WASHINGTON — Boeing said Nov. 7 that a misplaced pin prevented a parachute from deploying during a pad abort test of its CST-100 Starliner vehicle three days earlier, the only flaw in a key test of that commercial crew vehicle.

In a call with reporters, John Mulholland, vice president and program manager for commercial crew at Boeing, said an investigation after the Nov. 4 test at White Sands Missile Range in New Mexico led the company to conclude that a “lack of secure connection” between a pilot parachute and the main parachute prevented that main parachute, one of three, from deploying.

The pilot parachute is designed to deploy first, and pull out the main parachute. However, Mulholland said that hardware inspections and photographs taken during “closeout” of the vehicle prior to the test showed that a pin that links the pilot and main parachutes was not inserted properly.

“It’s very difficult, when you’re connecting that, to verify visually that it’s secured properly,” he said, in part because that portion of the parachute system is enclosed in a “protective sheath” intended to limit abrasion but which also makes it difficult to visually confirm the pin is in place. “In this particular case that pin wasn’t through the loop, but it wasn’t discovered in initial visual inspections because of that protective sheath.”

Mulholland said Boeing is modifying assembly procedures through what he called “fairly easy steps,” such as pull tests, to ensure those pins are properly installed. Technicians have already confirmed that the same parachute linkages are properly installed on the three parachutes on the Starliner that will launch in December on an orbital flight test to the International Space Station.

“As normal, when we identify a sensitivity in one area, we expand it out to other areas that could have the same potential issue,” he added, for a total of 18 linkages throughout the parachute system. All but three have been checked and confirmed as of the briefing, he said.

NASA’s commercial crew program manager said the incident didn’t raise any specific quality control issues with Boeing. “This is just another place where we’ll be working with Boeing going forward and put together joint action plans for us to address any concerns,” said Kathy Lueders. “It’s part of our normal process to work through this.”

The test, Mulholland said, also provided an unplanned, but successful, verification of the ability of Starliner to safely land under two parachutes, something that had been tested during earlier qualification of the parachute system. “It’s a demonstration and understanding of the robustness of our design,” he said.

The parachute issue was the only problem found with the pad abort test so far. Initial analysis of the data from the brief test showed that key elements of the system, including the abort motors and separation of the service module and heat shield, were as expected.

“The spacecraft performance and test team performance was outstanding,” he said. “The vehicle trajectory it flew was right on top of pre-test predictions.”

Mulholland said technicians planned to continue analysis of the test using data from flight recorders on the spacecraft recovered after the test, as well as an anthropomorphic test dummy inside the capsule. “We’ll spend a week and a half and pour through” that data, he said. “Nothing abnormal is expected based on the data review of the downlinked data we’ve seen so far.”

Nothing in that review, they said, suggested cause for delaying the Orbital Flight Test of Starliner, scheduled for launch no earlier than Dec. 17 from Cape Canaveral. United Launch Alliance started the stacking process earlier in the week for the Atlas 5 that will launch that spacecraft on an uncrewed test flight to the ISS.