Author Topic: "Tigers in a Cage"  (Read 6732 times)


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"Tigers in a Cage"
« on: June 18, 2011, 08:46:40 PM »
I have mentioned earlier and on several occasions that I was embarked on a mission to write a book about the Helio. It has been a work in progress for about 3 years. Work schedule and other things have delayed finishing it. When that time comes, you will be the first to know.. In the meantime here is an excerpt.


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Re: "Tigers in a Cage"
« Reply #1 on: June 18, 2011, 08:48:28 PM »
   Tigers in a Cage:  Helio Aircraft Company

                                     "Extreme short field airplanes" 

                                                                                       Stephen A. Ruby  EAA #406241


        Jack Phillipps flew the test flights out of M.I.T. athlectic field in 1948-49 after Dr. Otto Koppen and Prof. Lynn Bollinger came up with the concept of an airplane that was stall-proof and spin-proof converted from a Piper Vagabond PA-17. This conversion was an airplane like no other, handley-page automatic leading-edge slats, a rudder split in two-sections, the top being the trim, the bottom being the rudder, with the wing span shortened sporting modified slotted full span flaps and the landing gear moved forward ahead of the firewall to allow hard braking on rough field operations preventing a nose over. To further the performance enhancements an 85 h.p. Continental with fuel injection and a geared V- belt driven mechanism turning a 9 foot wide-chord Aeromatic propeller was installed. The result was an airplane that could fly at 27 mph and take-off with one pilot before the throttle was fully opened, about 60 FT. in still air, normally about 100 FT .at gross and clear a 50 foot obstacle less than 300 FT.

       Dr. Otto Koppen an aeronautical professor at M.I.T and Prof. Lynn L. Bollinger business research professor at Harvard Business School, were engaged in the design of an airplane that put extreme safety ahead of anything else. Dr. Otto Koppen was not new to designing slow flying safe airplanes afterall he designed the Ford Flivver and the General Aircraft Skyfarer. Otto Koppen had on occassion experienced loss of control flying into airfields around New York and Boston. This loss of control resulted from wind shear and turbulence generated by tall buildings in the same manner as "mountain wave effect" in high altitude operations. Otto Koppen was nearly killed when he departed from controlled flight on a few occassions. These test flights conducted at Boston Athletic Field and Harvard University tennis court were proof of concept evaluations that earned the Helioplane a place in history known as the "tennis court" airplane. Pitch control remained questionable because the elevator had not been modified and retained the same shape as all short wing Pipers have. This radically modified experiment is now known as the Helio C/STOL Courier (controlled short take-off and landing). In 1950 the Helioplane Four was introduced, it became a more polished, refined airplane, resulting in the only fixed wing airplane that had an all flying stabilator, shoulder harnesses, and a 15G tubular steel roll cage surrounding pilot and passengers. Fleet Aircraft Co. LTD in Canada agreed to build them, but that deal fell through, so Aeronca Aircraft in Alliance, Ohio agreed to build them.  The Board of Directors conceded that Aeronca could build them for $6750 and a out-the-door price of $9270 where a profit was established.  Hostilities in Korea broke out and as a result all light airplane production in the U.S. sadly, came to a screaching halt. 1952 the YL-24 was under evaluation by the U.S. Army  and it looked promising for Helio Aircraft to undertake certification and production performing in the liason/observation role with military officials developing a keen interest in the project. In particular the Helioplane

  The airfoil in the Helio is a NACA 23012 design that is the same section as the P-51, a hershey bar wing with 231 square feet of area that incorporates "frise" (freeze) ailerons, these are fabric-covered, card table sized control surfaces providing superb roll control at low speed and when deployed the aileron is lifted where the leading edge protrudes into the airflow enabling a condition to develop called "proverse yaw" thus practically enabling the pilot to turn the airplane with almost no rudder application. On the upper surface of the wing just behind the slats (15.5% chord) there are curved blades called "interceptors" recessed into the wing that give 16 to 20 degree roll rates per second margin at less than 40 mph. These interceptors pop out of the wing when normal roll control is lost at low airspeed, and are activated when the control yoke is moved to near maximum deflection. The designers obviously did their homework. The trailing edge of the wing encompass modified slotted flaps that extend out and down and comprise an area of 74% of the span, and when all devices are extended the Helio exhibits 100% more lift than any other airplane. The standard fuel system incorporates two 30 gallon tanks constructed of nylon, rubberized, collapsable bladders that conform to shape in the event of an accident which has shown Helio possessing the lowest post crash fire rate of any airplane produced. There is also a provision for 120 gallons in later versions (U-10D).. This Ichabod Crane of the air, is a thing of pure beauty.
Canyon turns, hovering, and aerial shenanigans

