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RV-8 V Speeds and Van's "Blue Line"

Saville

Well Known Member
Sorry for the elementary primary School 101 question, but I want to be sure I understand. This is also a lesson I learned in taking things for granted.:

Over the weekend I updated my EFIS so that it showed airspeed in knots rather than MPH (was set to MPH when I bought the plane).

So then I flew some tests and noted indicated speeds - now in knots - of Power Off (clean/Landing Config) stalls, power on stalls etc. with the view of updating the POH.

I also decided to compare the existent settings on the EFIS and POH with the hard values specified in the builder's document. Things like Vfe, Vne etc just to be sure they are correct.

I saw the table shown in the the Thumbnail. I eliminated the values for the other RV's and kept only those for the RV-8, and also kept the MPH values and added my values in Knots.

We can ignore Vso and Vs1 as those values in knots are ones I obtained in last weekend's test flights and are not conversions from Van's MPH values.

Vfe - I was aghast to see that the top of the white arc on the plane was
not the stated 100mph, but 120mph. So that was changed to 87kts
(or 100mph)

I confess to being confused by the "Blue Line" and the Yellow Arc values.

1) I only know of "Blue Line" in multi-engine ops - Vyse.
- Besides which I don't have a blue line marking on my airspeed indicator.

2) I'm trying to differentiate between the "Yellow Arc" in this table and the
"Blue Line". I'm figuring that "Blue Line" means Va (142mph) and the
Yellow Arc runs from Vno to Vne (193mph to 230mph).

Is that the correct interpretation?

If so then I need to placard 123kts (142mph)for Va (no full control deflection),
and set the EFIS yellow arc for 168-200kts (193-230 mph).

Presently my yellow arc starts at 180mph. I have no idea where that number came from. It's conservative from the standpoint of Vno so it's value doesn't scare me like the Vfe value did.

So I learned a lesson in taking settings for granted.

Or maybe I'm misinterpreting these values in which case correction is appreciated.
 

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Blue line in twins is not Vmc.. Blue line is Vyse, best rate airspeed single engine. My guess is that the previous owner had marked a Vy speed? I think most light twins label Vmc by a little red line, don’t they?

Va (maneuvering speed) isn’t marked on any airspeed indicator that I know of..
 
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Blue line in twins is not Vmc.. Blue line is Vyse, best rate airspeed single engine. My guess is that the previous owner had marked a Vy speed? I think most light twins label Vmc by a little red line, don’t they?

Va (maneuvering speed) isn’t marked on any airspeed indicator that I know of..

My error on the blue line = Vmc - changed to Vyse. Thanks

Not sure what speed setting you are referring to when you say: "My guess is that the previous owner had marked a Vy speed?"

Va is placarded I do believe.
 
My error on the blue line = Vmc - changed to Vyse. Thanks

Not sure what speed setting you are referring to when you say: "My guess is that the previous owner had marked a Vy speed?"

Va is placarded I do believe.

I misread your post.. I thought the previous owner had marked a “blue line” on your indicator.
 
Of course Va varies with weight, decreasing as weight goes down.
In a departure from the rules for normally certified aircraft, Vans has stated that their published Vne is meant to be true airspeed, not indicated. Which means the max allowed indicated airspeed goes down, as you climb. Some EFIS units will let you enter Vne as a true airspeed, then calculate where the red line goes on the IAS, based on altitude and temperature.
 
Of course Va varies with weight, decreasing as weight goes down.
In a departure from the rules for normally certified aircraft, Vans has stated that their published Vne is meant to be true airspeed, not indicated. Which means the max allowed indicated airspeed goes down, as you climb. Some EFIS units will let you enter Vne as a true airspeed, then calculate where the red line goes on the IAS, based on altitude and temperature.

Yes Va changes with weight (8083).

I'm asking about what Van means by the "blue line" and if that is meant to be Va.

Do you have any info on that?
 
https://www.vansaircraft.com/wp-content/uploads/2019/02/speeds.pdf

Blue Line
(Maneuvering speed. Maximum speed at which full control can be applied. Speed at which full elevator control would impose loads exceeding limits)


As a practical matter, most think of it as the limit speed for max elevator travel, in order to preclude inadvertent disassembly. Recall early on, Van's lost a demonstrator to an apparent over-G.

It's marked on airspeed indicators purchased from Van's, 123 knots or 143 mph for the -8
.
 

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It's marked on airspeed indicators purchased from Van's, 123 knots or 143 mph for the -8
.

Really? I’d consider that a poor practice, as someone flying below gross weight might think it’s okay to do abrupt control inputs just below that blue line, when in fact he may be over Va.
 
And THAT'S what happens when you don't follow standards and conventions...Van's used a term that is well-known to a large number of pilots and gave it a new (their own) meaning, thus causing confusion. Even more so now that most Van's aircraft being built don't use the old (and apparently custom) Van's gauges anymore, but rather glass panels, and yet it's still there in their documentation. And it's not even correct..."maneuvering speed" is also a function of weight; it's not fixed.
 
And THAT'S what happens when you don't follow standards and conventions...

I tend to encourage markings and operational conventions recognizable to almost anyone transitioning from a Piper or Cessna.

That said, wait about 10 minutes, and a post will come along in which someone will defend the right to build their airplane any way they want. For example, such posts show up a lot in defense of oddball electrical system design. The usual defense is that if the pilot has not learned how to operate that particular airplane, he/she has no business flying it.

Think about it. Van's felt it important to notate a Va somewhat below the yellow arc. It's not typically on an ASI, but putting something there is a darn good idea given the low stick force at aft CG, and the wing removal incident, generally attributed to an unthinking aft meat servo. A line on the airspeed indicator is far from perfect, but it's better than nothing...and it's not a twin. Why should anyone be confused because blue line is also Vyse in a King Air? Per the custom airplane argument (refer to the previous paragraph), you're supposed to know what it means in an RV.

The picture I posted is the 2.25" backup Vans airspeed in my -8. It's visible from the back seat. I point out the blue line to every fighter pilot type before I give them control, making it clear that if they want to die, all they need to do is exceed the blue line and haul back hard. It's an effective reminder. I like it.
 
I like the blue lines too. I put some blue tape at the utility weight and aerobatic weight Va's.

IMG_1521z.jpg
 
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