Tomas Dusek, 37, from Buckinghamshire, was in Peru in June 2012 looking at sites for a hydroelectric plant.
The Sikorsky helicopter chartered for the trip crashed in the Andes Mountains killing all 14 on board.
Mr Justice Hamblen ruled his employer StormHarbour Securities was liable as it had breached a duty to provide him with a safe place of work.
Mr Dusek was on duty for the independent global markets and financial advice firm when the helicopter crashed in bad weather.
He left his wife Angela and two children, then aged eight and five, who live at Gerrards Cross.
At the London High Court, Mr Justice Hamblen said his employers owed a duty to take reasonable care not to subject Mr Dusek to unnecessary risk.
If StormHarbour had made an investigation it would have told Mr Dusek not to go on the flight, Mr Justice Hamblen said.
"Although Mr Dusek was prepared to take risks, he did so on a calculated basis. He was also a devoted family man.
"He would not have taken on the risk of this flight in the light of an instruction not to do so from his employer on safety grounds."
The hearing was not concerned with damages at this stage.
Mrs Dusek said: "Tomas was a wonderful father and a loving and cherished husband.
"When he stepped on board the helicopter as part of his job, we expected and assumed it to be safe, not that he would be putting his life at risk and leaving us devastated by his death.
"My husband's life was thrown away by StormHarbour's disregard for his safety."
A businessman's widow has won a High Court action against his employers over his death in a helicopter crash.