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topic: Moyes RX 3.5 (1 article)

Krys' Drogue Incident 8-15-21

Thu, Oct 7 2021, 10:43:50 pm MDT

New and untested chute

bridle|drogue|Greg Dinauer|Krzysztof "Krys/Kris" Grzyb|Larry Bunner|Moyes RX 3.5|triangle

Larry Bunner reports:

On 8-15-21 Krys Grzyb and Greg Dinauer set an 83km triangle task from Twin Oaks airport in Whitewater, WI east to East Troy, northwest to McDermott airport and then southwest back to Twin Oaks. Greg aborted the task early and flew back to the airport. Krys was doing well getting over 5200’agl on nine climbs. He tagged the first two turn-points and was headed back to the airport.

To this point he had been in the air for 2hr 15min of which over 1½ hours was above 4200’. The winds were 5-9mph from the southeast. Sustained climbs over 1000’ were averaging about 350fpm with one climb averaging 770fpm. He found a thermal just past the last turnpoint 18km out and climbed 300 feet to ~4400’. He needed about a 12:1 glide to get back with a crossing tail wind. He confidently left the last climb knowing he could make it and even if he hit increased sink, he would hit a thermal soon enough.

He went on a long glide sinking over 300fpm and was soon down below 1000’. He selected a narrow field of grass along a farm for his LZ. Approaching from the southeast at 500’ he unzipped the drogue pouch and began extracting it from the pocket. His intent was to deploy it near the ground but the drogue slipped away and accidentally deployed.

Immediately the glider turned right and his sink rate increased to 600+fpm. He pulled in on the control bar, the glider began to pitch down and the sink rate increased to over 900fpm (peak). Thinking the drogue malfunctioned, he reached back to grab the bridle but couldn’t find it. He instantly began to correct for the turning dive. With extreme effort the glider rounded out pointing downwind and just above the corn. The glider, slowed somewhat by the corn, whacked in hard but the glider and Kris were miraculously unharmed. Pretty shaken, he called to the airport to get a retrieve; Greg and Chico showed up quickly to help get the equipment out of the corn.

Krys has used a drogue chute for many years. This particular drogue was developed to train runners to improve their speed. It has one long bridle that runs back to the chute shroud lines. These lines are short relative to the length of the bridle. He used this type of chute for several years with the drogue deploying aft of the keel. This spring he purchased a new drogue from a different manufacturer and replaced his old worn one. He did not compare bridle lengths before installation. Up to this flight the new drogue had not been tested/deployed. After landing, Kris discovered that the keel had penetrated between the shroud lines and the drogue was affixed/centered around the keel.

The bridle length was a couple inches shorter than his previous drogue. When the drogue accidentally deployed, the position of the drogue effectively provided a lifting surface on the end of the keel. When the control bar was pulled in to increase sink rate, the forces on the aft end of the keel decreased the nose angle further thus progressively increasing the sink rate (to the point the nose was pointed at the ground). It took close to all of Krys’ strength to push the bar out far enough to overcome the resistance to level out the glider before entering the tall corn.

In the moment, he focused entirely on recovering the glider turn and descent and felt there wasn’t enough time or altitude to throw his main parachute. His Moyes RX 3.5 sprogs were at the factory settings. Corrective actions that Krys has taken or intends to take include: shorten bridle to prevent keel interaction, add an extra line to one of the shrouds and the harness loop to give access to the pilot to deflate the drogue, and adding a drogue release so the drogue can be cut loose from the pilot.

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