Hangar Flying

Hi David,

Long time no talkee.

Yes, Burt put out the word on the g limit reduction after Andreas Christou's finding.  In the forensics of that airplane, the sparcaps were layed up rich (you can see the swelled composite structure immediately inboard of the inboard edge of the wing fitting), and when the outer fitting plate was pressed in place, it "hydraulicked" out the excess epoxy inboard, swelling and distorting the sparcap layup.  I believe the problem with Mike's VariEze was that the sparcaps were also layed up with excess epoxy, but the outer fitting plates were not squeezed into place.  This resulted in at least a .030 inch or more extra gap.  Not very good structurally, based on the design requirements of the wing fittings. 

Burt put out this limitation and was being rightfully conservative.  Andreas's airplane, and (in multiple qualified people's judgement) Mike's airplane, are both examples of why Burt did this.  Unless you build the airplane yourself, you really have no way of ascertaining the quality of some of the most critical structure and structural interfaces in the airframe.  As a buyer, you rely on the skill (or ham-fistedness...) of the builder in ensuring your structures are safe.  In one of the last Canard Pushers, Burt explicitly gives his opinion that these airplanes should not be sold.  Again, rightfully conservative, having evaluated numerous accidents (and at least 3 in-flight structural failures of VariEzes) over the past several decades.

I have placarded my own Eze at 1200 pounds, and +5 -2 gs (at 1110 pounds), and +3.8 and - 1.5 at the 1200.  I know exactly how all my primary structure was built, and know that it is of the best quality I could have made it.  In Andreas's airplane, one would have never known about the poor workmanship in the spars.  On Mike's airplane, the discrepancy was readily apparent.  Burt states at least once in the CPs:  "Your best workmanship is barely adequate", or words to that effect.  Yup.  The VariEze is pretty tolerant of less-than-good workmanship, with overdesign, but everything has its limits.

No.  Mike's airplane (fortunately) did not suffer wing failure, but as I have exasperatingly stated, had very high potential for one, and it would very likely be one that "snuck up" on the pilot.  The failure mode would have most-likely been cumulative material distortion in the outer upper wing fitting plates at the taper pin bore edges.  Eventually, the inner plate would take on more of the flight loads than the outer plate would.  Such unbalanced load distribution would impart a bending moment in the upper spar caps (centersection).  Over time, such actions had very high potential to end up causing the inner plate to take the vast majority of the flight loads.  There is a point where the resultant bending moment in the sparcap would cause the allowable stress level in the sparcap section to be exceeded.  The sparcap was already compromised, structurally, by being epoxy-rich.  Excess epoxy in a glass structure that reacts compressive loading is uglier than in structure that is in tension.

If Andreas had flown his airplane without finding the structural degradation it had, with only a single inner upper plate reacting flight loads, it would have been ugly-bad evetually  I believe Andreas did frequent acro in his airplane.  Lucky man.  Such a structural configuration is exactly the concern I had for Mike's airplane, over the long-term.

As for the recent VariEze crash up this way, no.  Not me.  I got that out of my system 10 years ago (knock on wood - I have firsthand knowledge of how a hidden, latent failure mode in a system can ruin your day, which is why I can be pretty damn adamant about squwaking about failure modes I can recognize given my canard and "day job" experience).  I helped recover the airplane from the field late in the afternoon with several other good souls, on the day of the crash.  Pilot OK (cuts, bruises, etc.) after an overnight stay in the hospital.  Airframe was totaled.  Airplane was on its second test flight.  Suffice to say, I'll let the NTSB report speak to this one. 

One thing I hope all buyers of these airplanes do is at least go read ALL of the Canard Pusher Newsletters.  Become familiar with the evolution of the VariEze and the Long-EZ (Ditto for Nat's Cozy newsletters for the Cozys), and study up on the accidents and the failure modes that caused them.  Going back to 1982 with my beginning in the Rutan canard world, I still pull the CPs once in a while and refresh.

Best regards,

Nevil Shute wrote a great novel about this kind of scenario, called, “No Highway” (1948).  If you are not interested in reading the book, a reasonable movie was made a few years later (“No Highway in the Sky”).  Gives a good perspective about seemingly trivial little things that aircraft engineers fret about, as written by an aeronautical engineer turned novelist.

I stand by my conclusion regarding the wing fittings on this late VariEze.  Moreso, I’m glad you got out alive, Mike, and that it was not a failure of the wing attach structure that caused the accident.

