NTSB Identification: WH34ATEV3R
14 CFR Part 91: General Aviation
Accident occurred Sunday, September 27, 2015 in Magnuson Park, Seattle, WA
Aircraft: Unknown make constructed of expanded polystyrene
On September 27, 2015 at 1501 PDT, an experimentally modified aircraft suffered catastrophic structural failure, losing its left wing and the underside of its tail, impacting terrain at Magnuson Park, Seattle. The aircraft, composed of expanded polystyrene ("Styrofoam") was purchased at the Dollar Tree, located at 7816 Aurora Ave N, Seattle, WA 98103 on August 20, 2015 for $1.10 including tax. The aircraft manufacturer and model are unknown as the original packaging was immediately disposed of and the Dollar Tree no longer had any similar aircraft in stock. It is considered highly probable that the country of origin of the aircraft was China, due the large number of other novelty items sold at the Dollar Tree that have a Chinese origin.
For the aircraft's fatal flight, the launcher was angled at approximately 45 degrees from vertical and pressurized via a bicycle pump to approximately 70 PSI. After a countdown by the Flight Control Operator (FCO), inexplicably in Spanish, the aircraft was launched with a press of the launcher's electronic trigger.
|2. The FCO was in a good mood. The author remembers that he too was in a good mood in 1995 at the start of his trip to England with his soon-to-be ex-girlfriend Amy.|
Almost immediately after launch (T0), the aircraft suffered an in-flight breakup and impacted terrain approximately 15 feet from the launcher in three separate pieces: 1) The left wing. 2) A portion of the underside of the tail. 3) The rest of the aircraft.
The aircraft was put in a shopping bag and recovered to a secure location for further examination.
Fortuitously, the launch resulting in aircraft failure was recorded on video:
Analysis of the video has allowed an understanding of the cause of incident with the following observations:
- The time elapsed from launch (T0) to impact was 2 seconds.
- In the first frame after launch (1/30th of second since T0), the aircraft can be seen inverted with its wings deflected towards the ground at an angle of approximately 35°, with the damaged tail piece already separated from the fuselage:
- In the second frame after launch (2/30th of a second since T0), the left wing can be seen broken off the fuselage:
- In the third frame after launch, the aircraft has flown out of frame, with the exception of the tail piece. One half a second later, the tail piece impacts, and one and half seconds later the left wing and the rest of the aircraft impact almost simultaneously.
- The speed of the aircraft at launch can be calculated by the ratio of the FCO's actual height (HA = 144 cm), the height of the FCO on the video monitor displaying the video (HV = 20cm), the distance on the monitor the aircraft traveled after launch (D = 6cm), the number of frames per second (F = 30), and the angle of the launching tube (θ = 45°):
Plugging in the above values into the equation results in:
(The author did attempt to find ways to quantify his heartbreak in 1995 by using this equation and finding appropriate measures that could be substituted for the variables. He did not succeed.)
The Not the Transportation Safety Board determines that the probable cause of this accident was a combination of a poorly thought out experimental modification to the aircraft and an excess of air pressure in the rocket launcher.
The launch velocity of 41 mph surmounted the maximum load the aircraft's wings could handle. The deflection of the wings during launch exceeded the tensile strength of the expanded polystyrene until the left wing fractured.
In fact, previous launch attempts at 25 psi (instead of the devastating 70 psi) were successful without damage to the aircraft, but as the aircraft only reached a height and distance of approximately 10 feet from the launcher, 25 psi was deemed "boring" and a decision was made to pressurize the rocket launcher "to the max."
Provided for further reference is the full 11 second long video of the flight accident, including the audio of the countdown in Spanish and the laughter of the camera operator: