F, S, green dot speeds
The Bumblebee
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The Airbus Instructor support handbook I have clearly says this in Intermediate approach section
If I am given a speed to fly by ATC whch happens to be below O F S speed I just querry ATC and ask them if it is ok to fly O F S speed. In most cases they have no problem.
Do not forget along with alpha floor we also have alpha lock in case you retract the flaps below S F speeds.
You may fly BELOW the maneuvering speed of the current configuration, provided you fly ABOVE VLS.
Do not forget along with alpha floor we also have alpha lock in case you retract the flaps below S F speeds.
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Rudderrudderrat - No, not "routinely" where on earth did you get that from?! The whole idea is that Airbus has provided us with a dynamic speed showing us exactly what you are saying, a margin that they have deemed "appropriate". So I am talking about possible and SAFE options that are available to you as a pilot.
The FCOM states -
"Minimum Selectable Speed (VLS):
The top of the amber strip along the speed scale indicates this speed. It indicates the lowest selectable speed providing an appropriate margin to the stall speed."
"Appropriate margin to the stall speed" - In other words - using the full range of speeds between Vmax and Vls is considered acceptable should you require or wish to do so. With auto thrust active you will not get below this speed anyway, not even when flying in V/S mode (this is another common misconception).
The FCOM states -
"Minimum Selectable Speed (VLS):
The top of the amber strip along the speed scale indicates this speed. It indicates the lowest selectable speed providing an appropriate margin to the stall speed."
"Appropriate margin to the stall speed" - In other words - using the full range of speeds between Vmax and Vls is considered acceptable should you require or wish to do so. With auto thrust active you will not get below this speed anyway, not even when flying in V/S mode (this is another common misconception).
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Thanks for the reference Desipilot.
Ah those valuable instructor support manuals that line pilots are not meant to access... I will try and get hold of a copy as it clearly has some useful info in there.
CP, just for clarification, I dont disagree with the things that you say, I am just enjoying a healthy debate and some useful stuff from fellow pilots.
As they say, there are many ways to skin a cat...
Ah those valuable instructor support manuals that line pilots are not meant to access... I will try and get hold of a copy as it clearly has some useful info in there.
CP, just for clarification, I dont disagree with the things that you say, I am just enjoying a healthy debate and some useful stuff from fellow pilots.
As they say, there are many ways to skin a cat...
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What is the exact definition on F speed (flap retraction speed), S speed (slat retraction speed) and VLS (lowest selectable speed)?
What is so "unprofessional" about flying above VLS but below F/S speeds, when I don't want to retract the slats/flaps?
And why doesn't the AT go below F/S speed when the speed is managed? Because it does not have any clue as to what you are about to do, retract the flaps or extend them. At S/F speed, you are usually safe to do both so it maintains it.
What is so "unprofessional" about flying above VLS but below F/S speeds, when I don't want to retract the slats/flaps?
And why doesn't the AT go below F/S speed when the speed is managed? Because it does not have any clue as to what you are about to do, retract the flaps or extend them. At S/F speed, you are usually safe to do both so it maintains it.
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All very good stuff. Had a few discussion points in after a sim check a while ago over exactly these sorts of points. My examiner was unable to justify why it was safe to fly from takeoff to above msa below F speed, but unsafe to fly from msa back to the threshold using the same speed.
As far as I understand it, not only is VLS not just more than 130% of stall speed, it's also dynamic in that it responds to wing loading, and therefore indirectly, to angle of bank.
As a slight aside we have one route where we tanker in to a high-ish intermediate airfield after a fairly short sector and aim to land about 500kg under max landing weight. In the summer watching the newbies try to slow the aircraft to configure, with the amber bit just under green dot which itself is fairly close to the amber ticks for the next flap setting, has my full attention, I assure you. Some even seem tempted to want to use the speed brakes as we start to turn base. However when you do get some flap out, the spread opens right out. So why are the trainers reluctant to let you use that part of the green tape if airbus says you can?
As far as I understand it, not only is VLS not just more than 130% of stall speed, it's also dynamic in that it responds to wing loading, and therefore indirectly, to angle of bank.
As a slight aside we have one route where we tanker in to a high-ish intermediate airfield after a fairly short sector and aim to land about 500kg under max landing weight. In the summer watching the newbies try to slow the aircraft to configure, with the amber bit just under green dot which itself is fairly close to the amber ticks for the next flap setting, has my full attention, I assure you. Some even seem tempted to want to use the speed brakes as we start to turn base. However when you do get some flap out, the spread opens right out. So why are the trainers reluctant to let you use that part of the green tape if airbus says you can?