     Helio U-10's performed amazing work in the jungles of  Laos, Cambodia, Thailand, and VietNam after expert persuasion on the part of a Major Harry "Heine" Aderholt who convinced the CIA that insertions into mountain tops providing operations that could only be served by an airplane with these capabilities. In 1958 Helio Aircraft developed the Super Courier with a Lycoming GO-480-G1D6 (295 hp) designated the L-28, and later became the U-10A, which were flown at various military bases around the counrty, FT. Bragg, NC, and Hurlburt Army Field in Florida. By now, the advisor program was under full swing in Southeast Asia and it became clear that supplies, interdiction missions, and support were ncessary to help the people of these countries combat communism. Thus, Air America became a reality and the airline of the VietNam War was born. The Air Commando's went to Southeast Asia in November of 1961, along with the U-10, and that airplane flies today, but what is interesting is that the CIA had been secretly involved with Helio Aircraft already, and it is rumored that 6 U-5 Helio twins ended up in Communist China, only 7 were built. The mission envelope flown was one of battlefield surveillance where recon data received indicating Viet Cong stronghold activity at peak staging zones, which included deployment of the U-10 to orbit suspected area's to monitor and persuade the enemy to convert to South Vietnamese forces and having amnesty available so that we could gather intelligence and instruct them to surrender. A Pilot, Radio operator, and door kicker boarded the U-10 and orbited these specified areas and began taped speech through loudspeakers installed in the airplane translated to Vietnamese. The "door kicker" would toss out Chieu Hoy (Open Arms) pamphlets encouraging them to relinguish their activities, it was met with some success. Ground fire was always present and there were bullet holes in any number of U-10's at any one time. Mission pilots soon learned to develop evasive tactics that employed the Helio's unusual attributes and when ground fire return was imminent, you simply yanked and banked a 180 degree turn all within the space of a runway, about 100 feet. The Lycoming GO-480-G1D6 "geared" engine really proved it's worth in this situation and was hailed as difficult to operate by some operators who flew Aero Commanders and Twin Bonanza's. Not exactly a high time TBO powerplant (1400 hours) but the GO-480 proved to be a bullet proof motor and worked when needed. A variety of other aircraft utilized this engine and it incorporated a planetary gear driven mechanism allowing 3400 rpm at take-off with the prop turning 2175 rpm. The confined areas in which the U-10 operated were generally above 4,000 feet in mountainous jungles with continuously adverse weather conditions, flight ops out of 1,000 foot airstrips were met routinely. NKP (Nakhon Phanom) Air Base was located 360 miles northeast of Bangkok, Thailand and was one of those clandestine area's and the subject of this article. When congressional hearings disclosed activity of American Forces in late 1969, and early 1970 operating secretly out of Loas, the cat was let out of the bag so to speak, and operations began to move elsewhere with skepticism by military officials who felt our presence there would enable combat operations to gain greater control of the North Vietnamese Army and force their surrender, that never happened. When I arrived in Viet Nam in July of 1969, the U-10's were operating out of Bien Hoa Air Base engaging the same role and flown primarily in the southern part of the country and relegated to lesser participation. In April of 1975 it was all said and done, thus the costliest conflict of modern times met it's fate and came to a bitter conclusion.       

     The Helio H-391B certified in July of 1954 under type certificate #1A8 has flown numerous demo's at EAA AirVenture and that airplane is now retired, the ruggedness and flexibilty of it's design has yet to be challenged and provides operators with a degree of safety not found in any other single-engine light airplane, and continues to serve routinely in the furthest reaches of the world. About 220 Helio's still fly.   

