What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

SB 14-01-31; RV-6, 7, 8

No Cracks

11 yr old RV 6A
520 hrs TT
180 HP IO-360
Hartzell C/S prop (not BA)
Not much grass or acro
Fairly sharp corners, no notches
Used lots of light and magnification

No Cracks

Don B
RV 9 Rebuild in Progress
 
RV4??

Sorry if this was answered already, I probably missed it going through over 300 posts. Any thoughts on why the RV4 was not included? It has the same HS as the RV6. Wondering if it is simply because no cracks have been found on a -4 to date or another reason. I plan on inspecting mine regardless, it certainly can't hurt to look and only takes a few minutes. Besides I need to do the other SB anyway.
 
No cracks?

2009 RV-7
380 Hours TT
360 hours with a H-6 Subaru and Sensenich 3 blade carbon
20 hours with IO-370 and aluminum Hartzell BA
Always operated on pavement
light acro
50/50 towbar / no towbar
Notches

I'm going with no cracks, but saw a line in the primer that made me nervous. Cleaned it up and I can't see anything, but I'm planning to use some dye penetrant to verify.
 
Neal@F14 said:
Has anyone found cracks on any RVs equipped with wood or composite fixed pitch props... or composite bladed CS props?

Going thru the reports posted thus far, unless I've missed something, it seems like only those with metal props (both FP and CS) are finding cracks.
Click to expand...

My 8 has never had a metal prop. Wood the first 600 hours and composite the next 1300. Only a small crack on the top right side, but a crack is a crack.
 
tracy said:
I can't figure out why they want the flanges trimmed in step 10. Any thoughts?
Click to expand...

I'd say it's to avoid the sudden transition in section stiffness that occurs when the ends of the channel flanges are squared off. Trimming the flanges will provide a more gradual change in the stiffness of the channel over the length of the taper.
 
A few statistics

It is difficult to capture in a post that will be read, but still say something useful, but here goes.

Of the 14 (yes there are more) cracks reported here with hours, they plot in a nice straight line on a Weibull plot, a statistical probability of failure plot.

Comparing each report hours to that expected for the fleet, this is about 1% of each years first flights beginning at 560 hours. There are some gaps, but that is pretty close. The only TT group that is odd is around 13-1400 hrs for the RV8, there seem to be 3 cracks reported in that hour group.

If half of all cracks have been reported here, then the crack occurrence rate is 2% of an hours group. Each hour group is 100-120 hrs. There are no failure reports above 2000hrs and no failures under 530 hrs. (update :340 hrs )The crack generation statistics may have as much to do with gust occurrence as prop or other hardware combination. If there were some strong influence of prop etc then the plotted data would not be a straight line. It was. The slope was 2.8 which is typical of a fatigue failure.

So, overall, if you have more than 560 hours you have a 2% (roughly) chance of finding a crack today. That is the same next year too, and the year after that. But the probability that you will find a crack eventually (3000hrs) is higher. This certainly supports the yearly inspection.

All in all my opinion is that this is, as Paul so clearly put it, not an emergency, and there should be no frustration or anxiety over this issue. Anyone who has built a plane has gone through much more in the process.

Hopefully this was helpful.

PS with the addition of the 340 hr report, there is a barely perceptible shift in the curve, along the thickness of the pencil line. Not enough to rep lot of change conclusions.
 
Last edited:
No crack

No cracks.
RV-6
400 hours
50% grass
0-360
Metal Prop
Light acro
Finished in 2000
Relief notches and smoothed very well. I did not build the plane. Planning on routine inspection and leaving as is for now.
 
Hi Bill,
Thanks for tracking these occurrences. There is one person with 3900 hrs on his 6A with no cracks. Member's name is Rosie. Not sure how this affects your outcomes.

John
 
Last edited by a moderator:
jroser said:
Hi Bill,
Thanks for tracking these occurrences. There is one person with 3900 hrs on his 6 with no cracks. Member's name is Rosie. Not sure how this affects your outcomes.

John
Click to expand...

Chuckle...


Other words here
 
Last edited by a moderator:
No Cracks

RV6A VH-YOY
O-360 A1A
Hartzell C/S (Metal)
320 Hrs
Purchased last November
Mainly pavement, Very little acro
No cracks, with relief notches
 
Hello from South Africa RVAitors,

Checked my 7A yesterday and I have to say - really not a difficult exercise (on both SBs) Took about an hour all together.


