UPDATE 1-Pursuit Dynamics H1 rev falls 61 pct; CEO to retire

* H1 pretax loss 3.1 mln stg vs 3.5 mln stg a year ago

* Revenue starts to flow in 2 segments; visibility rises

* Shares fall 7 pct (Adds details)

June 30 (Reuters) - Biofuel-tech group Pursuit Dynamics Plc (PUDY.L) posted a 61 percent fall in turnover for the first half, and said Chief Executive John Heathcote gave notice of his retirement.

However, the company, which makes a fluid processing reactor that reduces energy usage, said it saw steady progress in two of its businesses -- fire suppression and decontamination.

"Revenues have started to flow in both areas since the end of the financial period and commercial visibility is increasing," it said in a statement.

Pursuit Dynamics said the process to select Heathcote's successor was underway. The CEO will remain with the company until Nov. 1 or a successor is appointed, whichever is earlier.

Pretax loss for the six months ended March 31 fell to 3.1 million pounds ($5.16 million), from 3.5 million pounds in the year-ago period, as expenses declined.

The company's turnover, including discontinued operations, decreased to 0.7 million pounds following the move to a licensing operation for food and brewing.

Shares of the Huntingdon-based company were down 6 pence at 78 pence by 0714 GMT on Tuesday on the London Stock Exchange. ($1=.6013 Pound) (Reporting by Purwa Naveen Raman in Bangalore; Editing by Anne Pallivathuckal)