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RV7A Aft CG Restriction

I know this subject has come up many times with regards to the A models and how to deal with the rearward CG tendency.
My query is...based in the UK, when seeking to have the day/VFR restriction removed from an aircraft, the controlling authority places an aft CG limit on the aircraft the same as the recommended aero limit of 84.5". For a normally fitted out touring aircraft it is proving very difficult to fly within this limit.
My question is...in the US, are there any similar restrictions on the rearward CG when operated in IMC? I am trying to find data/justification for the aft limit restriction.
Many Thanks
Derek Cowan
 
Short answer: no.
Longer answer: in the US the government is pretty much hands off experimental aircraft. The builder sets the cg limits, although most have enough sense to follow Vans’ recommendations. The current ‘standard’ operating limits for ifr operations address flight instruments and radio navigation, only.
 
Short answer: no.
Longer answer: in the US the government is pretty much hands off experimental aircraft. The builder sets the cg limits, although most have enough sense to follow Vans’ recommendations. The current ‘standard’ operating limits for ifr operations address flight instruments and radio navigation, only.

And to amplify Bob's great response: As one who flies my RV-7A in hard IFR both light and heavy weight (but always within the Van's recommended CG limits), I have had zero problem trimming up KELLI GIRL and flying the needles. I'd be curious to know why your gov agency has pressed you with this CG restriction. It's just such a non-issue.
 
when seeking to have the day/VFR restriction removed from an aircraft, the controlling authority places an aft CG limit on the aircraft the same as the recommended aero limit of 84.5".

That's weird. What is the reasoning here? Do they not have such a thing as different envelopes for Aero/Utility/Normal?
 
Thanks for the replies guys....this is what I'm trying to figure out, where is the info/data that dictates why the CG is restricted to the rear aero limit (84.5) for IFR/IMC operations. I am awaiting a response to my query to see where we go from here. If the limit sticks at the aero limit it does prevent any comfortably trimmed and equipped 6A/7A from IFR ops two up (forgetting any baggage). Your responses have been helpful...so it is just a UK thing it seems. Van's themselves have been helpful echoing the same response.
Thanks
Derek
 
Yes you are correct, the document you have found does specify the restricted aft CG limit for IFR flight (which is the aero limit) but does not give reasoning. The aircraft is placarded with the normal category CG range for VFR day flight and if cleared for IFR/night then it is re-placarded showing the new aft limit for those flights. But you are correct there is no explanation why. The authority in the UK, the LAA set the CG ranges allowed in our case - not the builder/flyer.
 
Yes you are correct, the document you have found does specify the restricted aft CG limit for IFR flight (which is the aero limit) but does not give reasoning. The aircraft is placarded with the normal category CG range for VFR day flight and if cleared for IFR/night then it is re-placarded showing the new aft limit for those flights. But you are correct there is no explanation why. The authority in the UK, the LAA set the CG ranges allowed in our case - not the builder/flyer.

That's so weird. What if an airplane didn't *have* any other CG ranges defined by the designer? Would they just make them up?

I dunno, maybe you Brits are more likely to go inverted or start doing hammerheads when in IMC than pilots in other countries or something, but that makes no sense to me :).
 
Suspect the “why” is increased static margin. Aircraft certified for IFR have to meet stability requirements. The more forward CG limit increases stability. Someone in the LAA is likely thinking along those lines. It would be interesting to know whether or not an analysis and flight test were conducted or this is simply an example of “most conservative response” conjecture. Since RV’s already have a published aft aerobatic limit, there is a handy number easily available that insures higher stability.

Cheers,

Vac
 
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