A320 S speed question

[Gary Lager]

OK - I stand corrected; it's been a few years since I least flew one, but the requirement to use S spd as a min with F1 only was then my company (large UK airbus operator) SOP.

[Dream Land]

Yes, as I mentioned, most operators operate the same way.

[AlR]

You're getting to caught up in this. The Aircraft will fly at Flaps 1 right up to Alpha Prot. The slower below S-speed, the less protection you have.

The FMGC displays S as the speed with config flaps 1 to give you a limit protection speed. You can go below it, right up to Alpha Prot, but you give up a lot of safety doing that. Not a big thing to go S minus 5 kts at config flaps 1, but why do it, what do you gain from that? Lot of variables there to consider, but balance them with the protection the FMGC is trying to provide you.

As for the pic TURNING BLUE, who's in charge there. You'll get your turn some day, respect the wishes of the guy or gal in the left seat(as well as the FMGC) and play it safe. Few knots isn't a big thing here. It's the concept of what you are trying to accomplish here.,

[wheresthecoffee]

From the FCOM;

S Speed
Minimum speed at which the slats may be retracted at takeoff.
In approach, used as a target speed when the aircraft is in CONF 1.
Represented by "S" on the PFD airspeed scale.
Equal to about 1.23 VS of clean configuration.


The FAC computes :
-The minimum and maximum speeds :
-VSW (stall warning)
-VLS
-VFE and VFE for the next configuration
-VLE
-VMO/MMO

The maneuvering speeds :
-Green Dot Speed
-S speed
-F speed

So, the way I read it, it isn’t the FMGC – it’s the FAC that computes and displays on the speedtape (and the speedtape speeds can (and often do) differ slightly from the FMGC Appr page) and thatGreen Dot, F and S are not protection speeds but target manoeuvring speeds.

Personally I cannot see the point of flying below the calculated manoeuvre speed.

[Dream Land]

Quite right, there is no point, I believe it's another case of a new airbus guy trying to reinvent the wheel (the captain doesen't understand the airplane), thinks it's in the interest of saving what I don't know, with the deck angle in that configuration I would bet it's cheaper to be at CON FIG 2 never mind the comfort level for pax and crew.

[Gnadenburg]

Originally Posted by Dream Land

Quite right, there is no point, I believe it's another case of a new airbus guy trying to reinvent the wheel (the captain doesen't understand the airplane), thinks it's in the interest of saving what I don't know, with the deck angle in that configuration I would bet it's cheaper to be at CON FIG 2 never mind the comfort level for pax and crew.

You should voice your concerns to Airbus, not new crew!

Rehashing, it is Airbus that is teaching it's Instructor Pilots to impart the acceptability of flying below S speed in Config 1.

Comfort? Not noticable.

Economy? About 20kg a minute cheaper, in a level segment @ Flap 1 a few knots below S speed, as opposed to Flap 2.

Safety? Normal Law with all protections. And you can fly on one engine, slats 1 only, no flap, above max landing weight, comfortably, with an approach speed of VLS Config Full plus 25KTS.

Let's not mix good professional debate with unfounded, personal sentiments.

[Eisenhower]

Well writen, Gnadenburg. Surelly makes clear who does not understand neither the things that are happening around, nor the protections given.

No one is trying to reinvent the wheel. It is just people who fly and UNDERSTAND the airplane that are talking over concepts and information that someone who flies the machine should have. This makes the difference between pilots and drivers.

If one does not understand what is going around, he/she should not show how stupid they are, right, Dream Land ?

[junior_man]

No problem to fly below S speed.

The only reason that the bus doesn't slow below S speed when speed is managed is so that you can retract the slats and still be managed. S speed is the min speed to retract flaps slats to 0 that is it.
Min maneuver speed for the existing weight and configuration is shown by VLS

As far as going to 2 and back to 1. Airbus discourages this and although it does lower the nose of the airplane it increases the fuel burn.

