The Cessna's engine had stopped in mid air and Mr. Bohannon landed on the freeway shoulder in the direction of traffic just north of Farm Hill Boulevard in unincorporated Woodside, according to a report from the California Highway Patrol. There were no injuries.
The CHP did not speculate as to the cause of the engine failure. The accident and its causes are most likely being investigated by the Federal Aviation Administration, according to an agency spokesman.
Wendy Kwon, 47, of Sausalito was driving alone in the Mercedes, CHP officials said. In addition to the broken window, the car's roof was dented near the center, the CHP said. It was towed from the scene, as was the plane, though it was not damaged.
Why didn't the plane crash when its tire hit the car?
"When the tire hit, it would be with enough force to damage the vehicle but not enough to damage the landing gear," said CHP Officer Scott Neimeth in a phone interview. Mr. Neimeth said he is a pilot and familiar with the Cessna 210.
Landing gear is designed to provide give-and-take in several directions so as to cushion the landing, he said. On this plane, the landing gear has a suspension and is retractable and built to withstand thousands of pounds of pressure, he said.
In this case, Mr. Neimeth said, although Mr. Bohannon had no engine power, he apparently did have enough lift and forward momentum, and skill, to lift the plane off the car and on to a safe spot on the edge of the road.
Pilot radioed airport
Mr. Bohannon, 53, is a senior vice president at Bohannon Development Corp. based in San Mateo, according to a spokeswoman from his office. He is a grandson of David D. Bohannon, a legendary Peninsula developer, and the brother of David Bohannon, the company's current chief executive.
Mr. Bohannon had taken off from the San Carlos Airport on a test flight and was on his way back when the mechanical failure occurred, CHP Officer Art Montiel said. Mr. Bohannon radioed the airport as he was landing.
The CHP began to receive reports at 7:13 p.m. that a small aircraft had landed on the highway. As officers were responding, the airport also contacted the CHP about the incident.
Federal Aviation Administration spokesman Allen Kenitzer said the plane was conducting a photo mission when it lost engine power.
Landing on a freeway
That there were no injuries in this accident is probably more an indication of the pilot's skill rather than luck, said Chris Dancy, a spokesman for the Aircraft Owners and Pilots Association in Frederick, Maryland.
A pilot's first responsibility in any emergency may sound simple: fly the plane, Mr. Dancy said in a phone interview. Without an engine, a Cessna 210 becomes a glider and the pilot has full use of the controls just as if the engine were running, he said. The links to the plane's controls are cables and rods, but nothing hydraulic that is dependent on engine power.
An equivalent responsibility is safety. "From the first time a pilot sets foot in the plane, all of the flight training focuses on safety," Mr. Dancy said, adding that the pilot is solely responsible for the safety of any flight.
The pilot's job in such a situation is to manage and mitigate risk, which includes calculating a rate of descent over the longest distance, a formula known as the best glide speed, Mr. Dancy said. If the plane is high enough above ground, the pilot has "a fair amount of time" to make these calculations, he said.
While there are no guidelines for emergency landings on freeways, they are a natural choice, Mr. Dancy said. "What is more attractive than something that looks like a runway and behaves like a runway?" he said. "If you're fortunate to be near a major highway that's got a good straightaway, that's obviously an option."
The FAA agrees. "Typically, when a pilot is put in a position to have to get the airplane down in an emergency, it is a matter of choosing the least worst place to land," spokesman Lynn Lunsford said in an e-mail.
Asked if a citation was likely, CHP Officer Neimeth deferred to the FAA. Mr. Lunsford, asked the same question, deferred to the CHP but added that the FAA would not be issuing any citations. "This is an emergency situation, not a planned event," he said.
Bay Cities News Service contributed to this report.