No cracks.
RV-7A Reg ZU-ORV
499 hours
5% grass and gravel
Mattituck I0-360
MT 3 Blade Prop
Light acro, lot's of air-racing and formation.
Finished in 2008
Relief notches and smoothed very well. I did not build the plane. Planning on routine inspection and leaving as is for now.
__________________
 
19 yr old RV-6

RV-6
Built before pre-punched kits were available
Approx 1600 hrs TT
Hvy to Modest Acro for 19 yrs
50% Pavement 50% Grass
Wood Warkne Prop
No Notches
No Cracks
 
jroser said:
Hi Bill,
Thanks for tracking these occurrences. There is one person with 3900 hrs on his 6 with no cracks. Member's name is Rosie. Not sure how this affects your outcomes.

John
Click to expand...

All non failures had no bearing on the plot. We know what Mike Seager has over 4000 hrs on his 7 and we don't have data on the cracks found by Vans on the original articles either. Those were considered, but none of these single events will move the curve much and absolutely would not change the slope. With a little variance due to confidence band (75% probability that the plot is correct), we could easily have planes out to even 9000 hours without a failure. They, according to this plot, would be entirely possible, but obviously, rare.

Due to unknowns, only the slope and shape of the curve is close to firm.

As a practical point, none of this really means anything for decision making as an owner/builder, it is just a perspective that supports the SB. The SB addresses actions based on the hard known facts and is the only document that counts.
 
Last edited by a moderator:
Inspection party....

RV7 2010 somewhere around 300hrs
~1st 250hrs with a Metal FP Sensenich, ~50 or so with a Metal BAF Hartzell
O-360 Carbed
Very light acro
HS started life as a RV6 and has no notches
No grass time
No cracks


RV7 2007 630hrs
Metal BAF Hartzell
O-360 Carbed
Very light acro
Based on grass
Has notches
Cracks


RV6A 2008 700hrs
Metal FP Sensenich
O-360 FI
Very light acro
Little to no grass time
No notches
No cracks
 
Last edited:
According to Ken Scott the repair is no big deal (at least he didn't say "10 minutes")

Quote: Ken Scott of Van's told AVweb on Wednesday that repairs, if needed, should take a few hours at most.

Sorry but being in the repair business statements like this really aggravate the **** out of me.

I'd be more than willing to fly my airplane to the Van's factory if they will do the repair for "a few" hours labor!
 
Last edited:
rgmwa said:
I'd say it's to avoid the sudden transition in section stiffness that occurs when the ends of the channel flanges are squared off. Trimming the flanges will provide a more gradual change in the stiffness of the channel over the length of the taper.
Click to expand...
Hmmm... But then you add a deep notch right where it ends? That alone is a stress concentration. I still don't understand why you would want the deep notches when you could just round the corner instead...
 
2002 RV-7 QB
First Flight JAN 2005
Aerosport I0360M1B
Hartzell C/S blended airfoil
716 hours
first 3 years on hard surface, last 5 years living on grass
mild aerobatics
Notches
No Cracks
 
BillL said:
It is difficult to capture in a post that will be read, but still say something useful, but here goes.

Of the 14 (yes there are more) cracks reported here with hours, they plot in a nice straight line on a Weibull plot, a statistical probability of failure plot.

Comparing each report hours to that expected for the fleet, this is about 1% of each years first flights beginning at 560 hours. There are some gaps, but that is pretty close. The only TT group that is odd is around 13-1400 hrs for the RV8, there seem to be 3 cracks reported in that hour group.

If half of all cracks have been reported here, then the crack occurrence rate is 2% of an hours group. Each hour group is 100-120 hrs. There are no failure reports above 2000hrs and no failures under 530 hrs. (update :340 hrs )The crack generation statistics may have as much to do with gust occurrence as prop or other hardware combination. If there were some strong influence of prop etc then the plotted data would not be a straight line. It was. The slope was 2.8 which is typical of a fatigue failure.

So, overall, if you have more than 560 hours you have a 2% (roughly) chance of finding a crack today. That is the same next year too, and the year after that. But the probability that you will find a crack eventually (3000hrs) is higher. This certainly supports the yearly inspection.

All in all my opinion is that this is, as Paul so clearly put it, not an emergency, and there should be no frustration or anxiety over this issue. Anyone who has built a plane has gone through much more in the process.

Hopefully this was helpful.

PS with the addition of the 340 hr report, there is a barely perceptible shift in the curve, along the thickness of the pencil line. Not enough to rep lot of change conclusions.
Click to expand...

Thanks for statistical analysis Bill. It helps keep things in perspective.

