EXPEDITE MODE

[dhardesthard]

Does anyone know why the A320 has an EXPEDITE mode and the A340 does not?

[thermostat]

It was a very stupid feature. I did not like to use it. During "expedite" the rate of climb would take off and the speed would drop below what I consider a safe amount. It was also removed from the 330.
Speed is very important when climbing at high altitudes. Rate of climb should not be for climb as it causes the speed to slowly fall and as a result the wing looses lift. It's airflow that produces lift so airspeed is important. I thought that AB would have replaced the expedite mode on the 320 also but..............

[dhardesthard]

So did the A340 and A330 originally have EXPEDITE modes?
I found it very helpful during an emergency descent (sim) if a transition to high speed was required.
I agree that it was not ideal for climb.

[iceman50]

It is not a "mode" on the A330/340 but a function that allows you to see distance required to make a level, if you expedite your climb by reducing towards green dot. It can be found on the Perf Climb page and you have to manually select the speed. You can also take out any climb derate to "expedite" the climb.

[Microburst2002]

In the 320 that mode is optional, so I guess it is optional in the bigger brothers too.

I think its best use is in during an emergency descent.
For expediting climb it is much better to select speed as required.

The FMGC will provide expedite predictions even if the mode is not available.

[Wingswinger]

EXP is useful on departure in the London TMA in order to climb over the stacks and obtain early direct routings thus making significant fuel savings. However, I wouldn't advocate its use above FL150 - it's better and safer to select SPEED above that.

[ReverseFlight]

The A320 Family Instructor Support manual (2001, p25) says this:

If ATC requires you to expedite through a given FL:
- select a lower speed on the FCU for best speed/alt trade off,
- or use a higher V/S.

The moral of the story is, avoid using the EXP p/b.

[safelife]

The A330/340 never had this function, as on the button's location they feature an ALT (hold) function with causes an immediate level of maintaining the given altitude.

[Microburst2002]

EXP CLB and gree dot

EXP CLB is a comfortable way to fly green dot, but I prefer to fly a few knots above green dot, so I prefer use of selected speed.

reverseflight:

I would like to see that document. Specially i would like to see what they say about V/S mode. In my airline they seem scared of it, they don't use it at all and almost panic when I do, but I don't know why.

[westhawk]

Specially i would like to see what they say about V/S mode. In my airline they seem scared of it, they don't use it at all and almost panic when I do, but I don't know why.

I've noticed an unreasonable fear of the V/S mode ever since that Pinnacle Airlines "four-one-oh-it dude" accident. Somehow that means nobody is safe unless they use one of the speed control modes. I guess keeping an eye on the IAS and making a little adjustment when needed is just too much to expect.

Anyway, maybe that explains it.

[HPbleed]

So how do yu fly CDA's in the London TMA without V/S?

[Cardinal]

Not sure why the hate for Exp Clb. A function that adjusts the climb speed to best lift/drag - Oh the horror. If it's that bumpy and you don't like it, pull speed and add a few knots more margin. Then there's always that sidestick thingy if speed should get too out of hand. Of course she will initially pitch aggressively, that's the point of "expediting" is it not, but the pitch moderates well as speed decays, and it doesn't show much if any tendency to undershoot.

It's an A320 - not a 727, and certainly not Concorde. It barely has a swept wing! It behaves quite nicely at low speeds, and for the sloppy technician who encounters them, has more protections in that realm than I care to list.

Signed - A proud Exped afficianado.

[ReverseFlight]

Specially i would like to see what they say about V/S mode.

To summarise, the manual recommends V/S for:
1. small level changes like 1000' for less thrust variation
2. fast climbs until it fails to achieve the target V/S, resulting either in deceleration to maintain V/S or pitch down to maintain VLS (which we all knew anyway).

It goes on to warn that, above FL300, if a/c speed has so decelerated, it takes a long time to re-accelerate. I have been reliably informed that, in such a case, select green dot plus say 20 kts, which I believe is in line with what Mb2002 and Cardinal were hinting towards.

[MD83FO]

id say one of the uses of this mode is that the load factor maneuvering target is increased to achieve a faster result, as the normal target for passenger comfort i believe is close to 1.1g's

[TopBunk]

First a rider .... I haven't flown the A320 family since 2005.

From my recollection, I found the Expedite function in climb very useful. It promptly applied CLB thrust, whereas not using it resulted in CLB thrust taking 5 or more seconds to be applied.

So, if asked by ATC to expedite, I would set the new cleared level and push EXPEDITE and then shortly after CLB thrust had been established, pull selected speed and adjust as appropriate, reducing towards Green Dot or whatever seemed appropriate - it's not rocket science folks.

[thermostat]

Emergency descents

I have always felt that emergency descents should be conducted at the turbulence penetration (Vb) speed. To come screaming down at high speed, not knowing what the weather or turbulence is like below, is pretty stupid. IMHO.

[charlie83]

Only been on the 320 for 3 years but have never used that button. Even in the sim during emergency descent after "turn pull, turn pull" etc etc I'm inclined to wind the speed up myself (after damage consideration) rather than let it just dive. Seems to work well enough.