The Flying Engineer in 2009 got a rare opportunity, thanks to a wonderful crew, to jump seat on a Mandala Airlines A320 from Jakarta to Surabaya. This article describes in succulent detail everything that is performed in the cockpit, while smoothly integrating explanations of the various avionics and systems that were relevant to the flight. Sit back and enjoy the flight as it unfolds right in front of you, from an experience first hand.
First Officer Firman communicating with Air Traffic Control as we fly over tropical Indonesia
Signs of a delayed flight were everywhere. Kids and teenagers running around, Zone 2’s staff desk was approached every now and then by an anxious passenger. “How much longer?”
April 2009 witnessed the opening of Terminal 3 of Soekarno Hatta International Airport, making it the newest. Home to two low cost carriers, Indonesia Air Asia, and Mandala Airlines, the terminal sees primarily two colors: red and blue, respectively.
And today was to be blue, although events of the morning had made it Indonesia’s “Black Friday”, the black responsible for the delay of Mandala Flight number 276. The sun at 5 ’o’ clock, sinking through clouds of white swimming in a hazy blue background, started lending objects a mild tinge of gold.
A photo of PK-RME, an Airbus A320-232
Passing under the white nose of PK-RME, I climbed up to the cabin, turned left, and was welcomed by Captain Henry Saut Maruli, a well built man sporting kempt hair, and an air of professionalism sprinkled with a great friendly attitude. Turning to the right, I greeted first officer Firman Joseph, who diligently was scribbling numbers on the “tray” which only Airbus aircraft can sport. And boarding had begun.
This was the moment waited for: Six months of working on the Airbus family of flight management systems at a major North American avionics manufacturer, assimilating concepts very deep, some previously unheard of; all to be seen in action in the flight deck of a brand new Airbus A320, bought directly by Mandala from Airbus Industrie. This was the ultimate professional temple I was stepping into.
The load sheet came in with 55.6 tonnes Zero Fuel weight, and a CG at 31.5% of the mean aerodynamic chord. That made the tail heavy, and Firman manually turned the trim wheels to counter the CG shift. To fly this sector, from Jakarta to Surabaya, 2.7 tonnes of fuel was earmarked, for a flight time of 1 hour and 3 minutes over 377 nautical miles. 0.1 tonne of Jet A-1 was the route reserve, corresponding to 5% of the trip fuel. Our alternate airport was Bali, requiring 1.3 tonnes for a 33 minute diversion flight in case bad weather or airport closure at Surabaya’s Juanda airport prevented RI276 from landing at our destination. With other fuel figures, the block fuel came up to 7.5 tonnes, lending the aircraft a take off weight of 63.3 tonnes. 200kgs were to be burnt off during taxi.
After the pilot’s safety briefing, the observer’s seat was slid along tracks that ran from the Circuit Breaker Panel behind the first officer. The compact structure was unfolded, and ready to be seated on. 5 seat belts were fastened to a central lock, 2 across the shoulders, 2 around the waist, and one from the seat passing between my legs, all meeting at the central lock at my naval.
“Start sequence 2-1”, and engine #2 (the right engine) started coming to life. The Engine page on the Airbus A320 showed the dead left engine in amber, as the right hand IAE V2500 engine had just started. Even the engine start on this marvelous aircraft is automatic. As Captain Henry rightly put it, “We can now go to sleep”. He was joking, of course, thankfully.
Two types of engines can power the A320: the CFM56-5, or the IAEV2500. Neither of the engines is from a sole company, but rather from consortiums. As for International Aero Engines, from front to back, the fan and low pressure compressor comes from Japanese Aero Engines Corporation, the high pressure compressor from Rolls Royce, the combustor and high pressure turbine from Pratt and Whitney, and the low pressure turbine from MTU Aero Engines. International indeed. With only 1 unit of air burnt for every 6.4 units of air sucked in, “IAE ensures the V2500 is able to deliver world-class reliability, the lowest fuel burn and best performance retention. The V2500 can also boast the lowest total emissions and environmental leadership in its class along with the lowest cost of ownership.” With an overall back to front pressure ratio of 29.8, 25,000 pounds or 11,363 kg of force is capable of being produced by each engine.