Helio Stallion AU-24 (A)

     The Helio Stallion developed in late 1963 and test flown in July of 1964 (type certificate #A4EA) can best be described as the highest performing single-engine turbine, fixed gear STOL airplane, ever conceived. Helio Aircraft was in competition with 2 other manufacturers so the theory was to develop an aircraft that could rise above the competing entries and gain the bid for the military role of "armed gunship" escort. Helio decided that instead of converting the Courier they took the approach to a new design concept unlike Pilatus did with the Porter, the result was an 8-11 place transport equipped with PT6A-6 (550 shp) or the Garrett TPE-331-2 of (600 shp) due to numerous teething issues with gear box failures and hot section problems it was decided that the PT6 was the favorable option. The Stallion is similar to the Courier because it uses the same wing with a bit more span (41 feet) and 242 square feet of wing area, otherwise no comparison can be made, it is a different animal. The fuselage is 39.7 ft. and the prototype retained the 15G roll cage extending to the back of the cabin, the landing gear is at the same location ahead of the firewall but raked back at a 41 degree angle keeping C.G. locations where they should be. The first Stallion was demonstrating throughout the country and N10038 performing short-field antics that can be labeled as extraordinary. The Hartzell 101" inch 3-blade could be reversed and in excersing STOL landings the airplane was planted on the tarmac, stopped in 150 feet and backed up to the take-off point, gaining much curiosity from ATC controllers.

    Take off in the Stallion resulted in much the same response, but here is where the airplane became a bit unusual, it would achieve extreme angles of attack and in doing so, scared off many commercial operators when Helio performed sales demo's. It was clearly evident that climb rates beyond 3500 fpm were attainable and you could put the nose to 43 degrees or beyond in high performance climb out's, this is what extreme attitude is all about in STOL operations, right? Well, problem is roll control suffered so much that behavior in lateral stability required judicious aileron inputs that wore out potential customers after an hour of dual in turbine single-engine calisthenics, leaving pilots exhausted. Another condition existed when the Stallion entered steep descents, it demonstrated unusual characteristics in the descent profile, she would develop longitudinal "porpoising" at high speed, nose down, when the prop was placed in near "Beta" setting, the only remedy available was adding power and arresting the condition after achieving 11,000 fpm at 80KTS, downhill.

     Helio Aircraft decided to go back to the drawing board and come up with something more acceptable and in August of 1969 the Helio Stallion HST-550A was awarded FAA certification. Billed as the "fastest fixed gear STOL" airplane in production the FAA required Helio officials to install a SFAS (stick force augementation system) where as airspeed decreased and angle of attack increased, a stick force of 50lbs. was added to pitch control by means of limiting stabilator deflection much like the stick shaker in the Learjet. A vane on the left wing and tube rod assembly in the dorsal fin accomplished this goal. U.S.Air Force brass began negotiations to find suitable aircraft for it's "Credible Chase" program in the PAVE/COIN armed gunship role, the contenders were the AU-23 Peacemaker (Pilatus Porter) and the AU-24 Stallion and it is rumored Fairchild Hiller built both airplanes under contract at the same facilty in Maryland, yet no civilan sales occurred.

      Helio Aircraft at their Board of Directors meeting in the late sixties, under the auspices of General Aircraft Corp. were faced with financial pressure from lack of these civilian sales. The military just might save the Stallion program and the other theory is Helio may have gone bankrupt because of monetary input transferred to this project, but as fate would have it the Air Force ordered 18 aircraft to be evaluated for their pet program. Armed with 20MM Gatling Guns, 4 hard points for rockets, and a provision for the 500 lb. bomb beneath the fuselage, testing and evaluation commenced and construction underway. Of interest here lies the fact that fact that Helio also placed all bets in the military contract business and neglected the commercial market altogether and they certainly did so with earnest, thus the lesser powered Helio Super Courier H-295 with all it's glory became prohibitively expensive at $41,900 base list price and no accessories. STOL airplanes fit neatly into the "specialty market"

     The AU-24's deployed to Southeast Asia in 1972, were based in Thailand and used against the Khmer Rouge and communist forces from Cambodia, in a variety of escort duties all under combat conditions, at night, in heavy weather. Stallions were flown up to 240 KTS at altitude, and 205-210 KTAS down low (50 feet) routinely. In all 15 Stallion's were deployed to hostilities 10,000 miles away and by 1974 it was about over for US involvement in this overtaxed, overburdened conflict. The CIA built Helio's offshore at the taxpayers expense and was the subject of a bitter lawsuit that resulted in Helio settling out of court for $50,000 dollars, in all, about 2,000 airplanes were built between 1954 and 1974 when Helio closed it's doors. The military veterans who served in this capacity are to be remembered with honor, it is with their sacrifice that our freedom is still that, free. Only 2 Stallions remain flyable and their stories could tell all, if airplanes could talk, but some of those "speaker bird crews still can. A big Thank You goes to Dennis Petersen (U-10 pilot) who served with the 56TH ACS for providing me the pictures you see here........

     The Helio may never be built again, but those still remaining active have in some way fulfilled a purpose in aviation not many can claim, and they're called "tennis court" airplanes......

      Helio Super Courier U-10A/B Specifications:

         Wingspan: 39 FT.

         Length:      30.6 FT

         Wing Area: 231 sq. ft.

         Airfoil: NACA 23012

         Gross Weight: 3600 lbs. (Military) C.A.R. 8 (3920 lbs.)

         Empty Weight: 2300 lbs. (Average) 2037 lbs. Book

         Fuel Capacity:   60 gals. Plus a 25 gallon tank that can take place of the 5th seat

         Max.Speed: @ sea level (3000 lbs.) 176 mph

         Cruise: 75 % pwr. 170 mph at 8200 ft.

         Min. Speed power on: 28 mph

         Min. Speed power off: 31 mph

         T.O run zero-wind: 217 ft.

         Landing run zero-wind: 169 ft.

         Range at economical cruise: 800 miles   

                  Helio Stallion AU-24(A)


            Wingspan.............................. 41 FT

             Length.................................. 39.7 FT

             Height..................................    9.3 FT

         Powerplant :

             Engine................................. Pratt & Whitney PT6A-27 (680 SHP)

             Propeller.............................  Hartzell 101 inch, 3-blade, reversing

        Weight and Load :

           Gross Weight....................... 6300 lbs.

             Useful Load......................... 3070 lbs.

         Takeoff Distance....................... 560 ft.

              (Sea Level, ISA)

         Landing Distance:

              (Sea Level, ISA)....................... 320 ft.

         Rate of Climb:

               (Sea Level, ISA)...................... 1550 ft./ min.

         Max. Cruise:

                10,000 ft. @ 6300 lbs.............  160 kts

                 Min. Fully Maneuverable......     38 kts

         Range :

                 Standard, 120 gals..................  550 nm

          Service Ceiling:

                @ 6300 lbs............................   20,000 ft. 



Re: "Tigers in a Cage"
« Reply #2 on: June 18, 2011, 09:13:55 PM »
WOW! Excellent Stephen!   When they say that the structure is 15G steel tubing, does that mean that its thickness is 15 gauge or that the whole assembled structure is rated to survive a 15 G (gravity force) impact?    Paul


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Re: "Tigers in a Cage"
« Reply #3 on: June 19, 2011, 08:19:31 PM »
The entire roll cage including engine mount, seats, and shoulder harness are rated to a 15G impact, incidentally the wing carry-thru in it's original form can take a 50,000 pound test load.

Doug Johnson

Re: "Tigers in a Cage"
« Reply #4 on: June 29, 2011, 06:51:41 PM »

I question your statement that 2000 Helios were produced. The factory record show about 525 even if another couple hundred were produced by factory under black ops programs and excess parts, and if we are generous and say that the CIA produced  another couple hundred we should stumble on to a wrecked Helio or one with out paperwork. It just doesn't happen.

I concede there is documentation of seemingly questionable parts in the Indochina/Indonesia area. I suspect there was closer to 900 to 1000 Helios built
750 legally another 250 that were in all honesty unauthorized replacements.

Every wreck or Helio I find eventually tracks back to a factory construction number.

I'm sure Helios were built in the Air America repair facility using nothing but the data plate. Some went out without a Data plate but I would think that they were eventually tied to a Valid construction number. I think it comes down to a goverment workers eventual accountability and freedom of information policies.

When I was visiting a shop in Alaska I think it was called Cub crafters they said no cub isn't rebuildable as long as we have a data plate. I think this is the case here.

