The document discusses flight inspection procedures for navigation aids. It describes the periodic ground and flight tests required by ICAO for radio navigation aids to ensure they are maintained within tolerance limits. The key types of inspections are commissioning, routine, special and site evaluation inspections. Flight inspection procedures are then outlined for localizers and glide paths, checking parameters like coverage, course width, clearance, structure and monitor alarms to ensure compliance with ICAO standards.

1. FLIGHT INSPECTION
CNS FACILITIES
Suresh Kumar Sharma,
JGM CNS

2. THE REQUIREMENT
As per ICAO Annex 10 Vol I para 2.2.1 ,
Radio navigation aids ( ILS, VOR, DME,
MARKER, NDB, GNSS, ADF & MLS)
available for use by aircraft engaged in
international air navigation shall be the
subject of periodic ground and flight
tests.

3. Type of Inspection
 Commissioning / Re- Commissioning: comprehensive check of
performance of a nav-aid. The facility can not be declared
operational before this check.
 Routine Inspection: To ensure that Nav-aid facility maintained
within tolerance limits.
 Special Flight Inspection: On special request, e.g.
investigation, change of antenna system.
 Site Evaluation Inspection: to determine the suitability of a
site.
 Engineering Support Inspection: Finding Solution to the
imperfect installation site.

4. PERIODICITY OF FLIGHT INSPECTION
 Facility Periodicity
 ILS 150 + 30 days
 DVOR 720 + 60 days
 CVOR 240 + 30 days
 DME As per the associated facility.
 NDB As and when required
 Radar As and when required
 PAPI/VASI (Visual aid) As and when required

5. Flight Inspection System (FIS)
Airborne FIS Equipment
Fully Automatic System : The system has
automatic data analysis and compute results
based on self contained automatic position
reference systems.
Ground FIS Equipment’s:
DGPS base station , UHF link and Laser
tracker.

6. Phases of Flight Inspection
Pre-Flight Procedures: Ensure -
 Ground Calibration of Equipment.
 Availability of Competent Maintenance personnel to
make corrections and adjustments.
 Availability of infra such as DGPS and LT Platform,
last Flight Inspection Report etc.
 Special investigation needs are intimated to FIU.
 Coordination with local ATC for slot and
withdrawal of the facility.

7. Phases of Flight Inspection
In-Flight Procedures on Ground:
 Flight Inspector advises observed conditions and
adjustment required.
 Ground personnel will make suitable adjustments
to align the system.
 Flight inspector verifies and confirm the
performance after system adjustments
 Record the adjustments made, for post analysis.

8. Phases of Flight Inspection
Post-Flight Inspection:
 Record adjustment carried out.
 Carry out Monitor alignments of the
equipment;
 Record measurements on field/ground
for reference in future.

9. Flight Inspection Procedure
of ILS
Localizer

10. Flight Inspection Procedure of LLZ
Coverage Check and Power Alarm: Availability of ILS
signal within its service volume operating on mains &
Battery backup.
Availability of LLZ Signal within the covergae volume is
checked and adjusted as per the requirements of ICAO
Annex – 10 Vol 1:
Adjustment : Course CSB Level ( CSB Power)
Clearance CSB Level

11. LLZ Coverage
 3.1.3.3.2 In all parts of the coverage volume specified in 3.1.3.3.1, other than as
specified in 3.1.3.3.2.1, 3.1.3.3.2.2 and 3.1.3.3.2.3, the field strength shall be not less than
40 microvolts per metre (minus 114 dBW/m2).
 3.1.3.3.2.2 For Category I In Course Sector from 18.5 km (10 NM) to a height of 60 m
(200 ft) above the horizontal plane containing the threshold shall be not less than 90
microvolts per metre (minus 107 dBW/m2).
 3.1.3.3.2.2 For Facility Performance Category II localizers, the minimum field strength
on the ILS glide path and within the localizer course sector shall be not less than 100
microvolts per metre (minus 106 dBW/m2) at a distance of 18.5 km (10 NM) increasing to
not less than 200 microvolts per metre (minus 100 dBW/m2) at a height of 15 m (50 ft) above
the horizontal plane containing the threshold.
 3.1.3.3.2.3 For Facility Performance Category III localizers, the minimum field strength
on the ILS glide path and within the localizer course sector shall be not less than 100
microvolts per metre (minus 106 dBW/m2) at a distance of 18.5 km (10 NM), increasing to
not less than 200 microvolts per metre (minus 100 dBW/m2) at 6 m (20 ft) above the
horizontal plane containing the threshold. From this point to a further point 4 m (12 ft) above
the runway centre line, and 300 m (1 000 ft) from the threshold in the direction of the
localizer, and thereafter at a height of 4 m (12 ft) along the length of the runway in the
direction of the localizer, the field strength shall be not less than 100 microvolts per metre
(minus 106 BW/m2).