[Dream Land]

Eisenhower, your cpt may have misspoken by saying you can't do it, there is no operational limitation as mentioned in the first post, this is an simply an operating technique taught by Airbus for our airline.

[Ysatis]

well well, what has racism, ostracism or briticism to do with S speed Gnadenburg?

Originally Posted by Gnadenburg

... That Airbus pilots are uncomfortable flying a few knots below S speed, is testament of how much the French are dumming down this profession....

Just hope that all the well apreciated European and world wide engineers working for airbus along French colleagues do not share your inappropriate and degrading remark about French which is irrespectufull for the French nationals working for Airbus!

Thought the middle age was over, even in the farm land of Eden Valley.

[wheresthecoffee]

There are a lot of personal definitions coming out here.
S speed is the manoeuvring speed at F1 (not config 1 as per take off accel!).
Deliberately flying below manoeuvring speed is poor airmanship (even if VLS/ATHR is there as a back up to look after you!).
You may be planning a straight course, speed reduction but sometimes you have to unexpectedly manoeuvre..................................hence manoeuvre speed!
This is nothing to do with France or indeed the Airbus but is valid for every tye I have flown (more than a few!).

[Gnadenburg]

Originally Posted by wheresthecoffee

There are a lot of personal definitions coming out here..

And personal professional sentiments without qualification! Including yours!

Ad nauseum was my referrence to Airbus Instructor documentation that states an acceptability at flying below S speed with Config 1 selected, provided speed>VLS.

It has also been recently documented in the Airbus Flight Crew Training Manual.

So take it up with Airbus.

[Flying Fred]

Originally Posted by wheresthecoffee

There are a lot of personal definitions coming out here.
S speed is the manoeuvring speed at F1 (not config 1 as per take off accel!).

wheresthecoffee, you mention personal definitions and then (I think) you introduce one yourself
Where in FCOM does it talk about manoeuvre speeds? What is the reference? From your earlier post:-

Originally Posted by wheresthecoffee

From the FCOM;
S Speed
Minimum speed at which the slats may be retracted at takeoff.
In approach, used as a target speed when the aircraft is in CONF 1.
Represented by "S" on the PFD airspeed scale.
Equal to about 1.23 VS of clean configuration.

At S speed after takeoff, you retract the flaps so by definition it must be safe to fly clean at S speed. In fact, S speed corresponds pretty much to VLS clean.
S speed is the target speed in CONF 1 but I don’t recall Airbus using the term ‘manoeuvre speed’. I think that is Boeing terminology. I have not flown the Airbus family for four years now but that was one of the big differences going for Airbus to Boeing. On the A320, perfectly acceptable to go below the target speed with a minimum of VLS; on a Boeing, you want to go below manoeuvre speed, it’s the next stage of flap (although even my Boeing manual says you have full manoevre capability at 20kt below manoevre speed!)

Of course, all this may have changed since I left but I was always taught that VLS meant exactly that, lowest selectable speed for that particular config.

If you can find anything in official Airbus documentation that says otherwise, I stand to be corrected.

[wheresthecoffee]

FCOM 1.22.40 Flight Envelope

quote verbatim:

The maneuvering speeds :

* Green Dot Speed
* S speed
* F speed

unquote

When you take off with config 1, you don't have the same flap/slat configuration as you do when you select flap 1 on approach - maybe there lies the difference!

[Gnadenburg]

When your flaps lock on approach, are there any manouevre restrictions stated by Airbus? If your engine is lost in the same scenario, are there any manouevre restrictions? Remembering, Flaps locked means you will be flying below S speed without flap!

Incidently, single engine Flight Director restrictions on departure, are related directly to net climb gradients, and not an flight envelope limit.

Airbus " Flying below manuevre( sic ) speed for the configuration is acceptable, provided speed is greater than VLS ".

Mentioned in two Airbus manuals 1) Instructor Support 2) Flight Crew Training Manual. Both with reference to the approach scenario of ATC asking you to maintain speed a few knots below 'S'.

