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Airspeed Question

ChrisHodgens

Active Member
Just wondering how many people fly in the yellow arc, in any model. A friend of mine and myself got into a lengthy conversation about this. He is more experienced in RVs than Myself. I was telling him that it’s not a big deal taking my 8 into yellow in smooth air. He basically said I was an idiot. What are your thoughts?

(My background is 17000 hours in a bunch of stuff, currently SWA. So I didn’t just fall off the turnip truck )

Thanks for the thoughts folks, and merry Christmas!
 
Just wondering how many people fly in the yellow arc, in any model. A friend of mine and myself got into a lengthy conversation about this. He is more experienced in RVs than Myself. I was telling him that it’s not a big deal taking my 8 into yellow in smooth air. He basically said I was an idiot. What are your thoughts?

(My background is 17000 hours in a bunch of stuff, currently SWA. So I didn’t just fall off the turnip truck )

Thanks for the thoughts folks, and merry Christmas!

Your buddy wouldn’t have been happy back in the -200 and -300/500 days! That clacker was a target, not a limitation! Yellow arc? That’s what it’s there for! One thing different about RVs, and you probably know this, is that Vne is now TRUE airspeed, so up high, that yellow arc may have some no-no places..
 
The L1011 was a fast wide body when they were around. I knew of a guy at our company that would fly it even faster. The clacker would sound when you hit the barber pole. If you kept pushing it up, the clacker would stop when you got past the barber pole. If he was running a little late headed back home from across the pond he would push it above the barber pole to try to make his commuter flight home. At least that’s what a friend told me that flew with him. Not real smart, but surprising that the clacker would stop.
 
With caution

My RV-8 requires yellow arc operations to be conducted "with caution and only in smooth air". So I guess if you operate without caution you can not operate in the yellow arc in smooth air. Maybe your buddy does not operate with caution?:D
 
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Agreed Tom, remember the Captain tapping the yoke with a pen when you were slower than the clacker? Haha. Good times.

I haven't been here THAT long. .I got a few months of pulling gear pins, and a few more before the classics went away altogether. I did get to fly a couple of -200s as a side gig a little while ago, one was a former SW bird (N80SW) converted to VIP..
 
Sorry for my OWN thread creep!! Haha

I was really just making sure everyone has the same confidence in the RV design that I do. I honestly feel it’s safe well into the yellow
 
RV's are somewhat "overbuilt" and can take speeds into the "yellow" but should not be taken for granted. Sudden bumps can make your eyes get big! Yellow in SuziQ is 156K/180M. My normal cruise is 150K/172M going through 7-7.5 an hour. Will she GO 200? Yes, but I am sucking 10 an hour. It's fun to push her up there (and, secretly, I think she LIKES it!) just to see her go that fast. But, hey: I'm used to flying a J-3 Cub and going somewhere at 150K is a pretty good clip. Faster than you ought to be driving............
 
RV's are somewhat "overbuilt"...

What makes you think this? This implies that you believe the RV has more “margin” in the yellow than other aircraft. I honestly don’t think the RV tails are significantly over-built in terms of gust margin, and that’s where much of the “structural risk” lies when operating in the yellow and in anything other than smooth air.

Skylor
 
RV's are somewhat "overbuilt" and can take speeds into the "yellow" but should not be taken for granted.

That is questionable logic. The yellow range is where a 50 foot per second vertical gust will cause the aircraft to exceed the rated G loading of the specific plane. Yes, the 6/7 are stronger, but that extra strength is built into the specified yellow range. My 10 has a lower yellow band than the 6, due to it's lower G rating. You should never assume that there is strength built in beyond the rated G loading.

If you are confident that you will not exceed a gust of that magnitude, there is no need to observe the caution. I suspect that is very difficult to predict.
 
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That is questionable logic. The yellow range is where a 50 foot per second vertical gust will cause the aircraft to exceed the rated G loading of the specific plane.

If you are confident that you will not exceed a gust of that magnitude, there is no need to observe the caution. I suspect that is very difficult to predict.

Exactly! Which is why nearly all of my flying in the RV-4 is done well below the yellow arch. The "overbuilt" statement comes from Van allowing for a WIDE range of construction skills in his design of his aircraft. I remember him saying this himself. I am not advocating abusing this and don't in my own airplane. Am I occasionally into the yellow arch? Yes: smooth air cruising. But the lower aspect of the arch and don't like my fuel flow. I am not suggesting consistently flying around in the yellow arch. Is it stupid to fly into the yellow arch, which was the beginning of this thread? No. IMHO.
 
This post has me curious. I don't have a "yellow arc" on my RV9A's EFIS. I do have the maneuvering speed marked, but on a 9 this is a VERY low number - 118 mph (102.5 KTS). The 7/8 is 142 mph.

From the construction manual:
By definition, maneuvering speed is the maximum speed at which full and abrupt controls can be applied. It is also the minimum speed at which limit G-load can be produced.

