Vref & landing
 

Hello All

Whats is the correct speed for landing a jet ? It has been suggested to me that you should land at Vref !

Im new to a jet and my technique for landing has always been Vref over the threshold and then, it becomes a visual thing.
So in my new type (Hawker 800) I maintain Vref till over the threshold and then when I hear the 20ft call I slowly reduce the power - level off and catch the sink with a bit of nose up which gives a nose up attitude for landing, this way of course the speed bleeds off and on a couple of occasions a fraction of a sec before landing the stall warner has sounded (is this wrong ?), I thought this would be a good thing as it means you are landing at a slow speed and making the most of aerodynamic drag.

Look forward to your replys !!

Spam Up

When I say a fraction of a second, I really mean a fraction !

so tell me then , why is it okay in a C172 and not anything else, im still getting good landings with this technique ?

Spam Up

Vref is supposed to be the min speed at ?50ft' on finals, and I have always been taught that this SHOULD be bled off towards touchdown, and touchdown SHOULD occur at a minimum of Vref-5 - although the shrieks and yells from the other seat stop me doing that!:) Indeed, for the B737, Boeing confirm the above.

Correct (Boeing)technique :

Keep FAS : Vref + X ( for winds <= 10 knots : 5kts) until crossing the threshold, thereafter bleed off the speed during the flare.
For gusty winds the correction "X" to Vref would be 1/2 the steady wind + the gust with a maximum of 20 kts.

Why not VRef crossing the threshold ? to have some margin above the stallspeed.

Ummm. The stall warning in a Hawker is the stick shake!!!
Can I respectfully advise that to land with the stick shaker going is NOT correct. :eek: You are tooooooo slooooow. :=

Vref is the speed at 50' over the threshold. Not the touchdown speed. remember it's at least 1.23 Vs. I wouldn't expect stall warning before touchdown though.

I thought there is a horn also ? whats the horn that sounds then :\?

Definetley no stick shaker going off !




Spam

Hi
 

Opened a good old can of worms here !

been thinking about it ! ( yes it hurt ) could it be the horn for the ventral tank because of a nose high attitude causing fuel to slosh around, but isnt that only at high speed or does it warn you also when the gear is down???

My brain hurts now !

Spam

The horn in a Hawker is really multi-purpose. Much like an attention getter.

From the training manual:

STALL WARNING AND IDENTIFICATION SYSTEM

General

A stall warning and identification system is provided to emphasize the aircraft's natural cues available at the point of stall. The system functions are:

Stick shaker (warning)

Stick pusher (identification)

The system comprises ywo sensing channels, each using an airflow angle sensor vane, a signal summing unit (SSU), and a third sensing channel which uses two underwing pressure-sensing vents and a stall identification sensor.

Warning and identification is provided by two stick shaker motors, and hydraulically operated actuator with two integral electrohydraulic valves respectively, and associated logic, announciators and test switches.

SYSTEM LOGIC

1. It is impossible for a stick push to occur before a stall warning (stick shake)

2. No single active fault of an SSU or relay can cause the operation of a stall valve or the associated red STALL VALVE annunciator.

3. The autopilt is disengaged when a stall warning signal is initiated. This prevents the autopilot from attempting to counteract the resulting stick shake operation or subsequent stick push.

STALL WARNING SYSTEM

The stall warning system uses an electrically driven stick shaker on each control column to provide a physical warning of an approaching stall to the pilots.


There is more but I'm knackered now!

If you are not getting the shaker you are not on the stall warning.
Fuel in the ventral tank may be the reason if you are getting the horn!!!!:ok:

Spam Up. IIRC not all versions of ‘HS 125’ (if any) use the standard margins for calculating approach speed; thus you should follow what is written in the ‘particular’ aircraft’s manuals.

Normally the reference approach speed (Vref) is 1.3 stall speed (Vs), and most aircraft are certificated for a landing at or about 93% of Vref, often rounded to a training recommending to touchdown at Vref-7kts. However, as the 125 originated under UK BCARs many years ago, it claimed grandfather rights to maintain the benefits of reduced landing distance from a better (slower?) approach speed. A different FAA certification was used for the original ‘Hawker’ aircraft, circ 125-400, thus giving another set of figures; notably (to the angst of the Hatfield designers) a ‘lower’ FAR part 23 cert standard.
Later UK build and certified 125s may have compromised slightly in either using revised UK requirements, or moving toward the JAR 25 standard, but, not as I recall, ever having a JAR certification.
Most certifications normally account for an abuse approach and landing from Vref-5 at the threshold with a correspondingly lower touchdown speed – tail strike limit.

