On September 17, 1908, at 5:14 PM, local time, Orville Wright was conducting a demonstration for the United States War Department; he flew with United States Army First Lieutenant Thomas E. Selfridge. Wright was conducting a proving run for the military in a modified version of the Wright Flyer, the upgraded Model A. About twenty minutes into the demonstration, after three successful laps over the Parade Grounds outside Arlington Cemetery, Wright heard a light tapping. Being wary, he began to shut down the engine and attempted to glide from a height of 150 feet. Before the engine could be shut off, per Orville’s testimony, he heard, “… two big thumps, which gave the machine a terrible shaking.” A piece departed the aircraft before the airplane swerved to the right; the aircraft would not respond to his inputs. He shut off the engine, while working to regain control.
Per the accident report, Wright said, “I continued to push the levers, when the machine suddenly turned to the left. I reversed the levers to stop the turning and to bring the wings level. Quick as a flash, the machine turned down in front and started straight for the ground.” Witnesses said that at seventy-five feet, the machine began its nose-dive into the ground.
Lieutenant (Lt.) Selfridge had the sad distinction of being the first person to die in a heavier-than-air powered aircraft, a unique fatality for, at the time, only balloon and dirigible occupants were known for being aircraft fatalities. Even so, Lt. Selfridge’s unfortunate death had nothing the do with the accident; he neither affected airworthiness nor unexpectedly contributed to the accident. Aside from mentioning his unfortunate demise, Lt. Selfridge did not have a place in the investigation. However, Lt. Frank Lahm played an important role.
At the time of the Wright Brothers first flight and subsequent work with the military, the term, ‘Powered Aircraft’ was locked up by dirigibles, balloons and other lighter-than-air machines. Per Britannica.com, Gliders – one of the first heavier-than-air attempts – were receiving initial attention when Otto Lilienthal, with his brother Gustav, of Germany, “… built his first [heavier-than-air] man-carrying craft, with which he could take off by running downhill in the wind.” The Lilienthal brothers had experimented with wing camber and Bernoulli’s Principle; they studied stabilizing tail surfaces that would evolve into horizontal and vertical stabilizers, rudders and elevators. It was not until 1903 that power and aircraft were successfully married in the Wright Flyer.
Documented information on the accident was extremely limited; the unexpected disaster was witnessed by military personnel and some media; no one expected to see anything beyond the trial runs of some of the latest aircraft. The consequences of heavier-than-air flight were unknown, perhaps as alien to the people observing as those fearing a ship going over the horizon’s edge a millennium ago. It was clear from Wright’s comments that the accident was a surprise, that the modified mounted propeller upset the flight as it had; the result was completely unanticipated.
Per the airspacemag.com website, First Lt. Frank Lahm, after freeing Orville Wright and Lt. Selfridge from the accident aircraft, immediately began investigating the wreck. He would submit his report to the War Department five months later. Lahm had flown with Orville Wright a few days earlier and was familiar with the Model A; he had witnessed the accident and helped rescue the occupants. Lt. Lahm had access to all witnesses and the wreckage was available to analyze.
Before his demonstration for the War Department, Orville Wright had replaced the original 104-inch propellers on the Flyer with 108-inch propellers to increase aircraft speed. During the demonstration, the aircraft had reached a top speed of forty miles-per-hour and an altitude of 100 to 150 feet above ground.
When Wright heard the tapping sound, he was confused; his subsequent actions were not fast enough to prevent tragedy. The aircraft nosed over and lost 125 feet of altitude before Wright recovered, but he did not have enough room in the final 25 feet to pull adequately out of the dive; the skids – landing gear – dug into the earth and the aircraft crashed with what one reporter described as “frightful force”. Wright later commented, “A few feet more [of altitude], and we would have landed safely.”
During interviews, several witnesses had confirmed what Lahm had seen: a piece of one of the Flyer’s propeller blades had separated from the end of the propeller, causing a propeller imbalance. Lahm’s report stated, “… excessive vibration, this guy wire [securing the front rudder] and the right-hand propeller to come into contact. The clicking which Mr. Wright referred to being due to the propeller blade striking the wire lightly several times, when, the vibrations increasing, it struck it hard enough to pull it out of its socket and at the same time to break the propeller.” The term ‘guy wire’ may have been used in error; a guy wire is used to stabilize, brace or stiffen. The rudder was a moving flight control. However, the function of the wire was irrelevant, as was the title assigned to it; that it was in a position to be struck by the propeller was critical. It was not clear if Wright’s control movements moved the rudder wire into the propeller’s path or whether the amount of wire tension allowed it to swing into the propeller.
Was this accident preventable? Not likely; there were no previously similar situations for Wright to have learned from. The Model A did not have gauges to monitor the propeller or the rudder movements; all sensing of flight controls and engine monitoring were rudimentary, limited to sight, sound and feel. Even if Wright had identified the problem with the propeller, it would have been unlikely he could have shut the engine down in time to prevent the accident.
In today’s aviation, what would have been the norm for Wright’s propeller modification. First, as the Model A was a redesign … of an aircraft without a type certification, the Model A would have been classified as an ‘Experimental’ category; it would have been operated under a special airworthiness certificate (SAC) and it would have been subject to the limitations according to its category. Per the Federal Aviation Administration (FAA) website, experimental category aircraft SACs are issued today to aircraft used in Research and Development – for which the Wright Flyer Model A qualified. Other limitations of Experimental aircraft include: Showing compliance with regulations; Crew training; Exhibition; Air racing and Market surveys.
The 108-inch propeller Wright changed to would have required testing as a either a modification or a complete redesign. The change in manufacturer design would have required checking to assure a clear path for the blades – no airframe in the blades’ paths. The blade materials would be tested for structural integrity. The propeller would be rated for safe operation with the Model A’s engine and that there was engineering paperwork to assure the propeller was a safe addition to the powerplant. Assuming the propeller was constructed of wood, the blade angles, symmetrical uniformity, the bonding of propeller to hub, balance and effects of air on the propeller’s structure would have had to be engineered as well.
Even in 1908, there were lessons to learn – and some to unlearn – from early heavier-than-air powered-aircraft of the day. Even politics played a part in the demonstration of the Model A; Wright had reason to believe that Selfridge was friends with and would show favoritism towards, Doctor Alexander Graham Bell, an aircraft builder and rival for the War Department’s aircraft contract. However, on that fateful flight, there was nothing dubious about Orville Wright’s intentions, which was to make an aircraft to the War Department’s specifications.
Perhaps the only lesson to be learned that day was to maintain aviation safety, no matter what; to think outside the box and to anticipate … anything. A lesson not to be unlearned over a century later.