Flying in the Yellow Arc

[RotorAndWing]

Yes, but only one deflection in only one direction. See the NTSB accident report on AA587.

Hence why the A319/320 FCOM has this note:

CAUTION Rapid and large alternating control inputs, especially in combination with large changes in pitch, roll, or yaw (e.g. large sideslip angles) may result in structural failures at any speed, even below VA.

 

[dmspilot]

Actually it's closer to Vne than Vno since you are not supposed to exceed it.

The maximum operating speed (Vmo) on turbine-powered or transport-category is calculated the same way as the top of the green arc (Vno) on a piston.

Someone posted that if a Bonanza is converted to a turbine engine, the yellow arc is removed and the top of the green arc becomes the redline. The above is why.

Also, as Ron says, there is a turbulence penetration speed which is lower but not as low as Va.

Does that contradict anything I've written?

 

[Everskyward]

The maximum operating speed (Vmo) on turbine-powered or transport-category is calculated the same way as the top of the green arc (Vno) on a piston.

Someone posted that if a Bonanza is converted to a turbine engine, the yellow arc is removed and the top of the green arc becomes the redline. The above is why.



Does that contradict anything I've written?

It seemed like you implied that "commercial airplanes" wouldn't slow down in turbulence because their cruise speed was less than or equal to the equivalent of Vno.

 

[dmspilot]

It seemed like you implied that "commercial airplanes" wouldn't slow down in turbulence because their cruise speed was less than or equal to the equivalent of Vno.

Sorry, I didn't mean to imply that they don't need to slow down; just that they were already going "slower" than a piston in the yellow arc. So I only intended to give a reason why Geico's argument was invalid. The turbulence penetration speed you and Ron brought up is another reason.

 

[Everskyward]

Sorry, I didn't mean to imply that they don't need to slow down; just that they were already going "slower" than a piston in the yellow arc. So I only intended to give a reason why Geico's argument was invalid. The turbulence penetration speed you and Ron brought up is another reason.

Ok, sorry I misinterpreted what you meant.

 

[denverpilot]

Things OK at home, Nate?

Frigging autocorrect. ROFL!

 

[Velocity173]

I see your point Ron, but we are not talking about turbulence, the OP is talking about "bumps". Most pilots over exaggerate turbulence. This is actually a real problem for controllers when pilots give PIREPS. Once the definitions of light, moderate, and severe are understood, flying in the yellow "with bumps" is not dangerous, and well within the operating limits of most aircraft. We (as I understand it) are talking about "chop" not FAA defined "turbulence".

Light Chop is reportable turbulence. If I was in it I definitely wouldn't report a smooth ride.

 

[dans2992]

The maximum operating speed (Vmo) on turbine-powered or transport-category is calculated the same way as the top of the green arc (Vno) on a piston.

Someone posted that if a Bonanza is converted to a turbine engine, the yellow arc is removed and the top of the green arc becomes the redline. The above is why.



Does that contradict anything I've written?

So, why does adding a turbine engine make the plane "incapable" of operating in (what was previously known as) the yellow arc?

 

[Henning]

So, why does adding a turbine engine make the plane "incapable" of operating in (what was previously known as) the yellow arc?

Hmmm, I wonder if it has to do with speed at altitude and Vne being a factor of TAS rather than IAS.

 

[PilotAlan]

Why? Yellow arc is to warn against full deflection of flight controls.

Sorry, that's Va (which is not marked on the airspeed indictor), and there's a significant difference in terms of speed (in my bird, Vno is 140mph, Va is 129 at gross and goes down from there).

From AOPA's airspeed course, Vno is:

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.

30fps is not much of a gust factor. I'll stay out of the yellow when there's bumps, thanks. Otherwise, I'm depending on the designers' overload reserve (which decreases over time).

 

[gismo]

Hmmm, I wonder if it has to do with speed at altitude and Vne being a factor of TAS rather than IAS.

AFaIK, it's because turbine airplanes almost always have more than enough power to easily cruise in the yellow arc below 10K. If it were a TAS/flutter issue they'd simply put an altitude based Vne restriction in the limitations (as many turbine powered airplanes have).

