A good question!
A good question!
I guess airworthiness here is a relative term clearly depending on who is flying it and their abilities. Is there any downside to adding a stabilizer, or is it just a matter of being a purist about the original design?
I like the way you think about things Jeffrey.
In my opinion the downsides to adding a horizontal stabilizer are weight and the structure to handle the weight.
I feel mounting the horizontal stabilizer further back allows it to be smaller (lighter) to get the same benefits but complicates the structural challenge.
On a pusher gyroplane there is a propeller in the way off a structure with depth so the area under the propeller becomes the structural weak point. Going to an upper support complicates (heavier) and if it is part of the mast can quarrel with the normal movement of the rotor head.
The structure on Ed’s aircraft could probably support a horizontal stabilizer with a reasonable moment arm. Finding out could prove problematic. I find it difficult to calculate the loads on that tube and the fatigue life of aluminum. It is interesting to note that Ed has the vertical stabilizer and rudder on a unusually long arm and has it braced side to side.
Every gyroplane shakes and it is possible with a long enough stick to lower the resonate frequency of the empennage into the normal frequency range of that particular gyroplane leading to fatigue challenges.
I am a horizontal stabilizer enthusiast for many reasons and the gyroplane I fly (The Predator) has an unusually large horizontal stabilizer mounted well back of the center of gravity.
The Predator has the horizontal stabilizer below the propeller slipstream and that is where I prefer it.
The Predator is very nearly center line thrust so she is not compensating for a large thrust line offset with her generous tail.
I have less than three hours in gyroplanes without a horizontal stabilizer (three different RAFs) so I am not experienced enough to have a strong opinion. One RAF had a Stabilator and it made a difference but all of them seemed to be relatively pitch unstable particular in gusting winds. I suspect all three had a much higher thrust line/center of gravity offset than Ed’s aircraft.
Thank you, Vance