Approaches: ILS/LOC Flashcards
Is an ILS a Precision or Non-Precision approach?
Precision, provides both Lateral and Vertical guidance
What are the 3 Categories of ILS components and what do they entail?
- Guidance information
- Localizer, lateral guidance from centerline
- Glideslope - Vertical guidance, descent path, usually a 3 degree descent path - Range information
- DME, co-located with the localizer
- Marker beacons, Outer, Middle, and Inner - Visual Information
- Approach lighting and RWY lighting
How do you tell if the ILS/LOC has DME?
- Jeppesen charts will have “ILS DME” located on the Localizer feather
- Notes MAY state “DME requried”
What uncommon range element MAY be associated with an ILS OM and MM?
- Compass locator - used to identify OM & MM (LOM/LMM)
- DME - Collocated with the GS transmitter
What are the 3 Categories of ILS approaches?
Cat 1 - Approach may go down to 200ft ATDZE
Cat 2 - Approach may go down to 100ft ATDZE (require specially certified pilots and specific equipment)
Cat 3 - Allow for even lower minimums *(require specially certified pilots and specific equipment)
What is a Localizer, how far out does it go, and how high can it be received?
A ground facility that radiates a two overlapping frequencies down the extended centerline of the RWY
- 35 degrees wide up to 10 NM from the Loc
- 10 degrees wide up to 18 NM
- Transmits up to 4,500ft
- Full scale deflection is 2.5 degrees wither side, or 5 degrees total
What is unique about the letter identifier for an ILS?
It will start with an “I”
What are the range limits of the ILS Localizer antennae?
- 10 NM out, up to 35 degrees either side of the centerline
- 18 NM out, up to 10 degrees either side of the centerline
*This is the distance at which the localizer will be come ‘alive’
What is full scale deflection on a Localizer?
Full scale deflection on the HSI is 2.5 degrees either side of the RWY
What is different about tracking a Localizer vs tracking a VOR radial?
The localizer is 4x more sensitive than a VOR
Why do we intercept the GS from below?
To avoid false glideslope indications, which may indicate a higher rate of decent than the typical 3 degrees.
What is a false glideslope indication?
When the radio frequencies deflect higher into the air and falsely display a 9 or 12 degree descent slope.
What are the frequencies be transmitted by both the GS and the LOC?
Localizer - 90Hz = Left of center. 150Hz = Right of center
GS - 90Hz = High. 150 Hz = Low
How wide is the Localizer signal as it crosses the landing threshold of the RWY?
All Localizers are positioned so that they are 700 FT wide at the RWY threshold.
(350 FT on either side of the centerline)
Why are Localizers more sensitive on longer RWYs vs shorter RWYs?
Due to the standard requirement for the width of the frequency transmission to be 700 FT wide at the RWY threshold.
Where is the Localizer located relative to the RWY?
Normally placed 1,000ft off the departure end of the approach RWY.
Does a GS provide back course signal transmission?
NO, if you are receiving a GS on a BC, you are likely getting a false GS
Do you normally see Inner Marker (IM) beacons on Cat 1 approaches?
No, usually Cat 2
- they indicate decision height
What is the purpose of Marker Beacons?
To help pilots determine their position along an approach course. Usually FAF and DA/MDA
What does LOM mean on a chart?
Localizer Outer Marker (usually at the FAF) and usually associated with an NDB
Where is the Outer Marker (OM) located on an ILS and what does it indicate?
- 4-7 miles from the localizer front course at the FAF
- It indicates the point at which GS intercept should occur.
Where is the Middle Marker (MM) located on an ILS and what does it indicate?
- 3500ft from the threshold, 200ft above TDZE
- Usually indicates Cat 1 DA
*Middle Markers are rare
How will you know when you are crossing the Outer Marker?
- Blue light will flash
- Low pitched continuous DASHES
How will you know when you are crossing the Middle Marker?
- Yellow light will flash
- Sequential DOTS & DASHES
*“bip BEEEP bip BEEEP bip BEEEP
How would you know you were crossing the Inner Marker?
- White light will flash?
- Sequential DOTS
*“bip bip bip bip bip”
What does a Back Course Marker (BCM) indicate?
The FAF on a Back Course approach
What does an Outer Marker look like on an IAP?
Plan view: Football shape
Profile view: Fuzzy upward facing cone shape.
What ILS errors may be experienced? (5)
- Reflection - Cars, airplanes, or other objects may disturb the signal below 5,000ft AGL
1.5. False Courses - GS frequency may be transmitted above the standard 3 degree slope, up to 12 degrees. Causing the needle to act erratically. However; this should not occur if you intercept the GS as depicted.
- Failure to understand that ILS/LOC intercepts are more sensitive than a VOR
- Disorientation - Failure to properly set yourself up for the IAP due to a lack of SA
- Incorrect Localizer Intercept - choosing too high of an intercept angle will cause you to overshoot the LOC
- Chasing the needles.
When briefing an IAP, what all is required to go over per procedures?
PUT SIMPLY:
1. Everything up to the Plan view
2. Everything after the Profile view (
Timer/VDP)
+
3. NOTAMs
4. TAXI route
5. Special considerations
*additionally, go over how you will fly the route (altitudes, holds, course reversals etc)
What is important to remember in regards to a Glide Slope on a Localizer Back Course approach?
The Glide slope should be disregarded on a Back Course approach
- False glide slope indication are likely to exist on a back course, thus they are unreliable.
What are the dimensions of the Glide Slope?
- 1.4 degrees wide vertically, full scale deflection is 0.7 degrees either side
- Typically have a 10 NM range, sometimes more
- Slope will be between 2.5 & 3.5 degrees
If an ILS has an Outer Marker (OM), will there also be a Middle Marker (MM)?
No, if the is an OM there is typically no need for a MM.
How will you know you are passing the Back Course Marker?
“Beep, beep….. Beep, beep”
- It will flash white
What is the most common Category of ILS approach flown in general avaition?
Category 1 approaches.
What does an ILS Category 1 approach allow us to do?
- Descend down to 200 ft
- Have an RVR of 2,400ft
- Have an RVR of 2,800ft if touchdown zone and centerline lighting are available
What is an important thing to note when considering the obstacle clearance along the final approach segment of an IAP?
Obstacle clearance minimums for the final approach segment of an IAP can be as low as 250ft !!
- This is why its so important to remain at or above DA/MDA
What is important to remember in regard to lateral navigation along a Localizer Back Course approach?
- It is possible to get reverse sensing on a BC
- The G1000 can eliminate reverse sensing if BC mode is shown as operational by ‘BC’ appearing green in the Autopilot box
**If the AHRS fails, you will get reverse sensing on a Loc BC approach
What is important to remember while performing a Localizer Back Course Approach with an AHRS failure?
You will get reverse sensing, make your turn away from the needle.
Which is less desirable on an approach, the GS diamond being too high or too low?
The GS diamond being too high is less desirable, this mean you are BELOW GS and may not have proper obstacle clearance
What are the typical false glideslope error degrees?
6, 9, and 12 degrees.
