Imagine: A plane with 24 passengers crash lands on Dec. 25 on the campus of the Westport Senior Center. Outside on this Christmas Day, the temperature is 16 degrees. Well below freezing.

Mercifully, there is no fire but there are injuries.

That was the scene as CERT teams from Westport, New Canaan, Fairfield and Wilton arrived at the mock crash site.

The well-trained CERT volunteers deployed to assist with triage -- assessing and helping to classify passengers according to treatment needs: walking wounded, injured who cannot walk, those in shock or with blocked airways, or those who are bleeding profusely. In the worst case scenario, as tragic as case may be, some passengers are judged beyond help.

Instructors reminded the CERT volunteers: When assessing injuries be on the lookout for "the three killers: shock, blocked airway, bleeding."

CERT stands for Community Emergency Response Team. The CERT crews from the four towns, after assisting with triage, treatment and transport of victims to the hospital, discovered they had four missing passengers.

That called for a search-and-rescue operation in the wooded area.

You see, 20 victims were identified at the crash site. But since the passenger manifest indicated there were 24 aboard -- four were missing.

Beyond the mock crash site the members of the CERT crews commenced a second drill, this time performing a mock search-and-rescue for a family of four that had gone on a hike in the woods earlier in the day and had not returned to their SUV parked near the woods.

Relatives told CERT crews that a couple and their two sons left for their hike hours ago. Night was drawing near.

For communication in each situation, CERT members have two-way radios, a whistle -- two blows signal you need help -- a flashlight and, between the ears, rigorous training that equips them to respond to each situation -- always putting safety first.

Responding to the scripted "emergencies" -- before EMS or other first responders could get to the scene -- the drill was designed to test the CERT crews' abilities to work together.

Ernie Heidelberg, president of Westport CERT, explained the rationale of the combined CERT briefing/drill.

"This is to test the ability of CERT crews from the four towns to work together for the first time," he said. "In training, emphasis with all CERT volunteers is on safety first. Also, in the field volunteers use the buddy system. No one goes into any situation alone."

During the classroom part of the operation that started at 1:30 p.m. and ran until 6:30 p.m., about 100 participants wearing lime-colored CERT vests were briefed on radio operation, search-and-rescue and first aid (triage).

Before the drills in the field, the estimated 100 CERT volunteers from the four towns sat at tables in the Westport Police Training Center through two hours of intense refresher briefings on those same topics.

In the four towns in recent months, CERT volunteer have lent a hand with traffic control, most notably during parades. They also have been on the scene helping with crowd control during special circumstances -- such as the first-come, first-served administration of free H1N1 flu vaccine at the Westport/Weston Health District.

The CERT operation emerged on the national scene in the post-Sept. 11 period. The idea: when requested, CERT crews will augment local first responders -- police, emergency medical and fire departments.

This might be called for in the face of man-made or natural disasters -- such as terrorist attacks or hurricanes.

Jim Cole instructed them in their first use of the 2-way radios. Cole, New Canaan police commissioner, heads New Canaan's CERT crew.

"This works nothing like a telephone," he said.

In other words, you don't just carry on a conversation. There are protocols with the two-way radios. Demonstrating, he activated the start switch. You activate it, wait for 2 seconds and then talk, he noted. When you have completed your message, you release the switch.

"These are life savers," Cole said, waving his radio. "Once you use one twice, it's as easy as falling off a log."

When the operation moved outdoors to the campus of the Westport Senior Center, CERT teams gathered in the lower parking lot off Imperial Avenue.

The volunteers were broken into six groups.

Commanding the operation was Westport CERT's Mark Nodzelensky, barking orders into his two-way radio. He used it with military precision.

Following his orders, the first groups marched up the hill, stinging rain in their faces. They reached the site of the simulated crash. There was no fire, a fact that had been ascertained earlier.

In a short time, a radio from up on the hill crackled: "Two dead."

Further communications provided an inventory of injuries. The successful first use of the two-way radio showed Cole's instruction in its use did not fall on deaf ears.

For the second simulated emergency -- the search-and-rescue for the missing family -- the outcome was favorable. The missing were located.

In the case of each situation, large plastic signs, secured on the flat surface of the ground, provided clues.

These tipped off the CERT crews to, for one example, the location of the dead. And, in other instances, locations of injured.

Andree Brooks, Westport author and journalist, into her fourth year as a CERT volunteer, helped with the mock search-and-rescue for the family.

"I think the operation was successful," she said Sunday in an interview. "We accomplished what we set out to do: prove that we could work together."

Even the two-way radios used in Saturday's operation during inclement weather passed the "waterproof" test in the field.

Considering it was the first time for the CERT strangers from the four towns to accomplish their mission -- working together as a team -- Saturday's operation was declared a success. That included CERT leaders who designed the briefing/drill and veteran CERT volunteers with years of service.