For what it is worth, my “opinion” about the wing fitting configuration on this airplane was, in detail:

1.   My initial engineering assessment, back in 2005, for this airplane, based on direct airframe repair/modification engineering design experience (big aluminum beasties, and yes, believe it or not, the same engineering principles, analysis, material characteristics, etc., that apply to the big ones also apply to the little ones…)
2.   On-site detailed examination & measurement of the wing fittings by one of the most-respected VariEze builder/drivers in the Realm (also happens to be an exceptional engineer). 
3.   Actual, formal (not just thumbnail) engineering analyses (has to be done under the requirements of evaluating what is referred to as Statically Indeterminate structure), evaluating to the absolute worst-case scenario (worst-case, based on epoxy-rich sparcaps, aft cg loading at 1200 pound weight because I know that’s where most VariEzes end up, when loaded full…), etc.
4.   Peer review/independent analysis of the above by two veteran airframe structures/stress analysts.  I always seek qualified Second Opinions when dealing with such issues, as this is the way we solve such problems in my profession.
5.   Assessment of this condition by the designer’s Right Hand Man, when presented with the configuration and dimensions of the wing fittings (direct quotes copied and pasted out of the email I received back on this issue):

      "Ooohh, that's not good".

   and:

      "I wouldn't fly it like that - would you?".


I also considered having this looked at by a DAR (Designated Airworthiness Representative) I work with, but knew his final assessment of whether or not this configuration constituted Condition for Safe Operation would only weaken the above positions that much more…

Regarding the substantiation of 4 g’s continuous loading, how much above 4 g’s would this structure take (assuming that it was truly 4 g’s of flight loading, at aft cg, at the highest weight the airplane would ever be operated at)?  Unknown, and only truly “knowable” under formal, documented load testing (which would have to allow for measurements of yielding/deformation in the outer .125 plates, in the outer taper pin bores, etc., among other things).  Long and short of it is, the fitting installation/geometry did not meet the structural design requirements, and could not be guaranteed to provide the necessary structural performance over the life of the airplane. 

What if it took 10 more repetitions at x.x (pick a number here…) g’s before more bore yielding in the outer upper plate shifted the load transfer primarily from the outer plate to the induction of local bending moment in the upper composite spar cap due to primary load transfer being mostly/wholly reacted by the inner upper .125 plate???  The taper pin bore in one outer upper .125 plate had already been yielded at least once before, possibly twice, as evidenced by visible material upset/plastic deformation on the 2024-T3 alloy.  This is the sort of circumstance that was quantitatively analyzed (among others).

All told, the players in 1 – 4, above collectively had 10 – 15 some man-hours invested in all of this effort.  No.  It was not just a case of my “opinion”.  The overall situation honestly scared the hell out of me, and weighed heavily on my mind.  Engineering ethics, dontchaknow...

Given the same set of circumstances again, in the future, I would maintain the same position. 

For what it's worth,

Having looked (qualitatively and quantitatively) in at the discrepant wing fitting installation on this airplane in detail, and analyzed (engineering structural/strength analysis) same, you were lucky in avoiding this airplane.  The wing fittings had very, very good potential for not allowing the airplane to carry design 'g' load, and coupled with the epoxy-rich sparcap layups (resulting in the wing fitting plates common to the centersection spar being spaced at least 1/32 inch farther apart than the .375 inch per plans), this was a structural failure waiting to happen.  Failure could have occurred as low as 2.8 g's, and this assumes that the centersection sparcap layups were rendered correctly (so as to react approximately 40,000 psi of stress, which they probably could not on account of epoxy richness).

Two of us, both with proper engineering credentials (myself, I developed airframe repair and modification engineering for 16+ years where I work), came to the above conclusion, and passed this on repeatedly to the most-recent owner, to no avail.  In the end, "better opinions" prevailed.  The loss of this airplane could have been worse if it had been the incorrect wing fitting installation that caused the crash.  At a foot or two of altitude, it could have been bad.  At any appreciable altitude (10 feet and more???) - fatal.

In the exact words of an extremely-esteemed "former RAF employee", when this configuration was bounced off of him, "I wouldn't fly it, would you?"

It will be intersting to see the NTSB final report on this one.

Just because it is a pretty airplane, that does not meant the really important elements (airframe/strucures, flight controls, fuel system, etc.) are also up-to-par.

As I have stated before, it is paramount for buyers of plans-built airplanes to enlist the help of an experienced/qualified BUILDER/operator of the design in question, in order to have a good examination and assesment of the intended purchase.  Each plans-built airplane is unique, and if it does not "conform" to the basic requirements of the plans, one needs to know how/why that is so, and what potential (or definitive) effect the deviation has.

My 2 bits,

-Joe Person
EAA Tech Counselor 4418
VariEze N79JN
Bothell, WA  (KPAE)

Mike,

There are no regulations that pertain to iPods and other miscellany, in the Experimental world.  In an Experimental, there is a whole open realm of possibility - that is part of the aspect of the Experimental category.

