Bugging Up Vref, Pros and cons of increasing Vref. Options

[notanastronaut]

Dear Forum:

Would appreciate inputs and opinions on pros and cons of increasing Vref on approach when flying with steady headwind (no cross wind and no gusts).

Recently, the First Officer I was flying with, made the case for the need of increasing the Vref speed by 15 Kts as we were flying an approach to RNW 34 with a reported wind of 340/15. His argument was that by doing so we would compensate for the loss of ground speed, and basically there was no downside as the runway was long and surface conditions were dry.

I do not agree with this operating philosophy, but I am no "astronaut" so I welcome everyone's ideas.

Thanks for participating.

ANA

[Fast Jet]

Dear Forum:

Would appreciate inputs and opinions on pros and cons of increasing Vref on approach when flying with steady headwind (no cross wind and no gusts).

Recently, the First Officer I was flying with, made the case for the need of increasing the Vref speed by 15 Kts as we were flying an approach to RNW 34 with a reported wind of 340/15. His argument was that by doing so we would compensate for the loss of ground speed, and basically there was no downside as the runway was long and surface conditions were dry.

I do not agree with this operating philosophy, but I am no "astronaut" so I welcome everyone's ideas.

Thanks for participating.

ANA

As you stated Captain, there was no crosswind, or gusts and therefore there would be no reason to increase Vref. Unless you were expecting the wind to drop any second for some reason - like a hangar sits on the up wind end of the runway, for example. Plus, 15kts is, as you know, nothing apart from ideal, as you have already accounted for this in your calcs - and therefore your Vref is your final figure - so, should the wind drop due to that hangar on the end of the runway, just an example, then this would have been taken into consideration with the previous calcs you made to arrive at Vref.

[Fast Jet]

your First Officer has fallen into the trap of wanting to re-calc the Vapp - which is not critical as the runway was correctly determined to be long enough. He has forgotten the flight academy rule that your Bugged Vref is derived from your VLS and is your final figure on Approach. You will have got this figure by adding on the W/S onto the VLS which has given you your Vapp and including any further calcs (see later) you may add - increments. So to increase speed above Vref is not necessary at this stage as it has already been done. - by you.

For the benefit of your First Officer - he will remember from his flight academy days that VLS+HWC or derived HWC from XWC / 3 i.e., 1/3rd the W/S = Vapp then with the runway calcs and W.A.T Vapp will be Vref. Notwithstanding how many engines, what systems are up online, what systems are not going to be used for this particular approach.

Now that we have jogged his memory - he will now be doing calcs with a pencil to show you that he knew it all along - I`ll bet he has written an example similar to this:

Landing runway 360 W/V 360/30 VLS 137

So, VLS + 10 (1/3rd of 30) = Vapp [with your other runway perfs in a minute]

So, VLS 137 + 10kts = Vapp 147

Add or subtract increments due to 1 Eng, 2 Eng, 3 Eng, 4 Eng, spoilers in or out reversers out or not plus any asymetrical considerations and Length of Runway, W.A.T. Surface, Slope, / gradient, elev, Wet/Dry/Ice. LDA, LRA, TORA, TODA, Clearway (for any Go Around) plus bits you might add becomes Vref. This being the final figure, pun intended becomes your bug speed.

In the Airbus, which I frequent, we have an automatic computor programme called groundspeed mini or G/S mini.

G/S mini is VLS+1/3 W/S - W/S which gives your First Officer a seemingly low G/S of 117 in this example.

BUT

If you take our original VLS of 137 and add 30 kts W/S that would give us an even lower G/S of 107kts.

Does he remember it all now?

One may be tempted to enter a higher W/S into the FMGC but that would give us an even lower G/S mini. However, if you are feeling sensitive about this prior to approach then you can always enter your desired Vapp speed and the correct W/V of course for your new Vref - which are listed in the FCOMs or whatever your country has which is the same as. . .

Therefore bug is Vref which is VLS plus W/S +/- the other stuff of the runway and aircraft perf you may put in = Vref.

Now that he is back on track he knows that all of this is is different to a light a/c whose weight is invariably within the parameters of most of the runways including his speeds. - as a bit of power adhusts the RoD and a an adjustment to the Att gives the required airspeed., plus the spool up time of a light piston prop is much faster than that of a big fat jet engine. The light aircraft being comparatively easier and quicker to re-stabilize whereby in a bigger jet it would result in a go-around but you know this already.
The pre-programming or pro-active calcs are critical for good energy management where Inertia, Kinetic Energy and Potential Energy are all the rage as well as a slow spool up time of large jet-turbine engines.

