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A-330 ailerons



 
 
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  #1  
Old March 14th 05, 09:28 PM
M
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Posts: n/a
Default A-330 ailerons


I was sitting on a Northwest Airbus A-330 a few Sunday's ago at Tokyo
Narita airport waiting for everybody to board on the flight back to
Seattle, when I noticed something strange with the ailerons. Both
ailerons were at their full
downward deflection at about 30 degrees. Things like this can of
course never
happen in any light GA planes where the ailerons are mechanically
linked to
move in opposite directions. I have never seen that on any Boeing
planes
either. Knowing those airbus having flight by wire systems I assumed
that the
computers were just taking a hiatus when the galley was being loaded
and the
ailerons should straighten out once the engines are started.

I peeked out of the windows again as we lined up on the runway and
began the
takeoff roll. To my astonishment both sides of ailerons were still at
a
downward deflection at about 10 degrees. As we rumbled down the runway
I had
this strong urge to tell the flight attendents to check the ailerons.
Can you
say "flight control: free and correct" in the before take-off
checklist? Those
ailerons just plainly looked wrong to me. The big turkey finally
lifted off
the runway and it suddenly hit me: this bizarre behavior of the
ailerons was
actually a genius engineering feat by the nerds at Airbus!

It became obvious that the fly-by-wire computer actually uses the
independently
controlled ailerons to act as part of a full-span flap system. This
allows the
benefit of a full-span flap without having the drawback of a
traditional
full-span flap like the MU-2 (MU-2 has full-span flaps but it has no
room for
ailerons. It uses spoilers for roll axis control). By doing so Airbus
probably saves some weight in the main flap system which, in my wildest
un-scientific guess, reduces the fuel cost per-seat on my 4000nm trip
to
Seattle by maybe a dollar. I'm sure that's very important for the
airline bean
counters.

As the plane climbed out over Tokyo bay the ailerons returned to their
normal
position as the main flaps were retracted.

On our final approach to Seattle the main flaps were down to about 30
degrees
and those ailerons were down again at about 10 degrees. The weather
was CAVU
to 200 feet above the ground, and it was near zero visibility in fog at
the airport. The autopilot flew a fabulous category III ILS all the
way the
ground and the main gears landed very gentally. The pilot was in a
hurry to
derotate the nose down to the ground and the nosewheel hit really hard.
I
guess when you can't see a damn thing 30 feet in the air as the rear
end of
plane already on the runway, you want to get the nose down asap and
start
braking.

Ads
  #2  
Old March 14th 05, 10:21 PM
Roy Smith
external usenet poster
 
Posts: n/a
Default

M wrote:
I was sitting on a Northwest Airbus A-330 a few Sunday's ago at
Tokyo Narita airport waiting for everybody to board on the flight
back to Seattle, when I noticed something strange with the ailerons.
Both ailerons were at their full downward deflection at about 30
degrees.


I don't know the specifics of the A-330, but many modern (i.e. fly by
wire) jets use their control surfaces in all sorts of interesting ways
which would not be possible on a cable-pully-and-bellcrank system like
we've got in our spamcans.

On many jets, roll is controlled (as you observed) with a mix of
spoilers and ailerons, and both ailerons can move together to
effectively act as flaps.

  #3  
Old March 14th 05, 10:40 PM
M
external usenet poster
 
Posts: n/a
Default


I've seen 747 using both the ailerons and outboard spoilers for roll
control. However I've never seen the aileron-as-flap thing until I saw
it on the A-330. And I'm quite certain that B-737, 747, 757 and 767
don't do that. Nor do I think A-320 families do that either. I've
been on a A-340 once but I didn't pay attention to the control
services, it probably does it just like A-330. Never rode on a B777.

  #4  
Old March 14th 05, 10:55 PM
Stefan
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Default

M wrote:

ailerons to act as part of a full-span flap system.


Such control surfaces are called flaperons. Nothing new. You find them
on many aircraft, from gliders to military jets. The system does not
rely on fly by wire, e.g. on gliders it's realised mechanically.

