Investigation into the LOT Boeing gear-up landing at Warsaw are focusing on the role of circuit-breakers, after the twinjet's undercarriage failed to deploy following a hydraulic leak.
The aircraft had departed Newark, bound for Warsaw, on 1 November when, during flap and gear retraction, the engine indication and crew alerting system warned of a malfunction in the central hydraulic system, which was suffering a loss of pressure.
Having opted to continue the flight to the Polish capital, the LOT crew carried out a quick-reference handbook procedure which included use of alternate landing-gear extension.
But the gear failed to extend and the aircraft was vectored to a holding pattern while combat aircraft were sent to observe the state of the undercarriage. The crew attempted to use gravity extension to lower the gear but this was unsuccessful, and diminishing fuel levels forced the crew to consider a gear-up landing.
The 767 landed on Runway 33 with its gear retracted, about 1h 15min after declaring the initial emergency. It came to a halt around 2,000m along the strip, where Runway 33 and Runway 29 intersect.
Preliminary inspection of the aircraft traced the central hydraulic system problem to a fluid leak from a damaged hose in the starboard main landing-gear.
But it also revealed that while the individual circuit-breaker for the alternate landing-gear extension motor was 'on', an overarching battery bus circuit-breaker - which protects several systems including the alternate landing-gear extension motor - was 'off'.
Polish investigation authority PKBWL said this 'off' position "was not recorded or indicated" either by the EICAS or the flight-data recorder of the 767.
Suspicion over the role of the circuit-breaker in the accident heightened during a test carried out as the aircraft was being recovered from the runway using cranes and air-bags.
After connecting a ground-power unit to the 767, and switching the battery bus circuit-breaker on, investigators successfully used the alternate landing-gear extension system to lower the undercarriage - enabling the aircraft to be towed to LOT's technical facilities.
"Functional tests of the entire electrical installation of the alternate landing-gear extension system are being conducted," said PKBWL.
None of the 221 passengers and 10 crew members was injured.
2011年5月2日星期一
CAT® 990 Wheel Loaders Keep Wood Moving at High Volume Paper Mill
On an average day, 450 log trucks rumble in and out of the woodyard at a paper mill in southeast United States. On a really good day, 600 trucks, each carrying 30 tons of pine or hardwood, queue up to be unloaded by one of two CAT® 990H wheel loaders or a 40-ton P&H portal crane.
The CAT wheel loaders were purchased in January 2010 to replace two log stackers. “The log stackers are good machines built well for unloading log trucks,” explains the mill’s woodyard superintendent. “It was more a reliability issue; they just would not hold up in our environment. The 990s were a Godsend. It was a nightmare when our old log stackers were our only machines.”
The woodyard superintendent is responsible for overseeing all activity in the yard from unloading log trucks to ensuring there are enough wood chips to keep the pulp mill well-fed 24/7. Basically, he’s got to keep the wood moving. “My biggest challenge now is making sure we have enough wood chips to feed the digesters of the pulp mill. We have to run very consistently, very reliably to keep the mill running,” he says.
Early in 2009 the biggest challenge was at the beginning of the process — getting log trucks unloaded quickly and consistently. “We would have problems with the log stackers. They would be down and trucks would back up for a half a mile out on the highway. We’d actually end up cutting trucks off for the day because we couldn’t get them unloaded because nothing was running,” he recalls.
Mill management decided to buy two new pieces of equipment. The main requirements for the new machines were: enough capacity to unload a log truck in one pass, stability to lift a full load off the ground without tipping and, of course, reliability. Bottom line, it was all about getting trucks unloaded and out of the woodyard in a timely manner.
Show and Tell
The team charged with determining what machine to buy included the mill manager, the procurement manager, the woodyard superintendent and a woodyard senior operator. They evaluated several makes and models of wheel loaders and log stackers. Besides the CAT 990, they also considered the smaller CAT 988 wheel loader. They still had a 1984 CAT 988B that had already gone through one rebuild and, at 100,000+ hours, now was used as back-up.
After doing their homework, they told their CAT dealer rep, Mike Farris with Thompson Machinery in Tupelo, Miss., that they wanted to go look. So Farris arranged for a one-day whirlwind tour on the company jet to several locations in Georgia and South Carolina to see both the 990 and 988 working in mills doing the same work they needed them to do — unloading 30-ton trucks and reclaiming wood off the ground.
The evaluation team concluded that the 988 could do the job unloading 60,000 lb. truckloads in one pass, but it would be working at close to its maximum tipping capacity of about 65,000 lbs. They were concerned that the machine wouldn’t survive its full life cycle working at the maximum every minute of every day. On the other hand, with a tipping capacity of about 90,000 lbs., the 990 could unload 60,000 lb. truckloads, with another 30,000 lbs. of available capacity to spare.
