Western Planes Also Disappear from Air Traffic Control Radar
Russian airliners are not the only aircraft to have suddenly disappeared from
the radar screen of Helsinki-Vantaa airport. On Tuesday we reported on a
situation in December, in which a Russian Aeroflot plane, which had disappeared
from the radar of Helsinki-Vantaa air traffic control, and came within 150
metres of a Finnair plane. It was suggested that the problem is most frequent
with Russian airliners built in the Soviet era.
Now the Civil Aviation Administration /CAA/ reports that such disappearances
lasting from a few seconds to a minute occur occasionally with Western planes as
According to Jaakko Kaskia, deputy director of flight safety at the CAA, the
main reason for short disappearances is that the radar transponder of the
aircraft has either been accidentally been left shut off, or is not working
properly. Also, the antenna of the transponder can sometimes be blocked by the
aircraft`s fuselage when the plane banks for a turn.
Kaskia says that such problems do not cause hazardous situations, and that there
are other ways to guide the planes to a safe landing.
However, no explanation has been found for three recent incidents involving
Russian planes, in which radar contact was lost for several minutes. The longest
break, lasting five minutes on December 15 involved an Aeroflot plane which had
just left Helsinki-Vantaa airport for Moscow, and which came within 150 metres
of a Finnair plane returning from Spain.
After studying the incident of December 15, the Accident Investigation Board
/OTK/ believes that either the transponder on the Russian plane was turned off,
or that there was a fault of some kind in the signal it sent, or in the
secondary radar receiving the signal. Supporting the idea that the air traffic
control radar was malfunctioning was the fact that the Russian plane which was
invisible to the radar Helsinki-Vantaa did show up on the radars of the regional
air traffic controls of Tampere and Rovaniemi.
On Wednesday the CAA and OTK agreed to start testing and monitoring the signal
level of all types of aircraft. The intensified monitoring is to begin next
The Accident Investigation Board has also asked for help from the Russians. On
the same day that the Aeroflot plane flew too close to the Finnair plane,
another Soviet era aircraft, a Tupolev-134 of Pulkovo AirLines also disappeared
from the radar. The same happened more recently, on January 5, with an Aeroflot
According to Heikki Jaakkola of the CAA, the disappearances of aircraft from
radar are not leading to any extraordinary measures at Helsinki-Vantaa airport.
He says that planes can be brought in and dispatched safely even without the
help of radar.
``There is always the flight plan which contains the basic information. If a
plane disappears from the radar, the distance between other planes is extended.
At smaller airports where there is no radar, this is what is always done``,
Meanwhile, the Russian airline Aeroflot has promised to look into the situation.
The head of Aeroflot`s Helsinki office, Vladimir Patimov says that on Wednesday
he was in touch with the head office in Moscow as well as aviation officials in
both Finland and Russia. The company has promised to provide Finnish officials
with a report on the December incident within a few days.