Cerberonics Inc., a Falls Church-based defense contractor, expects to suffer a "dramatic" reduction in its earnings after losing a key Navy contract to manage spare parts for the C-9 aircraft, a company official said yesterday.

The company, which has about 350 employes, has been managing spare-parts storerooms for the C-9 since October 1982, according to Cerberonics Vice President Ludwig Lippert. But the company recently lost out in the rebidding for the $36.3 million contract to Surveyor Inc., a division of E-Systems Inc. of Dallas.

The loss of the contract is a major blow to Cerberonics and will have a significant effect on revenue, Lippert said. During the fiscal year ending June 30, the C-9 accounted for $23.2 million of the company's total revenue of $40.3 million. Cerberonics had profits for the year of $1.256 million.

Lippert said the company currently is studying what impact the loss of the contract will have on its operations and whether employes will have to be laid off. He noted that the company has enjoyed "enhanced" revenue for the past few years as a result of the contract and any losses it suffers will only cut into that revenue.

"It's impossible to say what the consequences will be," Lippert said. "But we view this as an intermittent setback."

Lippert also said "only a few" workers are employed at the 13 C-9 storerooms around the country. He said the company hopes to take up the slack by bidding on contracts in its other divisions, which perform such services as systems testing, logistics and research for the Pentagon.