Max structural speed vs Vne

I_WANNA_BE_ATP

New Member
I did a search and didn't find anything. Asked a CFI and he was like "they are the same" Not going back to him.

But what is the difference between the two?? And anyting else you can think of to post.

Thanx!
 

esa17

Well-Known Member
Are you talking about Vno which is Max Structural Cruising Speed and Vne? I hope there aren't CFI's out there who don't know the difference.
 

BobDDuck

Island Bus Driver
And just to make things more confusing there is also Vdive which is normally Vne+17% or so (I think) and while the aircraft doesn't have to be stable at that speed, it needs exhibit enough controllability to return to Vne or less.
 

I_WANNA_BE_ATP

New Member
Are you talking about Vno which is Max Structural Cruising Speed and Vne? I hope there aren't CFI's out there who don't know the difference.


Yes, sorry, at work trying to catch up on jc and ask questions while trying to keep my one patient off a ventilator.

Oh and he is a graduate of a cookie cutter school.
 

kgflyboy

New Member
Vno is the maximum structural cruising speed, which should never be exceeded except in smooth air. Vne is the speed which should never be exceeded, regardless of how smooth the air is. Operating above Vne can result in structural failure or damage to the plane.
 

tgrayson

New Member
I did a search and didn't find anything. Asked a CFI and he was like "they are the same" Not going back to him.
In somewhat of a defense of the CFI, "Maximum Structural Cruising Speed" is poorly named. If you just look at the words, you might easily draw the conclusion that it's something other than what it is.

Vne is the red arc on the airspeed indicator, and it's set mostly with a comfortable margin above where flutter might develop on an aircraft's flight controls. In a flight testing book I have, the author was doing dive tests on a Commander 112. The airplane literally fell apart around him and he had to evacuate the airplane using his parachute.

Vno is the top of the green arc. For all speeds at or below that speed, the aircraft can encounter a 50 fps vertical gust without exceeding the load factor limit. This is why they say to only exceed this speed in calm air. Still, I read an article the other day about a guy in a Saratoga doing a yellow arc descent and encountered wake turbulence from a jet crossing his path. The airplane broke apart.
 

matt152

Well-Known Member
Operating below Vno but above Va can also result in structural damage if the load factor limit is exceeded.

There is a good writeup in the Pilot's Handbook of Aeronautical Knowledge. But a picture is worth a thousand words:

 

mjg407

Well-Known Member
This is why they say to only exceed this speed in calm air. Still, I read an article the other day about a guy in a Saratoga doing a yellow arc descent and encountered wake turbulence from a jet crossing his path. The airplane broke apart.
The speeds are based on a brand new airplane with 0 hours fatigue or stress placed on the structure. As airplanes age (as we are finding out with our airplane) fatigue cracks begin to develop in places and many times the Vne and Vno speeds need to be adjusted from what the manufacturer originally put out. I also don't think (but I don't know for sure) that regular GA airplanes aren't evaluated structurally later in their life.
 

I_WANNA_BE_ATP

New Member
Thanks, that is what I thought it is and when we got discussing them he confused me a bit. (not that hard as geezerpilot would say).
 

esa17

Well-Known Member
The speeds are based on a brand new airplane with 0 hours fatigue or stress placed on the structure. As airplanes age (as we are finding out with our airplane) fatigue cracks begin to develop in places and many times the Vne and Vno speeds need to be adjusted from what the manufacturer originally put out. I also don't think (but I don't know for sure) that regular GA airplanes aren't evaluated structurally later in their life.
You are correct. I'm not aware of any GA aircraft with a limit of validity on their engineering data. To that end, when you hear her creak, stop pulling! :D
 

tgrayson

New Member
As airplanes age (as we are finding out with our airplane) fatigue cracks begin to develop in places and many times the Vne and Vno speeds need to be adjusted from what the manufacturer originally put out.
Agreed. It's not prudent to fly to the very limits of published capabilities.
 

SpiraMirabilis

Possible Subversive
Operating below Vno but above Va can also result in structural damage if the load factor limit is exceeded.

There is a good writeup in the Pilot's Handbook of Aeronautical Knowledge. But a picture is worth a thousand words:

I was under the impression that an aircraft would exceed the critical angle of attack and stall prior to exceeding the load limit factor if operated under Vno.
 
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