12. Flight Inspection Procedure of LLZ

13. Flight Inspection Procedure of LLZ
Course Width and Clearance check:
Purpose:
 Adjust & Ensure Course Width within tolerance;
 Check signal in the sector +10° and + 35° of C/L
Flight Procedure:
 Cal aircraft flies an arc about Runway center line at approx
5 NM from LLZ & 1500’ AGL.
Values and tolerances :
 COURSE WIDTH (W) = W ± 17% for CAT I, II & W ± 10% for CAT III
 Adjustment : SBO Amplitude ( SBO Power) - Course
 Signal in the course sector increase linearly to 175 μ Amps (18%
DDM) till 10° on either side of C/L.
 Minimum Signal in the clearance sector between ±10° to ± 35° sector
should be 150 μ Amps (15.5% DDM).
 Adjustment : SBO Amplitude ( SBO Power) - Clearance

14. Flight Inspection Procedure of LLZ
High angle clearance / High altitude clearance
Need: To eliminate the possibility of operationally false course at
higher altitudes. Due combination of ground environment and
antenna height can cause nulls or false courses, which may not
be apparent and therefore should be investigated upon:
When Required:
 Initial commissioning.
 Change in the height of an antenna;
Procedure:
At 5 to 8 NM, within the angular limit of coverage
provided, at a height corresponding to an angle of 7 degrees
above the horizontal.
Result:
If the minimum clearance at this height exceeds 150
microamperes, and the clearance is satisfactory at 300 m (1 000
ft), the localizer will be assumed as satisfactory at all
intermediate altitudes.

15. Flight Inspection Procedure of LLZ
Course Line, Course Structure & Flyability

16. Flight Inspection Procedure of LLZ

17. Flight Inspection Procedure of LLZ
Course Line Alignment, Course Structure and
Flyability Check
Purpose:
 Alignment of electronic centre line with the physical runway
centre line.
 To check quality of course signals i.e. for Course bends,
Roughness, scalloping;
 Flyability i.e. the aircraft following the ILS can fly smoothly
"manually" as well as on its "auto pilot".
Flight Procedure:
 For CAT – I & CAT – II : Cal a/c carries out ILS approaches
inbound from 8 NM up to R/W Threshold on LLZ and on
Glide Slope.
 CAT – III: Cal a/c carries out ILS approaches inbound from
8 NM and then follows the LLZ approach 50´ above the
RWY up to Reciprocal Threshold .

18. Flight Inspection Procedure of LLZ
Course Line Alignment, Structure
Alignment :
 Course Line and its Tolerance Limits:
 CAT I + 14.6 μA ± 1.5μA ( + 10.5m at the threshold)
 CAT II + 10.5 μA ± 1.1μA (+ 7.5 m at the threshold)
 CAT III + 4.2 μA ± 0.5μA (+ 3m at the threshold)
Adjustment : Course CSB DDM ( Nominal Value 0)
Structure:
CAT I :
• Outer limit of coverage to ILS Point A : 30 μA
• ILS Point ‘A’ to Point ‘B’ : decrease at a linear rate to 15 μA at Point ‘B’;
• ILS Point ‘B’ to ILS point ‘C’ : 15 μA
CAT III/II :
• Outer limit of coverage to ILS Point ‘A’ :30 μA
• ILS Point ‘A’ to Point ‘B’ : decrease at a linear rate to 5 μA at ILS Point
‘B’ .
• ILS Point ‘B’ to ILS reference datum : 5 μA
• ILS reference Datum to ILS Point ‘D’ : 5 μA (for CAT III)
• ILS point ‘D’ to ILS point ‘E’ : increasing at linear rate to 10 μA at
ILS point ‘E’ (for CAT – III)

19. Flight Inspection Procedure of LLZ
Coverage, Monitor Alarms
Coverage Check and Power Alarm: Availability of ILS
signal within its service volume operating on mains &
Battery backup.
Adjustment : Course CSB Level ( CSB Power)
Clearance CSB Level
Monitor Alarms:
Course line alarms on either side.
Course width alarms.

