NTSB report of In-Flight Breakup During Test Flight in Magnuson Park, Seattle, WA

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

 Injuries: None.

Executive Summary

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.

1. The aircraft after breakup on September 27, 2015. Note the cricket game in progress in the background. The author of this report first witnessed a game of cricket in 1995 while on vacation in England with his soon-to-be ex-girlfriend Amy. While watching the cricket game, the author was somewhat confused as he could not quite figure out its rules.

The aircraft was originally designed to be launched by grasping it firmly with a hand, pulling back the arm of the hand grasping it, and forcefully flinging it forward while timing the release of the grasp at the moment of the arm's highest velocity. However, for a reason described as "awesomeness", the aircraft had been modified by attaching to its underside a tube, approximately 0.75 inches in diameter and 10 inches long, open at the aft end and pinched closed at the forward end. The tube, constructed of plain white paper and duct tape was secured to the aircraft with masking tape. The purpose of the tube was to allow the launch of the aircraft by the release of pressurized air from a rocket launcher constructed out of polyvinyl chloride (PVC) pipe.

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.

3. Aftermath of in-flight break-up. When the author of this report was in 7th grade, after math class he had history. But the attempted humor in the previous sentence does not mitigate the author's experience of an in-flight breakup of another type when returning from his vacation in England in 1995. When the flight took off from London, he was sitting next to his girlfriend Amy. Ten hours later, when the flight landed in Seattle, he was sitting next to his ex-girlfriend Amy.

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:

  

  4. The inverted aircraft's wings deflected downward (or is upward the correct term because the wings are deflecting over the top of the aircraft? When should relative directions be used and when should absolute directions be used? The author has no idea) and the broken tail piece (on the left). Reflecting back to his 1995 trip with his ex-girlfriend Amy in England, the author can see incidents that led to the subsequent breakup. If Amy is reading this, the author wants to let her know that, yes, in cricket, the bowler (not the pitcher) really is attempting to knock down the wicket.

• In the second frame after launch (2/30th of a second since T0), the left wing can be seen broken off the fuselage:

  

  5. In-flight breakup as it happened, immediately after takeoff. The author of this report still wonders why in 1995 his ex-girlfriend Amy initiated their breakup immediately after takeoff and not after returning to Seattle, to avoid the miserable experience of being cooped up next to each other in an aluminum tube at 35,000 feet for an interminable ten hours. However, as the author is typing this, in retrospection, perhaps she didn't want to sit for an interminable ten hours next to the person she was planning on breaking up with and just wanted to get it over with. The author does believe the breakup was the right thing to happen and the author's life has turned out very well in the subsequent two decades.

• 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 (H_A = 144 cm), the height of the FCO on the video monitor displaying the video (H_V = 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.)

Findings

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: