FD distraction danger during Go Around
Over the years, the situation has occurred where many operators enforce SOP training policies that require the flight director to be engaged during all stages of flight. In turn this can lead to not only automation dependence but automation addiction. FD were designed to be an aid and not the be all and end all of instrument flying.
A recent issue of Boeing Aero flight safety magazine discussed go around procedures and quoted in part, accident reports where the pilot(s) seriously mis-handled a normal IMC go-around with the result the aircraft crashed. A common theme was a night or IMC go-around. It was an interesting article where some discussion took place about the central role of the PFD with its ADI.
Before the advent of EFIS, the well loved (?) and long established flight instrument scan that covered all the main flight instruments gave the pilot `the big picture` The method and direction of scanning the flight instruments depended largely on pilot preference though there were pedants insisting there was only one way to scan and that was their way.
Nowadays the PFD has all the flight instruments crowded into a small space where scan rate is narrowed and not expanded. In central position and partially obscuring the "little aeroplane" is the flight director. When in use, the FD is primarily designed to concentrate the pilot's attention to juggling two needles into a tiny square barely 2mm in size. Fine if auto coupled to an automatic pilot; but requiring skill if manually flying.
The Boeing article on go-arounds discussed poor or disrupted pilot instrument scannings where pilots reacted very late to extreme negative attitude displays on both ADI's. These possibly led to somatogravic illusions that may be present during high acceleration or deceleration where a pilot has no clear visual reference.
Poor instrument scan is often characterised by marked pilot hasty over-controlling on the flight controls. Flight Director indications can become quite distracting as the needles can overshoot in response to jerky and inappropriate control responses.
There are pilots so brain-washed into blindly following the movements of FD indications (after all, who hasn't experienced at some time in their career the exhortations of an impatient simulator instructor shouting "Follow the bloody flight director") that they would never consider turning off a flight director even if its indications were confusing.
Boeing, in their various FCTM used to have the statement "If the FD is not to be followed, then switch it off." While that statement may arise the ire of some instructors who prefer their students to trouble-shoot the reason for a perceived FD problem rather than switch it off and sort it out at an appropriate time, there will be times when it is important to follow that Boeing advice. That includes measures to avoid the compulsion to chase FD indications during low altitude IMC go-around where clear unequivocal attitude information is vital. The first measure may be to switch the distraction (FD) off and return to basic instrument scan.
There is no shortage of evidence that severe over-controlling, coupled with poor instrument scan during an IMC go-around has been the cause of fatal accidents. Whether or not flight directors were involved is rarely mentioned in investigation reports. During simulator training, "chasing" the flight director is not uncommon during early training.
Chasing FD indications during the course of a low altitude high thrust go-around situation can lead to over-controlling. If that is happening, and before extreme attitudes are allowed to occur, the immediate action to return the aircraft to a normal go-around attitude, may well be to turn off the FD and use normal instrument flying procedures.
The FD is designed as an aid to instrument flying - but depending on circumstances, it can lead to a serious and unwanted distraction.