While the SB is long and at first frightening, it is easy to live with. Inspect for cracks (which should be done in accordance with condition inspection anyhow) if all is ok, go fly for another year. The entire aircraft inspection process is no different. If something is in need of repair, fix it.

There is nothing new here - the SB is getting everyone focused on a potential problem and telling us how to deal with. That's good! That's how things should be in the aviation world.
 
I think it is important to remember that a sample size of 14 (or 140) is very small and any statistical data derived has a very low level of confidence. That's why telephone polls almost always have over 1000 respondents.

-John

BillL said:
It is difficult to capture in a post that will be read, but still say something useful, but here goes.

Of the 14 (yes there are more) cracks reported here with hours, they plot in a nice straight line on a Weibull plot, a statistical probability of failure plot.
Click to expand...
 
Used dental camera

RV-7A
100h
O-360 FI
Metal FP Sensenich
99% paved runways
No acro
Notches
No cracks

I used a dental camera to get good light and good pictures.
(Search "Dental Camera on VAF and E-bay to get some info)
 
RV6
GDFUN
No Cracks found
Tailplane built around 1996. No Notches
O-320 (160 Hp)
Wooden Prop
All Operations of Grass
No Aeros
Total Hrs 110
Will continue to do annual inspections
Elevator also checked No problem
 
David-aviator said:
Thanks for statistical analysis Bill. It helps keep things in perspective.

While the SB is long and at first frightening, it is easy to live with. Inspect for cracks (which should be done in accordance with condition inspection anyhow) if all is ok, go fly for another year. The entire aircraft inspection process is no different. If something is in need of repair, fix it.
Click to expand...

Considering the inspection takes only about 10-15 min, an annual inspection or every oil change should not be all that hard.
 
Adding notches?

Are folks without cracks and without notches adding the notches?

It seems to me that, especially some of the higher time airframes, that it would be better to leave well enough alone and just inspect regularly.

Perhaps I'm falling victim to the Texas Sharpshooter fallacy, but it seems to me there is a strong correlation between the existence of notches and the incidence of cracks. By that I mean, the incidence of reported cracks appears to be lower on unnotched aircraft.
 
SB 14-01-31

Check my 8 this morning, very closely, as I have almost 1900 hrs on the old bird, and she has had a good work out now and then.

All is well. Would be interested in finding out some information on those that have found a crack, TT, aerobatics, bush flying, or different circumstances that they think may have influenced the "crack".

Baby Bear
 
It's all in the context, Walt

Walt said:
Quote: Ken Scott of Van's told AVweb on Wednesday that repairs, if needed, should take a few hours at most.

Sorry but being in the repair business statements like this really aggravate the **** out of me.
Click to expand...

I understand your point but the word "few" really only means more than two, and I hope pilots are smart enough to realize such is the case. What Ken was really saying is that it will take more than "a couple" (two) hours to perform the fix. There is an implication that it will take significantly less time than building an entire RV. Nothing more.

100 hours is a "few" if your reference point is building the entire airplane (including smelting the ore, manufacturing the parts, transportation, etc.). 1000 might be considered a "few" in the context of building the entire International Space Station. ;)
 
No Cracks for me.

I inspected mine today and was pleasantly surprised that I have no evidence of cracks. I would have thought that I was a prime candidate based on others who have cracks. I have:

RV-6 kit from 1996
No stress relief cutouts
800 hrs including frequent loops, one or two 5g sustained turns, rare snap rolls and spins, and racing at Reno in excess of Vne.

So why don't I have cracks? I have 2 thoughts on that matter.

As I took the fairing off today I noticed all my unused nutplate holes in the skin edge. My fairing fit so poorly that I made my own (partly because my prop spins opposite direction any my rudder incidence is in the opposite direction). anyway, the home make one fits well enough to be held on with only a few screws. There are no attachments in the skin of the h-stab. I wonder if the forces on the fairing could be playing a role in these cracks.

The other main difference for me is my engine and the more frequent but weaker pulses from the engine and prop. Someone already mentioned that this may be a factor.
 
Inspected for both SBs today -- AOK

RV-6A, 1993 vintage, 900hrs TT, IO360 CS ---- notched, no cracks
 
Snowflake said:
Hmmm... But then you add a deep notch right where it ends? That alone is a stress concentration. I still don't understand why you would want the deep notches when you could just round the corner instead...
Click to expand...

