The Saga of the Sperry Special
Neither the Ellensburg librarian nor Dad could deter the nascent aeronaut.
Note that the original author of this article was Prater Hogue, as told to Dean Reynolds who added the hand drawings. Dean’s son (and New RCSD contributor) Waid Reynolds submitted it for all of us to enjoy. And don’t miss the ‘punchline’ at the end. — Ed.
The probable cause of the accident, in the cold and efficient language of a modern accident investigation report, would undoubtedly be: Inadequate engineering design with contributing factors of improper manufacturing processes, pilot error, and pilot inexperience in type.
Such an assessment, however, would neglect a fundamental human factor — the attitude of the Ellensburg Washington Librarian. She seemed to be in a particularly crotchety mood that summer, and she continually chased me out of the library before I could copy the drawings and specifications from that old issue of Popular Mechanics just right.
Time and wisdom have brought forgiveness, because I can now appreciate that she was only trying to protect me from myself. After all, in that long-ago time, a boy studying hang glider construction must have seemed, to her, the equivalent of a modern teenager researching the horticulture of marijuana — and her misgivings very nearly proved to be well founded.
Notwithstanding her resistance to aeronautical progress, my program moved out on several fronts. Financing is the bane of most high-technology projects, and mine was no exception. Two dollars for pine lumber was not easy to come by in that day, and neither was the price of a couple of cedar strips at 30 cents each. The bill of materials also contained a roll of wire, at 69 cents, two dozen flour sacks at 4 cents each, two turnbuckles (“borrowed” from a damaged airplane), and 40 cents’ worth of laundry starch. Starch?… yes, starch; but more about that later.
Vigorous cost control and lots of scrounging kept program costs under $5.00 (not counting my new slacks). No production line was planned, so I used what is known in the business as “soft tooling” — two saw horses and some old two-by-fours.
In Ellensburg the summer days are long and hot, but I didn’t notice the heat as I was busily sawing, bending, tying, and gluing.
My Dad helped, but if he knew that he was ripping out wing spars on his circular saw, he didn’t let on. Building a glider keeps a boy out of the pool hall; but, if my parents had been gifted with precognition, they probably would have put a cue in my hand and sent me off to town.
At length, the final wire was rigged, and the last of the flour sacks had been stretched over wing and tail. It was time to begin starching…yes, starching. Its purpose was to fill the pores in the flour sack fabric in order to prevent air from leaking through and spoiling the lift of the wings.
Coat after coat was applied, until the wings and tail surfaces began to take on a sheen that rivalled the famous twenty-coat, hand-rubbed gloss of a Staggerwing Beech, albeit with no pretense of the water resistance of the Beach. Fortunately, Ellensburg flies in a high, dry, and windy mountain basin, and all-weather flight was not an operational requirement.
When at last the final coat of starch was complete, she was a gleaming beauty of a stick and wire biplane emblazoned here and there with a colorful trademark proudly proclaiming “SPERRY SPECIAL” to the waiting world.
For those who never saw a hang glider, the cockpit consisted of a pair of fore and aft parallel bars on which the pilot clung like an acrobat; and, with an economy of design seldom seen in this day of specialization, the landing gear (the pilot’s feet) was combined with the flight control system. Airborne, the feet were to be thrown this way and that in order to effect a degree of control.
The propulsion system was a two-stage affair which also relied on the pilot’s undercarriage to build up a store of potential energy by climbing a hill, after which the glider would be boosted to takeoff velocity.
Finally, under the inexorable pull of gravity the machine and its pilot would float gently to the earth (so it said in the magazine). The whole concept was elegantly simple — no moving parts, no electronic control system, no instruments, no engine, no fuel system — so elementary that nothing could go wrong.
Like all good aircraft manufacturers, I conceived a multi-phase program of tests designed to prove the inherent safety and airworthiness of my machine. Phase One would consist of ‘taxi’ test during which I would run into the wind to sense the forces acting on the wings and tail.
Phase Two would progress to very short flights in which I would launch myself from the tops of small knolls and learn the feel of flying and how to control the glider.
Phase Three would progress to longer and longer missions until at last, I would launch myself from the top of a formidable ridge called Craig’s Hill for the ultimate in long-range missions. I was confident that this logical progression would lead to success. After all, it was a path well trodden by illustrious pioneers like Otto Lilienthal, Octave Chanute, and brothers Wright.
Phase One and Two proceeded rapidly, and I was soon hopping from one knoll to another logging flight time in intervals of seconds. Only minor modification and repairs were needed, and I gained confidence as the glider seemed willing to carry my weight and docile enough to control.
