Bookworm
So what do you do in an aircraft with de-ice that is "certified into light icing"? Does the de-icing suddenly stop working after an hour? If it can cope with the ice by use of the available equipment, is it "light" or "moderate"?
It is not just the ability of the boots to kick off ice or the prop heating to keep the props reasonably clear.
Ice will be accumulating all over the airframe not just the leading edges and props.
The airflow will be disrupted and the aircraft will also be carrying more weight.
The props even anti iced will not produce as much thrust.
Even keeping your boots clear you will note a drop off in IAS at cruise speed and a further drop as more ice accumulates on the airframe.
The stall speed will increase so your cruise speed decreases and your stall speed increases coming closer together.
On a light twin or single becuase the initial cruise speed isnt high the stall and cruise will get closer and closer.
So its not just about accumulating light ice and the deicing anti icing being able to cope with it but the continued accumulation on all the services not covered by anti ice or deice over longer periods or greater accumulations.
As the speed decays to maintain altitude the greater angle of attack and increased drag from that.
Also as the airflow descreases so does the friction from the airflow. As the angle of attack changes so does the point of ice accumulation on the lifting surfaces.
At that point I will let someone with greater knowledge of flight dynamics take over especially regarding ice accumulations
Pace