Using speed brakes on a320.
 

I like to point out that I am just getting started out on the a320, and just looking for some insight on usage of speed breaks.
I read somewhere that they should not be used in managed descent, but only in open descent?
Not sure if this is true, but i would like to understand why, if it is.

And lastly, any other times I shouldn't use them? I read they should be used only up till flap 3, correct?
Also(silly ques), does the same concept of using them apply to the 319, 321 as well?

Thanks n advance!

May I suggest the following regarding use of the speed brake and high speed descents.

Above 315kts they can take quite a while (20 sec from memory). If you travelling faster than 320 kts, I strongly suggest you control the deflection commensurate with AP pitch to avoid an Overspeed. Too fast and the 'G' pitch authority may not be enough.

You can expect "More Drag" message scratchpad message and also on the PFD if aircraft is experiencing overspeed conditions for speed constained waypoint, speed limit or approach decel. Or experiencing over altitude conditions for these POIs. Extending speed brake in managed mode is not a bad idea. Who is your supplier for FMC/FMS?

On this subject, can anyone explain why if on autopilot (and therefore only half speed brake deployed), VLS increases further (not by a lot) when you move the s/b handle from half to full. I seriously hope there's not an easy answer to this! :O

Superpilot - I haven't seen this behaviour on A320...On A319/321 it does it because that is the speedbrake extending further!

Flighttime -

Watch your speedbrake use on the 321 - It is inhibited in Conf 3/Full and also leaves you little margin when heavy and clean.

Cough, now that you mention the A319/A321, I'm also in doubt but I last flew those types 18 months ago, so my observation most likely stems from flying A320s exclusively over the last 6 months. Can I ask you to watch out for it next time? (I'm talking about a VLS increase of around 2-4 kts). I'm currently on my winter break so cannot check it out soon! If I'm not hallucinating and it does indeed happen, my hunch is it's a bit of instant insurance incase A/P trips?

Can't say that I've noticed that either. I'll see if I can remember to look for it on my next trip.

Superpilot, a lot of pilots mistake movement of VLS because it is actually Alpha Prot and Alpha max moving on the tape and the size of the margin between VLS and Alpha Prot changing.This creates an optical illusion. I had it proved to me on a recent sim. Alpha Prot and Alpha Max are dynamic whereas VLS is based upon FMS weight data and the weight will not be changing rapidly.
Can anybody explain the slight roll that is produced if the speedbrakes are extended and Flap 2 is selected? The Fcom gives the following but what causes it?

"When the speed brakes are deployed, extending the flaps beyond FLAPS 1 may induce a slight roll movement, and in calm conditions a small lateral control asymmetry may remain until disturbed by a control input or by an atmospheric disturbance."

SPEED BRAKES lever....................................................... ................................................AS RQRD
‐ If the flight crew uses the speed brakes to increase the rate of deceleration or to increase the
rate of descent, the VLS will increase as well:
•The flight crew should ensure that appropriate speed margin exists before the extension of
the speed brakes
•If the speed brakes are extended, the flight crew should ensure that appropriate speed
margin exists before the beginning of a turn.
This will avoid the activation of the Alpha-Floor protection.
Note: In clean configuration, the VLS with speed brakes fully extended may be higher than
green dot speed or VFE FLAP 1.

Is this MORE DRAG a french english thing? What about "Drag Required" or "Add Drag"?

Correct. This is because they are inhibited in the landing config. Thus if they are extended when the landing config is selected, they will auto-retract to meet the inhibition. When they do that, the aircraft nose will point at the fields below you to compensate for the sudden increase in lift. Descent rate will then increase significantly and potentially de-stabilise your approach.

It's not so much that the 320 is only limited to 50% of spoilers with the AP on, but you get the extra spoilers over the 319/321 and 320 with AP on. 50% of 320 spoilers are equivalent to what you get with the other mini-buses. Last ferry flight I did we decided to see how much you get and believe me it is impressive! Turned the AP off, selected 300kts in an open decent and full speed brakes… Was a pretty impressive decent anyhow!

I always assumed the 320 speed brake thing was due to the weight, but you guys are saying that the 321 works the same as the 319. Why is this the case. I've never flown a 321 so I'm just curious.

A320 Spoilers
 

Something slightly different I heard.


The reason for the difference of speed brake extension A320/21 is during testing it was found that during an emergency descent with max speedbrake on the A320 that the resulting pitch up moment exceeded the autopilot authority to correct it resulting in it going into a protection area (guessing alpha prot) and the autopilot disconnected. Thus the A320 has less speedbrake throw than the A321.


Could probably go dig up some paperwork to confirm it if anyone thinks its a tall tale

The Fcom gives the following for an A320:
The maximum speedbrake deflection in manual flight is:
40 ° for spoilers 3 and 4
20 ° for spoiler 2.
The maximum speedbrake deflection with the autopilot engaged is:
25 ° for spoilers 3 and 4
12.5 ° for spoiler 2.
The maximum speedbrake deflection achievable with the autopilot engaged is obtained by setting the speedbrake lever to the half way position. On setting the position of the speedbrake lever from half to full, no increase in speedbrake deflection will be achieved.

The A321 gives:
The maximum deflection for the spoilers 2, 3 and 4 is 25 °.

The problem with the A320 was inadvertant alpha floor protection engaging giving Toga thrust just when you were trying to descend.

On the 320 you can take out the autopilot, pull full speed brake then re-engage autopilot. It copes with it fine in normal conditions.

220 kts is a good speed in the A320 as unless you are high and heavy, you can apply half speed brake and the VLS will be around 210kts. Then you can select Flap 1 as you are below 230 kts, VLS will then drop and you can wind the speed back to 190kts and select Flap 2 if needed.

This enables you to go down and slow down at the same time whilst configuring for the approach.

The A319 speed brakes can be fully extended with the A/P engaged but the boards only move to the equivalent of half the deflection of the A320s.

Be careful of selecting full speed brake in the A320 with the A/P engaged as you may get caught out if the A/P disconnects.