RV Horizontal Stab Rear Spar SB…

[Notatestpilot]

Regarding this latest bulletin from Vans, I believe it has to do with the affected rivet holes not adequately deburred.
I have seen the effects of aluminum structure that wasn’t being properly filed smooth and surfaces finished. The results are these ‘stress cracks’ that emanate from corresponding part.
This is just my opinion though…others may disagree.
However, this is no different than the other SB they had on the HS front spar from 10 plus years ago.

 

[nauga]

However, this is no different than the other SB they had on the HS front spar from 10 plus years ago.

Yeah, no different...other than the location, loads, dynamics, and timing. At least the new one gave me an excuse to buy a borescope.

Nauga,
compliant - and no cracks

 

[tsts4]

While I’ll agree that stress risers as a result of improper hole prep could definitely be a cause, I would be hesitant to say it’s the one and only cause without some empirical data.

 

[Bell206]

The results are these ‘stress cracks’ that emanate from corresponding part.

FYI: the cracks tend to be a secondary result as any burr left in the hole will cause the rivet (or other fastener) not to seat 100% flush or worse it causes a reduced "clamping" pressure of the rivet. Over time the rivet loosens which in turn causes asymmetric load paths in the hole leading to a stress crack forming along the rough (non-deburred) edge. There've been ADs issued over non-deburred holes in the past.

 

[Notatestpilot]

Unfortunately, in our EAB world, when one builder's poor/lack of craftsmanship, we pay the price!!

 

[kyleb]

I believe it is cyclic fatigue driven by the elevator hinge moment. That moment is reacted across a relatively small distance, creating high cyclic loadings. Given the language in the service bulletins, I think this is more about insufficient fatigue margins than build quality issues.

 

[hindsight2020]

Unfortunately, in our EAB world, when one builder's poor/lack of craftsmanship, we pay the price!!

*fac-built has entered the chat*
*ERAU has entered the chat*
* @hindsight2020 has left the chat*

 

[Notatestpilot]

If that's a possiblity then why not inspect the right side rear spar outboard hinge too.
If its cyclical fatigue then the highest time rear spar web should be cracked too...however, that's not the case.
Respectfully, I disagree with your statement.

 

[kyleb]

If that's a possiblity then why not inspect the right side rear spar outboard hinge too.
If its cyclical fatigue then the highest time rear spar web should be cracked too...however, that's not the case.
Respectfully, I disagree with your statement.

It IS the rear spar. The spar at BOTH outboard hinges-left and right.

 

[Notatestpilot]

To my point, then the highest flight time HS should be cracked...not the case though.
NOT THE CASE!

 

[Notatestpilot]

It IS the rear spar. The spar at BOTH outboard hinges-left and right.

To my point, then the highest flight time HS should be cracked...not the case though.
NOT THE CASE!

 

[kyleb]

To my point, then the highest flight time HS should be cracked...not the case though.
NOT THE CASE!

It very much depends on the usage of the airplane. Airplanes that have been subject to the most acro (and the resulting elevator forces) would be more susceptible than airplanes with a history of straight and level.

 

[nauga]

To my point, then the highest flight time HS should be cracked...not the case though.
NOT THE CASE!

Do you think flight conditions and maneuvers have any bearing on cyclic loads at all or is it simply airframe time that results in damage?

Do you think cracks on the elevator spar at the hinges (SB14-02-05) are also simply the result of poor workmanship and if so why does this poor workmanship seem to be confined to the elevator hinge area?

Nauga,
who can't always lead the horse to water

 

[Notatestpilot]

Do you think flight conditions and maneuvers have any bearing on cyclic loads at all or is it simply airframe time that results in damage?

Do you think cracks on the elevator spar at the hinges (SB14-02-05) are also simply the result of poor workmanship and if so why does this poor workmanship seem to be confined to the elevator hinge area?

Nauga,
who can't always lead the horse to water

I’ve been reading some comments on the VAF forum and there’s an RV4 with 2000 plus hours in competition aerobatics. He found no cracks!
I still say it’s partly craftsmanship including many other factors.
I don’t plan to order the repair kit from Vans and unzip my HS anytime soon.

 

[tsts4]

I don’t plan to order the repair kit from Vans and unzip my HS anytime soon.

Me neither. This SB just got added to my list of 4 other SBs that gets complied with every condition inspection. I should note that all 4 SBs that I’ve been inspecting prior to this one also deal with potential cracks and 2 are also hinge brackets (bottom rudder and inboard aileron).

 

[Notatestpilot]

Since I started this post, just one more point if I may...
The RVs are the most prolific EAB of all time. As such, the basic skill - the craftsmanship is 'so' overlooked that the focus is on the multi-screen color displays in the cockpit. When I read further into a builder's completion story, its mostly outsourced - to an avionics shop. The airframe is a 'quick build'. The paint is sprayed on by some well known shop for $8000. The only parts that's touched by the builder is the empennage - no wonder its also the origin of the structural service bulletin(s)!
BTW, I've lived in many states (over a dozen airports) and I can say there are a number of builder assistance services. Given RVs popularity, many builds are actually from these 'assist' shops.
That's our world - we want instant gratification.

