Using v/s in initial climb
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Using v/s in initial climb
Hi,
Here is a situation:
Departure from LHR (or any other airport, but this is most extreme in London area), inital climb clearance acc. to SID is 4000' or 5000'. Next controller gives you climb to FL070, next controller to FL100, next controller to FL120 etc.
Do you stay in VNAV and let the airplane climb asap to assigned level and stay there or do you change over to V/S (500-1000 fpm) to "delay the climb" as to keep the climb gradient flatter and more continuous instead of step climb?
In my company, the skippers have mixed views, some want to stay in VNAV for traffice seperation purposes, others in V/S for passengers comfort and to keep the engines from constantly going from full climb power to almost idle while flying level at low level.
Input from controllers appreciated
Here is a situation:
Departure from LHR (or any other airport, but this is most extreme in London area), inital climb clearance acc. to SID is 4000' or 5000'. Next controller gives you climb to FL070, next controller to FL100, next controller to FL120 etc.
Do you stay in VNAV and let the airplane climb asap to assigned level and stay there or do you change over to V/S (500-1000 fpm) to "delay the climb" as to keep the climb gradient flatter and more continuous instead of step climb?
In my company, the skippers have mixed views, some want to stay in VNAV for traffice seperation purposes, others in V/S for passengers comfort and to keep the engines from constantly going from full climb power to almost idle while flying level at low level.
Input from controllers appreciated
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Have you levelled off at 1 altitude before the next climb clearance? If not, and you are in VNAV and can select the next alt/FL before ALT ACQ then stay in VNAV. If you are step climbing then V/S 1000' is better. Remember, that in congested airspace such as a TMA, is a requirement/airmanship/RA avoidance etc. etc. to limit V/S 1000fpm within 1000' of level off. I'm not sure how VNAV helps in 'traffic speration'. 1000fpm will more than achieve that.
As an aside: in B733 we used to use V/S 1000 for step climbs to avoid large thrust inputs, abrupt change in noise/cabin angles/change in g's etc. The CP found out about it and frowned. This was before Eurocontrol made it a recommendation/reuiqrement. It had been like that in FAA land for decades. On B767 (90's) it was even in the customer option PIC autopilot package; small changes in level did not cause full power.
They programmed the autopilot to think like a pilot. Now there's a novelty.
I've always wondered why (if I remember correctly), when the FAA had an SOP for 1000fpm at 1000' to go and 500fpm at 500' to go, the FAA certified autopilots kept outrageous V/S until even 300' to go. Surely they could program VNAV to do just that? Now we have to go VNAV - V/S - (ALT ACQ - ALT HLD) - VNAV. If you can program VNAV on departure to keep a speed up to an acceleration altitude for noise abate, and then climb 250/100 and then econ to CRZFL, why can't you program a VNAV(V/S) at 1000 to go? I'm not saying I want to computer-out the PF, but the use of V/S 1000 is not a universal SOP and it is a manual necessity. At high V/S you can already be ALT ACQ before 1000 to go. Too late.
As an aside: in B733 we used to use V/S 1000 for step climbs to avoid large thrust inputs, abrupt change in noise/cabin angles/change in g's etc. The CP found out about it and frowned. This was before Eurocontrol made it a recommendation/reuiqrement. It had been like that in FAA land for decades. On B767 (90's) it was even in the customer option PIC autopilot package; small changes in level did not cause full power.
They programmed the autopilot to think like a pilot. Now there's a novelty.
I've always wondered why (if I remember correctly), when the FAA had an SOP for 1000fpm at 1000' to go and 500fpm at 500' to go, the FAA certified autopilots kept outrageous V/S until even 300' to go. Surely they could program VNAV to do just that? Now we have to go VNAV - V/S - (ALT ACQ - ALT HLD) - VNAV. If you can program VNAV on departure to keep a speed up to an acceleration altitude for noise abate, and then climb 250/100 and then econ to CRZFL, why can't you program a VNAV(V/S) at 1000 to go? I'm not saying I want to computer-out the PF, but the use of V/S 1000 is not a universal SOP and it is a manual necessity. At high V/S you can already be ALT ACQ before 1000 to go. Too late.
to keep the engines from constantly going from full climb power to almost idle while flying level at low level.
