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RV speed markings: IAS or TAS?

All the limitating speeds on the speedo are to be adhered to bearing in mind that the speedo under reads at altitude. TAS is the only speed used for limitations and for all intensive purposes Indicated is the same as TAS @ SL.
 
Both

Thanks for the replies, the consensus seems to be both!

Part of the reason I asked is to decide whether it is worth marking the ranges on a backup steam gauge. If the values are supposed to be TAS then the mechanical gauge would be misleading because most do not compensate for pressure and temperature to give an accurate TAS reading. The EFIS should be more accurate, assuming I configure it properly.
 
If the values are supposed to be TAS ..

They are not. As noted above, ONLY Vne is in TAS.

And at least some modern EFISes will change redline with altitude (e.g., Dynon), if you configure them that way. I don't know about others as I fly behind Dynon glass.
 
limitations

Thanks; Post #4 above suggests that limitations are at TAS. I interpret limitations to include VNE, VA and Vfe as these are all related to structure. I understand (from reading VAF) that Vans changed from IAS to TAS for VNE however the Vans document that I linked to above is not explicit.
Is there some sort of industry standard that determines which speeds are TAS and which are IAS?
 
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Thanks; Post #4 above suggests that limitations are at TAS. I interpret limitations to include VNE, VA and Vfe as these are all related to structure. I understand (from reading VAF) that Vans changed from IAS to TAS for VNE however the Vans document that I linked to above is not explicit.
Is there some sort of industry standard that determines which speeds are TAS and which are IAS?

As to post #4, remember that this is the internet, anyone can say anything. I re-read #4 and wasn’t quite sure what he meant. But, I don’t speak Australian. -:)
As to an industry standard: For normally certified airplanes, the FARs require all these speeds to be expressed in IAS (or, sometimes, CAS). Placards are allowed (e.g., ‘Vne = 200 kias below 12,000’; Vne = 180 kias 12,000’ to 15,000’; Vne = 160 kias above 15,000’ to service ceiling”). This FAR does not apply to experimental aircraft; nevertheless, I think it is at best confusing that Vans chose to go a non-standard route here.
 
As to post #4, remember that this is the internet, anyone can say anything. I re-read #4 and wasn’t quite sure what he meant. But, I don’t speak Australian. -:)
As to an industry standard: For normally certified airplanes, the FARs require all these speeds to be expressed in IAS (or, sometimes, CAS). Placards are allowed (e.g., ‘Vne = 200 kias below 12,000’; Vne = 180 kias 12,000’ to 15,000’; Vne = 160 kias above 15,000’ to service ceiling”). This FAR does not apply to experimental aircraft; nevertheless, I think it is at best confusing that Vans chose to go a non-standard route here.

Yeah, I didn't understand what he was saying either. And it's "intents and purposes", not "intensive purposes" :). But I digress...

I couldn't find an FAR that required airspeed indicator markings to be in any particular system, BUT...

AFAIK, for GA aircraft, every one I've ever seen or heard of has ASI reading IAS, with V-speed markings accordingly, *including* Vne (redline) for most (in particular, steam gauges), because the old steam gauges couldn't dynamically change a painted red stripe based on altitude, temperature, etc.

With a modern EFIS, Vne can be computed and displayed accurately for any altitude, but (and here's the point I think the OP missed) *all the rest are marked/configured for IAS*. White arc, green arc, yellow arc...all IAS.

Maybe some high-end GA airplanes, or private jets or whatnot use CAS (or even TAS) for some of these, I dunno, but for us...not so much.
 
Discussion

There has been numerous discussions about the reasons for the Vne to be TAS instead of IAS...

Not going to rehash that.

It is really very simple, everything BUT Vne is IAS in these aircraft...
 
Thanks all for the clarification, I'll mark the backup steam ASI bands per the Vans guideline and will probably add a placard that Vne (only) is TAS.