By making all our calcs, ahead of the game, we arrive at a stabilised approach on glidepath and on speed (stabilised) by a certain altitude (Stable alt) thereby reducing thrust excursions and variations to a minimum.

Its all coming back to him now is it not?

[Kilrah]

Post moved to the appropriate topic.

[Fast Jet]

Vref, tjher is further on Vref, which is derived from VLS to get your Vapp and integrating the wind. The Bug speed being the Vref. Also, the runway data/performance will have been included into the calcs including W.A.T. too.

So, the Vref to which you refer has already had the wind increments integrated into it in order for you to arrive at that final bug figure. Vref.

[Fast Jet]

Post moved to the appropriate topic.

Well, ok, but I was going to remove the typos and was just editing it. . .

[notanastronaut]

your First Officer has fallen into the trap of wanting to re-calc the Vapp - which is not critical as the runway was correctly determined to be long enough. He has forgotten the flight academy rule that your Bugged Vref is derived from your VLS and is your final figure on Approach. You will have got this figure by adding on the W/S onto the VLS which has given you your Vapp and including any further calcs (see later) you may add - increments. So to increase speed above Vref is not necessary at this stage as it has already been done. - by you.

For the benefit of your First Officer - he will remember from his flight academy days that VLS+HWC or derived HWC from XWC / 3 i.e., 1/3rd the W/S = Vapp then with the runway calcs and W.A.T Vapp will be Vref. Notwithstanding how many engines, what systems are up online, what systems are not going to be used for this particular approach.

Now that we have jogged his memory - he will now be doing calcs with a pencil to show you that he knew it all along - I`ll bet he has written an example similar to this:

Landing runway 360 W/V 360/30 VLS 137

So, VLS + 10 (1/3rd of 30) = Vapp [with your other runway perfs in a minute]

So, VLS 137 + 10kts = Vapp 147

Add or subtract increments due to 1 Eng, 2 Eng, 3 Eng, 4 Eng, spoilers in or out reversers out or not plus any asymetrical considerations and Length of Runway, W.A.T. Surface, Slope, / gradient, elev, Wet/Dry/Ice. LDA, LRA, TORA, TODA, Clearway (for any Go Around) plus bits you might add becomes Vref. This being the final figure, pun intended becomes your bug speed.

In the Airbus, which I frequent, we have an automatic computor programme called groundspeed mini or G/S mini.

G/S mini is VLS+1/3 W/S - W/S which gives your First Officer a seemingly low G/S of 117 in this example.

BUT

If you take our original VLS of 137 and add 30 kts W/S that would give us an even lower G/S of 107kts.

Does he remember it all now?

One may be tempted to enter a higher W/S into the FMGC but that would give us an even lower G/S mini. However, if you are feeling sensitive about this prior to approach then you can always enter your desired Vapp speed and the correct W/V of course for your new Vref - which are listed in the FCOMs or whatever your country has which is the same as. . .

Therefore bug is Vref which is VLS plus W/S +/- the other stuff of the runway and aircraft perf you may put in = Vref.

Now that he is back on track he knows that all of this is is different to a light a/c whose weight is invariably within the parameters of most of the runways including his speeds. - as a bit of power adhusts the RoD and a an adjustment to the Att gives the required airspeed., plus the spool up time of a light piston prop is much faster than that of a big fat jet engine. The light aircraft being comparatively easier and quicker to re-stabilize whereby in a bigger jet it would result in a go-around but you know this already.
The pre-programming or pro-active calcs are critical for good energy management where Inertia, Kinetic Energy and Potential Energy are all the rage as well as a slow spool up time of large jet-turbine engines.

By making all our calcs, ahead of the game, we arrive at a stabilised approach on glidepath and on speed (stabilised) by a certain altitude (Stable alt) thereby reducing thrust excursions and variations to a minimum.

Its all coming back to him now is it not?

Thank you Sir. It is important that it comes back to me as well, not only him!!!
ANA

[Fast Jet]

Thank you Sir. It is important that it comes back to me as well, not only him!!!
ANA

ok, here are one or two speeds which wil help. Just put these speeds VLS,Vapp,Vref into a search engine and you can click on the link when it comes up (the address of the document) and you will get a whole group of pages for the A320 or A330 or all the speeds from the JAR ATPL syllabus and also the FAR (FAA) syllabus.

