This video is sponsored by Blinkist Plane crashes have occurred over the
years for many different reasons. Some of those accidents have paved the
way for major changes in the industry. Others such as the case with the
accident we’re discussing today, the problem can be found in what may appear to
be the simplest of issues. Austrian Airlines Flight 901 when looked at in hindsight, can
show how effective cockpit communication is key for the safe operation of a plane. And
how failure to crosscheck can end in death. -sponsor- The date was September 26th, 1960. A plane
operated by Austrian Airlines was making a routine trip between Vienna to Moscow, then capital of the
Soviet Union. Airspace involving the Soviet Union was complicated and often restricted in many
areas for many airlines. Moscow’s Sheremetyevo airport was one of only a few airports in
the USSR that allowed western air carriers. Flight 901 left Vienna that Monday afternoon
and made a stopover in Warsaw in Poland. By the time the plane left Warsaw it was carrying
37 passengers and crew. The plane itself was a British built Vickers Viscount. It’s a plane
we’ve talked about before but for a quick recap. The aircraft is often credited as being
the world’s first Turboprop. The four-engine plane was popular for its time with well over 400
units built in the years between 1948 and 1963. The Viscount though has certainly
had its fair share of incidents, but the plane is still remembered fondly
by its former pilots and passengers. Many operators across the European Continent flew
the Viscount and Austrian Airlines was among them. Up on the flight deck that day was 36-year-old
Captain Erwin Wilfing and 39-year-old First Officer Ferdinand Freisleben. The plane
had arrived in Warsaw 35 minutes late but the departure for the second leg was pushed
back further due to poor weather in Moscow, their expected arrival time became
Quarter to Ten in the evening. To unpack this accident, we need to more closely
examine the approach phase. When it comes to landing an aircraft, it’s a delicate process and
pilots need to run through several checklists to configure their aircraft. To set the scene in
the case of Austrian 901, it was night-time, and it must have been a busy evening at Moscow’s
Sheremetyevo airport as controllers would give flight 901 two sets of holding instructions.
A normal procedure at larger busier airports. At the time, Sheremetyevo airport had just
one runway. This one… The descent into the airport was initiated whilst inside the
holding patterns and Flight 901 was given approach instructions for runway 07, the
“straight in” approach from the west. One part of the process of preparing any plane for
landing is that the cockpit instruments should be reviewed and synchronized as needed, and one of
the most important cockpit instruments is the altimeter. So, we need to talk a bit more about
the altimeter. Bear with me, we’re about to go on a bit of a tangent. You already likely know
what the altimeter does, it measures altitude. On the surface, altimeters are basic
instruments and often easy to read and even for non-pilots can be easily
interpreted. In western countries, we adopted the measurement of feet to be the
standard when it comes to altitude in aviation. It was Russia, Warsaw pact countries and China
for example that went with the metric meter, these countries have now since
adopted the foot measurement. To get the actual altitude readings, altimeters
are connected to the aircraft’s static port. The changes in air pressure as a plane climbs or
descends drive a barometer inside the instrument. The barometer being the device
that measures air pressure. That information is then
displayed on the altimeter. So, this next part is where it gets a bit
confusing, and I’ll do my best to keep this simple. Obviously, air pressure changes on
the ground, day to day, even hour by hour. So, every altimeter on a plane has some way to
calibrate the altimeter setting to adhere to these changes at ground level. An adjustable Barometric
setting is usually displayed in a small window on or very near the altimeter itself. It is there
to input what is called the Barometric Reference. Pilots before a flight for example, would match
the barometer with the outside pressure so that their altimeter should be calibrated to read
the correct altitude of their departing airport. A lot of the time, altimeters may be
calibrated with reference to sea level, something that pilots call “QNH” “QFE”
can also be useful and is the calibration to display actual height above the ground.
Basically, setting the altimeter to read 0. To give an example, I’ll show you the airport
that I personally know the most about, Newcastle Airport in England. This airport is roughly
260 feet above sea level. If a pilot wanted to calibrate their altimeter to read 260 feet,
they would input the QNH in that Barometric scale. If a pilot wanted their altimeter to display
0, they would input the QFE, which would be a considerably lower Barometric Reference.
This works in the air too, it’s common for pilots to adjust the altimeter setting in flight.