Stefan
  #5  
Old March 15th 05, 08:02 AM
Brian Burger
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Default

On Mon, 14 Mar 2005, Stefan wrote:

M wrote:

ailerons to act as part of a full-span flap system.


Such control surfaces are called flaperons. Nothing new. You find them
on many aircraft, from gliders to military jets. The system does not
rely on fly by wire, e.g. on gliders it's realised mechanically.


Some of DeHavilland Canada's designs have/had them; I know the Twin Otter
does - it's interesting watching them land in the harbour here with the
entire trailing edge of the wing sagging! The Twin Otter is mechanical, of
course.

For real oddness, the F16 supposedly uses its elevators for roll control;
they can move together (pitch) or differentially (roll).

Brian
www.warbard.ca/avgas/
  #6  
Old March 15th 05, 08:46 AM
Jay Beckman
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Posts: n/a
Default

"Brian Burger" wrote in message
ia.tc.ca...
On Mon, 14 Mar 2005, Stefan wrote:

M wrote:

ailerons to act as part of a full-span flap system.


Such control surfaces are called flaperons. Nothing new. You find them
on many aircraft, from gliders to military jets. The system does not
rely on fly by wire, e.g. on gliders it's realised mechanically.


Some of DeHavilland Canada's designs have/had them; I know the Twin Otter
does - it's interesting watching them land in the harbour here with the
entire trailing edge of the wing sagging! The Twin Otter is mechanical, of
course.

For real oddness, the F16 supposedly uses its elevators for roll control;
they can move together (pitch) or differentially (roll).

Brian
www.warbard.ca/avgas/


As does the F15, F14 and, I belive, the F/A18 as well.

For additional "oddness", check out the A10: the ailerons function as speed
brakes by splitting and deploying both up and down. I've often wondered if
the amount of up/down is variable for roll control or if the amount of split
remains constant and the entire assembly pivots up and down as ailerons
normally do?

Jay B


  #7  
Old March 15th 05, 01:07 PM
private
external usenet poster
 
Posts: n/a
Default


snip
Some of DeHavilland Canada's designs have/had them; I know the Twin Otter
does - it's interesting watching them land in the harbour here with the
entire trailing edge of the wing sagging! The Twin Otter is mechanical, of
course.

snip

These are called drooping ailerons and were used (in a reportedly unreliable
design prone to asymmetric deployment caused by freezing of cable actuating
system) on the Noorduyn Norseman. Credit is usually given to Dick Hiscocks
and Fred Buller for the excellent design of the mechanical (reliable rod
actuated) drooping ailerons used on the DHC stol series that began with the
DHC-2 Beaver and grew into the single (and later twin) Otter as well as the
larger Buffalo and Caribou aircraft. These aircraft are legendary for their
stol capabilities due mainly to the use of drooped ailerons (and big
powerplants).

I believe that the Robertson stol kits for the C-337 and others also feature
modifications that cause the ailerons to droop with the application of
flaps.

Blue skies to all


  #8  
Old March 15th 05, 05:54 PM
Teranews
external usenet poster
 
Posts: n/a
Default

Correct. I flew a turbo 206 with the Robertson kit. It would droop the
ailerons 10 degrees with the first 15 degrees of flap. We regularly operated
in and out of a 500 foot strip in Southern Oregon for 14 years.
Al

"private" wrote in message
news:[email protected]

snip
Some of DeHavilland Canada's designs have/had them; I know the Twin Otter
does - it's interesting watching them land in the harbour here with the
entire trailing edge of the wing sagging! The Twin Otter is mechanical,
of
course.

snip

These are called drooping ailerons and were used (in a reportedly
unreliable
design prone to asymmetric deployment caused by freezing of cable
actuating
system) on the Noorduyn Norseman. Credit is usually given to Dick
Hiscocks
and Fred Buller for the excellent design of the mechanical (reliable rod
actuated) drooping ailerons used on the DHC stol series that began with
the
DHC-2 Beaver and grew into the single (and later twin) Otter as well as
the
larger Buffalo and Caribou aircraft. These aircraft are legendary for
their
stol capabilities due mainly to the use of drooped ailerons (and big
powerplants).

I believe that the Robertson stol kits for the C-337 and others also
feature
modifications that cause the ailerons to droop with the application of
flaps.

