DENVER - Tests did not go well earlier this week for the $193 million automated baggage system at Denver International Airport, according to a spokeswoman for the city.

Computer programming problems on United Airlines' Concourse B caused automated carts to wander aimlessly around the tracks without going to their designated positions to pick up bags, according to Amy Lingg a spokeswoman for the city's public works department.

The tests are crucial to opening the $4 billion-plus project as scheduled on May 15, more than six months after it was originally scheduled to open.

When the airport opening was delayed in December to March 9, the fire alarm system and installation electronic systems were partially to blame, but the complicated bag system was the chief culprit. When March rolled around, the rest of the airport was ready, but testing on the bag system lagged as software problems mounted.

The chief problem now is to get the system up and running with enough time to allow the airlines to train their personnel on it. On Wednesday, the full-scale system test was scheduled to run on the two main concourses, Continental Airlines' Concourse A and United Airlines' Concourse B.

Wednesday's test, followed by an identical test scheduled for Thursday, is expected to involve 7,000 bags, compared to the 72,000 that are handled on an average day in Denver's Stapleton Airport.

Investors and rating agency analysts are holding their breath as the system is tested. Analysts stress that money must begin flowing so the airport, can begin paying its $3.2 billion debt load - or the market and the rating agencies will begin to sell off the debt and the agencies will probably downgrade the debt.

Moody's Investors Service rates the debt conditional Baal. Standard & Poors Corp. rates it BBB. Both ratings two notches above non-investment grade.

City and construction officials said earlier this week that although they are confident the system win be 95% effective by opening day, they will not open the airport without an automatic baggage system on concourses A and B, which will account for 80% of the traffic in Denver.

"There is no question there is a base level of operations the system must maintain," said the city's chief project engineer, Ginger Evans.

Acknowledging that the airlines want the system to be 99.5% effective on opening day, Gene Di Fonso, president of BAE Automated Systems Inc. and designer of the system, said, "I'll give you a guess. On day one, they'll probably not get 99.5%. They'll be well over 95%, though. My contract with Denver requires an efficiency of 99%, but we have 90 days post-[date of beneficial occupancy] to do it."

Limited tests are running at 95% proficiency, Di Fonso said, after early troubles with electrical current flow and other problems. But problems remain. Tests are still producing scanner problems, where a cart zips through a scanner but the computerized bar coding is not read properly. And the software programming still has not produced the required number of empty carts to show up where they need to show up.

Part of the 4,000 carts that are pushed on by motors installed on 22 miles of steel track are for oversized luggage items. In Colorado, that means skis and golf clubs. Di Fonso said the system is designed to handle 2,000 pieces per hour of odd-sized luggage such as skis.

"DIA will have a precedent-setting capacity for odd-sized luggage. I have not seen this around the world and I probably won't again in my lifetime," Di Fonso said.

The system is designed after a similar one in Frankfurt, although Denver's will be larger and accomplish more tasks. After years of problems, Frankfurt boasts a bag loss of five per million, a record that conventional systems cannot come near matching, Di Fonso said.

The bag system entwines around the huge terminal complex and the three concourses sitting perpendicular to the terminal in five separately operated loops. Each loop is self-contained, but special gates allow carts to transfer to another system if there is an inter-airline transfer.

The following is a list of other key functions of the system:

* Destinated Coded Vehicles, also known as telecars or carts. These are containers on wheels that carry baggage along a 28-inch-wide track. The cart has three positions for loading, carrying, and unloading baggage.

* Carts without engines. Instead, carts are propelled by linear induction motors that don't have moving carts, instead working off of electromagnetics. The cart has a protruding metal fin that passes through a trackmounted motor, which has a slot. An electromagnetic impulse propels the cart to the next motor.

* Carts with their own radio frequency reader. The reader is a hockey puck-sized sensing device that responds to a radio frequency emitted by a track-mounted reader. The main computer tracks each cart through the readers. Photocells mounted in the track also tell the computer the car has passed a certain point.

* An encoding console for each bag loop. The console has a work station where baggage handlers can manually route a cart using a keyboard connected to the mainframe computer. Airline handlers use this for in-bound and transfer bags.

* A programmable logic controller to route the carts. Each loop has its own controller. The computer sends "open" or "close" signals to routing devices installed on the track, similar to the way railroad trains are switched.

* Manual coding stations. If a bag isn't scanned correctly, the cart veers off to a station. There, baggage handlers route the cart to where it needs to go. The sorting rate is the number of bags correctly sorted the first time they pass through the scanner.

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