Almost every modern Army heli has a built in APU. THose larger turbines are difficult, if not impossible, to start on regular battery power and require either hydrualic or air to crank 'em.

I've never seen an APU catch fire but have heard of uncontained failures which lead to a safety message not to stand underone or to the side of one when it is running ;-)

The cancellation of the Comanche program will allow the Army to buy many more UH-60 and CH-47 helis.