Area Navigation (RNAV)Radio Navigation — DGCA CPL practice questions
Question 1 of 14
The accuracy required of a precision area navigation system is:
All 14 questions — Area Navigation (RNAV)
Radio Navigation · DGCA CPL. The correct option is marked on each.
Q1. The accuracy required of a precision area navigation system is:
- A.0.25 NM
- B.2 NM
- C.1 NM✓
- D.0.5 NM
Why: P-RNAV requires position accuracy of 1 NM on 95% of occasions. B-RNAV requires 5 NM.
Q2. A basic 2D RNAV system will determine tracking information from:
- A.twin DME
- B.VOR/DME✓
- C.twin VOR
- D.any of the above
Why: A basic 2D RNAV system uses VOR/DME (rho/theta — range and bearing) to define position and compute track to waypoints.
Q3. Aircraft on track WP1→WP2 (45 NM). Aircraft 20 NM from phantom station, phantom 270°/30 NM from VOR/DME. Aircraft 15 NM from VOR. Range read-out:
- A.15 NM
- B.20 NM✓
- C.25 NM
- D.30 NM
Why: The DME display shows distance to the phantom station (waypoint) , not the real VOR/DME. The aircraft is 20 NM from the phantom station → 20 NM .
Q4. The sequence of displays accessed on FMC initialization is:
- A.POS INIT, IDENT, RTE
- B.IDENT, RTE, POS INIT
- C.IDENT, POS INIT, RTE✓
- D.POS INIT, RTE, IDENT
Why: Correct pre-flight sequence: IDENT → POS INIT → RTE . IDENT first to verify database, then position initialization, then route entry.
Q5. The IRS position can be updated:
- A.on the ground only✓
- B.at designated positions en route and on the ground
- C.on the ground and overhead VOR/DME
- D.at selected waypoints and on the ground
Why: The IRS position can only be initialized on the ground . In flight, the FMC uses Kalman filtering with external references (DME/DME, GPS) to correct IRS drift, but the IRS itself is not manually updated in flight.
Q6. The position used by the FMC in the B737-400 is:
- A.an average of the two IRS positions
- B.an average of the two IRS positions smoothed by Kalman filtering
- C.taken from the selected IRS, smoothed by Kalman filtering and updated to external reference✓
- D.generated from external reference, updated by IRS as part of Kalman filtering
Why: The FMC uses the position from the selected IRS , processed by Kalman filtering and updated by external references (DME/DME, VOR/DME, GPS).
Q7. The FMC position will be at its most inaccurate:
- A.on take-off
- B.at TOC
- C.at TOD✓
- D.on final approach
Why: IRS drift accumulates over time. The position is most inaccurate at Top of Descent (TOD) — the end of a long cruise, furthest from the last IRS alignment. FMC tries to correct with DME/GPS updates.
Q8. Positions input to FMC using maximum 5 alphanumerics:
- A.SIDs & STARs, reporting points and airways
- B.Navigation facilities, reporting points and airways✓
- C.SIDs & STARs and latitude/longitude
- D.Latitude/longitude, reporting points and airways
Why: Max 5 alphanumerics: navigation facilities (NAVAIDS), reporting points, and airways designators . SIDs/STARs use up to 7. Lat/long uses special format N5000.0E00527.0.
Q9. The FMC navigation database can be accessed by pilots:
- A.to update the database
- B.to read information only✓
- C.to change between 28-day updates
- D.to change data for sector requirements
Why: Pilots can read (interrogate) the database only . The database cannot be modified by pilots; it is updated by maintenance/data service providers every 28 days.
Q10. Above 84° latitude, a twin FMS/triple IRS system goes to de-coupled operations because:
- A.to prevent error messages as IRS longitudes show large differences✓
- B.to ease pilot workload
- C.to improve system accuracy
- D.because magnetic variation changes rapidly
Why: Above 84° latitude, the secant of latitude increases rapidly. Longitude calculations from the two IRS systems show increasingly different values → de-coupled mode prevents false gross error messages.
Q11. Maximum range at which VOR bearing information is used by the B737-400 FMC:
- A.160 NM
- B.180 NM✓
- C.200 NM
- D.250 NM
Why: The B737-400 FMC uses VOR bearing up to 180 NM from the station. Beyond this range, bearing accuracy is insufficient for Kalman filtering updates.
Q12. Which of the following is NOT a waypoint definition format for the CDU:
- A.5-letter alphanumeric
- B.Lat/Long
- C.range and bearing from NAVAID
- D.bearing from two NAVAIDs✓
Why: The bearing/bearing (BB) format (e.g. GOW167.0/TRN090.5) IS a valid waypoint format. The format NOT available is bearing from two NAVAIDs as a simple format — the CDU uses only the BB format with specific syntax.
Q13. Correct format to input position 50°N 005°27'E to the CDU:
- A.5000.0N00527.0E
- B.N50E00527
- C.N5000.0E00527.0✓
- D.N5000E00527
Why: CDU latitude/longitude format: N5000.0E00527.0 — hemisphere prefix, degrees and decimal minutes, with decimal point mandatory.
Q14. The period of validity of the FMC navigation database is:
- A.28 days✓
- B.1 month
- C.determined by national authority (28 to 91 days)
- D.91 days
Why: The FMC navigation database is valid for 28 days (one AIRAC cycle). It must be updated every 28 days to remain current.