slipped

How do u guys explain the difference inpractical terms?

Planespotta

I'll take a stab at it (dons flame-resistant clothing)

Think of Va as the maximum speed at which you can safely stall an airplane without causing structural damage. If you try to stall the airplane flying faster than Va, you will physically break the airplane before reaching a stall (bad thing). During certification, these airplane-destroying forces are measured on the ELEVATOR. When you exceed Va, you risk tearing the airplane apart from control deflections that exceed those which the airplane is rated for.

Vno, on the other hand, has to do with wind gusts measured on the WINGS - NOT forces/structural limits on the elevator. This has to do with the wings getting all bent out of shape (literally) because of turbulent conditions suddenly producing damaging amounts of lift, stressing the wings. When you're flying fast, the wings are "working" with lots of air to produce lots of lift, and it you hit a sudden gust or patch of turbulence, the wings may suddenly find themselves "working with" more air than is structurally safe. When you exceed Vno, you risk causing structural damage because of a sudden gust of wind, rather than elevator/control deflection. This is why you only exceed Vno in smooth conditions, and only then, with extreme caution.

Think of Va as more of a control deflection issue, whereas Vno is more of an environmental/gust issue.

That theory may have a few leaks in it, but it's worked on a checkride or two.

Hope it helped!

abelenky

I'm a student, and could definitely be wrong on this, but my take is this:

Up to speed Va: MAXIMUM control deflection will NOT break the airplane. You can yank-n-bank, and the airplane will still be intact.

Above speed Vno: Flying straight-n-level is okay, but LESS than full control deflection might break the airplane. Minor control input, or even surprise turbulence (with no control input) could conceivably break the airplane.

Of course, I'll defer to more experienced voices here.

**edit:** fixed my description of Vno as Ewfflyer pointed out I had Vno in the wrong spot.

Ewfflyer

Va= Plane will stall before structural damage occurs if any control surface is given immediate and full deflection in any direction. Obviously, the immediate pitch up is the one that will induce the most force and is typically the one demonstrated.

Vno= Green Arc, means life is good. The structural integrity of the airframe should be able to handle normal operating loads in smooth air, as well as light-moderate turbulance(although slowing to Va in moderate isn't a bad idea). Not to mention, most planes out there usually don't have the engine power to exceed Vno in straight and level flight, so another reason it's refered to as Normal Operating. The statement "Even Suprise Turbulence could break up an airplane" is incorrect, unless it would be "severe" turbulence, and you most likely just flew into a thunderstorm.

If you are operating in the Yellow Arc(Vno-Vne), then the onset of turbulence in that speed range could potentially damage the airframe, but even then there are many factors involved that don't guarantee damage will occur(but over time with repeated high-speed flight into turbulence will cause accelerated fatigue).

ryan1234

There's difference between Va (design maneuvering speed) and Vo (operating maneuvering speed)(not Vno)



Here's it from part 23 certification from the FAA:

b. VA should not be interpreted as a speed that would permit the pilot unrestricted flight-control movement without exceeding airplane structural limits, nor should it be interpreted as a gust penetration speed. Only if VA = Vs √n will the airplane stall in a nose-up pitching maneuver at, or near, limit load factor. For airplanes where VA>VS√n, the pilot would have to check the maneuver; otherwise the airplane would exceed the limit load factor.

The idea is that the control surfaces will be structurally sound - it's doesn't really have anything to do with stalling/loads

Va can be higher than maneuvering speed

Stalling vs. limiting load factor is an operating limitation: Vo

rickair7777

Va has several limits. My understanding...

It only applies to the elevator (not aileron/rudder deflection).

It should provide adequate margins for normal maneuvers for the airplane including normal training maneuvers, spin entry/recovery (utility), and aerobatics for aerobatic planes).

It should provide margins for control surface structural failure as well as stalling the wing before wing damage occurs...but I'm not sure that includes slamming the controls back and forth, full deflection.

It may also not apply to aileron/rudder manipulations...it has been clearly demonstrated that rudders can be broken off with large repetitive deflections.

250 or point 65

Va is very commonly misunderstood. It is just like ryan quoted.

Under Va, a full, abrupt, NOSE UP control deflection will result in a stall. Above Va, that same control input could result in structural damage.

Nose down, roll or yaw inputs may or may not be protected below Va.

Cubdriver

Not so fast, that is not always the case. Read the FAA statement again. I suggest making a simple spreadsheet to see how it works- mine is given below. Under Va, there is no guarantee of avoiding structural damage UNLESS the formula agrees the loading is under spec. Note the red values- this airplane may exceed stress loading (n) when loaded lightly. Va is 97 knots at the low end. Max positive n for this airplane, a Cessna 206H, is 3.8.

Va.JPG

Singlecoil

At Va, the aircraft will stall before the positive limit load factor is exceeded. The negative limit load factor can still be exceeded at Va.

The old, "you can push or pull on any control surface and not hurt anything" is totally wrong though you do hear it a lot.

This graph says it all:

ryan1234

It is not required for Va to stall and aircraft when design limit loads are exceeded, nor is it the case for all aircraft.

Some designers make it so that Va is at maneuvering speed - but the thing no one gets is that Va does not have to equal operating maneuvering speed (Vo)

Vo (operating maneuvering speed) is the speed that an aircraft will stall, etc before the design loads are imposed

Va (design maneuvering speed) does not have to have anything to do with stalling - it's part of a certification process which all speeds are based off. It basically just makes sure the control surfaces stay attached to the aircraft.

Here is the FAA Part 23 (a bit more than I last posted) to clear up the confusion:



b. VA should not be interpreted as a speed that would permit the pilot unrestricted flight-control movement without exceeding airplane structural limits, nor should it be interpreted as a gust penetration speed. Only if VA = Vs √n will the airplane stall in a nose-up pitching maneuver at, or near, limit load factor. For airplanes where VA>VS√n, the pilot would have to check the maneuver; otherwise the airplane would exceed the limit load factor.