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RV-3 aerobatic gross weight

randylervold

randylervold

moderator
There has been some confusion about Aerobatic gross weight on the RV-3 ever since the new B wings were introduced in 1998. I spoke with Van himself twice this week on this issue, he in turn discussed with his staff internally, and have now clarified it. Aerobatic gross weight for the RV-3 (all models, all wings) is 1,050 lbs. (no confusion on this). This figure however does NOT include fuel in WING tanks which is what was not clear. Note that any fuel in a fuselage tank WOULD be included in the Aerobatic gross.

Interestingly, he confirmed that this method applies to any RV model. As an RV-8 builder/pilot I interpreted Van's W&B instructions to mean that fuel WAS included in Aerobatic Category gross weight calculations as well as Utility/Normal Category gross weight operation. In fact that is erroneous -- as long as the fuel is in wing tanks it may be excluded from the Aerobatic calculation and limit. Of course Van's points out that weight has other deleterious effects on aerobatic handling and encourages pilots to use good judgement when loading their aircraft for aerobatics.

I have updated the summary of all RV-3 weight & balance data and issues on my web site...
http://www.romeolima.com/RV3works/Info/info.htm#WeightBalanceIssueshttp://www.romeolima.com/RV3works/Resources/resources.htm#WeightBalanceIssues

Informationally,
 
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Wow

Randy,
This is a trememdous piece of information. I wonder why he never said that before.
That is bizzare that it would be left out and never mentioned cause it has not been calculated on 99% of RV's.
hmmm. :confused:
 
Something's funky about that

RV-7 aerobatic gross weight: 1600 lbs.

Fuel capacity: 42 gal = 252 lbs

RV-7 MAX gross weight: 1800 lbs.

Something doesn't line up here if what you're saying is true. Why wouldn't they just call it "max aerobatic zero fuel weight" if that was the case?

)_( Dan
RV-7 N714D (725 hours)
http://www.rvproject.com
 
Kahuna said:
Randy,
This is a trememdous piece of information. I wonder why he never said that before.
That is bizzare that it would be left out and never mentioned cause it has not been calculated on 99% of RV's.
hmmm. :confused:
Click to expand...
I'm with you, which is why I confirmed it with him 3 or 4 times on the phone during our conversations. I asked why they had not made this clear in all of their documentation and he indicated they just "wanted to be on the conservative side". It kind of made me feel silly for assuming fuel was to be included in doing the calcs on my -8.
 
Possible explanation

This is very interesting and I have never thought of it before. I imagine if the center of lift of the wing is close to the center of the fuel load, then it would not put much if any bending stress at the wing root. The load would be transmitted across a very short distance of the spar.

The flight charachteristics would indeed be altered as the more weight you have, no matter where it is, the easier it is to enter an accellerated stall.
 
whifof100ll said:
This is very interesting and I have never thought of it before. I imagine if the center of lift of the wing is close to the center of the fuel load, then it would not put much if any bending stress at the wing root. The load would be transmitted across a very short distance of the spar.
Click to expand...

If we had a wing tank that went down the whole wing span, had a constant size at each spanwise location, and we had no dihedral, then each spanwise location would carry the load of the fuel at that location. An increase in fuel load would not increase the spar bending moments. But this is not true with RVs, as our fuel tanks are not like that.

The centre of lift is somewhere around mid-span of each wing panel, and the RV fuel tank is more inboard than that. And, if you only have a partial fuel load, there is more fuel in the inboard end of the tank than the outboard end, due to the dihedral. So, adding fuel in an RV does increase the wing spar bending moments just outboard of the fuel tank, as the outer wing has to help carry the fuel load.
 
More funky numbers

dan said:
RV-7 aerobatic gross weight: 1600 lbs.

Fuel capacity: 42 gal = 252 lbs

RV-7 MAX gross weight: 1800 lbs.

Something doesn't line up here if what you're saying is true. Why wouldn't they just call it "max aerobatic zero fuel weight" if that was the case?

)_( Dan
RV-7 N714D (725 hours)
http://www.rvproject.com
Click to expand...

I agree that this does seem a bit odd.
RV8A empty wt = 1034 lbs
well-fed pilot = 200 lbs
well-fed pax = 200 lbs
lots of baggage = 116 lbs
-----------------------------
total wt = 1550 lbs = max aerobatic zero fuel weight

so, add on some fuel: (1800 lbs - 1550 lbs)/6lb/gal = 41.7 gal !!

Aerobatics with passenger and baggage and full fuel...?
Not in my airplane.

Was there eggnog involved in this max aerobatic weight decision? ;)
 
Gross Weight

I have seen listed gross weights for both the -A and -B all over the map.

Can anyone explain why there would be differences from what Vans has published.
 
Pave Tim said:
I have seen listed gross weights for both the -A and -B all over the map.

Can anyone explain why there would be differences from what Vans has published.
Click to expand...

The designer recommends a gross weight, then the manufacturer picks what he/she wants. That's how it works in the USA.

Tony Spicer, RV-3B manufacturer, 360 wonderful hours with no lights, no autopilot, no cs prop, 800 lb empty, 1250 lb gross
 
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