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Hi Nubboy,
It's because on take off and GA, it's permissible to fly at 125% V stall (or whatever Airbus's factor is) but limit bank angle to 15 degs and you are not expected to pull speed brakes.
On the intermediate approach, you fly at a minimum of 130% V stall, bank up to 30 degs, and may pull speed brakes - hence the bigger margin.
Edit. @CP
But that's the problem - it is displaying the instantaneous margin for your present "g" which will change with bank angle and speed brake usage. I'm sure Airbus would be happy for us to fly around a few knots above VLS provided we didn't bank or pull any "g" - but speed brakes usage would be prohibited.
I think I'll stick with their present flaps / speed schedule.
My examiner was unable to justify why it was safe to fly from takeoff to above msa below F speed, but unsafe to fly from msa back to the threshold using the same speed.
On the intermediate approach, you fly at a minimum of 130% V stall, bank up to 30 degs, and may pull speed brakes - hence the bigger margin.
Edit. @CP
The whole idea is that Airbus has provided us with a dynamic speed showing us exactly what you are saying, a margin that they have deemed "appropriate"
I think I'll stick with their present flaps / speed schedule.
Last edited by rudderrudderrat; 30th Apr 2010 at 08:35. Reason: @ CP
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Ta for that.
However, since it's all computer generated, and the airbus knows what stage of flight you're at (eg SRS displayed, or perf activated), doesn't it compensate for that already?
My question is quite simple, to me anyway.
If you're in the green arc, even below F speed, and above VLS, and airbus say you can choose any speed down to VLS, why do the trainers give you a hard time when you do it?
However, since it's all computer generated, and the airbus knows what stage of flight you're at (eg SRS displayed, or perf activated), doesn't it compensate for that already?
My question is quite simple, to me anyway.
If you're in the green arc, even below F speed, and above VLS, and airbus say you can choose any speed down to VLS, why do the trainers give you a hard time when you do it?
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Remeber - SOPs may differ from company to company and as stated before, airbus does not prohibit you from doing it.
Enough on this subject from my side.
Keep it safe.
CP
Enough on this subject from my side.
Keep it safe.
CP
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What i find very amazing is that all qualified pilots and some instructors study the same books, have the same training, fly the same aircraft but all have different opinions for the exact same subject....
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I answered this before. All speeds are flyable upto VLS. You don't see this in manuals because it is not mentioned. However Airbus has clarified this in one of the conferences. The bank angle for angle of attack protection is reduced by 5degrees i.e. at GD it is 45 dgrees at VLS it is 40 degrees. If you are flying with auto pilot or manually with FD you won't exceed the bank.
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Rudderrudderrat. Green dot F and Especially S speed are nowhere near 130% VS. Please don't confuse these speeds with VLS, this question has nothing to do with 130% VS.
The question is completely justified, airbus have provided us with VLS which is the lowest selectable speed that provides a safe margin over VS.
The speed range between VLS and green dot, S or F speed can be something like 50 - 60 kts.
Every takeoff this margin is used, and the bus does bank more than 15 degrees. But on descent airlines prohibit flying i this range between VLS and green dot/S/F.
Now we can come-up with all kinds of imaginary scenarios for the descent/approach case with speedbrakes and bankangles, but I could do the same for the takeoff case. In takeoff this isn't planned nor is it in approach.
The instructor will give a hardtime anytime you don't fly in accordance with company procedures. But technically there is nothing wrong with flying somewhere in between VLS and F, S or O speed.
I have heard people complain about selecting a speed below F/S speed on takeoff (expedite climb for earlier turn in right direction) while the managed speed (same speed) was doing the same for the last 2 minutes or so...
The question is completely justified, airbus have provided us with VLS which is the lowest selectable speed that provides a safe margin over VS.
The speed range between VLS and green dot, S or F speed can be something like 50 - 60 kts.
Every takeoff this margin is used, and the bus does bank more than 15 degrees. But on descent airlines prohibit flying i this range between VLS and green dot/S/F.
Now we can come-up with all kinds of imaginary scenarios for the descent/approach case with speedbrakes and bankangles, but I could do the same for the takeoff case. In takeoff this isn't planned nor is it in approach.
The instructor will give a hardtime anytime you don't fly in accordance with company procedures. But technically there is nothing wrong with flying somewhere in between VLS and F, S or O speed.
I have heard people complain about selecting a speed below F/S speed on takeoff (expedite climb for earlier turn in right direction) while the managed speed (same speed) was doing the same for the last 2 minutes or so...
