VG-21 Squadron




March 2011




ISSUE # 63




I have finally retired from Boeing and can now spend more time with airplanes and with the newsletter. I haven't flown as a pilot in command in more than three years and, when my airplane crashed a year ago last November and with some negative things that have gone on here at Falcon Field,  I've been pretty discouraged with the airplane business. Other than occasional additions to the web site, that bad attitude has made it hard for me to even think about keeping up with the newsletter. I apologize for that but now that I have more time and my plane is back on it's wheels with the engine mounted again and it's starting to look like it'll fly again soon, I am beginning to feel better about getting back into the flying game again...


That being said, as I assume many of you know, Lee Beery and several others worked hard on the resolution of the vertical stabilizer spar crack issue that resulted in the Service Bulletin and Airworthiness directive that you should all now have in your hot little hands or at least in the hands of you trusty mechanic... Most of this newsletter will discuss the process that got us from discovery of a serious problem to fixing it but first, we appreciate that Brian Tetrault would like to acknowledge and thank those responsible for the effort that it took to get his airplane back into the air again and to get yours repaired and flying safely again.. .


Vertical stabilizer spar reinforcement

As the owner of the Varga with the first vertical stabilizer spar crack, I wanted the Varga Community to know how much effort and tireless volunteer work went into finding a fix for our birds.  I have asked Max Bishop to publish this in the next newsletter unedited as I believe he would tend to minimize his part in achieving the end results.


The driving forces were Lee and Pat Beery and Max Bishop.  It started on July 6th, 2009 and finished up administratively at least on the 23rd of February, 2010.  There were one hundred and seventy pages of correspondence, twenty eight photographs, thirty four diagrams, an FAA Airworthiness Concern Sheet, an FAA Service Bulletin and an FAA Airworthiness Directive. The effective date of the AD is March 24th, 2010.


Lee and Max drew from their many years of experience in the industry.  They tackled the problem and were steadfast in pursuit of an equitable solution.  Their emails showed up on federal doorsteps practically each day.


Tom and Tina Wasson of Tom’s Aircraft Enterprises and Steve Colvertson of Steve’s Aircraft Repair both at Lampson Field in Lakeport, CA. gave much with their insight and innovative thinking.  Loren Perry, the current Type Certificate Holder, published the service bulletin that Lee and Max wrote.


On the Federal side were Brook Stewart of the Sacramento FSDO, Hal Horsburgh and Cindy Lorenzen of the Aircraft Certification Office in Atlanta .  For the FAA to approve of this fix, this quickly, all the key players had to keep the lines of communication open and the exchange of information flowing.  We thank them.


For a certain few, this was a labor of love and to them we owe a great deal.


Brian Tetreault N1901A

In addition to the thanks from Brian, as a Maintenance Item included at the end of this newsletter, Lee Beery has written a short synopsis of the events and his own thank you for help along the way to the eventual creation of the Airworthiness Directive that has now been distributed and is in the process of being accomplished by most Varga owners.


The Vertical Stabilizer issue: Where it all started and how…

I first learned about this problem while I was Varga Aircraft's Engineering Manager just before Varga closed it's doors in June of 1982…

When someone notified Varga of cracks in a vertical stabilizer forward spar, on what I think may have been a Shinn, I investigated the problem and submitted a report to the FAA describing what I had learned and providing a potential solution, very similar to what the current Service Bulletin provides… 

After the factory shut down, shop foreman Al Wilson and I were running a sheet metal business out of Varga Aircraft's hangar and I was still there when the report was returned to Varga with a reply from the FAA stating that, since this was the only instance of cracks like these that they knew of and that it should be detectable in a normal annual inspection, no further FAA action would be taken unless and until there were more reports of similar instances.

My report and the FAA letter may still exist somewhere in Varga's archives but, at this point, it's existence is irrelevant...

At the time, I was a bit worried that the problem might resurface again some day but, since it was out of my hands, I had no choice but to let it go...

In any event, I was not surprised to hear about a crack when I got an email from Lee Beery but I was surprised to learn that cracks had traveled across the spar web without being detected sooner. It was fortunate that there was no catastrophic failure in flight.  Fortunately, this was discovered in time there was ample opportunity to warn Varga, Shinn and Morrissey owners of the problem. That being the case, I think that I was not as alarmed as those who discovered it or as was the FAA when they were first told.  I will tell you why and continue a discussion about the cause but first I will digress a bit to give you a little perspective (both personal and historical) about cracks... Much of this may seem unrelated to the current issue... but I'll get there...  ;-)

In about 1978, I think, we began to get reports of cracks in elevator control horn flanges on airplanes. After some review of he reports it began to appear that most, if not all, of the airplanes with cracks were being used in flight schools or for rent by FBOs.