If you can program VNAV on departure to keep a speed up to an acceleration altitude for noise abate, and then climb 250/100 and then econ to CRZFL, why can't you program a VNAV(V/S) at 1000 to go?
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If we are cleared to, say FL100 but SID includes waypoint restrictions with lower altitude, we stay in VNAV (given the restriction is in the FMC) but when cleared "Climb now FLXXX" many (me included) use V/S for the last 3000' or so as to avoid major thrust changes and stay in shallow climb while waiting for a clearance for higher altitude.
VNAV in our 757 does not reduce the V/S when aproaching the cleared level, but instead rockets upwards at 3500+fpm until about 800-1000' prior when alt acq engages, causing sometimes abrupt pitch changes.
Is a 500fpm climb the minimum required/allowed/expected when climbing or should the airplane climb as its performance allows and as soon as possible to assigned level?
VNAV in our 757 does not reduce the V/S when aproaching the cleared level, but instead rockets upwards at 3500+fpm until about 800-1000' prior when alt acq engages, causing sometimes abrupt pitch changes.
Is a 500fpm climb the minimum required/allowed/expected when climbing or should the airplane climb as its performance allows and as soon as possible to assigned level?
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I use v/s all the time to REDUCE the climb rate. Even at the flight levels. Company policy is that the world comes to an end if you use v/s at altitude ("you have no speed protection!!!!). Uh, if it's being used to REDUCE climb rate how is that a problem? Using it to INCREASE climb rate is beyond dumb.
Nothing like being on the tracks and getting a climb from FL350 to FL360. VNAV, rocket power!!!, idle...., level at FL360. How about 200-300' FPM? Most folks won't even notice. If they're standing they will (level sensors in your feet). Otherwise the .5 degree pitch change will be barely noticeable.
There is no engine noise in the cockpit in cruise. Behind the wing it's very obvious.
U.S. Airman's Information Manual (AIM), has the requirements. Less than 500' FPM climb, or 1000' descent, requires notification to ATC. It's not prohibited, you just have to advise ATC. In the tracks (NATS) or non radar you're giving a time to report level. How long you take is up to you as long as you meet the report time.
Nothing like being on the tracks and getting a climb from FL350 to FL360. VNAV, rocket power!!!, idle...., level at FL360. How about 200-300' FPM? Most folks won't even notice. If they're standing they will (level sensors in your feet). Otherwise the .5 degree pitch change will be barely noticeable.
There is no engine noise in the cockpit in cruise. Behind the wing it's very obvious.
U.S. Airman's Information Manual (AIM), has the requirements. Less than 500' FPM climb, or 1000' descent, requires notification to ATC. It's not prohibited, you just have to advise ATC. In the tracks (NATS) or non radar you're giving a time to report level. How long you take is up to you as long as you meet the report time.
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Use FLCH? How does that differ from using VNAV or v/s to climb 1000'? Or differ from VNAV or v/s when trying to manage climb rate to avoid the level off/climb/level off/climb aspect of some departures(and arrivals)?
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I typically will leave the airplane in an Open Climb and disengage the A/THR (whether with AP on or off). I find sometimes (especially when light - changing from a very high vertical speed) the airplane will hunt around for speed control after dialling back the v/s thus having many annoying power changes.
On the bus, generally I (and some that I fly with) will climb at greendot until we are above noise abatement altitudes. From there we can turn enroute faster. If we will level off I hold green dot for a bit longer until about 2-3000 feet until my cleared altitude (depending on weight/climb performance). At that point selecting managed speed (typically 250) the v/s will drop to accelerate. I will disconnect the A/THR at that point so that when the plane thinks it wants to increase pitch again to keep the 250 it maintains the current v/s. At 2000 feet I start reducing thrust to target 1000 fpm at 1000 feet to my cleared altitude.
This method seems to always work regardless of turbulence/wind shifts (where the a/thr starts over controlling the thurst.)