Say there is a new weather report with a change in air pressure reported. Pilots adjust the
altimeter accordingly for an accurate reading. In most of the world, the measurement to record
air pressure on airplanes is known as HectoPascal. This is a metric unit. HPA is pretty much the
same as what one may already know as the millibar, they are the same unit. In the United States
because, of course, they use a completely different measurement of Inches of Mercury. A
measurement that often needs to be converted. So, when a pilot inputs the QNH, QFE
or what we’re about to talk about next, they would input the HectoPascal or Inches
of Mercury measurement into that window. But we’re still not done talking about
altimeters. A barometer can only do so much. At high altitudes, the changes in air pressure on the
ground become rather irrelevant, so at some point during the climb, pilots switch their altimeters
over to what is known as standard pressure. As its name suggests, it’s a global standard of
pressure that has been agreed upon to be the sea level average atmospheric pressure. In HectoPascal
this would be 1013, or 29.92 Inches of Mercury. Because the standard air pressure is rarely
the same as that at ground or sea level, sometimes it is but it is an average, this
means that when a plane is say cruising at 30,000 feet… That’s not exactly true.
At higher altitudes, pilots and controllers use what are called Flight Levels which are
abbreviated thousands of feet based on the standard sea level pressure we’ve already
discussed. So, when we say our hypothetical plane is flying at 30,000 feet, to those in the
know this may be referred to as Flight Level 300. Which technically is only roughly 30,000 feet.
That is if you were to actually measure it. because every plane at cruising altitude should
be tuned into that standard pressure, this doesn’t cause any problems in terms of traffic conflict.
So, with all of that information, how did things go wrong on the Austrian Airlines
Viscount, on that one day in 1960. Basically, and incongruence between the Captain and
First Officer’s altimeters had emerged. When investigators later combed through the
wreckage the discovered that the two instruments were badly damaged in the accident. Infact
they were completely destroyed in the crash, including much of the internal mechanisms of
the instruments themselves. Because of this, evidence was non-existent to suggest there was
ever a mechanical problem with the altimeters. Despite the poor state of the altimeters, Austrian
investigators were able to determine that both altimeters were actually sort of set correctly
however, there was still a large discrepancy between the two. A difference of 23 HectoPascal
or millibars was observed. This corresponded to a nearly 700-foot difference between the two
instruments. The captain side altimeter was set to 0990 mb whilst the Co-pilot altimeter was set
to 1013. Investigators believe that the possible explanation for this and possible causal factor
in the crash, was that the captain had set his altimeter to the QFE air pressure setting, so
in theory it would indicate the actual altitude above the ground, whilst the co-pilots was set
on the QNH to read the altitude above sea level. To round it off, the elevation of Sheremetyevo
airport is nearly 700 feet above sea level. The plane flew too low and the pilots flying was
unaware. The poor weather that night obscured much of the pilot’s view outside. It is believed
that they thought they were flying on the correct approach path, supposedly backed up with radio
transmissions between the plane and control tower. But the thing is, with the lack of a cockpit
voice recorder because this was 1960, investigators had no way to know if the pilot’s
had actually misinterpreted their approach. Assuming that Captain Erwin Wilfing was
the one flying the plane, his altimeter was displaying an altitude 700 feet lower
than the co-pilots instrument. You could imagine how with such a discrepancy, that
conflict could occur between the plane and the ground. From what one can gather; this
was exactly what happened. When factoring in the tops of the nearby trees, the plane
was getting dangerously close to the ground. The viscount plane descended well below the
intended flight path and initially struck the tops of some trees west of the airport. An attempt
was supposedly made to pull the plane up, however significant damage had already been inflicted
on the plane as the pilots were unable to climb. Seconds later the plane crashed into the ground.
The area the plane had crashed into was in a wooded region a few kilometres west of the runway
at Sheremetyevo, near the town of Zelenograd. Of the 37 people on board, 31
were now dead leaving 6 survivors. There were investigations that were conducted
both by Austrian and Soviet investigators. A certain conspiracy sort of surfaced around this
flight. Apparently, according to the writings of an Austrian Journalist, an individual with
connections to the KGB was booked onto the flight but was sternly warned not to board
the plane and to walk away from the airport in Vienna. The story goes, the plane was
carrying documents bound for the US embassy in Moscow and was downed on the approach. Make
of that what you will as I don’t wish to step into that sort of region with this video.
Austrian Airlines with this information had determined that the pilots had deviated from
standard practices. The pilots should have had their altimeters synchronized to read the same,
it’s right there in the checklists. The reasons as to why they might have done this are unknown.
Patreon Outro A big thanks once again to Blinkist for sponsoring
this video. If you fancy checking out Blinkist, be sure to use my link below and get learning today.
It’s been a long while since we’ve had a sponsor, I think last time I did one was back
in November 2021 so a while ago now. Anyway, I would like to say that this is the
first of two videos coming out this week. Be sure to be subscribed so you don’t miss the
next video coming at the usual time on Saturday. I would like to take a moment to thank my
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Anyway, that is all from me today but like I said, there is another video coming on Saturday. So
I’ll see you then, have a great evening goodbye.