APPENDIX Getting to Grips with Aircraft Performance
210
TOGA TakeOff / Go-Around thrust
TOW TakeOff Weight
V
V Velocity
V1 Takeoff decision speed
V2 Takeoff climb speed
VAPP Final approach speed
VEF Engine failure speed
VFE Maximum flap extended speed
VLE Landing gear extended speed
VLO Landing gear operating speed
VLOF Lift Off speed
VLS Lowest selectable speed
VMBE Maximum brake energy speed
VMCA Minimum control speed in the air
VMCG Minimum control speed on ground
VMCL Minimum control speed during approach and landing
VMCL-2 VMCL two engines inoperative
VMO Maximum Operating speed
VMU Minimum Unstick speed
VR Rotation speed
VREF Reference landing speed
VS Stalling speed
VS1G Stalling speed at one g
VSR Reference stalling speed
Vtire Maximum tire speed
VFR Visual Flight Rules
VMC Visual Meteorological Conditions
WW
Weight
Wa Apparent weight
WC Wind component

Lowest Selectable Speed: VLS
As a general rule, during flight phases, pilots should not select a speed below
VLS (Lowest Selectable Speed), defined as 1.23 VS1g of the actual configuration.
VLS = 1.23 Vs1g g
* The 1.23 factor is applicable to the fly-by-wire aircraft (1.3 for the others).
This rule applies for landing. During landing, pilots have to maintain a
stabilized approach, with a calibrated airspeed of no less than VLS down to a height of
50 feet above the destination airport.
Final Approach Speed: VAPP
VAPP is the aircraft speed during landing, 50 feet above the runway surface.
The flaps/slats are in landing configuration, and the landing gears are extended.
VAPP is limited by VLS:
VAPP ≥ VLS
It is very common to retain a margin on VLS to define VAPP. For Airbus aircraft,
in normal operations, the VAPP is defined by:
VAPP = VLS + wind correction
Wind correction is limited to a minimum of 5 knots, and a maximum of 15
knots. VAPP is displayed on MCDU APPRoach page.
The FMGS and managed speed is used to define the VAPP TARGET. It gives
efficient speed guidance in approach with windy conditions, since it represents:
VAPP TARGET = GS mini + actual headwind
GS mini = VAPP + Tower wind
Actual headwind is measured by ADIRS, and the tower wind is entered on the
MCDU.
When the auto-thrust is used or to compensate for ice accretion on the wings
LANDING
Reference Speed: VREF
In case of failure in flight, emergency or abnormal configuration, performance
computations are based on a reference configuration and on a reference speed. VREF
means the steady landing approach speed at the 50 feet point for a defined landing
configuration. For Airbus, this configuration is CONF FULL.
That gives:
VREF= VLS in CONF FULL
In case of a system failure affecting landing performance, Airbus operational
documentation indicates the correction to be applied to VREF to take into account the
failure:
VAPP = VREF +/- VINOP
Another speed increment can be added to VAPP.

Operators of different aircraft will apply an increase in Vref for flap retraction speeds after takeoff - such as the L1011-1 Tri-Star. So you would have your Vr followed by V2 then flap retract speed for the first stage of retraction would be V2+10 for example or V2 + 20 just for example and these would be bugging up the bug speed after take off. These increments will be maintained or altered depending on the status of the engines and/or systems during takeoff, as you know already.

Hope this helps.

[Ranger]

I'm a simple guy so I'll write a simple post.

Vref is a FIXED number based on the conditions that exist. Vref= 1.3 X Vso. Vso= the stall speed of the airplane in a landing configuration. So ref speed is basically a speed that provides you a buffer from a stall during an approach in a landing configuration . Since it's basically a fixed number you don't "bug up" Vref. Most airlines have established procedures for calculating the final approach speed that they want to fly. I've worked for a company that used Vref + 10 knots and for companies that used Vref + 5 knots. At work, we apply the additive and then call it V approach, or Vapp. Wind additives are applied to Vapp. I could go into the procedures we use for figuring the wind additives but my guess is that it'd confuse most of you. It still confuses me.

I'm more than a bit surprised that an airline crew working an airplane that requires calculating speeds would even be having this kind of conversation. It should have been covered in training and published in their aircraft flight manual or in the limitations. Curious.

[bernoulli]

I'm a simple guy so I'll write a simple post.

