1/2 the steady-state wind?

MidlifeFlyer

Well-Known Member
On another forum, there was a discussion of the procedure of adding 1/2 of the gust factor to Vref in gusty wind conditions. In the course of the discussion a pilot (who apparently works for an airline) said that his company's requirement was to add enough airspeed to maintain a ground speed equal to Vref, even in steady-state headwind conditions.

Is that the case? Is there a reason? In a light airplane at least, it would seem the airspeed increase would mean a lot of float.
 
G450 is 1/2 the steady state plus full gust factor up to ref +20 kts. Personally, I think it's too much, but that is in the AFM.
 
The Falcon 900 AFM states the same, half the steady and all the gust up to 20 knots correction above Vref.
 
EMB 145 was half the steady state wind plus 100% of the gust to Vref to determine Vapp, up to "I forget" knots max for Flaps 45 and "I forget plus some more" max for Flaps 22.

When Vapp exceeded Vfe45 for a flaps 45 landing (say, landing in the middle of a tropical storm), Vapp = Vfe45 = 145 knots.
 
Thanks. WAG: the greater mass of these aircraft means less ability to react quickly and a need for greater stall margins. Make sense to anyone?
 
Thanks. WAG: the greater mass of these aircraft means less ability to react quickly and a need for greater stall margins. Make sense to anyone?
Good WAG. Sounds reasonable to me. I would have to dig out Fly the Wing to confirm it.


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EMB 145 was half the steady state wind plus 100% of the gust to Vref to determine Vapp, up to "I forget" knots max for Flaps 45 and "I forget plus some more" max for Flaps 22.

When Vapp exceeded Vfe45 for a flaps 45 landing (say, landing in the middle of a tropical storm), Vapp = Vfe45 = 145 knots.

Saab is pretty much the same.

1/2 the headwind component plus all of the gust. Minumum added to Vref is 10, maximum is 20 to achieve Vfa.
 
Thanks. WAG: the greater mass of these aircraft means less ability to react quickly and a need for greater stall margins. Make sense to anyone?

MidlifeFlyer Autothrust Blue

Our final approach speed provides aircraft controllability and a stall margin within the certified CG envelope in normal or abnomal (ice, malfunction, wind, combination thereof). Paraphrased from our manual
 
To further complicate the issue. We only do it if the autothrottles are off. With autothrottles on, you don't have to worry about it. I've always wondered what the heck sense does that make...
 
MidlifeFlyer Autothrust Blue

Our final approach speed provides aircraft controllability and a stall margin within the certified CG envelope in normal or abnomal (ice, malfunction, wind, combination thereof). Paraphrased from our manual
Makes sense. The jet had a line in limitations that Vref was always higher than Vmcl (we'd certainly hope so). We have separate speeds for ice accretion on our flip cards, so if there's ice on the airplane we fly those instead.

To further complicate the issue. We only do it if the autothrottles are off. With autothrottles on, you don't have to worry about it. I've always wondered what the heck sense does that make...
Autothrottles are better at speed management than humans? (another WAG ;) )
 
To further complicate the issue. We only do it if the autothrottles are off. With autothrottles on, you don't have to worry about it. I've always wondered what the heck sense does that make...

Same policy here too. I think Boeing suggests it... At least they do on the 744/748.
 
In the Dash, we have two separate speeds. Vref and Vrefice. Vref is what you think it is and Vrefice is for ice accumulation on the airframe, gusty conditions, wind shear, etc.

Pretty much everyone flies Vrefice all the time. In the 300 we aren't allowed to fly Vref (only Vrefice) because a of a separate, unrelated (to the conditions above) incident.
 
in the E170, most of the same, 1/2 the steady, all of the gust, min of 5, max of 20

in gusty conditions, I select the auto throttles off, they can't react fast enough and they just constantly try to compensate.
 
To further complicate the issue. We only do it if the autothrottles are off. With autothrottles on, you don't have to worry about it. I've always wondered what the heck sense does that make...

A/T in gusty conditions automatically bump up the speed based on the differential between target and speed change. It is built into the algorithm for the A/T.
 
Half steady state plus all the gust not to exceed 20 kts is pretty typical for about 3/4's of the jet fleet out there.

Dc8 citation II and BE400 all are/were 1/2 the gust. I recall the DC8 going through some iteration of steady state plus something but it was getting to be too much of an additive when each knot over ref corresponded to 100 feet or so of landing roll increase.
 
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