Aircraft Radio & Navigation Systems / Flight Planning

It is vital to have a flight plan before flying an aircraft from point A to point B. Let says I have recently purchased a Cessna S172SP single prop aircraft. For my first flight, I am to depart from Shoreham airport (SHR), it will then intercept Seaford (SFD) towards Haywards Heath (using way-points) and then back towards Shoreham. Numerous navigational techniques are required, some which are listed below:

• Shoreham (SRH) to Seaford (SFD) – using Pilotage
• Seaford (SFD) to Haywards Health (Waypoint) – using VOR
• Haywards Heath (Waypoint) to Shoreham (SRH) – using ADF/NDB

Limitations and restrictions need to be acknowledged by the pilot before planning the flight. These factors are a guideline set by the Civil Aviation Authority, thus have to be abided at all times. A precise flight plan will allow the pilot to navigate around the airspace without intrusion.

Flight Planning:

Using a verified aeronautical chart, a flight plan must be developed. This plan must be followed when departing from Shoreham airport from runway 20 (most efficient runway to take-off from due to flight plan). It must be noted that there is an altitude restriction from Seaford to Haywards Heath thus the aircraft is to fly at a cruising altitude of 4500 feet.

As pilotage is used from Shoreham to Seaford, a VRP (visual reference point) must be taken in to account. The VRP on this sector is Brighton Marina. Having found the reference point, I can then determine the angle required to intercept the flight path towards Seaford. Since having, for instance, a wind from South West at 220°|16KTS, I must consider the drift factor. The calculation determines the drift factor for the aircraft to fly at a constant heading of 110° after a 700ft. climb, and a left bank turn cruising towards Seaford.

A VOR needs to be acknowledged between the way-points Seaford to Haywards Heath. This entails for a second way-point, thus a ‘Phantom’ way-point is used. In other words a secondary way-point from another area, away from my flight path is used as a reference guideline to help navigate accurately. This Phantom frequency will allow the interception for both VRPs, the first VRP is at Lewes and the second at Haywards Heath. A drift angle needs to be taken into consideration as wind is acting from the South West (220°) at 16KTS. This is an important factor to take into account as this would eliminate the drift of the aircraft, hence a heading of 331° is what the aircraft needs to fly at. To determine the aircraft position at all times, a frequency is to be tuned into the navigation 2 panel.

An aeronautical chart is a very important map to that a pilot must carry at all times. This present’s important information such as the positioning of the NDB, in this case at SRH airport. To precisely locate and position the runway (landing at SHR), a radio beacon frequency is set in the initial stages of the flight on the AF panel. A magnetic needle then displays the location of SHR airport. The flight-plan to be used should consist of detailed information such as way-points, VOR, frequencies and VRP and NDB station has been shown.

Pilotage:

Pilotage is the use of fixed visual references on the ground and sea by the means of sight or radar to guide in our case the pilot to a specific destination. This technique is applied when the aircraft thus the pilot is close enough to land (the pilot can use a map or an aeronautical chart to help guide him more accurately/safely). At this stage, the pilot does not have enough time to make a detailed navigational plan but in this circumstance, it is not necessary for the pilot at this stage to exactly know where he is but instead pilotage guarantees him that he is in a safe position/area or on a safe path which will remain for a period of time until the next change is needed to be made helping him stay away from dangerous hazards (tall buildings, power-lines, mountains etc.).

Disadvantages to this would be that the pilot needs to recognise the visual references in order to make use of them. Poor visibility and heavy winds (pushing the aircraft of course) may also affect safe pilotage. Drifting off-course can occur (if not using the navigating instruments). Regular updated maps will also be needed as there would be new/demolished buildings/landmarks.

ADF (Automatic Directional Finder):

An Automatic Direction Finder or known as ADF is widely used today in navigating. This equipment within the aircraft is used to tune into a specific frequency to the NDBs (Non directional beacons) installed on the ground. An ADF works in the low to medium frequency band of 190kHz to 1750kHz. The radio signal follows the curvature of the Earth; the maximum distance would depend on the power of the beacon. An ADF can receive on both AM radio station and NDB (Non-Directional Beacon). Non-Directional Beacon operate in the frequency band of 190 to 535KHz. When selected a specific frequency, an ADF allows the pilot to: determine the positioning of the airport and how far it is from the aircraft by using the transmitted NDB signals.

NDB (Non Directional Beacon):

A Non-Directional Beacon or known as NDB is a ground based, low frequency MF radio transmitter which is used as an instrument approach to airports for aircraft's. This radiates an uninterrupted carrier in the range 255kHz to 526.5kHz.

A NDB transmits an omni-directional signal which is received by Automatic Directional Finder ‘ADF’ which as mentioned above can be found in most modern aircraft's. The pilot would use the ADF instrument to determine the direction to the NDB relative to the aircraft. The pilot is able to navigate using ADF by entering the frequency of the NDB and the compass card on the ADF which will then indicate the heading to the station. This signal is transmitted and is uninterrupted 24/7. An audible Morse code call sign which will consist of one or more letters or numbers will be used to help identify the NDB which is being received.

A NDB can also be used as Locator Outer Markers or known as LOM for a pilot to use an Instrument Landing System or known as (ILS). These Outer Markers are placed at the starting area of an ILS approach or flight path for the aircraft to follow for a standard arrival. NDBs are extremely reliable as they have been in working application for decades. They are also extremely low cost to install and operate.

VOR (VHF Omni-Directional Range):

A VOR (short for VHF Omni-Directional Range) is a radio station that transmits radio navigation signals in the very high frequency or VHF band. This station transmits radio signals called ‘radials’ in every direction, away from the station (navigation information is referenced to magnetic north). Pilots use 360 radials, 1 for each degree in a circle, to determine position. For example, if the instruments within the aircraft indicate the aircraft to be on its 360 radial, then the aircraft is north of the VOR, if on the 90 radial then the aircraft is east of the VOR, if on the 180 radial then the aircraft is south of the VOR and if on the 270 radial the aircraft is west of the VOR.

Each VOR has its own frequency, Morse code identifier (sometimes a voice identifier) and data that is broadcasted in a very high frequency radio composite signal, allowing the aircrafts receiving equipment acknowledge the magnetic bearing from the ground station to the aircraft. Pilots are then able to use this information to determine their exact position and navigate to their desired destination, making adjustments if needed.

To find our heading, we can use a VFR or IFR chart and then set the course into an OBS (Omni Bearing Selector) and flying to that heading. When established on the heading, the CDI (Course Deviation Indicator) will indicate if the course is to the right or left. The course has to be intercepted and tracked, as the CDI moves closer to the centre, the heading needs to be changed to match the course, it is vital that the needle is centred. Wind will blow you off course thus we must intercept the course and use a WCA (Wind Correction Angle).