Victor 398

Victor 398 was a UNSC Pelican dropship which crashed into the mountain gorge that is the Halo 3 multiplayer level, Valhalla. The crash, which the crew barely survived, also scattered the Pelican's contents throughout the valley. V-398's rear hatch is sealed, presumably by its surviving crew, which denies access to the bird's interior.

You can briefly see Victor 398 being shot down by a Brute fighter during the opening battle over the Ark in Halo 3's Campaign.