If we require a shallow climb rate at a constant speed, if its a smooth day and the A/THR/AP works well then ill let it do it's thing. If the autopilot is hunting around for the right speed ill take it over just to smooth things out.
On those dark and dirty nights where you have lots to worry about - I care a bit less of pax comfort let the airplane do it's thing and let us worry about the more pressing issues.
On the bus, generally I (and some that I fly with) will climb at greendot until we are above noise abatement altitudes. From there we can turn enroute faster. If we will level off I hold green dot for a bit longer until about 2-3000 feet until my cleared altitude (depending on weight/climb performance). At that point selecting managed speed (typically 250) the v/s will drop to accelerate. I will disconnect the A/THR at that point so that when the plane thinks it wants to increase pitch again to keep the 250 it maintains the current v/s. At 2000 feet I start reducing thrust to target 1000 fpm at 1000 feet to my cleared altitude.
This method seems to always work regardless of turbulence/wind shifts (where the a/thr starts over controlling the thurst.)
If we require a shallow climb rate at a constant speed, if its a smooth day and the A/THR/AP works well then ill let it do it's thing. If the autopilot is hunting around for the right speed ill take it over just to smooth things out.
On those dark and dirty nights where you have lots to worry about - I care a bit less of pax comfort let the airplane do it's thing and let us worry about the more pressing issues.
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Use FLCH? How does that differ from using VNAV or v/s to climb 1000'? Or differ from VNAV or v/s when trying to manage climb rate to avoid the level off/climb/level off/climb aspect of some departures(and arrivals)?
Thus there is a danger when using V/S inappropriately at higher flight levels, such as cruise climbs. As using V/S has its design emphasis on achieving the rate of climb allowing low speed to develop until low speed protection activates as it pitches for a selected rate and then attempts to achieve the speed selected while maintaining the selected rate of climb. This could lead to an under-speed situation to occur if not used with caution.
However, equally using V/S has its benefits for the same cruise climb if aircraft far exceeds the maximum 1000'/min due performance capabilities.
IMHO there is thus a time and place to use either/or other, neither is exclusively correct. Good airmanship will dictate which option to use.
Back to the OP...
Departures with new climb instructions, when given in UK airspace, should include the term NOW or UNRESTRICTED if the controller would like you to climb without adhering to the published altitude restrictions on the SID. Thus if cleared to climb, VNAV will level off at intermediate restriction unless you remove it, this is safe. The closure rate of VNAV is commanded by the ACQUIRE manoeuvre of your jet, thus may exceed 1000'/min, which should therefore be actioned by yourself if you observe this to happen using V/S. In all other cases when climbing from e.g. 4000' to FL120, this should not be done using V/S, rather use full/derated climb power, as ATC monitors your rate of climb and will give further clearance or handover when approaching your assigned altitude/level. Reducing the climb rate using V/S will give ATC possibly the idea that you are limited in climb capability performance. Further climb clearances to new altitudes/levels may take this personally introduced limitation into account without your intention.
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Please be aware of the muppets that have an SOP of <1000fpm with 1000 to go. They climb in VNAV at high level; a/c is struggling for 700fpm; the buzzer goes at 900' and the muppet selects V/S 1000'. Please oh please bite your tongue and allow the scenario to unfold. Hopefully they'll never do it again, but learn to scan. (I don't mean let the machine gun go off).
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Thanks Canadian, reminds me of why I'm not a fan of the AB.....
CP's a renown for the common sense of ferrets. They sit in the towers, looking at ASRs and f**kups and generally only think about restricting pilots from making mistakes or infact deviating in any way from the best practice they have evolved from flying once a month whether they need to or not.
Boeing or Airbus, Dash or Avro, it doesn't really matter what aircraft, the passengers want a smooth ride, comfort and suchlike, or they'll choose someone else.
ATC want us to climb when asked and not to trigger TCAS warnings all over the place.
Perhaps we should just manage our aircraft with common sense. Personally, SPEED and VS work well on every type I have flown. Smooth changes, sensible rates and no problems.
AB? Push the knobs in and let the plane fly as requested should work..the Autothrottle can't be that bad, can it?
