“Ladies and gentlemen, this is the captain
speaking. As you no doubt may be aware we have a small
problem with our engines”. This is what it sounds like when a pilot tells
a white lie. The ‘small problem’ that Malcolm Waters,
the captain of cathay pacific flight 780 is referring to, is that one of his plane’s
engines has stopped, and the other one is stuck on high power, and will not slow down. The 309 passengers on board this plane don’t
realise it, but there is a very good chance that in a few minutes, they will end up crashing
into the South China Sea. The only thing standing between them, and
that outcome, is the skill and teamwork of the two australian pilots in the cockpit. With every passing minute, the condition of
their aircraft worsens. Can they make it to Hong Kong before their
engines deteriorate entirely? This is a situation which the pilots were
never trained for, and for which no standard procedure exists. This is the story of cathay Pacific flight
780. On the morning of April 13th, 2010, Cathay
Pacific flight 780 prepared to push back from its gate at Juanda international airport in
Surabaya, Indonesia, for its 5-hour journey to Hong Kong. On board were 309 passengers, and 13 crew. The aircraft being used for the flight was
an 11 year old airbus A330-300, one of over thirty such aircraft in Cathay’s fleet at
the time. The A330 is a popular medium to long-haul
aircraft, with over a thousand in service worldwide in the year 2010. In the cockpit on this flight were two pilots. They had flown this aircraft into Surabaya
the previous night, and had stayed overnight in a nearby hotel. The captain, Malcolm Waters, was 35 years
old, and had been working for Cathay Pacific for the last 12 years. He had over 7000 hours of flying experience,
two and a half thousand of which were on the A330. The first officer, David Hayhoe, was 37 years
old, and had just over 4000 hours of flying experience, 1000 of which were on the A330. Much of his previous flying experience was
with the Australian Air force, where he had served for 11 years. The aircraft still had 9,000 kilogrames of
fuel onboard from when it landed in Surabaya the previous night. The captain ordered the uptaking of a further
24,000 kilogrammes of fuel, for the three and a half thousand kilometre journey to Hong
Kong. The weather on this day was perfect for flying. The forecast was for clear skies enroute,
and as the pilots taxiid their aircraft to the runway, there was no indication that this
would be anything other than a routine flight. The passengers and crew had no idea that they
were in grave danger. Over the next few hours, the pilots would
have to deal with a series of escalating warnings from their on board computers. These would appear benign at first, but would
culminate in a nightmare scenario that they had never been trained for. Flight 780 lifted off from runway 28 at Surabaya
at 24 minutes past 8 local time. The first officer was flying the aircraft
back to Hong kong, and the captain was handling radio communications. The first sign that something was amiss came
during the climb, when the pilots noticed that the engine instruments showed abnormal
EPR fluctuations for the number 2 engine, the one on the right hand side of the aircraft. EPR stands for Engine Pressure Ratio, which
is a measure of the difference in pressure, between the front of the engine and the back. The EPR is used as an indication of the thrust
output of the engines, and the pilots instruments were showing that the engine was having some
trouble maintaining the desired thrust output. The number 1 engine, on the left hand side
of the aircraft, was also giving unusual readings, but these were within a narrower range than
the fluctuations in engine 2. The first indication that this abnormality
might be serious came just before 9am, when the aircraft was level at 39,000 feet. A warning came up on the ECAM, or Electronic
Centralised Aircraft Monitoring system, saying “Engine two CTL system fault”. This system also displayed the message “Engine
two slow response”, meaning that engine 2 would now be slow to respond to movements
of the thrust lever. Captain Waters wanted to clarify the significance
of these warnings, so he contacted Cathay Pacific’s Operations centre for technical
advice. The maintenance engineer on the other end
of the line asked the pilots to move the thrust levers, and see how the engines responded. They did this, and noted that the EPR was
still fluctuating. However, because the other engines parameters
were normal, the crew decided to continue the flight to Hong Kong. About an hour later, the ‘Engine 2 control
system fault’ warning reappeared on the ECAM, along with a warning advising the pilots
to avoid rapid thrust changes. The pilots turned on the engine anti-ice system
to see if this would fix the abnormal EPR readings, but this had no effect. They contacted maintenance control again,
and informed them that the EPR fluctuations had now become larger. They asked whether it was safe to continue
the flight to hong Kong. The maintenance control engineer on the other