The fan of a V2500 on an Airbus A320
In an IAE equipped aircraft, engine readings are not as intuitive as the CFM counterparts. With CFM A320s, the fan thrust, or N1, is displayed as a percentage of maximum thrust. However, in IAE equipped aircraft, readings are in terms of the pressure ratio developed by the front most section of the engine: the huge air intake fan that is readily visible to all on the ground. This huge fan alone can develop a pressure ratio, or EPR, of 1.6.
With push back complete from Apron G, and a wave
to the ground crew, Capt Henry advanced the throttles mildly for taxi. The ride was bumpy. Meanwhile Firman completed the checklists. Control surfaces were checked for normalcy. We were asked to taxi and line up on runway 07R, perfect for our east bound route.
Every major airport has a SID, or a Standard Instrument Departure. This is to ensure that aircrafts follow predictable flight paths in an organized manner, simplify clearance deliveries from air traffic control, and provide better separation between arrivals and departures, such
The Island of Java, Jakarta (origin, left) and Surabaya boxed in red (Destination, right)
that air traffic flow is optimized. Mandala 276 flies to Surabaya via W45, which flies through waypoint KASAL, radio beacon CA, waypoint PIALA, radio beacon ANY, radio beacon BA, waypoint NIMAS, before kissing terra firma at Surabaya. Since KASAL is our first waypoint, we would like to choose a SID that would take us to KASAL. A quick look at the charts reveals a SID termed PURWAKARTA2C from runway 07L/R would take Mandala 276 to W45’s KASAL.
Purwakarta 2 Charlie Departure
Control Surfaces on an A320
The flaps were set to 1+F, a configuration that extends both the flaps and the slats from the wings, by the least increment. The advantage of using flaps and slats is that the aircraft stalls at a lower speed, thereby allowing the aircraft to lift off at a lower speed, consequently taking up less of the runway for the take off roll, something that wouldn’t be a problem when operating off long runways.
“Cleared for take off, Mandala 276”, read back Firman, while Henry advanced the throttles to a position less than that which would command maximum thrust.
Lined up on runway 07R, ready for departure
Simple laws of motion dictate that a higher force leads to a greater acceleration, for a given weight. And a greater acceleration corresponds to a shorter distance for take off. The flip side of this shorter takeoff is that the engine is operated at its limits. So severe is the operation that if the engine is run at maximum thrust for ten minutes, the blades would begin to melt.
A jet engine produces exhaust gas temperatures of nearly 600 degrees centigrade. Normally, higher the thrust required, greater is the fuel burnt, and hence higher the temperature. When the engine is specified an outside air temperature of a particular value, it can be asked to command a thrust such that, the exhaust gas temperature, or EGT, for a particular thrust, plus the outside air temperature (OAT), equals the maximum EGT, of say, 600°C.
A quick mind will immediately see the benefits of such a procedure. A long runway would not require the aircraft to take off in a short distance. This would, in turn, not require the aircraft to take off with full thrust, but below full. This would lead to “flexible” thrust. By specifying an OAT that is greater than the actual OAT, the engine is fooled into delivering a lower thrust. And hence, our flexible take off thrust that day, commanded an EPR of 1.301, as against the maximum of 1.6, by specifying an OAT of 68°C, while the actual OAT was 31 degrees. The immediate effect of this is saving engine life.
Today’s tough competitive environment forces airlines to consider operational costs in every facet of their business. The cost incurred by a flight comprises of fuel cost, time related costs, and fixed costs. In the 1970s, when fuel prices surged, airlines were worried about fuel consumption, with fuel costs accounting for no less than 45% of operating costs. Gradually, as prices eased, airlines began to encompass other costs into their equation, the only two variables being fuel cost and time related costs.
CI 39 mentioned in the FMS interface
The tricky part lies in the fact that attempting to reduce fuel consumption adversely affects time related costs, and vice versa. The faster the aircraft flies, the more is the fuel consumed due to extra drag, but shorter is the time of travel. This way, time related costs such as hourly maintenance costs, flight and cabin crew costs per hour, and marginal depreciation or leasing costs are saved upon, but the important point lies in incurring the minimum cost for the trip. And the concept of Cost Index, or CI, was born.
