What is vref speed

Sure, he warns you when he is giving you his personal techniques, but you should always follow your primary guidance Aircraft manuals, government regulations, etc. Please note: Gulfstream Aerospace Corporation has no affiliation or connection whatsoever with this website, and Gulfstream does not review, endorse, or approve any of the content included on the site.

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V REF Aeronautical. Eddie sez:. Last revision: V REF. Regulatory [ 14 CFR 1. That is at least as high a V MCL , minimum maneuver speed in the landing configuration. See Also:. Learning never stops. Copyright Code LLC. It is a number, such as 15 deg. We also learn that the wing stalls at a particular AOA.

That is just a fancy way of saying they are giving you a ratio of the actual AOA in degrees divided by the stall reference AOA in degrees to give you a number between 0.

Yes, the number can actually exceed 1. A fly-by-wire airplane may use a lower AOA to prevent overshoots. An airplane with a conventional stick pusher may do the same to ensure the system activates early enough. We typically think of 1. An example of that could be 1. While far from universal, most aircraft in my logbook flew final approach at an NAOA around 0. The charts and graphs that follow may not precisely reflect your airplane and ignore things like ground and Mach effect, but they serve to illustrate the concepts that you can apply to your aircraft to better understand the principles.

Stall reference speed, Vsr, is determined at 1. Notice that the intersection of our Vref line and 1. This would make a good target NAOA on approach for our notional aircraft.

If the notional aircraft has an alpha limiter or stick pusher that activates at 0. Of course, we do not want to operate below Vref, but this area is available to us in the event of wind shear or another non-normal condition.

This becomes useful to us, realizing that if we see an NAOA greater than 0. Many manufacturers add 5 kt. Imagine yourself flying at 1g at Vref. You are given a margin before stall warning the red zone above the line as well as a maneuver margin. That margin was determined by allowing for a deg. In either case, it would be wise to avoid high angles of attack.

Most pilots are primarily focused on airspeed even if presented with an indication of NAOA. Of course, nothing is ever static on a gusty day and just as we expect the airspeed to bounce around, so too does the NAOA. Our green zone is defined by Vref on the left and the G-loading that equates to a deg. Passing the threshold and entering the flare, it will be OK to go below Vref in calm conditions since we no longer need all of the maneuver margin for the design parameter of 40 deg.

So, it should be apparent that getting below Vref is not a good idea and that when it gets windy, you need to add to your approach speed to avoid doing that. But by how much? Some aircraft manuals say you should add half the steady wind and the full gust increment to your approach speed.

But that is far from universal. Looking at several aircraft from the smallest Challengers and Falcons to the largest Airbus and Boeing jets reveals the breadth of the variation. You might add a half, a third or none of the steady wind, or the headwind. Most will have you add all of the gust. Most will limit you to a 20 kt. The reasons for variation may seem arbitrary but might be more strongly correlated to aircraft design and recommended landing technique than one might suspect.

All aircraft should be concerned with at least the headwind component because of the nature of winds low to the ground. The wind normally decreases as you near the runway, particularly below 50 ft. Adding at least 5 kt. An airplane that lands in a crab may only be interested in the headwind, since sideslip is not a factor.

The reason for including a wind additive to your approach speed is clearly designed to prevent landing with too little stall margin should the winds change. But landing with too much speed presents its own set of problems. If you land with that extra speed, will you still be able to stop on the runway available? Many manufacturers recommend you lose any additive prior to crossing the runway threshold. More on that later. But that will require considerable judgment.

Will this extra speed throw you into a higher approach category? Some aircraft circle at their final approach speed and an extra 20 kt. This could require a higher circling altitude as well as higher weather minimums.

Will the extra airspeed create problems with tire groundspeed limits? Even if your aircraft manufacturer has not posted such limits, the tire manufacturer most certainly has. These limits can be a factor at higher pressure altitude airports, especially on a day with a low headwind component. On a gusty-wind day an additive might bring tire groundspeed limits into play even at lower pressure altitudes.

Will the lower deck angle make it possible to contact the runway nosewheel first? If your airplane flies its final approach in a relatively nose-low attitude, touching down too fast could result in a nosewheel-first landing with the risk of a nosewheel landing gear collapse. Thus the limits to the approach speed additive should take this deck angle limit into account.

For these reasons, and maybe others, some manufacturers recommend you get rid of the airspeed additive prior to crossing the runway threshold. Here again manufacturers differ. Many Boeing, Airbus and Dassault aircraft leave the additive in until the autothrottles retard for the landing.

As noted, some manufacturers recommend the pilot remove the additive prior to crossing the threshold. There are many reasons for caution, but if you decide to lose the additive prior to the runway threshold, how do you do that?

Both methods work. But not always.