When Vref

[GravityHater]

What were you all taught about when to fly it on approach?
From established inbound?
From final vector to intercept?
From the OM?
From MM inbound? Vref +10 before then?
Does it depend on the aircraft? The company?
Provisios and caveats, too please - including weather variations.

C'mon you can do it.... "I fly Vref from this point inbound ..........."
C'mon you can suppress your natural desire to be rude; "You dumba$$, you have no right to ask such a stupid question!"!

 

[avbug]

Vref is only a reference speed. It's not necessarily a target. Vref is adjusted for weight and weather; gusty conditions dictate an increase, as does increased weight. Approach speeds are typically higher than ref on final, decreasing to Vref over the fence or at touchdown, with touchdown generally taking place at a value somewhat below Vref.


There is nothing magic about Vref itself. It's a starting reference point for determining how one will conduct the approach with respect to airspeed control.

Alternations to normal approach configurations, such as partial flaps, or speed or lift control devices that have been deactivated or are inoperative, play a part in adjustments to the Vref speed. Increments of knots are added for partial flaps, for example, or if the aircraft is carrying ice.

The specifics of the airplane and the approach conditions, and aircraft weight, determine the reference speed. How it is applied also depend on these factors. There is no need to start an approach at reference speed; usually the approach and landing begins at a higher speed, and gradually decreases to a final value that may never be reached until the runway. Sometimes it may be held until the runway as part of a stabilized approach concept.

 

[2000flyer]

I don't think it could have been explained better. Well done AvBug!

Personally, I'll fly most apporoaches around 140KIAS in either the Falcon or Citation. In the Ultra at lighter weights, ref can be as low as 96-98 knots. I would have ATC jumping all over me at larger airports If I spent the last six miles at less than 100 knots, especially if there is a good breeze on my nose. 140 knots works well as I can slow to Vref at the fence comfortably and touch down close to ref. Anything more than 140 on the approach can lead to floating down the runway or having to plant it in the touchdown zone. Again, this is just a personal tip. Our company requires a stabilized approach. Stablized isn't restricted to "ref" as, as AvBug put so well, will vary with conditions.

2000Flyer

 

[Checks]

Army guy, Vref+20 FAF inbound, once visual slowing to Vref over the threshold.

 

[GravityHater]

Succinct and useful info guys (what is happening to this board?!).

One last Q:
Is there anything unsafe with respect to your proximity to the mca by flying for long periods right at Vref, say for the entire approach?

 

[Sphrynxlla]

If i am flying an approach in IMC to near mins. then i will be fully configured by the OM (ils) and fly the glide slope at vref.....if non precision i will keep flaps 20 and ref +10 until i have the field. .......

If i am having fun on a visual, then i will fly final at 160kts down to the MM....dump flaps chop the power and hit ref over the numbers....works out fine. and its more fun.

 

[2000flyer]

One last Q:
Is there anything unsafe with respect to your proximity to the mca by flying for long periods right at Vref, say for the entire approach?

If traffic isn't a problem, you're the PIC and may fly at whatever speed you wish (within regulation of course).

2000Flyer

 

[Guitar Guy]

Actually, Vref has an important function. It is your target speed at 50 feet above the runway, as per FAR Part 1:

Reference landing speed means the speed of the airplane, in a specified landing configuration, at the point where it descends through the 50 foot height in the determination of the landing distance.

And so there's no confusion, here's the definition of Vref from FAR Part 2:

VREF means reference landing speed.

And from FAR Part 25, here are the landing distance calculation regulations (with certain items not related to this discussion removed):

§ 25.125 Landing.
(a) The horizontal distance necessary to land and to come to a complete stop (or to a speed of approximately 3 knots for water landings) from a point 50 feet above the landing surface must be determined (for standard temperatures, at each weight, altitude, and wind within the operational limits established by the applicant for the airplane) as follows:

(1) The airplane must be in the landing configuration.

(2) A stabilized approach, with a calibrated airspeed of VREF, must be maintained down to the 50 foot height. VREF may not be less than

(i) 1.23 VSR0;

(ii) VMCL established under §25.149(f); and

(iii) A speed that provides the maneuvering capability specified in §25.143(g).

(3) Changes in configuration, power or thrust, and speed, must be made in accordance with the established procedures for service operation.

(e) The landing distance data must include correction factors for not more than 50 percent of the nominal wind components along the landing path opposite to the direction of landing, and not less than 150 percent of the nominal wind components along the landing path in the direction of landing.


Note that the FAR's make a point of the importance of being at Vref at 50 feet above the runway. That means that if one has increased his approach speed above Vref for wind gusts, the landing distance will longer than that determined from the airplane flight manual (AFM) unless that speed additive is lost before crossing the 50-foot-above point. It's also important to note that Vref is not an arbitrary number as indicated in FAR Parts 1 and 25. From a manufacturer's standpoint, they want to make Vref as low as possible to reduce landing field length requirements and to help protect against brake energy margins.

As for my current company, our SOP in the Ultra is to fly the final approach segment at Vref + 10 for straight-in approaches and Vref + 20 for circling approaches with Vref being the target speed at 50 feet above the runway. We will bump up the target approach speed (Vref + 10 or 20) for wind gusts but that does not change the target speed over the threshold.

I hope this helps. I've not added anything about abnormal configurations or contaminated runways, but I hope this helps your understanding of Vref and approach speeds. For what it's worth, I was aircraft performance engineer for 11 years before I started flying professionally.

 

[mar]

Airspeed is life

I suppose it all depends on aircraft and conditions *but* when I was a Metroliner capt it would kinda irritate me when copilots would touchdown on a long (10,000') dry runway right at Vref--especially if there was any wind.

Airspeed is life right? Besides that, the Metro controllability is much better with a little extra airspeed.

Now, if the runway was 4,000' long, contaminated with a slight tailwind component, well, now I'm briefing a touchdown at Vref -5.

Know what I mean?

Fly smart.

 

[Sphrynxlla]

yeh... and v ref really has nothing to do with touchdown speed, if you fly an approach at ref..you will always touchdown under ref if you do a normal flare, but i see what you mean. its all the same as long as your vref 50ft hat... except for that stabilized approach thing.