PILOT BEHAVIOR IN GLASS COCKPITS

For an improved situational awareness

 

By Captain Etienne Tarnowski

 

INTRODUCTION

 

The transition from conventional dial cockpits to glass cockpits has not caused any major turmoil in the pilots’ community, as compared to other evolutions such as a more extensive use of computers or of automation.

 

The glass cockpits, usually architectured around six display units, provide the pilot with a rationally well-ordered flight deck, with a neat and pleasant environment. Furthermore, the display units offer most of the information in a very comprehensive manner; they have the flexibility to display various data only when needed, and they have the capacity to accommodate more and more functionalities.

 

In other words, the glass cockpits have significantly modified the display of the main information and data required by the pilot to achieve his main tasks: operate, navigate and manage.

 

Such an evolution in the display of the flight data has necessarily major consequences in the way the pilot puts together his perception of the situation in flight. Hence, the pilot’s frame of mind and behavior must necessarily evolve as well, so as to get the proper situational awareness, when flying in such cockpits.

 

Let us now review the following issues:

1 Evolution of the instrumentation

2 Evolution of the pilot’s perception

3 Necessary evolution of the pilot’s behavior

 

1. EVOLUTION OF THE INSTRUMENTATION

As for all systems in the cockpit, the evolution of the flight instruments provided to the crew has been dictated by the evolution of pilots’ needs and by the continuous will to improve flight safety.

 

In the very early days of aviation there were almost no dials in the cockpits, just those needed to fly in VMC conditions; heading, speed, altitude indicators, and a couple of instruments for the engines.

But as aviation started to grow, the flight conditions expanded: faster, higher, further. The airplane became multi-engine powered, flying in all weather conditions.

 

As a consequence, pilots had to achieve new tasks to face and control many more factors which were materialized by a growing number of instruments and dials:

 

- instruments necessary to fly the aircraft

- instruments necessary to navigate

- instruments necessary to detect weather

- instruments necessary to control systems and engines

 

All these instruments did display one given parameter independently of the others; dials were adjacent one to another, and became very numerous.

In the mid fifties the number of airplanes started to grow. The commercial aviation became a blooming industry and travelling became part of our culture. So the air traffic constraints started to rise, as well as the economic pressures: the traffic flow rate had to increase, the aircraft had to come and land in more and more difficult conditions.

 

But during approximately three decades, the cockpit hardly changed; the initial information provided were still there, and additional ones had to be added.

 

As a consequence, in order not to overload the crew with too many additional dials and also in order to allow them to achieve more constraining tasks, some of the information have been synthesized or integrated as, for example:

 

- DRMI instead of standard bearing & heading

- EHSI instead of OBS or ZERO READERS

- FAST/SLOW indication on ADI

- Flight Director ...

First ADF indicators	First integrated ADF/VOR indicators

Then, in the early eighties, the manufacturers introduced cathode ray tubes driven by symbol generator units and data management computers. The CRTs provided a tremendous flexibility in the way to display information to the crew, to rearrange and to tidy the instrument panels which were overcrowded.

 

Two solutions were contemplated at that time:

 

· The first solution merely consisted in copying the old dials into the CRT; I will not expand on this solution which calls up for new technology without any real operational benefit behind it!

 

· The second solution, adopted by Airbus Industrie from the start, consisted in taking benefit out of the CRTs in order to rationally rearrange the great amount of data required for the crew, in order to take benefit of new computers, such as FMS, or TCAS, and in order to properly concentrate the information provided by the aircraft systems which have to be managed by the pilot.

 

The operational goals achieved by the Airbus solution can be summarized as follows:

- improve the pilot’s situational awareness

- allow a safe and efficient 2 crew member operation

These goals have actually been reached from day one because:

- the quality of the information has been improved: more reliable, more accurate,

- the content of the information has been optimized: more complete (speed scale), more synthetic (FPV, wind on ND ...), shown when needed,

- the location of the information has been reviewed, keeping up with the basic natural information layout (FMA, S/D arrangement),

- the format of the information has been rationalized: more comprehensive (systems synoptic), more realistic (navigation display)

 

                         Primary Flight Display              Navigation Display

 

2. EVOLUTION OF THE PILOT’S PERCEPTION

 

The evolution in the instrumentation actually dictates the evolution of the pilot’s perception of the situation. Two phases may be outlined in this evolution:

 

· Conventional dial phase (or pre-glass cockpit)

· Glass cockpit phase

 

Indeed the transition from one technology to the other has not so much modified the contents of the data provided to the pilot, rather than the way to present it. Hence, this has changed the mental perception process required from the pilot.