 

[Henning]

AFaIK, it's because turbine airplanes almost always have more than enough power to easily cruise in the yellow arc below 10K. If it were a TAS/flutter issue they'd simply put an altitude based Vne restriction in the limitations (as many turbine powered airplanes have).

That doesn't explain why Vno suddenly becomes Vne though.

 

[gismo]

That doesn't explain why Vno suddenly becomes Vne though.

I think it does. The rules turn Vno into Vmo so that the airplane isn't allowed to cruise in what would otherwise be the yellow arc, something that would be easy to do if the limit was higher than it is.

 

[Henning]

I think it does. The rules turn Vno into Vmo so that the airplane isn't allowed to cruise in what would otherwise be the yellow arc, something that would be easy to do if the limit was higher than it is.

I didn't mean rule wise, I meant laws of physics/engineering wise.

 

[gismo]

I didn't mean rule wise, I meant laws of physics/engineering wise.

AFaIK, Newton, Einstein, and Fineman never composed any laws regarding Vno and Vmo. What specific "law" of physics are you referring to?

 

[Marauder]

AFaIK, Newton, Einstein, and Fineman never composed any laws regarding Vno and Vmo. What specific "law" of physics are you referring to?

I think he is referring to the "Law of Carnage". In other words, Vne-1 knots = yellow arc. Vne = Carnage. What created the Vne number? Flutter, control surface departure or some other potential factor resulting in carnage?

 

[Velocity173]

You could still be just below VNE in the yellow, hit light turbulence and your indicated airspeed now goes over VNE. The definition that I know of yellow arc says to operate there in only smooth air and with caution. I don't know of a definition that adds smooth air or light turbulence. If someone wants to operate their 50 yr old aircraft in the yellow arc in turbulence, have at it.

 

[Henning]

Is there a difference between operating in the lower half of the yellow vs the upper half? If I am 5kts into the yellow and I hit a bump will the effect be the same as if I am 5 kts from the top?

 

[Clark1961]

Is there a difference between operating in the lower half of the yellow vs the upper half? If I am 5kts into the yellow and I hit a bump will the effect be the same as if I am 5 kts from the top?

Only if the yellow arc is 10 kts...

 

[Martymccasland]

Only if the yellow arc is 10 kts...

So you're saying the yellow arc gets "yellower"?

e.g. If there's perfect air, sniff on up to Vne (if you dare). If there some light bumps, stay closer to the green side of the yellow arc -- the "pale yellow" arc?

 

[Henning]

So you're saying the yellow arc gets "yellower"?

e.g. If there's perfect air, sniff on up to Vne (if you dare). If there some light bumps, stay closer to the green side of the yellow arc -- the "pale yellow" arc?

Wouldn't that seem to make sense?

 

[jesse]

I don't mind spending extended periods of time (or the whole flight) in the yellow if the air is smooth. Some occasional light chop isn't a concern for me either. If we're getting consistent real turbulence or I'm about to fly where I think turbulence may be (going below the cumulous on a hot summer day) then I will slow below it.

Some of this depends on the airframe to me as well. I personally would not be worried about doing the above in an A36.

 

[Martymccasland]

Wouldn't that seem to make sense?

I'm just someone learning the subject at this point and trying to sniff-out a personal SOP.

Before owning a plane that could easily get deep in the yellow arc, I thought of the yellow as ONLY for PERFECT air. From reading and learning here, I'm seeing that's not necessarily the case... i.e . The increasingly "yellower arc"...

 

[Ted]

Some of this depends on the airframe to me as well. I personally would not be worried about doing the above in an A36.

There's certainly something to this. Bonanzas and Barons are certainly very stout in this area, and I never once saw the Aztec's wings budge. Ever. That included some pretty rough rides. It was also the Aztec, thus slow.

The Commander I was careful with since it did say to stay below 180 KIAS in moderate turbulence (wings have fallen off of them). Of course, it didn't have a yellow arc. In the 310, since I can easily end up in the yellow arc, I am more careful about it.