Radio-NAV = Radio Navigation

Audio Control Unit ADF / NDB COM/NAV-Radios The Controls of the Radios: "Easy -SetUP": The NAV-Radio = VOR & ILS OBI: The VOR/ILS Indicator Standard VOR Procedures Directly flying towards a VOR:  Intercepting a radial to follow: Define your position with 1 VOR + DME Define your position with 2 VOR (NDB): Finding a "FIX"-point ILS (Instrument Landing System) COM/NAV-Radio 2 Autopilot DME IAP: The"IFR-Approach-Procedure" e.g.: KLVK ILS RWY 25R Analyzing the IAP: MAP

The Radio-Stack inside a C172p

Audio Control Unit

The rotary-switch at the left side connects the microphone with the transmitter wanted. Below that there are the 3 lights with special meanings during the final approach: Outer-Marker: The blue light and a sound of 400 Hz, positioned between 4-7 mi out Middle-Marker: The amber light and a sound of 1300 Hz, positioned between 0.5 to 0.8 mi out Inner Marker: The white light and a sound of 3000 Hz - signaling you are over the Touch-Down-Area of the runway!

ADF / NDB

• OFF/VOL: See that smaller rotary-button labeled Off/VOL. You can operate it as usual by mouse-clicks into the hotspots or by the mouse-wheel.
  • When turned all the way left it will switch off (and the display gets dark) - in all other positions it will vary the volume of the Morsecode transmitted from the NDB.
  • Unfortunately, at the time of writing, the indent function does not work yet, so for now you can only use the "on/off" function.

• ADF/ANT: In the most left side of the display there may be written"ADF" or "ANT", you switch between those two modes by pushing the ADF-button:
  • You need the "ADF" mode to navigate - so watch that this one is active when flying
  • The "ANT" mode is used in reality to indent a NDB, because it gives better audio reception. While in this antenna mode, however, the ADF will not point to the station - the needle will then be parked pointing directly to the right!

So make sure you always have the "ADF" sign in the display!

• BFO: The additional BFO-mode enables the device to receive the Morse-code also from "non modulated transmitters" -- we do not use this!

• FRQ: Switches between the 2 preselected frequencies:
  1. The "selected" (active) frequency, displays on the left - that is the the NDB-frequency where our ADF-needle points to. Watch it: If the needle just points straight to the right and does not move when changing the heading - then you are not receiving any signal! (Check that you are in "ADF"-mode and that the "selected" frequency is in range!)
  2. The "standby" frequency is the one you will use when pushing "FRQ". Only this frequency you can change by the big dial on the right! Use that as usual:
     • by moving the mouse-pointer over the dial and rotate the mouse-wheel
     • or click with the mouse into the hotspots left or right, left button for small steps, center button for big steps
     • or use the "Easy-Setup"

• FLT/ET: pushing this button will replace the displayed "standby-frequency" with a clock, and and when pushed multiple times it changes between the modes FLT and ET:
  • FLT = Flight Time: Displays the passed time since you started FlightGear
  • ET = Elapsed Time: Is a Stopwatch, which is then controlled with the button SET/RST

To display the standby-frequency again: Push FRQ

• SET/RST: Sets the Stopwatch to "0" and starts it at the same token. So you cannot do a stop/continue!
  • Watch it: Hitting this button will always reset the Stopwatch, independent of if you see it or not! e.g. even when you are in the "Flight Time" mode! That is sometimes a little confusing (for people like me)! So watch it.

• HD (left lower corner of the "ADF display" (see above picture in the center):
  • Turning that knob will rotate the internal wind-rose in the instrument. That does not influence our course etc. - but if you (manually) set that to the same heading as the "Heading Indicator", then the ADF-needle does not just point to the NDB-location, but also gives you the real heading to it. 
  • May be you want to change your course at a certain point of your course (e.g. 46° to a certain NDB), then you
    • adjust the NDB-scale to indicate the same as the "Heading Indicator"
    • then you turn when the ADF points to 45°

(That is laborious? Yes, it is. And Yes: There are instruments that link the scale automatically with the "Heading Indicator", but those cost extra money - what we poor Private-Pilots do not have!)