Last edited by 737Jock; 4th May 2013 at 16:08.
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flap speeds close to min managed speed (f, s, green dot)
As for turning below F or S speed, we regularly do it, and select below for an improved early climb. Places like BCN with their sharp left turn from RWY 25L at 450 AGL.
In the company I fly for (easyJet) we are not allowed to select below these speeds on approach. I know in BA from mates there that they do on approach.
As for limitations to this :
Obstacle clearance, noise abatement, or departure procedures may require an immediate turn after take-off. Provided FD commands are followed accurately, the flaps and slats may be retracted using the normal procedure as FD orders provide bank angle limits with respect to speed and configuration.
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Makes me giggle this...
If I want to fly 180kt at 56T on final then if you are in a 319 you need flap 2 (if your SOP isn't to go below 'S'). In a 320 or 318 you can fly it at flap 1...
Same wing, different certification assumptions (I'm lead to believe) hence different speeds....
If I want to fly 180kt at 56T on final then if you are in a 319 you need flap 2 (if your SOP isn't to go below 'S'). In a 320 or 318 you can fly it at flap 1...
Same wing, different certification assumptions (I'm lead to believe) hence different speeds....
Last edited by Cough; 5th May 2013 at 09:40.
In my airline, we cant go below green dot, F or S speed without selecting the next stage of flap, having said that we only mandated it around two years ago in company procedures. Before this guys would apply common sense and not normally go below it anyway.
As pilots we become so used to following everything to the letter of the law, when a law is not written we are often at sea wondering what to do, then someone messes up and....hey presto, there is a new procedure and, if your company is like mine, it takes a few weeks to find out why, then the rumours start.
I believe that Airbus has not specified a restriction on selecting a speed on approach below the manoeuvring speeds because they, unlike modern Airline management allowed some PIC discretion to fly the aircraft they way the PIC thinks it should be flow within the normal envelope.
Our reactive airline safety departments however remove all discretion, I sometimes wonder if I should be retitled pilot under command (of airline management) rather than pilot in command.
Whinge complete, you have the comms.
As pilots we become so used to following everything to the letter of the law, when a law is not written we are often at sea wondering what to do, then someone messes up and....hey presto, there is a new procedure and, if your company is like mine, it takes a few weeks to find out why, then the rumours start.
I believe that Airbus has not specified a restriction on selecting a speed on approach below the manoeuvring speeds because they, unlike modern Airline management allowed some PIC discretion to fly the aircraft they way the PIC thinks it should be flow within the normal envelope.
Our reactive airline safety departments however remove all discretion, I sometimes wonder if I should be retitled pilot under command (of airline management) rather than pilot in command.
Whinge complete, you have the comms.
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Perhaps the Flight Crew Training Manual might be of interest.
A320 FCTM NO-110 (Approach): "A speed below the manoeuvring speed of the present configuration may be selected provided it is above VLS. When the ATC speed constraint no longer applies, the pilot should push the FCU speed selector to resume managed speed."
The disadvantage, of course, is reduced margin in case of unexpected turbulence (wake vortex encounters aren't unheard of on approach...) or perhaps the next flap selection being made in the wrong direction!
In the after takeoff scenario, once in the clean configuration, you're only likely to want to deviate from the managed speed profile to achieve either best angle (green dot) or best rate (considerably faster than green dot speed). As Airbus put it: "Pilots should be aware that it is possible to select and fly a speed below green dot, but there would be no operational benefit in doing this" (A320 FCTM NO-060 - Climb).
A320 FCTM NO-110 (Approach): "A speed below the manoeuvring speed of the present configuration may be selected provided it is above VLS. When the ATC speed constraint no longer applies, the pilot should push the FCU speed selector to resume managed speed."
The disadvantage, of course, is reduced margin in case of unexpected turbulence (wake vortex encounters aren't unheard of on approach...) or perhaps the next flap selection being made in the wrong direction!
In the after takeoff scenario, once in the clean configuration, you're only likely to want to deviate from the managed speed profile to achieve either best angle (green dot) or best rate (considerably faster than green dot speed). As Airbus put it: "Pilots should be aware that it is possible to select and fly a speed below green dot, but there would be no operational benefit in doing this" (A320 FCTM NO-060 - Climb).
Last edited by Down...2 greens; 5th May 2013 at 11:46.
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http://www.pprune.org/tech-log/45800...ml#post6588270
Vls is only dynamic regarding change of config ie slat/flap/spoiler position.
Not loading. Discussed in the above link.
Vls is only dynamic regarding change of config ie slat/flap/spoiler position.
Not loading. Discussed in the above link.