CP's a renown for the common sense of ferrets. They sit in the towers, looking at ASRs and f**kups and generally only think about restricting pilots from making mistakes or infact deviating in any way from the best practice they have evolved from flying once a month whether they need to or not.
Boeing or Airbus, Dash or Avro, it doesn't really matter what aircraft, the passengers want a smooth ride, comfort and suchlike, or they'll choose someone else.
ATC want us to climb when asked and not to trigger TCAS warnings all over the place.
Perhaps we should just manage our aircraft with common sense. Personally, SPEED and VS work well on every type I have flown. Smooth changes, sensible rates and no problems.
AB? Push the knobs in and let the plane fly as requested should work..the Autothrottle can't be that bad, can it?
No problem for me in using VS in the climb. These modes are just that - modes of operation provided by the manufacturer. An understanding of how they work allied to the much maligned concept of 'airmanship' should provide a satisfactory solution for all normal requirments.
Canadian Pilot, the speed hunting is down to how the aircraft is manging the climb. In V/S mode in an Airbus the autothrust is managing the speed and the vertical speed is being managed by the elevator.Iam surprised by your assertion of hunting as the aircraft does everything at 1g, which is meant to be very smooth. The FBW is meant to be flown as an integrated package so reverting to manual thrust just doesn't make sense to me .I doubt that your method is any smoother than just selecting with a bit if finesse a vertical speed of 1000ft min.
Last edited by tubby linton; 24th Aug 2015 at 21:45.
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LVLCHG differs not in climb from VNAV. However it does from V/S. So much as to that it allows you to climb with full power.
Any of the 3 modes will "allow" full climb thrust, if the conditions are right for it.
VNAV will almost always go to full climb thrust, unless the next altitude is captured before CLB thrust is attained.
V/S will use full climb thrust whenever the speed and V/S selected require CLB thrust or more. Then IAS will be sacrificed to maintain V/S.
FLCH will use whatever thrust is needed to attain the selected altitude in 2 minutes. If the CLB thrust limit is reached, V/S will be reduced to maintain selected IAS.
FWIW, I almost always stay in VNAV for the climb. Initially, VNAV optimizes acceleration and climb. With the NADP1 profile, the 744 won't reach climb speed until 4000' or higher anyhow, so V/S will be in the 1000 FPM range during acceleration until then.
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No problem for me in using VS in the climb. These modes are just that - modes of operation provided by the manufacturer. An understanding of how they work allied to the much maligned concept of 'airmanship' should provide a satisfactory solution for all normal requirments.
Ah, finally, a sane breath of fresh air. Dream on Macduff. We all can.
Ah, finally, a sane breath of fresh air. Dream on Macduff. We all can.
I agree with Intruder and RAT 5: understand what the automation does and why and you can make an informed decision about what modes to use in a particular circumstance.
*Think* about what you want to achieve and how environmental factors (speed, altitude, available performance, ATC, other aircraft, etc.) are going to affect you then make a choice.
There are often many ways of achieving similar results and the aircraft manufacturer has acknowledged this by giving you options. Don’t be a microwave operative - be a chef!
*Think* about what you want to achieve and how environmental factors (speed, altitude, available performance, ATC, other aircraft, etc.) are going to affect you then make a choice.
There are often many ways of achieving similar results and the aircraft manufacturer has acknowledged this by giving you options. Don’t be a microwave operative - be a chef!
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There are often many ways of achieving similar results and the aircraft manufacturer has acknowledged this by giving you options. Don’t be a microwave operative - be a chef!
Oh that the CP, DFO & HOT would let you. Today there are too many SOP operators and not enough knowledgeable pilots. Too many believe there is only one method of operation, and when that seems not the best idea have no idea of the alternative options. They never were taught properly how the a/c and its systems were designed.
e.g. I once flew for an operator whose SOP on G/A was to fly manually until flaps up. On a real nasty night, heavy rain, turbulence, no radar, NPA and low MAA I made a G/A and engaged A/P PDQ as we were above minimum A/P engagement height. In a relaxed manner we cleaned up, I spoke to ATC (quicker) to ask for a non-standard routing to avoid weather and we climbed out clear of the mess into safe air and a safe area. The F/O was fully occupied with PM/PNF-ing. In the hold he asked "if we were 'allowed' to engage the A/P before flaps up?" My reply was, "did it engage? and do you think it was a good idea in the testing circumstances?" A pause, and thought, and a "yes, so why don't we do that every time?"
