Van's over-engineering compared to certified aircraft

[Snowflake]

Originally Posted by Captain Avgas

I love flying my RV7A...but I?d rather crash a Cessna.

Me too... It'll be going slower.

[2of5]

I recently disassembled a 1946 Cessna 140, down to the individual fuselage frames and skins. I saw no deburring and prep to the standards that the RV assembly instructions specify. Sheared sheets with edges that catch a fingernail, etc. I even found pencil markings used at the factory 73 years ago to mark rivet locations.

FWIW.

[David Paule]

"Over-engineering" is a rather vague term. To some it means over-strength and to others, it approaches the infamous "paralysis by analysis," excessive use of engineering time.

Are the RVs over-strength? Apparently not, from all I've read. They seem to be adequately designed for their mission, without a whole lot of margin. Remember, their mission includes being built by amateurs.

Has Van's wasted excessive engineering on them? Probably not, because they are still in business.

Dave

[gmcjetpilot]

The Vans aircraft (edit) ARE certified and designed for aerobatic category load factors. Cessna's are certified and designed to normal and utility category load factors (which are lower than aerobatic).

Van's aircraft are not "over engineered" or assume you mean over built or stronger than a Cessna. RV's are well designed for intended purposes if flown within limits.

Big difference is in control forces and speed. RV's have very light controls and are very fast compared to a Cessna... so a pilot could overload an RV easier than a Cessna if they are careless or ignorant RV's build speed very fast when pointed down hill and can exceed Vne quickly. The control forces are very light. if the pilot is incompetent or careless, say botched Aerobatics, excessive loads are possible and more likely than a Cessna. Cessna you can't legally do aerobatics, except in an C150/152 Aerobat.

Cessna's are more forgiving and in many ways are a little more robust as well for "abuse loads". An airplane is only as strong as it's weakest structural link. Cessna, can take the pounding of student pilots year after year. The nose gear on RV trike models is not as robust as a Cessna to be sure.... for example.

RV through wing main spar carry through is stout. However a Cessna typically has a strut, also strong.

One is a fast sport kit-plane and the other is a Cessna. Apples and Oranges. Are RV's falling out of the sky? No. Are Cessna's falling out of the sky? No.

[Sam Buchanan]

Originally Posted by 2of5

I recently disassembled a 1946 Cessna 140, down to the individual fuselage frames and skins. I saw no deburring and prep to the standards that the RV assembly instructions specify. Sheared sheets with edges that catch a fingernail, etc. I even found pencil markings used at the factory 73 years ago to mark rivet locations.

FWIW.

Which kinda makes one wonder.......why do RV builders obsess over these build techniques?

2019-1946 = 73 yrs

2019 + 73 = 2092 AD

How long do our RVs need to last?

[RV7A Flyer]

Originally Posted by gmcjetpilot

The Vans aircraft are not...designed for aerobatic category load factors.

Wait, what?

From Van's:

The RV-3B, RV-4, RV-7/7A, RV-8/8A and RV-14/14A have been designed for the operational stress limits of the aerobatic category (+6.0/-3.0 G) at and below their aerobatic gross weights.

[jrs14855]

Originally Posted by RV7A Flyer

Wait, what?

From Van's:

Left out a word. I understand what he intended to say.

[RV7A Flyer]

Originally Posted by jrs14855

Left out a word. I understand what he intended to say.

Good for you! Based on all that followed, it wasn't clear to me the he left out a word at all.

Words *do* matter, after all.

[sailvi767]

One thing I found interesting when researching my first RV purchase was how well the RV6 seems to hold up and the complete lack of any reports of inflight structural failures. They may have been some but I could not find any during my research. The RV7 and to a lessor extent the RV8 have had issues however most appeared to be outside the design envelope of the airframe with possible the exception of the Utah accident a few years ago. The six was probably designed with a slide rule but you would expect the seven to be a improvement.
G

[RV8JD]

Originally Posted by sailvi767

One thing I found interesting when researching my first RV purchase was how well the RV6 seems to hold up and the complete lack of any reports of inflight structural failures. They may have been some but I could not find any during my research. The RV7 and to a lessor extent the RV8 have had issues however most appeared to be outside the design envelope of the airframe with possible the exception of the Utah accident a few years ago. The six was probably designed with a slide rule but you would expect the seven to be a improvement.
G

Don't forget the early RV-3s, before the numerous wing mods. Those accidents were apparently due to poor workmanship, with little margin in the design for that.

Also, there have been more than a few RV-7 in-flight structural failures, but I only recall the Van's factory RV-8 demonstrator coming part in-flight, IIRC. The RV-7 accidents do appear to be outside the Van's-specified design envelope. After an extensive post-accident analysis and test program, the RV-8 was determined to be most likely over-stressed.