Navigational Aids

Navigational Aids

TCW Navigation, ATC and Communications Site, Stanley Airhead 1982

In order to activate an airfield for use by aircraft, an Aircraft requires several key elements, theses being a runway, airfield lighting, navigational aids, and communications. Since the concept of Expeditionary Airpower the air force has utilised dedicated teams and equipment to provide this service. Presently 90SU is tasked to provide navigational and airfield facilities. 

Airfield Lighting Equipment

Airfield Lighting, Air Operations Iraq
Mobile O S , MOSKIT, Kabul, Afghanistan
Precision Approach Path Indicator (PAPI)
Deployable PAPI and Airfield Lighting Systems

In the early days of the expeditionary Air Force the Royal Fling Corp utilised cleared areas of land with small fires or lamps to indicate the strip. During the years that followed the strips remained relatively the same, however, the methods of lighting them ranged from torches to Portable Airfield Ground Lighting. These lighting systems ranged from semi-permanent systems such as the Tactical Flare Path, TFP, complete with approach lights and Precision Approach Path Indicator, PAPIS, that could be deployed from the back of a vehicle connecting each light with a series of cables. In later years the Minimum Operational Strip, MOS Kit was introduced. This system allowed the portable lights to be charged whilst not in use by a dedicated generator. The MOS kit also had the advantage that it could be remotely controlled switching between normal operation and Infrared. Additionally, the in order for the SF and Airborne forces to be able to activate a covert strip the Portable Airfield Lights PAL, were developed.

 

 

Precision Approach Path Indicator, PAPIS.

The PAPI is a light system positioned beside the runway that consists of two, three or four lights that provide a visual indication of a fixed-wing aircraft’s position on the glidepath for the associated runway. The PAPI is usually located on the left side of the runway and can be seen up to five miles during the day and twenty miles at night. Each box of lights is equipped with an optical apparatus that splits light output into two segments, red and white. Depending on the angle of approach, the lights will appear either red or white to the pilot. Ideally the total of lights will change from white to half red, moving in succession from right to left side. The pilot will have reached the normal glidepath (usually 3 degrees) when there is an even split in red and white lights. If an aircraft is beneath the glidepath, red lights will outnumber white; if an aircraft is above the glidepath, more white lights are visible.

Digital Readout Direction Finder (DRDF)

Digital Readout Direction Finder (DRDS) and UHF Antenna, Stanley Airfield
DRDF Basrah, Jun 05

The DRDF works in both VHF and UHF band. Has a number of concentric aerials which activate in turn through 360 degrees. Once in range, the pilot contacts Air Traffic Control via air to ground U/VHF communications. This allows the DRDF aerial in the specified vector to receive the incoming signal, generating a phase difference from a reference point usually north. This creates a pulse for every half a degree calculated. By this process a bearing in degrees is generated allowing an Air Traffic Controller to ability to see what vector the aircraft is flying from the airfield. The DRDF also has the capability to inverse this reading by 180 degrees allowing the controller to know the exact coordinates/bearing the pilot needs to fly to reach the airfield. Within the ATC a digital vector or numerical display indicates a reading in degrees and also a frequency selection unit allowing them to monitor only selected frequencies. When a reading is obtained from a transmitting aircraft, a reading in degrees is displayed and also a trace is pulled on the radar display which will dissect the target. This will help the controller to determine which aircraft is trying to contact them. 

Tactical Aircraft Navigation Aid (TacAN)

TACAN, Stanley Airfield, 1982
TACAN Transmit System

TACAN is a system which, working in the Y.H.F. band, between 962 and 1,214 Mc/s, gives to a pilot continuous information as to his range and bearing from a beacon. The airborne equipment consists of an interrogating transmitter and a receiver which includes suitable demodulating circuits to enable the information contained in the beacon’s response to be extracted. The ground equipment consists of a beacon provided with a rotating aerial system. In the absence of interrogating signals the beacon transmits a series of random pulses together with groups of marker or reference pulses which are locked to the aerial rotation. Bearing information can be obtained without interrogation since the beacon is continuously transmitting.

Precision Approach radar, Watchman radar. AR1

Watchman AR1 - Shackleton Flight Check, Shetland

Ground Controlled Approach radar or PAR is used to control the approach of aircraft to an airfield, usually known as a G.C.A.  The requirement here is twofold.  First, all aircraft flying within a range of thirty or forty miles must be detected; secondly, they must be accurately ‘talked down’ on to the correct runway.  The detection of the aircraft is made easier by the fact that they will be flying in well-defined height zones.  The radar will not have to deal with very low flying targets and will not need to take an interest in very high targets.  Consequently the detection beam is usually set with its maximum at an angle of about 3o to reduce the likelihood of ground clutter.  Nonetheless, M.T.I  techniques are widely used for G.C.A. radars in order that the controllers shall have the clearest possible picture of aerial activity in the vicinity of the airfield.  The shape of the beam is ‘cosecant squared’, designed to give good coverage up to a height of about 5000 feet.

Ground to Air Communications

Radio Cabin and Masts, Falklands
26100 Radio Cabin

In order to assist aircraft onto a airfield, the ground controller utilises dedicated voice communications. These systems vary from small, man portable backpacks to the larger Air transportable communications cabins. Also available are transceivers that can be installed inside existing tents or buildings depending on the requirement or environment.  Depending on the range and type of airfield, the radios have an output power ranging from 5W to

Mobile Air Traffic Control.

Mobile ATC Cabin

In conjunction with Tactical Air Traffic Control, 90SU can provide mobile Air Traffic Control Facilities. This ranges from small platforms that can be transported into theatre on a Hercules to the larger, more permanent centres. The larger centres are normally air conditioned and can be elevated giving improved visibility. Once erected the cabins are then remotely connected to the navigational aids, radar, communications and weather sensing equipment, thus providing a fully integrated Air traffic control centre.   

Mobile ATC, communications cabins and MT350, Pristina Airfield

Project Marshall

Mobile ATC Cabin, with integrated communications and Radar feeds

Project Marshall enables vital air traffic management services at MOD-operated airfields in the UK and overseas, including Cyprus, Gibraltar and the Falkland Islands.

 

Not only will Project Marshall look to deliver fixed  Air Traffic Control equipment, including radar displays, ground-to-air radios, voice communication and control systems and record and replay equipment. It will also deliver deployable navigation aids, landing aids, and air traffic management systems.

Navigational Aids

Ground Support Equipment