 

Conventional dial phase

 

With the conventional dials the pilot used to scan the main instrument panel in order to pick up each individual piece of information and to make a mental synthesis, so as to rebuild the situation in his mind. Obviously, when some parameters got synthesized, this task was easier for him.

 

Some examples will illustrate this statement:

Materialize the aircraft position:

 

- Initially, by watching the heading on the heading dial and the bearing on the bearing dial, the pilot could work out the radial

HEADING ± BEARING + 180° ® RADIAL

 

Then, some instruments allowed the pilot to rotate the heading dial in order to

select the aircraft heading and thus to get immediately the radial reading under the pointers.

 

Finally the DRMI did this function automatically.

DRMI ® RADIAL

 

But the problem was not yet over; out of the radial, the pilot had to determine the

aircraft position! Quite often he had to determine the aircraft position versus a given radial, and then to intercept and track that radial.

 

Initially he did it by a mental process; subsequently the EHSI did help him significantly.

EHSI

Fly a stabilized approach:

 

In order to do so the pilot had to mentally process several parameters so as to properly fly the approach, more specifically in varying wind conditions.

 

Laterally he had to work the drift (X) so as to get an assessment of the heading

required to fly the approach course or track:

HDG + TRK ± X

 

Vertically he had to work out the average rate of descent (V/S) to fly from FAF down to MDA and be properly positioned to continue the approach and to land, if visual:

IAS + ALT ® TAS TAS + WIND ® G/S

G/S + DIST ® TIME TIME + ALT ® V/S

 

This method was quite widely used in some areas of the world, but disregarded in other areas where operators did favor step down descents to MDA, which is a method increasing the risks of CFIT.

 

Thus, the conventional dials forced the pilot to build up himself his own perception of the situation; he did so by making a synthesis of various independent data displayed on the main instrument panel, and by computing essential parameters required to fly a given trajectory.

 

This mental process had advantages and disadvantages:

 

Advantages:

 

- The situational awareness was created by the pilot himself

- The mental process was an active process from the pilot

- The mental process was based on raw data

 

Disadvantages:

 

- The mental process never became natural/intuitive to some pilots,

- The mental process required a high intellectual workload,

- If an error was made, it was difficult to detect because buried in the pilot’s mind,

- The process allowed for computation errors,

- The process allowed for interpretation errors,

 

The glass cockpit phase

 

With the latest display units, the pilot’s perception has been significantly modified for the following reasons:

 

- The information are displayed and properly laid out in a clearly limited space.

- The information format is comprehensive, realistic and salient when required.

- Information of the same nature are provided along the same scale.

- Whenever feasible, properly synthesized information is displayed.

 

This obviously modifies the instrument scanning requirements and methods; furthermore, the mental process necessary to get a full assessment of the situation is by far more straight forward.

 

Let us review the previous examples:

 

Materialize the aircraft position

 

- Is immediate on the ND.

The position of the aircraft versus a beacon, an airfield, a radial, is obtained by direct reading of the ND.

 

Fly a stabilized approach

 

- Laterally: the pilot gets an immediate reading of the aircraft track on the heading scales of the PFD and ND.

 

In crosswind situations, the pilot has merely to fly the track index in view of the TRK selected target.

 

- Vertically: the pilot may select the Flight Path Vector (FPV). Once overhead the FAF, he will merely fly the FPV to the intended approach FPA and to the selected TRK target.

PFD: FPV selected for Non Precision Approach

 

The data which are today provided on display units are by far more accurate, more complete and more realistic than on conventional dials. The realism of the pictures is such, that the pilot does not need a lot of complex mental process to update his situational awareness: the ND linked to the FMS gives all data required to locate the aircraft by mere reading.

 

The S/D pages of the ECAM materialize the status of a given system in normal or abnormal situations by direct reading. Furthermore, to assist the pilot in his monitoring task, the EFIS and ECAM provide him with trends or phase advanced data as, for example:

 

- acceleration/deceleration (speed trend) on PFD SPD scale?

- V/S indicator adjacent to the altitude indicator,

- armed modes on FMA,

- intercept trajectories when possible with NAV armed, on the ND,

- advisory mode on the ECAM,

- monitoring messages of the ECAM (T/O configuration, baro-setting, discrepancy

messages, ...).

 

The purpose of these data is also to assist the pilot to keep ahead of the aircraft, so as to always be in a position to control it.

Example of Trend/Phase advanced data on PFD

 

 

Thus, the glass cockpits provide the pilot with a direct perception of the situation. They achieve for the pilot a part of his scanning scheme, and a synthesis of many information gathered from numerous peripherals, so as to process a realistic picture of the situation. Furthermore, they allow to get a more complete and a more flexible display: only the information which are needed are provided, which allows to select additional data in some flight phases when required (TCAS, EGPWS, ...).

 

Advantages:

 

- More realistic, more complete displays

- Pilot’s mental is available for other tasks such as operate and manage

- Significantly enhanced situational awareness

- Pilot flies more ahead of the aircraft

 

Disadvantages:

 

- All the process is achieved according to built in computer logic

- This favors complacency

 

Finally, the display units do improve so much the realism of the pictures, that these should only be provided if the data are processed with a high level of accuracy and reasonableness. Hence, the manufacturers have to ensure that these levels are actually reached and that a proper coherence is achieved between various functionalities.

 

Let us consider an example, the EGPWS:

 

The EGPWS materializes on the ND the obstacles in the vicinity of the aircraft position and the severity of their threat considering the aircraft performance. The colored areas are most realistic (as a radar image is), and indicate to the pilot whether its intended trajectory is safe or not.

 

ND: EGPWS image

 

The behavior of the crew will be similar to his behavior when facing a radar image (map or weather) or a TCAS TA or RA. In other words, the crew will assume that the relative position between the aircraft symbol and the colored area is exact! This is always true in case of radar or TCAS; this is true for EGPWS only if the FMS computed position is correct. This explains why the EGPWS image is provided only, if FMS accuracy is high, or with GPS.

 

 

3. Evolution of the pilot’s behavior in glass cockpits

 

In glass cockpits the situational awareness of the pilot is therefore continuously updated by very realistic displays, by many synthetic information which he can directly use without any additional process. In other words, in many cases, the pilot has merely to watch the picture in order to get an assessment of the situation.

 

Yet, the experience demonstrates that, in certain circumstances, some data are missed or are not seen by the crew, that misinterpretation of parameters causes misjudgment of the situation and that some parameters are quite misunderstood; furthermore, the realism of the picture is such, that the display becomes attractive and compelling; this somehow reduces the alertness state of mind of the pilot ("It is so nice, it can’t be wrong!").

 

The introduction of glass cockpits necessarily modifies the pilot’s behavior in the cockpit, as compared to what it was with conventional dials.

 

The following guidelines indicate the benchmarks of this behavior:

 

3.1. Get a proper understanding of the display rules and of the main parameters

 

The pictures provided on the CRTs have been designed according to display rules which should be familiar to the crew: color coding, warning inhibition etc...

 

Let us consider the specific rule which states: "On the ND, the green solid line is the presently flown and predicted aircraft trajectory, assuming the current autopilot active mode".

If such a rule is understood, in case NAV mode is armed, the pilot will immediately detect whether the track line will or will not actively intercept the FPLN, by merely watching the ND

 

Intercept not possible                 Intercept possible 

On the other hand, some information is quite synthetical or has a precise meaning. The pilot must know and understand the meaning of the information. For example, it is still frequent today for some pilots to assume that the FPV indicates the flight path angle in the vertical plane and ... the heading (!) in the horizontal plane!

 

Such a misunderstanding causes the pilot to feel most uncomfortable in crosswind situations, when he sees the FPV symbol not centered on the PFD!

 

Furthermore, he does not take benefit out of the alignment between the FPV, the track index and the track targets located on the heading scale and on the horizon line, to follow a selected course.

 

Finally, such a misunderstanding destroys the "intuitive" awareness the pilot should get from the FPV display on the PFD: when the FPV is pushed to the right of the PFD, this means that the aircraft itself drifts to the right because of the wind. Thus, when reaching minima, the pilot intuitively looks to the right through the windscreen to get the view of the runway!

 

 

 

FPV: intuitive cross wind assessment

 

3.2. Adapt the PFD scanning scheme to the level of automation selected

 

On a conventional aircraft the scanning scheme is a repetitive process which has to be systematic because the information are wide spread on the main instrument panel. As a consequence, it is quasi impossible to grasp several data at a time. Furthermore, some data associated to automatic systems, such as AP/FD or ATS, do not appear on the main instrument panel itself but on the glareshield or on a specific unit.