Cost index is the cost of time over the cost of fuel. A cost index of 100 would imply that 100 kilos of fuel is as expensive as 1 minute of flight time. A higher cost index emphasizes savings on time related costs, while a lower cost index saves on fuel. For a given place, the cost of available fuel is weighed against the cost of time incurred, and that cost index, which would result in the least operating cost, due to both time and fuel, would make sense to the airline’s operations. And Mandala 276, for that day’s Jakarta-Surabaya sector, was flying with a cost index of 39.
The aircraft was accelerating down the runway, pinning me against my seat. Firman kept a close watch on the airspeed, while Henry was rapidly looking outside, and inside on the displays. On approaching 154 knots, Firman called out “V1”, indicating that the pilot must, at that very instant, decide to abort or continue with the take off. Since all systems were normal, Henry decided to go ahead with the take off. At 155 knots, Firman called out “Rotate”, indicating that Henry could safely pull back on the stick, and get airborne.
The most remarkable feature anyone would observe, about a new generation Airbus cockpit, is the absence of control columns between the legs of the pilots. What appears in all Boeing and conventional commercial aircraft as a pipe and a semi-steering wheel, known as the control column, is found in the Airbus as a small stick to the left of the commander, and to the right of the first officer. Pilots who move onto the new generation Airbus aircraft: A318/A319/A320/A321/A330/A340 or A380 from more conventional aircraft do express their initial feeling of an awkward void that represents the free space between the pilot’s seat and the front panel. However, very soon, most are all praises for the new technology.
Normally, at V1, the pilot lifts his hands from the throttles, and holds both the sidebars of the yoke. In an airbus, the hand on the throttle has nowhere to go, but on the lap. A very awkward feeling, initially.
Absence of the control column
The new generation Airbus aircraft differ from most aircraft in that these aircraft use “Fly by Wire” technology. The inputs by the pilot are neither mechanically nor hydraulically linked to the control surfaces. Movement of the small stick causes electrical signals, representative of the stick’s position, to be generated, and these signals, after being processed by computers, move the control surfaces by means of hydraulic pressure. Because there is a computer between the pilot and the control surfaces, there is the provision of limiting the pilot’s input, such that, what he commands may not be what the aircraft performs. And this, ladies and gentlemen is the wonderful feature that prevents modern Airbus aircraft from reaching dangerous states.
The stick: inputs to the Fly By Wire system
Airbus Fly By Wire aircraft are a result of military technology that, after exhaustive convincing, saw itself successfully, for the first time in civil aviation, in the form of the Airbus A320 flight controls. Pilots flying the A320 are free to operate it as normal, but the flight envelope protection prevents the aircraft from performing maneuvers outside its performance limits. With fly by wire technology, the aircraft cannot, under normal circumstances, bank the aircraft by more than 67 degrees from the vertical, pitch up by more than 30 degrees, and pitch down by more than 15 degrees. In addition to these, all maneuvers are limited in the stress induced to the aircraft to 2.5G. Besides, in the unlikely event of the aircraft approaching a stall condition, the aircraft, lowers the nose automatically and commands full thrust. In the event of over speeding, the aircraft raises the nose gently. In all these cases, pilot input is smoothly over-ridden, in the interest of safety.
Mandala 276 was airborne, and Firman raised the landing gear. The aircraft was climbing like a home sick angel, with the capital Jakarta slipping below us.
The planned route in blue and the route flown up to radio beacon CA in green.
Firman requested for a direct routing to CA, instead of following the longer PURWAKARTA2C departure.
Since there was no conflicting traffic, ATC agreed.
The aircraft turned right, headed to CA, skipping the initial part of W45. The reason for such a request was obvious: flying a shorter distance saves fuel. Before we could enjoy the view, the Master Caution sounded. Engine #2 bleed had a fault.
