Vref & landing
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Hi All !
Thank you all for your comments so far !
Framer : it has been established that the horn im hearing is nothing to do with the stall warning system, maybe more to do with the Horn that warns if there is a small amount of fuel sloshing around in the ventral tank ! but you are 100% right, i want to get the correct technique now so that I wont have to re-learn in the future.
On my flights so far there have been no crosswinds, but the book says to add half the gust !
Someone actually took the time to explain the technique to me over the phone yesterday, so thanks to them
Spam Up
Framer : it has been established that the horn im hearing is nothing to do with the stall warning system, maybe more to do with the Horn that warns if there is a small amount of fuel sloshing around in the ventral tank ! but you are 100% right, i want to get the correct technique now so that I wont have to re-learn in the future.
On my flights so far there have been no crosswinds, but the book says to add half the gust !
Someone actually took the time to explain the technique to me over the phone yesterday, so thanks to them
Spam Up
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Vref and landing
Spam Up:
Fly Vref + Additives (Vap), then bleed off a little during the flare (do not stall).
The early HS 125 business jets had an excellent lift dump system for after landing. It was like landing on a treacle covered runway.
Tmb
Fly Vref + Additives (Vap), then bleed off a little during the flare (do not stall).
The early HS 125 business jets had an excellent lift dump system for after landing. It was like landing on a treacle covered runway.
Tmb
Good stuff Spam, I just mentioned the tail strike thing because when I first went onto the 737 the landing attitude looked very flat to me after turbo props and took a few hundred hours before it seemed normal. Are you flying with Captains that can show you what the picture looks like?
Like I said before I have no idea about the Hawker, does it seem like a flatter attitude than your last a/c?
Like I said before I have no idea about the Hawker, does it seem like a flatter attitude than your last a/c?
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Hello
I was on a Kingair before and dont really feel the attitude looks much different, good point about the lift dump sytems, it is very effective !
Spam
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I'm a FO on a cj1+ and the commander I fly with (used to fly A320/330) expects me to be at Vref+10 over the numbers (in calm conditions, otherwise the wind corrections as mentioned in some previous posts apply) and to touch down on the runway surface with Vref (never below!). Another commander, however, who has always flown small business jets, applies the power-idle at 50ft AGL technique and then flares the a/c much like a C172, I watched the airspeed sometimes going down to Vmca before the wheels touched the ground. I reckon the former landing technique gives you a greater safety margin.
FE Hoppy – “just be sure you have the extra landing distance required”
Absolutely correct! The extra 10 kts that pilots add without thought is equivalent to 300-500ft added to the actual landing distance ( AC 91-71 Runway Overrun Prevention), and that’s without considering any effect on extending the flare.
Many pilots think that they can adjust their landing technique in adverse landing conditions, thus minimizing any additional distance; however as indicated above there is only one optimum landing technique, and the associated skills are best improved by constant practice. Furthermore when the approach and landing conditions are poor, and the manufacturers recommendation for speed addition is followed, then we need to exercise the mental skill of adding the speed-additive-distance to the landing distance required just to maintain the same level of safety as for a ‘calm’ day, ‘dry’ runway landing; if not, this could be judged as poor risk management in the event of an overrun.
Spam Up, you may be seeking a real smooth touchdown in the 125-800; IMHO this is difficult to achieve as the gear / structure is relatively ‘stiff’ occasionally causing the aircraft to shake and the touchdown feel hard. Also, small roll errors give some ‘judder’ from a single wheel touchdown. The 125 is relatively demanding when seeking excellence, but the low flight deck, small aircraft, ‘heavy’ control feel provide a good basis for improving landing skills which can be transferred to larger aircraft in the future .
Absolutely correct! The extra 10 kts that pilots add without thought is equivalent to 300-500ft added to the actual landing distance ( AC 91-71 Runway Overrun Prevention), and that’s without considering any effect on extending the flare.
Many pilots think that they can adjust their landing technique in adverse landing conditions, thus minimizing any additional distance; however as indicated above there is only one optimum landing technique, and the associated skills are best improved by constant practice. Furthermore when the approach and landing conditions are poor, and the manufacturers recommendation for speed addition is followed, then we need to exercise the mental skill of adding the speed-additive-distance to the landing distance required just to maintain the same level of safety as for a ‘calm’ day, ‘dry’ runway landing; if not, this could be judged as poor risk management in the event of an overrun.
Spam Up, you may be seeking a real smooth touchdown in the 125-800; IMHO this is difficult to achieve as the gear / structure is relatively ‘stiff’ occasionally causing the aircraft to shake and the touchdown feel hard. Also, small roll errors give some ‘judder’ from a single wheel touchdown. The 125 is relatively demanding when seeking excellence, but the low flight deck, small aircraft, ‘heavy’ control feel provide a good basis for improving landing skills which can be transferred to larger aircraft in the future .
the commander I fly with (used to fly A320/330) expects me to be at Vref+10 over the numbers
My understanding is that Vref is a 50ft speed, not a touchdown speed. I would get the QRH out and determine how much extra distance is used by carrying the extra speed. I reckon you'll be developing a mental picture of what the flare attitude looks like that isn't quite right if you are carrying extra speed and also one day you might operate into a strip where it really counts.
Just an opinion though. Good thread I reckon.
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The answers are all in this thread just not in one post, applying boeing airbus landing techniques to a Hawker 800 maybe isn't quite as relevant as people think much more iniertia, different spool down rates for the engines.
My 2p'sworth is to read the AFM, in their is a definiive guide to how the test pilots derived at the raw figures, more than likely it will say that the TR's were not involved, it will probably say that the thrust levers were closed at 50ft at VREF over the runway. Test pilots when certifying aircraft are fairly brutal with them, not for the reasons of trying to achieve better figures but to ensure that they have consistency in their data, no point chuck landing one way and john another.
Regardsless of what advise you are given here just arrive at 50ft on speed and then do what the AFM says! should you wish to be less brutal than the test pilots youwill use more runway, this is what factoring is about cos we dont want to hit the runway at 180fpm or whatever the hard landing criteria says it is.
If you add speed then more runway will be used, consider the 90 degree gusting x-wind scenario if you are arriving with an extra 10-15 knots and its Part 91/private and its a tight runway then problems may ensue!
My 2p'sworth is to read the AFM, in their is a definiive guide to how the test pilots derived at the raw figures, more than likely it will say that the TR's were not involved, it will probably say that the thrust levers were closed at 50ft at VREF over the runway. Test pilots when certifying aircraft are fairly brutal with them, not for the reasons of trying to achieve better figures but to ensure that they have consistency in their data, no point chuck landing one way and john another.
Regardsless of what advise you are given here just arrive at 50ft on speed and then do what the AFM says! should you wish to be less brutal than the test pilots youwill use more runway, this is what factoring is about cos we dont want to hit the runway at 180fpm or whatever the hard landing criteria says it is.
If you add speed then more runway will be used, consider the 90 degree gusting x-wind scenario if you are arriving with an extra 10-15 knots and its Part 91/private and its a tight runway then problems may ensue!
Stanley Eevil, - “…performance manuals assume a 15kt overspeed…”
I believe that you are perpetuating a widely held misbelief; see:- Landing performance of large transport aeroplanes.
Modern certifications/operations use a factored landing distance:-
“…in order to provide an operationally realistic value of performance, this gross distance is multiplied by a field length factor to obtain the Landing Distance Required.
This factor accounts for the normal operational variability that can be expected in day to day service such that the chances of a landing overrun are remote”.
The AIC does discuss an (old) alternative method of determining landing performance from a ‘fast landing’, Vref+15 (and from a low screen ht, 30ft), but this ‘error value’ was an alternative means of contributing to a safety factor catering for operational variability. The speed error, or field length factor, are not margins to be employed routinely without thought about the change in safety / risk.
I believe that you are perpetuating a widely held misbelief; see:- Landing performance of large transport aeroplanes.
Modern certifications/operations use a factored landing distance:-
“…in order to provide an operationally realistic value of performance, this gross distance is multiplied by a field length factor to obtain the Landing Distance Required.
This factor accounts for the normal operational variability that can be expected in day to day service such that the chances of a landing overrun are remote”.
The AIC does discuss an (old) alternative method of determining landing performance from a ‘fast landing’, Vref+15 (and from a low screen ht, 30ft), but this ‘error value’ was an alternative means of contributing to a safety factor catering for operational variability. The speed error, or field length factor, are not margins to be employed routinely without thought about the change in safety / risk.
When scheduling LDR, most performance manuals assume a 15kt overspeed with regards to VAT/Vref anyway?
I am going flying tomorrow and when I am PM I will take note of the exact touchdown IAS on a couple sectors and work out what % of VS it is. I'm picking it will be about 1.2VS, maybe but probably not 1.3 .
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I know just how much everyone on this forum likes to have someone come along and “tell them” how it’s to be done. So, for those of you here who are older than ½ of my age – stop reading and go on down to the next post. OK, maybe you don’t know my age, but I was around when dirt was invented – that should give you an approximation. But, for you folks who are less than ½ of my age, listen up – this may be important to you, and, after a little practice, you just may be able to teach those guys who have now stopped reading how to really land an airplane. This procedure is applicable to every airplane from a C-152 to a B-747 (I haven’t flown a B-52 or the A-380, but I’ll bet it works there, too) – it also works in calm conditions, head winds, tail winds, cross winds, CAVU conditions, snow, ice, rain, simple IMC conditions, and even FLIR-aided IMC conditions.
As almost all of the folks above have indicated – the last portion of the final approach should be flown in the configuration in which you plan to land, and flown at a constant speed of 1.3 Vs (computed in that configuration), plus ½ of the steady state wind (not to exceed an additive of 20 knots) plus all of the gust factor. I personally believe that this steady-state condition should be established at 1000 feet AGL, but I know that some operations allow this altitude to be lower – but in the passenger revenue world I’m not aware of any that are below 500 feet AGL.
You should cross the runway threshold at what ever is the minimum threshold crossing height – for most transport category airplanes this should be about 50 feet. And at that point you should have been able to bleed off the airspeed additives you’ve been holding for steady-state wind (only the steady-state wind additives) – you’ll still have the 1.3 Vs plus all the gust factor. This will require you to continue to fly the airplane to the runway. Some operators recommend that you begin to reduce power at this point – if that is the procedure you’ve been taught, fine – but keep the airspeed constant until you begin the flare (that may mean pushing the nose over a bit – hopefully it will only require nose down pressure and not nose down movement. The point to which you should be flying at this point (the “aim” point – that point that doesn’t move up or down in the windscreen) is a point on the runway surface about 2/3 of the way between the threshold and the fixed distance markers (for the C-150 guys, this aim point should be the numbers themselves and for the B-747 guys, the aim point should be the fixed distance markers or just beyond).
OK, now for the flare. The question that always comes up is, “what attitude do I flare to?” When you start to flare is critical. You will want to reach your flare attitude with the main wheels something between 1 and 5 feet from the runway surface (1 foot or so for the C-152 guys and 5 feet for the B-747 guys … yes, I know how difficult it is to imagine the mains at 5 feet above the runway from the B-747 cockpit – but remember, you’re good at your job! – Make it 5 feet!) The change in the attitude from when you initiate the flare to reaching the flare attitude should take 3 seconds and you should wind up with the main wheels “just off the runway surface. The speed you should have when you reach the flare attitude should be just below what you carried from the threshold to this point – between 5 and 15 knots – the smaller number for the smaller airplanes and the larger number for the larger airplanes. The attitude should be just exactly what it would take to maintain level flight from this point all the way down the runway. What I’d have you practice would be, “do not climb, do not descend, do not accelerate, do not decelerate; we’ll go around at the end of the runway.” I’d also have you mentally locate the position on the belly of the airplane exactly between the main gear (the body gear for you B-747 guys) and I’d tell you to fly down the runway (no climb, no descent, no faster, no slower) with that point on the belly of the airplane exactly over the runway centerline – and to do that with whatever crab angle you need to do it. Of course you’d have to add a bit of power – since you had the throttles back but this is OK for practice.