Lighting is a different thing.  91.205 is pretty specific, and is required per current operating limitations.  If your airplane was signed off by the DAR (or FAA Inspector) with some sort of lighting system that was intended for Night VFR, you're good.  Post-C/A installation, a bit different.  Oh, people make post-C/A installations/changes all over the place, on Experimentals.  Does not make all of them right.  If one is to have a mishap/accident, and the investigation reveals that you made changes to the airplane in a manner not acceptable (i.e. under the requirements of the airplane's Operating Limitations, as well as all other governing regulations), then one can get into deep yogurt.  Go read up on the Davenport accident and the fuel system changes that opened up a huge can or worms for the owner).

I have always striven for ensuring compliance with all regulations and requirements that apply to my airplane, and have been known to vocally urge that all others do as well (particulary the non-builder owners).  Collectively, doing things below the table can hurt all of us.  Just because it is an Experimental, that does not entail free-for-all operation, maintenance, and compliance to certain things.

I agree that new technology in lighting is the way to go, but installation of new technology lighting still has to end up being approved for VFR Night, per noted requirements & circumstances.

As for your airplane, no, I never tried to buy it, nor would I have ever.  Both of my airplanes were built by me, as that was the only way for me to know that they met my standards for construction, integrity, etc., and the cost was much less.

Two more bits:

When the FARs use the term, "approved", unless the term is used in conjunction with an identified person, the term means "Approved by the Administrator" (of the FAA).

Approval by the Administrator can occur if a product has FAA/PMA approval, for example.  It might require additional approval is installed on an airplane, however.

If a homebuilt was equipped for Night VFR, as part of original construction, then that lighting technically becomes approved, as the issuance of the special airworthiness certificate is done by a Designated Airworthiness Representative (DAR).  The DAR is a Representative of the Administrator, and thus approves as such.  If the Night VFR lighting system was all homebrew, and the DAR approved the airplane thusly, the lighting is approved, even if it does not meet the color, intensity, viewing angles, etc., requirements that are associated with a Part 23 certificated aircraft.

Post-installation of Night VFR lighting (i.e. you decide to equip your Experimental with Night VFR lights after your flight test hours are flown off) would have to comply with §91.205, which requires that the anticollision lighting and the position lights be approved (Approved by the Administrator of the FAA).   How does one do this with homebrew lighting?

Interesting situation.  If one installed the ubiquitous Whelen tip lights (strobe, tail light and position lights), it is probably safely arguable that approved lights, meeting §91.205, are installed.  If homebrew lights are installed, how is one going to demonstrate that the lights meet the "approved" criteria of §91.205?  For Part 23 (type certificated) airplanes, Part 23 has a whole series of lighting requirements applicable to that category of aircraft.

I maintain that if one installs Night VFR lighting AFTER the airplane has its Experimental C of A, the only way to be in compliance with the airplane's operating linitations is to use lighting components that are approved.  Otherwise, one would have to demonstrate to the Administrator (i.e. a DAR) that an homebrew lighting system meets minimum requirements (e.g. Part 23) for lighting systems.

I have a set of "homebrew" strobes I will be installing over this winter, as I like the improved visibility they yield - VariEzes are tough to spot, especially on days when light is dimmed by clouds, haze, etc.  Being that I will not be operating Night VFR in my Eze, there will be no issues associated with whether or not the strobes are approved.

IMO, all Night VFR lighting should meet or exceed the same requirements given in Part 23.  If ya wants to play like a "real" airplane, ya oughta be at least as good...

See Lycoming Service Instruction SI-1505 as a start.  

FWIW, both Lycoming and Continental have several of the more popular Service Bulletins, Service Letters/Service Instructions on their respective websites.  All operators of these engines should spend some time reviewing and researching such data so as to understand more about their engines, as well as to determine maintenance or repair practices that could be beneficial.

Chris,

If you are referring to what is called a taper pin, I may be able to help with a replacement.  This assumes that your Eze was built with the stock Ken Brock VEZ wing fitting assemblies.  I have several spares.  Be advised, there is no guarantee that the pin will be an exact fit - you may need to lap the pin in the fittings, and then always use that pin in the same location.  Generally, Brock-manufactured taper pins seem to be pretty consistent in dimension.

Contact me off-line - ezejoe@comcast.net.

Drew,

If you would like a decent set of guidance material, email me on the side, and I'll zap you a copy.

14CFR Part 1 (FAR 1.1) defines Major and Minor, with respect to definition as associated with Alteration and Repair.

Your Operating Limitations speak to FAR 21.93 - although this Part is applicable, by regulation, to Type Certificated products, the application of the definition of Major & Minor from this Part applies to your homebuilt, per your Operating Limitations.

