Mitragorz

Correct, but you just said "Va decreases with weight." You didn't specify an increase or decrease with weight, but when someone says "X decreases (or increases) with Y" it's assumed that Y is increasing. At least that's how I've always seen in presented. Could be a regional (geographical, not airline) thing. Like "Air temperature decreases 2C with every thousand feet" or "Air pressure decreases with altitude."

Although I guess after re-thinking the way you said it, I picture weight "with" Va, holding hands and strolling down a merry decline together. So yeah, Va would be decreasing with weight . So i guess you could say it like that too. I just never heard that kind of statement worded that way.

Just didn't want to confuse the guy. When I read what you wrote, I assumed you meant an increase in weight. Just a matter of semantics, I guess .

ryan1234

So what if the aircraft moves into another category. For example, light cessna moves from normal into utility?

NoyGonnaDoIt

No, you're right. My explanation should have been clearer.

NoyGonnaDoIt

Huh?

Maneuvering speed is a structural-related limitation. I'm not sure that it does change with the aircraft's category. The general rule that the max gross weight number is always listed (if there's only one number, it's for max gross). Listing others is pretty much optional, although airplanes that have a wider range of possible weights will tend to list more since Va for 6-seat airplane with lots of fuel and baggage capacity will be significantly lower when someone flies it solo with only a headset and a kneeboard with only 1 hour of fuel left. So I guess that if utility category means less max gross, a manufacturer might well opt to list a Va for max weight when operating in that category.

btw, I don't think anyone mentioned it, but the formula for calculating maneuvering speed (or any load limited V-speed for that matter) at any weight is

V1=V2 * Sq Root (W1/W2)

Where:
V1=Airspeed being calculated
V2=Published airspeed for a given weight
W1=Weight for which airspeed is to be determined
W2=Gross weight for which airspeed is published

ryan1234

Va for light aircraft, the manufacturer bases it on load limit factors. Going from category to category changes the load limit factors (3.8normal to 4.4utility). A 4.4 load limit will allow more airspeed at less weight. Notice how 172s' are placarded with "Va = 105". The safety factor is 1.5 for structural items.

Usually the formula used for (light aircraft manufacturers) Va is Va = stallspeed * sqrt(limit positive load limit factor)

One thing to consider doing, let say aerobatics, is that certain high-g maneuvers require a higher entry speed than Va. Of course these maneuvers are symmetrical, but it really just depends on the amount of residual energy. I think Assymetrical loading has a little more to do with a Vd/Va interpolation.

Cubdriver

It's been a few years since I've done one, and we did them ad-nauseum in aersopace college of course but a given manufacturer submits a "VN Diagram" for a new airplane design to the FAA or their designate which must be approved. V stands for velocity in feet per second, and N is load factor. It looks like the ones you see in pilot textbooks, but with a gust envelope added as well, see diamond shaped envelope shown in this one:

shdw

Just in case we have some european readers, ultimate load factor for them is two times limit load factor for their certifications.

To clear this up since I have had a bunch of questions arise from speaking of limit load and ultimate load factor:

Limit load factor = the published g limitations in your POH and the point where structural damage can occur.

Ultimate load factor = as Ryan said, in the USA 1.5 times limit load or two times it in Europe. This is the point where structural damage is certain and items may begin to come off the aircraft. Ryan: Is it may come off or will come off at ULF? I can't recall for certain.

ryan1234

I have really no idea at all.... my only slightly educated guess would be that it is based off the "weakest link" - that is maybe the wings will hold on but the engine mounts might go or vis-a-vis... or maybe it's when detectable damage occurs.

USMCFLYR

We just got a Ops Bulletin regarding Va again and thought I would share it.
I re-read this thread before posting and agree that there certainly is some confusion

From the Special Airworthiness Information Bulletin (Jan 18, 2011):
USMCFLYR