If you think I'm wrong feel free to beat up on me. But please post some facts and numbers to substantiate your claims.

Thanks, Doug

The Air America Years (Part I)   
Excerpt from:
John Deakin (Air America
The story was told of a huge maintenance barge that moved down-river on the Mainland as the tides of war shifted. City after city fell to the communists, led by Mao Tse Tung. In 1949, the last cities fell, and the barge was moved across the Formosa Strait to Tainan, Taiwan, where it grew into the maintenance facility we were about to visit.
It was nothing short of mind-boggling, and no briefing could prepare me for it. It was, and remained for many years, the largest maintenance facility in the world, and it was all top-secret. That facility was fully capable of rebuilding a whole airplane, from scratch, and often did. Helio Couriers would come in from Laos as a small pile of mangled and bloody wreckage, and leave as shiny new airplanes, some with the original data plate, and others with none at all. Most of the "business" seemed to be U.S. Military airplanes, in for overhaul, modification, or maintenance. It was a beehive of activity in 1963, and it grew exponentially during the following decade, with Vietnam.
« Last Edit: June 29, 2011, 06:57:07 PM by Doug Johnson »


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Re: "Tigers in a Cage"
« Reply #5 on: June 29, 2011, 07:02:50 PM »
You can question all you want, but the facts are facts and I have personally talked with the lawyer who handled the case for Helio Aircraft Company in 1975.

You can come up with explanatory evidence found on the net, that's easy and most of the stuff you read has been handed down through various means. The CIA doesn't need a data plate for anything they do off-shore, they didn't when there were production facilities in places like Hungary, Romania, Beirut, Thailand, India, and Pakistan dating back to 1963.
« Last Edit: June 29, 2011, 07:11:58 PM by greatlakeshelio »


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Re: "Tigers in a Cage"
« Reply #6 on: July 07, 2011, 06:48:13 PM »
 This business of the inner team of workers, all actually operating within the law (once in a while there was some aberration, but we usually found it and brought it to Mr. Dulles' attention -- but, generally working within the law) could get rather phenomenal things done.
For example, one day I got a call from the agency. They had heard of the capability of a new aircraft that had been designed at MIT and they wanted to know if the Air Force had an interest in it. The Air Force hardly knew about it. I had seen a picture of it in the newspaper. The plane was the Helio Courier manufactured by the Helio Aircraft Co. And I said, `Let me find out what we can do about that.' I called the company. A small company -- but it had very preeminent people including Dr. Koppen from MIT and Dr. Bollinger from Harvard Business School, as well as a lot of very good aircraft designers and builders. So, the company was solidly on the ground but it was very small. I told the man I was talking to that I was a Colonel in the Air Force, that we had an interest in this small plane for certain special activities, and that I would send a representative of my office up there to talk with them.

I called in a CIA man -- the same man that had called me -- and said, `Look, you're from my office, here's some credentials -- you go up there, you see this company. You know what you want.' I didn't know whether they'd really want the plane or not. But they decided they did. In fact, they wanted hundreds of them -- something that company had never heard of before, orders in that number. We bought hundreds of those airplanes for the CIA, technically for the Air Force. The Air Force had no concern with this because the CIA money paid for it -- it didn't cost us anything -- and we didn't go through the Air Force procurement procedures at all. We were just like a civilian company buying airplanes.

The CIA was delighted with the plane. They used so many of them in Southeast Asia that there was a flyer's handbook for what were called Heliostrips. In other words, air landing grounds that only the Helio airplane could land on, because it could land in a very short space, and it was under full control right down to the ground. Some of these little runways were hardly suited for helicopters but this little Helio plane was operating regularly.

Millions and millions of dollars were poured into that exercise -- a lot of people were involved in it -- and it never went through any Air Force procurement. However, the cleared individual -- the man in the team -- in the procurement offices, made papers that covered up this gap. There were papers in the files but they had never been worked on -- they were simple dummy papers. We could do things like that with no trouble at all. The U-2 was started like that. That's how the U-2 got off the ground. Ostensibly, purchased by the Air Force, but not paid for by the Air Force, and so on.

Doug Johnson

Re: "Tigers in a Cage"
« Reply #7 on: July 08, 2011, 08:37:50 AM »

"In fact, they wanted hundreds of them -- something that company had never heard of before, orders in that number. We bought hundreds of those airplanes for the CIA, technically for the Air Force."

