Ailerons and spoilers question

B00056718

Ok. I'm very far from being an expert in aircraft control surfaces, so this might appear like a question of a four year old, but it bugs me for a while and I dont seem to be able to find a satisfying answer.

I usually try and book a seat behind or over the aircraft wings and enjoy watching the above in action.
However, I have noticed that when I was in older B737, on the approach, ailerons would do most of the work to stabilize the aircraft and only on very bumpy events you could see spoilers kicking in to assist. I don't mean deployed spoilers to help the descent, but working asymmetrically to keep the wings level.
However on 737-800 and A320, even on a reasonably calm approach, most times I can see spoilers doing all of the work, while ailerons are just sitting there pretty. Yet on the rare occasion I see ailerons leveling the plane.

So the question is - is this how the control systems are designed and the airplane just decides what surface to use, or is it something to do with the settings, the pilots enter?

Hope the above makes sense.

ZeroFourNiner

The ailerons would typically do most of the work to control the roll rate of the aircraft. They are located on the very end of the wing so they would create the greatest rolling moment about the centre of gravity of the aircraft.

The scenarios you mentioned where the spoilers come in to play typically occur during the landing phase in turbulent weather when the aircraft may be required to make sudden and sharp corrections to stay wings level.

In the landing phase the aircraft will be flying slow and it's flaps should be deployed. This makes it harder for the aircraft to develop rolling moments. As most of the lift will be produced further inboard due to the location of the flaps and there is a slower airflow over the control surfaces. This means the pilot has to work harder to roll the aircraft.

The spoilers may be activated on one side automatically based on the input of the pilot in to the aircrafts flight control system.

olive20

Was bored yesterday and went for a drive around the stands. How come the DHL A330s have no ailerons? Took fotos but blocked from posting here.

billy few mates

The 737 has a unit in the main wheel well called a Spoiler Mixer which takes an input from the aileron cable drive and adds an input to the flight spoilers on the wing of the upgoing aileron once the aileron raises above 10 Degrees (iirc) to augment the authority of the aileron for a given roll demand. It's a purely mechanical unit consisting of springs and cams.

The DHL A330s are actually DHL A300-600s and they do have ailerons, you just probably didn't notice them. If it was one of the older A300B4s you would have seen two sets of ailerons on the wing, a high speed and a low speed aileron, the -600 has a more advanced wing and only requires one set of conventional ailerons.

B00056718

Ok. Thanks for the answers. But in both it should be that the spoilers should only deploy after the aileron reaches its limit, but the pilot continues further with the controls input.
However, I often see that aileron isn't moving at all. All the work is being done by spoilers.

ZeroFourNiner

B00056718 wrote: »

Ok. Thanks for the answers. But in both it should be that the spoilers should only deploy after the aileron reaches its limit, but the pilot continues further with the controls input.
However, I often see that aileron isn't moving at all. All the work is being done by spoilers.

I've just watched a few videos of the wingview in the A320. The spoilers do appear to make small defletctions during high speed phases, with the ailerons appearing to deflect even less or not at all. This makes sense, aerodynamic loading at the wing tips at very high speed would put a lot of stress on the wing structure. The small amount of spoiler would decrease lift on on one side creating a rolling moment.

During the landing phase it looks to me like the ailerons droop with the flaps. (The ailerons would be doing the same job as the flaps when drooped) The ailerons do a lot of the work and the spoilers would only go up slightly when the aileron goes above the chord line of the flaps.

The Airbus FBW system is interesting to watch in action.

B00056718

Just watched this video http://youtu.be/KgIhWqvNGRc
And everything happens as you described. Also, plenty of aileron movement, along with some spoilers action.
However, was returning from Frnkfurt last Monday on Ryanair 737, and the aileron stayed solid, while spoilers kept working away.
Maybe I just need my eyesight checked.

ZeroFourNiner

Can't post links myself but watched a HD vid of a RYR 737 landing in stansted.

The aileron movement might be a bit more obvious in the videos and you can playback and watch the ailerons and spoilers seperately.

Aileron deflection would be very small and definitely difficult to spot as a pax don't be too hard on yourself!

olive20

Hi Billy
Pulled up to the DHL today and spoke to engineer doing something and he said no outboard ailerons on this Bus, uses spoilers instead. All the B4s are gone years, they had them. Big plane I taut it was a 330 but it's bigger it seems.

Alpha Romeo

olive20 wrote: »

Hi Billy
Pulled up to the DHL today and spoke to engineer doing something and he said no outboard ailerons on this Bus, uses spoilers instead. All the B4s are gone years, they had them. Big plane I taut it was a 330 but it's bigger it seems.

You'd know if it was an A330 by the winglets. If you are talking about the DHL in Dublin, it's not as big as an A330. An A330-300 wouldn't be far off a B777-200. Very big planes!

Tenger

olive20 wrote: »

Hi Billy
Pulled up to the DHL today ...............Big plane I taut it was a 330 but it's bigger it seems.

A310's have a little 'wing tip fence', similar to the A320 family (older models) while the A330 have the slightly angled 'winglet'

smurfjed

In the normal mode, the ailerons and spoilers 5 and 10 are locked out during high–speed flight; the flaperons and remaining spoilers provide sufficient roll control. During low speed flight, these panels augment roll control.

today just happened to be my flight control day:) I'm sure some of the 737/320 guys can explain the logic for those aircraft, but you can see from this text that it's quite normal for the ailerons to be locked out at higher speeds!

The A300 has FLAPERONS.

Bussywussy

going by memory on A330 Spoilers 2-6(Think 2-5 on 320) are for roll control along with the ailerons,the roll control has priority over the speedbrake function,the deflection of each spoiler reduces as flaps are lowered too.spoiler 1 will only deflect on ground.The outboard ailerons are locked at high speed flight above 190kts or so

B00056718

ZeroFourNiner wrote: »

Can't post links myself but watched a HD vid of a RYR 737 landing in stansted.

The aileron movement might be a bit more obvious in the videos and you can playback and watch the ailerons and spoilers seperately.

Aileron deflection would be very small and definitely difficult to spot as a pax don't be too hard on yourself!

A few answers here are starting to shed some light.
I'll lick the window next time for a better view

billy few mates

Hi Billy
Pulled up to the DHL today and spoke to engineer doing something and he said no outboard ailerons on this Bus, uses spoilers instead. All the B4s are gone years, they had them. Big plane I taut it was a 330 but it's bigger it seems.

The A300-600 does have ailerons, Airbus call them ASAs (All Speed Ailerons) they're not flaperons.
I mentioned the A300-B4 because the -600 is a derivative of it, in fact it's proper name is the A300B4-600, the old A300B4 had one set of low speed (inboard) ailerons and one set of high speed (outboard) ailerons . One of the differences between the B4 and the -600 is a completely redesigned and much lighter wing which did away with the need for the outboard (high speed ailerons) leaving only the 'inboard' ailerons which are called All Speed Ailerons. Your original post asked why the A300 did not have ailerons, I said it did, I should have said it didn't have outboard ailerons.

smurfjed

Billy Few Mates, my understanding of a Flaperon is this...

A flaperon is a type of aircraft control surface that combines aspects of both flaps and ailerons. In addition to controlling the roll or bank of an aircraft, as do conventional ailerons, both flaperons can be lowered together to function similarly to a dedicated set of flaps.

On the A310 (therefore I assume the A300-600 as its a common rating)

To improve the aerodynamic characteristics with slats extended, the ailerons droop down by approximately 7 degrees (Taken from smartcockpit A310 flight controls)

So wouldn't that make them Flaperons?