[pakeha-boy]

Gnad.....have you ever been at F1......REQUESTED.....F2,and as the flaps start to move,as seen on the ecam...gone back to F1.....this was an original procedure from Airbus.....most companys dont do it because of flap track wear........my point here is that will put the aircraft ia a better config at "s" at low speeds........

FOQA....is pilot friendly,we use it as a training tool,mostly for unstable apps ,but it cannot be used for enforcement action...not a big deal really,great training aid in groundschool....

[Gnadenburg]

Originally Posted by pakeha-boy

Gnad.....have you ever been at F1......REQUESTED.....F2,and as the flaps start to move,as seen on the ecam...gone back to F1.....this was an original procedure from Airbus.....most companys dont do it because of flap track wear........my point here is that will put the aircraft ia a better config at "s" at low speeds........
FOQA....is pilot friendly,we use it as a training tool,mostly for unstable apps ,but it cannot be used for enforcement action...not a big deal really,great training aid in groundschool....

Not familar with this procedure. Can you elaborate?

I have been at Flap One and > 200kts, Selected Flap Two, only to reselect Flap One. Not for your reasons but due an impending overspeed!

[Flying Fred]

Originally Posted by wheresthecoffee

FCOM 1.22.40 Flight Envelope
quote verbatim:
The maneuvering speeds :
* Green Dot Speed
* S speed
* F speed
unquote
When you take off with config 1, you don't have the same flap/slat configuration as you do when you select flap 1 on approach - maybe there lies the difference!

Thanks for the quote and I stand corrected. Hovever, I still stand by my original post in that you can retract to clean at S speed (which is defined as 1.23 Vstall clean) so the 1+F/1 debate isn't really relevant. VLS clean is the same as S speed.

I spent many years on the A320 from when it first came into service and did a manufacturers course all those years ago. We were definitely taught that coming back to VLS is OK. I think that, over the years, the original Airbus concept of flying anywhere between VLS and VMAX in whatever config you happen to be in has been diluted by successive generations of ex-Boeing pilots who have got used to doing it the other way. I must say that converting onto my current Boeing, I found it hard to understand why you couldn't come back to min manoeuvring speed (which, I would imagine, is the minimum speed you can manoeuvre at). As I said above, my Boeing manual says you have full manoeuve capability at 20kt below the manoeuvre speed.

What I am sure about is it is perfectly OK to go a few kt below S speed while at F1, unlike on my Boeing which does not allow it.

[wheresthecoffee]

This is one of those circular debates without end so I'll say my last piece.

I can fly an aircraft just above the stall and, as long as no 'upset' occurs, all will be well.

So, by the same token, I can fly an airbus below the manufacturer's manoeuvre speed (which they also refer to as the 'target' speed for that configuration) and all will be well.

However, are either of the above examples of good airmanship............I don't think so!

Vls is a protection that exists when the A'Thr is engaged.........nothing else.

Manoeuver speeds are designed to give a margin of safety for manoeuvre in certain configs (hence the boeing -20 kts thing.............that's the margin).

Flying below that speed reduces the margin and negates the point of it being there in the first place.

[pakeha-boy]

Gnad....I should have been more specific.......10-12 yrs ago we used the procedure.....Flaps 1 +f....used at geen dot on long finals so as not to use Flaps 2 ,because of pitch attitude and drag.......the procedure(for us) is not prohibited but not reccommended due to flap track wear.....

Impending overspeeds.as you suggested, requires you to reduce flap settings at any config that goes into the "red"(auto thrust,auto pilot off,speed brakes,etc etc)......that is an action,not a procedure.

We used this as procedure,and to this day works very well.I would totaly agree with wheresthecoffee,Airbus wants these A/C flown on profile,within the "laws" of the A/C for which it is designed......only problem with that is ,as humans we tend to cock-up profiles and flying these things as designed{guilty as charged) .....there are many safe and efficent ways of flying "outside of the box" ....PB