UPDATE 1-Spirent CEO steps down, CFO takes charge

* CEO Bill Burns to step down immediately

* CFO Eric Hutchinson to take charge

* Stock the largest percentage gainers on mid-cap FTSE 250index

By Tasim Zahid

Sept 3 (Reuters) - British telecoms testing company SpirentCommunications Plc said Chief Executive Bill Burns wouldstep down immediately, and Chief Financial Officer EricHutchinson would take charge, sending its shares up as much as5.8 percent.

Spirent did not comment further on Burns' exit from thecompany, where he was at the helm since 2008.

Shares in the Crawley, UK-based Company were up 4.8 percentat 134.7 pence at 0858 GMT on the London Stock Exchange. Thestock was the largest percentage gainer on the mid-cap FTSE 250index.

"The change is unexpected and appears to be a consequence ofthe disappointing performance of the business over the pastyear, where Spirent has faced challenges in its core markets andmissed some opportunities to benefit from stronger adjacentmarkets like security testing," Numis Securties analyst NickJames said in a note.

The company has been struggling over the past few quartersand reported a 72 percent drop in first-half profit last monthdue to lower orders and a weak performance at its network andapplications unit.

"The timing of this departure suggests that perhaps we arenot going to see a turnaround this year," Jefferies and Coanalyst Lee Simpson told Reuters.

Spirent, which tests ethernet networks and 3G and 4Gwireless networks and devices, said in a statement on Tuesdaythat it would begin the search for a new CEO in due course.

"They have got an excellent (possible) CEO in a lady calledSue Swenson, who is already on the board," Panmure Gordonanalyst George O' Connor told Reuters.

Sue Swenson is a independent non-executive director on Spirent's board and has served as President and CEO of SageSoftware Inc and mobile service provider Cellular One in thepast.

However, Numis's James said it is likely that such anappointment could take a year or two.