What would you have done (and bonus if you're familiar with citabrias)

[Immelman]

Today I was flying the Citabria. After about 1.5 of sightseeing with my wife she taps my shoulder and points at the right strut assembly. The stabilizer that connects wing rib to rear strut had failed where it bolts to the rear strut... just sheared off. There one moment (yes, I pre-flighted it), gone the next. We spent the next 20something minutes going - nice and slow - to the nearest vfr airport.

Rental outfit's mechanic said not to worry about it; its purpose is to dampen vibration (well why the hell did the thing break from fatigue...). An A&P where I stopped was kind enough to fabricate a quick bracket to bolt it back together and I went home. I noticed that that strut, even when properly attached, has a noticable vibration in a certain airspeed range... resonant/harmonic type thing. Simple change of airspeed and it was gone. Trouble was that the "excited" airspeed range was, you guessed it, right in normal cruise IAS.... so this thing will shake most of the time. The left strut suffers no such predicament.

Back at home base I showed the rental outfit's A&P, explained that the braket was temporary, etc.. they liked the fact that I got it taken care of, but to my surprise, when I mentioned the vibration, he still wasn't worried about it. The vibration of that strut (probably what caused the stress fracture) was a known issue. I'd sum it up to wing rigging or strut tention, myself. No, I haven't built or rigged wings, but I do know a thing or two and can see how this would happen... but that is exactly what has me worried: I am thinking that the attitude of nonchalance may be my clue to take the business elsewhere. Unfortunately this isn't the first time I've caught that vibe from this particular person.

FWIW the A&P where I made the precautionary stop agreed with the assessment of the first; this was not a structural piece, but its job is to prevent an otherwise wimpy strut from vibrating, and later causing metal fatigue where it attaches to the fuselage.

Also just for my own information, if there are any citabria owners reading this I'm curious what your thoughts are; a quick google search didn't turn up much except for a reference to a citabria magazine article on the subject that I could not read online.

 

[avbug]

Congratulations on returning home alive. Apparently you believe in luck.

There is no such thing. Don't ever do that again.

Neither you, nor the mechanics involved are qualified to determine if the failed part is indeed necessary to the longevity or integrity of the structure. When parts of the airplane start breaking off in flight, you land. And you don't fly again in that aircraft until it's been properly repaired. A shadetree repair by someone telling you it's okay, doesn't count.

The mechanic who performed your repair could lose his certificate for doing so. Not a suspension, but a revocation. If caught, you're more likely to experience a suspension, but you placed yourself, and your wife, in jeopardy.

Repairs need to be done in accordance with approved data. Period. Without that, the aircraft is unairworthy, the airworthiness certificate is invalidated, and you are in danger. This isn't a time to be managing risk; it's a time to be eliminating it. Hard to create an inflight risk if you refuse to fly the airplane until it's not only properly repaired, but you have a clear explaination as to why the part failed in the first place.

Flutter is a very destructive force. Nothing trivial. Vibrations may appear to be affecting an unnecessary part...but what caused the part to vibrate in the first place, and what is that vibration doing? What's going on that you can't see? Important questions to ask before you bet your life on an illegal repair.

A rental car home is a whole lot cheaper than a casket.

 

[Rally]

I would have landed and made them get another strut. Structural things are not to mess around with, if your engine/radios/dg/fuel pump etc. You can still make a relatively controled landing. Not so with out a wing. I don't believe the A&P made a approved repair and he returned the aircraft back to service, as far as you knew it was airworthy. And for starters not that I am qualified but on many wooden spared/ribbed and even metal the dual struts are there to keep the back of the wing from twisting excessively from the front of the wing, that wing could be damaged now. Twisting of a wing is not something its designed for.

 

[MauleSkinner]

Having done an extended battle with rigging issues on my Maule that, at one point involved a vibrating rear strut, I would guess that the rear strut is in compression at your normal cruise IAS. Now, I'm not an engineer or anything, but my understanding is that lift struts are designed primarily for tension loads.

If you take something long and slender and pull on the ends, it will withstand a pretty good load. If, on the other hand, you push the ends together, it will bend fairly easily. Now, support it in the middle as you push the ends together, and it takes more compression force to bend it. This is probably what the broken strut is designed to do...it doesn't dampen vibration, it adds strength for increased compression loads. Unfortunately, it appears that the compression loads on the strut are more than the strut can deal with even with the help of the support strut.

If it were my airplane, I'd sit down with my mechanic and figure out how to get it fixed. After the tailwheel issue, he doesn't argue with me anymore when I tell him to spend my money

In your case, unfortunately, it appears that you don't have that kind of leverage due to the rental issue. If it were me, I'd find something else to fly. But then, that's one of the reasons I bought my Maule in the first place.

Fly safe!

David

 

[KeroseneSnorter]

ooohh, fully aerobatic airplane coming apart in level flight...and the FBO is not worried about the vibration....not too good there.

Find another place to rent from.

