The principles that
Cuban_8 referred to are in a diagram here (although the engine is older than some and not a high by-pass):
Avon Engine.
It may take some time to load – 1mb.
Do not get into any further discussion about the length of the jet pipe as shown in the diagram. It is clear that the thrust is generated by the main components of the engine. For prop engines most of the thrust comes from … the prop.
Rear fuselage strakes, particularly those on the under side, are generally used to enhance directional stability at high angles of attack where the fin effectiveness is reduced. On prop aircraft a large directional / rolling effect comes from the swirl of the prop airflow hitting the rear fuselage and fin as described by
BigGreenPleasureMachine .
747FOCAL from your description of the tests that you sat through it appears that those pilots were doing something very stupid. No test should be conducted with the need to readjust cg in flight to effect a recovery and any Vmca test is complete when it is no longer possible to maintain heading, well before any loss of control. Furthermore, your description was of a classic stall limited Vmca test. Vmca is defined where directional control is lost or by aerodynamic stall whichever occurs first. i.e. some aircraft do not have a ‘loss of control’ Vmca. Note that the secondary effect of loosing directional control is roll; and usually very quickly at high alpha.
You may wish to reconsider your opinion of the aerodynamic knowledge of those pilots’s who took you for a ride.