COM/NAV-Radios

1. The "COM"-radio (the left half of the above unit): That is the radio for communicating with the outside via MPchat or FGCOM, etc., may it be with other "Multiplayers" or with "Artificial-Intelligence Functions" (like e.g. AI-ATC).
2. The "NAV"-radio (the right half of above unit): That is the radio for Navigation to tune in to VOR and/or ILS transmitters.
3. The "NAV"-display" (the right picture)
   • displays the instructions from VOR or ILS transmitters, as well for the horizontal directions (radial or localizer) as for the vertical direction (GS = GlideSlope)
   • has a knob (down left) for setting the wanted "radial" to be tracked

The Controls of the Radios:

• Volume: Beneath each Radio there is a small rotary knob to adjust the volume. If you turn the left one all the way to the left, it will switch off the complete unit.

• Display: There are always 2 frequencies shown: On the left the "selected" and on the right the "standby". That way you are able to preselect a frequency to be used later while you continue to work with the "selected" one. You can only adjust the "standby" one - and then exchange the both by clicking onto the white button underneath the display.

• Frequency: You set the frequency using the bigger knobs at the right, by
  • clicks with the left mouse-button into the hotspots at the knob - that adjusts the frequency in small steps
  • clicks withe the central mouse-button/wheel into the hotspots - that adjusts the frequency in bigger steps
  • rotating the mouse-wheel inside those hotspots
  • type the frequency into a GUI - see the following chapter about the GUI "Menu → Equipment → Radio Settings“ - that one has the advantage that you can set ALL frequencies for both (standby and selected!) and at the same time also ADF, DME, TACAN, Radials etc. - see the following chapter "Easy-Setup".

For the VOR-frequencies: After you have set a VOR-frequency, first turn up the radio-volume and listen and check it's Morse-coded identification! Because especially in high altitudes you will find many, many VORs and even some with the same frequency! You only can be sure to have the right VOR when you hear its Identification! In the simulator that may be worth a laugh - in real life that could become very, very critical!

"Easy -SetUP":

e.g.: Click onto "KRHV", that will present a sub-GUI with the available frequencies. Set the ones wanted into the COM's in above "Easy Setup". e.g.:

125.20 → into COM1 Selected, to first listen to the ATIS at KRHV

119.80 → into COM1 Standby, which you will use after that (notice: There is no "GROUND" at KRHV!)

The NAV-Radio = VOR & ILS

• VOR-transmitters may be located anywhere. They send out long-ranging radials, covering all directions of the wind-rose. Depending on the surrounding area you may be able to tune to it already 100 mi out (but e.g. not in a 20 mi distance, if there is a mountain between you and the VOR!). On maps you notice VOR's by the Windrose-Scale around them (see below).
  
• ILS-transmitters are always located directly at a unique runway and do send out only one single "radial" - that is the heading of the runway, called the "localizer"! You may be able to receive a localizer up to 50 mi. out
  
• In addition the ILS may send a Glide-slope Signal (GS) - which functions exactly the same as the localizer - but guides you vertically to the "Touch Down Area" of a unique runway. The GS-signal usually only reaches 10 mi out from the threshold!
  

In the graphic on the left you see 2 VORs, named "OAK" and "SJC". Let us analyze line by line what a typical aeronautical chart tells us about e.g. the "VOR SJC" (see it outlined in the right lower corner): VOR-DME: tells us, that this is a civil VOR with an integrated DME. (In the left upper corner you see the example of a military VOR ==  the VORTAC "OAK"). SAN JOSE: is the full name name of that VOR (which you cannot use e.g. in a  Route-planer) 114.1 Ch 88 SJC ... 114.1 : is the frequency you would have to set into your NAV-radio Ch 88 : is a frequency for another type of NAV-radio (which we will not use) SJC : is the UID for that VOR (which you would set into a route-planer) "...  .---   -.-." is the Morse-code for "SJC", which is transmitted and should be used by you to identify the station! You hear those dashes and dots as longer and shorter sounds on your radio - between each letter there is little pause. During the flight the OBS of the VOR tells the Pilot on which magnetic bearing to or from a VOR he is flying. Most VOR's will indicate also the distance (see DME) to it. The bearings are in magnetic degrees and are called "radials". In the graphic on the left you see 2 bearings: 1. "114° FROM" coming from the VOR OAK 2. "002° FROM" coming from VOR SJC Those two radials happen to meet somewhere, and this unique meeting point is given a special name: "MISON". Thus it is a very important "FIX"-point in the Bay-Area! Such a FIX is not seen during strict VFR-navigation, because it is just a crossing of two radio-signals - so do not try any sightseeing for it! By defining such FIXes traffic can be routed not just by defining VORs as way-points, but also by the crossing of two radials. Those FIXes are very often used as "waypoints" in Flight-plans, as Reporting-Points for ATC, etc.