 

[Rally]

The reason I am so worried about structures is that alot of these airplanes are very old. Very old aircraft can be very safe as safe as a 172 SP out of the factory. The problem is that owners/operators are'nt taking the fact that when the aircraft were built they were 5 years old, and that the aircraft has been exposed to every type of flight condition weather salt, sand etc imaginable in the last 10-60 years. I flew a aircraft one time that had a stabilator repainted and deice boot removed. Problem was that even though it was signed off (and the mechanic that signed it off admited that he assumed the mechanics would do the balance) the balance was never done. Furthermore, the drain holes for the stabilator were covered by paint 6 hours of rain inflight and a CG change was all it took for that stabilizer to become unbalanced. Scared the *hit out of me. Not a joke. I'll fly any airplane to the ground and make sure I stand a good chance of the crash as long as I have control. Loss of tail control or wings is for the most part unrecoverable. Really FAA requirements are'nt that stringent. Consider the fact that a 100 hr pilot can go 2 years without flying do a 3 takeoffs and landings and still be legal same thing with repairs but it has to be according to resonable and normal practices outlined in the maintenace advisory circulars.

 

[Amish RakeFight]

A rental car home is a whole lot cheaper than a casket.

Good quote.

You took a chance and got lucky when you should have had one of thier own pilots or A&P fly that thing back to base.

 

[avbug]

The problem is that owners/operators are'nt taking the fact that when the aircraft were built they were 5 years old, and that the aircraft has been exposed to every type of flight condition weather salt, sand etc imaginable in the last 10-60 years.

You mean the aircraft were on the assembly line five years and were five years old once they were officially built? Or perchance did you mean to say that owner/operators were five years old when the aircraft that they own or operate were built? If you meant the latter, what on earth has that to do with the price of tea in China? Would an operator who was ten years old when his aircraft was built be a better owner, or one who was 25 years old when his aircraft was built be even better? Not seeing the correlation, there.

Consider the fact that a 100 hr pilot can go 2 years without flying do a 3 takeoffs and landings and still be legal...

And a flight review by an authorized instructor too, of course...

same thing with repairs but it has to be according to resonable and normal practices outlined in the maintenace advisory circulars.

Of course repairs must be done in accordance with approved data (not necessarily advisory circulars, however), but what has that to do with a pilot flying two years with only three takeoffs and landings?

 

[Rally]

You crack me up Avbug. The point was some of these aircraft are'nt getting any younger. My dad was 5 years old when our C-170 came rolling out of the factory. The C170 outlived him. 50+ years is a long time and alot of people are'nt taking maintenance serious. And you could go exactly 2 years with just 3 takeoffs and landings and the next day need a flight review.
The coorelation to that was the FAA outlines minimum standards and like the above rule are'nt that stringent same thing with maitenance.

 

[avbug]

The coorelation to that was the FAA outlines minimum standards and like the above rule are'nt that stringent same thing with maitenance.

I couldn't follow your sentence structure, but you appear to be suggesting that maintenance regulation isn't stringent or exacting. I don't know where you got that impression, how much you know about maintenance, or your familiarity with maintenance and performance regulations, but you're quite wrong.

I've spent a number of years making my living as an aircraft mechanic, inspector, and Director of Maintenance. Personally, I don't know many mechanics in this business who take their work lightly, or who don't feel the weight of oversight. The knowledge base and scope of what an aircraft mechanic must know and do, and the detail to which he or she must do it, is far more extensive and exacting than that required to fly. I know, I do both.

Some private owners may not take maintenance very seriously, any more than some gun owners properly clean, care for, and secure their weapons, or those entrusted with the lives of pets properly provide for them. However, from the perspective of the FAA, there isn't leeway or wriggle room with maintenance proceedures, tolerances, and practices.

Age of the airplane is irrelevant. How does a pilot or owner of an aircraft being younger than the aircraft have any bearing on how it's maintained? Do you seriously suggest that an owner or operator, or mechanic might provide a lesser degree of maintence for an aircraft that's five years older than himself, than he might for one that's younger than himself? This is a ridiculous concept.

I learned to fly in a 1947 J-3 cub. I am not that old. The cub was impeccably maintained...it might easily have passed for one fresh from the factory on the day it rolled out, except perhaps that it may have been in even better shape, with better fabric, etc. I've flown and am typed in WWII bombers, though I didn't fly in WWII. I wasn't born then. When I flew the airplanes, they were better maintained and saw more maintenance more frequently, and were taken care of by people with far more experience and training than their original owners. Never the less, we saw them break up recently, and mechanical things do fail. Age wasn't a factor, though fatigue was.

In this case, we have an example of an aircraft suffering a failure of it's structure. The persons who elected to jerry rig it and who dismissed the seriousness of the failure had no place doing so. The aircraft should have been immediately landed and not flown again, following the failure.

I think that to suggest maintenance regulation is lax, that maintenance is viewed with no level of seriousness, or that owners and operators tend to dismiss maitnenance on aircraft older than themselves, are unfounded concepts.

The point was some of these aircraft are'nt getting any younger.

Neither are any of us who fly them. Again, your point is?