end of the line hypothesised that the EPR instability on engine number 1 may be a result
of the flight computer trying to compensate for the instability on engine number 2. In other words, it may in fact just be engine
number two, that had a problem. He advised the flight crew to continue monitoring
the engine parameters, and told them that the Fuel Metering Unit, which controls the
amount of fuel being fed to the engines, would be replaced when they arrived at Hong Kong. The flight continued more or less as normal
for the next two hours. As far as the pilots were concerned, the engine
readings were unusual, but nothing to be concerned about. In their minds, they would soon be landing
in Hong Kong as normal, and it would be maintenance’s job to deal with the engine trouble once they
had parked at the gate. At twenty past 1 in the afternoon, Hong Kong
time, the plane was about 110 nauticle miles from the airport, on its initial descent. From this moment onwards, the crew’s situation
would get progressively worse. As the plane was descending through 30,000
feet, the captain reported hearing a light ‘pop’ sound, which was followed by the
smell of ozone and a burning smell in the cockpit. This was quickly followed by two new ECAM
messages - Engine 1 control system fault, and, critically, engine 2 stall. This second warning about an engine stall,
was particularly troublesome. The flight crew followed standard procedure
for an engine stall, and reduced the power on engine 2 to flight idle, the lowest engine
setting that keeps the engine running. The ECAM then displayed new warnings for engine
1, which read “Engine 1 slow response”, and “avoid rapid thrust changes”. These were the same warnings that they had
received fro engine 2 previously. To compensate for the reduced thrust from
engine 2, the crew pushed the engine 1 thrust lever to the setting known in airbus aircraft
as MCT, or maximum continuous thrust. This is the highest thrust setting the engine
can stay at for a prolonged period of time. However, despite this, engine 1 never reached
this thrust output. Instead, it increased slightly from where
it was, and then decreased back to about 37%. Still over 100 miles from their destination,
the flight crew were now faced with a serious problem. One of their engines was stalling, and had
to be run at the lowest setting, while the other one was running way too slow. Without sufficient engine power, they would
lose speed, and be unable to maintain altitude. They were now on a slow motion collision course
with the South China Sea. The captain called hong kong air traffic control
and declared a “Pan Pan”, which is one step down from declaring an emergency. The pilots had previously carried out an approach
briefing for a normal arrival at hong kong, but they now had to quickly change plan. They briefed for what’s known as a one-engine-inoperative
approach, and also briefed the missed approach procedures in case their first approach was
unsuccessful. Eager to get on the ground before their situation
deteriorated further, they requested a shortened path to the runway from air traffic control,
which was granted. Captain Waters went on the PA system, and
told the flight attendants to prepare for landing. He also briefed the chief cabin crew member,
known as the in-flight service manager, about the engine problems. He then took over from the First officer as
the pilot flying, given the fact that they were operating on one engine now. As the plane continued its descent, the crew
received permission from air traffic control to maintain high speed so that they could
make it to the airport as soon as possible. Having gone through all the relevant checklists,
the captain recapped the situation to the first officer, and asked if there was anything
else that they might not be thinking about. The pilots agreed that they had covered all
the necessary details, however, and that their task now lay in landing the crippled aircraft. It was now looking as if the situation had
stabilised. The plane was about 50 nautical miles from
the runway, and the pilots had briefed for a single-engine approach. At half past 1 in the afternoon, however,
things took another serious turn for the worse. The pilots received a warning that Engine
one had now stalled. Their situation was now critical, and the
first officer made a mayday call to air traffic control, saying “And ah approach, Mayday,
Mayday, Mayday, Cathay seven eight zero had engine 1 and engine 2 stall, ah currently
we require a lower descent, maintaining 8 thousand”. The crew was cleared to descend to three thousand
feet, and they began working through their checklists to deal with the stalled engine. Just as they had done with the other engine
minutes earlier, they moved the thrust lever for engine 1 to the idle position. The aircraft was now essentially a giant glider. If the pilots were going to have any chance
of landing at Hong kong, they had to get at least one of their engines working. They were still in the clouds at this point,
and their speed was steadily decreasing. The captain had disconnected the autopilot