In addition to the old regulations being applied to later variants of the 125 (at least the 800?), there may have been other differences between the ‘A’ (USA and FAA cert) and the ‘B’ (rest of the world, UK cert) markets (N.B. there were some FAA certs in ‘the rest of the world’ so check the manuals and who owned the aircraft originally/previously). The AFM should reflect these differences, which might also include Vmo / Mmo.
There may be a reference in the aircraft documentation to the certification standard, i.e. UK BCARs (old), UK – becoming JAR, or FAA. When the basis of certification has been established, you can then check the speed margins for approach and landing from the appropriate regulations;- of course follow the advice in your ‘particular’ aircraft manual might be quicker.

The 125 also has a particular characteristic when landing with full flap, in that the ground effect can feel like sitting on a bubble of air, which cushions the landing. This depends on landing at the ‘correct’ speed and ‘holding off’ at relatively low height (1-2 ft?); if the aircraft is too high or held off too long with speed falling, the bubble can burst resulting in a ‘stiff’ landing. The trick is to ‘burst the bubble’ at touchdown.

That's exactly as i posted !
things haven't changed as much since '65 :)

EXCEPT that we set our bug speed at FAS = Vref + correction ! ( min 5 max 20 kts)

Embaer do a nice little pamphlet called understanding Vref and Approach speeds. I don't have it with me but will print extracts from work tomorrow. Not withstanding the Approach speed additions which for the E-jets are half the head plus all the gust min 5 max 20 this speed is expected to be lead off so you cross the threshold at Vref and touchdown below Vref.

Important to know that Vref is used to ensure landing climb and approach climb gradients so could be considerably higher than 1.3 or 1.23 Vsr.

Cross the threshold...
 

Target speed is usually 1/2 the steady state wind plus all the gust factor (if any). This speed is to be held until crossing the threshold (actually
50 feet). Total additives not to exceed 20 kts...


Example: Vref is 120
Landing Runway 10
Reported surface winds: 060/12G22

So, take half of the 12, which equals 6....and all of the gust factor, which is 10 (22-12)

Vapp = 120 + 6 + 10 = 136

Note: This is a TARGET SPEED....it's not a minimum speed or maximum speed...it's what you try to hold...plus or minus...based on the turbulence and wind speed kicking around.

Speed to reduce to as you're crossing the fence:
120 + 10 = 130

(10 is the gust factor...which you are to hold crossing the threshold, going into the flare)

The idea is to touchdown at a speed not below Vref...or thereabouts....so, you have to be prepared for a loss of the gust factor as you go into the flare...thus, you hold the extra speed (in this case the gust factor of 10 kts). In theory, you could lose 10 kts of wind...lose 10 kts of speed...at the worst moment (in the flare)...that's why you keep the gust factor as you cross the threshold.

In the Airbus, we normally use 'Managed Speed' .....so, these calculations are made for you...a different algorithm.


Fly safe,

PantLoad

Boeing have always avoided recommending the point on final approach at which you deliberately commence to reduce airspeed when the only additive is Vref plus half the steady headwind component.

Example runway 27 and wind 270/30 knots. Half the HW comp is 15 knots therefore approach speed Vref plus 15 knots. Under steady wind conditions the average landing will bleed no more than 3-5 knots off in the flare providing you do not float. . That leaves at least 10 knots excess speed. The free flow airstream (wind gradient) commences around 2000 ft above ground level. Below that, ground friction slows the wind. This suggests in a perfect world you should commence the bleed off of the half the steady HW component at 2000 ft. It is this failure to understand the dynamics of bleeding off the half the steady HW component, that has been a factor in some fast landings and subsequent over-runs particularly on a wet or slippery performance limited runway. Everyone becomes an expert when this point is discussed.

For Airbus VAPP would be only 125 as the correction is limited to the higher of
- 5Kt
- 1/3 HEADWIND (excluding gust) max 15Kt

The 727 didn't like Vref+5 always felt better +10. Other Boeings +5 and the gust loading to a max of +20 is fine. I have never been back to Vref in a jet.

