Preliminary report on serious aircraft incident
When intercepting the glide slope on the ILS-approach, with autopilot engaged, the crew experienced that the aircraft unintentionally pitched up. As a consequence of a very high nose attitude, airspeed dropped rapidly and aircraft came close to a stall.
The investigation has revealed that de-icing fluid could ingress into Tail Cone Compartment and freeze on in-put arms on the Power Control Units and jam normal elevator operations on Boeing 737s.