Vref is a FIXED number based on the conditions that exist. Vref= 1.3 X Vso. Vso= the stall speed of the airplane in a landing configuration. So ref speed is basically a speed that provides you a buffer from a stall during an approach in a landing configuration . Since it's basically a fixed number you don't "bug up" Vref. Most airlines have established procedures for calculating the final approach speed that they want to fly. I've worked for a company that used Vref + 10 knots and for companies that used Vref + 5 knots. At work, we apply the additive and then call it V approach, or Vapp. Wind additives are applied to Vapp. I could go into the procedures we use for figuring the wind additives but my guess is that it'd confuse most of you. It still confuses me.

I'm more than a bit surprised that an airline crew working an airplane that requires calculating speeds would even be having this kind of conversation. It should have been covered in training and published in their aircraft flight manual or in the limitations. Curious.

Kinda thought you would chime in.

[Fast Jet]

.]

[BMeister]

http://www.youtube.com/watch?v=OaIe-rDN9X8...feature=related

by the way why do they call it 'Bugging' up

[Kilrah]

Probably because the little marks used as a target on the airspeed and altitude ladders are commonly called "bugs"...

[Fast Jet]

by the way why do they call it 'Bugging' up

They are plastic bits like mini arrows around the outside of the instrument - often on the standby airspeed indicator or standby altimeter. you can slide them around the dial to the position of your choice they are often 4 or six bugs. for example, you can bug (move a little plastic mini arrow0 a Vspeed like V1, then bug Vr, then bug V2, then bug V2+10, you brief it several times anyway in your head so you don`t get them mixed up. A previous bug on your dial means you have passed that speed (or alt-titude) but it does not indicate if you have completed the action for that speed or alt - hence you have to be ahead of the game and ready for when the needle on the indicator passes the bugs you have set - example V2+10 could be the time when you call for a flap setting after takeoff for example, so you have to fly the aircraft and watch the bugs too. In the Airbus the bugs come up on the electronic displays. On the approach, for example, if the display tells you to drop flaps FULL and continue the approach at 147 knots after all the information you have correctly put into the computor (FMS) and you decide to fly in at 149 knots, then this is called bugging up Vref, only in reality, you would have put 149 into the computor yourself or come in at selected speed in order to temporarily override the computor - like when you set up the approach from a high altitude. The computor will navigate you around the approach profile accurately but because you have told it you are approaching, it smells the coffee in the canteen inthe terminal and immediately goes down to approach speed. This is perfectly fine but would cause a queue about thirty miles long (and beyond) as the stream of traffic inbound to a busy airport have all now just slowed to the approach speed. So, we tend to select the speeds required during the approach until we are at that place and time where the approach speed is the computed approach speed and then we just hand it over to the computor. during the approach we will have selected a slower and slower speed, like 210, 180, 160, stuff like that. I digress, as usual.

However, before you decide to take up coarse fishing instead, and as Ranger rightly said, Vref is a fixed num which has come off a bug card. The card contains the weight altitude and temperature where you are at, plus maybe other bits and pieces and so you simply pick your card from the pack of cards. As you know how much your aircraft weighs at any given time and you known what the outside temperature is and you know how much all your systems are functioning correctly and also what the conditions of the runway is that you are landing on - icy, wet, dry, short, long, slope, sea level, stuck on top of a mountain in Peru, etc, etc, etc and you pick the bug card of your choice and set the bugs on the dials accordingly and away you go - the aircraft - is now set to land at that aerodrome on that runway during those conditions of altitude, temperature and at that weight. it gets easier the more often you do the same old thing for every approach. Okay?

A meercat could do it - only thing is. . . when you are doing the exams to get there, they don`t let you use bug cards and the like and they expect you to work it all out with a pencil which is laborious and tedius and you have a strict time limit and you are generally starving as you have just paid for the exams.

[AirRabbit]

I’ll join the “Ranger Chorus” on this one, specifically his comment that “I'm more than a bit surprised that an airline crew working an airplane that requires calculating speeds would even be having this kind of conversation.”