 

[tsts4]

Since I started this post, just one more point if I may...
The RVs are the most prolific EAB of all time. As such, the basic skill - the craftsmanship is 'so' overlooked that the focus is on the multi-screen color displays in the cockpit. When I read further into a builder's completion story, its mostly outsourced - to an avionics shop. The airframe is a 'quick build'. The paint is sprayed on by some well known shop for $8000. The only parts that's touched by the builder is the empennage - no wonder its also the origin of the structural service bulletin(s)!
BTW, I've lived in many states (over a dozen airports) and I can say there are a number of builder assistance services. Given RVs popularity, many builds are actually from these 'assist' shops.
That's our world - we want instant gratification.

I don’t concur 100% with your assessment as you are painting the whole community with a very large brush. While the current kits are light years beyond the original 3/4/6 kits and many builders are just as you describe, there is a very large segment that definitely followed the more traditional route of completing as much as possible (to include avionics) on their own, myself included.

oh and BTW, paint jobs at one very well known shop are north of $20k and avg run of the mill shops are in the $12K-$15K. I feel lucky that my non-show quality paint job was $7500 back in 2017.

 

[painless]

I don’t concur with 100% your assessment as you are painting the whole community with a very large brush. While the current kits are light years beyond the original 3/4/6 kits and many builders are just as you describe, there is a very large segment that definitely followed the more traditional route of completing as much as possible (to include avionics) on their own, myself included.

oh and BTW, paint jobs at one very well know shop are north of $20k and avg run of the mill shops are in the $12K-$15K. I feel lucky that my non-show quality paint job was $7500 back in 2017.

Agree with you. I like to poke fun at the “kids” that are building the match drilled RV kits these days that all they need to do is toss a bunch of clecoes in the box the kit came in, shake it a bit, and the airframe will be all clecoed and set to rivet. I went to a forum at OSH last year put on by “the” paint shop to go to these days and thus scoop up a Lindy, and they stated that level of paint will run you more like $25-$35,000. I kid you not.

 

[jnmeade]

I believe it is cyclic fatigue driven by the elevator hinge moment. That moment is reacted across a relatively small distance, creating high cyclic loadings. Given the language in the service bulletins, I think this is more about insufficient fatigue margins than build quality issues.

Mr. Honey would say about 1440 hours.

 

[kyleb]

Agree with you. I like to poke fun at the “kids” that are building the match drilled RV kits these days that all they need to do is toss a bunch of clecoes in the box the kit came in, shake it a bit, and the airframe will be all clecoed and set to rivet. I went to a forum at OSH last year put on by “the” paint shop to go to these days and thus scoop up a Lindy, and they stated that level of paint will run you more like $25-$35,000. I kid you not.

Those guys (Evoke Aviation) do incredible work and are nice people too. They charge >$30K to paint an RV-10. They are located about 30 minutes of flight time from my home base, so I went over there on a Saturday a couple of years ago, walked the shop, and ate lunch with Jonathan the owner. I was just there for the show and tell, but a couple of guys in the group were considering them as a paint option. They will take a rough looking airplane and do a huge amount of fiberglass work and paint prep on it. They can turn a toad of an airplane into something very pretty. That said, it seems like an over-spend IMO, because if you actually use the airplane, that perfect paint job won't stay perfect for long. A great example was the nice couple at Oshkosh last year who had just gotten their -10 out of Evoke's shop. The windstorm on Saturday night slammed their rudder stop to stop (and beyond) and knocked holes in both sides of their rudder, plus knocked paint off of the elevators where the rudder hit 'em.

My airplane (never intended to be a Lindy winner) has a very nice 10' paint job. If you get closer than that, you begin to see minor flaws here and there. I paid less than Todd did for his paint, but I did all the prep work myself. And yes, in 9 months of flying, there are already nicks and bruises on my airplane.

But back to the bigger picture. I think 80% of RV builders put in the hard work themselves. Another 15% get some pro help, and the last 5% get a whole lotta pro help. Part of those 5% are paying for expert help in the quest for a show winning airplane and the other part would rather just pay for a spec built airplane than do the work themselves.

 

[CJones]

But back to the bigger picture. I think 80% of RV builders put in the hard work themselves. Another 15% get some pro help, and the last 5% get a whole lotta pro help. Part of those 5% are paying for expert help in the quest for a show winning airplane and the other part would rather just pay for a spec built airplane than do the work themselves.

At some point in every build, you will reach a point where you ask yourself "Do I want this to be picture perfect, or do I want to get to the point I can fly this thing?" How you answer that question will determine a lot of the appearance based build 'quality'. We got a a point with the fiberglass work where we said "Yeah.. We could sand this thing for another 2 weeks and it would be as smooth as silk and every single joint would be within a frog's eyelash of aligned... or we could go with what we got, which is already pretty darn good, and fly this thing two weeks sooner." We decided Fly > Shine. Not everyone answers the question the same, though.

 

[Notatestpilot]

At some point in every build, you will reach a point where you ask yourself "Do I want this to be picture perfect, or do I want to get to the point I can fly this thing?" How you answer that question will determine a lot of the appearance based build 'quality'. We got a a point with the fiberglass work where we said "Yeah.. We could sand this thing for another 2 weeks and it would be as smooth as silk and every single joint would be within a frog's eyelash of aligned... or we could go with what we got, which is already pretty darn good, and fly this thing two weeks sooner." We decided Fly > Shine. Not everyone answers the question the same, though.

In my day job as a liaison engineer - working at a 'large' airplane factory, we make that decision to get the production going and not be hindered by 'science experiments' and calculated theories.
I agree with you though, the over kill and dwelling on the wasteful tasks will keep a builder from becoming a flyer.

 

[Daleandee]

Perfect Is The Enemy Of Good Enough ...