Electronic Flight Planning and Navigation

Revision: March 14, 2012, at 03:28 AM

Module content

GPS technology combined with an accurate aeronautical database provides excellent position fixing capability — and excellent DR capability when associated with a stored flight plan. GPS is not yet classified as a sole-means navigation system under the VFR and is only officially regarded as a primary-means day VFR navigation if the GPS system accords with the FAA's Technical Standard Order [TSO] C129 or TSO C145/6 series or has other approval. However the reality is that many recreational pilots do use non-TSO'd GPS, plus electronic on-screen position tracking (i.e. a moving map display), as the primary means of airborne navigation.

When a small portable computer is used for a true topographical moving map display then additional material can be added to create 'personal' charts; plus weather, Notams and so on can be stored. Thus the concept of the 'electronic flight bag' is introduced – hopefully with paper charts and manual pilotage as the backup system.

So electronic flight planning and electronic navigation is becoming the norm for many recreational pilots, not least because the availability of powerful, inexpensive – but highly reliable – desktop computers, handheld PDAs and handheld GPSs (or GPS cards) is now associated with a proliferation of quality utility software – readily and cheaply available to all via the internet – allowing any reasonably computer adept person to put together a system of software, general purpose (rather than application oriented) hardware and navigation databases tailored to their particular aviation needs; all without excessive cost.

Good electronic VFR flight planning should only differ from the manual flight planning described in prior modules, in that digitised – rather than paper –topographical charts are used to plan, and finally plot, the route; and the final flight plan is stored in digital rather than paper and pencil format.

When airborne there is only a slight difference in pilotage where the navigator – while still reading from map to ground – is primarily relying on a cursor on a digitised moving topographical chart to display a constantly updated current position and then confirming it with the ground. The significant difference in airborne navigation is in using electronic DR to provide all the inflight data and corrections necessary to arrive at the planned destination safely: which indicates the vital importance of working with a complete and absolutely accurate aeronautical database.

In addition (as a flow-on from the glass primary flight displays and multi function displays of larger contemporary IFR aircraft) the availability of rather inexpensive non-certified electronic flight instrument systems [EFIS] is increasing. Such non-certified systems can be legally installed microlight aircraft – although there may be a regulatory problem if a non-certified EFIS is providing altitude encoding to a transponder. These flight instrument systems are software based and, in future, are likely to provide increasing data transfer to/from other avionics within electronic communications, navigation and surveillance technology.

It is possible that ADS-B will be operational in the lower levels of Australian airspace within a few years. It is then likely that a handheld PDA, linked to the ADS-B device, could be used for a low cost cockpit display of traffic information overlaying a moving topographic map.

Electronic planning and navigation should follow the same procedures described in the preceding modules:

  • Accessing airfield and airspace information
  • Plotting a route on an aeronautical or topographical chart
  • Accessing TAFs, ARFORs and Notams
  • Doing the E6b calculations and producing a flight plan
  • Monitoring flight by checking from map to ground and
  • Making the necessary enroute flight path adjustments.

Navigation information databases

In manual flight planning navigation information is obtained from printed documents – VNCs and other reference charts – containing details concerning aerodromes, navigation aids, air route intersections, special use airspace, airspace boundaries, magnetic variation and communications frequencies: obviously location latitude, longitude and elevation are particularly important details. The digital version of such print information is the aeronautical navigation database. Such databases are supplied via various media, including plug-in data cards and internet download, and it is most important that the compiler/distributor of the database material has a quality assurance system that guarantees the accuracy of the data. Jeppesen is regarded as the best source – certainly the best known – but most flight planning software includes a proprietary database and, hopefully, some guarantee of its quality level. In some databases the aerodrome runway data also includes a graphic display.

In addition to the database a full function GPS receiver will utilise a built-in ground map or 'base map' and the data that can be displayed graphically, such as locations and airspace boundaries, is extracted from the database and represented by icons on the basic map page. The base map in a GPS receiver usually cannot be updated or changed over although some receivers employ a programmable plug-in cartridge and other maps can then be loaded.

The problem for recreational pilots is that the standard aviation databases – the Jeppesen for example – are amended monthly, thus an initial database will become increasingly out of date. However the bulk of the database changes relate to refinements that are probably only applicable to IFR operations. The updates come in CD form for use in PCs connected to the GPS receiver via a special data cable, or in a replaceable data cartridge format. Update subscription services are comparatively costly for the non-professional so the fine judgement for recreational pilots is when, or how often, to update the database. However as non-TSO'd GPS is officially only a supplemental-means navigation tool and, if VFR pilots in Australia always check – pre-flight – the airfield information contained in NZAIP on-line, then the only significant area for doubt is in changes to controlled airspace or special use airspace boundaries. The use of current VNC and VTC charts [paper or digitised] and reference to Notams during flight planning will preclude any problems in that area.

The data for airfields that are not contained in a standard aviation database can be entered in a user's database if required, but the need for absolute assurance that location coordinates and elevations have been correctly ascertained and entered, cannot be over-emphasised.

Digitised aeronautical charts

Route construction in electronic flight planning follows the steps outlined in previous sections using trip planning software on a desktop computer. Much of this specialised software now utilises digitised aeronautical and topographical charts.

The raster format is for use in desktop computers with flight planning software and for inflight use in laptops or PDAs with moving map software. GPS moving maps use vector digitisation and are usually only available from GPS manufacturers or their distributors.

A vector image is a series of mathematically defined points, lines and polygons (closed shapes) whereas a raster image (such as that from a digital camera or a scanner) is a matrix of rows and columns each cell containing a picture element [pixel] with a discrete colour value – a bit-mapped image – a BMP, TIFF, JPEG, GIF or PNG file. Vector based images allow 'zoom-in' without distortion, whereas rasters do not; unless a larger file has been created containing several 'zoom' levels. When a paper map is scanned to produce a raster image a few latitude/longitude control points have to be identified and stored in a calibration text file together with other essential information such as the map projection and datum; this may require some utility software which is generally included in flight planning software packages or possibly just a normal text editing utility. There is software available to convert raster to vector, and vice versa.

As every pixel in a bit-mapped image can be edited (the colour value changed with image manipulation software) then permanent user data and symbols – for example, the verified position and name of a private airstrip or a named waypoint – can easily be added to the original image (with careful matching of font, size and colour) to create a personalised chart [WAC or VNC for example].

Flight planning software

A range of desktop computer flight planning software is available to facilitate route selection. Waypoints are selected (either from a table or by point-and-click methods) and the planned route(s) plotted on a chart display.

Some software requires basic performance, fuel consumption and other data for the user's aircraft to be pre-stored then, after entering forecast wind velocity for various altitudes, E6B software calculates much the same information as acquired/calculated manually in section 5.4, thus allowing the user to select an optimum route and cruise altitude.

The route, resultant flight plan and other data can then be printed or uploaded into a GPS, laptop, smartphone or EFIS. Most flight planning software supports import/export of waypoint files.