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Head Up Guidance at easyJet

Mike Keane
Chief Pilot easyJet

Kim O'Neil
Advanced Aviation Technology Ltd.
February 2001


easyJet has established itself as a successful and growing low cost airline with its innovative approach to operating aircraft in an efficient and cost effective way. This extends to all aspects of its operations: from the boardroom to the cockpit. The benefits for its customers are a safe, efficient and friendly airline with very low fares. easyJet works hard to maintain this competitive edge everywhere it can. The introduction of Head Up Guidance Systems in the cockpit - the first UK airline to do so - is another example of its determination to maintain this competitive edge. easyJet has opted for the Flight Dynamics Head-up Guidance System for its existing B737-300 fleet. easyJet objectives are increased safety, improved operations and performance gains, which easyJet will pass directly on to its customers.

1. Introduction

Improving safety is of great concern in an industry that depends upon customer confidence. easyJet's purpose in adopting the Head Up Guidance System provided by Flight Dynamics is specifically to enhance safety, to improve its operating performance and to further improve its commercial efficiency. Head up Guidance Systems have significant potential for improving and enhancing the flight capabilities of aircraft. Even more benefits can be obtained by improving the pilot's situation awareness. Consequently, achieving these benefits is a major goal for easyJet.

2. easyJet Operating Philosophy

The traditional picture of low-cost operators is of small airlines operating mixed fleets of old aircraft at the end of their lives on marginal routes that larger airlines are not interested in. Low cost operators also tend to give the impression of operating on a shoestring near the accepted limits of safety.

easyJet completely busts this model. It operates modern aircraft intensively on busy routes. It operates at a profit and is expanding, buying a fleet of brand new aircraft that will radically increase both its route structure and the intensity of its operations. easyJet makes money by looking at all aspects of its operations and reducing overheads where-ever and when-ever they occur. It has an interesting cost per seat model that allows it to compare its costs with its competitors, in order to offer the lowest possible price to its customers. Above all, easyJet is innovative. For example, its online booking services are way ahead of its competitors and have firmly established it as a favourite with its customers.

This philosophy is carried forward in all its operations. For all passengers everywhere, safety is the number one priority. Any airline that does not ensure the highest levels of safety is courting disaster. Not just in terms of loss of lives and aircraft but also in the straightforward loss of it commercial operating position. Safety is therefore, an essential element of commercial success. Period.

easyJet Aircraft
Figure 1: easyJet operates a very modern fleet

easyJet is not content simply to operate aircraft to the currently accepted safety standards, but wishes to further enhance safety wherever the opportunity exists. This means taking advantage of new navigation, surveillance and communications technology and new procedures where these aid safety in day-to-day operations, for example, enhanced GPWS and enhanced wind shear. There are many areas where Head Up Guidance systems can help contribute towards this. A very straightforward safety benefit is achieved by improving Pilot Situation Awareness. In fact, the safety benefits of Head Up Guidance Systems have been widely demonstrated in military aircraft - often in very difficult operating conditions for over three decades. It is unfortunate that awareness of these benefits has not been as visible as they could have been to civil airline operators.

The introduction of Head Up Guidance into commercial civil aircraft operations is long overdue. Head up Guidance allows the introduction of flight concepts such as 'Angle of Attack', which are very familiar to military pilots but virtually unknown to most civil pilots. Yet these concepts will allow aircraft to be flown in a simpler and far safer manner, permitting the pilot to fly the aircraft safely within its flight envelope irrespective of weight, load and distribution.

3. easyJet Operating Fleet

easyJet operates a fleet of 18 Boeing 737-300's. It has ordered a further 30 Boeing 737 -8700s which it is currently taking delivery of. It also has options to purchase a further 30 Boeing 737 -700/800s. The decision whether to exercise this further option is expected to be made during 2001. There are numerous benefits to operating a new fleet of a single type, which significantly reduce operating overheads. These benefits include low maintenance, reduced spares holding, reduced crew training costs and greater day-today operational flexibility. The list of benefits is long and completely confounds traditional views of low cost operators. Larger airlines with mixed fleets of varying ages of aircraft do not gain these benefits.

4. Head Up Guidance Systems and Safety

The safety benefits of Head Up Guidance Systems are well established. According to the Flight Safety Foundation: "…civil jet transport aircraft equipped with properly functioning head-up guidance system technology, that provides critical aircraft flight guidance and performance information to a correctly trained flight crew, will result in significantly fewer aircraft accidents…" (Flight Safety Foundation Report). In a 1990 study of civil jet transport accident data from the period 1959 -1989, the Foundation concluded that HGST would have prevented or positively influenced the outcome of 31% of the accidents.

5. Rockwell Collins Flight Dynamics Head-up Guidance System (HGS

The Head-up Guidance System (HGS) offers the pilot all critical flight information head-up and superimposed on the real world. Information is focused at infinity so no refocusing from real world to cockpit instruments is required. This makes HGS information easy to assimilate and natural to the pilot.

Figure 2: Head Up Guidance System in Cockpit

The key elements of Flight Dynamics Head up Guidance System (HGS) are:

5.1 HGS Combiner

Optically combines flight symbology with the pilot's view through the windscreen. The holographic Combiner is designed to reflect the light projected from the CRT in the OHU. The holographic Combiner in effect, acts as a wavelength selective mirror reflecting the CRT color while allowing all other colors to pass through the glass.

5.2 HGS® Computer

The HGS Computer receives input signals from aircraft sensors and equipment and converts this data to symbology. The HGS® Computer also evaluates both system and approach performance through extensive Built-ln-Test (BIT), input validation and Approach Monitor processing. The output of the HGS® Computer then goes to the Drive Electronics Unit. The HGS® Computer is installed in the aircraft avionics bay

5.3 Drive Electronics Unit (DEU)

The Drive electronics Unit receives signals from the HGS® computer and conditions these signals to drive the Cathode Ray Tube (CRT) in the Overhead Unit. The DEU contains power supplies and electronic circuitry for signal amplification, distortion and geometry corrections, and system monitoring.

5.4 HGS® Control Panel (HCP)

HGS® Control Panel (HCP) provides the pilot with the ability to enter data required by the HGS® but not available from other equipment on the aircraft.

Figure 3: Head Up Guidance System Components

5.5 OverHead Unit (OHU)

The Overhead Unit projects the image onto the Combiner. The Overhead Unit is mounted above the pilots head, hence the name. The OHU also contains electronic circuitry for display, intensity control, and system monitoring.

5.6 HGS® Annunciator Panel

HGS Annunciator Panel provides HGS® status and warning annunciations to the First Officer during CAT IIIa approach and landing operations.

6. Flight Dynamics HGS Flight Modes

The Flight Dynamics HGS has 4 Modes of operation:

a) Primary Mode
This mode is similar in format to head-down PFD/ND or EFIS Display and uses the aircraft Flight Director to drive the guidance cue.
b) AIII Approach Mode
This mode provides a decluttered display and uses unique HGS Guidance-to-Touchdown for CAT IIIa approach and landing..
c) IMC Approach Mode This mode also uses a decluttered approach display with Flight Director guidance for CAT 1 or CAT II approach without command flare guidance.
d) VMC Approach Mode
This mode is typically reserved for Non-precision approaches. No guidance cue is provided, just a straightforward Flight path only indication.

7. The Benefits of Head Up Guidance Systems

The benefits of Head up Guidance Systems can be quantified in three main areas:

  • Safety
  • Operational
  • Commercial and economic
  • 7.1 Safety Benefits

    The HGS is a powerful tool for accident prevention. During HGS operations, the pilot is head-up looking for terrain and traffic while monitoring all essential flight data. This 'head up, look out' rather than 'head down, look in' paradigm, means the pilot's attention is directly focused on the most important task - flying the aircraft, whilst being able to monitor all critical flight data. Pilot situation awareness is greatly improved, with the integration of all essential flight data 'head up'. This is particularly helpful at night.

    The unambiguous symbolic presentation of flight path is a tremendous assistance in difficult conditions such as "black holes", circling, VMC and non-precision approaches. The improvements provided by the HGS, for Non-Precision approaches is a particular benefit. Emergency situations such as wind-shear and TCAS can also be more easily handled, with the pilot flying escape guidance while observing external visual references. Specific benefits for the pilot include:

    a) Conformal display of Critical Flight Parameters with:
    - Inertial Flight Path
    - Flight Path Acceleration (Potential Flight Path)
    - Attitude
    - Stall Margin
    b) Constant view of Flight Path and Energy State
    c) Precise Aircraft Control
    d) Stabilized Approaches
    e) Improved Manual Touchdown Precision
    f) Improved Wind-shear Awareness
    g) Tail-strike Avoidance
    h) Recovery from unusual attitudes.

    6.2 Operational Benefits

    Day-to-day operational benefits include the following:

    6.2.1 Improved CAT I minima

    Lower Cat I Minima can be achieved for aircraft equipped with HGS, irrespective of the nature of the facilities at the airport. In all cases, HGS gives direct and quantifiable operating benefits:

    Type of Facility RVR without HGS RVR with HGS
    Full 550m 450m
    Intermediate 700m 500m
    Basic 800m 600m
    None 1000m 700m

    Table 1: Improvements in RVR achievable with HGS

    6.2.2 Cat II operations on Cat I runways

    Head Up Guidance enables Cat II operations to take place on CAT I runways, providing the following improvements are also carried out at the airport:

  • A review of the Airport ILS installation, requiring:
    - a solid state transmitter
    - tighter monitoring tolerances
    - a 2nd IRVR Transmissometer in the rollout zone
    - Beam protection zones enforced
    - Type II obstacle clearance requirements are met.
  • This necessarily implies that approval to operate in these conditions must be given on an airport-by-airport basis.

    6.2.3 Improved Cat III Operations

    HGS is certified for Manual Cat IIIa Approach and Landing Capability with a decision height of 50ft. and 200M RVR. It is also certified for low-visibility take-off, allowing operations down to 75M RVR. This means those early morning flights on foggy days will get off on time, allowing the company to maintains its schedule throughout the day. There is also the potential for Cat IIIb operations via the 'Hybrid' or 'Super Fail Passive' method. In this approach, the pilot utilizes the fail-passive Cat IIIa autoland and the HGS to monitor the performance of the autoland for approaches down to 150M RVR.

    Figure 4: Head Up Guidance in CAT III at 50 feet

    The above enhancements to aircraft operating performance means that the HGS system offers direct and improved airline on-time performance by avoiding the flight disruptions normally associated with poor visibility conditions as well as the 'knock on' effects of such disruptions. Improvements in take off reliability are particularly good. These benefits can be directly quantified by straightforward examination of historical local meteorological conditions and simple calculation of the 'before and after' of installing HGS. These improvements mean smoother and more reliable flight operations, which in turn, mean less disruptions affecting aircraft scheduling, crew rostering etc.

    6.3 Commercial Benefits

    The improvement in landing and take off reliability also translate into direct and indirect commercial benefits. Passengers have a far greater assurance of arriving at their destination despite conditions that hamper most carriers. These improvements in reliability mean improved customer perceptions of the airline and confidence in its operations, which means that customers come back more often. Operating costs are also reduced (crew time, fuel, tyre and brake wear etc.). It is reasonable to expect reductions in diversions and go-rounds and overall reductions in general wear and tear on the aircraft.

    Figure 5: Economic Model for HGS Operations

    Commercial and economic benefits can be calculated in terms of avoiding revenue loss, additional revenue gains (increase in passenger/cargo loads) and gains made in operating costs.

    7. Certifications and OEM Relationships

    The Flight Dynamics HGS has a wide range of certifications and is offered by the following manufacturers:

  • Boeing
    - Standard equipment for the Boeing Business Jet
    - Factory installed on all models of B737 (600/700/800/900)
  • Bombardier
    - Offered on the Dash 8 (100/200/300/400) and
    - CRJ series (200/700)
  • Dassault
    - Factory-installed option on the F2000 & F900EX Embraer
    - Factory-installed option on the ERJ-135 and -145
  • Lockheed Martin
    - Primary flight display for C-130J
  • Flight Dynamics' HGS has more in-service experience than any other commercial HUD System - at over 6 millions flight hours. It has over 3 million flight hours in-Service experience on Boeing 737s. In all, over 25,000 Low-Visibility Operations have been carried out. To date, over 1000 systems have been delivered.

    8. The future

    easyJet will work with both the UK Civil Aviation Authority and local airports to maximize the benefits of Head Up Guidance in its daily operations. This will mean breaking new ground in the UK, as easyJet is the first UK airline to commit to Head Up Guidance systems. Flight Deck operating procedures have to be formalised with the UK CAA. Pilot qualification and crew training for Head Up Guidance requires simulator training and appropriate facilities and training programmes will be established to meet easyJet's needs as its aircraft fleet grows steadily over the next few years. easyJet will continue to seek further improvements in safety, operations and commercial returns as each of these can be passed directly on as benefits to the customer. This means exploring the full potential of Flight Dynamics HGS in all its aspects.

    9. Summary

    The key benefits of Head Up Guidance Systems are straightforward. When integrated on an aircraft, an HGS increases the aircraft's operational capability and significantly improves the Pilot's Situational Awareness. It also improves manual Flight Path Control and provides a platform for further growth for new technologies. HGS offers a clearly quantifiable financial return on investment. easyJet will seek further improvements in its low visibility operations, in taxi guidance, and for take off and landings.

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