OBI: The VOR/ILS-Indicator:

OBS = "Omni Bearing Selector": When you rotate the knob at the lower left corner, the wind-rose-scale inside the instrument will rotate too - placing the currently selected radial at the very top of the scale: See e.g. the value "N" (= 000° or 360°) in the picture. With this setting you fly with a heading of 360° "TO" (=North) or "FROM" (=South) the VOR-transmitter. CDI = "Course Deviation Indicator": This is the vertical needle inside the VOR-display. If that needle is vertically centered, it tells you that you are on the selected radial -  if not, it indicates into which direction you have to correct your heading in order to return to the radial. GS = "Glide Slope": The horizontal needle in the instrument functions like the CDI, but in the vertical direction! Watch it: A "Glide-Slope" is only available from some ILS transmitters, and its signal usually reaches only 10 nm out from the "Touch down Area" of the runway.  The GS becomes active a long time later then the CDI - which is active already 50 mi out and more! TO/FROM: Do you see that little cutout at the right side of the center, now indicating "TO"? In that window will appear a "TO" when the radial brings you towards the VOR - otherwise it will show a FROM (or short "FR"). If neither "TO" nor "FR" is indicated you are not inside a valid range to a VOR with that frequency!   To make it very clear: The "TO/FROM" indication does NOT indicate in what direction you actually fly - it just tells you in what direction the radial points - so yes: Although when flying on a radial "FR 270" and a centered CDI you may very well be flying towards the VOR! But in case you deviate from the radial, the CDI will indicate the needed correction reverse! Have a look at all 4 possibilities and there effects: Radial Your Position Compass ° OBS ° CDI function when flying eastbound: TO 090 WEST of the VOR 090° 090° normal: Showing left when you should correct to the left FROM 270 WEST of the VOR 090° 270° reverse: Showing left when you should correct to the right FROM 090 EAST of the VOR 090° 090° normal: Showing left when you should correct to the left TO 270 EAST of the VOR 090° 270° reverse: Showing left when you should correct to the right

• So we have used the OBS to set the compass-rose to 002°  (actually you hardly can do that very precisely with that instrument - so I suggest to use the Easy-Setup to input that value.)
• In the example the CDI points slightly to the left - telling us we should correct our heading in order to get (back) onto the radial
• we obey that by turning about 10° to the left - i.e. to a heading (on the Gyro-Compass) of about 350°
  
• if the needle remains as is or even moves more to the outside, then we increase another 10° to the left (on the Gyro-Compass now about 340°)
• if that still does not help add another 10° - but you should not need more then 30° for correcting. Be patient: Depending on how far you are away from the VOR it may take quite some time to see a noticeable change! Do not overreact!
• when the needle starts to move back to the center, wait until it is shortly before the centerline - and then turn back to your course
• in case you have to repeat these corrections again and again (i.e. because of heavy crosswinds), then correct your heading (according to the Gyro) in that a way, that the CDI remains centered. e.g. keep a heading of 355° (7° against the wind) in order to stay on the radial/course of 002°!
  

HSI: Horizontal Situation Indicator

The HSI is a combination of the OBI and the Heading indicator. It is somewhat more expensive - and thus not in our c172p! If you want to know more about it see: http://en.wikipedia.org/wiki/Horizontal_situation_indicator

Standard VOR Procedures

	Specifies a VOR without DME
	Specifies a DME without VOR
	Specifies a combined VOR-DME, for both functions you need to set only the VOR frequency (the unique DME -frequency will be set automatically!)
	Specifies a TACAN (= a military VOR), those always include a DME, but no VOR for civil usage!
	Specifies a VORTAC, the all-in-one solution: It combines the civil VOR-DME + the military TACAN! It does have different frequencies for military and civil usage, and both set the unique DME-frequency automatically

Directly flying towards a VOR:

• Set the VOR-frequency into the NAV-radio and move it into the left display ("selected")
  
• increase the volume to listen to the Morse-code - make sure it is correct, because there may be several VORs with the same frequency!
  
