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GROSS WEIGHT RV-7A

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infltc2s

Member
Happy Easter Gang!


Can someone tell me about Gross Weight on the 7A.
I'm designing the new toy on my computer and trying to decide on the engine choice (IO 360 180 or 200hp)
Spoke with Van's Friday and they said to keep it as light as possible and put a sign over my work area "every ounce counts"
Here is the question:
Does the Max Gross Weight go from 1800 to1950 if I go with the 200 hp engine? After looking around this fourm I found some weight and balance data that shows those numbers. So I'm wondering if those numbers are correct, is the restriction the airframe or the performance of the engine.
 
No, the gross weight does not change with different hp. Gross weight is determined by many things, such as structure, landing gear. etc. Some people increase their gross weight because they have a heavy airplane. This practice is not condoned by the designer and your DAR may question an increased gross weight. He may ask for data supporting the new gross weight.
 
Van's gross weight for the RV7A is 1800lbs. Only if you adhere to this weight will you have an airplane that meets Van's numbers for stall speeds, performance and safety margins. As a tech counselor I see a lot of builders who happily increase the gross wight of their airplanes to compensate for the porked up airplanes they have built. Since there is a good safety margin in Van's numbers a few extra pounds probably will not cause the plane to fall from the sky but you are still compromising a superbly engineered complex piece of machinery.

I have had the opportunity to fly many different RV's of all models except the RV3. The most significant aspect I discovered is that the light ones fly sooo much better than the porky ones. Not only do they get off and climb faster but the handling is much sweeter. RV's are very light airplanes and added weight manifest itself very quickly since it is a greater percentage of the overall weight. Some folks have overbuilt their rides by 200lbs or more and claim that they fly just fine. In comparison with a production single they probably still do but compared to a light RV of the same models they are lead sleds. If you want that RV to be the Ferrari of the skys it is designed to be, suppress that urge to load it up. Like an old aircraft designer once said "throw every part you want to install in that plane in the air, if it comes back down it's too heavy!"

Martin Sutter
building and flying RV's since 1988
 
Mine is 1900lbs

Mine is not particularly heavy, but not the lightest either (1130 I think). I put 1900lbs on it for the sole reason that my Wife and I tend to carry a lot of stuff on camping vacations...So I didn't want to have the insurance Co, the FAA or the NTSB t do naughty things just because I was flying over gross weight.

I have a prop extension too which moves my CG forward so I can load it up behind the seats...within reasonable limits.

Have I yet challenged the 1800lb limit (or likely to)?..Doubtful, I weight around 150 and my Wife is a slender 120 so I just throw gear at it and when I can't get in we have too much...:)

Frank
 
JimLogajan said:
That statement makes sense, but then how do you explain the gross weights listed by Van's for the RV-9A?
Click to expand...
The structure is designed a gross weight of 1750 lb. But, if you have the 118 hp O-235, the performance at 1750 lb would not be that good. This engine is lighter, so you don't need as high a gross weight. Van recommends a 1600 lb gross weight with the O-235 as the best compromise between performance and useful load.
 
JimLogajan said:
That statement makes sense, but then how do you explain the gross weights listed by Van's for the RV-9A?
Click to expand...
The -9[A] has a completely different wing & tail. If I'm not mistaken, the landing gear legs may be different as well (I've heard they are longer than, say, a -7[A]'s gear but I have no data to back that up).

The -9[A] cannot be compared directly to the -7[A] structurally as far as gross weight is concerned.

Back to why some builders bump their gross weight up above Van's recommended #. Let's say for some oddball reason I "need" to take my 300-pound friend as a passenger with full fuel and 50 pounds of parts in back. Let's say his RV broke down and he's stranded otherwise, and I "need" to transport him and some parts back and forth for some reason. In that rare oddball case (that will probably never happen), I'd be over Van's 1800-pound recommended max gross.

Let's say we have an accident. Is the insurance likely to cover us if my airplane has an 1800 max gross and we're loaded to 1930? Am I likely to run up against certificate action from the FAA for operating the aircraft outside the "published" maximum?

Now realistically, in my opinion any insurance company is gonna do the due diligence to discover that my max gross is above & beyond that which Van's, the kit DESIGNER publishes. I would not be surprised if they use that against me...possibly not covering the accident since I as a builder deviated from yadda yadda.

But I would think...at least I wouldn't lose my license.

I guess what I'm saying is...all this hubbub about max gross weight is mostly "intended" to cover your a$$. Whether it's effective at doing so or not, how can it HURT to have a higher NUMBER on paper?

Now...in the case I mentioned above, the absolute "right thing" to do would be for me to say, "Sorry, bud. I can't take us since we'll be over gross. You'll have to find another way." He's SOL and needs to figure something else out. But...yeah, right. How many of us would actually say that?

I would, of course, encourage builders to stick with Van's published numbers. But if I had a nickel for all the RV builders I know who DID stick with Van's numbers, I'd have enough to make one phone call.
 
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I understand what you are saying Dan. But I have certified several hundred RVs, and done TC inspections on hundreds more, and most of them are done at Van's recommended numbers. Maybe people are different in your part of the country.
And I completely agree with Martin, the lighter planes fly MUCH better.
P.S. And you can include the RV-3s too.
 
gross weight

So, at ~1100 lbs dry, how do you add 452 lbs of fuel(42*6), 380 lbs passagers( 2*190), and 100 lbs of baggage and be within the 1800 lbs limit. Above totals 2032. Even at 1050 dry you are still at 1980 lbs
 
Once again...

Bobby1226 said:
So, at ~1100 lbs dry, how do you add 452 lbs of fuel(42*6), 380 lbs passagers( 2*190), and 100 lbs of baggage and be within the 1800 lbs limit. Above totals 2032. Even at 1050 dry you are still at 1980 lbs
Click to expand...

42 gallons of fuel weighs closer to 252 lbs.
 
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