Va Vs Vno

[cocolos]

Can someone give me a good explanation between them?

 

[ronnieh]

I will take a stab.

Va - design maneuvering speed. Max IAS at a given weight that full abrupt deflection of control surfaces will not cause structural damage. Aircraft will stall first.

Vs - Stall speed or minimum steady flight IAS speed that the aircraft is still controllable. (Vs1 and Vs0 are the stall speeds at certain configurations, simply clean and dirty)

Vno - Maximum IAS for normal operations. Generally the green arc on light aircraft.

I suspect you can Google these terms.

 

[Captain]

Va: Elevator only, not ailerons or rudder.

Ref: AA587

 

[cocolos]

Va: Elevator only, not ailerons or rudder.

Ref: AA587

So Vno is the limit for the ailerons and the rudder?

 

[airguy]

So Vno is the limit for the ailerons and the rudder?

Technically speaking, I don't think any manufacturer has listed a max speed for full deflection of ailerons or rudder. For decades Va was assumed to mean all control surfaces - but after AA587 that changed.

 

[ronnieh]

I think Airguy is correct. It has been more than two decades since I have done any instructing. Things change.

Edit: Actually it is all three but only one at a time as stated by others.

 

[dmspilot]

Va is the maximum speed the aircraft can be stalled without exceeding the limit load factor (3.8g for normal category airplanes).

Vno is based on the maximum speed at which the aircraft can encounter a 50fps vertical gust and not exceed the limit load factor.

 

[cocolos]

Va is the maximum speed the aircraft can be stalled without exceeding the limit load factor (3.8g for normal category airplanes).

Vno is based on the maximum speed at which the aircraft can encounter a 50fps vertical gust and not exceed the limit load factor.

Do you have a reference for this?

 

[dmspilot]

Do you have a reference for this?

14 CFR §§ 23.333, 23.335, and 23.1505

 

[PilotAlan]

Vno is based on the maximum speed at which the aircraft can encounter a 50fps vertical gust and not exceed the limit load factor.

50fps for aircraft certified on or after August 1969, 30fps prior.

The green arc terminates at VNO, the maximum normal operating velocity or maximum structural cruising speed. The formula for calculating VNO is somewhat complex. But one of the formula's factors is the airplane's ability to withstand a specified vertical gust (30 feet per second for planes certificated before August 1969 and 50 feet per second after this date) and not exceed its maximum load limit. - AOPA Airspeed Course

 

[gismo]

Va: Elevator only, not ailerons or rudder.

Ref: AA587

Sorry Captain, but that's not quite correct. Part 23 and 25 require proof that full and sudden deflection of rudder, aileron, or elevator (one at a time) doesn't cause permanent deformation of critical components at or below Va. The AA587 accident brought to light the fact (already clear in the certification rules but not well known in the general pilot population) that this doesn't include repeated and/or alternating control deflections and that's true for all three axes as well.

 

[ronnieh]

And based on another thread I THINK just a single deflection of any surface.

 

[gismo]

And based on another thread I THINK just a single deflection of any surface.

Yes and there are even more specifics than that. The deflection has to occur when the initial motion about the affected axis is zero and static IIRC.

 

[warthog1984]

14 CFR §§ 23.333, 23.335, and 23.1505

Not quite. Va (manuevering speed) is the speed at which the airplane cannot exceed structural load factors before stalling, given a single full and abrupt deflection of one axis control.

In other words, above Va you can still stall the plane safely; below Va any one input (besides CFIT) is physically incapable of permanently damaging the plane since it will stall first and therefore relieve the loading. steep turns and such are thus generally made below Va.

Vno is the "clear air" limit speed above which strong turbulence or specified strong gust is capable of damaging the plane.

So Va protects against pilot error, Vno guards against turbulence. The one exception is that for really strong turbulence I would drop below Va, just in case.

 

[dmspilot]

In other words, above Va you can still stall the plane safely

If you attempt to stall the aircraft above Va, you will exceed the limit load factor. I don't consider that very "safe".