Yet in the next section is shows the airspeed indicator markings and the yellow arc starts at 180 mph (193 on the 7/8).

Yellow arc: (caution range, to be flown only in calm or light turbulence conditions)

My curiosity is why is there such a significant difference between maneuvering speed and the yellow arc if both are describing similar limits? I know the maneuvering speed is for control inputs, but I was taught that moderate turbulence above maneuvering speed was dangerous as it could have similar effect as full control deflection. Is that an overly cautious interpretation? How do others use maneuvering speed to limit operations in rough conditions?
 
This post has me curious. I don't have a "yellow arc" on my RV9A's EFIS. I do have the maneuvering speed marked, but on a 9 this is a VERY low number - 118 mph (102.5 KTS). The 7/8 is 142 mph.

From the construction manual:


Yet in the next section is shows the airspeed indicator markings and the yellow arc starts at 180 mph (193 on the 7/8).


My curiosity is why is there such a significant difference between maneuvering speed and the yellow arc if both are describing similar limits? I know the maneuvering speed is for control inputs, but I was taught that moderate turbulence above maneuvering speed was dangerous as it could have similar effect as full control deflection. Is that an overly cautious interpretation? How do others use maneuvering speed to limit operations in rough conditions?

Not similar. Va is where full control movement can be applied, as the wing will reach an accelerated stall BEFORE max G load occurs. Once the wing is stalled, further G loading cannot occur. Vno is where a vertical gust can introduce G loading beyond the maximum rating. No relationship to control movement or accelerated stalling. The gust itself is causing the increased G loading. Unsure of the aerodynamics as to why this is speed related, but know that it is.

Va can be helpfull for turbulence, where heavy control inputs maybe required to maintain stability. Vno is all about unknown gusts, which tend to be unpredictable. It is not about control, but surviving the gust itself, structurally. Most turbulence, I believe, is not significant vertical gusting, but more about the abrupt changes in vertical air movement. CAT is quite a bit different than convective turbulence though and may have a higher gusting component.
 
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Not similar. Va is where full control movement can be applied, as the wing will reach an accelerated stall BEFORE max G load occurs. Once the wing is stalled, further G loading cannot occur. Vno is where a vertical gust can introduce G loading beyond the maximum rating. No relationship to control movement or accelerated stalling. The gust itself is causing the increased G loading. Unsure of the aerodynamics as to why this is speed related, but know that it is.

You are right, I confused Va with Vno. So then, Vno would be the number at the bottom of the yellow arc. It is in fact Vno that I was taught about. I guess I'll stop looking at Va when I encounter rough air and use it only before I try a move that would pull the wings off - which is never.
 
Not similar. Va is where full control movement can be applied, as the wing will reach an accelerated stall BEFORE max G load occurs. Once the wing is stalled, further G loading cannot occur. Vno is where a vertical gust can introduce G loading beyond the maximum rating. No relationship to control movement or accelerated stalling. The gust itself is causing the increased G loading. Unsure of the aerodynamics as to why this is speed related, but know that it is.

Va can be helpfull for turbulence, where heavy control inputs maybe required to maintain stability. Vno is all about unknown gusts, which tend to be unpredictable. It is not about control, but surviving the gust itself, structurally.

That is a perfect description of Va!!!
 
don't forget the tail

... Va is where full control movement can be applied, as the wing will reach an accelerated stall BEFORE max G load occurs. Once the wing is stalled, further G loading cannot occur. ...

Va can be helpfull for turbulence, where heavy control inputs maybe required to maintain stability. ...
Va applies to the rudder as well. One point that I was not taught but subsequently learned after reading the NTSB report on AA587 https://en.wikipedia.org/wiki/American_Airlines_Flight_587 is that Va only allows a single movement of the controls, not repeated movements.
 
I guess I'll stop looking at Va when I encounter rough air and use it only before I try a move that would pull the wings off - which is never.

never say never. I once had a very wierd situation at 3000' I immediately began a viscous drop and out of instinct pulled up very hard and almost stalled (much earlier in my flying career). Not sure what it was, but scared the **** out of me. unlike normal turbulence where you tend to gently ride it out, this was so abrupt and instant that instinct took over and I am embarrassed to say, did the wrong thing. Glad it happened in the 6 with its greater G loading.

Another story on Vno. I flew through the top of a Cu cloud in the 10. We had a severe vertical gust that threw me into the cabin top with such force that I felt lucky to maintain consciousness. You just never know and why I try to respect the yellow arc most times.

Larry
 
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Vno is where a vertical gust can introduce G loading beyond the maximum rating. No relationship to control movement or accelerated stalling. The gust itself is causing the increased G loading. Unsure of the aerodynamics as to why this is speed related, but know that it is.
It’s speed related because while a specified vertical gust will cause the angle of attack to increase inversely proportional to your speed, the lift also varies as airspeed squared, so the net is higher speed, higher g load.
Claude: note Vno protects you against the specified vertical gust. Va protects against all vertical gusts, in theory, because the wing stalls first. If you enter a thunderstorm, you want Va, not Vno.
The FAA actually changed the definition of Vno a few years ago, to something more complicated but a better model of actual vertical winds. But in practice it’s pretty much the same.
 
