A medical helicopter that crashed this month in the dark hills north of Reno, Nev., killing three, lacked safety features recommended for years by federal experts, including night vision equipment and a system to warn the crew when the aircraft was too close to obstacles or the ground.

The Nov. 14 accident was the industry's second fatal crash this year and remains under investigation. But as was the case in this year's previous lethal accident, in South Carolina in September, the helicopter did not have equipment onboard that federal investigators have said probably can prevent crashes.

The pilot was flying by sight, and the helicopter was not equipped for instrument-guided flight. The helicopter also lacked an autopilot system, which would have kept it level and on course even if the pilot had become disoriented, said Ted Lopatkiewicz, a spokesman for the National Transportation Safety Board. Lopatkiewicz was responding to questions from The Washington Post about the safety features.

The NTSB has urged medical helicopter programs to adopt those safety features, concluding that they could have helped prevent some accidents. Medical helicopters are permitted to operate without many of the safety features required on commercial airliners.

Killed in the crash were pilot James Bradshaw, 39, of Kapaa, Hawaii, and nurse Clinton Reger, 40, and paramedic Christopher Ritz, 37, both of Susanville, Calif. The helicopter went down in California near the Nevada line.

Last year was the deadliest yet for the $2.5 billion air ambulance industry, with 28 crew members and patients killed in seven helicopter accidents. Working on a medical helicopter has become one of the most dangerous jobs in the country, The Post reported in a series of articles published in August.

The helicopter that crashed Nov. 14, which was operated by Mountain Lifeflight, was returning to its base in Susanville about 2 a.m. after delivering a patient to Renown Medical Center in Reno. In 2002, a company pilot misjudged his altitude, became disoriented and flew a medical helicopter into a lake. The daytime accident killed him and injured two crew members.

Mountain Lifeflight operates at high altitudes where the weight of added equipment has a greater effect on lift and performance, said General Manager Brian Gray, explaining why the helicopter did not have some safety features. His company runs ground ambulances and airplane ambulances but had only one medical helicopter. The firm was in the market for a second helicopter before the crash, and is planning to include safety upgrades in its next copter, Gray said.

Gray said the company had been waiting for specific guidance from federal agencies before buying enhanced equipment. "We needed to see where the industry was going. It wasn't something we were willing to just dive into," Gray said. "There are a lot of neat toys, but you want an industry standard."

In keeping with other NTSB recommendations, Mountain Lifeflight tracks its flights by radio through a central dispatcher and requires pilots to use and file a written checklist assessing risks such as weather conditions before beginning a flight.

Gray said he was frustrated that the NTSB, which can only recommend improvements, and the Federal Aviation Administration, which regulates aviation, have not agreed on the features and procedures that should be required for medical helicopters. "I get the sense there is not a friendly relationship between those entities, and that ties up things," he said.

In September, the NTSB said insurance payments for air ambulance flights should be linked to safety, particularly federal Medicare reimbursements, which cover many of the trips. That recommendation followed years of statements listing equipment and procedures that the board said could reduce accidents.

After relying heavily on voluntary compliance and arguing against state regulation of medical helicopter flights, federal transportation officials have begun considering mandatory rules. But those probably would not be ready before 2011, FAA officials have said.

Meanwhile, Sen. Olympia J. Snowe (R-Maine) is promoting an amendment to health-care reform legislation that would require medevac helicopters to meet certain aviation, patient safety and quality standards to receive Medicare reimbursement. Opponents say the proposal would reduce service in some parts of the country.