Engine #2 Bleed Fault
An engine can “bleed” some of its pressurized hot air from the compressor, which can be used for temperature control, and pneumatic pressure, for the air conditioning packs and cabin pressure. An in-operational bleed may prevent the aircraft from climbing to its cruise altitude (which for this flight was Flight Level 370 or 37,000feet MSL), due to the inability of a single bleed in providing sufficient pneumatic pressure to handle the required cabin pressure for passenger comfort. For our flight, the cabin was to be maintained at a pressure altitude equivalent of 7450ft. At 37,000ft MSL, the outside pressure is 215hPA, while at 7450ft, the pressure is 768hPA. To maintain a pressure difference of 553hPa on one engine’s bleed is not possible, and hence the aircraft must descend to a lower altitude, such as 22,500ft, before the APU’s bleed may be used to compensate for one defunct bleed system, and be able to support the desired cabin pressure.
Most jet aircraft have one more jet engine than is visible to the eye. For example, an Airbus A320, which is a twin engine aircraft, has a third, smaller engine at its tail. This jet engine, however, is not used for propulsion, but rather for pneumatic and electric power when both the engines are shut off, and hence known as the Auxiliary Power Unit, or APU. Most of the time, engine start on the ground takes place with the APU’s pneumatic pressure. The APU is limited in its altitude of operation to 22,500 feet, when pneumatic pressure is demanded from the unit to supplement one engine’s pneumatic pressure. In case both engines’ bleed malfunction, the aircraft needs to descend to 10,000ft: an altitude that the human body can cope with. However, if the APU is to compensate for the loss of both the engine bleeds, the aircraft can stop short its emergency descent at 15,000ft. In the event of using the APU for electrical power alone, the aircraft need not descend below 25,000ft MSL.
Thankfully after repeated on-off cycles, the bleed functioned normally, much before reaching our cruise altitude of 37,000 feet.
One may wonder why the aircraft, in the first place, needs to fly at such high altitudes. Firstly, the density of air decreases almost linearly with altitude. Secondly, a higher density air would offer more drag to an aircraft, keeping the aircraft from flying fast, and at the same time, forcing the engines to work hard to produce a high thrust to overcome the drag. In such a case, both time and fuel wastage is high, defeating the economics of flight operations.
With so many parameters to manage, in order to realize economical operation, pilots require a tool to meet airline goals. Computers made this possible with the Flight Management System, or FMS.
The whole flight, and the navigation along the ground, is taken care of by the Flight management System on board the aircraft. The Flight Management System (FMS) integrates sensors, systems, and displays to give economy with a minimum workload. The FMS helps the pilot create the flight plan, optimizes the flight plan for winds and operating costs, fills in the details, and suggests the most economical climb profile, cruise altitude, airspeed, step climb, and descent. Our climb speed, corresponding to the entered cost index of 39, was calculated by the FMS to be 303knots indicated airspeed, until reaching Mach 0.78, and then climbing at Mach 0.78 till 37,000 feet.
Cross Over Altitude
The dual speed confusion is sorted out through this simple explanation. As the aircraft rises, the air gets thinner and thinner, and so the air speed sensors record a speed which is, in reality, much lower than the actual speed of the aircraft through the air. In this process, an aircraft flying higher and higher with the same indicated airspeed will start flying closer to the speed of sound, which will adversely affect safety (through structural stress) and economy (due to drag associated with compressibility effects near the speed of sound). A reliable means of expressing the speed of sound through the air is by comparing the speed of the aircraft to the speed of sound through the air in which the aircraft is flying. This ratio is known as the Mach number, after the physicist and philosopher Ernst Mach. Thus, the aircraft climbs at an indicated airspeed of 303knots, till the Mach number reaches 0.78. At Mach 0.78, the aircraft will switch over to Mach as the speed reference. The altitude at which this occurs is known as the cross over altitude, which, for the 303-0.78 pair, is around 29,000ft.
A peaceful evening, the relaxed atmosphere made possible by the automation.