There are notches and there are notches. A sharp notch can act as a localised stress riser, and a well formed notch will tend to reduce stress concentration. But as has been pointed out in another post, the top and bottom notches in this particular case also reduce the overall depth of the plate, resulting in higher stresses simply due to the smaller cross section (as opposed to a localised stress concentration).

Perhaps the notches in this particular case are something of a double-edged sword - reducing stress concentration, but at the cost of raising the overall stress levels in the plate. Maybe that's why there appears to be no strong correlation between the presence of notches and the presence or absence of cracks. In any case, as was alluded to in post 277, it's good practice to avoid sudden changes in stiffness, which may be the reason that Vans have asked for the flanges to be tapered.
 
Last edited:
RV6A
1997 vintage empenage kit
flying since 2006
194.5 hrs
O320 E2D 150hp
Catto three blade
rolls only, not very frequently
no grass
no notches
no cracks in HS spar web or elevator rod end platenuts


Examined with dental loupes and LED illumination
 
SB 14-01-31

I went out to inspect "Redhawk" RV 7A (Serial 73077) today. The plane has 340 hours, light acro, mostly paved strips. IO 360 M1B, fixed metal Sensenich prop. Bounced in really hard trying to jump over debris on the runway at KIGX and bounced to 4-6 G in turbulence going over the mountains. It is a quick build, but I built the tail from Vans match hole tail kit in the summer of 2007. My plans required the relief notch 5/16" over from the where the spar web flanges are bent. We looked very carefully and found no indications of cracks at this point. The notch was very smooth, I like to buff the edges in places like this, not saying one won't develop. Lastly, I don't know if it make any difference, but my tail fairing is very modified, wraps around the stab leading edge and attaches in the rear, so I don't have the nut plates at that intersection, but a rivet instead. My flanges seem to lay very flat in that area vs some of the pictures that I have seen, not sure what the difference may be. I hope the helps the data keeper.

I'm building an RV 14 now, and the double spars is really stout on this ship. We plan to watch the stab frequently since it is only a few screws to remove the fairing on the 7 and use dye penetrant each annual.

I think my would preference would be to build a new stabilizer for the RV 7 if Vans were to offer an enhanced or improved version at a reasonable price vs the retrofit. I've been told my building skills are pretty good and I think I could do a good job on SB 14-01-31, but my gut would feel better with a new stab. CJ
 
Both Service Bulletins complied with

RV-8 (no notches....no cracks)
0-360, CS Prop, 582 hrs., Paved runways, Lots of acro.
 
rgmwa said:
.........Maybe that's why there appears to be no strong correlation between the presence of notches and the presence or absence of cracks.
Click to expand...

Been following this thread and I would say there is a statistically significant correlation between the presence of notches and the presence of cracks - over 80% of the cracked spars reported here have notches - only a couple without notches have reported cracks. While I have not tabulated it, the distribution of notched spars vs non-notched appears relatively even.
 
SMO said:
Been following this thread and I would say there is a statistically significant correlation between the presence of notches and the presence of cracks - over 80% of the cracked spars reported here have notches - only a couple without notches have reported cracks. While I have not tabulated it, the distribution of notched spars vs non-notched appears relatively even.
Click to expand...

You may be right. I guess time will tell.
 
2011 RV7 N797RB
210 hours TT
AeroSport IO-375
WW 200RV
Light Acro
Some grass, mainly pavement
Tow bar, tow strap
Notched
No cracks

VAF 2014 Dues Paid
 
My buddy and I inspected today:

7A with O360 180hp, Hartzell metal prop.
410 hrs
Lots of acro
No notches
No cracks!

7 with IO360 180 hp, WW200RV composite prop.
125 hrs
Some light acro
Notched
No cracks!
 
The thread of wishful thinking.

On a lighter note, I'm noting an amusing trend to this thread.

Those with composite props are tipping that the cracks are caused by metal props.

Those with nose wheels are suggesting that the problem may be more widespread among tail draggers.

Those with no notches are predicting that notches are the problem.

Those with notches are tipping that notches will be superior as long as they're meticulously deburred (I happen to fall into this camp).

I'm therefore coming to the suspicion that many of the suggestions on this thread are less science and more wishful thinking. :D
 
Captain Avgas said:
On a lighter note, I'm noting an amusing trend to this thread.

Those with composite props are tipping that the cracks are caused by metal props.

Those with nose wheels are suggesting that the problem may be more widespread among tail draggers.

Those with no notches are predicting that notches are the problem.

Those with notches are tipping that notches will be superior as long as they're meticulously deburred (I happen to fall into this camp).

