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Ailerons In Full Down Deflection On Taxi/TO Roll?  
User currently offlineEstorilM From United States of America, joined Jan 2009, 124 posts, RR: 0
Posted (4 years 10 months 3 days 3 hours ago) and read 5334 times:

Okay, so I've been around planes my whole life (like most of you reading this) and while some of you (pilots, mechanics, ground crew, etc) have seen it all, I think there's a wide assumption that if we fly a lot - we know what's "normal" and "safe" when it comes to aircraft. I've also flown some light AC with a friend who happens to be a flight instructor and would like to think I have a good and full understanding of control surfaces and their influence on a plane.


SO with that being said, I just about shit myself when I was taking off in a smaller aircraft a while ago (sorry, a similar thread about control surface movements spurred my renewed interest in this topic, which I never asked about - it was a while ago now, so I forget the model.) I want to say it was a United connector flight, possibly a CRJ200? Who knows.

In any event, I'm staring out at the wing at the gate and everything's dead as usual when the systems are off.. then we push back, and I don't see any control surface checks - even after startup and during taxi.

I'm starting to get a little nervous, as the aileron on my wing is in the MAX down deflection still! At this point we're cleared onto the active and he positions and holds. I'm doing that nervous "first time passenger" type thing where I look around to see if anyone else notices, with eyes probably bulging out of my face..

Then he starts his roll! I just stare out at the wing with a mental image of the plane doing a barrel roll into the ground  eyepopping 

Well - as his air speed increased, the aileron simple lifted into a neutral position with the rest of the wing trailing edge.

How is this even possible? What if the pilot needed some sort of roll stability control in the event of a sudden wind gust or crosswind? Does the computer system just wait till there is sufficient airflow over the wings before allowing certain surfaces to function in certain ways?

Now that I think about it, maybe it was an ERJ140/145?

19 replies: All unread, jump to last
 
User currently offlineDw747400 From United States of America, joined Aug 2001, 1257 posts, RR: 1
Reply 1, posted (4 years 10 months 3 days 3 hours ago) and read 5328 times:

Sounds like crosswind correction. Common on smaller aircraft, though I'm not sure of the procedure on the CRJ200.


CFI--Certfied Freakin Idiot
User currently offlineEstorilM From United States of America, joined Jan 2009, 124 posts, RR: 0
Reply 2, posted (4 years 10 months 3 days 2 hours ago) and read 5325 times:



Quoting Dw747400 (Reply 1):

I would agree, however it stayed at this deflection from the time I boarded the aircraft, till just before he rotated on takeoff.


User currently offlineAaron747 From Japan, joined Aug 2003, 8034 posts, RR: 26
Reply 3, posted (4 years 10 months 3 days 2 hours ago) and read 5320 times:



Quoting EstorilM (Reply 2):
I would agree, however it stayed at this deflection from the time I boarded the aircraft, till just before he rotated on takeoff.

Are you sure you were watching the aileron's position the entire time? It is highly unlikely that a professional crew would depart without ever running the flight controls portion of the taxi or before-takeoff checklist. They could have quickly run the controls when you weren't looking and returned them to an x/wind correction config.



If you need someone to blame / throw a rock in the air / you'll hit someone guilty
User currently offlineEstorilM From United States of America, joined Jan 2009, 124 posts, RR: 0
Reply 4, posted (4 years 10 months 3 days 2 hours ago) and read 5318 times:



Quoting Aaron747 (Reply 3):

I might have missed a flight control test while continuing to progressively tighten my seat belt as we got closer to to the runway, but trust me - my eyes didn't shift off that wing too much  Smile


User currently offlineVC10 From United Kingdom, joined Nov 2001, 1407 posts, RR: 16
Reply 5, posted (4 years 10 months 2 days 23 hours ago) and read 5270 times:

It sounds to me like an aircraft that has control surfaces that are controlled by tabs. With no airflow the control surface just hangs , but as the airflow increases then the tab becomes affective and moves the control to the selected position

The Bristol Britannia airliner was an example of this

littlevc 10


User currently offlineFredT From United Kingdom, joined Feb 2002, 2185 posts, RR: 26
Reply 6, posted (4 years 10 months 2 days 16 hours ago) and read 5196 times:

Would be hard to design free-floating tabbed ailerons though, due to upfloat of the ailerons due to pressure differences caused by the wing generating lift.


