This is the story of logan air 670A. It was the 27th of february 2001, the night
was cold just one degree over freezing or 34 degrees fahrenheit. A short 360-100 landed at Edinburgh airport
after completing the day's flights. The plane taxied to the stands where it would
spend the night. Before heading out for the night they refueled
the plane with 3000 pounds or 1300 kilos of fuel. The plane needed to head back out at 4 am
so fueling the plane now would save time for the next crew. But mother nature had other plans for the
crew and the plane. By 2 am the airport was closed as a result
of the severe weather, the snow pounded the airport and winds of upto 43 knots battered
the planes. By 6 am the crew were told that the airport
would not open for a few more hours, so the crew made the best of the situation. They secured the plane the best they could,
they put straps on the propellers, covered up the pitot tubes and then retired to the
crew room to get out of the biting cold. The wind and snow didn't let up till 10 am
the next day. By 3 pm they were ready to take the plane
from Edinburgh to Belfast, this was a flight that was delayed by the storm. They started the engines but immediately had
some issues , the right hand engine was starting and stopping. The crew tried their best, but soon they had
to ask for engineering assistance, the generator in the right hand engine just wouldn't work. With the engineer made the changes and ran
the engine for about 15 minutes to see if the fix had worked, they ran the engine again
for 15 minutes to double check. The engine worked fine, before the engineer
left the engineer checked the oil levels and checked the surface of the plane for ice,
the oil levels were fine and there wasn't a whole lot of ice on the surface of the plane. With that the engines were started and both
engines functioned for about 20 minutes at the stands with no issues. By 5:10 pm the plane was taxiing to runway
06. As they taxied, they went through the checklists,
icing was a concern that was on the pilots minds. The captain wanted to cycle the landing gear
once in the air to make sure that it was free of ice and slush, that's the kind of things
that they talked about as they taxied. The plane took off, as they had talked about
before the captain cycled the landing gear to get rid of any ice on them, the gears were
retracted and then extended and then retracted again. As the plane breached 1200 feet they pulled
back the engines to climb power as they did. The crew carried out the after takeoff checks
on the plane. The captain asked the first officer to turn
on all the anti icing systems. The captain was busy tuning the to scottish
ATCC and the first officer was busy flipping switches. As the switches were flipped both engines
died. They had just suffered a dual engine flameout
at 2200 feet. The captain immediately put out a mayday call
Quote "MAYDAY MAYDAY MAYDAY THIS IS LOGAN SIX SEVEN ZERO ALPHA WE'VE HAD A DOUBLE ENGINE
FAILURE REPEAT A DOUBLE ENGINE FAILURE", end quote The captain turned the plane towards and coastline
and let the speed drop down to 110 knots, they were descending at 2800 feet per minute. At this point they realized that they'd be
ditching in the water. The first officer made a radio call to let
ATC know that theyd be ditching, but this was never received by ATC. As they got closer and closer to the water
the captain started to pull the nose up. The plane impacted the surface of the water
at 86 knots in a nose high attitude. The plane came to rest 65 meters from the
shore in water that was 6 meters deep. None of the two pilots survived. The first suspect was the weather, the weather
had been very bad leading up to the takeoff but, when they took off the weather was calm. So the weather at the time of the take off
was ruled out. In this case both engines flamed out at the
same time, so something affected the engines together. What if ice blocked a fuel vent? But that theory was quickly dismissed, the
ice in the fuel vent could not block the flow of fuel as the diameter of the pipes were
low, They then looked at the engines for mechanical
faults but this was very unlikely. What are the odds of two engines having mechanical
problems at the exact same time? Tearing the engines down they found no signs
of mechanical failure and the engines were fine. They then looked at the possibility of the
engines icing up, sure the pilots de-iced the plane and the weather was relatively good. But ice could have snuck into the engines. You see the night before the plane was parked
into the wind and the engine's inlets were not covered up, so there is a possibility
that the wind may have driven snow and ice deep into the engine. Well that's the idea anyway, so they built
