GPS/RNAV Flashcards
Cover RNAV/GPS/RNP
What’s the difference between LPV & LNAV/VNAV?
LPV
- Both have DA, but LPV DA’s lower than L/VNAV
- LPV requires WAAS to shoot this approach
- Cannot use precision minima if it’s to be used for alternate planning
- Increased sensitivity all the way down to the runway
L/VNAV
- Requires barometric aiding (an integrity augmentation allowing GPS to use non-satellite input to use for vertical reference) if not WAAS equipped
- Higher DA
- Deflection sensitivity does NOT change as you get closer to the runway
-
What is LNAV +V?
- LNAV+V gives you an advisory glidepath (as opposed to approved) for IAP
- Glidepath may guide you below step down minimums so watch your altitudes
- Refer to LNAV minima for the approach
- Requires WAAS GPS to get the “LNAV+V” advisory on GPS
- For airports that cannot have LNAV & L/VNAV due to obstacle and terrain clearance
If I see LNAV+V on my GPS during the approach, can I descend to a published DA since I have vertical guidance?
- NO
- LNAV+V is an advisory glideslope not approved
- I may follow the glideslope but be careful not to go below published minimum altitudes for each fix as obstacle clearance is not guaranteed
If you don’t have WAAS, but you have baro-aiding altimeter able to assist with L/VNAV descent, what are some of the limitations regarding baro-aiding altimeter?
- I may not be able to use minima published for baro-aiding altimeter due to extreme temps (hot or cold) as this could drastically affect the indicated altitudes
- Must not descend to DA; make sure to read the notes that may negate the descent to a DA
For testing or IPC purposes, when can I use an LPV approach for precision/non-precision approach?
- It can be used for a non-precision approach if the DA is greater than 300’ HAT (height above touchdown)
- When using for a precision approach, the DA must be 300’ HAT or lower
What are the differences between an ILS and GPS LPV?
_GPS_
- Sensitivity doesn’t get any tighter (usually 700’ width of the runway) the closer you get to the runway
- Doesn’t require infrastructure at the airport to provide information for the approach
_ILS_
- Needle gets more sensitive the closer you get to the runway
- Requires infrastructure at the airport to provide approach information
What is RAIM?
- RAIM is the capability of a GPS receiver to perform integrity monitoring on itself by ensuring available satellite signals meet the integrity requirements for a given phase of flight.
- Without RAIM, the pilot has no assurance of the GPS position integrity. RAIM provides immediate feedback to the pilot.
How many satellites are used for 3D info on a GPS, and how many do you need for your GPS to utilize the RAIM function?
- 4 satellites required for 3D nav
- 5 satellites or 4 w/ baro aiding altimeter is required for GPS to use RAIM to monitor itself
What’s the difference between RAIM and FDE?
- RAIM is the faulty detection function of a GPS to detect a bad satellite
- FDE (fault detection exclusion) is the ability to isolate and remove the bad satellite from being used for navigation
- RAIM only requires 5 satellites or 4 with baro aiding capabilities
- FDE requires 6 satellites or 5 with baro aiding
What are the 2 general fault messages you will receive from a RAIM?
- There are not enough satellites to provide RAIM integrity monitoring
- The GPS nav solution should be acceptable, but integrity solution cannot be determined
- The second type indicates that the RAIM integrity monitor has detected a potential error and that there is an inconsistency in the navigation solution for the given phase of flight.
- Without RAIM capability, the pilot has no assurance of the accuracy of the GPS position.
Explain how WAAS works:
- GPS Satellites: Signals are received from GPS satellites and information is sent to across the country to _38_ ground reference stations
- Ground Reference Stations: Errors are detected at the ground reference station and data is sent to master station
- Master Station: Generated error corrections are sent to Ground Uplink Stations (GUS)
- GUS: Uplink stations uplink corrected info to Geo-Stationary Satellites (rotates w/ the earth)
- Geo Satellites: Send corrected data via GPS signal to a/c receiver and corrected place is displayed on GPS
What is RNP?
Required Navigation Performance
- RNP is RNAV w/ onboard nav monitoring and alerting
- Allows less reliance on ATC and/or route separation for overall safety of the operation
What are fly by & fly over waypoints?
- Fly by waypoints require anticipated turns so you don’t miss the next flight course following the FBWP
- Fly over waypoint turns are made after flying over the FOWP