I thought I was doing good trying to avoid those airport hotels... and look at me now.
User currently offlineChrisjw From United States of America, joined Jan 2009, 123 posts, RR: 0
Reply 7, posted (4 years 10 months 2 days 14 hours ago) and read 5155 times:

Not sure what the procedures are for regional jets. But with small planes anytime the wheels are on the ground you use a crosswind correction (unless wind is absolutely dead, but still good technique to look at the windsock and correct).

Bank into a quartering-headwind. Dive away from a quartering-tailwind.

For T/O you simply slowly relax pressure on the controls as they become more effective with airspeed (or you could barrel roll like you mentioned). If done perfectly, you should have zero crosswind correction right as you rotate (or if the winds are really stiff, you keep some in to prevent winging-up).

I think I've seen some Cessna Citations do this when taxiing with a stiff crosswind at my airport.


User currently offlineVC10 From United Kingdom, joined Nov 2001, 1407 posts, RR: 16
Reply 8, posted (4 years 10 months 2 days 14 hours ago) and read 5144 times:



Quoting FredT (Reply 6):
Would be hard to design free-floating tabbed ailerons though, due to upfloat of the ailerons due to pressure differences caused by the wing generating lift.

Going back now some 40 odd years,but I seem to remember they had a darn big spring to counter that and the ailerons would go to neutral position around about 80kts.

It was not unheard of that other aircraft aircrew would warn the Brit crews that they had both ailerons hanging down

littlevc10


User currently offlinePilotpip From United States of America, joined Sep 2003, 3149 posts, RR: 11
Reply 9, posted (4 years 10 months 2 days 4 hours ago) and read 5018 times:

The 145 does not have aileron tabs. They're hydraulically actuated. Also no roll spoilers.

As others have indicated, it was likely crosswind correction. The reason it was taken out as you accelerated is simply because as airspeed increases control surfaces have more effectiveness so you need less input to get the desired effect. Crosswind correction is the same in the bigger aircraft as it is in smaller aircraft. If you don't make some sort of correction you'll have a difficult time holding center line as you accelerate.

I've never had crosswind correction while taxiing and in the case of the smaller Embraer aircraft it's not the ailerons that are the issue in winds but the elevator. It's cable actuated and in gusty winds it can be really hard to hold the yoke and keep it from slamming back and forth. One particularly windy day at ORD it took both of us holding the yoke with both hands as we took the runway to avoid having it slam back.



DMI
User currently offlineDashTrash From United States of America, joined Aug 2006, 1520 posts, RR: 2
Reply 10, posted (4 years 10 months 1 day 17 hours ago) and read 4925 times:

Are you sure you didn't confuse this flight with one where you were on a DC-9 / MD80?

User currently offlineEstorilM From United States of America, joined Jan 2009, 124 posts, RR: 0
Reply 11, posted (4 years 10 months 1 day 17 hours ago) and read 4914 times:

Definitely a tiny plane - I remember being able to look past the other rows (I believe it was 1-2 seating) and see the opposite wing.

That's interesting about the crosswind correction, and makes sense. I suppose it was just a coincidence that I missed the flight control check and the ailerons remained in the same position before/after the check as well.

Thanks guys =)


User currently offlineFredT From United Kingdom, joined Feb 2002, 2185 posts, RR: 26
Reply 12, posted (4 years 10 months 1 day 13 hours ago) and read 4833 times:



Quoting VC10 (Reply 8):
It was not unheard of that other aircraft aircrew would warn the Brit crews that they had both ailerons hanging down

Oh my, I stand corrected. They actually built it! Somewhere between lunacy and genius... love it! Big grin



I thought I was doing good trying to avoid those airport hotels... and look at me now.
User currently offlinePilotpip From United States of America, joined Sep 2003, 3149 posts, RR: 11
Reply 13, posted (4 years 10 months 1 day 13 hours ago) and read 4821 times:



Quoting EstorilM (Reply 11):
That's interesting about the crosswind correction, and makes sense. I suppose it was just a coincidence that I missed the flight control check and the ailerons remained in the same position before/after the check as well.