a test to see if that could actually happen. They used another short 360 to see if surface
winds could reach deep into the engines, they found that 30 knot winds could easily reach
deep into the engine. So on the night before the flight as the plane
braved the storm, the wind was sending snow and ice deep into the chambers of the engine. To understand why this is a problem we have
to look at the engines that's used on the shorts 360. The air is sent through an intake and then
through a mesh and finally it reaches the plenum chamber, this is where ice accumulated
overnight. But the short 360 has anti ice vanes designed
to keep ice out of the engine right? Yes the short 360 has systems designed to
protect the engines from Ice. The air intake has an electrical heating system
to prevent icing. In addition to that it has an inertial separator
in the engine. In the air intake path there are two vanes,
vanes as in moving metal sheets not veins as in veins in the body. The vanes are part of the inertial separation
system, when the anti icing vanes are deployed, they extend into the air flow in the engines
air inlet path. When this happens the snow and ice are redirected
out of the engine and only air goes to the mesh and the chamber. That's how the anti icing system on the short
360 works. On the accident flight they noticed that the
engines flamed out after the pilots engaged the anti ice vanes in the engines. But there's no way that the engine was iced
up in flight, right? I mean the engines were turned on and they
ran for quite some time on the ground. So even if the engine had been iced up it
should have been melted away by the heat of the engine right? Well the investigators found that when the
engine warmed up it indeed did melt the ice, and it turned into slush and it flowed down,
but once it came down it came into contact with the cold wind that was forcing its way
into the engine inlet. At this point the wind was at about 16 knots. Also the engine was run intermittently so
slush accumulated at points inside the engine and the cold wind prevented the residual heat
from the engines melting the slush. So at this point the air intake of both engines
are contaminated with slush. Not good. Once the plane started its takeoff run the
air pushed the slush back, all the way back to the anti-ice vanes. Now after the plane had taken off, as it was
climbing the captain knew that theyd encounter some icing in the clouds and so he asked the
first officer to enable the anti icing vanes. With slush pushed up against the vanes, when
the vanes extended it dug into the slush kind of like a snow plough and the vanes and the
slush drastically reduced the air flow into the engine. With the slush disrupting the airflow into
the engine, the engines flamed out. Now you might be asking, how do we know that
this is exactly what happened? Good question. For one each engine failed exactly 3.95 seconds
after its corresponding anti ice switch was flipped. On top of that the motor that drove the vanes
created a very specific kind of electrical noise that the CVR picked up, they compared
what they heard on the CVR to their test bench and both samples matched up perfectly. So they know that the vanes were working that
day. A bit of ice in the engines that no one could
find caused the flameouts. So how could this have been prevented? Well plugs for the engine inlets would have
done the job, it would have prevented the ice and snow from getting into the engine. The manufacturer’s maintenance manual called
for the engine inlets to be sealed up during times of rough weather, but the operator's
manual didnt call for that. The operators manual said that plugs had to
be used if the plane was parked for quote “any length of time”, that's pretty vague
and was generally interpreted to mean an overnight stop, remember as per the original schedule
the plane was supposed to go back up in a few hours. But even if they wanted to secure the engines
the airline didnt provide the crew with plugs and they were not readily available at the
airport. It seems that no one thought of ice contaminating
the engine in this way. In addition to that they found loopholes in
the training of the pilots, in case of a water ditching the pilots were trained to use an
emergency hatch and life vests but this wouldnt really work if the cockpit was submerged as
was the case this time around. Also the operations manual didnt have a procedure
that the pilots could follow, so quote “they attempted a ditching at the slowest possible
speed and attained a similar attitude to that recommended for the power available case”
end quote. Its very concerning that something as simple
as how a plane is parked can lead to complications and accidents, How do you think accidents
like these can be avoided, do let me know in the comments below.