20. Flight Inspection Procedure - LLZ
Monitor Alarms:
Course Line: Alarms for change in Course Line
toward left or right of the Centre Line:
Cat I : + 10.5 m or 1.5 % DDM;
Cat II : + 7.5 m or 1.09 % DDM;
Cat III : + 6 m or 0.88 % DDM
Curse width:
Cat I : + 17 % of Nominal Value
Cat II: + 17 % of Nominal Value
Cat III: + 17 % of Nominal Value

21. Flight Inspection Procedure
of ILS
Glide Path

22. Flight Inspection Procedure - GP
Antenna Null Checks:
Purpose:
To confirm and correct (if required) the height of
G/P Antenna elements above ground.
Periodicity:
Commissioning or after major maintenance of
antenna.
Procedure:
The calibration aircraft flies at 1000'/1500' AGL
on LLZ, from a distance of 8 NM to a point
overhead G/P antenna.
Result: Get correct nulls. Antenna should be raised to
decrease the NULL ANGLE and VICE VERSA.

23. Flight Inspection Procedure - GP

24. Flight Inspection Procedure - GP
Glide Angle and Sector Width check:
Purpose: Determine the Glide angle, sector width
 Flight Procedure:
The calibration aircraft fly in-bound on extended centre
line (level run) at 1500′ AGL from 10 NM to MM.
 Glide angle
Commissioning : No tolerances allowed
Routine :
± 7.5% of θ for CAT I & II (2.775 to 3.225 Deg for θ=3)
± 4% of θ for CAT III ( 2.88 to 3.12 Deg, for θ=3 )

25. Flight Inspection Procedure - GP
Glide Angle and Sector Width check
Half Sector Width (8.75 % DDM)
CAT I & II:
Lower Half Sector Width 0.10 θ to 0.14 θ.
Upper Half Sector Width 0.07 θ to 0.14 θ.
CAT III:
Lower Half Sector Width 0.10 θ to 0.14 θ
Upper Half Sector Width 0.10 θ to 0.14 θ

26. Flight Inspection Procedure - GP
Glide Path Structure:
On the Glide Path the deflection current (DDM) should
not exceed:
CAT I
Coverage up to point 'A' : ± 30 μA
Point ‘A’ – ‘B’ - ± 30 μA
Point ‘B’ – ‘C’ - ± 30 μA
CAT II & III
Coverage to point ‘A’: ± 30 μA
Point ‘A’ – ‘’B : Linear decrease from ± 30 μA to ± 20 μA at ‘B’
Point ‘B’ – ‘T’: ±20 μA

27. Flight Inspection Procedure - GP
Monitor Alarms:
Glide angle:
Alarms for change in glide angle below or above the
angle:
Cat I : + 7.5 % of θ;
[Cat III : + 4.5 % of θ]
Sector width alarms.
 Narrow width alarm: - 25 % of Nominal Value
 Wide width alarm: + 25% of Nominal Value

28. FLIGHT INSPECTION
DVOR
Radial Check:
Purpose:
 Check quality of course signals, Course bends,
roughness, scalloping.
 Minimum 8 radials, at least one in each
quadrant including PDRs.
Flight Procedure
 Calibration A/C flies on enroute radials either
inbound or outbound to a distance of 40 Nm.
1000 ft above the highest terrain. .

29. FLIGHT INSPECTION
DVOR
5 Nm Orbit :
 Purpose:
- Adjust North bearing, determine the
accuracy and overall alignment error.
- To Evaluate the error in azimuth alignment ,
the roughness and scalloping.
 Flight Procedure:
- Calibration aircraft flies an orbit radius of 5
Nm or more in a Counter Clock wise
direction at 1000’ AGL or above.

30. FLIGHT INSPECTION
DVOR
Orbit Checks
 25 Nm Orbit :
 Purpose:
- To Evaluate the error in azimuth alignment ,
the roughness and scalloping.
 Flight Procedure:
- Calibration aircraft flies an orbit radius of
5 NM or more in a Counter Clock wise
direction at altitude of 1000’ AGL or above.

31. FLIGHT INSPECTION
DVOR
Other Checks
 Coverage
 Sensing and Rotation.
 Identification Coding
 Modulation Level
 Polarization
 Monitor Alarm

32. FLIGHT INSPECTION
CNS FACILITIES
From the perspective of
Aviation Safety
Suresh Kumar Sharma