor in the video but I'm assuming from the ramp lights that this is a 25R departure?
If you need someone to blame / throw a rock in the air / you'll hit someone guilty
JBirdAV8r From United States of America, joined Jun 2001, 4459 posts, RR: 22 Reply 21, posted (3 years 3 months 1 week 3 days 4 hours ago) and read 3911 times:
Quoting 474218 (Reply 16): The ailerons on the left wing are up during the entire takeoff roll. When the flaps are extended the spoilers work in conjunction with the ailerons (up ailerons up spoilers/down ailerons down spoilers). At liftoff the ailerons and spoiler retract then modulate up and down through the remainder of the video. All the above indicate taking off in a very strong crosswind.
...right, which is what I said...I just simplified it for the non-pilots/engineers...
"Down spoilers" is kind of a misnomer because most aircraft with spoilerons don't have a negative position. They just stay in the 0' position when the ailerons on their wing are deflected downward.
Interestingly in my experience spoilerons aren't dependent on flap position--obviously you may have a different experience on the 767. Generally at higher speeds they aren't needed to augment roll control either...
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