A service bulletin was issued requiring 25 hour mandatory inspections and an Airworthiness Directive soon followed.

One airplane owner was so concerned that he brought his airplane to the factory for us to test. One of the first things that we noticed was that the aft fuselage was dented on each side. This appeared to mean that the elevator horn balance arms were vibrating very severely from side to side. But when we did a vibration survey, flight tests and load tests on the part, we couldn't find anything that showed the airplane or parts were loaded or operating outside of the what original design data said it should be and we could not repeat a vibration as severe as the ones causing the aft fuselage dents...

Even though we couldn't duplicate the problem at the time, we knew it was a serious issue so, on advice from an engineer whose opinion was respected by the FAA, we changed the elevator horn from aluminum to steel to improve stiffness and strength. Vibration, flight and load test data was about the same as with the aluminum part and after the design change was accepted by the FAA, we started shipping replacement parts to owners who found cracks.

Unfortunately, after we began to ship the steel parts, even with the Service Bulletin and the AD in effect, there was a fatal accident caused by the failure of an elevator horn...

The airplane that crashed was one of five being used by a company with a Navy contract to test Cadets for suitability as pilots. My understanding was that each student got 15 hours of instructed flight and if good enough, the Cadet was qualified to go on to Navy flight school...

After we shipped new elevator horns to the flight school so that they could continue their program, I got a call from an FAA manufacturing inspector asking if I wanted to go to visit the flight school to help him investigate the problem... I accepted and when we got there, the first thing we did was review the aircraft logs and the four elevator horns that were removed from the airplanes that had had them replaced and were still in use. While the FAA guy examined the logbooks, I looked at the elevator horns we had been given. The logbooks did have all had the correct signoffs at the required 25 hour intervals. Unfortunately, though one of the service bulletin requirements was to remove the paint in the flange area in order to accomplish an inspection, first thing I noticed was that, on none of the four remaining elevator horns, had the paint been removed. 

After the FAA pointed this out to the manager of the company, I was called into his office for a private discussion... Apparently, he had called his lawyer to discuss the apparent discrepancy between the logbooks and the parts and, upon legal advice, I was told that, though I was allowed to stay on the premises, I would no longer be allowed to examine the planes or parts while the FAA representative finished his review so I wandered around in the fog on the ramp until it was time to go home...  ;-)

In the process of our search for a solution, we hired a vibration specialist (a guy named Sandy) to analyze the problem for us. Within a few days of our call to him, he came by with his test equipment, instrumented the back end of an airplane with accelerometers and strain gauges and climbed in the back seat with his recorder to do a flight test. When he reviewed the flight test data on his analyzer he quickly determined that the problem was a resonant frequency that was at about twice the elevator's natural frequency of about 1200 cpm that was so strong during an accelerated stall that the loads at the elevator horn flange, where the cracks were occurring, were greater than either the aluminum or steel material could handle over time. It turned out that the elevator horn/balance weight assembly was a near perfect tuning fork when excited by an accelerated stall when the engine speed was about 2400 rpm.

With this information in hand, Sandy suggested a company that could do redesign of the part for us so we contracted with them to do the job. 

Sometime later, along with a bill for $7,000, we were sent a drawing of a proposed elevator horn and balance arm assembly that was made from solid 4130 steel that weighed twice as much as the whole elevator.

Dismayed by the design I had in hand, I called Sandy to tell him that this was unacceptable and ask him what I should do... He told me that he had an out of state job to do in a couple of weeks and, on his way back in his Twin Beech, if I would come up with a few elevator bellcrank designs that I thought might work, he would stop by and test them to see which was the best...

By the time he got there, I had 5 different elevator horn designs for him to test. The simplest (cheapest) was just an existing steel horn with gussets welded at the forward corner of each  flange and the most complicated (expensive) was the elevator horn design that you now have on your airplanes. I don't remember what the 3 other variations were but I do remember that the test Sandy did was simple, fun and interesting...