• Rotate the OBS until the CDI centers AND the "TO/FROM" indicates "TO"
  
• when you rotate the OBS "wind-rose dial" a full circle (360°) the "CDI" will center 2 times: Once on the radial "TO" and once on the "FROM". Check your little "TO/FROM" flag and continue rotating it until the CDI is centered while "TO" is indicated.
  
• if you do not get any indication check for
• is the set frequency correct -- and is it in the LEFT display of that NAV that you are tuning (remember: you have 2!) ?
• is the VOR in range (max about 100 mi) or may there be mountains between you and the VOR ?
• is the NAV switched on? (Well: Probably it is when you can see the frequency in the display!) ?
  
• Follow the CDI-indication as described before
• When the CDI suddenly deviates very fast AND the "TO/FROM" changes to "FROM" --> then you arrived over the VOR. You now should either:
• just continue on the same course
• report to ATC that you arrived over the VOR, if ATC advised you to go to that VOR (and maybe go into a "Procedure Turn")
• or change the course as you planned

Turning to a new direction over VOR

• While letting George (autopilot, i.e.: You must use NAV-1!) keeping the CDI centered as described above, we already set the "red bug" within our "Heading Indicator" to the new heading (but do not yet activate that heading!)
• Wait till you notice that the TO/FROM starts moving - then push "HDG" (button on the autopilot) and George will directly turn, even though he might not be over the VOR yet!
  
• While George is still turning set your OBS (that is not in use now) to the new radial
• and check that the "TO/FROM" now indicates "FROM"
• or even change to the next VOR and tune it in - in that case "TO/FROM" would have to indicate "TO"
• And then order George to follow again the CDI (e.g. push the "NAV" button on the autopilot!)
  

 Intercepting a radial to follow:

Before TakeOff set the VOR-FFM frequency 114.20 and the course=radial 270° into your OBS. (Just for learning: Notice that Frankfurt also had a big Military mission - so that VOR is mixed: See the function VORTAX and the frequency "114.20" for the civil operations and the TACAN "089X" for military users!) After TakeOff (and clearance by ATC) go onto a heading that should intercept the wanted course in an angle between 30-60°, i.e. if the departure was to the north: turn left  to a heading of about (270-30=) 240° to the south: turn right to a heading of about (270+30=) 300° The interception-angel of 30° is pretty ideal to intercept without overshooting - if the angle becomes bigger than 60° you definitely will overshoot and will need several retries prior to be centered on the radial! Make sure that the OBS shows "FROM 270"! (Otherwise you may end up in Moskau instead of in Paris!). Watch your instrument closely when approaching the interception point: As soon as the CDI-needle starts to move towards the center start turning to the heading set in the OBS (in this case 270°) and then follow the radial by keeping the CDI centered. e.g. if the CDI-needle moves left - turn left a little more. Start with about 10° (in this case hold a hdg of 260°) - if that does not cause the needle to start moving back into the center, increase the turn to the left, may be another 10°, and so on. But be patient: As you get further and further away from the VOR the time to see a change in the OBS will increase, because the difference (see the red circled "1") becomes larger and larger and thus the time for a noticeable change in numbers (i.e. instruments!) will increase!

DME">Define your position with 1 VOR + DME

• Tune one of your NAV-radios to the frequency of the wanted VOR in your area (depending of your altitude inside an area of 100 to 200 mi) and switch the DME-Selector to that NAV.
  
• You should now directly see the distance to that VOR (if not: That VOR may have no DME, or you mis-adjusted the frequency, or..)
• Now turn the little knob at the left lower side of the OBS until the CDI is vertically aligned. It does not matter if that is a "TO" or a "FROM" radial, but note what it is --> You will need it later to define the direction on the map!
  
• If you need a very exact positioning take an aeronautical map for the following
  
• if it is not that important you may also take a street-map (and maybe convert the VOR magnetic heading to a cartographic heading! (Compare "The Route")
  
• Draw a straight line crossing through the VOR location under the angel of the radial, it does not really matter if it is TO or FROM - the line is good for both!
  