I’d have you do this exercise as many times as was necessary to get you comfortable with when to initiate the flare, how quickly to flare, and to what attitude you need to stop the flare with the main gear just off the runway surface. The key here, getting you to recognize when to start the flare and how quickly to flare, is to get you to recognize what attitude to reach at the end of the flare – THAT attitude is the LEVEL FLIGHT ATTITUDE.
Once you’ve got it, as you begin the flare you begin the throttle reduction. The idea is to get the throttles to the idle position as the mains touch the runway. As you pull the throttles back, you will notice the nose getting heavier – don’t let it move down. Increase the back pressure on the elevator controls – not to move the nose up – rather to just keep it from moving down. Over that 3 seconds, the airspeed to continues to decelerate, while the airplane continues to descend, going from just above the runway to ON the runway. Level Flight Attitude is the attitude from which you want to land the airplane. Your touchdown should be firm but not hard, the kinetic energy of the airplane should be moving in the right direction, the nose should be able to be flown to the runway rather quickly as it is not unnecessarily high to arrest a high sink rate. You should be over the center of the runway, with the controls already properly positioned for the landing run.
If you had been carrying a crab angle to counter a crosswind, the crab should be removed in exactly the same time as the flare takes – 3 seconds. The pressure applied to the rudder pedal to pressure the nose around to line up with the centerline of the runway should start with the back pressure on the control column to flare. As you probably know, this may take some into-the-wind aileron to counter the tendency of the forward sweeping wing to rise … but, unless the wind is quite strong, you won’t be in the air long enough to have the wind blow you downwind off the centerline. Of course, if the wind IS quite strong, you may have to add a bit more aileron to slightly (very slightly) dip the wing tip in the up-wind direction.
I offer just one caveat. If you discuss this with your chief pilot or fleet captain and they absolutely forbid you to fly and land this way – pay attention to your company and forget what I’ve said. This is not an attempt to thwart the way your company procedures require you to operate. If this is different from the way you normally approach and land, I do not recommend that you do it without everyone in the cockpit knowing what you are going to do, no matter what position you are flying – if you can swing it, I’d recommend practicing it in the simulator with someone who knows what they are doing. I think you’ll be surprised at how easy this becomes, and how consistent your landings will become as well – night, day, rain, snow, clear, no matter. Consistent landings are good things to cultivate. Also, if you try this and just simply think it is the epitome of wrong-headedness, let me know and I’ll buy you a beer. However, if you think it is the correct way to land, let me know and I’ll buy you two!
As almost all of the folks above have indicated – the last portion of the final approach should be flown in the configuration in which you plan to land, and flown at a constant speed of 1.3 Vs (computed in that configuration), plus ½ of the steady state wind (not to exceed an additive of 20 knots) plus all of the gust factor. I personally believe that this steady-state condition should be established at 1000 feet AGL, but I know that some operations allow this altitude to be lower – but in the passenger revenue world I’m not aware of any that are below 500 feet AGL.
You should cross the runway threshold at what ever is the minimum threshold crossing height – for most transport category airplanes this should be about 50 feet. And at that point you should have been able to bleed off the airspeed additives you’ve been holding for steady-state wind (only the steady-state wind additives) – you’ll still have the 1.3 Vs plus all the gust factor. This will require you to continue to fly the airplane to the runway. Some operators recommend that you begin to reduce power at this point – if that is the procedure you’ve been taught, fine – but keep the airspeed constant until you begin the flare (that may mean pushing the nose over a bit – hopefully it will only require nose down pressure and not nose down movement. The point to which you should be flying at this point (the “aim” point – that point that doesn’t move up or down in the windscreen) is a point on the runway surface about 2/3 of the way between the threshold and the fixed distance markers (for the C-150 guys, this aim point should be the numbers themselves and for the B-747 guys, the aim point should be the fixed distance markers or just beyond).