Once he had his analyzer set up on a table in my office area, he had me attach each horn, in turn, to the table with C-clamps and after he attached a couple of accelerometers to the horn, he just whacked it with a hammer to see what it's natural frequency was... 

After the whacking... errr... testing was done, it was obvious to Sandy that any of the horns would work but, for political reasons (both FAA and customer), it was decided to go with the stiffest (and most expensive) design. 

From there we proceeded in the next couple of weeks to install a new horn on an airplane and have Sandy come back, instrument the new horn and do a flight test... The result was that the stress on the part went from over 90,000 psi in the old part to less than 10,000 psi in the new...

With that data in hand, we got FAA approval fairly quickly and began manufacturing and shipping the new parts as fast as we could.

OK... what was the point of this long preamble that apparently has nothing to do with the vertical stabilizer? Well... mostly it's about lessons learned about vibration, fatigue and stress but it's a journey and I'll get there...

Here's another part of the journey.  

The Varga Taildragger was originally designed and built by one of our dealers named Hibbard Aviation. In trying to sell airplanes, Hibbard had gotten lots of inquiries about a tailwheel Varga but, heavily into the certification process of the Model 2180 Varga couldn't afford the time and energy required to build and certify a taildragger as well so Hibbard chose to go the STC route and design and build their own.  It took many months but they were eventually able to convert a Model 2150A tricycle gear plane to a taildragger and get it certified. 

Interestingly, about the time that Hibbard finished their certification, a new partner in Varga brought an infusion in cash that allowed us to buy the tailwheel STC from Hibbard and add the 2150ATG to the 2150A and the 2180 model that had been recently certified.

Unfortunately, as it happened, the STC was for a 2150 and then, with the availability of the model 2180, all of our customers with deposit money in hand, wanted a 180HP taildragger instead of a 150HP one...

This meant that incorporating the taildragger into the production line required the addition of the Model 2180 to the STC and lots of extra work for Max and others.

We knew from flight tests done by Hibbard that rudder size and travel was adequate for the 2150 but there was some concern that, although OK for the 2180 Tricycle airplane, in tail low landing conditions, the rudder might not be big enough for the 2180 taildragger so the decision was made to increase it's size.  The new size was mostly determined by guess, appearance and, in an attempt to reduce rudder forces a bit, I also decided to add an aero counterbalance.

Once I had the design, engineering consultant Harold Dale created a report that defined the load test requirements. When we did the model 2180 certification we made a fixture to mount an aft fuselage on it's side with the vertical tail parallel to the ground so that we could do load tests on the original rudder and vertical stabilizer to show that tail power was adequate for the higher horsepower engine. So, when we needed to test the new rudder we were ready for that.   For the 2180 tricycle gear, the original rudder easily passed it's load test but what was interesting was that, it flexed so much that, as we added lead shot bags, the shot bags began to slide off... Since the rudder returned to it's original shape when the load was removed, no one was concerned that it wouldn't do it's job...

In noting that flex though, when I designed the new rudder, I decided to add an additional spar to stiffen it some, which ended up working well....

To finally get to the point, we used the same vertical stabilizer and aft fuselage for both tests and in neither case did the vertical stabilizer suffer ill effects from multiple tests to an ultimate load and that led me to believe, when I heard about them, that the resulting cracks that we now see were not the result of static load or overload conditions but to fatigue. 

That conclusion led me to believe that we didn't need to reinforce the stabilizer for strength but we did need, in addition to stop drilling the cracks to keep them from traveling, to stiffen the stabilizer joint enough to get it's natural frequency away from the destructive one that was probably due to propeller vibration over time at some resonant propeller RPM...

There was no vibration analysis done but stiffening the spar is essentially what the doubler that Lee and company designed did and was, as I said above, about the same as what I proposed as a fix almost 30 years ago...

The process of getting the fix approved was a bit painful but all in all the FAA was very helpful and we all owe, along with Loren Perry and others, Lee & Pat Beery especially, an enormous debt of gratitude... 



For those of you who don't know, I am the former Varga Aircraft Corporation engineering manager (1975-1982) and may be able to help you with a problem. I can be reached at:


VG21 Squadron

Max Bishop

2062 West Gila Lane

Chandler , Arizona 85224

(480) 786-3578 (evenings)

(480) 201-6553 (cell)

You may also may be able to find me at hanger RR2 at Falcon Field in Mesa, Arizona, now that I am retired, most any day of the week except Sunday.  


