Welcome, Guest. Please login or register.
Did you miss your activation email?
October 24, 2014, 11:36:30 PM
Home Help Login Register      
News: LiveATC.net Flyers Released!  Please click here to download & print a copy and be sure to post at an airport near you!


+  LiveATC Discussion Forums
|-+  Air Traffic Monitoring
| |-+  Aviation Audio Clips (Moderators: dave, RonR)
| | |-+  UPS 2954 Flight Control Issues
« previous next »
Pages: [1] 2 Go Down Print
Author Topic: UPS 2954 Flight Control Issues  (Read 9017 times)
silagi
Jr. Member
**
Offline Offline

Posts: 67



« on: September 29, 2010, 08:00:59 PM »

UPS 2954 had some flight control problems while on approach to SJC this afternoon.  They were able to land without incident.
Logged
alltheway
Guest
« Reply #1 on: September 30, 2010, 07:04:24 AM »

According to flightaware it's a Airbus A300F4-600 (twin-jet) (H/A306/Q

They where having spoiler problems, like a while ago with a A320 where #4 spoiler element remained in the upright position. Might be frost or to much tailwind... undecided
Logged
svoynick
Full Member
***
Offline Offline

Posts: 109


« Reply #2 on: September 30, 2010, 02:25:45 PM »

This reminds me of the thread where we were discussing whether a controller can ever declare and emergency for a pilot.  Seems like once they roll the equipment and ask for souls and fuel, you can kinda read between the lines...

According to flightaware it's a Airbus A300F4-600 (twin-jet) (H/A306/Q

They where having spoiler problems, like a while ago with a A320 where #4 spoiler element remained in the upright position. Might be frost or to much tailwind... undecided
Was the tailwind comment a humorous one?  As long as you're flying, from the perspective of the airflow over the wing, there is never a "tailwind", only forward airflow measured as airspeed.
Logged
alltheway
Guest
« Reply #3 on: September 30, 2010, 04:35:27 PM »

Quote
Was the tailwind comment a humorous one?  As long as you're flying, from the perspective of the airflow over the wing, there is never a "tailwind", only forward airflow measured as airspeed.

That is now exactly what I am afraid about, when spoilers are active during a turn (roll) they disrupt the airflow to reduce lift on that side. When this disruptive airflow starts to rotate towards the backside of a spoiler (due to wingfoil) and lifts it up and into a locked position. So far only Airbus has had this and they have a exclusive wingshape (foil). So it has not (yet) been confirmed, but I am a litte afraid it would be possible. If this would be studied with a tailwind then I have no idea what will come out. (windtunnel vision)
« Last Edit: September 30, 2010, 04:42:03 PM by alltheway » Logged
mrusa
Newbie
*
Offline Offline

Posts: 1


« Reply #4 on: September 30, 2010, 07:15:04 PM »

Quote
Was the tailwind comment a humorous one?  As long as you're flying, from the perspective of the airflow over the wing, there is never a "tailwind", only forward airflow measured as airspeed.

That is now exactly what I am afraid about, when spoilers are active during a turn (roll) they disrupt the airflow to reduce lift on that side. When this disruptive airflow starts to rotate towards the backside of a spoiler (due to wingfoil) and lifts it up and into a locked position. So far only Airbus has had this and they have a exclusive wingshape (foil). So it has not (yet) been confirmed, but I am a litte afraid it would be possible. If this would be studied with a tailwind then I have no idea what will come out. (windtunnel vision)

I'M an A&P mechanic and I work on airbus aircraft ( and Boeing, Douglas, etc) what seems to be missunderstood here is that spoilers operate on 3000 psi hydraulic pressure. And on ALL aircraft the spoilers are designed to fail in the down
position. Without any hydraulic pressure they are locked in the down position. So no the wind will not push a spoiler up!For ground maintenance the mechanic has to override the lock to push the spoiler up. In these cases it had to have been A major failure of the spoiler servo(hydraulic or electrical). And for those of you worried about flying on a passenger
aircraft, please remember this..PASSENGER AIRCRAFT ARE DESIGNED SO THAT THEY WILL STILL FLY AND REMAIN
CONTROLLABLE EVEN IF ALL THE SPOILERS ARE DEPLOYED.
Logged
alltheway
Guest
« Reply #5 on: October 01, 2010, 07:16:56 AM »


PASSENGER AIRCRAFT ARE DESIGNED SO THAT THEY WILL STILL FLY AND REMAIN
CONTROLLABLE EVEN IF ALL THE SPOILERS ARE DEPLOYED.