Who is the is the "man" and the "man" he is talking to? I remember reading this interview or one very similar some time ago.

The facts or rather believable facts is what I've been trying to pick out by putting numbers together. When ever I find a Helio out of the country it eventually leads back to a legitimate construction number. I have no problem believing in 150 black ops Helio's that disappeared into thin air, its a big world out there. 14 hundred I have trouble with.

At first I had trouble with the 50,000 dollar settlement because it seemed like such a small amount, especially if there were 1000 extra Helios out there some where. But after thinking about it, I realized that the settlement was probably for lost profits so that probably was 500 to 1000 dollars which in turn relates to 50 to 100 airplanes

I remember a rumor that there were several to dozens of Stallions that the CIA had abandoned in South America. I believe that there was one Tim  Greenes.

I'm going to attach the bill of sale for Tim Greenes stallion which shows air america as the seller, and the serial #001 which makes it the second #001. N500HE is the documented first #001.

250 of the 550 factory Helio's were built for the Army the Air National Guard or  US Air Force about 50 of these aren't really accounted for.


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Re: "Tigers in a Cage"
« Reply #8 on: July 08, 2011, 10:53:12 AM »

I'm not in the position to get into a boxing match with this issue. Tim Green's Stallion is serial #001, it is the airplane that the military originally flew. They wanted sticks instead of wheels and a left hand throttle quadrant which led to Stallion number two and was awarded FAA certification in August of 1969.

There are no legitimate c/n numbers for airplanes being secretly in foreign countries, and those numbers cannot be traced to anything.

Doug Johnson

Re: "Tigers in a Cage"
« Reply #9 on: July 08, 2011, 03:27:38 PM »
I'm not trying to get in to any kind of match.

Probably in some respects I'm nit picking, erroneous information even my own especially my own drives me to distraction. If my facts are in error  please point them out.

I'm just airing two slightly different points of view.

We've met some of the same people in the past and probably came away with slightly different impressions Larry was the person that thought there was might be several stallions in south america but didn't know where they were. Dean Tremaine agreed.

For a long time I was sure there were a bunch of Stallions some where in south america.

In the not to distant past I realized I was confusing a modest bunch of Jaars standard Helios with one Stallion in Columbia .

my next confusion was the three prototypes HST-1 and HST-2 (maybe there were really 20 Helios) but I found that the Helio LLC was adamant that only 18 helios were built and that prototype HST-2 N9550A was used as construction number 001.

But what happened to prototype HST-3 N9551A? Was it used as c/n 002? But I had pictures of it, and N70850 c/n 002 (maybe there were really 19 Helios built and the Helio LLC was mistaken?) I was really confused.

I found the military contract (72-1319 to 1333) after doing the arithmetic twice and counting on my fingers it came to 14 but I had construction numbers 003 to 018 (15) being delivered to the military after doing a bunch of checking and number comparing I finally concluded that c/n 005 was never manufactured.

I also had information that 14 were delivered to the Khmer AF under Military the assistance Program. Later I found information that  009 was never delivered which leads me to believe only 13 actually went to Cambodia. In different ways those 13 can also be accounted for.

My only point in bringing Tim Greenes HST-1 N500AA second c/n001 with its Air America bill of sale and David Maytags HST-2 N500HE first c/n001 (according to David Maytag) into the conversation, was to show the ease of confusion and maybe how some numbers have possibly become mixed and inflated over the years.

My other point that when ever I find a wrecked Helio, and airplane crashes are big news in any country or a Helio picture or reference to a Helio it always leads back to a legitimate c/n. My thinking is that 14 hundred illegal Helio's is a lot of airplanes to vanish into thin air no matter how big the world is and how many covert operations there are. With that many, a needle would seem to shake out of the stack once in a while. I believe there were a couple of hundred illegal Helios, but that's all.

I hope that we can agree to be friends. I think we are looking at the same facts from two different directions and getting two different opinions.

Who knows maybe someday we'll meet in the middle? I'm certainly not absolutely convinced I'm absolutely correct.
« Last Edit: February 26, 2012, 07:47:12 AM by Doug Johnson »