I have never flown the Hawker so I don't know if tailstrike is ever an issue.
Maybe someone with lots of jet experience can give their opinion on whether or not Spam is setting himself up for a tailstrike if things start getting a bit gusty. If it is not an issue in the Hawker it may be in other types that you fly Spam....down the track a bit I mean.

Some observations

(a) The 727 didn't like Vref+5 always felt better +10

If my recollection is correct, the -100 was certificated on the basis of stall speed, while the -200 used minimum steady flight speed, leading to the common practice of carrying a bit extra on the later aircraft. I suspect that most (many ?) of us preferred the -100 for landing ease.

(b) the steady wind/gust (Boeing) rules of thumb reflect the reasonably predictable nature of a steady wind (intentional speed bleed into the flare) and the randomness of gusts (maintain the gust additive). This was discussed at length in an old thread. The slightly different tack adopted by Airbus indicates that the subject is a bit rubbery and that the goal can be achieved by multiple, similar techniques.

(c) the certification landing animal is a flight test black art resulting in a substantial operational fudge factor (100/60 or 1.67) for the final AFM data. Those who have been involved with performance takeoff and landing trials will understand what I mean. Rather than agonise over whether a particular aircraft was certificated to this or that, on the line I prefer to consider the underlying intent of the exercise - which is to stop comfortably on the runway .. and I hold that the AFM is the pilot's friend ..

(i) follow the AFM guidance, fly a stable approach, and you are half way to the hotel

(ii) beware of slow speed approaches unless you have lots of instantaneous thrust to counteract gust problems

(iii) beware of low approach path landings lest the undershoot area beckon you

(iii) beware of high speed or high approach path landings lest the overrun area beckon you

(iii) if the aircraft is somewhere near (say, ± 10 kt) the AFM recommendation at screen/touchdown, and touchdown is in the nominal touchdown region (typically around 1500 - 2000 ft into the runway) then there is a high probability of a successful outcome. Conversely, if not, then perhaps one ought already to be on the missed approach or doing something else appropriate and urgent to address the matter.

Here is the conclusion from Embraers guidance pamphlet
 

SECTION V − CONCLUSIONS
From the certification point of view, landing performance data
presented in AFM/AOM is generated considering that the airplane will
be at VREF once it has reached the threshold and is at a height of 50 ft
above the ground.
From a practical point of view, every pilot knows that almost every
approach is better if the airplane maintains a speed higher than VREF
on final approach in order to assure a speed margin above stall should
turbulent air or variable wind conditions be encountered along the
flight path.
Due to these reasons (or at the Captain’s discretion for safety
reasons), sometimes it is not possible to cross the threshold exactly at
VREF. It must be clear that VAPP must be the upper limit in this case. In
this scenario, the pilot must always keep in mind that the performance
achieved cannot be determined exactly but may be close or better
than the calm wind performance data.
Crossing the threshold with VREF at 50 ft height will always
produce, at least, the predicted performance in the AFM and this is
the actual policy suggested by Embraer.

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 :ok:

Spam Up

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

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?

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

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.

To all who carry extra speed over the fence just be sure you have the extra landing distance required.

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 .

Is that what the book says? I'm not being smart, serious question.
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.

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!

When scheduling LDR, most performance manuals assume a 15kt overspeed with regards to VAT/Vref anyway?

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.

Even if that were so, carrying extra speed just erodes any buffer built in. If you land a bit deeper than planned (say 1800ft in) plus you are a couple knots over your planned speed which has already got ten knots added to it, plus it's wet...it all starts to add up I reckon.
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 .
Cheers,

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!

That is the conclusion from the link that safety pee posted above. Thanks for doing that.

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

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.

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.

Nice day your too fast consider the last 50 feet

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

I presume you mean half of the steady state headwind component. That is straight from Boeing.

- I know nothing of the way your a/c landing performance is calculated, but NORMALLY limiting landing weights are predicated on a given touchdown speed. This should be determined in the manufacturer's publications and this is what you should fly. If the 'Hawker' manuals tell you to fly at or below Vref at 50' then that is what you should do, on the basis that the runway has been calculated to be long enough. If you choose to fly slower than the recommended speeds that is up to you, of course, but I would have expected someone to complain. I have not experienced an a/c in my time where I am expected to fly the approach below Vref.

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