Blue skies to all




  #9  
Old March 15th 05, 07:10 PM
Gord Beaman
external usenet poster
 
Posts: n/a
Default

"M" wrote:


I was sitting on a Northwest Airbus A-330 a few Sunday's ago at Tokyo
Narita airport waiting for everybody to board on the flight back to
Seattle, when I noticed something strange with the ailerons. Both
ailerons were at their full
downward deflection at about 30 degrees. Things like this can of
course never
happen in any light GA planes where the ailerons are mechanically
linked to
move in opposite directions. I have never seen that on any Boeing
planes
either. Knowing those airbus having flight by wire systems I assumed
that the
computers were just taking a hiatus when the galley was being loaded
and the
ailerons should straighten out once the engines are started.

I peeked out of the windows again as we lined up on the runway and
began the
takeoff roll. To my astonishment both sides of ailerons were still at
a
downward deflection at about 10 degrees. As we rumbled down the runway
I had
this strong urge to tell the flight attendents to check the ailerons.
Can you
say "flight control: free and correct" in the before take-off
checklist? Those
ailerons just plainly looked wrong to me. The big turkey finally
lifted off
the runway and it suddenly hit me: this bizarre behavior of the
ailerons was
actually a genius engineering feat by the nerds at Airbus!

It became obvious that the fly-by-wire computer actually uses the
independently
controlled ailerons to act as part of a full-span flap system. This
allows the
benefit of a full-span flap without having the drawback of a
traditional
full-span flap like the MU-2 (MU-2 has full-span flaps but it has no
room for
ailerons. It uses spoilers for roll axis control). By doing so Airbus
probably saves some weight in the main flap system which, in my wildest
un-scientific guess, reduces the fuel cost per-seat on my 4000nm trip
to
Seattle by maybe a dollar. I'm sure that's very important for the
airline bean
counters.

As the plane climbed out over Tokyo bay the ailerons returned to their
normal
position as the main flaps were retracted.

On our final approach to Seattle the main flaps were down to about 30
degrees
and those ailerons were down again at about 10 degrees. The weather
was CAVU
to 200 feet above the ground, and it was near zero visibility in fog at
the airport. The autopilot flew a fabulous category III ILS all the
way the
ground and the main gears landed very gentally. The pilot was in a
hurry to
derotate the nose down to the ground and the nosewheel hit really hard.
I
guess when you can't see a damn thing 30 feet in the air as the rear
end of
plane already on the runway, you want to get the nose down asap and
start
braking.


What goes around comes around? in the mid fifties the RCAF
acquired an ASW aircraft called the Argus...it was a much
modified Bristol Britannia and had 'floating controls'. They were
free floating and were controlled by 'tabs' on their trailing
edges. When at rest the ailerons hung down (both of them!) at
about 45 degrees and when the 'gust locks' were on they both
reared up about the same. The elevators both hung down 30 0r 40
degrees when unlocked and were straight back when locked, the
rudder was straight back when locked and was 'where-ever it
damned well wanted' when unlocked...quite weird...got many tower
controllers (and airline pilots) in a knot.
--

-Gord.
(use gordon in email)
  #10  
Old March 15th 05, 07:24 PM
Roy Smith
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Posts: n/a
Default

Gord Beaman wrote:
What goes around comes around? in the mid fifties the RCAF
acquired an ASW aircraft called the Argus...it was a much
modified Bristol Britannia and had 'floating controls'. They were
free floating and were controlled by 'tabs' on their trailing
edges. When at rest the ailerons hung down (both of them!) at
about 45 degrees and when the 'gust locks' were on they both
reared up about the same. The elevators both hung down 30 0r 40
degrees when unlocked and were straight back when locked, the
rudder was straight back when locked and was 'where-ever it
damned well wanted' when unlocked...quite weird...got many tower
controllers (and airline pilots) in a knot.


Doesn't the DC-9 work this way too? I have a vague recollection of
talking to a DC-9 pilot who explained the system to me -- mechanical
interconnections to servo tabs, with the main surfaces floating free.

Or is my memory faulty?
 




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