History of Gyros


Platinum Member
Hello gyronuts
I am writing a piece about gyros, just passing the Bensen years, need some info about
How Bensen created his gliders? Thought process
Who configured the CLT gyros, in special the Air Command?
thanks in advance


David McCutchen
last year I went to a "Mini Maker" fair at Vanderbilt University ; and had my dominator and a Kolb ultralight on display. There was a elderly gentleman there, which had a display also. He had a Bensen clone that was podded up to lool like "Little Nellie". He had a lot of articles and historical information with him. He was a Colonel in rank.
I had a very lengthy conversation with him that day. As I recall his story, it went something like this.
I am assuming after the fall of Germany in WWII.
He said they were on a beach and about 1/3 of a mile away was a concrete bunker. Housed within the bunker was a German Submarine, and a few gyro gliders. He said that Dr. Bensen was there as an employee of General Electric and was designing water "turbines" propellers. I assume to be used in hydro electric dams. He said Dr. Bensen was really intrigued with the gyro housed on and in the Submarine.
We know from Dr. Bensens story, that he brought the gyro glider back to the USA for testing. General Electric say no practical application or the ability to produce a profit so the entire project was aborted. Dr. Bensen took the remnants of the program and started building and testing on his own. There was the birth of "Bensen Aircraft Co." and we know most of that history.
You mention CLT.
The B7m and B8m models were designed around a McCulloch or Volkswagen engine. Using his plans and either of these engines, and the gyro was very very close to CLT.
These designs did not have a functioning horizontal stabilizer either. Flown properly by an average skilled pilot, they are quite safe and fairly pitch stable.
The McCulloch "Mac" engine developed a fairly nasty reputation for quitting. Builders started using the Rotax engines and wanted larger diameter propellers. The standard Bensen frame with a VW or Mac accommodated a 50 inch prop. To accept the larger diameter props on a Rotax, the builders would just raise the engine mounting location on the mast and get the distance they needed for the propeller clearance to the keel. Not realizing they were building a HIGH thrust line, pitch unstable machine. I believe that is where the bad reputation got started on the Bensen B8 design.
Last edited:

Doug Riley

Platinum Member
This account combines a few details.

The German-submarine gyroglider was a Focke -- the same company that produced the first controllable helicopter, famously demonstrated by flying it in an indoor arena around 1938. The Focke gyroglider had a 3-blade rotor.

Igor Bensen may have been intrigued by the Focke, but his gyros were derived not from that model, but from the free-flying Rotachute developed on the Allied side by Raoul Hafner. Its intended military function was to substitute for a parachute in infantry air-drops. Igor's earliest gyros were very, very close to Hafner's in design, right down to the overhead stick.

Bensen's B-7 was designed around the 40 hp Nelson engine. The B-7 had quite a substantial H-stab; the B-8 had almost none.

The B-8M proved to be a prolific killer of unwary amateurs. It had fast, light rotorblades and its short-coupled little H-stab made no handling difference (that I could notice anyway).

Ken Brock's version of the B-8M, with light wheels and a seat tank, may have been close to CLT, but the stock Bensen wasn't. It had very heavy, iron-hubbed industrial wheels and a steel outboard-motor gas tank mounted low. There was some degree of HTL which combined with very low rotor damping to make a machine that was very prone to pilot-induced oscillation a/k/a porpoising.

Once you learned to under-control and let the machine catch up to you, you were largely safe from porpoising. Many died before they could get this straight, however. Arguably a machine marketed in Popular Mechanics to non-pilots should have been more beginner-friendly.

At one point in the late 60's, the B-8M was killing about one pilot a month. We have yet to live down the horrible reputation that this disgraceful situation earned for gyros.

The introduction of offset redrives around 1980 made the HTL situation much worse for awhile, of course.

We've turned the stability problem around with CLT, H-stabs and much heavier, slower rotors than Bensen used. We'll see if the reputation problem likewise turns around. We've had quite a deep hole to dig out of.

C. Beaty

Gold Supporter
I’ve seen photos of Dr. Bensen flying the Rotachute at GE’s Schenectady flight test center.
Here’s Bensen’s patent for landing gear controlled by the pilot’s feet. That’s sorta duh but what is interesting is the accompanying drawings showing his water pipe version of the Rotachute with overhead stick and non underslung seesaw rotor. A jackhammer ride for sure.

I believe that most if not all were modified changing the design. Changing the height of the motor at the mast makes it an entirely different machine. Even though the Bensen plans stress that no changes or modifications be made people did it anyway. Any gyro can be made unsafe by changing its original design. The Bensons the KB2 and the Walace machins that flew with the Mac had much success. I wonder how many of those deaths were cased by trying to fly the machine with little or no training?


Supreme Allied Gyro CFI
cloudhopper;n1140236 said:
I believe that most if not all were modified changing the design.
Now I have to wonder where you're getting that data.

cloudhopper;n1140236 said:
The Bensons the KB2 and the Walace machins that flew with the Mac had much success.
The first half dozen fatality reports I checked (the most recent) all show Mac engines. The older ones don't specify because the report formats are more cursory. I don't doubt that as Doug suggests, offset redrives made things worse, but that does not account for the whole list.

cloudhopper;n1140236 said:
.I wonder how many of those deaths were cased by trying to fly the machine with little or no training?
Since it was mass-marketed to the public as something you could teach yourself to fly, that's to be expected, and in my own humble opinion, Dr. Bensen bears some moral culpability for the casualty rate. His self-train syllabus may have worked well enough for the very, very conscientious, but there was no screening for that trait in the marketing/sales.

Doug Riley

Platinum Member
Cloudhopper, I lived through the Bensen era as a young teenage gyro-builder. I met the man and heard him speak at Oshkosh in 1972.

Most of the gyros that smoked in back then were Bensen designs with trivial modifications. Bensen always seized on supposed changes by the builder to excuse crashes. Many of these changes were immaterial. He was a clever designer, and apparently could be quite affable, but, as Wasp says, he had a moral blind spot when it came to improving the beginner-friendliness of his craft.

It would have been dirt-simple to change the B-8M to add a larger H-stab (possibly one incorporating roll-torque compensation as Cierva did), and maybe a slower rotor to increase rotor damping. Instead, Bensen adamantly refused, telling half-truths about the function of H-stabs, the nature of porpoising and zero- and negative-G -- things he almost certainly knew all about. (Note that thrustline placement was not the only issue, and possibly not even the most important one at the time.)

Self-teaching was possible (I did it at 16 -- a reckless age, but even so I didn't smash anything and am still here). As a substitute for patience, I had poverty. I couldn't afford an engine immediately and spent my time gyro-gliding. Then I had a 1500 cc VW that wouldn't get the gyro more than a few feet off the ground. I probably logged a hundred hours of near-ground putzing-around before flying my first, terrifying pattern.

Dual training in a well-designed trainer with well-informed instructor would have been a lot simpler and safer.