A combination of factors were likely responsible for the fatal Quicksilver chair accident on Whistler Mountain last year, a coroner’s judgement of inquiry has concluded.
"The underlying cause of the accident was systemic in nature," Coroner Peter Gordon wrote. "The problems, weaknesses, and causes noted in this report were all items that could have, and should have, been found and attended to before they culminated in the fatal accident on December 23, 1995. There was more than one occasion when an incident or maintenance problem should have alerted the various parties to undertake a more thorough examination of the lift. Such an examination did not take place. The system of checks and balances was inadequate to prevent this tragedy."
However, Whistler Mountain Ski Corp. President Doug Forseth noted that engineers, lift operations and maintenance personnel at other ski areas in North America that operated similar lifts had not discovered the problems and weaknesses Gordon outlines in his 18-page report.
Two people died and another was left paralyzed as a result of the accident last December in which four chairs fell from the Quicksilver haul rope. Gordon led an eight-month investigation into the accident and noted there were two previous accidents involving chairs detaching from the haul rope and falling to the ground in the area of tower 21. Both accidents occurred with empty chairs.
Gordon’s report notes the fatal accident was preceded by a lift host halting the lift for a misload at the top station. Witnesses stated the lift came to a sudden, violent stop. Trevor MacDonald, a 25-year-old Vancouver man, and two others were on chair #146, which was between towers 21 and 20 when the lift was stopped. That section, above Coach’s Corner on the Dave Murray Downhill, is the longest distance between two towers, is the highest point above ground (approximately 75 feet) and is the steepest angle on the haul rope (38 degrees).
"When the sudden stop occurred, the carrier Mr. MacDonald was riding swung backwards and forwards as the rope bounced up and down. The grip detached from the haul rope and slid down the rope until it collided with the carrier (chair) in front of it, carrier # 44. The force of the impact caused carrier #44 to detach from the haul rope and carrier #146 fell to the ground. Carrier #44 slid down the rope and collided with carrier #62, which also detached from haul rope. Mr. (James) Roche (who died several days later as a result of massive pulmonary thromboembolism) was riding on this carrier. Both carriers continued sliding down the haul rope and collided with carrier #110. This carrier also detached, and all three carriers slid down the haul rope until they collided with the lead-in sheave assembly on tower 20. All three carriers then fell to the ground."
Gordon’s investigation found a number of faults with the basic design of the high-speed detachable quad chair, manufactured by Lift Engineering and Manufacturing Inc. of Nevada, and its Yan 11 grip.
"Although some of the findings of these tests were not causative factors in this particular accident, they do demonstrate there was a lack of research and development on the part of the manufacturer, and a lack of adequate checks and balances on the part of the manufacturer, the ministry and WMSC," he wrote.
He also found fault with the lift’s installation, with some aspects of its certification and with maintenance. His report makes 24 recommendations.
Lift Engineering has since filed for Chapter 11 bankruptcy protection. Whistler Mountain is replacing the Quicksilver chair with a high-speed gondola manufactured by Poma of America.
Among the faults Gordon found with the lift:
o the Ministry of Municipal Affairs, Engineering and Inspection Branch, do not always receive all the plans, specifications and documents for new lifts far enough in advance of construction to complete a full review of all documents. Construction is usually allowed to proceed provided documents are forwarded later. These documents were not forwarded.
o the engineer who certified that the lift met all design and code requirements was an employee of the lift manufacturer. "Some portions of the lift did not meet the Z98 code or design specifications, and these difficulties were either not detected or not adequately acted upon by the manufacturer, the lift owner and/or the inspection authority."
o under the province’s Z98 code governing standards for all aerial tramways, a minimum longitudinal swing of 15 degrees between vertical position of the arm and the grip assembly/haul rope is required. None of the chairs on the Quicksilver complied.
o the requirement for 15 degrees of lateral swing clearance was not met.
o under the Z98 code grips are required to resist slipping to a minimum of 2,425 pounds of pull force. 29 Quicksilver grips were tested; all grips failed to meet the required standard. All the tested grip assemblies had jaws that were either new or had been rebuilt three weeks prior to the accident.