One mill they visited in South Carolina had two 990s. “The company shared its maintenance records that showed one of the wheel loaders had 30,000 hours and basically no down time other than a hose or two. That’s what the company was looking for — a machine they did not have to work on,” Farris says.
The senior operator was able to ride along with the 990 operator in the jump seat. “I could tell what the machine was capable of doing, just riding with him,” he says. “I didn’t actually unload a truck or handle any wood, but I did operate the machine just to get the feel of it and the functions.”
He asked himself if he would want to run the 990 on a daily basis. “Comparing it to all the machines I’ve experienced in my years at the mill, I thought this was going be a real nice machine — a lot easier to operate, a lot more comfortable,” he says. “The cab was roomy and all the controls were user friendly and handy.”
He especially liked the joystick operation compared to the steering wheel in the old 988 back in the woodyard. “The joystick just seems to give you more room in front. You don’t have that big steering wheel right there in front of you. And I feel like I have a little more control, too.”
According to Farris, by the end of the day, the mill team had pretty much made up their minds that the 990 was the machine size they were looking for.
The CAT wheel loaders were purchased in January 2010 to replace two log stackers. “The log stackers are good machines built well for unloading log trucks,” explains the mill’s woodyard superintendent. “It was more a reliability issue; they just would not hold up in our environment. The 990s were a Godsend. It was a nightmare when our old log stackers were our only machines.”
The woodyard superintendent is responsible for overseeing all activity in the yard from unloading log trucks to ensuring there are enough wood chips to keep the pulp mill well-fed 24/7. Basically, he’s got to keep the wood moving. “My biggest challenge now is making sure we have enough wood chips to feed the digesters of the pulp mill. We have to run very consistently, very reliably to keep the mill running,” he says.
Early in 2009 the biggest challenge was at the beginning of the process — getting log trucks unloaded quickly and consistently. “We would have problems with the log stackers. They would be down and trucks would back up for a half a mile out on the highway. We’d actually end up cutting trucks off for the day because we couldn’t get them unloaded because nothing was running,” he recalls.
Mill management decided to buy two new pieces of equipment. The main requirements for the new machines were: enough capacity to unload a log truck in one pass, stability to lift a full load off the ground without tipping and, of course, reliability. Bottom line, it was all about getting trucks unloaded and out of the woodyard in a timely manner.
Show and Tell
The team charged with determining what machine to buy included the mill manager, the procurement manager, the woodyard superintendent and a woodyard senior operator. They evaluated several makes and models of wheel loaders and log stackers. Besides the CAT 990, they also considered the smaller CAT 988 wheel loader. They still had a 1984 CAT 988B that had already gone through one rebuild and, at 100,000+ hours, now was used as back-up.
After doing their homework, they told their CAT dealer rep, Mike Farris with Thompson Machinery in Tupelo, Miss., that they wanted to go look. So Farris arranged for a one-day whirlwind tour on the company jet to several locations in Georgia and South Carolina to see both the 990 and 988 working in mills doing the same work they needed them to do — unloading 30-ton trucks and reclaiming wood off the ground.
The evaluation team concluded that the 988 could do the job unloading 60,000 lb. truckloads in one pass, but it would be working at close to its maximum tipping capacity of about 65,000 lbs. They were concerned that the machine wouldn’t survive its full life cycle working at the maximum every minute of every day. On the other hand, with a tipping capacity of about 90,000 lbs., the 990 could unload 60,000 lb. truckloads, with another 30,000 lbs. of available capacity to spare.
One mill they visited in South Carolina had two 990s. “The company shared its maintenance records that showed one of the wheel loaders had 30,000 hours and basically no down time other than a hose or two. That’s what the company was looking for — a machine they did not have to work on,” Farris says.
The senior operator was able to ride along with the 990 operator in the jump seat. “I could tell what the machine was capable of doing, just riding with him,” he says. “I didn’t actually unload a truck or handle any wood, but I did operate the machine just to get the feel of it and the functions.”
He asked himself if he would want to run the 990 on a daily basis. “Comparing it to all the machines I’ve experienced in my years at the mill, I thought this was going be a real nice machine — a lot easier to operate, a lot more comfortable,” he says. “The cab was roomy and all the controls were user friendly and handy.”
He especially liked the joystick operation compared to the steering wheel in the old 988 back in the woodyard. “The joystick just seems to give you more room in front. You don’t have that big steering wheel right there in front of you. And I feel like I have a little more control, too.”
According to Farris, by the end of the day, the mill team had pretty much made up their minds that the 990 was the machine size they were looking for.
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