Very true but as the story says there was a uncommanded roll, like landing with or without gear it should not happen, but very rare it does. I bless the PF for recognizing the problem immediately and acted accordingly, I would never be afraid to fly with a pilot like this one  cheesy

« Last Edit: October 01, 2010, 07:35:02 AM by alltheway » Logged
svoynick
Full Member
***
Offline Offline

Posts: 109


« Reply #6 on: October 01, 2010, 02:42:27 PM »

That is now exactly what I am afraid about, when spoilers are active during a turn (roll) they disrupt the airflow to reduce lift on that side. When this disruptive airflow starts to rotate towards the backside of a spoiler (due to wingfoil) and lifts it up and into a locked position. So far only Airbus has had this and they have a exclusive wingshape (foil). So it has not (yet) been confirmed, but I am a litte afraid it would be possible.
Can I ask where your information is coming from that this has been an issue with Airbus aircraft?  I agree with your description of how asymmetric spoiler deployment is used to provide/enhance rolling moments in some aircraft designs, but your assertion that the disrupted airflow can roll back and push a spoiler up doesn't sound right.  Can you reference any specific reports, examples, or technical data that describes this phenomenon, or are you just guessing?

If this would be studied with a tailwind then I have no idea what will come out. (windtunnel vision)
I really think you are misunderstanding what a "tailwind" means with respect to the airflow flowing over a wing.  An aircraft in flight - even in a "tailwind" - is still always moving forward through a mass of air, and the air is always flowing from the front to the back of the wing.  

For an aircraft in flight, a tailwind dows not mean that the airflow reverses and flows from the back toward the front of the wing; it only means that the overall mass of air is moving in generally the same direction as the aircraft, but regardless: the aircraft is still moving forward through that moving mass of air.  So in flight, aerodynamically, a tailwind doesn't make any difference in the airflow over the wing at all.

(This is all for an aircraft in flight.  In ground operations, i.e. taxiing, you can certainly have wind and airflow in any direction over the aircraft.)
« Last Edit: October 01, 2010, 02:48:21 PM by svoynick » Logged
alltheway
Guest
« Reply #7 on: October 01, 2010, 05:30:52 PM »

With a tail wind going in the same (or near same) direction of the airplane at 20-40 kts I assume the vortex (wake) has more difficulty leaving the wing. In normal flight this "backpressure" helps the airplane to move foreward, but when this UPS was descending they encountered an uncommanded roll due to spoiler problems. As you should know with descending you try not to speed up, rather slowing down a bit. Then how can an uncommanded roll start with nothing there but air?

Logged
svoynick
Full Member
***
Offline Offline

Posts: 109


« Reply #8 on: October 02, 2010, 03:11:54 AM »

With a tail wind going in the same (or near same) direction of the airplane at 20-40 kts I assume the vortex (wake) has more difficulty leaving the wing.
No, that's not a correct assumption.  The aircraft moves through an air mass at a given airspeed regardless of which way the air mass is moving relative to the ground, i.e. the "wind direction".   At a given airspeed, vortices act the same relative to the wing, regardless of wind direction over the ground.

In normal flight this "backpressure" helps the airplane to move foreward...
No.  Wing vortices are actually a source of drag, which impedes the aircraft from moving forward.  One of the purposes of winglets and tip-tanks is to reduce wingtip vortices, which likewise reduces drag and increases efficiency.

...but when this UPS was descending they encountered an uncommanded roll due to spoiler problems. As you should know with descending you try not to speed up, rather slowing down a bit. Then how can an uncommanded roll start with nothing there but air?
What I've been responding to are your comments that "this disruptive airflow starts to rotate towards the backside of a spoiler (due to wingfoil) and lifts it up and into a locked position", and also that a tailwind can have any effect at all on the performance or action of a spoiler.  Neither of these assertions are aerodynamically correct.
Logged
Fryy
Sr. Member
****
Offline Offline

Posts: 418



WWW
« Reply #9 on: October 02, 2010, 02:48:18 PM »

At 2:30 into the clip when the controller asks how the flight controls are now, they tell him they shut some systems down. So it could of been a problem with the hydraulic system or some other system. Doesn't sound like it was from anything outside of the airplane, tailwind, etc.
Logged

Volunteer KSUU feeder
http://d.liveatc.net/ksuu.m3u
alltheway
Guest
« Reply #10 on: October 02, 2010, 04:55:51 PM »

If it cannot be from the outside of the airplane it must be from the inside, could it be an over worked actuator or ...?

