(CNN) -- Investigators are again on the scene of a fatal medical helicopter crash. Four people were killed Saturday night in suburban Washington when the chopper operated by the Maryland State Police went down in a park.
The emergency medical-services helicopter had picked up two automobile accident victims and was attempting to land when air-traffic controllers lost contact with the pilot. Authorities said the pilot had twice radioed for help in foggy weather.
Nationally, it was the eighth fatal medical helicopter crash in the past 12 months.
Pilots, flight nurses and paramedics who fly emergency medical operations often must navigate rough terrain, darkness and bad weather. But the National Transportation Safety Board says the accident rate for such flights is far too high.
"The Safety Board is very concerned with the increasing number of these EMS helicopter accidents," said Robert Sumwalt, the NTSB's vice chairman. "We have had too many of them. The number is increasing. We need to do something about it. We need to do something about it right now."
It's a problem that David Bacon of Simpsonville, South Carolina, and his wife, Barbara, know only too well.
Their son, David Bacon Jr., was killed along with three others on an EMS helicopter July 13, 2004, in Newberry, South Carolina. Their aircraft hit some trees in fog about 5:30 a.m. after picking up a patient from an accident site on an interstate.
The senior Bacon, a volunteer firefighter when David Jr. was a boy, remembers exactly when his son decided he wanted to be a paramedic.
"Another volunteer firefighter worked as a flight paramedic. I took him down there one day when he was working, and [my son] got a tour of the helicopter. He was 13 years old, and I have the picture, him standing by the helicopter. And that's when he decided that's what he wanted to do," Bacon said. "That flight paramedic was also one of his pallbearers."
Bacon's crash was one of 55 EMS aircraft accidents investigated by the NTSB between January 2002 and January 2005. Those accidents resulted in 54 fatalities and 18 serious injuries.
In a 2006 report on the crashes, the NTSB found that 29 of those 55 accidents could have been prevented.
The NTSB identified four recurring safety issues:
• Less stringent requirements for EMS operations conducted without patients on board.
• A lack of aviation flight-risk evaluation programs for EMS operations.
• A lack of consistent, comprehensive flight-dispatch procedures for EMS operations.
• No requirements to use technologies such as terrain awareness and warning systems to enhance EMS flight safety.
The NTSB report showed that although 38 percent of all helicopter EMS flights occur at night, 49 percent of accidents during a 20-year period occurred during the night.
"We are an independent federal agency, charged by Congress to investigate transportation accidents, to determine the probable cause, and then to issue safety recommendations. And when those recommendations are not implemented, lives are lost, needlessly," Sumwalt said.
Although the NTSB offers recommendations, it is the Federal Aviation Administration that has the power to make regulations mandatory.
"We understand the NTSB safety recommendations, and we agree with all of them," said Jim Ballough, director of the FAA's flight standards service. "We also understand that rulemaking takes a long time," he said.
The details of the federal rulemaking process provide little comfort to Bacon's parents.
"It is now four years [since the crash], and I have seen no response to any of the recommendations made by the NTSB," Bacon said. "Why the FAA either doesn't want to deal with it, doesn't want to take action, doesn't have funds allocated to do this, I don't know what their problem is."
One technology that veteran EMS pilots say could improve their safety is the use of night-vision goggles. Developed for use in the military, the goggles can improve visibility for pilots flying in darkness. The NTSB has encouraged night-vision goggle use since 2006. It costs about $60,000 to train two pilots and retrofit an aircraft cockpit with night-vision technology.
But because of the wars in Iraq and Afghanistan, there is a shortage of the goggles. In the United States, the military gets first access to the goggles, and only a couple of companies manufacture the complex, and classified, equipment.
Fewer than a third of about 800 EMS helicopters in the United States have night-vision technology. A lot more would like it, according to a survey of 382 active helicopter EMS pilots by the National EMS Pilots Association.
The survey, published in May, found that 82 percent of pilots prefer to use night-vision equipment. Among their comments:
"I feel night-vision goggles have improved the safety in our program more than any other thing I have seen in 17 years of EMS flying."
"Landing in unimproved areas at night without NVGs is idiotic!"
"The FAA many times seems to hinder rather than enhance safety with some of their rules made by out-of-touch desk jockeys."
"I left my last job because they didn't have a NVG program."
Mike Atwood, owner of Aviation Specialties Unlimited in Boise, Idaho, is the distributor of night-vision systems for ITT Technologies, the largest U.S. manufacturer. His company provides training for pilots in the use of night-vision goggles and modifies cockpits for their proper operation.
He said the waiting time for civilian uses of the goggles, mostly emergency medical services and law enforcement, is about six to eight months.
"The [ITT] plant is maxed out. They are operating 24 hours a day, 7 days a week," Atwood said. "It would be very difficult to make any more than they are making right now."
Atwood said night-vision technology has improved dramatically since it was introduced in World War II. He first used the goggles in the military in 1978.
"I thought, this is the greatest thing in the world. Even though they were a full-faced goggle then, you could go into dark areas and be able to see," he said.
The equipment Aviation Specialties sells is a third generation of the technology. It works through "image intensification," amplifying a small amount of light from the moon or stars to produce a green image.
As CNN correspondent and pilot Miles O'Brien learned when he flew with Aviation Specialties pilot Justin Watlington, there is no doubt that the equipment makes night flying safer. So when might the FAA adopt the NTSB's safety recommendations? Watch O'Brien's report on proposed changes »
"I can't give you a timeframe at this point. We continue to strive to enable the technology to be implemented by these [EMS aircraft] operators, and we will certainly look to codify that in the future," said the FAA's Ballough.
Meanwhile, 52 people have died in EMS flight accidents since the NTSB made its recommendations in 2006. Nearly two-thirds of those fatalities, including Saturday's crash in Maryland, involved nighttime or poor-visibility flights.
David Bacon says there is a big hole in his life because of his son's death. But he can't get angry.
"I'm just thrilled, I know his mother is thrilled [our son] got to do what he wanted," he said. "He got to live his dream, and he got to do it for a year. I wish it had been 20 years."