In a “no wind” condition it is Vref that you should fly on final approach – and, as Ranger says, this is 30% above the stalling speed for that gross weight and configuration. Some airlines make it a policy to add 5 knots to Vref for final approach speed. If there is any wind present, they usually forego the 5-knot additive and add ½ of any headwind value and all of any gust that exists. This then becomes the speed you fly on final. But, all of those additives (except for the gust value, if it exists) are gradually reduced by the time you cross the threshold. Crossing the threshold is the earliest you should start reducing the throttles to idle for the landing – and after you flare (i.e., reach level flight attitude) should be the latest you begin to reduce the throttles to idle. You should touchdown somewhere below Vref and above Vso – ideally (according to some) midway between the two values. The additions are to protect you during the final approach – but when you don’t need that protection (i.e, as you get closer to landing), you need to adjust your attention to getting the airplane stopped on the runway. Carrying extra airspeed on final where it was a safety issue, becomes a problem when landing. Extra speed pushes you farther down the runway during the final descent to, and during, the flare … particularly if you don’t begin to reduce the power setting until you have completed the flare. Once on the runway, it then becomes a matter of dissipating the energy – and that can be accomplished only through the brakes, the friction of the tires on the landing surface, and the use of reverse thrust (unless you’re a Navy pilot and can depend on the arresting wires). If you touchdown with 10 or 20 extra knots of airspeed, your landing distance will be much longer. If you dally around with the power reduction, your landing distance will be longer. If you hold the airplane in the flare (looking for the grease-job landing) your landing distance will be longer. If you have ground spoilers and don’t use them, your landing distance will be longer. If the runway surface is contaminated (i.e., water, ice, slush, snow, etc.), your landing distance will be longer. And, if you start the landing roll further down the runway because you delayed the touchdown … guess what … you get closer and closer to the departure end of the runway.

“Bugging Up” the speed you fly on final approach is something you do in certain circumstances, but you do it knowing all the risks involved. Professional pilots should not be in a position of having to ask this question on a pilot forum. Learn your airplane and fly it the way it must be flown – and I wouldn’t necessarily take the advice of someone with little experience … particularly when they make a “really good case” for increasing ground speed during final approach.

[Fast Jet]

I loved your post Bugsy.

Espesh` the bit about runway remaining. hope I never get to that point - hey, there was a 73 full of reporters and he elected to land with no reversers due to noise abate - and they ended up in the hedge - nobody got hurt though, well, not physically. I see now in Air Law that to fore-go reversers due to noise abate is now not legal anymore, according to one exam question am doing. . . seems like word got around.. .

You guys must look at Performance "A" on the JAR ATPL subjects. It all in there - including runway performance.

In short - its also in the FAA ATPL studies too and I wonder if the Capt. was really just a clone from the CAA, expecially the `English`. anyway, it was fun sharing my knowledge of Vspeeds and even fun demonstrating that one can find anything under FAL MET SAR AGA COM, en-route supp to name but a few reliable sources or anythingelse by simply knowing where to find the information at any one given time, on the ground, in the air, where-ever. This tiny piece of knowledge was taught to me by my PPL flying instructor all those years ago. We were discussing the A I P at the time and the AICs. Hmmmm.

I would be interested to know - where "I" stand in this merry band of men.

But, instead of it becoming a political topic, maybe it can be a fluid exchange of knowledge - which, in my experience - that is what flying has all been about - a mutual respect - a team of professionals who have the same values and beliefs of flight safety and the same objectives which are and always should be:- To fly the pax/cargo from A to B in the maximum of safety and comfort as cost effectively as possible and cost effective takes a very second place to flight safety in my book and all Captain`s books. The Captain`s inherent task is to avoid hitting other aircraft or the ground inadvertantly, which is his/ her ultimate responsibility.

Also - for some reason, "bugging up Vref" has somehow trans-muted onto the Yahoo search engine - which I discovered when doing my own academic research of V speeds.

So, keep it sweet - your on the net!!!

FROM THEN ON - INTO THE FULLNESS OF TIME - SILENCE REIGNED and we all got wet!!!
"LETTUCE PRAY" - said the Wabbit.

[AirRabbit]

The Captain`s inherent task is to avoid hitting other aircraft or the ground inadvertantly, which is his/ her ultimate responsibility.

Perhaps. But perhaps a more stringent Captain requirement is to Not Hit someone a lot more closely seated.

[Fast Jet]

Perhaps. But perhaps a more stringent Captain requirement is to Not Hit someone a lot more closely seated.

(LOL)

OUCH!!! That hurt MY EAR!!!!!!! (Thats it!! As soon as we land - am phonin` ma mom!! - sulks)

Thank you for watching - next week we discuss Cockpit Resource Management in today`s modern aviation.