 

[MauleSkinner]

I've noticed over the years that a lack of clear communication between the pilot and mechanic is far more common than we would prefer to believe. According to the mechanics I've worked with, "inop", "broke", and similar words do not exist except in a structural sense (the wing broke in half). If you are referring to the operation of a system, it's not "inop". It's either doing things that it's not supposed to or not doing something that it is supposed to. Either way, there are specific indications of such that need to be conveyed.

In the specific case of this Citabria, the original squawk, way back when, was probably just a mention to the mechanic on the way out the door that the struts seems to be vibrating once in a while. Nothing specific, nothing urgent, just a passing mention. It then becomes a non-urgent condition in the mind of the mechanic.

A more appropriate method would probably be a written squawk, outlining specifically the speeds and/or conditions under which the right rear strut vibrates (and that none of the others do), and whether or not you can hear it or feel it in the cockpit when it happens. Follow-up with the mechanic to ensure he got all the information he needed and/or how it was handled is usually a good idea.

If the mechanic doesn't see the need to deal with it, then other avenues need to be pursued. As I indicated in an earlier post, it's easier to apply the pressure to get something done if you're the one directly paying the bills. Rental airplanes need to be handled differently, and other than simply going elsewhere, I haven't found a technique that works consistently.

Note that this is all from the perspective of a pilot, not a mechanic. Commentary from the mechanics' side is welcome.

Fly safe!

David

 

[Rally]

Point taken Avbug you know your stuff. My communication might not have been the best. What I was suggesting is that alot of these aircraft are older, alot of annuals a minimal at best. I have seen it first hand, and refused to fly many aircraft. I once worked for a banner tow out fit that had significant play on the strut to wing attachment in otherwords you could see it move. I said thanks but no thanks. Fix it and call me when you want me to fly. The particular aircraft was a '43. Not to say that this could'nt happen on a 5 year old aircraft but if maintenance is not kept up over the years its all the more likely.

Has nothing to do with the age of the owner, pilot etc. There is quite a curve on age so to speak. When my father was a pilot at 30 a cub may have only been say 30 years old. Now its more than twice that, and you can have a perfect aircraft if maintained properly. But age, use, maintenance have to to be resonable to each other or crap breaks. Sorry for the miscommunication but I was mostly agreeing with your original statement in a not so smooth relavant way.

 

[Rally]

Was this a strut brace or the complete rear strut. For instance on a but there is actually 4 places where something attaches to the wing. Forward strut, rear strut and the two strut braces in between. Which was it?

 

[Immelman]

Thanks for the replies. Would have written back sooner but was away from the computer for several days.

First, thanks to all for the thoughts. Avbug, I appreciate the seriousness you gave to the issue. You had better believe that the first thing we did was to slow the airplane down in case of any bumps to reduce loading, and babied the airplane to the nearest field. The field repair was, in my opinion, **at the time** just fine, but I understand where you're coming from and recognize why we use 'AN' bolts, etc., to begin with. I'm still going over this in my head and recognize that, given all that is on the line, deciding to go home was probably a judgement error.

This particular airplane is only a few years old and has just a few hundred hours on it. Of course it is a metal wing spar being newer, not that that has anything to do with the rigging issue that might have caused that. Along those lines, I've learned that this airplane was ground looped with moderate damage and repaired by what is supposedly a reputable shop very experienced with citabria restoration (this was prior to the FBO purchasing it for rental use); from what I've gathered at least some rigging had to be done given the nature of the repairs. This may have been where the sort of vibration issue came from, unless Champion is producing aircraft this way (which I kind of doubt).

About that last question: No, the rear strut did not detach at any point. On citabrias there is a 4-pt brace made of three rods; two vertical that go from different points along the chord line of a single wing rib vertically down; they each attach to one strut (front and rear). There is a third rod, horizontal, that ties both vertical rods and both struts together. The connection points involve a vertical bolt that goes through each strut with a small, what I'd call as a layman "tack weld" to a horizontal (perpendicular) threaded piece above it; a conventional bolt screws into this horizonatally, and passes through each of the two rods that connect to an individual strut. The tack weld is what broke. This photo I found illustrates the structure I'm referring to:
http://www.planecover.com/Citabria/Citabria3.jpg

Notice the trapezoidal shape formed by the bracing I'm describing. Where that meets the rear strut was the point of failure. With the pressure relieved the bracing assembly separated from the strut by approx 1/2" in flight, and the distance was the same on the ground. They could be easily pushed back into the correct position (as was done to affix the temporary bracket).

Finally, I did write up a squawk describing the vibration including the speeds that excited it.

 

[Rally]

A worry but hardly as much as we made out of it in this conversation. I thought ther rear spar attachment strut is what had failed. Sorry. However it probably was not a approved repair and probably should have been on a ferry permit at least with a ferriable repair.

Thanks

 

[avbug]

I knew what you were talking about from your prior description, and I stand by my previous comments. Bottom line; if the repair isn't an authorized and approved repair, it makes the aircraft unairworthy. Without the repair, the aircraft is unairworthy. Taking guesses as to w(h)eather it's safe or not is irrelevant. Once the aircraft has been made unairworthy, all other discussions are meaningless, because that's as far as you need to go. Or should go.

The unairworthy condition is exactly worthy of the discussion in this thread; no one has made much ado about nothing.