o the Yan 11 grips used a combination of rubber springs and steel wedges in combination with direct gravity assistance from the loaded chair to achieve grip slip force (most detachable grip designs use a steel spring arrangement). "Testing found that the elastomeric springs had significant, inconsistent load-deflection characteristics not only from one spring to another, but also as a group, when the temperature changed."
o the steel wedges were a design feature added in 1992 in response to low grip force values achieved after the lift had been in operation for only one year. Gordon found that the wedges did increase grip force but were subject to fairly rapid wear themselves. New wedges, as were on the Quicksilver at the time of the accident, also caused the grip to ride higher on the haul rope than the original design specifications, thus reducing the jaw grip wrap.
o "Increased susceptibility to vertical forces resulting from grip modifications (the addition of inserts) was one of the factors which caused carrier #146 to detach from the haul rope when it was bouncing up and down as a result of the sudden jerking stop. The fact that the Yan 11 grips relied, to a certain extent, on direct gravitational assistance to maintain grip slip force, also made the grips susceptible to the effects of vertical forces because the bouncing caused negative vertical forces on the grip and therefore negated some of the effect of the gravity assistance."
o documents supplied by the manufacturer state the maximum rope angle on the Quicksilver to be 35.5 degrees. However, Gordon’s investigation found the maximum rope angle to be 38 degrees. "This has a bearing on calculations for swing clearances and grip slip forces," he wrote. "This is a critical matter that must be accurate. It is a matter that must be carefully checked and rechecked before a lift goes into operation."
When it was suggested the design of the Yan 11 grip and chair were faulty Forseth said it was not so much "faulty" design but, "We’re learning that the design done was inadequate.
"The direction I think we’re going is that gravity grips should be done away with."
The Redline and Green chairs have used Yan 7 grips, which are not identical to the Yan 11 grips but are of a similar design. Whistler Mountain has a design team, a manufacturing team and a monitoring team working on a new grip for those lifts. The teams have been working closely with the ministry throughout the development process.
Gordon’s inquiry also found the emergency brake was being engaged when the normal "stop" button was used to halt the lift. The Z98 code requires motors to bring the lift to a complete halt without the assistance of another brake. "...misadjustments caused the performance monitor to sense an emergency and it shut the motors down during the normal stop and applied the emergency brake. The emergency brake stop was therefore more sudden and jerky in nature than a normal stop. This problem had existed for some time but it was not attended to."
Lift operation and maintenance staff also reported that there were a number of ongoing problems with some of the safety detection devices with the Quicksilver. These devices often needed adjustment of their tolerances.
In a press release, Whistler Mountain said Lift Engineering continued to have a major role in the ongoing maintenance of the lift from the date of the installation until the date of the accident.
Gordon concludes that when the lift stopped at 3:11 p.m. on Dec. 23, "the emergency brake engaged because the performance monitor had detected an abnormality. Prior to the emergency brake engaging, the electric motors shut down and the lift accelerated. When the emergency brake came on, the lift was jerked to a sudden stop. This combined sequence of acceleration and deceleration created unusually severe rope dynamics. As a result, the carriers bounced up and down in addition to swinging back and forth. The hanger arm on carrier #146 likely swung forward and struck the underside of the grip assembly. As noted, the grip and the hanger arm hand insufficient swing clearance and resistance to vertical forces. The bouncing motion may have created negative vertical forces on the grip, which eliminated the effect the carrier’s own weight had on the grip. The grip would have detached from the haul rope in a peeling type motion. The steep angle of the haul rope then allowed carrier #146 to slide freely and swiftly, which began the chain reaction collisions with the other carriers."
Gordon made a number of recommendations with regard to regulating chairlifts and aerial tramways. Two specific recommendations for Whistler Mountain have already been complied with, Forseth said. Communications between the lift operations and lift maintenance staff has been improved, as both departments now report to one authority. As well, staff training for lift evacuations has been improved.