 

In all circumstances the scanning scheme is as follows and has to be completed by other information being picked up throughout the cockpit:

Typical Scanning Scheme with Basic T

 

On the glass cockpit the scanning obviously still applies, but it is easier, and more complete. Indeed:

 

the speed scale carries the available flight envelope, the maneuvering speeds, the

target speed, the acceleration, in addition to current speed

 

the altitude scale carries the target altitude, the differentiation in between flight

level and baro-setting altitude, the MDA in addition to current altitude

 

the baro-setting/standard carries a message linked to transition altitude by the

pulsing of QNH or STD pending upon situation

 

the heading scale carries the target heading, the ILS course and the track symbol

in addition to current heading

 

- the upper part of the PFD carries the FMA

 

all these data are displayed most clearly; furthermore, the nearness of the

information and the benefits of color and format display rules allows to grasp several data at a time.

 

 

But the scanning must follow the following rules:

 

Scanning depends upon the flying references selected:

 

- if altitude (HDG – V/S) is selected, altitude and heading have to be scanned,

- if flight path vector (TRK, FPA) is selected, FPV and track have to be scanned.

 

Scanning depends on the level of automation selected

 

- with AP or FD or ATHR, the FMA as well as the guidance targets must be periodically monitored.

 

 

3.3. Monitor and use the ND according to FMS rules

 

The ND linked to the FMS has in most cases solved the orientation problems of the pilot.

 

"In most cases" means that some precautions have to be taken in order to get the best out of it:

 

- Ensure that the FMS accuracy is satisfactory using raw data. If satisfactory the pilot may use the ARC and ROSE NAV display modes.

 

- Ensure that the FMS F PLN is correct: hence, monitor that the TO waypoint on ND is the most probable one.

 

- Properly adjust the ND range and mode to the flight progress.

 

Select the appropriate additional information on EFIS Ctle panel as a function of f

light progress: en route, select airports; in approach, select constraints etc ...

 

In case of any doubt in navigation accuracy, revert to raw data and select ROSE

VOR (ILS).

 

The ND ARC and ROSE NAV pictures carry a lot of very valuable information displayed in a very realistic format to the crew. The realism is such that crews may be tempted to lose their critical mind, which will cause them to miss a map shift for example.

But a proper monitoring of the ND prevents such a temptation, and ensures a safe perception of the situation.

 

 

ND: monitoring rules

 

3.4. Adopt a positive attitude during flight progress

 

All pilots know that they have to fly AHEAD of the aircraft; if they do so, they can readily react to severe situations and on the other hand, they can operate the aircraft efficiently.

 

Trend data and advanced phase information are provided to the pilot to assist him for that purpose; but the pilot is the one who has to stay ahead, to fight against any form of complacency and to fully manage the flight, that is:

 

monitor the automatisms with the right cues: e.g. ATHR, with speed / speed trend

and with N1 (EPR) gauge

 

periodically monitor the FMS accuracy and take appropriate action if a cross check

is negative

 

- periodically monitor the major ECAM S/D pages (Eng, Bleed, Elec, Hyd, Fuel, Fit Ctles ...) during flight

 

- periodically monitor Fuel (XTRA, FU, FOB ...)

 

- periodically update the SEC F.PLN for diversion purposes

 

- in case of caution/warning, review the ECAM S/D to analyze the situation prior to acting.

 

Such a positive attitude will allow the pilot to properly anticipate and to continuously keep in mind these two essential questions:

 

What do I want the aircraft to fly now ?

What do I want the aircraft to fly next ?

 

 

Conclusion

 

VMC conditions offer the best possible perception of the world picture pilots may obviously dream of! This explains why they react most intuitively and naturally to any kind of circumstances, in such conditions.

 

The major design objective of glass cockpits is to provide the crew with the most realistic picture of the in flight situation and with the most comprehensive displays of the aircraft systems: indeed, realism and comprehension are the two key elements necessary for the pilot to properly update his situational awareness.

 

Such design objectives were not part of the conventional dial cockpits, which could only offer the juxtaposition of many dials displaying individual parameters, on the main instrument panel.

 

On glass cockpits, all the experience and methods gained by training and flying on conventional cockpit aircraft, are obviously preserved.

 

But the pilot’s state of mind and behavior are somehow modified: indeed, the realism and comprehensiveness of the displays must be compensated by an active and positive attitude from the crew, leaving no space to complacency, and by a systematic reference to basic airmanship and common sense, whenever a doubt might arise.