It was about 1900. No pictures but I heard them first thinking it was the usual monthly flyover by the three Chinooks. Something just wasn't right about the sound though. I heard a very loud deep rumble like the Chinooks but also a turbine whine and not very much whop whop whop the Chinooks usually have. It kept getting louder like the Chinooks do but instead of south to north these were coming right at me from the west. They flew right over my house then turned echelon right over Hefner Parkway and headed south.