Category Archives: Flight Following

Communications Tower

Each of us in the Communication team works 2 shifts a day in the tower. Today for example I worked the morning shift with Pete and the afternoon shift with Crispin then Callum and Crispin took over for the evening shift and Pete had “second night gash” in the evening.

A typical shift in the tower will involve flight following and base radio communications.

Communication Tower
Communication Tower

The computer on the left is used for AFTN flight planning. This is where we submit the AFTN flight plan intentions and update departure and arrival times for each flight. Next week we will be changing to the AFPEX web-based flight planning application instead of the UDP based installed Copperchase AFTN client software. This will make the client PC easier to administer and eliminate the  need for a dedicated established network link through to Swanick NATS centre.


Also on the left side of the desk are our antenna choosers and rotator.
We have 4 HF antennas. A North-South, an East-West, a Rotatable log periodic and an emergency HF. The emergency antenna is connected directly to our batter powered iCOM ic- 78 which we only use during power downs. The other 3 antenna we can switch between our 3 HF transmitters.

The main console of the desk has our 2 skanti HF sets and the marine and aero VHF units.


The right hand side PC we use to pickup weather observations from the internet and

On the right corner of the desk we have our Iridium and Cisco VOIP phones.

Rothera Airfield Landing Procedure

When pilots use an airfield they follow published airfield procedures .  I have been learning how Rothera airfield is used and what procedures arriving and departing aircraft need to follow.

The most basic piece of information a pilot needs about an airfield they intend to use is the magnetic heading of the runway.  They can’t land sideways onto a runway so obviously they need to know what their compass needs to be pointing as they approach the runway.  Because this information is so fundamental it is actually encoded into the number assigned to the runway.

Runway 23-05 Sign @ Cambridge Airport
Runway 23-05 Sign @ Cambridge Airport

For example Cambridge airport runs kinda east-west.  Approaching Cambridge Airport from the east you need to be heading 230 degrees on your compass to hit the runway directly and approaching from the west you would need to head 050 degrees (180 degrees from 230).  Cambridge runway has therefore been assigned runway numbers  05 and 23. The runway number tells the pilot the heading to approach the runway with.

Rothera runway numbers are very easy to remember as the magnetic heading of the runway is straight north-south.  The runway numbers assigned are therefore 36 (from the south) and 18 (from the north).  The number 36 would be painted in big white numerals at the southern threshold of the runway and 18 at the northern end of the runway.

The  Co-ordinates for the thresholds of the two runways are:

Runway 18  67 33.83 South  068 07.40 West
Runway 36  67 34.27 South 068 07.85 West

Clever-pants readers might be wondering why the westerly co-ordinate differs for the two thresholds if the runway runs directly on a north south magnetic heading. The reason is

Rothera Variation 21 degrees East
Rothera Variation 21 degrees East

that the co-ordinates are given in True while the runway is given as a Magnetic bearing.  Because of the vicinity to the South Pole there is a significant difference between true and magnetic headings at this latitude. The variation is 21 degrees east.  Maps of Rothera runway will show it   pointing at one o’clock.  But if you stood on the southern  end of the runway a compass  would  point at twelve o’clock.

Airfield crcuit
Runway 18 Lefthand

The circuit direction is also important airfield information .  The circuit direction is described as either left-hand or right-hand, according to which way the pilot turns in the circuit.  At Rothera there is a large mountain to the west of the runway so the circuit is always to the east of of the runway.  This means that Runway 36 has a right-hand  circuit and Runway 18 has left hand circuit.

There is unlikely to be a lot of circuit traffic at Rothera.  But the circuit direction and circuiting procedure will still be important to pilots because they may choose to do a  go-around then come back around circuit  or have a problem such as a bird strike during a take-off and want to come around the circuit and land.

Looking West.   The circuit is on the eastern side to avoid those mountains.

Looking West. Circuit is  on the east  to avoid those mountains.

The circuit height is 1,200 feet.  The elevation of the airfield is a tiny 13 feet.

The missed approach point (MAPt) is the point at which a pilot will decided whether they are going to continue into land or execute the missed approach procedure. The Rothera missed approach point RMAPt is 1.5 nm from the runway.  The minimum descent altitude(MDA) at the RMAPt is 700 feet.

The local barometric pressure is an important piece of airfield information.  Pilots use this information to calibrate their altimeters .  Without an accurate pressure a pilot won’t accurately know their altitude(bad).  Pressure is  typically provided to pilot as hector-pascals for a QNH (pressure msl) or a QFE(pressure at the runway threshold).  qnhandqfeBecause the runway at Rothera is only 13 feet above msl there is very little difference between the QFE pressure and the QNH pressure.  The QFE is one hector-pascal lower than the QNH.  So I just looked at the current pressure measurement for Rothera and I can see that it is reading 979 hPa.  From this I know that the QFE is 979 and the QNH is 980.

QFE 997 HPa  = QNH 998
Pressure = 979 hPa therefore QFE=  979hPa and  QNH =980hPa

The VHF frequency 129.7 MHz is for Traffic Information Broadcast by Aircraft (TIBA) in the region.  Pilots will listen to the is frequency and broadcast any pertinent information for other aircraft in the vicinity.

There are various ways aircraft can contact Rothera tower.  Rothera is a prior arrangement only airfield so any visiting aircraft will have phoned  to make arrangements prior to departing.  For long distance contact with Rothera tower from the air  pilots have three HF channels  9106.0 kHz,  7775.0kHz and 5080.0kHz.  Alternatively the aircraft have Iridium satellite phones and could call the tower on 881 631 831 227.  Once closer to the station probably less than 50 miles they should be able to make VHF radio contact on 118.1 MHz from which we would expect a clearer and more reliable connection.  We will be listening on all of those communication links in the tower, so I hope that don’t all go active simultaneously.

The official hours of operation of the airfield are 1100 to 0000 Zulu time, Monday to Saturday, October to February.  Zulu time is UTC and the time offset at Rothera is UTC-3 (P – Papa time). Converted to local time the operation hours will be 0800 to 2100 local time.  But in reality we will work much longer hours than this in the summer if the weather is favourable for flying.