No need for popcorn but it would help clarify things for everyone I think if Vans updated their support document, as per for the RV-14, to show which speeds are IAS and which is TAS (Vne only). Otherwise it's not intuitive to people like me as well as some others who have responded.:confused:

Here's the links to the Vans support documents that I found:
https://www.vansaircraft.com/faq/airspeed-indicator-markings-by-model/
https://www.vansaircraft.com/faq/horsepower-limits-why-not-a-turbocharged-higher-horsepower-engine/
https://www.vansaircraft.com/service-information-and-revisions/n-rv-14-v-speeds/
 
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I couldn't find an FAR that required airspeed indicator markings to be in any particular system, BUT...
.

To answer the above question (normal category planes, not EAB):
14 CFR 23.1545 sections (b)(1) and (c).
As I said, this is not mandatory for EAB but IMHO it would be good if Vans stuck to established standards.
 
Thanks all for the clarification, I'll mark the backup steam ASI bands per the Vans guideline and will probably add a placard that Vne (only) is TAS.

No need for popcorn but it would help clarify things for everyone I think if Vans updated their support document, as per for the RV-14, to show which speeds are IAS and which is TAS (Vne only). Otherwise it's not intuitive to people like me as well as some others who have responded.:confused:

Here's the links to the Vans support documents that I found:
https://www.vansaircraft.com/faq/airspeed-indicator-markings-by-model/
https://www.vansaircraft.com/faq/horsepower-limits-why-not-a-turbocharged-higher-horsepower-engine/
https://www.vansaircraft.com/service-information-and-revisions/n-rv-14-v-speeds/

https://vansairforce.net/community/showpost.php?p=1519920&postcount=16
 
To answer the above question (normal category planes, not EAB):
14 CFR 23.1545 sections (b)(1) and (c).
As I said, this is not mandatory for EAB but IMHO it would be good if Vans stuck to established standards.

Almost, but no cigar. Neither of those (or anything else in there) mentions IAS, CAS, TAS, Mach number, or any other system of measurement.
 
Where Is 23.1545?

First paragraph:
“...section, with the marks located at the corresponding indicated airspeeds.”

So if I go to the current CFR's at https://www.ecfr.gov/cgi-bin/text-idx?SID=6acc80552c160dc2433f081178de89d8&mc=true&node=pt14.1.23&rgn=div5#se14.1.23_12615 I can't even find 14CFR 23.1545. Why isn't it listed there? It's supposed to under Supbart G, but the numbering is different...

This is the site linked on the FAA's website for the current CFR's

What am I missing?

Skylor
 
First paragraph:
“...section, with the marks located at the corresponding indicated airspeeds.”

Fair enough. That's a bit of an unusual way to require IAS (and not CAS, e.g.), but I'll buy it.

You have to then go back to the Definitions section 1.1 to find:

"Indicated airspeed means the speed of an aircraft as shown on its pitot static airspeed indicator calibrated to reflect standard atmosphere adiabatic compressible flow at sea level uncorrected for airspeed system errors"

but (like most FARs, it seems), you're correct.

I knew there was a reason I decided not to go to law school. :)
 
So if I go to the current CFR's at https://www.ecfr.gov/cgi-bin/text-idx?SID=6acc80552c160dc2433f081178de89d8&mc=true&node=pt14.1.23&rgn=div5#se14.1.23_12615 I can't even find 14CFR 23.1545. Why isn't it listed there? It's supposed to under Supbart G, but the numbering is different...

This is the site linked on the FAA's website for the current CFR's

What am I missing?

Skylor

In 2016, FAA revised Part 23 from prescriptive to performative requirements to ease certification burden and encourage new technology to be used to design general aviation aircraft. No longer are you required for example to mark indicated airspeed on the instruments, instead, you must display any markings required by the AFM and "necessary for operation". What's necessary for operation? That's up to you to convince the FAA engineer or DER in a lengthy analysis how you intend to comply with the regulation. This opens the door for example for more aircraft to have TAS limitations in the AFM and be certified with an avionics system that will translate TAS to IAS on the fly. Or you can install a Laser Air Speed Sensor to directly measure true airspeed and fly off of that. As long as you can convince the FAA.

https://www.federalregister.gov/doc...ity-acrobatic-and-commuter-category-airplanes

There's a handy table in there that links the old reg to the new reg. Just search the reg and it'll pop up.
 
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