* Engineering firm says 2015 to be "meaningfully" belowforecasts
* Stock plunges to three-year low
* Analyst expects 10 pct downgrade to 2015 EPS
* Shares down 19 pct (Adds analyst's comment, background)
LONDON, Oct 28 (Reuters) - Shares in Meggitt plunged on Wednesday after the UK engineering firm warnedprofits this year would be "meaningfully" below forecasts afterdemand for spare aircraft parts deteriorated and its energyindustry business suffered from low oil prices.
The supplier of wheels, brakes and electronic systems toplanemakers said trading in the third quarter was below itsexpectations, with comparative sales down 1 percent, due to amarked deterioration in September.
Meggitt said it sold fewer spare parts for aircraft thananticipated in the period, dealing a blow to the company whichmakes its best margins in the so-called aftermarket, and abusiness which one analyst said accounted for about half ofgroup profits.
Shares in Meggitt, a FTSE 100 stock, were 19 percent lowerat 372.8 pence at 1102 GMT, their lowest level in three yearsand wiping some 680 million pounds off the company's marketvalue.
Meggitt's equipment on some older types of planes affectedits trading in the period as more of those planes were taken outof service and broken up, flooding the market with alternativesupplies of spare parts.
Warning that it expected these factors to persist in thefourth quarter, Meggitt said underlying operating profit for theyear would come in "meaningfully below" the current consensusmarket forecast of 369 million pounds ($564 million).
"We expect 2015 consensus earnings per share will likelycome down by around 10 percent, and by more in 2016. Today'swarning raises questions on the timing of recent acquisitions,"Investec analysts said in a note.
Shares in other UK companies operating in aerospace anddefence markets also fell in reaction to Meggitt's tradingstatement, analysts said. Senior fell 2.3 percent andCobham was 3.8 percent lower.
The profit warning came as a surprise after the company inAugust stuck with its forecast for growth this year, creditinghigher spending on military aircraft with offsetting declines inthe oil industry-related energy business, which has been underpressure for some time due to the lower oil price.
The group said on Wednesday it was now looking at options tocut around 300 jobs from its global workforce due to thechallenging trading conditions in the energy business, wheresales fell 16 percent in the third quarter. The businesssupplies valves for oil and gas projects and accounted for about10 percent of revenues in 2014.
Organic sales in the military division were down 2 percentin the third quarter, and Meggitt said it was also affected by anumber of programme deferrals.
The job cuts would be completed by the end of the firstquarter 2016, Meggitt said, but added that it would take anexceptional charge in 2015 to cover the cost. ($1 = 0.6539 pounds) (Reporting by Li-mei Hoang and Sarah Young; Editing by GregMahlich)