OK, now for the flare. The question that always comes up is, “what attitude do I flare to?” When you start to flare is critical. You will want to reach your flare attitude with the main wheels something between 1 and 5 feet from the runway surface (1 foot or so for the C-152 guys and 5 feet for the B-747 guys … yes, I know how difficult it is to imagine the mains at 5 feet above the runway from the B-747 cockpit – but remember, you’re good at your job! – Make it 5 feet!) The change in the attitude from when you initiate the flare to reaching the flare attitude should take 3 seconds and you should wind up with the main wheels “just off the runway surface. The speed you should have when you reach the flare attitude should be just below what you carried from the threshold to this point – between 5 and 15 knots – the smaller number for the smaller airplanes and the larger number for the larger airplanes. The attitude should be just exactly what it would take to maintain level flight from this point all the way down the runway. What I’d have you practice would be, “do not climb, do not descend, do not accelerate, do not decelerate; we’ll go around at the end of the runway.” I’d also have you mentally locate the position on the belly of the airplane exactly between the main gear (the body gear for you B-747 guys) and I’d tell you to fly down the runway (no climb, no descent, no faster, no slower) with that point on the belly of the airplane exactly over the runway centerline – and to do that with whatever crab angle you need to do it. Of course you’d have to add a bit of power – since you had the throttles back but this is OK for practice.
I’d have you do this exercise as many times as was necessary to get you comfortable with when to initiate the flare, how quickly to flare, and to what attitude you need to stop the flare with the main gear just off the runway surface. The key here, getting you to recognize when to start the flare and how quickly to flare, is to get you to recognize what attitude to reach at the end of the flare – THAT attitude is the LEVEL FLIGHT ATTITUDE.
Once you’ve got it, as you begin the flare you begin the throttle reduction. The idea is to get the throttles to the idle position as the mains touch the runway. As you pull the throttles back, you will notice the nose getting heavier – don’t let it move down. Increase the back pressure on the elevator controls – not to move the nose up – rather to just keep it from moving down. Over that 3 seconds, the airspeed to continues to decelerate, while the airplane continues to descend, going from just above the runway to ON the runway. Level Flight Attitude is the attitude from which you want to land the airplane. Your touchdown should be firm but not hard, the kinetic energy of the airplane should be moving in the right direction, the nose should be able to be flown to the runway rather quickly as it is not unnecessarily high to arrest a high sink rate. You should be over the center of the runway, with the controls already properly positioned for the landing run.
If you had been carrying a crab angle to counter a crosswind, the crab should be removed in exactly the same time as the flare takes – 3 seconds. The pressure applied to the rudder pedal to pressure the nose around to line up with the centerline of the runway should start with the back pressure on the control column to flare. As you probably know, this may take some into-the-wind aileron to counter the tendency of the forward sweeping wing to rise … but, unless the wind is quite strong, you won’t be in the air long enough to have the wind blow you downwind off the centerline. Of course, if the wind IS quite strong, you may have to add a bit more aileron to slightly (very slightly) dip the wing tip in the up-wind direction.
I offer just one caveat. If you discuss this with your chief pilot or fleet captain and they absolutely forbid you to fly and land this way – pay attention to your company and forget what I’ve said. This is not an attempt to thwart the way your company procedures require you to operate. If this is different from the way you normally approach and land, I do not recommend that you do it without everyone in the cockpit knowing what you are going to do, no matter what position you are flying – if you can swing it, I’d recommend practicing it in the simulator with someone who knows what they are doing. I think you’ll be surprised at how easy this becomes, and how consistent your landings will become as well – night, day, rain, snow, clear, no matter. Consistent landings are good things to cultivate. Also, if you try this and just simply think it is the epitome of wrong-headedness, let me know and I’ll buy you a beer. However, if you think it is the correct way to land, let me know and I’ll buy you two!
The highest degree of confidence in successfully achieving the scheduled landing distances is obtained by crossing the threshold
at the correct height and at the target threshold speed, touching down firmly after a normal flare and applying maximum retardation
without delay.
at the correct height and at the target threshold speed, touching down firmly after a normal flare and applying maximum retardation
without delay.
Can I ask someone to confirm for me that the 'Target Threshold Speed' mentioned in the above post is indeed Vref+5 on a nice day, and not Vref.
In my company we arrive at 50ft at Vref+5 on a nice day . Cheers again
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AirRabbit,
Excellent description of how to teach someone how to correctly "flare" (check?) for landing - the best I've ever read - thanks!