No good test program would be complete without a problem and mine was that I could not seem to find an intermediate-sized hill in the neighborhood. The leap from Craig’s Hill seemed mighty long and lonely. Torn between the desire to fly and the fear of it, I searched my soul for awhile.
The test program had been going without a hint of trouble, and I had accumulated some thirty-six seconds of pilot-in-command time in some thirty-odd flights. Why not? I asked myself, and there was no answer. Terms like phugoid oscillation, tail moment arm, and stabilizer trim angle had not entered my vocabulary. I didn’t know that they, the librarian, and the author of the magazine article had set an unseen trap for me.
Anyone who can slip away from home and avoid curious acquaintances while wearing a hang glider should give lessons to the CIA, but somehow I succeeded. In due time I found myself engaged in pre-flight activities on the lofty top of Craig’s Hill. These consisted of catching my breath after the climb, and mustering my courage.
I didn’t dare to look over the edge; but if I had, I would have seen that the familiar Ellensburg wind was sweeping up the hill, making a strong updraft that could not be perceived from my sheltered position.
At last, the decision was made, and the glider stiffened in the breeze created by my running feet as I hurled myself toward the lip of the hill. All too soon came the scalp-prickling realization that my feet we no longer touching the ground, and that I was looking down on the world from an awesome height.
Moreover, the front of the glider was pointed skyward at an angle that even I, in all my innocence, knew was too steep. The sough of the wind in the struts and wires whispered down the scale as the front of the glider tilted ever farther toward the zenith. There was a timeless moment of hanging suspended between brown earth and blue sky; then came the stomach-wrenching, falling-elevator sensation as the stall break came.
We fell, seemingly forever, as the glider nosed earthward and began to dive. The wind notes climbed the scale, and the earth rushed upward at a terrifying speed. Half paralyzed with fright, I tried to work my way tailward to correct that hair-raising dive; and at long last, the front of the glider began to rotate upward as I clung desperately to my parallel bars while the roaring wind and the g-forces tried to dislodge my white-knuckled hands.
The glider soon reached level attitude, but my relief was short-lived. The nose-up rotation continued; and, in spite of my best effort, the whole terrifying sequence was repeated — stall, fall, dive, upward swoop.
Like a repetitive nightmare, it began a third time, but there was a profound difference. As the glider nosed down and began to pick up speed, its flight path abruptly intersected the solid earth. There was a pride-shattering impact, a small mushroom cloud of dust and starch erupted skyward, and I was lying in a pile of instant splinters.
I lay there a moment while the dust cleared, half expecting a transparent replica of me to soar skyward like a scene from an old movie. When it didn’t happen, I slowly arose and untangled myself from the wreckage of splintered wood, torn cloth, and clinging wire. Stepping clear at last, I brushed off the dust as best I could, and then trudged homeward across that hot and dusty field with never a backward glance.
My father was working in the front yard as I limped home, trying not to call attention to the holes in the knees of new slacks and the sleeve that was nearly separated from my jacket. He demonstrated great sympathy and understanding by resisting the temptation to engage in a game of 20 questions which would have sandpapered my already-bruised nerve ends, and further diminished by battered ego.
Early next morning I initiated an official investigation into the cause of this accident. From the wreckage it was determined that the fuselage was approximately 27 inches longer than the designer intended. Further investigation revealed that this error stemmed from the fact that the magazine containing the glider plans was bound into a larger volume which could not be opened fully. The crucial dimension was hidden, and an engineering estimate was substituted.
This error, in itself, might not have been too serious; but it was also discovered that the horizontal stabilizer had been fastened to the fuselage at the wrong angle causing the glider to be trimmed nose-high in flight.
Hang gliding is being rediscovered now, and youths are flinging themselves off hills all over the country even as I did, and some are not so lucky. I would like to pass along some advice from some old pioneers. Call it a message from Otto, Octave, Orville, and Wilbur. Proceed slowly fellows. Find that intermediate hill!
As described in the interview linked below, Prater Hogue eventually went on to become head of Boeing’s Accident Investigation team. — Ed.
Resources
- Prater Hogue Interview — A transcript of an extensive interview conducted by Central Washington University as part of their CWU Retirement Association Interviews presumably to capture the life stories of CWU alumni.
Transcript from the original text by RCSD Editorial Assistant Michelle Klement. Read the next article in this issue, return to the previous article in this issue or go to the table of contents. A PDF version of this article, or the entire issue, is available upon request.
