Parachute Lesson Learned
by Tom Myers, IAC 16830
It was all my fault. I did not realize it at first. Fortunately, I realized it at last. Here is the story.
I was getting my plane ready to fly one recent morning. I opened the canopy, and there to greet me was my deployed parachute. My first thought was, “How on earth could a parachute deploy itself overnight?” The answer was the Law of Unintended Consequence, aka Murphy’s Law, which states that what you do not pay attention to comes back to bite you in the tail. In this particular case, it was a few things I was not paying attention to. I promise you I’m sure paying attention to them now.
When I first bought my plane six years ago, it came with a foam pad in between the seat back and the parachute. The pad was showing some signs of use, and not knowing how long it had been in service, I just replaced it. I went to a local sporting goods store, bought a 7/16” thick yoga mat, trimmed it to fit the seat back, velcroed it in place, and never really thought about it much afterwards. Mistake number one.
Over the ensuing years, the high points on the back of the parachute compressed and wore down the mat to the point where there was no longer any cushioning between the parachute high points and the rigid carbon fiber seat back. Because I was not inspecting the mat, I did not notice this happening.
The high points on the back of the parachute are created by the ripcord pins and closing loop, which are located underneath the inspection flap. The ripcord pins are attached to the D-ring by stainless steel cable. The closing loop holds the parachute in its packed state. The closing loop runs between the two ripcord pins. The closing loop is made from high strength nylon cord. Pull the ripcord pins with the D-ring, and the closing loop no longer holds the parachute in its packed state. The big spring around which the pilot chute is constructed is now allowed to decompress. Rapidly. When that happens in your plane overnight, you end up with a cockpit full of deployed pilot chute, and a face full of chagrin in the morning.
(Photo Left - Closing Loop Failure.)
The seat back pad had reached a critical point of thinness at the top ripcord pin. That allowed the closing loop to directly bear high compression forces from the rigid seat back right where it passed over the tight radius of the top ripcord pin. Since I was routinely pulling and pushing very hard during virtually every flight, both the chute and I would regularly shift up and down directly against the seat back. Since the last repack of the parachute, the top closing pin had been wearing its way through the closing loop until the closing loop gave out.
Had I been regularly opening up the inspection flap and checking on the condition of the ripcord pins and closing loop, I likely would have noticed fraying of the closing loop where it passed over the top ripcord pin before it gave out. Unfortunately, my attitude had been that the inspection cover was tantamount to the lid of Pandora’s Box, so I avoided courting trouble by not messing around underneath it. Sort of like being the pin inspector in a hand grenade factory being concerned with the outcome of actually finding a bad pin. Mistake number two. All I was really doing was changing the nature of the trouble that I was courting. Sooner or later, as is always the case with the Law of Unintended Consequence, I was destined to have the trouble that I ended up with.
The two questions foremost on my mind were, “What caused this to happen,” and, “How do I prevent this from ever happening again?”
I am indebted to parachute rigger Robert Marshall for his assistance in answering both questions. First I emailed photos of the deployed chute to Robert. Then I shipped the chute to Robert for repacking. As soon as Robert saw the photo of the failed closing loop, we spoke by phone, and he put forth a theory about compression wear on the closing loop by the ripcord pin. While Robert was still on the phone, I discovered and described the wear to the seat back pad (Photo to the left shows the wear to the seat back pad.), fessed up to not opening up the inspection flap, and the likely sequence of events causing the problem, both physical and behavioral, became clear.
Many changes were implemented to prevent a reoccurrence of this problem. I open the inspection flap regularly. I look at the condition of the seat back pads regularly.
Instead of just replacing the seat back pad with a new one, I decided to prevent any compressive forces from being applied to the inspection flap in the future. I fabricated a two layer seat back pad assembly. I took the old seat back pad, and cut out the rectangular wear pattern area caused by the inspection flap. This became the top layer pad that rests against the parachute. I made a new bottom layer pad that rests against and covers the entire seat back. I velcroed the layers together and to the seat back. The new two layer pad arrangement creates a cavity for the inspection flap. After multiple practice flights, there is still no evidence of any contact between the inspection flap and the lower pad. (photo to the right is the new two layer seat back pads with chute.)
The closing loop of an emergency parachute is normally fabricated from 500 pound strength nylon cord. After Robert discussed the situation with the parachute factory, the decision was made to fabricate the new closing loop from 1000 pound strength Spectra cord normally used on sport parachutes (Pictured left). After multiple practice flights, there is still no evidence of any wear to the new closing loop.
So far, so good. I will report back in the future on how well the changes have worked out.
Fly safe.
