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The Glass Cockpit

On a recent trip to Nepal, Capt. Lim Khoy Hing chanced upon misleading information touting a flight in a glass cockpit. Here, he dispels misconceptions about what a glass cockpit really is. 

Recently, I visited Nepal to experience the land with the highest mountain on Earth. In one of my previous articles, which discussed some of the most exciting airports in the world, Tribhuvan in Kathmandu was listed as one of them. Flying an approach into the valley and onto the runway at 4,400 feet above sea level in cloudy weather is certainly an exciting experience. Only dedicated airline pilots who are trained and competent are permitted to fly into this destination due to its difficult approach, especially during bad weather.

A Unique Approach

So, why is the approach into Tribhuvan unique for big airliners? Well, it is a one-way-in, one-way-out airport due to the high terrain to the north of the airfield. Bigger planes require more room to manoeuvre in the event of an engine failure. Hence, the stringent procedures imposed for safety reasons by certain airlines.

     To fly in, initially, pilots must approach the runway from the south, staying high then dipping steeply to perform a challenging landing into the bowl-shaped city of Kathmandu. Not only must the pilot stay high, he or she must also maintain the runway approach centre line. On any given cloudy day, isolated thunderstorms sit smack in the centre path. A deviation at this point would put the plane very close to mountainous terrain. Hence, the approach to land is often a rather rough ride on such days as the pilot has very little choice but to charge through the stormy cloud for a short while.

Views of Everest

A traveller to this city would often be harassed by travel agents, promoting fly-bys to Mount Everest. Not surprisingly, I was instantly approached by an agent and handed a leaflet promoting a spectacular Everest flight that offers tourists, who are unable to climb the mountain, a breathtaking view of its peak. Of course, being an aviator myself, I knew that at the time of my visit, the peak would likely be shrouded in clouds.

     There were three airlines offering the Everest flight experience and something that may have easily been missed by non-pilots caught my eye. One airline proudly extolled a British Aerospace-built Jetstream plane that could make a traveller’s Everest experience ‘as reliable as possible’ with its full glass cockpit and Enhanced Ground Proximity System, amongst others.

     This may be misleading information, as it implies that you will be flown in a transparent flying device to fully experience the magnificent marvels of Mt Everest. Unfortunately, this is not quite true. A glass cockpit is not really a space enclosed by glass that allows a pilot to see through all around him. It isn’t like looking out of a bottle from the inside.

The Glass Cockpit

In the past, one would see mechanical gauges and traditional analogue dials on the instrument panels of cockpits. Today, modern aircraft feature electronic instruments with digital displays. This enables data driven by computers (flight management system) to be displayed on LCD (Liquid Crystal Display) screens. Such screens and the earlier cathode ray tube displays are basically made of glass. Hence, the term ‘glass’ is added to describe the cockpit.

     By using computers to manage the flight in a glass cockpit, pilots are able to call up what they want to see, when they want to see it. The advancement in this technology has effectively reduced the need for flight engineers. Planes that used to have three crew members in the cockpit now require only two – a captain and a first officer, which translates to huge savings.

     However, on the flip side, these technological advancements place a greater burden on pilots inside the glass cockpit. For instance, the glass cockpit concept may have confused the pilots of a British Midland Boeing 737-400 on January 8, 1988 in the UK. A fan blade in one of the engines had failed but the crew, guided by the display in the glass cockpit, proceeded to shut down the remaining good engine as well. It was basically the confusing display of the earlier systems, which were often misread, that had caused the error in identifying the proper engine. Fortunately, pilot information has been improved with a better display system, thus minimising erroneous readings.

     On January 20, 1992, Air Inter’s Airbus A320 with this glass cockpit technology flew into a mountain on a night approach to Strasbourg in France all because the pilot operated a knob erroneously. This knob would have commanded the plane to descend either in degrees or a rate of descent. Where the pilots thought they had commanded the plane to descend at an angle of 3.2 degrees, they had actually instructed the plane to begin a 3,200 feet per minute descent in the display system – a far steeper descent rate.

     After this, Airbus redesigned the descent mode display in its glass cockpit.

EGPWS Saves Lives

EGPWS stands for Enhanced Ground Proximity Warning System. This is an improvement over the traditional GPWS that had some limitations.

     The traditional GPWS (Ground Proximity Warning System) works off an aircraft’s radar altimeter – a very accurate sensor of how high the plane is above the ground but only up to 2,500 feet – as opposed to a normal barometric altimeter, which is accurate to above 50,000 feet.

     When the GPWS senses that the aircraft is getting dangerously close to the ground, it alerts the crew. However, since the altimeter is looking straight down and not in front of the aircraft, it would give no warning when encountering very steep terrain such as a vertical rock face.

The Perils of Whiteout

The EGPWS addresses this shortcoming. It can look ahead of the aircraft and see if the potential for a collision with terrain exists. This system, sadly, was not available in 1979 when a DC 10 belonging to Air New Zealand crashed into Mount Erebus in the South Pole.

     Investigations revealed that the main cause of the Erebus disaster was the crew’s inability to see rising terrain ahead, namely Mount Erebus, and not having sufficient visual warning. The crew had suffered a ‘whiteout’, a condition in which visibility and contrast ahead of the pilot are severely reduced by snow as in the case above. The horizon disappears completely and there are no reference points at all. This causes the pilots to have a distorted orientation because of the continuous white cloud layer appearing to merge with the white snow surface. Hence, there’s no visible horizon – to the extent that a pilot may not even know he or she is flying inverted unless he or she looks at the instruments.

     So, how come the crew of the DC-10 did not see the mountain ahead? Well, they were unable to distinguish between the cloud base and the rising terrain until it was too late. If an EGPWS was available then, it would have alerted the crew with this warning, ‘Terrain! Terrain! Pull Up!’ That would have saved the day; alas, this technology was not available then.

Best Time for Kathmandu

In the event that you find yourself planning a trip to this mountainous country, it would be useful to note that the best time of the year would be from December to April. These months denote the drier season when the skies are clearer, which will give you a better view of the amazing peaks. Flying over the mountainous terrain in a ‘glass cockpit’ would be a great experience, as long as you don’t expect the plane to be fully transparent! However, having read this article, you now know that the ‘glass cockpit’ merely houses modern technology that allows pilots to fly even more safely in tricky environments.


Captain Lim Khoy Hing is a former AirAsia Airbus A320 and AirAsia X A330/A340 pilot who also used to fly the Boeing 777. He has logged a total of more than 25,500 flying hours and is now a Simulator Flight Instructor with Air Asia X. In his spare time, he shares his opinion on aviation issues with others. For more air travel and aviation stories, check out his website, ‘Just About Flying’ at www.askcaptainlim.com.