Dad's RV-10

Dad's RV-10

Well Known Member
The GDU-370's (non-Touch G3X) in my new-to-me RV-7 have a lot of parameters that were incorrectly configured - or never configured at all.

Vne was configured as IAS. Vne TAS was blank. The other day, I blanked the Vne IAS field and entered 200 in Vne TAS.

I was looking at that same config page again today and noticed the Vne TAS field was blanked. After playing with it a bit, it looks like the Vne TAS field will not hold a value unless there's a value entered in the Vne IAS field.

Should both Vne IAS & TAS have the same value (200)?
 
From the point of view of the G3X software interface, "Vne (IAS)" is required, "Vne (TAS)" is optional. If you want them both to be the same, enter 200 knots for both.
 
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Vne Configuration

Just to reiterate Matt's comment, IAS based Vne is "required" and TAS based Vne is "optional", in terms of the G3X Touch system.

In the case that a TAS based Vne value is what you need to reference to keep the aircraft within the upper end of airspeed limits, entering a value for both IAS and TAS based Vne can be considered "required".

Thanks,

Justin
 
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g3xpert said:
Just to reiterate Matt's comment, IAS based Vne is "required" and TAS based Vne is "optional", in terms of the G3X Touch system.

For Vans airframes specifically, a TAS based Vne value is what you would reference to keep the aircraft within the upper end of airspeed limits, so entering a value for both IAS and TAS based Vne can be considered "required".

Thanks,

Justin
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Thanks. I was trying to enter only a TAS value, since Vne IAS isn't really relevant for Van's airframes.

But as you point out, the system will not accept a Vne TAS value without a value entered for Vne IAS.
 
I always assumed both TAS and IAS for Vne. Examples where this is relevant is a cold high pressure day. Smooth air, so descend to the airport near the TAS Vne. Except it's 0°f and 30.30. The 200ktas is actually 210kias...oops.
 
Dad's RV-10 said:
Thanks. I was trying to enter only a TAS value, since Vne IAS isn't really relevant for Van's airframes.

But as you point out, the system will not accept a Vne TAS value without a value entered for Vne IAS.
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The RV-12 POH states that Vne is 136 KIAS below 16,000'. Clearly a relevant value not to be disregarded by Van's.

Air doesn't care who's airframe design it's flowing over.
 
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rongawer said:
The RV-12 POH states that Vne is 136 KIAS below 16,000'. Clearly a relevant value not to be disregarded by Van's.

Air doesn't care who's airframe design it's flowing over.
Click to expand...

This is interesting, given that some years ago Vans published a letter (meant to discourage turbocharging) stating that, contrary to most certified aircraft (and far part 23) Vans regarded Vne as a TAS number.
 
I suspect listing the Vne in TAS doesn't meet certain certification standards that Van's intended the RV-12 to meet. The RV-12 is unique among the Van's fleet for the legal standards it is certified under. If Vne in KIAS is the legal requirement, they list the RV-12 Vne in KIAS.

Vne in TAS creates some compromises.
Vne in IAS creates some compromises.
Pick which one is most suitable for the airframe. Maybe the limit is flutter, maybe it's gust load, maybe it's a certification requirement, maybe it's Mach effects (doubtful for our planes).
 
BobTurner said:
This is interesting, given that some years ago Vans published a letter (meant to discourage turbocharging) stating that, contrary to most certified aircraft (and far part 23) Vans regarded Vne as a TAS number.
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I hear you, and I have that letter, but the KIAS Vne limit is right there in book.

David Z said:
I suspect listing the Vne in TAS doesn't meet certain certification standards that Van's intended the RV-12 to meet. The RV-12 is unique among the Van's fleet for the legal standards it is certified under. If Vne in KIAS is the legal requirement, they list the RV-12 Vne in KIAS.

Vne in TAS creates some compromises.
Vne in IAS creates some compromises.
Pick which one is most suitable for the airframe. Maybe the limit is flutter, maybe it's gust load, maybe it's a certification requirement, maybe it's Mach effects (doubtful for our planes).
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A technicality, but not so much IAS as it is CAS. S-LSA certification (ASTM vice Part 23) has the basis of airspeed being Corrected Air Speed, which is IAS corrected for the measuring instrument in the aircraft.

This has a "much ado about nothing" aspect when you are actually out flying in the normal bug smashing altitudes (<12,500'), but the solution is simply to put both in the EFIS and stay within whichever one you choose as limiting.
 
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rongawer said:
,
….but the solution is simply to put both in the EFIS and stay within whichever one you choose as limiting.
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Ron, I very much doubt that 99% of the readers here (myself included) have the flutter knowledge/expertise to make any kind of informed decision. I wish Vans was more candid about their data, but I suspect there are lawyers involved.
 
BobTurner said:
I wish Vans was more candid about their data, but I suspect there are lawyers involved.
Click to expand...

I agree. I should clarify my previous post; absent basis data or technical knowledge to determine which to use for your aircraft, I recommend setting IAS and TAS settings that Garmin, and I believe Dynon, supports. And then adhere to whichever Vne tick is achieved first.

To Van’s credit, at least they do publish a Vne for their designs.
 
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