The Autogyro does not stall but..... instead
may have another deadly behavior if not properly built!

Igor Bensen built his first gyrogliders and gyrocopters in 1950s and soon started marketing them in earnest. The design was so simple and easy to build that numerous enthusiasts around the world got exited and started to build and experiment with the gyros without full understanding of rotorcraft design, aerodynamics and control principles. I was one of those enthusiasts, ordered the gyroglider drawings and built my first machine in 1957.

As the number of machines increased accidents started to happen. At the end of the sixties it was obvious that a certain type of fatal accident was far too common.  So discussion, debate and wild explanations started to thrive on the possible cause of these accidents. Bensen always faulted the pilot or bad workmanship, never the basic design.

In 1969 the first such fatal gyro accident happened in Pori, Finland, a city on the west coast of Finland. The machine was a standard Bensen B-8m.  I was appointed as the chairman of the accident investigation committee.  We soon realized that the accident was similar to many accidents which were common in the US and elsewhere. This was referred to as "porpoising" or zero-G in the PRA magazine, at the time controlled by Igor Bensen,  designer of the B-8m gyro and originator of the whole gyro movement.  The cause of the accidents was always considered as pilot error, lack of training, etc.  The accidents continued to happen, often to pilots having a lot of fixed wing time. The accident type or cause was later renamed as PIO, Pilot Induced Oscillation, reminding us again that the cause was the pilot, not the machine.  Typically, the machine was first seen "porpoising" which increased to a point where the rotor had a negative angle of attack. At this point the pilot lost control of the machine and it started tumbling.  Rotor rpm slowed down, the blades hit the tail and a terrible crash resulted.  This short description is exactly what happened in Pori causing the death of a pilot having 1000 hrs of fixed wing time.  You can view the Pori accident description in this link but the notation is in Finnish only.

At about the same time another similar accident happened in England to a Wallis autogyro during the famous Farnborough Air Show. The pilot was a very experienced test pilot.  I was in Farnborough at the time but did not actually see the accident happen. However, pictures of the accident were published in newspapers and one can see from the picture sequence below that the rotor had hit the vertical tail and the machine is tumbling down to a final crash.

At the time of these accidents I was flying the ATE-3 gyro, a machine I had built with Aulis Eerola. We had a horizontal stabilizer installed in the machine right from the beginning but decided to test it without one and with a larger V-tail in addition.  The machine was flyable in all the three configurations but proved to be sensitive to fly without a horizontal stabilizer.   The longitudinal stability of the machine with the large V-tail was the best but the lateral stability left something to be desired. So we returned to the first configuration with horizontal and vertical stabilizers.

I wrote an article of this testing in Sport Aviation in 1971 which was immediately reprinted in the WOT (Wings of Tomorrow). I recommended to install a horizontal stabilizer on all  gyros.  I received many enthusiastic letters (example1 and example2) but the influence of this article was very minor and short lived.  However,  I was not completely alone, some months later a similar opinion appeared in September 1971 issue of Helicopter World magazine.
As I expected Bensen did not like my article. When I visited the EAA Fly-In in Oshkosh 1974 he neither wanted to talk with me or take a look at my 8 mm movie of the JT-5 gyro in the air. Regrettably, the end of the friendship. Brock, Wallis and many others did not agree either, not even 30 years later after many, many similar accidents.
The accidents in Finland and our testing of ATE-3 gyro certainly influenced my next design,  the JT-5 autogyro, which was on my drawing board in 1969.  A big horizontal stabilizer was installed. The first flight was in 1973 and the machine proved to be rock solid stable up to the maximum speed of 100 mph.

I sold my JT-5 gyro 1974 to Vittorio Magni in Italy who eventually started to build similar designs having a JT-5 type rotor and good size horizontal stabilizer.  In the following years I concentrated in motorgliders and my next design, the JT-6.  For many years the gyro movement was in the background of my activities, until.........1989 yet another fatal gyro accident happened in Finland.

Again the machine was a Bensen B-8m copy, a Ken Brock KB-3. The pilot was a very experienced fixed wing pilot. You can read the complete accident report in this link.

At this point I decided to write letters to FAA and to Jack Cox in EAA to get a thorough investigation made of these accidents during the past decades and to get something done on the matter.  I got a polite answer from FAA but the message was more or less like.... "We have no regulations for this case. Dont worry, just let them fly and......?"  
Jack Cox from EAA did not answer at all. Probably he sent the letter to Bensen and Brock for comments and...... thats it.  
What I proposed was an accident investigation program consisting of complete statistics of gyro accidents starting from 1960 and a test flight program of gyros with and without a horizontal stabilizer.
However, it proved to be impossible to influence the safety matters of gyros from such a tiny country as Finland (population 5 million), which many Americans apparently considered to be behind the iron curtain.  During the following years I sent  copies of these letters to individuals who had written about the gyro accidents in the press.  I never got a comment.

I don't know if my letter  campaign had any influence at all but it so happened that 3 years later the NTSB finally published the gyro accident statistics (which I had proposed in my letters) including both experimental and type certificated gyroplanes. The NTSB made their own conclusions and afterwards various opinion leaders expressed their views in gyro magazines and papers. The opinions heavily depended on the background of the writer. In general, as before, pilots were considered guilty, not the bad designs.

The accident descriptions in the NTSB paper are quite short and witnesses often were not experts to describe what they saw. In addition the NTSB paper did not mention if a horizontal stabilizer was installed in the machines or not. My own interpretation of the statistics can be seen in the graph below.  By my count, more than 50 fatal zero-G accidents happened in the 10 years time, how many there have been from 1960 to 2000?  
I often wondered how this is possible in the US which has such stringent product liability laws. You only need one nasty lawyer to rake up all this accident history and start very unpleasant actions.

I am encouraged to be informed that the "Magni gyros have an enviable safety record". This is very good news to me– the Magni gyros are an evolution of the JT-5 design and use a very effective horizontal stabilizer!

In 2003 an autogyro symposium arranged by professor Bruce Charnov was held at Hofstra University in New York. Among other influential people in the gyro community I met with my old friend Vittorio Magni and Greg Gremminger, the ASTM gyroplane subcommittee chairman and the USA Magni dealer. I soon realized that there finally were persistent people who really had the same goal as myself, to improve gyro safety and stop the maddening crash record of experimental gyros. And Greg had more persistence, power and prestige than me.

In the US, the FAA initiated the development of new ASTM standards for light sport aircraft. A new ASTM standard for gyroplanes was developed according to a strict  “consensus” process by numbers of influential people in the gyroplane community.

Due to my encounter with Greg at Hofstra University I got involved in the gyro standards balloting. The final result, the ASTM standards for gyroplanes, by raising awareness and knowledge and providing objective criteria by which to determine longitudinal stability of a gyro, is hoped to bring safety improvement into the gyroplane kit industry.

I am lucky I avoided the pitch instability issue early in my gyroplane experiments. However, I had my share of incidents and accidents, some of them very serious.