http://www.villagephotos.com/pubbrowse.asp?selected=594734This ship never existed, but it was for a time a great source of worry for Starfleet. Based on incomplete and innaccurate battle reports, and the inherent assumption that the Andromedans thought and would build ships much like Starfleet did, intelligende and engineering analysts assumed that Andromedans could and would upgrade their ships into a new heavy cruiser analogue by welding a third engine and additional hull volume onto the bottom of a Conquistador. Extensive simulation combat trials showed that the Conqueror would be a dangerous opponent, but no Andromedan with a third engine ever appeared.
Over the decades during which the Andromedans went from random unknown menace to a major invasion, the various intelligence services from all the races evaluated what combat reports they could get of ships that (a) got close enough to an Andromedan to gain useful information and (b) survived the experience. The reports were fragmentary and the results of any analysis were often wrong, sometimes spectacularly so. The Federation, along with the other races in the Alpha sector, simply could not grasp the doctrines, design philosophies, and mental limits of the Andromedans, and more often than not assumed that the Andromedans would, logically, follow the same design doctrine the Federation and its neighbors used. The combat simulators were programmed with no end of bad guesses about the Andromedans, such as the use of improved Phaser-1's (it eventually turned out that the Andromedan "Phaser-2's" were an entirely different weapon that had similar effects, seeking weapons, fast patrol ships, and other specialized variants.