and was now flying manually, trying to keep the aircraft at its green dot speed of 202
knots. Green dot speed, is an airbus term for the
speed which ensures the furthest glide distance when the engines have failed. For this reason, as you may have noticed,
it is the inspiration for the name of this YouTube channel. The captain tested the controllability of
the engines by moving the thrust levers one at a time. If he could get even one engine working, the
plane would make it Hong Kong. Fearing a loss of electrical power if the
engines got any worse, the pilots turned on the Auxilliary power unit. Finally, the aircraft broke out of the clouds,
and the pilots were able to get a better picture of where they were. Air traffic control then advised the pilots
as to how to get to the airport quickly “Cathay seven eight zero, roger, on your present heading,
there will bring you a close base around Lantau island, I’ll advise if this is any..if you’re
too close.” “Cathay 780 roger I can’t see Lantau for
cloud, but we’ve got the island just to, ah, the southeast of the airfield” “Seven eight zero roger, your present heading
is the most efficient to miss the lantau island and still make the right base” “Cathay 780 roger”. Having tested each of the thrust levers, Captain
Waters discovered that engine 1 still responded somewhat, so he decided to use this engine
to keep the aircraft flying. He also set the engine start switch to ignition,
to reduce the chances that the engine would flame out when it was needed most. As the plane neared the airport, it was travelling
too fast for this part of the approach, so the captain started pulling back the thrust
lever for the number 1 engine. However, the engine wasn’t responding. Waters continued bringing the thrust lever
back until it was in the idle position, but the engine itself stayed at a high setting
of 74%. This was a serious problem. Now one engine was stuck on a high thrust
setting, while the other was basically dead. This crew would now have to attempt a landing
faster than anything their aircraft was designed for, and faster than they had ever trained
for. The danger was no longer that they would crash
short of the runway into the sea, but that they would overrun the runway, and end up
in the sea anyway. The First officer told the flight attendants
to prepare for a possible evacuation. The captain then made a PA to the passengers,
telling them that there was, quote, a “small problem” with the engines, and urged them
to fasten their seatbelts. To help slow the aircraft down, the crew extended
the speedbrakes, which are flaps that pop up from the top of the wings and disrupt the
airflow. In order to put more distance between himself
and the runway, and to give himself more time to slow down, the captain started to zig-zag
the aircraft. The plane was not slowing down, however. The overspeed warning began to sound as the
aircraft reached 244 knots, indicating that the aircraft was at risk of structural damage
due to how fast it was going. Air traffic control then cleared the aircraft
to land. At a distance of three miles from the runway,
and at 1000 feet above the water, the aircraft was still travelling at 230 knots, which is
almost twice the normal final approach speed. As they descended through 900 feet, the crew
stowed the speedbrakes. Even though these were preventing the speed
from increasing further, they were too dangerous to leave extended any longer, doing so would
lead to the plane hitting the runway too hard on landing. The first officer asked whether they should
set the flaps to 2, and the captain agreed that this would be worth a try, as it might
slow the aircraft down somewhat, even though it risked damaging the flaps. At this moment the terrain alarm sounded,
as the aircraft was descending rapidly towards the ground while not in a normal landing configuration. The overspeed warning sounded again, as the
aircraft was travelling too fast for the flap setting that had been selected. The captain’s full attention was on making
sure the plane didnt’ impact too hard, so that he could maintain control of it as it
careened down the runway. At fifteen minutes to two in the afternoon,
the aircraft slammed down onto the runway, at a speed of 231 knots, or 426kph, almost
twice the normal landing speed. It bounced, and then hit the ground again,
this time scraping the left engine against the runway. The spoilers deployed automatically, and the
captain deployed the thrust reversers, but only the number 1 engine thrust reverser deployed
successfully. He stepped on the brakes, which reached temperatures
above 1000 degrees celcius, and began to glow. The aircraft continued to skid along the runway,
and was rapidly running out of space. Finally, after a two and a half kilometre
long fight to stop the aircraft, the pilots finally brought it to rest, just 309 metres
from the end of the runway. Everyone on board had had survived the ordeal,
but now there was a new problem. After shutting down the engines, the pilots
looked at the brake temperatures. They had reached the top of the scale on their