VG-21 Membership: A $20 annual donation to the above will help to cover all the printing and mailing costs for as many issues a year as I have time for and for web site maintenance costs and help pay for return phone calls, letters and postage when you have questions or comments that require a quick or personal response. Beery VG-21 Newsletters: $10 covers most of the printing and mailing costs for all the archived issues. Old Bishop VG-21 Newsletters are $2.00 each (includes postage).  


I plan on publishing a current membership roster in the near future but, for privacy reasons, don't want to include any information that members don't want to make public...  I will let you know by email when the roster is ready so, at that time, you can let me know what info you do or do not want included and, once edited, will then mail the membership list to those who request a copy...


I could put a list here on the web site for those who don't care about publicly listing their name address and phone number but to some, that may be unacceptable. I've thought about making this site more like a weblog with password access but, from what I can tell, it's a lot of extra time and work to do that and, at this point, I'd rather not...


New Members:


Ned Collins, Tucson AZ, N5070V

Jack Reynolds, Bolivar, MO, N5083V

Joel Scotland, Gardnerville, NV





It's been so long that I have too many emails to post so I'll start sorting them out and picking up on some of them in my next issue...


Max Bishop





1977 VARGA 2150 TG

Lyco O320A2C 150 HP TSMO 239 Hours











Contact Don at:

Hm: 636-488-5218    Cell: 636-357-8322




Parts / Service / Tools  


12-24 Screws are still available for Landing Gear Hydraulic Fluid and Lubrication holes:

I have 3 boxes of the 12-24 screws that are used to plug the 2 filler holes at the top of each landing gear. 12-24 screws are an oddball size so, if you need and can’t find any of these screws, let me know how many and I’ll send them.


Stabilizer Bushings:

I still have lots of horizontal and vertical stabilizer hinge bushings left if you need them…


Aileron & Flap Hinge:

The Varga uses NAS40-6 hinge at the wing and NAS40-10 hinge at the aileron and flap.  I have a couple of 6’ lengths of NAS40-10 hinge. I don't have any dash 6 hinge but it is narrower and the dash 10 hinge can be cut down to the dash 6 width...


Main Landing Gear (lower)


Other Varga Stuff:




Max Bishop


Please don't hesitate to provide suggestions for subject, content or format changes or corrections to this web site or the newsletter at any time. Questions and comments about Vargas are always welcome....  



  (by Lee Beery)


This Maintenance Item is to give the VG 21 members some insight into the new AD 1020-04-14.  As you recall in the last NL, Max reported the problems found on the vertical stabilizer on several planes.  I will tell you briefly what transpired.


Being a licensed mechanic, I must report such findings to the FAA, which I did, and they promptly grounded the two planes [Brian Tetrault and Lee Beery's] .  The FAA Designated Airworthiness Representative for our area said the repair was beyond his authority and directed us to the FAA Designated Engineering Representative [DER].  The DER wanted $1600.00 for the fix on the primary aircraft and then $800 each for every aircraft that was repaired after that.  This left us with paying a huge price for his service or doing our own design work and getting FAA approval by using a “one time” field approval, a form 337.  It took four submissions of a 337 and 60 days. The actual time to disassemble the tail, fabricate, and install the doubler, reassemble the tail and check everything out was only about 14 hours.  There has never been so much activity at the Varga Service Center – ever!  Tom, of Tom’s Aircraft, spent many long hours working on this project.  Steve of Steve’s Aircraft Service provided a lot of insight as to how to work with the FAA.  Approval for the second Varga came within another twenty days.


I was told by more than one rep from the FAA that what we achieved was rare and could never be done in less than a year.  I’m sure this would have been true had it not been for Max Bishop who was called upon many times for information and we even called up retired aircraft engineers who I worked with before I retired.  The biggest thanks goes to FAA Engineer Horsburgh as he provided guidance the entire time.  There was a great deal of technical data going back and forth between mechanic ranks and engineering gurus.  Pat, of course, was doing all of the correspondence for me so many thanks to her. 


Max and I collaborated on producing a Service Bulletin for Augustair and I want you to know it was 3 pages long, not the 22 pages that were published.  On the negative side of all this, some individuals feel we created all this just to make this miserable and to spend their hard-earned dollars.  Guess you can’t make everyone happy!