When Va is not always Va: Certification standards and Va - Jetcareers

Go to that link for all the technical information you need for understanding the certification basis for Va.


Now I don't think you care to here about published Va having the possibility of being published at a speed other than sqrt (limitloadfactor) * Vs. You did ask for practical terms, I suspect for explaining to a student pilot, not a training aeronautical engineer. Right? :D

In practical terms, maneuvering speed is a speed at which full control movements will result in no structural damage. I've yet to find an aircraft where published Va doesn't equal sqrt (limit load factor) * Vs, so, we can ignore that entire discussion when presenting this to a pilot.

Above Vno can simply be deemed as the speed to operate only when in smooth air. I.E. Smooth air penetration speed.

The limbo occurs with the question: When is there enough turbulence to require flight at Va versus up to Vno? IMO, you don't need to slow down to Va for light turbulence. I consider light turbulence still in the realm of 'normal' with respect to operating conditions. So my answer to this would be:

1. Less than Va whenever you're in stronger turbulence (moderate to be safe IMO).
2. Less than Vno whenever turbulence is light or better
3. Greater than Vno whenever there is no turbulence

I agree, but you should have said positive limit load factor. You can still overstress the aircraft with negative g's at Va. You can pull as hard as you want at Va, but you can't push as hard as you want without exceeding the negative limit load factor. Look at the Vg diagram again. Follow the vertical line down from Va. You will see that it hits the horizontal line (negative limit load factor) before it would hit the curved line (negative load available).

I leave it out intentionally, no sense in adding confusion; for two reasons. Ones is because I can't answer the next question "what is safe for negative G's?". The second is because you also over stress your skull if you ram the yoke forward. This is of course when it collides with twice to three times the weight of your body into the ceiling. This of course won't happen if you have a 5 point belt with a submarine strap, but I haven't seen many non aerobatic aircraft with that.

I'm not even certain you are right, you're basing your analysis on the Vg diagram. Nothing is to say there is enough control throw to even impact that point on the diagram. I do know that the two aerobatic aircraft I've flown had identical Va for inverted and upright flight. We went full controls in all directions at Va. Furthermore, an outside (inverted) loop in a cap 10 is done at 165 mph dual (Va=146).

What is safe for negative g's? How about staying within the design limits of the aircraft? For normal category that would be -1.52g and for utility category that would be -1.76g.
Hop in a 172 and slam the yoke all the way forward and you will most likely exceed -1.52g's.
I agree that it is important to keep things simple. How about this: At Va, you can still exceed design characteristics with control inputs.

I was speaking in terms of what speed is safe for full forward inputs. Giving them the g limits of the aircraft is about as useful as giving them the timing on the spark plug. Without a g-meter no untrained pilot is going to be able to accurately quantify g-load based on feel.

You're saying the same thing, with different wording. However, this wording does encapsulate multiple control inputs, which can cause non progressive and asymmetrical loading. Both of which Va doesn't protect us for. I still don't know with your negative G assessment.

Like I said, in the cap 10 (with a g-meter that recorded max load) I applied full inputs on all surfaces from Va. Our g-limit was not exceeded in any demonstration. My instructor wanted to, with instrumentation proof, demonstrate that Va was safe for all control inputs.

Either way, I still wouldn't nit pick about this with a student. If they fly in a manner where these few limitations might cause them to rip up the airplane, then chances are good they will never get their private pilot license with me. If they already have it, it is only a matter of time till they kill themselves doing something stupid.


Edit: For the record here, I'm not trying to peel appart what your saying to be a shmuck. I just won't tell a student something I can't verify. I also know that basing verification on a graph, without a complete understanding of the factors used to sketch that graph, can quickly lead to inaccurate conclusions. I simply don't know if a negative push will over stress the aircraft and I won't claim to know this based on a graph that I can't derive from pure numbers.