It’s speed related because while a specified vertical gust will cause the angle of attack to increase inversely proportional to your speed, the lift also varies as airspeed squared, so the net is higher speed, higher g load.
Claude: note Vno protects you against the specified vertical gust. Va protects against all vertical gusts, in theory, because the wing stalls first. If you enter a thunderstorm, you want Va, not Vno.
The FAA actually changed the definition of Vno a few years ago, to something more complicated but a better model of actual vertical winds. But in practice it’s pretty much the same.

Thanks for the detail on this. Always looking to expand knowledge.
 
I fly my RV-12 at lower end of yellow arc most of the time. I have Dynon set in MPH so numbers are bigger… :D
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Va Speed

It’s speed related because while a specified vertical gust will cause the angle of attack to increase inversely proportional to your speed, the lift also varies as airspeed squared, so the net is higher speed, higher g load.
Claude: note Vno protects you against the specified vertical gust. Va protects against all vertical gusts, in theory, because the wing stalls first. If you enter a thunderstorm, you want Va, not Vno.
The FAA actually changed the definition of Vno a few years ago, to something more complicated but a better model of actual vertical winds. But in practice it’s pretty much the same.

Something often overlooked is that "POH" Va speed is for gross weight. At loadings less than gross weight, Va needs to be reduced.

Skylor
 
Trying to explain with my words:
Va is the speed at which the max g-load can be produced, further AOA increase will relieve the stress on the wing with a stall. Va is lower with lower gross weight. With lower weight more G´s can be produced at Va and the engine mount or other parts can be overloaded. Staying with the mount, the engine will not change it´s weight with lower gross weight. So Va is always the speed at which max G´s can be produced.
The lower limit of the yellow arc (Vno) will produce max G load with a 50 ft/sec vertical gust. The airframe can withstand higher gusts at lower speeds and less gusts at higher speeds. At Vne a 25 ft/sec vertical gust will produce max G load. So inside the yellow arc the "allowable" vertical gust is anywhere between 25 and 50 ft/sec. And so below that lower yellow limit it is above 50 ft/sec. I don´t know how the 50 ft/sec was established though.
 
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Your buddy wouldn’t have been happy back in the -200 and -300/500 days! That clacker was a target, not a limitation! Yellow arc? That’s what it’s there for! One thing different about RVs, and you probably know this, is that Vne is now TRUE airspeed, so up high, that yellow arc may have some no-no places..

I have read that True airspeed determines Vne in these planes but isn’t TAS taken into account along with maximum ceiling when Vans determined the indicated V speeds? If not, wouldn’t they require a TAS indicator be used?
 
I have read that True airspeed determines Vne in these planes but isn’t TAS taken into account along with maximum ceiling when Vans determined the indicated V speeds? If not, wouldn’t they require a TAS indicator be used?

Things like stall speed, Va, etc., scale like rho-V-squared and thus can be expressed as a single, CAS number, regardless of altitude. Other numbers, like Vy, are more complicated and cannot be expressed as a single number.
 
Remember once above SL yr speedo gets more inaccurate the higher you go.
I don't drive my 8 above 150 kts IAS under normal Ops, I don't see the need to!
It's scary the amount if drivers who don't understand basic aerodynamics!
 
Remember once above SL yr speedo gets more inaccurate the higher you go.

I know what you meant but your indicated airspeed device does not get ‘more inaccurate’ as you climb; it continues to display IAS which is a poor name for dynamic pressure or rho-V-squared. This is useful for avoiding stalls, knowing Va, proper approach speeds, etc. It just isn’t true airspeed.
 
Just wondering how many people fly in the yellow arc, in any model. A friend of mine and myself got into a lengthy conversation about this. He is more experienced in RVs than Myself. I was telling him that it’s not a big deal taking my 8 into yellow in smooth air. He basically said I was an idiot. What are your thoughts?

(My background is 17000 hours in a bunch of stuff, currently SWA. So I didn’t just fall off the turnip truck )

Thanks for the thoughts folks, and merry Christmas!

Fly it like a -200...you'll be alright ;)

Seriously though I would be less concerned with accidentally exceeding 50 fps gusts (which is a lot) in the yellow on a smooth day then hanging out in the green in moderate turbulence for extended periods of time.

Think of all the 152s and 172s that have been terrorizing the sky with students in them for decades get totally abused, and you don't find them falling out of the sky busting the yellow arc on smooth days.
 
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So along these lines do the new Glass Garmin/Dynon/GRT panels have a warning that would tell you you exceeded 50 ft/sec so you could do an inspection?
 
Hi Pete. It’s called a G meter. It can be presented real-time on the screen and is recorded in the 1 second data of most modern EFIS units.

Tom
RV-7
 
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