Ah, you're asking the wrong bloke. Know your a/c and use it wisely to achieve required task. There are various methods to succeed in that, all within the design envelope.
Oh that the CP, DFO & HOT would let you. Today there are too many SOP operators and not enough knowledgeable pilots. Too many believe there is only one method of operation, and when that seems not the best idea have no idea of the alternative options. They never were taught properly how the a/c and its systems were designed.
e.g. I once flew for an operator whose SOP on G/A was to fly manually until flaps up. On a real nasty night, heavy rain, turbulence, no radar, NPA and low MAA I made a G/A and engaged A/P PDQ as we were above minimum A/P engagement height. In a relaxed manner we cleaned up, I spoke to ATC (quicker) to ask for a non-standard routing to avoid weather and we climbed out clear of the mess into safe air and a safe area. The F/O was fully occupied with PM/PNF-ing. In the hold he asked "if we were 'allowed' to engage the A/P before flaps up?" My reply was, "did it engage? and do you think it was a good idea in the testing circumstances?" A pause, and thought, and a "yes, so why don't we do that every time?"
Ah, you're asking the wrong bloke. Know your a/c and use it wisely to achieve required task. There are various methods to succeed in that, all within the design envelope.
Last edited by RAT 5; 26th Aug 2015 at 09:06.
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I hear what you're saying. I found the newer airbuses are much better but the older fins (I have flown a handful that are double midget serial numbers) do hunt around for the speed. Say you're climbing out at 250 kts and the plane is doing 3000 fpm. Pulling VS and dialling it back to 2000-2500 fpm is usually pretty smooth when you start pulling it back further to 1000 fpm the speed tends to increase, then the plane pulls a bit too much power off and the adds it again. Same thing at ALT * sometimes the plane pulls off a bit too much power and hunts around for a second. It can also be fairly aggressive pulling speed off. In open climb the climb rate will decrease to maintain the 250kts (or what ever target is) if you slowly decrease the trust manually it can be much smoother.
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CanadianAirbusPilot
SOPs should not be something which are in company manuals but pilots are not comfortable following them and in daily operations they do things differently. This creates a culture where no one believes in the wisdom of OPS department's or the manufacturer's procedures and has his own thing going. In FBW aircraft FCOM knowledge is not enough to develop your own procedures as the design features, logic of computers and limitation of certain modes is not given in its entirety nor an average pilot is software expert to understand all that. Safer is to refer the matter to the company and the manufacturer and seek their guidance or approval. This particular use of ATHR or V/S may not create problems but the attitude to be different is problematic and can create problems. For example in a GA after setting TOGA thrust FMA call out is mandatory and essential according to Airbus. Three airlines relegated this to after raising gear and this resulted in incidents in all those airlines and in the worst case the aircraft came down to 14ft. above runway in IMC. It could have been fatal on another day.
SOPs should not be something which are in company manuals but pilots are not comfortable following them and in daily operations they do things differently. This creates a culture where no one believes in the wisdom of OPS department's or the manufacturer's procedures and has his own thing going. In FBW aircraft FCOM knowledge is not enough to develop your own procedures as the design features, logic of computers and limitation of certain modes is not given in its entirety nor an average pilot is software expert to understand all that. Safer is to refer the matter to the company and the manufacturer and seek their guidance or approval. This particular use of ATHR or V/S may not create problems but the attitude to be different is problematic and can create problems. For example in a GA after setting TOGA thrust FMA call out is mandatory and essential according to Airbus. Three airlines relegated this to after raising gear and this resulted in incidents in all those airlines and in the worst case the aircraft came down to 14ft. above runway in IMC. It could have been fatal on another day.
