Questions in the title. Asking because I wanted to try an ILS landing (which I understand) at Innsbruck but it only has LOC and RNAV options.
Cheers
ILS - Instrument Landing System.
It uses radio frequencies to help the aircraft navigate the Approach and landing at an airport. Olden days it was on radio frequencies. The radio waves provided a Localizer (LOC) and Glide Slope (GS). The localizer told you how far left or right of the runway approach you are and the GS shows you how high or low you are on the approach. You tuned the LOC frequency on you NAV receiver and watched a dial on the instrument panel that had a vertical bar and horizontal bar… You keep them in the middle of the dial.
Now we are in the future. GPS is the way to navigate. So you now have the GPS database has/shows imaginary waypoints the the GPS computer knows. Imaginary as there is no physical device at the waypoint. These are the RNAV approaches. RNAV is aRea NAVigation.
edit = got ninja’d
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Well, I’ll try to keep it simple.
In Innsbruck, an ILS approach is not possible because due to the surrounding terrain. Therefore, there is only a LOC (localiser, providing lateral guidance) with an approach track which is about 3° off the RWY track. In addition, there is a GP (glide path, but not a glide slope which would be required for an ILS) which provides for a vertical guidance of 3.77° (instead of the standard 3° GS commonly used in ILS approaches).
By contrast, RNAV (or RNP) approaches do not rely on ground stations sending signals but on satellites. Therefore, these approaches can be drafted in a much more flexible way. Depending on the actual aircraft’s capabilities, RNAV-approaches can either be lateral only, provide vertical guidance with reference to barometric altimeters (LNAV/VNAV) or very precise vertical guidance (LPV).
As to Innsbruck, RNAV approaches can basically lead you down to the runway with no offset whereas the LOC/DME approach requires the pilot to manually correct for a few degrees before touchdown. Therefore, the LOC/DME-approach have really high decision altitudes for IFR approaches.
As to LOWI, I suggest having a look at the official charts published in the AIP of Austrocontrol (see https://eaip.austrocontrol.at/lo/200814/ad_2_lowi.htm). Please note that the LOC/DME approach charts refer to the visual approach chart for the last segment before touchdown which has to be flown in VMC.
One final note: In order to fly conventional approaches (in particular VOR-, LOC- or ILS-approaches), be sure to have to correct frequencies tuned in, the correct CRS set (G1000 should do this automatically) and the mode in the G1000 set to “CDI” - your needles are green. For RNAV approaches, you have to be in GPS mode (magenta needles).
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I am researching this as well. I believe RNAV approaches use the GPS approach procedure. There will be predetermined altitudes with each step of the approach. I think the plane should descend to these preset altitudes automatically. However, I have not been able to do this type of approach yet.
LOC stands for Localizer. There is a radio that broadcasts signals which assist your Autopilot in lateral alignment with the runway. Tuning to LOC also tunes in the GlideSlope which provides radio information vertically, assisting your Autopilot in changing altitudes during approach. The glideslope is usually a 3 degree slope from the runway. So your Autopilot will follow the vertical and horizontal (lateral) radio guidance and you touch down on the runway. However, you are in charge of your airspeed which you should be decreasing during the approach until you hit the recommended landing speed base on your plane. The AP will also need assistance to maintain its alignment with the glideslope so you may need to throttle up or down as needed.
Basically true with one remark I would like to make: Approach types have nothing to do with the AP. The autopilot does nothing but following the needles provided by the avionics in the same way the human pilot is trained to do.
The autopilot only follows the vertical guidance of an approach (ILS or RNAV) if APPR-Mode is selected. Be sure to intercept the approach mode from below the GS - some systems do not allow the GS to be intercepted from above for safety reasons. Typically, you fly at constant altitude (ALT hold) to the FAF (Final Approach Fix), press the APPR button which arms the approach mode, and as soon as the aircraft intercepts the GS, ALT hold is disengaged and the AP switches over to APPR mode, following the GS down to the runway. Obviously, this does not work if the approach does not provide vertical guidance (VOR-approach, for example).