I'm therefore coming to the suspicion that many of the suggestions on this thread are less science and more wishful thinking. :D
Click to expand...

I did not find any cracks in my HS and believe my brand of EIFS has much to do with that.
 
Captain Avgas said:
On a lighter note, I'm noting an amusing trend to this thread.

Those with composite props are tipping that the cracks are caused by metal props.

Those with nose wheels are suggesting that the problem may be more widespread among tail draggers.

Those with no notches are predicting that notches are the problem.

Those with notches are tipping that notches will be superior as long as they're meticulously deburred (I happen to fall into this camp).

I'm therefore coming to the suspicion that many of the suggestions on this thread are less science and more wishful thinking. :D
Click to expand...
But notches really are the problem! (Deburred or not.) ;)
 
1999 rv-6
830 ttaf
O360 counterwghted crank
Hartzell c/s prop
Regular mild Afro
Occasional grass
Notches
GRT efis
No cracks either sb

Whew
 
I have a tip-up. I have no cracks. Therefore, sliders = cracks. Whew!

Ps: I also have 0 hours on the airframe, with another 500+ hours of build ahead of me. But it's a good thing I have a tipper!
 
Crucial feedback for Vans

On a more serious note.

This thread will be providing enormously important feedback for Vans. I'm absolutely sure they will be religiously monitoring it on a daily basis for information resulting from the individual aircraft inspections for cracks. People are reporting back to this thread on VansAirforce....they're not reporting back to Vans.

In other words, up until now, Vans has probably had very little hard information on the actual extent or nature of the cracking. They knew it was a problem with serious implications but they just didn't know how widespread the cracking was. Their sample would have been too small. Now they're finding out (and so are we).

We can be of major assistance here to Vans. And the more we assist them, the more knowledge they will have, and thus the better their solution to the problem (the more they can assist us).

How can we assist them.

Firstly, keep reporting results of inspections....everyone should report here. Even if you don't normally post on VansAirforce, make the effort. You're an important part of this important survey.

Secondly, be careful with your inspection. As reported these cracks can be very difficult to detect with the naked eye. A false report is worse than no report.

Thirdly, report both good and bad results. My guess is that those with cracks may be more reluctant to report for one reason or another than those with no cracks. That may skew the data and hide the extent of the problem.

Fourthly (and this may be the most important), if you have a crack then send photos of the cracked area. This will be most important to Vans. As they say a picture is worth a thousand words.

Fifthly, provide maximum aircraft data as previously requested (model, year, hours, notched or not, aeros, runway, prop type, etc)
 
You so funny!!

scard said:
I'm happy to have a little skin in this game. Just inspected mine. No cracks. 0hrs. Lots of aerobatics being moved from one space to another in the shop! I'm looking forward to getting the parts so I can utilize my expertly honed rivet removal skills :). This is going to be an easy couple hour project for those of us that have yet to install the HS. I do feel a bit sorry for those that didn't build their airplanes or otherwise have acquired the skills.
Click to expand...

On a normal day I would say "you crack me up!", but it just doesn't seem appropriate right now. But you did bring a smile to my face. :D
 
No mention of small vert stab & rudder

Haven't heard anything mentioned about small vert stab & rudder for the six's that kept originals as does the rv4 having small vs & rudder. Any of those showing cracks? Just checked mine today-short original vs & rudder--no cracks in HS . Don't know if that is even a factor?

Dave Ford
2004 RV6 FADEC
 
Possible new info:

I initially thought I was crack free, having pored over the photos I took of the four corners in great detail. However, I happened to open them up again and noticed something I had missed on first review... The photo below is taken with the camera in the space behind the front spar, and the lens oriented roughly towards the passenger wingtip. So you're looking at the top right stress point in the SB.

Look at the rib at the right of the photo though, specifically the bend in the flange that joins it to the back of the front spar. Right beside that top rivet, is a crack that extends down at least the width of the rivet head. It's very faint to see, but the rivet head is just above the center of the photo, the crack just to the right of it.

I wonder if this is related to the failure in the SB, and if people should check for this as well... Maybe my shear web didn't crack because this part did?

IMG_20140202_160352.jpg


In any case, as the crack in question would be fixed if I did the SB, I'll be ordering the kit.

If the photo doesn't embed properly for some reason, here's the album with all four corner photos (yes, I know it's dirty... the annual is coming and it's bl**dy cold in the hangar right now).
https://picasaweb.google.com/111320...&authkey=Gv1sRgCIuN5Ofwz8yrUQ&feat=directlink
 
You must log in or register to reply here.
Back
Top