instruments, which was 995 degrees celsius. The fire crew which had arrived at the aircraft
reported that they could see smoke and a fire on the landing gear, and the captain quickly
gave the order to evacuate. In the end, 56 passengers received minor injuries
in the evacuation, and 1 passenger fractured and dislocated their left ankle, and required
hospitalisation for surgery. The high-speed landing itself did not result
in any injuries. All 309 passengers and 13 crew survived the
ordeal. It’s hard to understate what an incredible
achievement this landing was. During their approach to Hong Kong, the crew
stayed calm and continued to collaborate in a highly effective manner despite being faced
with a totally novel set of failures for which they had never been trained. They made sound decisions for the entirely
of this ordeal, and safely landed a plane which could very easily have ended up in the
ocean. In recognition of their achievement, captain
Waters and and first officer Hayhoe were each given the Polaris Award by the International
Federation of Airline Pilots associations, which is the highest decoration associated
with civil aviation. As positively as this story turned out, however,
the question remained as to what had caused all this in the first place. How could a modern aircraft like the A330
suffer such a catastrophic failure? The suspicion of investigators quickly fell
on the fuel. When they closely examed the engines and fuel
tanks, they made a shocking discovery. Many engine components were clogged with thousands
of tiny spheres, made of Super Absorbent Polymer material, or SAP. After examining the chemical composition of
these spheres, investigators determined that they could only have one source - the fuel
pump itself, back at Surabaya. Specifically, they found that they must have
come from a part of the fuel pump known as the filter monitor. The filter monitor acts, like the name suggests,
as a filter, ensuring that trace amounts of water and other particles in the fuel being
pumped from the below-ground tanks, do not make it into the aircraft’s fuel tanks. The filter monitor is almost like a series
of coffee filters stacked on top of one another, with each layer filtering out a different
kind of material. Part of this filter consists of a Super Aborbent
Polymer layer, whose function is to absorb any water from the fuel being passed through
it. In absorbing this water, however, this material
swells, and turns into a kind of gel. Here’s a picture from the final report of
what it looks like when this material swells to form a gel. In normal circumstances, if there is enough
water in the fuel, this material swells enough that it actually blocks the filter, and cuts
off the water-contaminated fuel supply to the aircraft. So, why didn’t this happen with Cathay flight
780? How did this material end up in the fuel tanks
of the aircraft? On closer examination, investigators discovered
that this material was not just exposed to normal water-logged fuel. The water in the fuel was in fact, salt water. Salt water is known to reduce the filter’s
naturally ability to shut off when it is overloaded with water. Investigators concluded that as the aircraft
was being fueled, the SAP material in the filter swelled and congealed, due to the presence
of large amounts of water, and that as fuelling continued, the high pressure of the pump pushed
the SAP gel through the filter and into the fuel, where it formed tiny spheres. As the engines ran throughout the flight,
these spheres clogged up the fuel metering units, which control the amount of fuel entering
the engines. This caused them to get stuck on particular
thrust settings. Ironically, this SAP material, the very thing
that was meant to remove contaminants from the fuel, ended up being a contaminant. The person who carried out the aircraft fuelling
did not investigate when on numerous occasions during the fuelling, there was significant
vibration in the hose, as well as an increase in differential pressure (DP) in the fuelling
system. This should have alerted him to the fact that
something was amiss, but he ignored these telltale signs, and simply stopped and restarted
the refuelling each time this occurred, each time pumping more and more saltwater and SAP-laced
fuel into the aircraft’s tanks. As for where this saltwater came from, investigators
found that the refuel facility at Surabaya had recently been overhauled, and several
underground fuel pipes had been replaced— during heavy rain. As the large steel pipes were cut, measured
and then re-sealed, saltwater from an overflowing pond nearby made its way into the fuel lines. The final report made a number of recommendations
aimed at improving the aircraft fueling procedures at Juranda airport, as well as improving the
oversight of fuel quality monitoring. Airbus also inserted a new section in the
A330 pilots Quick Reference Handbook, titled “Suspected engine fuel system contamination”,
which helps pilots diagnose and deal with contaminated fuel. In the end, it’s incredible that the lessons
learned from this incident, were learned without the loss of a single life.
