On the C-5, with all hydraulics unpowered, it had a phugoid oscillation. It could be suppressed by applying and reducing power at the right times; my memory is power off at the top and power up at the bottom. In the sim, most guys could handle the phugoid, once they a handle on the period which was quite long and induced overcontrol.
Pitch could be controlled by adjusting CoG (dump fuel, move cargo/pax) and using the ground spoilers (override the ground-only restriction). Again, in the sim, one could usually have a controlled crash on the airfield. They did a very loosely controlled crash in Saigon and, like Souix City, many survived.
GF