• Now see the scale of the map and mark that on the straight line! And now it is important what "TO/FROM" radial you use! (See above!)

Define your position with 2 VOR (NDB):

Finding a "FIX"-point

• In this example we will try to find the FIX "MISON", which is at the crossing of two radials (ref. the Sectional at the beginning of this chapter and also the usage during the IFR-Cross-Country)).
• So we set our NAV-1 to 114.1/002 and NAV-2 to 116.8/114 (compare the "Easy-Setup")
  

• First we need to intercept the Radial "NAV-1 FROM 002" (See above how to do that). And we make sure we are and remain centered on that radial (may be the Autopilot could help during our first tries!)
• Then we wait until the NAV-2 CDI starts moving
• then it may be a good idea to check if it is moving into the right direction - i.e. are we still before or already after the crossing?
• I admit: I always had problems with that - nowadays I just move my "mind" into the VOR2 and look from there onto the NAV-2 CDI:
• If that points to the right it tells me: Correct the heading to the right to get back onto the radial -- i.e I am left of it --> that means I crossed already
• If that points to the left it tells me: Correct the heading to the left to get back onto the radial -- i.e. I am right of it --> that means I did not yet cross
• Compare: The_NAV-Display
  

•  When both CDI's are centered you are exactly over that FIX. But do not look out of the window trying to find anything: It is just the crossing of two radio-signals -- there is nothing to be visualized!

ILS (Instrument Landing System)

• they do send only one very unique radial with the exact runway heading, which is called the "localizer" - i.e. you cannot change it! "Wonderful - I do not have to care about the radial!!" you might say - and you are right: You do not have to set it - in the "modern" Cessna -
  
• but there are other models, where the CDI is not automatically tuned. In those models you will not see how far you are off the "localizer" if you did not set the radial. 
• and if some day you have enough money to effort a modern, expensive HSI, then you do have to set the runway direction for it's operation (have a look above at the HSI!)
  

==> So it is a good practice to set it always - to make sure you do not forget it when needed!

• most of them do send an extra signal, called the "glide-slope" (GS). That works like a CDI - but in the vertical direction. The function is the same: The horizontal needle tells you in what direction to correct:
• if the needle points upward: Do add power to reduce the speed of your descent
• if the needle points downward: Do reduce power to increase the speed of descent

• watch it: The GS usually gets active only in a range of about 10 mi - thus you might be following the CDI since a long time (up 50 mi out) prior that the GS gets active - most students get nervous and believe the GS does not work, but I hope you know now - and just be patient!
  

•  the localizer is 4 times as sensitive as a VOR-CDI

In KSFO you see the example of an "ideal " setup: There is a VOR-DME in the center of the Airport.  So here you can use the VOR as support to get you onto the ILS-localizer, and have a pretty exact distance measurement as well for the VOR as the for the ILS and or Glideslope! So you can use the your NAV1 for the ILS NAV2 for the VOR (inclusive DME)

In EDDf it is just a little more challenging. There also is a VOR - but a little outside, which is still good enough for aerial-navigation. But see the symbol - it does not have a DME! But there is a standalone DME in the center of the airport. (For that one is shown in FGFS only the military frequency. If you look into other (newer) navigational maps you see it has a distinct civil frequency of 115.9 MHz (see e.g. http://www.ourairports.com/navaids/FRD/Frankfurt_DME_DE/). That means you need to set 3 frequencies: 1) Set the VOR 114.2 into NAV2 2) Set the DME 115.9 into NAV1 3) Set the DME-Selector first to "1" to get the DME 119.5 indicated in the DME-display then switch to "HOLD" --> that holds the DME, even when changing the NAV-frequency 4) Set the ILS-frequency into NAV1

1. Set the ILS frequency into the NAV - if you want to use the autopilot it must be the NAV-1!
   
2. As explained above it is suggested also to set the localizer/radial to the runway heading
   
3. Between 30 to 50 mi out, the ILS should become active, .i.e. the CDI starts to point into some direction AND the "TO" flag should get visible. Be aware of:
   
• When you come from a direction opposite to the runway-heading, that indication is most probably reversed! (e.g. during Downwind)
  
• The same happens when executing a GoAround and thus flying in the reverse direction of the localizer!
• If the NAV + CDI + TO/FROM do not start to indicate about 30 mi out, it is time to recheck the set frequency, look for mountains in your approach, etc.
  