I forgot to mention that we do have a saying: Cannot is at the graveyard and will not next to it...
« Last Edit: October 02, 2010, 04:57:56 PM by alltheway » Logged
Hollis
Sr. Member
****
Offline Offline

Posts: 403


« Reply #11 on: October 02, 2010, 09:42:40 PM »

Just a FYI. Airflow over a wing can and does go forward in flight under certain conditions. Usually when close to stall speed or at a high Alpha.
I have some nice color footage of stall tests with a fully 'tuffted' wing which shows the air moving front to rear in cruise at 1.4 Vso, then as speed is slowly reduced, the airflow from the inboard trailing edge begins to go forward then progresses up to the leading edge and outboard until all wing lift is lost, as well as roll control. Technically, it's know as boundary layer separation. Simple recovery is to push the nose down and 'reattach' the air to the upper wing surface.

 
Logged
SASD209
Jr. Member
**
Offline Offline

Posts: 62



« Reply #12 on: October 03, 2010, 12:07:32 AM »

This reminds me of the thread where we were discussing whether a controller can ever declare and emergency for a pilot.  Seems like once they roll the equipment and ask for souls and fuel, you can kinda read between the lines...


 I do not want to re-open the debate, but I for one would like to  have the trucks standing by and not need them, rather than not have them there and need them. They are on duty anyways, may as well have them come out the the field and be more readily available. Some people are macho and think "nah, I don't need em, I got this under control" right up until the point an incident happens. I'm sorry, but a flight control issue can be very serious and you never know how it may develop. I'm glad this was much ado about nothing, professionally handled by the crew and controllers. Thanks for posting it!!

-SASD209
Logged
svoynick
Full Member
***
Offline Offline

Posts: 109


« Reply #13 on: October 03, 2010, 02:15:52 AM »

Just a FYI. Airflow over a wing can and does go forward in flight under certain conditions. Usually when close to stall speed or at a high Alpha.
I have some nice color footage of stall tests with a fully 'tuffted' wing which shows the air moving front to rear in cruise at 1.4 Vso, then as speed is slowly reduced, the airflow from the inboard trailing edge begins to go forward then progresses up to the leading edge and outboard until all wing lift is lost, as well as roll control. Technically, it's know as boundary layer separation.
Point taken - a valid (but narrow) exception to my statements earlier.  However, the purpose of my point was to respond to the assertion that a "tailwind" in normal flight somehow changes the direction or nature of airflow over the wing, related to that poster's speculation about a spoiler getting "locked" up.

I'm sorry, but a flight control issue can be very serious and you never know how it may develop. I'm glad this was much ado about nothing, professionally handled by the crew and controllers. Thanks for posting it!!
Yeah, listening to this, I got the same chilled feeling as I got listening to the Alaska 261 audio (Jan, 2000; dove into the water off Pt. Mugu, CA due to horizontal stabilizer actuator problem.)  First they reported a control problem, then they had thought all was OK and had it stabilized out.  That much of the sequence was eerily similar between these two.  Fortunately for the guys in UPS 2954, theirs stayed controllable, but boy, I just got a horrible feeling in my gut listening to it...

Alaska 261 audio in this thread: http://www.liveatc.net/forums/atcaviation-audio-clips/alaska-261/
Logged
alltheway
Guest
« Reply #14 on: October 03, 2010, 06:02:51 AM »

related to that poster's speculation about a spoiler getting "locked" up.

Wasn't speculation at all it happened...
Logged
Pages: [1] 2 Go Up Print 
« previous next »
Jump to:  


Login with username, password and session length

Powered by MySQL Powered by PHP Powered by SMF 1.1.20 | SMF © 2011, Simple Machines Valid XHTML 1.0! Valid CSS!