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CARE INO III

3D IN 2D PLANAR DISPLAY PROJECT

D4-2: COCKPIT INFORMATION AND SPATIAL TEMPORAL

NEEDS (LOT NO. 3, WP 4)

Reference : Edition 1 Effective Date 06/10/08

Authors Organisation Signature

William Wong Middlesex University

Stephen Gaukrodger Middlesex University

Fan Han Middlesex University

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DOCUMENT CONTROL

Copyright notice

© 2008 European Organisation for the Safety of Air Navigation (EUROCONTROL). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of EUROCONTROL.

Edition history

Edition

Nº

Effective date

or status

Author(s) Reason

1 06/10/2008 Wong, Gaukrodger,

Han

Deliverable due.

Acknowledgements

Name Location

Other members of the project team

Paola Amaldi Middlesex University

Bob Fields Middlesex University

Martin Loomes Middlesex University

Ifan Shepherd Middlesex University

Richard Aked Space Applications Services

Luigi Mazzuchelli NEXT Sistemi Ingeneria

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Table of Contents

1.  INTRODUCTION ................................................................................................. 5 

2.  METHDOLOGY .................................................................................................. 9 

2.1  Cognitive Task Analysis: The Critical Decision Method .............................. 9 2.2  Interview Procedure .................................................................................. 10 2.3  Data Analysis ............................................................................................ 11 

3.  RESULTS AND ANALYSIS .............................................................................. 13 

3.1  Bucharest thunderstorm incident (P1, 15 Sep 2008 1000h) ..................... 13 3.1.1  Incident Summary .................................................................................... 13

3.1.2  Decision Timeline .................................................................................... 13 

3.1.3  Decision Table ......................................................................................... 13 

3.2  Engine vibration incident (P2, 15 Sep 2008 1330h) .................................. 18 3.2.1  Incident Summary .................................................................................... 18

3.2.2  Decision Timeline .................................................................................... 13 

3.2.3  Decision Table ......................................................................................... 20 

3.3  Oil leak incident (P3, 17 Sep 2008 1030h) ............................................... 24 3.3.1  Incident Summary .................................................................................... 23

3.3.2  Decision Timeline .................................................................................... 26 

3.3.3  Decision Table ......................................................................................... 27 

3.4  Hydraulic failure incident (P4, 17 Sep 2008 1330h) .................................. 33 3.4.1  Incident Summary .................................................................................... 33

3.4.2  Decision Timeline .................................................................................... 34 

3.4.3  Decision Table ......................................................................................... 35 

3.5  SFO Energy Profile Incident (P4, 17 Sep 2008 1330h) ............................ 36 3.5.1  Incident Summary .................................................................................... 36

3.5.2  Decision Timeline .................................................................................... 37 

3.5.3  Decision Table ......................................................................................... 38 

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4.  KEY FINDINGS ................................................................................................. 39 

4.1  Energy profile management ...................................................................... 39 4.2  Track miles ............................................................................................... 39 4.3  Fly by parameters and the 3 times table heuristic ..................................... 41 4.4  The ‘green arc’ .......................................................................................... 42 4.5  Awareness of surrounding traffic .............................................................. 42 4.6  Flight Management System does not work for the pilots .......................... 43 

5.  DISCUSSIONS & CONCLUSIONS .................................................................. 44 

6.  REFERENCES .................................................................................................. 46 

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1. INTRODUCTION

SESAR addresses the needs of the future European ATM system with a number of

advanced operational concepts, such as the Business Reference Trajectories, and

technology infrastructures such as System Wide Information Management, for the guidance

and control of aircraft. The concept is designed to enhance the safety and efficiency of the

airspace system, and especially to cope with the explosive growth of air traffic and the

projected continued expansion over the next decades. As various elements of the SESAR

concept become implemented, the future European ATM system will be transformed from a

centralized command-and-control system between pilots and air traffic controllers, to a

distributed system that allows pilots to choose their own route and file a flight plan that

follows the most efficient and economical route. Such a development will relax many of

today’s flight constraints. However, the economic benefit of increased traffic flow may come

at the risk of more potential air traffic conflicts or incidents. This potential problem prompts

the re-examination of current and conventional technologies and methodologies used for

managing the European airspace system, with an emphasis on the how to achieve efficient

and effective management of aircraft from the perspective of the pilot.

In this report, we discuss the findings from the cognitive task analysis of four pilots, as they

recounted five personally experienced and memorable flight incidents in detail, and

addressed the insight we gained from these interviews. We used the Critical Decision

Method, an in-depth interview method used to identify and elicit expertise invoked during

critical incidents the pilots had personally experienced during the course of their work

(Wong, 2006).

In these instances of differing nature and level of seriousness, the pilots have had to deal

with and resolve the situation not just at some fixed instant in 3D space, but often over a

lengthy period of time, in some cases, up to the entire duration of the flight. It emerged that

pilots frequently perform quick mental calculations in order to predict the outcome of some

future event, e.g. to project ahead the aircraft’s future 3D location, how far aircraft the aircraft

will land from the end of the runway (by considering heading, speed and altitude), as well as

to assess the likelihood of any conflicts or impending danger.

By comparing how pilots resolve conflicts in terms of his or her ability to visualize spatial

patterns and to mentally manipulate them over a time-ordered sequence of spatial

transformations, we have gained a deeper understanding of the process of pilot-generated

conflict resolution based on space-temporal reasoning. This offers a venue to expand the

work on human temporal awareness from available cockpit information, and allows

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comparisons to be made between the differences in pilot performance and biases in their

different task environments. This analysis provides an understanding of pilots’ temporal

awareness that will enable prediction of their performance (which is influenced by subjective

workload) under various operational demands, thus providing a scientific basis for further

development of novel human-machine systems that could function under SESAR.

There is a growing interest in understanding the process by which pilots maintain awareness

of the many complex and dynamic events of the world and systems around him at any point

in time, and how this information is subsequently used to guide him through future actions.

Being able to perceive and comprehend the 3D space in which he is travelling in; to then

predict future traffic situations or aircraft locations by projecting current trends; and then to

allow for any other demands that may arise within that 3D space, such as weather changes,

over different time bands (Burns & Baxter, 2006); is essential to maintaining good situational

awareness (Endsley & Smolensky, 1998). Pilots begin by assessing the current situation –

urgency, severity etc, then anticipating all possible future scenarios that may occur in some

appropriate time band, before going on to formulate and develop plans to deal with any such

scenarios should they arise.

Various cognitive processes are involved in this interaction with complex, dynamic, possibly

unstable, environments. Such intense environments present the operator with multiple tasks

that must be monitored, prioritized, and managed, often simultaneously. It is conjectured that

in the future the role of pilots in cockpits would be one of a “decision-maker”: who is required

to act according to his understanding of the situation, and the source of error is in the

accuracy and completeness of his knowledge base, or in the process of reaching a decision.

Figure 1. Requirements, concepts, and architecture (Boeing Commercial Airplane Group(1997))

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Figure 1 summarizes the concept proposed by Boeing, of the preliminary design process for

the development of air traffic management systems and components. The approach consists

of development of traffic demand scenarios, performance of a mission analysis based on

evaluating high level system capacity, safety and efficiency objectives, allocation of

operational requirements to subsystem technical requirements, and evaluation of

technologies, human factors, and economic factors in defining system transitions from the

current operating state to the future concept.

Current cockpit displays of traffic information provide airspace information to the pilot in such

a way that allows the pilot to understand his location relative to the environment and to

positions of potential dangers. This series of cognitive task analysis interviews have enabled

the identification and development of new concepts that would allow pilots to carry out

suitable manoeuvres with both of global situation awareness and local situation awareness

over a span of time.

A primary focus of this report is on the discussion of the factors that influence the

presentation of energy-related information to the crew. Based on our interviews with the

pilots, it was found that energy profile management was a common source of concern. Most

of the accidents that occur in air traffic management often concern the landing phase as

indicated by accident statistics. These include heavy landings, rushed approaches and

runway overruns. It was reported during the interviews that good energy management would

provide more accurate information on which to base actions, which should lead to more

appropriate and timely responses that could minimise these events.

However, due to the large number of variables involved, e.g. wind, aircraft weight, aircraft

speed and configuration, altitude, and rate of energy loss, it is very difficult for a pilot to

achieve the final approach gate with the right amount of energy. The pilots report using a “3

times table” heuristic to estimate the distance they need to track in order to bring the aircraft

to within the correct “energy profile” (speed, distance, altitude) associated with landing the

plane. This heuristic lacks precision and requires constant computation during approach, a

time when pilots are already busy.

Accordingly much more work is yet to be done on the problem of effective energy

management, with the goal of creating tools that pilots of any level of experience can use. By

allowing the controller to communicate a five dimensional target value (x, y, z, t, and Ek), the

pilot can then choose an appropriate track route to fly in order to reach the goal. The

provision of aircraft instrumentation to monitor aircraft energy levels and assess energy

status could enhance crew decision-making, which in turn, could lead to improvements in

safety. Finally, these calculations could be made available to controllers to tell them when a

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particular request is impossible. In the future, it would be highly desirable to have an intuitive

display to show whether, with some particular aim in mind, the current energy level of an

aircraft is too high or too low, thus allowing pilots to maintain the correct profile all the way

until the final approach.

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2. METHDOLOGY

This study was conducted among four experienced pilots and pilot trainers at the British

Airways Flight Training Centre, near London Heathrow Airport. The study involved the use

of cognitive task analysis techniques to identify and elicit pilot expertise used during flight

control. In particular, we used the Critical Decision Method to focus our analysis on

understanding the nature of the pilots’ spatial-temporal temporal expertise within the context

of SESAR operational concepts such as the 4D trajectories (Reference Business

Trajectories). The next section will briefly explain what is a cognitive task analysis, and in

particular what is the Critical Decision Method as used in this study.

2.1 Cognitive Task Analysis: The Critical Decision Method

A cognitive task analysis (CTA), unlike the more traditional task analysis used to study

physical human activity, is the study of non-observable behaviours and the reasoning behind

them. Typically, through a CTA, we identify the way decisions are made, the information

used, manipulated and combined, and how such information were considered during those

decisions, issues or cues attended to, their relationships and priorities that guide decisions,

achievement goals, intentions, their awareness, and the structure of the cognitive work they

perform. This often involves the identification of functional relationships of the cognitive work

in the operational domain in such a way that these can be used to guide designs that would

support the demands of the cognitive work.

One of the many CTA techniques is known as the Critical Decision Method, or CDM

(Crandall & Getchell-Reiter, 1993; Crandall, Klein, & Hoffman, 2006; Wong, 2006). It is an

open-ended, in-depth interview technique that is based on retrospective protocol analysis. It

requires the person being interview to think back to, or retrospect on, a particularly

memorable incident that they had personally experienced during the course of their work.

During a CDM interview, the interviewee would be probed about this incident in a systematic

yet open-ended way in order to identify emergent and un-anticipated themes, rather than to

ask about pre-defined issues that could be coloured by the interviewers’ per-conceived

understanding of the nature of the expertise being studied. The latter would introduce

problems of interviewer bias and limit the discovery of the un-anticipated. These

retrospective reflections can then be systematically analysed in the process of protocol

analysis to reveal relationships and issues across the group of people interviewed.

It should be noted that techniques such as the CDM were deliberately designed to be

exploratory (to find out what is there), rather than confirmatory (to confirm and measure the

occurrence of a phenomenon). Such studies provide very rich and detailed qualitative

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accounts of the variety of events and circumstances from which we can extract insights

about the nature of human expertise.

The purpose of such analysis is not to discover standard practice and procedures that could

be readily referred to in operator manuals and embedded in equipment procedures, although

such findings would quite naturally emerge from the analysis, but instead, to identify decision

strategies, expertise and other cognitive behaviours that are invoked during out-of-the-norm

and demanding situations.

In the case of the CDM, the nature of critical incidents are such that during those incidents, it

often demands the interviewees operate at the limits of their abilities. The findings from

these studies would then help us discover the nature of expertise and how that expertise

was employed during the variety of demanding situations that a system (human and

technology) must be able to cope with. This is a simplified explanation of the application of

the law governing the design of complex systems, the Law of Requisite Variety (Ashby,

1958).

2.2 Interview Procedure

In this section we describe the procedure we used during the study. Each CDM interview

lasted between one and a half to two hours long. The interviews were conducted in a private

office-type environment. The interviews were audio recorded. Each interview comprised the

following sets of activities:

a. A briefing on the main SESAR ideas and how we will use it as a context for the

development of cockpit information displays later in the project,

b. Identification and selection of suitable incidents to retrospect on,

c. Charting of the decision time line which can then be used as a prop for deeper

analysis of key decision points during the incident,

d. Progressive deepening where identified key decision points are probed in further

detail,

e. What-ifs analysis, where the interviewee is asked to reflect on other aspects of

expertise.

Prior to the start of each interview, each interviewee was first presented with a brief

explanation of the key operational concepts of SESAR such as the Reference Business

Trajectory (4D Trajectory), Controlled Time of Arrival, and the SWIM (System Wide

Information Management) network-centric information architecture, and the lattice concept.

In addition, we provided a demonstration of a number of novel display and interaction design

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concepts we were working on. These included the concept prototypes such as the AR-in-

your-hand and reach-in-and-grab concept, the stack manager in the Wall’s display with the

altitude ruler. This was intended to be used to set the context of how different we were

anticipating the future ATM environment was going to be.

We then spent some time selecting demanding and memorable incidents that the pilots have

personally experienced. If they were not personally experienced, there would be no

experience to retrospect on. The incidents needed to present a degree of challenge that is

outside scope of normal flight control.

Once the incident had been selected, the interviewee is asked to describe the incident. Each

key event and decision point is recorded on a piece of sticky paper (Post-It pad). These

events and decision points are then organised along a timeline in the broad sequence in

which they occurred.

The interviewees are then progressively probed more deeply at key decision points to

identify the cues attended to, what information was used, how the information was

considered, how was the problem resolved, what actions were taken, what factors formed

part of their analysis and assessment at that time, the goals they were trying to achieve, and

the purpose of their actions.

Following this detailed analysis of their decisions and actions, we then turned our attention to

the what-ifs. For example, what-if you were supervising someone of less experience, what

kinds of mistakes do you think you would likely observe? What-if you had the chance to do

this again, what would you do differently? What advice would you give a less experienced

person starting of the job and having to experience such a situation? The objective here is to

provide an alternative perspective for retrospecting on the nature of their expertise.

2.3 Data Analysis

Once the data had been collected, the next stage is to analyse the data and to make sense

of it. For this, we were guided by the Emergent Themes Analysis method (Wong, 2004). This

is done systematically by firstly creating the decision chart that shows the sequence of

events, decision points and how each key decision is progressively deepened to reveal the

factors considered, how considered, cues attended to, assessments made and so on. Then

next step is to use the decision table to systematically extract the different aspects of the key

decisions. Using the goals of the different decisions, we can then attempt to collate, compare

and discover how decisions are made across the different incidents. In this way, this data

analysis approach provides us with a method for systematically discovering insights about

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the decision making processes and spatial-temporal reasoning expertise invoked during

flight control.

The results of this analysis is reported in the next section, although for brevity, the detailed

process of this analysis will not be discussed in this report.

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3. RESULTS AND ANALYSIS

3.1 Bucharest thunderstorm incident (P1, 15 Sep 2008 1000h)

3.1.1 Incident Summary

1. This incident describes the events and decisions made by the pilots in responding to a

route change requested by Bucharest ATC in order to avoid flying into thunderstorm

clouds at eastern end of runway. basis

2. The flight was planned to land at Bucharest Airport in a westerly direction. This would

require the flight to fly abeam the runway and come around the eastern end, landing into

the wind on Runway 26. When the flight was about 80 nm away, Bucharest ATC

requested that, due to thunder clouds at the eastern end of runway, the flight alter its

route to approach and land directly on Runway 08, with a slight 5kts tailwind. See Figure

2. (NB: the details are simplified, e.g. Bucharest Airport has two runways, 08L/26R and

08R/26L).

Figure 2. Schematic of the situation

3. The requested approach change requires that the aircraft fly a shorter distance to land.

This would reduce the tracked miles from 105nm to 80nm. This means that the aircraft

will now need to lose the same amount of energy (momentum) in a shorter distance. If

the aircraft approached too fast, it may have overshot and needed to go around, or if it

landed at too high a speed, the severe braking could have generated enough heat to

cause the aircraft’s tyres to explode.

4. The pilot reported using a “3 times table” heuristic to estimate the distance they need to

track (actually travel) in order to bring the aircraft within the “energy profile” (speed,

distance, altitude) required for landing the plane. In this incident, cruising at 30,000ft, the

aircraft would need a tracked miles of 90 nm (30 x 3) to comfortably reach the final

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landing gate (1000 ft, 3.3 nm from end of runway, at 140 kt landing speed). This 90 nm is

greater than the 80 nm available for the easterly approach and landing.

5. There are two key aspects to this incident: (i) to assess whether this is feasible, and (ii)

to then carefully manage the ‘energy profile’ during descent. The energy profile is a way

of describing how high and how fast an aircraft is approaching a target point in space

and time, e.g. the landing gate. The objective is to ensure that the aircraft does not arrive

“too high, and too fast”.

6. The aircraft landed successfully.

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3.1.2 Decision Timeline

Bucharest thunderstorm incident (P1, 15 Sep 2008 1000h) 80 nm west of

Bucharest Airport

ATC request that flight approaches directly using Rwy 08 instead of Rwy 26.

Can I do it?

Can I brief the other pilot in time?

Feasible? Can I slow down enough to approach runway in the shorter

tracked miles? ATC does not know or not able to tell.

Use the “3 times table” heuristic to estimate if

this is feasible.

Experience suggests need to get lower: for the range and speed

TCAS - wasn’t clear as Bucharest is not a busy airport, so not

many flights to form a pattern.

A/c currently at 33-34000ft, 80 nm. The requested approach would reduce track miles by 15-20 nm,

requiring greater energy loss.

Can I land with the tail wind? 5 kts

Is the runway wet or dry? Affects landing

speed.

How will I taxy to parking gate?

Used TCAS to see what other aircraft

are doing; what patterns they are in

to assess ATC overall intentions.

Will cabin crew have enough time to prepare

for landing?

Enough time?

Can I re-program the new approach into the computer aids in time?

Check altitude constantly, every 5000ft

Check ‘distance to go’

10-12 nm 180 kts tail wind 5 kts

3.3 nm 1000 ft 140 kts

Lock on to ILS localiser beam

Check aircraft is stable

GATE Final checks:

Speed? Energy? Stable?

Cabin good?

Evaluate energy profile - repeat constantly

Work out distance to go (3 times table heuristic) to estimate for particular aircraft type, how high and how fast it should be at a point on the trajectory

Land the aircraft

Don’t want to be ‘high’ on the profile, esp at

the arrival gate.

Slow up for approach.

Check speed brakes, thrust levers, slats

and flaps.

Respond to ATC: accept the request (Yes, I can.)

“set up the box” Flight Management

Computer for Rwy 08.

Tune ILS for Rwy 08.

Check distance for wet runway. Refer to paper

chart for the info.

Consider contingencies:

Are we likely to go into the thunderstorm clouds?

Do we need to revise our route?

Do we have enough fuel?

What if we need to fly a go-around?

15 nm 4500 ft

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3.1.3 Decision Table

Bucharest thunderstorm incident (P1, 15 Sep 2008 1000h)

Decision Point Considerations Cues used and

sources How cue used Actions Goals

Can I do it?

(situation assessment)

Is it feasible? Current cruise speed at 33-34000 ft

Current altitude (altimeter)

Current distance from the airport (distance to go indicator)

Use the “3 times table” heuristic to estimate if there are enough track miles from current position (33-34000 ft, 80 nm) to the landing / approach gate (1000 ft, 3.3 nm)

Needed to get lower To ensure that the aeroplane does not come in “too high and too fast”. (energy management)

What are other aircraft doing around the airport?

TCAS display to see what other aircraft are doing – aircraft pattern around the airport, crossing traffic in the general approach area.

TCAS display does not provide aircraft direction nor track history, only current location and whether they are climbing or descending in relation to ownship.

To anticipate approach direction, likely difficulties, areas or routes to avoid.

Use TCAS to see where other aircraft are and what ‘pattern’ they are in (e.g. aircraft lined up for finals, where aicraft are approaching from, etc).

To be aware of situation in order to anticipate courses of action, to minimise conflict.

Landing factors 5 kts tailwind at runway Can I land with the 5 knts tail wind?

Is the runway wet or dry? (later ATC report)

Wet runways need more stopping distance than a dry runway

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How will I taxy to the parking gate?

Landing speeds and at which taxyway likely to get off the runway?

Enough time? Will cabin crew have enough time to prepare for landing? – comms with cabin crew lead.

Part of situation assessment

Can I brief the other pilot in time?

Part of situation assessment

Can I re-program the new approach into the computer aids in time?

Part of situation assessment

Respond to ATC, “Yes, I can”.

Set up the FMS for Rwy 08

Tuned ILS for Rwy 08

Checked distance for wet runway

To prepare for landing

Consider contingencies:

- what if we need to go-around?

- Are we likely to go into the thunderstorm clouds?

- Do we need to revise our route?

- Do we have enough fuel?

Evaluate energy profile Check altitude every 5000’

Check ‘distance to go’

Check speed

Work out track miles. To ensure that aircraft does not arrive too high or too fast at the approach and final gates.

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3.2 Engine vibration incident (P2, 15 Sep 2008 1330h)

3.2.1 Incident Summary

1. In approximately 1991, during a flight from London Gatwick airport to Lagos on a 747

classic – 3 crew, 4-engine aircraft – during intermediate cruise due south, passing near

Paris, an engine vibration problem was discovered in engine number 4. Engine 4 was

then shut down according to standard procedures. The aircraft was turned around back

towards London.

2. About 5 minutes later a vibration problem was discovered on a second engine and it too,

was shut down. The failure of two engines within such a short space of time is a very

rare occurrence, and suggested a potentially severe underlying problem. Now running on

two engines, Mayday was declared and a decision was made to divert from initial route

and plan for landing at an airport near/in Paris.

3. In terms of distance Paris Orly was the closest airport, but Paris Charles de Gaulle was

chosen instead due to pilot familiarity with terrain and runways etc. It was noted that it

was possible to arrive at Charles de Gaulle by gliding – using idle thrust had all four

engines failed. This provided back-up.

4. At the time, one pilot was briefing ATC on the situation and requesting priority landing,

while the other was engaged in flying the aircraft. Cabin crew were also briefed and

discussions held.

5. It was decided that were a third engine to experience similar problems, it will not be shut

down; instead, both the previously shut-down engines will be restarted.

6. There was the question of whether and when to dump fuel. If landing with weight much

above the max landing limit, then energy stored in brakes heating up after touch-down

and explosion of tyres. Decided to start dumping fuel about 10 minutes later and

continued until dropped to below max landing weight.

7. Plane diverted safely to Charles de Gaulle.

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20 mins from nearest airport – Paris Orly

Discovered engine vibration in engine 4. Engine 4 shut-down.

Turned aircraft back towards London

Updated ATC, and requested priority landing at CDG

Decided even if more engines suffered vibration would not switch them off, and will restart the two that have been shut down.

about 5 mins later

Discovered vibration in second engine. Also shut-down.

Informed cabin crew, did mini-brief,

Pan-day signal sent out

Declared Mayday, decided to divert to nearest airport,

Informed ATC.

Checked location, available airports were Paris Orly and Paris Charles de Gaulle (CDG)

Various considerations led to decision to divert to CDG

If complete engine failure could even glide to CDG

Renewed destination to CDG in flight computer, now ready to select exact route

Checked Paris weather. Due to familiarity with airport, assumed suitability of terrain, runway etc

Dump fuel? Route-planning

Started dumping fuel just over 10 minutes discovery of incident

So selected the alternative route, opted for single frequency approach,

Possible routes? East runway shorter and could easily get there using tail wind, bt would mean flying over Paris

Program destination, current location and desired route into computer to get magenta flight line

Paris CDG

Continue approach using Heading Select mode – direct control.

Landed safely – weight a little over max landing weight

3.2.2 Decision Timeline Engine vibration incident (P2, 15 Sep 2008 1330h)

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3.2.3 Decision Table Engine vibration incident (P2, 15 Sep 2008 1330h) Decision Considerations Cues Cue use Goals Further Observations

Engine vibration: Switch off engine 4

Engine vibration fault registered, followed standard procedure, as instructed by checklist.

vibration guage, amber vibration light,

Checklist

other engine parameters e.g. pressure,

Engineer went out with tool to manually determine from which engine the vibration originated

Checked as safety precaution

Flight safety Switching off the wrong engine was a common mistake since there was only one engine vibration indicator for the whole panel displaying the 4 columns – one for each engine – of engine parameters. So can end up with conflicting information.

Turn back towards London

+ PanDay

How well would a 4-engine plane cope on 3 engines? Could it make it all the way to Lagos? Could travel ahead but would have to get engines fixed later, say in Barcelona?

Usual flight parameters --- Return to London

Engine vibration:

Switch off second engine

Should still follow the std procedure? Implications of running on only 2 engines?

Checklist + vibration light

As before Flight safety

Divert immediately to Charles de Gaulle

+

MayDay

Statistically small possibility of having the second engine vibration over such a short period, so assess seriousness of incident – warrant MayDay signal?

How to inform ATC of situation?

Various engine

Successful diversion to nearest airport

One person talked o ATC while the other flew the plane

Captain then briefed cabin crew of situation and the scheduled diversion

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Where to divert to? Orly was closest in terms of distance but CDG was better – all the pilots were familiar with it. Could land at CDG even in case of complete engine failure – currently enough altitude to glide to touch-down

Weather? Terrain?

Request priority landing.

parameters, green-arc,

Selected Northern route

Route towards the East had a shorter runway and could make it if wanted to run on idol thrust, but would have to fly over central Paris (the other route does not), any incidents would have greater consequences.

Magenta line

Destination, runway, arrival, waypoint, distance to go,

Needed to program destination, e.g for departures: input departure airfield, instrument departure procedure; arrivals are similar

Ensure safety for the Paris population comes first

Task often performed on simulator

Dumped fuel Currently over max landing weight? Must dump fuel? If do not, at risk of brakes burning up and causing explosion once on ground – cannot even use liquid coolant straight away.

If dump fuel, when? Dump during descent or dump first then descend?

Fuel gauge? Safe landing Always remained slightly due north of flight profile so the fuel can be dumped during flight.

Approach made in Heading Select mode

How much automated control how much manual control? Other available modes, no hnav and lnav in flight management system?

How is the energy being transferred – potential to kinetic, when to have the flaps out, when to put on the speed brakes.

Direction, flight level changes, speed, thrust, air speed, distance to end of runway

2 or 3 times tables

Sometimes would make quick mental calculations – when to descend, what speed at which point, or how far can you glide starting form this height

Safe landing

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Other Queries Considerations Inadequacies About the Present System Suggested Alterations

Problems with pilot-training simulations

Programming flight route into FMS

“getting the magenta route line” poses high workload for pilots with less experience

Often can’t get the route into the computer –forget to change the flight destination

Younger guys spend disproportionate amount of time to get a magenta line,, especially in a stressful situation such as in the event of a diversion, caused by e.g. losing engine. They often rely too much on automated systems –feel the need to have the route they are flying on, all the quantitative data displayed in front of them.

Cannot choose a new route on management computer until you change the destination

e.g. changing destination for diversion

On the Boeing flight management computer, have to press route button, come up with page 2 as default, then page back to get to the front page, select new destination, e.g from LHR to EGHL. Need to select route point of destination before you can change the way point for the destination,

Often all the information is available but want to be able to extract it in digestible manner.

Lack of spatial awareness

Aspect of spatial awareness?

Intuition?

But if you put the restraint in wrong, then the computer wont tell you this is wrong they wont tell you that given this is your energy, you cant achieve this etc.

Cannot judge how far to the airport without seeing the numerical distance written in digits right in front of them

Not aware of where they are in space

Some form of energy management display

Present FMS system error-prone – if your energy is of the wrong order of magnitude, the computer does not tell you this

Experienced pilot:

“I use a 3 or 2 times table, so if it says 45 miles to go and I’m at 15000 feet, then I know I’m on the profile, then if I was 15000 feet and there’s only 12 miles, then I know I have to lose 30 miles some how.”

If programming FMS carefully, input some particular restraint, say at 10 miles want to be at 3000 feet above airfield, want flap 5 out 180 knots; computer then give you a vertical profile on v-nav, tell you where you are relative to your profile. Computer can then calculate pre-program descent point, and control and fly that

Better displays for energy management

Intelligent energy management – inform you of any obvious errors?

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vertical profile etc. But no way of knowing if the initial constraint was entered correctly

Developing accurate mental picture

How to train pilot to develop a mental picture of their situation, their surroundings etc

Situation awareness

2D picture?

On A380 have vertical profile displayed, but lots of information there, not easy to interpret

More intuitive displays?

e.g. would help to see what would happen if the plane has too much or too little energy? i.e. where would it land or could land if the current situation is projected into the future.

Verbal constraints?

Current training method:

On a map, around destination point, put in 10 mile ring, then 25 mile ring. On the 25 mile range ring the instruments will work…on the charts we have a safety quarter, in that segment I know I can go down to 1500 feet, in another segment might only go down to 3000 feet depending on terrain…then make sure by 10 mile ring have a certain speed and altitude

Vertical profile displays only scale and arrow, simplistic form, will only display based on what constraints you put in.

Airbus use Brake To Vacate, map with turn-off point, have pathline for dry conditions and one for wet conditions that depends on landing weight.

Want a display that shows a line that predicts path of aircraft starting at the present altitude and distance from runway, if assuming idol thrust. So will receive warning when the calculated path exceeds end of runway – severity of warning increasing with excess length – so the pilot knows immediately the aircraft has too much energy. This is more intuitive.

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3.3 Oil leak incident (P3, 17 Sep 2008 1030h)

3.3.1 Incident Summary

1. In 2005, during an examination of before take-off, a small oil leak had been registered on

a 767 Heathrow aircraft scheduled for a flight from Uganda back to the UK, but the leak

was not deemed dangerous enough to warrant any further action. However, about 2.5

hours into the flight, having known about the leak and therefore taking extra precaution to

check the oil gauge, the co-pilot observed an unexpected drop in the oil supplying one of

the two engines – it was discovered that only 8 quarts (out of a 20 quart capacity) of oil

remained in one engine, where in normal circumstances there should have been about

18 quarts.

2. An immediate assessment was made; the aircraft was, at that point, flying satisfactorily,

and on-course with no problems, the situation was not thought to be urgent.

3. It was decided that an assessment of the oil had to be made, to determine whether the

12 quarts was lost due to the sudden take-off and that remaining 8 quarts would be

consumed at a slow, stable, safe rate; or that the rate of loss of oil was in fact rapid and

constant throughout the flight. The latter case would result in a potentially dangerous

situation of the aircraft running on one engine and the possibility of a diversion being

made. With a stop-clock, the oil was timed – how long before the level dropped from 8

quarts to 7, then from 7 to 6.

4. Meanwhile, the two pilots discussed and agreed on a flight procedure that both will follow

should the event of the engine failure occur – how to configure the aircraft when running

on one engine etc – a flight guide book + checklist was consulted and possible actions

discussed and reviewed.

5. The oil was found to have dropped from 8 to 7 in 30 minutes, the situation then became

more serious. However since the readings provided integer units only – there was no

indication of how long the oil level had previously been at 8 units before the problem was

discovered, for a better estimate the oil was timed from 7 to 6.

6. While still timing, the pilots began to consider nearby airfields that are available for a

possible diversion, many factors – environmental and human, were taken into account.

The situation was dynamic. It was more preferable to divert to the North Coast of Africa

or better Europe, rather than somewhere in central Africa where the facilities are not so

adequate.

7. After further discussion the airfield at Khartoum was thought to be the best option at the

time, and the available data on routes/airways to Khartoum and on Khartoum airport

itself (documented on “plates”) – detailing width of runway, elevation etc, was collated.

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The precise diversion route was decided upon, and while one pilot spoke to the

engineers back at Heathrow to gather expert technical advice, the other was engaged in

processing this information and programming the diversion route into the “second flight

path” on the computer, to be assessed readily if the diversion were to occur.

8. Further planning and re-planning, routine exercises performed, more in-depth planning of

diversion route and diversion procedures were carried out. The two pilots updated each

other on their respective findings and the situation was reviewed. The oil dropped from 7

to 6 quarts in 25 minutes. Oil levels were continuously monitored.

9. The dynamic planning continued throughout the duration of the flight. The oil lasted and

no planned diversion ever had to be executed. The aircraft reached Heathrow safely and

on schedule.

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before take-off, Uganda:

Small oil leak detected in one engine, but assessed to be safe to fly as scheduled

Checked current aircraft status – no immediate problems

Timed oil to determine rate of leakage

Levels dropped from 8 quarts to 7 in 30 minutes

Both pilots went through procedures + checklist in case of immediate engine failure, formed mutually agreed plan ready for instant reaction

approx 3hrs into flight, at least 2hrs from Khartoum:

Oil was being lost fast enough to warrant considering diversion to nearby airports

Checked current location and decided best option was Khartoum.

Agreed on best route to Khartoum should diversion be necessary

Possibility of being left with only one functioning engine

One pilot talked to engineering back at Heathrow for technical advice.

The other programs route to Khartoum + other divert information into “second route” system on flight computer

2.5 hrs into flight, over central Africa:

Discovered oil dropped from 20 quarts down to only 8 quarts. Query major oil leak

Situation continued to be monitored; oil levels monitored found oil dropped from 7 to 6 in 25 minutes – diversion now a real possibility

No helpful advice received. But decided not to make further climbs for fear of additional stress on

Further dynamic planning and re-planning – REVIEWED situation

Diversion planned to more details, consulted charts etc, but not including details of navigation or energy management

approx 6hrs later, Heathrow:

In the end no diversion was necessary, aircraft landed safely in Heathrow

3.3.2 Decision Timeline Oil leak incident (P3, 17 Sep 2008 1030h)

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3.3.3 Decision Table Oil leak incident (P3, 17 Sep 2008 1030h)

Decision Considerations Cues Cue use Goals Further Observations

Check oil levels in engine 2.5 hrs after take-off

Know about small leak already, so needed to be extra cautious

Two screens displaying engine parameters

Flight safety In this case the consequence of the problem is evident – lose one engine, this is not always the case

Time rate of oil leakage

How long to drop from 8 to 7 quarts, then from 7 to 6 quarts? Was the 12 quarts of oil leaked during sudden motion of take-off and no further rapid leakage will take place (case 1), or was it lost at a constant rate over the 2.5 hrs (case 2)? The latter situation is more dangerous. How much oil is actually needed to get back to Heathrow?

Bottom screen displaying oil levels in digital integer format; time registered on handheld stopwatch

Digital meter could not indicate how long oil level had been at 8 prior to discovery of problem, so had to time decrease from 7 to 6 as well for better idea

To determine whether situation is case 1 or case 2, and act accordingly

Both pilots independently carried out the timing – to minimize possibility of human error

Agree on plan – set of procedures to follow if engine failure occurred at that instant

Is the plane still safe? On the right course? What to do if the engine stopped? How to cope with only one engine?

Go through checklist for this, need to configure switches?

Have to descend? Divert? Need ATC permission for any diversions? Will these permissions be granted in central Africa? Will facilities be available at the airport when we get there?

Checklist in “quick reference handbook” – explanation of every message that can appear on plane

For certain procedures had to consult handbook even if can recall from memory.

Work through checklist.

Flight safety, try to keep to scheduled route

Decision was not time-critical, more of a planning exercise

Was important that both pilots were clear about the same plan

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Discuss possibilities for diversion

Where? When? As you continue flying the environment will be changing also.

Is the situation urgent – need to find the nearest airfield and land straight away? Or do we have enough time to choose a better option? How many options do we have?

Few facilities in central Africa, the only contact was through hf radio, ATC rarely reply to the regular traffic reports anyway. But will the oil last until we get to Europe or at least the North Coast of Africa where the facilities are better.

When choosing airfield, consider terrain, location, local weather, availability, humanitarian conflict, does BA operate there – if so, better for dealing with passengers, ease of access, runway length, system for accessing runway – compass-based VOR/DME system or one similar to Heathrow – Heathrow option better.

If we divert who do we need to inform?

Various charts and maps

Booklet of plates detailing the essential info about each airfield

For finding current location, getting sense of surroundings, and situation near possible diversion site.

Lookup airfield location,

look up/recall airport code,

find correct plate for chosen airport,

find right side of plate, extract relevant details – elevation, runway length etc

Have plan ready in case of diversion – so can have instant reaction when required

Only one copy of booklet, had to share

Preliminary decision to go to Khartoum in the event of diversion

Oil just dropped from 8 to 7 in 30 minutes, situation worse than thought, we have case 2 in above. What to do?

Took out plate for Khartoum – width of airfield, elevation of airfield

Decide on airport for possible diversion

During pre-flight briefing session, made sure on scheduled route always had an airfield at most 3hours away, but when air-borne

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Three airports available:

Option1: not viable, for domestic flights only – not international, but runway long enough, thought of as last resort – would only land there if on fire

Option2: airport to west, but there is civil unrest, the facilities are good though

Option3: Khartoum – the one recommended in the briefing session – so met criteria for diversion airfield, a lot known about it, facilities suitable, currently 2.5hrs east

So how was the weather at Khartoum? Which runway to land on? Type of runway approach to take – what is the system at Khartoum?

Decision heights

Priorities are:

Safety

Ease of landing approach

Passenger satisfaction

you can go wherever you want

Talk to engineering at Heathrow

Anything that can be done on the technical side? Can’t go and fix the mechanical fault right then and there, or fill with more oil…

The radio connection was bad, really need to listen hard – one person is occupied completely doing the contacting.

none none Get more advice Nothing more could be done on technical side

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Make no more climbs

Might go to higher altitude to save fuel, but would need to work/put more stress on the engines to get to higher altitude, this might increase fuel leakage?

Altimeter Maintain height Minimize fuel loss

Played safe

Program route to Khartoum into “second route” in computer

Which route to choose? Best route, airways like motorways – crossing points, motorway exits? Joint decision between the pilots.

Are there features of terrain around Khartoum that would make an approach from particular direction difficult?

At this stage just program the routes – about 3 to negotiate with. Any problems getting into the airfields?

Maps and charts

Terrain charts

Coordinates of your current location

Programmed route into flight computer, ready to be accessed at the press of a switch

Have second route ready – can switch to immediately if diverting

One pilot was doing the programming while the other spoke to engineering – maximises work efficiency.

The pre-programmed flight is necessary because the conditions are too variable for any approach to be executed completely manually

No navigation details or considerations of energy management yet, do not want information clutter – since might not actually land at Khartoum – and such details can be taken care of during the diversion

Review of situation

Go through everything from the start. Do both pilots agree on the problem? Is it still the same problem? What are the options? Are we up-to-date with what each option involves? Are the plans for diversion all set and ready?

None None Precaution – being prepared

Continue to monitor oil levels & situation

Took 25 minutes to drop from 7 to 6? What are the implications? Immediate action?

Oil gauge Timing fuel leak rate Keep well-informed of situatio & changes

In the end no diversion was necessary.

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Hypothetical Situation

Decision Considerations Cues + Usage

If the diversion had to be made after all what would have happened?

land

inform other aircraft via radio

Have lost engine, cannot maintain altitude,

We are descending, need to make sure others know where they will conflict with us.

Is the runway visible?

ATC permission given? May have to descend regardless. But then will not know if coast is clear. If can see problematic aircraft coming towards you, then change route to avoid collision.

Most aircraft will have TCAS(?).

Once that you program the routes into the computer, if you are on the “pink line” then you are in the middle of the airway, everyone flying on different levels, separated by time, or by altitude.

Can spot conflict on TCAS system, or and other aircraft tell you.

An inexperienced pilot facing above incident

+

Other factors affecting descent

NA Finding correct chart

From which pinpoint your precise location.

Knowing your aircraft

Each aircraft is unique, the computer calculations are not always correct for your aircraft. E.g. if the computer calculates you should make a descent at some particular height, might have to do this 3 or 4 feet sooner.

Airfield traps

Each airfield is unique, computer calculations may be misleading – higher temperature, thinner air, etc these factors make actual descent speed, ground speed, very different from that displayed on screen

Knowing the unique 4letter runway codes assigned to each airport

Would use the calculated altitude as a guide.

Altimeters, speed indicators – don’t use ground speed indicators while executing descent. High up, would use mac numbers (?), mac 7 8; lower down, use knots (290 to descend at Heathrow).

want to be at about 180 knots at 30000 feet, so depending on weight of aircraft, how much flap etc

altimeter, speed indicator, ground distance to

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Aircraft configuration

Mental gate-points

Constantly checking but have a few important mental check-points: know what speed you should be at by what altitude, how far from end of runway

cover

Suggestions for improvement

NA Want two “green arcs”, currently only have one. For your present conditions, computer can display your position on map – e.g. when at 30000 feet computer shows your location, but want predictive function - display estimated location when at altitude 15000 feet?

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3.4 Hydraulic failure incident (P4, 17 Sep 2008 1330h)

3.4.1 Incident Summary

1. Pilot 4 was the co-pilot flying a 747 from Singapore to London. Because of the length of

the flight, there were four crew members, working in shifts. Pilot 4 was part of the

second, or “heavy”, crew.

2. Three hours before arrival there was a major hydraulics failure during her shift, and this

was the catalyst for the incident described here. With a hydraulic failure of this

magnitude, the slats, flaps and landing gear take much longer to deploy than normal.

This means that much more delicate control is necessary or the plane will enter an

oscillation.

3. Pilot 4 and the senior pilot monitored the situation and prepared a series of detailed

scenarios, considering other problems that might arise and how they would react to

them. Two hours before arrival they awoke the other crew and briefed them on the

situation. The new crew considered the scenarios and also generated some additional

ones.

4. They made a “Pan” call, meaning that ATC allowed them to make their own decisions

about how and when they would approach the airport. Because of the slow reaction from

hydraulic equipment they used a long, straight, approach, flying under the nominal flight

profile. Although less fuel efficient, this meant that energy management was not a

problem and that they had time to react to situations.

5. The cabin-crew was briefed on the situation and prepared for a possible emergency

landing. At 3000ft they deployed their gear, but an electrical fault meant they believed

that the outside starboard gear did not deploy.

6. They were forced to “go-around” and approach again, prepared for a partial-gear landing.

This took about twenty minutes, and included a re-briefing o the pilots, the cabin-crew

and the passengers. Passengers were not asked to enter the brace position. By this

time they had been flying considerably longer than the normal flight time and fuel was

becoming a concern. They then proceeded to land the plane.

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3 Hrs from London Heathrow:

Failure of two of the four hydraulic systems.

Checked current aircraft status – no immediate problems

Went through checklists to find prescribed actions

Issued a Pan call to notify Heathrow of a problem

Both pilots generated scenarios of what might occur in the future and decided on courses of actions that might be taken.

Approaching LHR

Gear fails to deploy properly

Briefed them on the situation

Described possible scenarios and courses of action

Control surfaces and landing gear react more sluggishly

Generated additional scenarios and courses of action

Discussed new scenarios with other pilots, generated courses of action

2 Hrs from LHR:

Woke the other crew.

Landed safely

Circled around to approach again

Monitored fuel because of unusually long flight time

Briefed cabin-crew to prepare passengers for a partial gear landing

3.4.2 Decision Timeline Hydraulic Failure Incident (P4, 17 Sep 2008 1330h)

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3.4.3 Decision Table Hydraulic failure incident (P4, 17 Sep 2008 1330h) Decision Point Considerations Cues used and

sources How cue used Actions Goals

Hydraulic failure Can the aircraft continue flight?

Engineering reports, checklists

Went through checklists Continued flight to target airport. Generated scenarios of what might happen

Find a solution that optimised the flight –e.g. landing at target airport – without compromising safety. Also prepare for other events that may add difficulties.

Can the aircraft land normally?

Issued a “pan” call, meaning that ATC allowed a direct approach, rather than having to fit in with other traffic.

Land safely.

Gear fails to deploy How much fuel remains?

Fuel gauge Read directly Recognised that they must land on the next approach.

Land before running out of fuel.

How serious is the gear failure

Gear instrumentation Read an outside starboard gear failure (although no failure had actually occurred)

Briefed the cabin-crew and passengers to prepare for a partial gear landing

Land the plane without damage to passengers or crew.

Generated scenarios for a partial gear landing

Find optimal solutions and be prepared for other eventualities.

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3.5 SFO Energy Profile Incident (P4, 17 Sep 2008 1330h)

3.5.1 Incident Summary

1. Pilot 4 was the first-officer on a 747 approaching SFO when they were given an

unexpectedly early landing slot by ATC. They were too high and too fast to make the

approach clearly, and it took some time for the captain on the flight (the handling pilot) to

realise this. By that stage the situation was worse and they were forced to deploy the

gear early in order to act as a brake. This is undesirable because of noise concerns –

the gear makes a large amount of noise as it passes through the air, and this is

undesirable for people on the ground. The situation could have resulted in them having

too much energy when they entered their final approach, in which case they would have

had to circle the airport and try again.

2. This is an ongoing problem at SFO, so there was an unusually detailed briefing during

the planning phase. Possible scenarios and appropriate reactions were considered well

in advance. In the actual situation, they were following a path as shown in figure 1.

They were expecting to fly the outbound leg for a significant period of time*(I need to go

through the tapes and get specific values for altitude and speed)* and then turn toward

the final approach path. In accordance with this, and contrary to the briefing, the

handling pilot performed a slow (~750ft per minute) descent. This meant they were

unprepared for a short approach when control vectored them towards the approach path

after only eight miles.

3. The captain did not realise that his energy was too high until halfway to the approach

path, at which point he was forced to deploy his gear in order to lose enough energy to

land.

4. British Airways provides two targets that pilots should meet in order to safely land the

plane. The first is a given configuration and energy at 1000ft, the second is at 500ft. If

pilots miss the first “gate” they may continue, but they must hit the second gate in order

to land the plane. The pilot missed the first gate, but was able to hit the second gate,

and the plane was landed as is normal.

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Approaching SFO

Followed standard energy profile

1000ft gate, 3.3nm from runway

Energy profile still too high, but approaching required state Calculated new track

miles remaining

Realised that energy was inappropriate for new descent profile

Began to lose energy at an unusually high rate

Instruction to turn in quickly

Landed safely

Continued descent while losing energy at increased rate

Energy profile acceptable

500ft gate

3.5.2 Decision Timeline SFO Energy Profile Incident (P4, 17 Sep 2008 1330h)

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3.5.3 Decision Table

SFO Energy Profile Incident (P4, 17 Sep 2008 1330h) Decision Point Considerations Cues used and

sources How cue used Actions Goals

Approaching SFO Fuel Efficiency Projected track miles for normal approach (calculated based on pilot estimate), altitude

Compared projected track miles with altitude using the 3x heuristic

Descended slowly, approx. 750 ft/min

Land safely while optimising fuel use

SFO regularly requires a rapid approach

Prior experience, noted and considered during the briefing.

Ignored

Given instructions to turn in toward approach path

Are they vectoring us for landing or just to the other side of the approach?

TCAS provided some information about local traffic situation

Bring plane to a state where they could land safely

How many track miles remain?

Distance flown past SFO, distance to approach path from TCAS

Added the two distances together, producing an approximation of remaining track miles.

Used remaining track miles to calculate appropriate descent profile

Provide a basis for calculating desirable energy profile.

Is our energy profile acceptable?

Track miles remaining, altitude

Used the 3x heuristic, found that they had too much energy

Used control surfaces and gear to lose energy as rapidly as possible

Lose enough energy to land safely

1000 ft Gate Is the energy profile suitable for landing?

Compared specific values of speed, altitude and configuration against values mandated by company.

Found that values were not within the appropriate range, but that they could be fixed by the 500ft gate.

Continued descent Continue descent if a landing was possible, otherwise declare a missed approach and circle for another attempt.

500 ft Gate Is the energy profile suitable for landing?

Compared specific values of speed, altitude and configuration against values mandated by company.

Found that values were within the desired ranges.

Landed safely. Land only if parameters are within state bounds.

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4. KEY FINDINGS

In this section we describe our findings and insights derived from the interviews with the

pilots regarding their spatial-temporal needs on the flight deck. For the purpose of this report,

we will only discuss those issues relevant to understanding how spatial-temporal matters are

considered in terms of aircraft flight profile.

Our findings are based on a collation of common themes identified among the four

interviews we conducted. We acknowledge that the findings from four experienced

commercial pilots are not representative of all pilot strategies, we believe that this work is

adequate for identifying a significant number of issues relevant to the spatial-temporal

management of flight.

4.1 Energy profile management

One of our key findings is that of energy profile management. Understanding this Energy

profile management is the process by which pilots manage the potential energy (energy in

terms of altitude), and kinetic energy (energy in terms of the aircraft’s motion). This needs to

be managed in particular in order for the pilots to bring the aircraft to a point in space and in

time so that they are not “too high and too fast” at that point. The pilots indicate that energy

management is particularly important and challenging during the descent from cruise altitude

(around 30,000 ft) down to the approach gate at 3000’ and 10 nm from runway at 180 kts,

and at finals gate at 1000 ft, 140 kts, 3.3 nm from the runway. This descent may be carried

out over the 80 to100 nm as the aircraft approaches the landing runway.

4.2 Track miles

One of the key concepts in energy management is the notion of track miles. This is the

distance that the aircraft will actually cover as the aircraft descends to the target point in

space. This would include distances required for re-routing around weather, or flying longer

or shorter distances due to changes in runway direction, and so on. It is not the point-to-point

distance between the aircraft and the destination.

The situation presented by P1 in the Bucharest thunderstorm incident described the

considerations and actions taken by the pilots to control their energy profile to land 20-30 nm

shorter than they had originally planned. This meant that the pilots had to find a way to lose

the same amount of energy in the shorter available distance.

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The situation presented by P2 when forced to land at Charles de Gaulle was a reverse of

this problem. Rather than decide if he could lose sufficient energy, he needed to verify that

the plane had sufficient energy to glide the distance to Charles de Gaulle.

The situation presented by P4 on the San Francisco Airport incident shows a situation in

which pilots’ projected track miles did not match the controller’s intended track miles. When

the controller vectored the pilot for approach, the pilots were not well situated for the

decrease in track miles. Once again, the pilots had to lose energy quickly in order to land in

the available distance.

Track miles are an important concept used by pilots to determine the rate pilots need to

expend the aircraft’s energy as it descends. Ideally, the track miles should be sufficient for

the aircraft to gently glide with minimal power to arrive on the runway at its landing speed of

about 140 kts. This represents the idea of a controlled descent approach, and the basic

principles of this can be applied to assist pilots in flying to a 4D trajectory.

P2 provides an example of how tracked miles can be represented. He often uses this

illustration to help train new pilots (Figure 3a). The inner ring represents a 10 nm circle

around the runway. When the aircraft reaches this circle it must have a suitable energy.

Using a 3x height heuristic, this means that the aircraft must be at about 3000ft. The larger

ring is a 25nm circle. The route planned in the briefing is drawn on it, and the route may be

more than 25nm. When the aircraft crosses this circle, any heading change from the

controller can be represented. A route that shortens the distance to the inner circle means a

decrease in track miles, and thus a need to increase energy loss. A route that increases the

distance to the inner circle means an increase in track miles and a potential for a more

gradual descent (Figure 3b).

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Figure 3 (a)

Figure 3 (b)

Figure 3. a) The diagram that P2 uses to explain to trainees how track miles can change. b) When a new routing is received, pilots know that if the routing is closer to the inner ring then track miles will decrease, where a routing away from the inner ring will increase track miles.

P2 uses this representation to help pilots understand the issues needed to make quick

decisions about how a new heading will affect track miles, without needing to wait until the

new route is programmed into the FMS.

4.3 Fly by parameters and the 3 times table heuristic

P4 explains how she “… fly by parameters …” using distance to go, altitude, and speed, to

manage energy and to guide the aircraft safely in to land. Included within the concept

‘distance to go’ is the heading the aircraft should fly towards the target destination. In the

incident described by P1, he reports using a “3 times table” heuristic that uses these

parameters to estimate the track miles needed to dissipate the aircraft’s energy, e.g. if the

aircraft is at 30 thousand feet, then it will need to effect the descent over 90 tracked miles

(30 x 3).

In the incidents described by P1 and P4, the pilots use these information to provide an

estimate of whether they are likely to be arriving at the target gates at the desired altitude

and speed. For example, in the Bucharest thunderstorm incident, when P1 received the

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request from ATC to land on Runway 08 instead of Runway 26, they were about 80nm

away, and at 30,000 ft. Using the 3 times table heuristic, the aircraft would have needed 90

nm of track miles to descend comfortably. As Runway 26 was their planned runway, they did

not initiate their descent earlier as they had the distance to reduce their energy. With the

change in runway, they now had a much shorter distance of tracked miles to reduce their

energy. They needed to carry out actions to lose energy more quickly. P1 reported that he

constantly carried out this heuristic-based calculation as they executed their manoeuvre to

descend with the shorter tracked miles.

4.4 The ‘green arc’

Flight deck navigation aids such as the ‘green arc’ on the flight navigation display provide an

arc of where the aircraft’s trajectory is likely to intersect with the ground. However, according

to P4, it only shows one arc that is based on the aircraft’s current position in space and its

attitude. These parameters will change as the aircraft loses energy, and it is therefore not a

reliable indicator of whether the aircraft will approach the target destination (an intercept of

the trajectory with the terrain) with the right level of energy.

The ‘green arc’ also targets the point in space where an aircraft will intercept the target flight

level. The arc takes no account of time constraints. Since the information only relates to the

target flight level, there is no information regarding destination points that are not on the final

flight level, even though pilots do report using such intermediate destinations. It also

provides no information about destinations in level flight.

An adaptation that used the line to provide information about 4D gates would be useful to

help pilots navigate the future 4D Trajectories defined under SESAR. Also, the current

implementation of the ‘green arc’ is intended to support real-time flight control, rather than as

a decision and planning aid. P1, P2 and P4 have suggested that a function they could

benefit from is to allow them to designate a point, or even several points, in space and to

then allow the system to suggest the energy profile needed to reach the target point in

space. Such a point could include the arrival gate, or any 4D point in space and time.

4.5 Awareness of surrounding traffic

Although tools like CDTI (Cockpit Display of Traffic Information) have been in planning and

development, it has yet to reach operational fleets in a significant way. In lieu of this, the

pilots interviewed report using their TCAS systems to display the secondary radar picture of

the traffic situation in the 30nm surrounding area. TCAS was not intended to provide aircraft

heading nor track history information. It was only intended to show conflict and the

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instruction to climb or descend. As such the displays only show locations of aircraft at a point

in time. P1, P2 and P4 report following the display over a short period of time to see the

“pattern” of traffic around an airport, e.g. to discern and anticipate how they are likely to be

sequenced for arrival at a busy airport.

The awareness of this knowledge helps them plan ahead their arrival trajectory, and if they

are under radar vector control, the traffic patterns ahead, e.g. how the aircraft are lined up

and sequenced for landing, can provide them with an indication of the air traffic controllers’

intention as they prepare to approach an airport.

4.6 Flight Management System does not work for the pilots

P2 reports that the descent algorithm in the FMS overly conservative, calling for

unnecessary drag that needs to be compensated for later with increased power. In this

case, the FMS causes pilots to come in too low and slow, requiring thrust to be applied and

wasting fuel.

P4 reports that the FMS does not allow for lag in the control surfaces and acts too late to

follow an appropriate energy profile. In this case, the aircraft comes in too high and fast, and

can cause a rushed approach.

The statements from the two pilots are contradictory and may represent differing experience

levels, different aircraft types, or different styles of flight. The important thing to note is that

neither pilot believes that the FMS provides an optimal descent tool.

It is quite possible that these beliefs are unfounded, however, the lack of information about

energy management and a lack of transparency about the FMS’ method of calculating

descent profiles mean the pilots do not have confidence in this tool. By adding information

and transparency, the tool, or the pilots’ confidence in the tool, could be improved.

Whether P4 is correct in her assessment that the FMS does not take lag in to account, this

raises an important point regarding the planning of 4D trajectories. Many systems fail to

take lag into account, and as such the operators must manually compensate for this fault.

When planning 4D trajectories, efforts should be made to ensure that the trajectories make

allowances for the time necessary to change the state of the aircraft. Assuming that the

aircraft will instantly change configuration may lead to difficult, unrealistic, or even impossible

trajectories.

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5. DISCUSSIONS & CONCLUSIONS

We often use the term "3D" to mean the three dimensions of physical space, and often also

imply virtual reality-type of spatial representations, i.e. virtual representations of the real

world in which one can walk in or fly through. We can however also think about 3D in a

more mathematical sense as a problem involving 3 dimensions or variables.

For the purposes of developing alternative design concepts, we have found that the notion of

3D as VR-space concept is limiting and can in fact hinder our thinking about the right kinds

of solutions. Why? because this pre-supposes that the solution will inhabit a particular style

of representation, i.e. a VR-style of spatial representation, when in fact the pilots and

controllers could be better served by a more powerful multi-variate representation, which

could very well be presented in a 2D physical display.

Many of the problems identified by controllers and pilots are actually multi-variate problems.

Just as metrics and heuristics are used to condense 3D problems into 2D solutions (e.g. the

3x heuristic) a multi-dimensional problem could be condensed into 3D. If we consider each

dimension of the display to be a resource, then we must make sure that those resources are

well spent. A veridical 3D representation of the airspace is likely to provide a good

understanding of spatial relationships but at the cost of other data. We may be able to get

better value from our display resources by condensing multiple variables into each

dimension of the display, or by displaying non-spatial information on some dimensions.

The three spatial dimensions of the airspace match naturally with the three spatial display

dimensions available to us. However, our recent work has led us to the conclusion that this

match may be unnecessary. Just as altitude and speed can be better expressed as a single

energy value, there may be areas where combinations of other spatial, temporal and

kinematic can be expressed as single, abstract values. In this sense the display dimensions

could be considered resources, to be spent in the most effective way possible, whether that

be displaying a simple spatial value or a value that represents another variable or

combination of variables. The question then becomes: how do we provide the best quality

information on the three display dimensions available to us? When specifically considered

for pilots:

"How should we represent and navigate in multi-variate information, in a

way that would support pilot sense-making and decision-making for

navigation and flight control to achieve 4D trajectories as described by

SESAR's Reference Business Trajectory flights?"

From this we face further questions:

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• What visual form should the logic of the information to be communicate take?

• What interaction methods are suitable for the likely use situations?

• What variables are important? e.g. energy (kinetic and potential), drag coefficients,

air density and a host of other factors affect stopping distance.

In conclusions, it appears that the flight computers either hinder or do not facilitate some

pilot tasks. To overcome this, they make use of heuristics to simplify the task of managing

energy (e.g. the 3 times table). It does not show the intermediate points between current

state and goal states. Physical systems have lags which need to find their way into the

calculations and their representation of the system state.

From this early study, it appears that one of the key support tools for use in the flight deck

under a SESAR context will be tools and displays to assist pilots in flying 4D trajectories. It

would be beneficial if such a future flight deck system incorporated:

• Energy profile support

• Indications of track miles

• Interpretation of multiple variables – such as heading, speed and altitude - to assist in

energy profile management

• Adapted tools such as the ‘green arc’ to support energy dissipation during real time

control.

• Awareness of the surrounding traffic situation

• The representation of process lags to support energy profile planning and execution

• Information about the intentions of controllers, as pilots currently use their TCAS

displays to see the traffic situation ahead at, say, around the airport, to observe how

the air traffic controllers have lined up or sequenced the arriving aircraft. This provide

the pilots with clues as to the intention of the air traffic controller, allowing them some

insight about the controllers intentions. This provides us with an opportunity to

develop concepts for tools to help communicate intention between the cockpit and

the ground, which will have an impact on how pilots manage their aircraft energy

profiles.

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