Aircraft Controllability and Primary Flight Displays - A Human Factors Centered Approach

Knut Lande, General Manager/Flight Safety Advisor, LandAvia Ltd, Norway

Abstract

The global air accident rate has gradually decreased during the last decades. During the 1990’s Controlled Flight into Terrain (CFIT) and Approach and Landing Accidents (ALA) were the “biggest killers” in aviation. Continuous focus and efforts by the airlines, manufacturers, and not least Flight Safety Foundation, has succeeded in reducing this type of accidents. However, today the “biggest killer” has changed to be Loss of Control in the air type of accidents (LOC-I).

When analysing these accidents we find that lack of pilot knowledge and skills quite often are significant cause factors. It seems that the development in aviation technology and automation has made the aircraft so reliable and the flying so automated that the pilots are left out of the loop. During routine flight this works fine, but if unexpected situations are encountered the pilots are not capable of handling flight situations “old timers” would call “basic flying” situations.

The improvements in aeronautical technology might have had a negative effect on pilot edu- cation and training. Aircraft manufacturers and aviation authorities may also have contributed to this trend by advertising “low workload” cockpits and less required pilot training. Reduced focus on aerobatic flight and unusual attitude recovery training, combined with more automa- tion, may have influenced basic piloting skills.

Even though modern flight deck design is overall improved, there might have been some loss in instrument readability/interpretability during unexpected upset flight conditions and unusu- al attitude recovery. Using today’s technology, flight displays could be made more intuitive and easier to read in an unexpected and blurred flight situation. Also, by making flight control inceptors more intuitive, and thus improve tactile feedback cues, the pilots may be kept in the loop and be more prepared to take control in an unexpected situation.

Several LOC accidents are related to aircraft stall. This may be an indication that the state-of- the-art Primary Flight Displays (PFD) are not presenting the aircraft flight condition in a most intuitive way, and not presenting the pilot with a clear indication of Angle of Attack (AOA). Further, it may indicate that the pilot knowledge and skill in basic stall and upset recovery are insufficient.

An aircraft’s stability, control and handling qualities are very important to the pilot’s ability to control the aircraft. However, regardless of how ideal the aircraft’s handling qualities are, it is of limited value if the handling pilot becomes confused and disorientated during an unusual attitude (UA) or upset recovery (UR). Several of the recent accidents seem to be related to PFD’s and the pilots knowledge and training in interpreting their displays. It may be time for SETP to focus also on PFD’s in addition to aircraft handling qualities.