Three-sixty degree appraisal
This is a sub-page of Hang gliding 1976 part 1. It documents my own hang glider design efforts during that period. It follows from Simple versus complex, which includes my first experimental hang glider.
Established hang glider manufacturers were not the only ones who encountered problems…
This design suffered from an unfortunate pitch characteristic that aerodynamicists term phugoid motion. The camber curve of the sail changed shape as the angle of attack changed, which amplified my pitch control inputs—after a brief delay. On one test flight, that positive feedback mechanism* sent me into a series of pitch oscillations. Fortunately, it happened to be leveling out from a dive when I touched down in the dusty bottom field at Monk’s Down and I got away with a sprained ankle.
* Positive feedback mechanism?
“You engineering types are so confusing. Positive feedback is good! We want more positive feedback! It tells use we are doing things right! And why don’t you smile?”
In engineering terms, as distinct from corporate HR arts graduate terms, positive feedback is a runaway response that causes instability; an out-of-control situation. Negative feedback is where the mechanism tends to damp out excursions from the required control setting. The Watt governor of the first successful steam engines is an example I learned in CSE engineering at secondary school.
“The what governor?”
Oh, never mind…
I contracted out the construction of my sails to a local hang glider sailmaker (who, at age 17, had built his own Skyhook IIIA from plans) but I built the airframes myself. My hang gliders all flew — eventually. However, I was always at least two steps behind the state of the art.
Notice the absence of an emergency parachute at this time.
On a later version of this glider, I created the deflexor cables as a single wire running through a pulley (or equivalent device) at the nose so that the tension on each side would always be the same. It just seemed like a good idea at the time. On a flight test, the glider seemed to fly normally and I was about to land it, avoiding wet ground, when the horizon whipped round and, still in the prone position, I was dumped onto the ground — actually into a couple of inches of water — with the glider and me facing the opposite direction of my approach.
Some time later, when I was away from home, my mother took a call from Steve Hunt of Hiway Hang Gliders (then based in Brighton on the Sussex coast) who heard about the incident. When I next saw Steve, a year or so later, I had forgotten all about it. I will never know what insights he might have provided.
I took this photo of Winklebury hill from the car park at Berwick St John village fête in June, 2013. The aspect reminds me of a trivial event in early 1976, when this was our only north-west site. (Bell Hill had not yet been discovered.) I was at the farm at the bottom, watching one of two flying brothers on approach to the landing field (nearer the hill than where this photo was taken). Flying seated in a Waspair Falcon IV, framed by the hill and some low trees (out of view in the photo) he went right round in a 360-degree turn with little loss in height. He then levelled out and landed normally. That was the first 360-degree turn in a hang glider I had seen.
Doesn’t sound like much, but it was most impressive for those times. However, the pace of advancement was so rapid that, by the end of that summer, 360 degree turns were considered almost routine.
In 1976 I was a hang gliding instructor, first teaching beginners informally at my local site, then working for a hang gliding school in south Wales. One day teaching beginners on a low slope, we found that those who flew one particular glider (the sole example of the type that we used) kept nosing in hard shortly after launching. We determined the correlation with the incidents and the specific glider only gradually. Why did Fred Bloggs nose in just now when he was OK two minutes ago. And why has Joe Soap just nosed in? Eventually one young fellow, a student at the nearby Polytechnic of Wales, was winded so badly in a hard impact he was unable to breathe. He just lay on the ground curled in a ball for a minute. I thought we were witnessing a fatality. However, in a few minutes he was up and about and able to describe his experience. My relief was short lived.
“Everard, take that glider up and find out what’s wrong with it.” Mike, the chief instructor, was a former RAF pilot, glider pilot, and scuba diver.
I launched with plenty of speed (for safety) and was settling into the short period of level flight afforded by the low grass-covered slope when the glider slowly, but unstoppably, pitched nose-down and gathered speed, in much the same way as in stall recovery, but I was nowhere near the stall. I ‘pushed out’ on the control bar for maximum rearward weight shift (equivalent to hauling back on the control stick in a conventional glider or airplane) and it levelled out and flew normally from then on until I landed (for a total flight time of no more than thirty seconds).
“That glider is grounded,” said Mike. No explanation from me was needed; everyone saw what I did and what the glider did.
I do not know why it behaved like that or why the fault had not been discovered earlier, or whether the problem was inherent or the result of incorrect adjustment. (The type had been in use for about a year by then.)
We kept the gliders in a disused cinema at the back of rambling premises in Merthyr Tydfil. ‘Rambling’ isn’t strong enough. It was like another dimension. Looking out one window onto a vertical hole between structures, there was a river flowing underneath… Late in the year, we instructors were all issued with identical red and white winter jackets and I recall us striding up the Merthyr main street, about 10 feet tall. I half expected to bump into a local girl whose song Lost in France was climbing the pop charts. In retrospect, the people in that street likely thought were were a bunch of English fools and I never did get to meet Bonnie Tyler. (One pop star I did meet through hang gliding is Elkie Brooks, but that was in the early 1990s.)
Mike had immigrated from Russia with his mother — who barely spoke English and lived in rooms in the back of the sprawling building (which included a disused cinema/movie theater). Fronting onto the High Street, was a junk shop.
Mike sometimes had friends round and I overheard them discussing how much money they had made the day before. Then, barely pausing, switching to the subject of hang gliding, one of them described how turbulence had rolled him (in a Birdman Firebird) upside-down a few days earlier. (This was before we adapted emergency parachutes for hang gliding.) He was lucky to be alive. These were kick-ass people with a kinda strange background. Mike had flown for the RAF in his younger days.
The Fight to Preserve South Wales’ Jewish History in the Jerusalem Post