The pilot had previously noticed his aircraft “hunting” in pitch in FLC mode and had therefore decided to operate in VS mode during the climb. Whilst the use of VS mode in the climb is not prohibited by the AFM, it exposed the aircraft to the risk of entering a low-energy state during the climb. Without greater systems knowledge the pilot was unaware of the additional risks involved in the use of VS mode. Therefore he was unable to make an informed decision regarding this autoflight mode.
The autopilot will, in this mode, prioritise maintaining vertical speed over airspeed and pilot vigilance and intervention is required to avoid a low-speed condition. As the aircraft was operating at the edge of its climb performance envelope there was insufficient thrust to follow the selected climb profile. Over a period of 50 seconds up to the departure from controlled flight, the airspeed steadily decayed, by 10 kt.
I think the above from the accident report says it all and why VS should be used with absolute caution for climb JETS or LIGHT PISTON AIRCRAFT. Frankly at worst I think you are better climbing with manual trim either through the autopilot trim wheel or the main trim wheel as at least you are aware that you are controlling the aircraft. VS should only be used in descent and in climb with absolute caution and awareness
IAS mode will protect the aircraft. Down side is that the aircraft will hunt the speed again causing a pitching which is not great for the PAX so again MENTALLY manually fly which will at least mentally make you aware that you are controlling the climb rate rather than going to sleep thinking George has it in hand with VS use the trim or autopilot trim )))
Pace