- 1 Introduction
- 2 Instruments
- 2.1 GNSS Receiver
- 2.2 Control Display Unit & Navigation Display
- 2.3 Conventional Turns
- 3 RNAV flight: do-lists, checklists and briefings
- 4 Conclusion
- 5 See also
- 6 Reference
- 7 Author
The position of the aircraft is known using various sensors that can compute its position. RNAV can then be summed up as the ability of one aircraft to navigate, computing change of tracks from one point to another, using only coordinates.
The RNAV system may also be connected with other systems, such as auto-throttle and autopilot/flight director, allowing more automated flight operation and performance management. Despite the differences in architecture and equipment, the basic types of functions contained in the RNAV equipment are common.
Fly-by turns are a key characteristic of an RNAV flight path. The RNAV system uses information on aircraft speed, bank angle, wind, and track angle change, to calculate a flight path turn that smoothly transitions from one path segment to the next.
We will study some basic functions and requirements of a GNSS receiver using the Garmin GNS430 depicted in Flight Simulator as the default GPS.
You may also use the official Garmin trainer version available on their website.
Connection between GNSS receiver and Navigation instrument (HSI/CDI)
Else, the pilot should synchronize it when passing a waypoint for a correct situational awareness.
From left to right, and up to bottom:
- TERM: Current mode in which the GPS is operating
- 1.0: Current RNAV performance associated to current mode
- Lateral deviation in regard to desired track (DTK)
From left to right, and up to bottom:
- Approach mode (LPV, LNAV, L/VNAV, …)
- 0.4: Performance reducing linearly during approach phase from 1NM to 0.3/0.1NM
- FA: Final Approach Fix (specific procedure point: FAF, IAF, MAPt …)
- Vertical guidance and deviation
Following specifications are required for each mode:
- Enroute (RNAV-5)
- RAIM Alert Limit (IMAL) : 2.0NM
- CDI Sensitivity : 5.0NM
- Terminal (RNAV-1)
- RAIM Alert Limit (IMAL) : 1.0NM
- CDI Sensitivity : 1.0NM
- Approach (RNP APCH)
- RAIM Alert Limit (IMAL) : 0.3NM
- CDI Sensitivity : up to 0.1NM for LPV, 0.3NM for overlay and LNAV(+V).
Control Display Unit & Navigation Display
CDU will provide all the information computed by the Flight Management Systems (FMS), relying on input provided by Attitude & Horizontal Reference Systems (AHRS), navigation sensors, and the pilot. The display will be mainly integrated into a Navigation Display.
On a Boeing 737NG, the aircraft obtains its position generally by using all available sensors (except for LORAN). When powering up the aircraft, the pilot must insert/confirm position to initialize IRS. This input is made in the FMC but the mechanical device present on oldies is still completely integrated.
Various pages of the FMC display position computation according to each sensor
Conduct of RNAV operations
Comparatively to the Garmin, the FMC can display Required Navigation Performance
Flight Information Display
PFD and ND will display the same information to the pilot, including graphical representations.
- Track to intercept a fix radial
- Timed base turns
- Procedure 45/180 and 80/260 turns
RNAV flight: do-lists, checklists and briefings
This part of the documentation is intended to provide the key actions that should be associated to flying RNAV, in particular emphasizing the difference with an aircraft flying purely conventional.
- Route: VADEN T227 DEDIN
- SID: VADEN 1P
- STAR: DEDIN 1D
- APP: RNAV (GNSS) RWY09
This can be done in Europe by using the AUGUR RAIM Prediction Tool: http://augur2.ecacnav.com/
The only case in which this check is not needed is if your aircraft is SBAS-equipped.
You will need to check the availability of the GNSS signal for:
- your route using “Route Tool”
- your terminal area using “Terminal/Approach Tool”
Same with « Terminal/Approach Tool »
- Perform same tasks as for departure/arrivals. Clearly identify discontinuities, particularly for Overlay
- Verify altitude constraint.
- Perform RAIM Prediction if not done on ground.
- Conventional means (VOR/ADF)…..SET
- RAIM…..Operative and available
Add into your briefing a strategy about loss of GNSS and positioning. Highlight discontinuities.
RNAV is a brilliant navigation method to optimize traffic flow using the power of GNSS even though it implies tons of new rules, standards and recommendations to implement for all actors of the aviation industry.
However the future is already marching on, as the evolution of RNAV is already being developed and enhanced: the Required Navigation Performance (RNP)
- VID 200696 - Creation
- VID 256292 - Wiki Integration
DATE OF SUBMISSION
- 01:03, 14 May 2021
- This documentation is copyrighted as part of the intellectual property of the International Virtual Aviation Organisation.
- The content of this documentation is intended for aviation simulation only and must not be used for real aviation operations.