Don't worry, I can't see the control check either. Gotta trust the MFD  Smile
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We'll pull this up on the right side though because the control check is part of the FO flow. In our case we move the yoke and the captain does the rudder.

Oh, and I don't know why they'd have deflection during taxi.



DMI
User currently offlinePGNCS From United States of America, joined Apr 2007, 2821 posts, RR: 45
Reply 14, posted (4 years 10 months 1 day 12 hours ago) and read 4787 times:



Quoting DashTrash (Reply 10):
Are you sure you didn't confuse this flight with one where you were on a DC-9 / MD80?

My thoughts exactly.

Without more information I don't think you will ever know the answer to your question definitively (unless it was a DC-9 series aircraft or other plane with aileron control tabs), but obviously the crew did, in fact, know what they were doing as you made it with no aerobatics involved.


User currently offlinePart147 From Ireland, joined Dec 2008, 482 posts, RR: 0
Reply 15, posted (4 years 10 months 1 day 11 hours ago) and read 4774 times:

Perhaps you were looking at an aileron droop system?

http://www.tpub.com/content/aviation/14018/css/14018_23.htm
http://www.tpub.com/content/aviation/14018/css/14018_370.htm
http://www.freepatentsonline.com/5702072.pdf

They're used to increase lift during take off by 'dropping' both ailerons by a few degrees so they act like a smaller set of flaps.



It's better to ask a stupid question during training, rather than make a REALLY stupid mistake later on!
User currently offlineTWAL1011727 From United States of America, joined Mar 2006, 625 posts, RR: 0
Reply 16, posted (4 years 10 months 1 day 10 hours ago) and read 4769 times:



Quoting EstorilM (Thread starter):
I'm starting to get a little nervous, as the aileron on my wing is in the MAX down deflection still! At this point we're cleared onto the active and he positions and holds. I'm doing that nervous "first time passenger" type thing where I look around to see if anyone else notices, with eyes probably bulging out of my face..

If he did indeed have max deflection on the ailerons, he would also have a corresponding
spoiler deflection on the up aileron side (if so equipped.)
Was there a winglet on the wing tips....If not it probably was a DC9/MD80 series.

KD


User currently offlineMSPNWA From United States of America, joined Apr 2009, 1918 posts, RR: 2
Reply 17, posted (4 years 10 months 1 day 10 hours ago) and read 4762 times:

What I've read here has helped me understand a similar situation I saw on an HA 717 just a little while ago. During the entire taxi roll, the ailerons were in a deflected position (no wind problem either). I had never noticed that before, not even an a recent DC-9 flight. Nevertheless it was a little concerned as to why that was, but now I see why that could have been.

User currently offlinePilotpip From United States of America, joined Sep 2003, 3149 posts, RR: 11
Reply 18, posted (4 years 10 months 1 day 8 hours ago) and read 4739 times:



Quoting TWAL1011727 (Reply 16):
Was there a winglet on the wing tips....If not it probably was a DC9/MD80 series.

Most ERJ-145s don't have winglets. They also aren't equipped with roll spoilers.

Unless you really have the ailerons cranked in you won't see the spoilers deflected with a little crosswind correction in the 170 either. The FBW controls them.



DMI
User currently offlineSluaviator From United States of America, joined Aug 2004, 357 posts, RR: 3
Reply 19, posted (4 years 10 months 1 day 8 hours ago) and read 4729 times:



Quoting Dw747400 (Reply 1):
Sounds like crosswind correction. Common on smaller aircraft, though I'm not sure of the procedure on the CRJ200.

Its the same as any other plane. The only difference from the CRJ and a piston popper is we don't want to lift the mains on one side off the ground before the other.



What do I know? I just fly 'em.......
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