Thankfully, all this is automated in modern day aircraft. The pilot need not do anything but monitor flight progress and scan the systems, allowing the crew to detect a fault early and execute corrective measures in time. In the meanwhile, the FMS does all the hard work: numerous complex calculations that guarantee hassle free smooth navigation, flight economy and accurate predictions for safety. The result of these calculations produce guidance targets which are fed to the auto flight control system, which interfaces to the flight control computers mentioned earlier, enabling the aircraft to fly automatically without much pilot intervention, from point A to point B, in the safest, and most economical manner.
The primary role, however, of the flight management system, is to ensure navigation integrity and accuracy. Economy and predictions are meaningless to a lost aircraft. And in the result, safety is compromised.
Approaching ANY, a VOR, or a Very high frequency Omni Range type of a radio beacon used for air navigation, pilots Henry and Firman are able to “see” the radio beacon on electronic map displays in the cockpit, known as the Navigation Displays, or NDs. The data source for the electronic map is the FMS, again.
PK-RME, Mandala’s Airbus A320, has two Global Positioning System receivers on board. These independent receivers receive signals from satellites, with the help of which the position of the aircraft may be determined. The figure of merit, or the accuracy on our flight was shown to be 10M, or 10 meters. Just to highlight the level of accuracy, the first GPS displayed a position of 06° 31.9’S/108°04.2E, while the second one displayed 06° 31.9’S/108°04.1E, representing 0.1 minute of displayed longitudinal disagreement. Near the equator, 1 minute of longitude and latitude correspond to 1 nautical mile, resulting in 0.1NM of displayed disagreement. This was when both were receiving signals from 10 satellites, while the absolute minimum for a stand alone GPS to work is 4 satellites; the excess 6 satellites resulting in a good GPS RAIM (Receiver Autonomous Integrity Monitoring).
Apart from the GPS, which hasn’t gained worldwide acceptance as the primary means of air navigation due to the complete dependence of operational accuracy and availability on the United States Department of Defense, aircraft are also fitted with Inertial reference Units, or IRUs, which double integrate sensed accelerations over time to determine the aircraft position relative to the starting position. It is for this reason that parking bays have coordinates, so that the IRU can be “told” what its initial position is, before the aircraft is moved. However since this is a unit that works purely on dead reckoning, the errors accumulate over time, unless the position is updated on a periodical basis. And this is where the FMS come in, as the guardian of navigation integrity.
Navigation Accuracy HIGH: Last line of the display. Note also the Optimum altitude as OPT FL365. The flight ident is also visible: RI276
The FMS updates the position of the IRUs with information derived from radio beacons in range. The position calculated by all 3 IRUs (the case with all Airbus aircraft; Boeing 737s have 2 IRUs) are combined to form a “mix IRS” position. The FMS then mixes the position derived from the two GPS and the mix IRS to form a GPIRS position, which is very accurate. The accuracy is so high that the estimated position uncertainty, or EPU on our flight was 0.08NM, while the Required Navigation Performance, or RNP (A statement of the navigation performance expected of the aircraft navigation system) was expected to be 2 Nautical Miles for W45, this meaning that the aircraft must be within 2 nautical miles, on either side of its track, and the estimated position uncertainty of the navigation system must be within these limits. Since our estimated position uncertainty was very low, our accuracy was HIGH.
GPS Navigation Air Data Inertial Reference System (GNADIRS), displaying the aircraft’s position.
But such is not the case, as always, especially with aircrafts fitted with IRUs without GPS. On 1st January, 2007, Adam Air 574 disappeared between Surabaya and Manado, both cities on adjacent islands of Indonesia. Indonesia’s archipelagic layout and minimal radar coverage dictate the normal method of combating IRS drift-rates en route is via a manual or auto-update of the FMS from a VOR and DME (Distance Measuring Equipment) navaid somewhere along or adjacent to the planned route.