I short, here is a portion of the guidance material I noted in my opening - interestingly enough, this originated out the Portland FSDO a few years ago, and is titled, "Nortwest Mountain Region - Guide to Aircraft Alterations":

201. MAJOR VS. MINOR ALTERATIONS

a. The definition of major alteration in FAR 1 is: “Major Alteration” means an alteration not listed in the
aircraft, aircraft engine, or propeller specifications-

(1). That might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness;

 or

(2). That is not done according to accepted practices or cannot be done by elementary operations.

b. This definition is reasonably clear except the meaning of “appreciably” and the phrase “...or other qualities affecting airworthiness...”. In this regard, major alteration is considered to include any alteration
which as a result of malfunction or improper accomplishment could:

(1). Preclude continued safe flight and landing in any type operation for which the aircraft is approved;

or

(2). Adversely affect the safety of crew or passengers.

c. A minor alteration is defined as any alteration other that major.

202. DISCUSSION

a. For practical purposes, alterations and changes to type design have the same definition. Part 43, appendix A, provides a listing of product alterations classified as major alterations. This list is not and cannot be all-inclusive. Anyone proposing to alter or approve an alteration to a type certificated product must make a judgement whether the alteration is major or minor. The definition in FAR 1 serves as the foundation to make this judgement. As noted in paragraph 201, the difficulty in applying these definitions is determining the meaning of “appreciable” and “other qualities affecting airworthiness”.

-snip-

c. “Appreciable effect” and other “qualities affecting airworthiness” must be considered for the proposed alteration. Webster’s 9th New Collegiate Dictionary definition of appreciable is “capable of being valued or estimated”. Thus any effect that could be valued or estimated would be appreciable. Appreciable is the value of such measurable effect.

-snip-

f. Performance. Aircraft performance is determined primarily by the difference in the aircraft’s available thrust and the aircraft’s aerodynamic drag in a given flight condition. Any alteration to the aircraft, aircraft engine, or propeller that may affect thrust, drag, or other changes that may affect the airflow over the aircraft, is likely to affect performance. If experience or accepted guidelines have demonstrated that the alteration (such as a small antenna installation) does not produce a measurable effect on performance, then the alteration is minor with regard to performance.

-snip-

h. Flight characteristics are similar to and closely related to aircraft performance.  Thus, any alteration that may produce such an effect, such as a change in the length or width of flight controls or power, is a major alteration.


So, in providing my advice to Dave, I used the guidance from Paragraphs (f) and (h), above.  In my experience, either paragraph could make me make a Major determination for the VG addition.  The big key, for me, is in Paragraph  (h):  "Any measurable change to thrust or drag that affects performance is also likely to affect flight characteristics and requires engineering flight test for evaluation".   Would you, upon putting VGs on your canard, do dedicated and well-documented engineering flight test(s)?  I'd hope so, especially since your airplane is a one-off, not-duplicated-exactly-anywhere, non-Type Certificated air machine.  Just because the VGs worked marvelously on 'ol what's-his-name's Long-EZ, does not absolutely guarantee they will work the same on 'ol what's-his-face's Long-EZ.  The fact that you NEED to flight test, in order to determine what the airplane's new handling/performance characteristics are, would drive me to a Major determination.  Again, Dave's FSDO deemed it a Minor, and again, if you done told the Feds everything, and they reach a conclusion, that'd be it for me...  

So, wheelpants.  Here's my take, from past personal experience.

When I flew my first VariEze, I opted out of installing the wheelpants.  Figured I get to then "next winter".  At Copperstate 1995, Gary Hertzler gently chided me on "dragging those draggy wheels all the way from Seattle to Phoenix".  Having the Master admonish me like that, was a life-changing event...  But I digress in my shame from 10 years ago...

Upon installing the pants, the FSDO said I was OK to proceed, without a new C of A, but that I should still flight test (which is what I planned to do anyway).  Yee-haw!  8 knots more poop on account of the pants.  Flight test also showed that I ran out of forward trim above 135 knots - the reduced pitch trim requirement of the airplane on account of the wheelpant installation required collateral changes in the pitch trim springs.  Did the wheelpants have an appreciable effect?  Yes - Higher cruise speed, and requirement to re-rig the pitch trim system.  A seemingly innocuous change, that I would still classify as a Major change.

I have to deal, literally, with Major/Minor determinations every day at work.  They are not all black/white cut or dry.  Some are, but some are more insidious.  In the homebuilt realm, I prefer the cautious/conservative route, primarily (again) because we are not dealing with airplanes of established Type Design with associated Type Certification.

Enuf, sez I.  I have an Eze in the garage awaiting more meddling.

Hope this adds benefit, and was not too long and hideous to read.

Nitey-night,

-Joe Person
EAA Tech Counselor 4418
VariEze N79JN
Bothell, WA  (KPAE)