One of the major design flaws discovered during the flight testing of the early Halifax prototypes was rudder overbalance at low speeds. This meant that with the trim applied, the rudder would overbalance at speeds below 150 mph. This issue became even more pronounced when one or two engines were stopped on the same side of the aircraft. This flaw had deadly consequences when the aircraft was introduced to squadrons. While not explicitly stated to have been an issue with the prototypes, early production aircraft suffered from a "vicious swing on take-off causing inherent undercarriage collapses". This issue, combined with the rudder stall problem, made the early Halifax a "poor design" in the eyes of some.