Unfortunately, VOR radials are only accurate to within 4 degrees and are subject to bending and scalloping, particularly when high terrain intervenes. For many Adam Air routes, distant fixes taken on the beam will be less accurate because of this. Other accuracy wild cards include the frequency with which pilots update the FMS and the integrity of the geographic coordinates inserted at IRS initialization on the ramp. All these biasing factors presume the twin IRS itself is functioning within laid-down drift-rate limits. And when the drift rate is excessive, or the updates erroneous, an event similar to Adam Air 768 could occur- another Boeing 737, which, in February 2006, ended up at Tambolaka, some 400 nautical miles away from its destination of Makassar, Indonesia. That “lost” episode was attributed to the vagaries of haphazard VOR updating 
As the sun moves away. View from the Commander’s side, with the left wing tip visible
Cruise at 37,000ft over Indonesia in the evening is beautiful. With the aircraft and the sun going different ways, darkness sets in faster, and the horizon appears like a sea of cotton topped with molten gold. Before long, the surroundings got bluish black, and it was time to turn on the panel, flood and integrated lights in the cockpit. The A320 cockpit now wore a different look: from a blue paneled bird during the day, to a light brown, almost golden red panel with every switch and knob sporting its own lighting, in the dark. Henry and Firman were barely visible, with most of the attention being grabbed by the beautiful LCD displays.
Henry pointing out to few volcanoes enroute.
While FL370 was the cruise Altitude of Mandala 276, the FMS initially showed an Optimum Altitude of FL365, or 36,500ft. For a given speed, the lift decreases as the aircraft climbs higher and higher. This can be combated by making the aircraft fly faster, or by increasing the angle at which airflow meets the wings, both of which induce greater drag on the aircraft’s motion, which must be combated by an increase in the engine thrust, resulting in a greater fuel burn. Thus, for a given Cost Index, the Optimum Altitude is a function of the weight of the aircraft: The lighter, the higher. As the aircraft flies, the weight reduces due to the fuel burnt off, allowing for a higher optimum altitude. And a higher altitude for a lighter aircraft is desirable: due to the lower density at higher altitudes which induce a lower drag on the aircraft, for the same speed, reducing fuel consumption. During the course of 276, it wasn’t long into the cruise before the optimum altitude read FL370. We were then flying at the most economical altitude corresponding to CI 39. And at the Optimum Altitude, the specific range (SR), or the distance covered per fuel unit, is the best for the given CI.
For the A320-232, flying 2000ft higher than the optimum altitude slaps a SR penalty of 1.4%, while flying 2000ft below causes a 2.1% SR penalty. 6000ft below the optimum altitude, and the airline accountants would be crying due to the 12% penalty in specific range. In the airline business, it all comes down to the dollar.
The White Arrow, indicating top of descent, seen between the two innermost arcs, along the flight path, on the Navigation Display, or ND.
A small white arrow on the electronic map, known as the Navigation Display, indicated the optimum point at which the aircraft should begin its descent. Firman requested for descent from Air Traffic Control 30 seconds prior and Henry began Mandala 276’s descent into Surabaya. All by the autopilot, of course.
The engines whined down, and the
A small pink dot on the 2nd vertical tape from the left, indicating the vertical path deviation
aircraft began descending at idle thrust at 2800feet per minute. A small pink ball on the primary Flight Display (PFD) indicated that the aircraft was 440ft below the ideal descent path. A small lightning bolt drawn on the Navigation Display indicated the point where the aircraft would intercept the FMS computed descent path.
Soon, the lightning bolt was gone, and we were back on the path deemed economical by the FMS. At the same time, the cabin began repressurizing at a schedule such that, at the destination, the outside air pressure would equal the cabin pressure, facilitating the safe opening of the cabin doors.
Most of the descent was performed at idle thrust, which speaks well about the economical management of the flight by the 320’s FMS. The aircraft reached the deceleration point, a point at which the aircraft starts slowing down, to facilitate the extension of flaps.
