NEW V/S Modification video Anti-Splat-Aero

[krw5927]

Originally Posted by David Paule

With this part installed, can the original part be inspected for cracks?

Dave

Ding ding - we have a winner! This is the singular biggest issue here. You're covering up a known potential failure point and preventing ongoing inspection. The good news is that the plates don't appear to be too difficult to un-bolt every hundred hours or so to continue inspection.

[Andy Hill]

Allan...

Just a comment, your website states:

Though to our knowledge, no tails have fallen off yet

which does not seem to equate with C-GNDY TSB Report

It is way beyond me to judge the effect of such a mod in this accident, whether positive, negative or no effect. Just altering the stiffness of any component v flutter is an area I would not wish to pass comment on.

However, I do note that the V/S did not separate in the area of this mod, but in the spar just above this attachment plate (p6):


So whilst I have no doubt it 'adds considerable strength', (and adds stiffness), I am not sure it is in the "weakest point", and so I am not sure about the validity of 'and much peace of mind into the equation'?

[PerfTech]

Originally Posted by David Paule

With this part installed, can the original part be inspected for cracks?

Dave

....Yes! You can see the opposite side and both edges, also if you wish it is easily removed to look at the front side. The bottom line is you don't even need the original piece to be in tact as the new one is several times stronger and much tougher. By using the layered assembly the possibility of the tail departing is pretty much impossible. Thanks for the good question. Allan...

[LifeofReiley]

Dammitt Allan... Thanks for taking the beating and keep on ticking with the Great Ideas!!!

[PerfTech]

Originally Posted by krw5927

Ding ding - we have a winner! This is the singular biggest issue here. You're covering up a known potential failure point and preventing ongoing inspection. The good news is that the plates don't appear to be too difficult to un-bolt every hundred hours or so to continue inspection.

...When in the process of doing an annual inspection, if concerned this is easily removed. Getting the intersection fairing off is far more difficult than removing these two brackets one at a time. You are correct stating that we are covering a possible known failure point with a mod that will make this a non failure point, as long as it is in place. That is the idea and purpose of this part.
If your original bracket from Vans is not cracked when the add-ons are installed, you will never see a crack form. Thanks for the question. Allan...

[rvbuilder2002]

Originally Posted by PerfTech

By using the layered assembly the possibility of the tail departing is pretty much impossible.

I wouldn't go that far....

It is probably not obvious to someone not familiar with the load paths in aircraft structures, but nearly all of the load induced in the vertical stab is translated to the fuselage through the rear spar.
That is why it is a continuous assemble with a .125 thick doubler on it.

Case in point - The RV-10 (and now the 14) have a single 1/4 inch bolt for the fwd spar attach link.

[PerfTech]

Originally Posted by Andy Hill

Allan...

Just a comment, your website states: which does not seem to equate with C-GNDY TSB Report

It is way beyond me to judge the effect of such a mod in this accident, whether positive, negative or no effect. Just altering the stiffness of any component v flutter is an area I would not wish to pass comment on.

However, I do note that the V/S did not separate in the area of this mod, but in the spar just above this attachment plate (p6):


So whilst I have no doubt it 'adds considerable strength', (and adds stiffness), I am not sure it is in the "weakest point", and so I am not sure about the validity of 'and much peace of mind into the equation'?

...We were well aware of this accident and as stated before, this tail didn't fall off. It was sheered in half from surface flutter caused by balance issues and over speed. This plane was seeing speeds well over 280 MPH and recorded dives in excess 12,000 FPM. This is far and away beyond the design limits of this airplane and the outcome is predictable and pretty much what Vans cautions can happen. This failure is in no way even related to the subject of the V/S mounting bracket or the modification we are offering. Thanks , Allan...l

[LifeofReiley]

Originally Posted by rvbuilder2002

I wouldn't go that far....

It is probably not obvious to someone not familiar with the load paths in aircraft structures, but nearly all of the load induced in the vertical stab is translated to the fuselage through the rear spar.
That is why it is a continuous assemble with a .125 thick doubler on it.

Case in point - The RV-10 (and now the 14) have a single 1/4 inch bolt for the fwd spar attach link.

Would not go that far with it, two cases known now with a failure at this point on airplanes. I know of two law suits in play at this time dealing with failures at the same point.

[Andy Hill]

Hi Allan...

Thanks for the reply. Sorry if I ask one or 2 more questions / make one or 2 more statements:

...We were well aware of this accident and as stated before, this tail didn't fall off. It was sheered in half from surface flutter ...caused by balance issues

Sorry, not my reading. Flutter was a possible factor. The rudder had possible balance issues, and split in half. The VS remained largely intact (see photos).

and recorded dives in excess 12,000 FPM ... This is far and away beyond the design limits of this airplane

I am not sure this is beyond the design limits of the RV-7? It is 125K in the vertical, something many RV pilots do on many days.

The fractures in the vertical spars occurred just above where the spars fastened to the fuselage. The fracture surfaces were consistent with faiure by overstress. There were no indications of progressive failure.

So the VS Spar(s) were determined the have failed due overstress, not flutter (I am not saying flutter did not occur, but if it did, it was the trigger, but the failure was due overstess).

This failure is in no way even related to the subject of the V/S mounting bracket or the modification we are offering.

OK - what exactly is the bracket offering that now enables you to flick / side-slip as you state?

When in a hard slip, rapid yaw movements, any aerobatic maneuver that ads stress to the V/S like snap rolls or worst case point rolls or knife edge flight this area is really stressed to the limits

Though to our knowledge, no tails have fallen off yet, we think it prudent to be sure this potential point of failure is eliminated

seems incompaible with

...We were well aware of this accident and as stated before, this tail didn't fall off

Maybe I am just unfamiliar with the "structural failure mode" of "falling off" as opposed to failing by overstress (in defined directions / types e.g. shear) or fatigue etc.?

Please do not get me wrong, anything that adds to the safety level of RVs, and in an area I do a lot of flying (aerobatics etc.) is great. The HS/VS attach and structure is clearly one concern. Here in the UK, the RV-8 was delayed aerobatic clearance for exactly such concerns until additonal testing was performed. All I am asking though is exactly what failure mode (and where) has been determined as most vulnerable that this product overcomes? Your text above repeatedly refers to "stress", and the TSB assessed this attachment area failed "due overstress". The 2 therefore seem directly related - but the mod does include the failure point?

Given your

this area is really stressed to the limits....accomplishes this beef-up in just a few minutes

can one ask, in figures or even just %, what the load increase of this "beef-up" is, in terms of the calculated ultimate load for the VS (as a whole)?

Have you approched Vans and asked them what calculations or testing was done on the (somewhat generic) VS attach area, and asked where the failures occurred, or were predicted to occur? The pictures to me suggest a fairly clear story - the VS was subject to a left/right load, and failed (as one might expect) where the structure was at it's weakest. Forward this seems to be the single spar at the rivet hole line (just above your mod area), and the aft spar at the attach bolt holes (where there is no doubling of plates etc.)

[rvbuilder2002]

Originally Posted by LifeofReiley

Would not go that far with it, two cases known now with a failure at this point on airplanes. I know of two law suits in play at this time dealing with failures at the same point.

-d- ? Reiley

"I know of", with out any specifics is not of much value.