Re the initial issue, just to add to the confusion - Airbus and Boeing ahve different meanings for Vref. In "AB-speak" there's only one Vref = Vls Config (Flaps/Slats) FULL. Due to the low-speed protections of the fly-by-wire system this is lower than the traditional Vref at 1.23 Vs instead of 1.3 Vs (in that configuration). In practice it means little (as Vls is not Vs) but AB has cunningly hidden it away in one little line in the QRH
p 2.32.
Essentially, no matter which type you fly, there will some additive to your basic approach speed to cater for the wind - usually up to a max of 20 kts so as not to infringe the landing distance calculation. In all cases, most if not all of this should be bled off after you cross the threshold and it is perfectly acceptable - even desirable - to touch down at a speed below Vref/Vls.
What's most important of all is to touch down in the TDZ and get the nosewheel on the ground without delay to maximise the retardation effort. Many more aircraft have gone off the far end of runways than have landed short (although it's usually more severe to hit the fence on the way in!). Safe landings (i.e. in TDZ) are what is required in any a/c especially a transport category one - not smooth ones. If you can achieve both, congratulations but never hold it off for a greaser.
Happy (safe) landings. You're only as good as the last one.
Excellent description of how to teach someone how to correctly "flare" (check?) for landing - the best I've ever read - thanks!
Re the initial issue, just to add to the confusion - Airbus and Boeing ahve different meanings for Vref. In "AB-speak" there's only one Vref = Vls Config (Flaps/Slats) FULL. Due to the low-speed protections of the fly-by-wire system this is lower than the traditional Vref at 1.23 Vs instead of 1.3 Vs (in that configuration). In practice it means little (as Vls is not Vs) but AB has cunningly hidden it away in one little line in the QRH
p 2.32.
Essentially, no matter which type you fly, there will some additive to your basic approach speed to cater for the wind - usually up to a max of 20 kts so as not to infringe the landing distance calculation. In all cases, most if not all of this should be bled off after you cross the threshold and it is perfectly acceptable - even desirable - to touch down at a speed below Vref/Vls.
What's most important of all is to touch down in the TDZ and get the nosewheel on the ground without delay to maximise the retardation effort. Many more aircraft have gone off the far end of runways than have landed short (although it's usually more severe to hit the fence on the way in!). Safe landings (i.e. in TDZ) are what is required in any a/c especially a transport category one - not smooth ones. If you can achieve both, congratulations but never hold it off for a greaser.
Happy (safe) landings. You're only as good as the last one.
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framer - my understandng of 'threshold' is start of runway, which should be crossed at around 50', so in my book, Vref+5 at 50' is the target, as you are doing.
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Vref+5 at 50' is the target, as you are doing.
Typical Hawker Vref 115KIAS V squared = 13225
+ 5 knots for the wife/kids = 14400
Difference is 1175 as a percentage of 13225 =9%
9% more lift energy to go somewhere, where is it eventually going to go? Brakes?? Runway ??
Might work on your boeing though
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constant speed of 1.3 Vs (computed in that configuration), plus ½ of the steady state wind
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Originally Posted by GSPOT
9% more lift energy to go somewhere, where is it eventually going to go? Brakes?? Runway ??
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Sorry - crossed purposes somewhere. I was advocating Vref at 50ft because that is how the book says the aircraft should be flown and how the figures are derived. What Boeing, Airbus et all reccomend before you get to 50ft is whatever the company or manufacturer consider to be safe.
My point was that on a limiting runway 50ft at Vref is whats required to make book, up until that point then Vref +** is determined by whatever portion of h/w/ or gusts or other weather math you/your company choose to deploy
Framer is instructed to be at the Threshold at 50ft at Vref +5 hence my amateurish maths.
Sorry for mixup
My point was that on a limiting runway 50ft at Vref is whats required to make book, up until that point then Vref +** is determined by whatever portion of h/w/ or gusts or other weather math you/your company choose to deploy
Framer is instructed to be at the Threshold at 50ft at Vref +5 hence my amateurish maths.
Sorry for mixup