The Airbus A320 has 4 flap configurations, which are manually extended sequentially. Each wing has 2 flap surfaces, and five slat surfaces, which are electrically controlled and hydraulically operated. Flaps extend outward, from the trailing edge of the wing. Slats extend downward, from the leading edge of the wing. When slats are extended, they smoothen the airflow over the wing, even when the wing meets the airflow at high angles, thus preventing airflow separation, which would otherwise lead to a stall. Flaps effectively increase both the curvature and the surface area of the wing, leading to a high lift even at a low speed, allowing the aircraft to land in a slow and controlled manner. The flap lever selects simultaneous operation of the slats and flaps. Henry opted for configuration FULL for landing, which extends the flaps to 40 degrees down, and the slats to 27 degrees, both from the horizontal referenced to the wing surface. The FMS calculated approach speed, which would be maintained by the auto flight system, for the computed landing weight and flap configuration was 135kts. Each time the next flap position was selected, the drag increased, and the engines surged ahead to maintain the speed, before reducing the thrust to match the automatically targeted lower speed for the given flap setting. It was a nice feeling to be pinned to the seat every now and then.
About 30NM from the runway, air traffic control vectored the aircraft slightly to the left, due to traffic, spoiling an otherwise perfect straight in approach to the runway, which runs from west to east. This made our flight deviate nearly 10NM left of track, before Henry turned right, on ATC’s instruction to get back on course. Henry was mildly upset, as the deviation would translate to more fuel burnt for this flight under his command. It’s a matter of professional pride for pilots to burn the least fuel on a trip.
About 10Nm from touchdown, Henry had got the aircraft aligned with the runway’s course, ready for the landing. The landing gear was lowered, and checked by three lights reading green. The city of Surabaya was sparkling in the darkness: cars, buildings and houses.
Red flashing lights in the cockpit, the Master Warnings, blinking when the autopilot was disconnected. Surabaya’s runway 01 is in sight.
“Cleared to land on 01”, read back Firman, and the autopilot was disengaged, with an aural “cavalry charge”. Henry was now flying the A320 manually, and as we approached the runway, with the runway approach lighting system running under us, objects on the ground starting to get bigger, and faster. The automatic system that commands the amount of thrust required to maintain a target airspeed, known as autothrust, was disconnected at 10 feet above the runway, on hearing the famous synthetic “Retard, retard” voice. Then followed the silence: engines cut to idle power, and the aircraft floating few feet above the runway, touchdown an unknown second away. A mild thud, heads moving left and right, and there ensued a smooth touchdown.
The braking action in an aircraft is contributed by air drag, wheel brakes and engine “reverse” thrust. Some aircraft engines have the capability of redirecting the engine’s fan air flow such that a force is applied in the direction opposite to aircraft motion, leading to a greater deceleration. With most bypass engines, such as the V2500, this “thrust reverse” is achieved by placing vanes in the direction of the bypass airflow in the engines, and opening slots through which the air is expelled at 45 degrees towards the front. Since 80% of forward thrust is generated by an engine’s bypass air, the reversers are pretty powerful. The air drag is contributed by the flaps and spoilers, the latter being wing panels that rise up from the upper surface of the wing, and face the airflow. Airbrakes apply brakes on the main wheels below the wing. In the effort to cut fuel costs, reversers are not used, unless required.
Henry used no reversers, as the runway was long enough for the aircraft to be stopped by the automatic brakes which were set to medium intensity. Soon, we vacated the runway from left onto a northerly taxiway.
Henry maintained the aircraft along the taxiway centerline, until he could see the parking gate he was assigned, and the marshal who kept indicating, by means of glowing directors, the aircraft’s parking slot. Turning right, PK-RME slowly made its way into the gate, before parking brakes were set and engines cut off. The APU had been turned on by Firman during the taxi, and all the systems and air-conditioning were now running on the APU’s power.
Mandala 276, another everyday flight connecting the two major cities of Indonesia, came to an end. For crew members Henry and Firman, it was just another day at work, just another sector. In thirty minutes, this aircraft was ready to fly to its next destination, with Firman at the controls. Air traffic control was not able to identify the aircraft as the flight it came in: It had already changed its identity. PK-RME was ready to fly back to Jakarta as Mandala 277.
For making this article possible, and proof-reading, and checking facts:
Captain Henry Saut Maruli
First Officer Firman Joseph,
First Officer Ashish Tandon
First Officer Depak SD
First Officer Abhilash Sagi
Capt Raj Menon
Air India Express
Captain Hari Shankar Das
Crossover Altitude Image
Aircraft Specific Data
Mandala A320 picture