4. In a range of 5 to 20 mi out you should intercept the ILS localizer. If your airport informations do not say otherwise do that a little higher then the pattern altitude, which usually is about 800 to 1000 ft above airport altitude.
   
5. Follow the CDI on that altitude, till:
• Starting about 10 mi out, the GS will become active.
  
• At that point your altitude should be LOWER then the GS! i.e. the vertical needle should point upward.
• Most students then get nervous and try to follow the needle - that is wrong - wait till the needle gets down into a horizontally centered position, indicating that you intercepted the GS!
• That is especially important if you use the AutoPilot: If you activate the GS when you are not already on the GS then the plane may jump upward/downward and you may loose control!!
• (That problem seems to be solved in the newest version of the c172p (higher than FlightGear 2.0!) - but you better stick to the above procedure to get used to it for other models!)
  
• If at that point you are much higher then the GS you definitely should consider a "GoAround". Because when forcing the plane down at that point, it might destroy all your nicely balanced actions for the "Final" - and you are the first who is (should be) ashamed of yourself! Remember: It is fun - no emergency or air-show!
  
6. Start the descent only AFTER the GS-needle crosses the centerline - from now on you can follow the needle (or activate the Autopilot GS)
   
7. Being on "Final" you should notice on your instrument panel 3 signals before "Touch-Down":
1. Outer-Marker: The blue light and a sound of 400 Hz, positioned between 4-7 mi out
2. Middle-Marker: The amber light and a sound of 1300 Hz, positioned between 0.5 to 0.8 mi out
3. Inner Marker: The white light and a sound of 3000 Hz - signaling you are over the Touch-Down-Area of the runway!
   

COM/NAV-Radio 2

Autopilot

• Switch off the Autopilot before any "TakeOffs" and "Landings"! Otherwise you are up for very funny surprises! Even when landing with AP-ILS: Do switch off prior to Touch-Down!
• Yes, I know: There are models that can do a complete landing (including speed and leveling off - the Concorde is a perfect example for it!) -- but that are only a few - and for sure not the Cessna!! 
• When you switch off, switch off the whole device because it is very difficult to predict which functions will remain active or become active when you switch off only certain functions (e.g. the "ROL" will stay active, etc.)
• Remember the delay! The AP will never switch off at once - it always first blinks some time to warn you - and then switches Off after that! Try it and notice how long that takes!
  

• AP (Autopilot) switches the AP-unit on/off.
  
• When you switch on the AP the very first time, it will read all the needed status-informations and controls at that time only. The following are typical values displayed in the upper line after the initial start:
  
• "ROL“: The AP keeps the wings leveled
  
• "VS“: The "vertical speed" continues active - e.g. the current climb or descent will continue
• "00000“ the wanted cruise altitude is reset to 0 !!
• You should set the wanted altitude as soon as possible! Otherwise the AP will try to climb to the moon or descent to sea-level!!
• Change that soon - see "ARM" below

• For cruising we will change the AP-settings to show that first line like in the picture above:
  
• HDG: The AP will hold the heading set in the Gyro-Compass
• ALT: The AP will hold the current altitude
• 04000: The Altitude to be hold is 5000 ft

•  AP-Error-Indications: Above the AP-button there may show up 2 error-indicators as red letters:
• P: The AP cannot control the "Pitch" (elevator/trim) - the AP may switch off.
• R: The AP cannot control the "Rolling" (ailerons) - the AP may switch off
  

• HDG (Heading) will switch the upper left indication between "ROL“ and "HDG“.
• "ROL" just keeps the wings leveled
  
• "HDG“ will turn to and hold the heading defined by the "red bug" in the Gyro-Compass. When you move the bug the AP will immediately follow that new setting (even while in transfer!). And it will always take the shortest way to the new setting. That may result in a problem:
  
• let us assume you are flying a heading of 000° and ATC advises you to "turn left to 090°"
  
• then you probably start turning the red bug to the left to go to the new heading - and the plane follows turning left
• BUT: You can turn the bug that fast, that there will occur a gap of more than 180° between the bug and the actual heading achieved
• that means: The plane suddenly turns the other way - because the initial turn is now greater 180° - thus the other one now is less than 180° - and thus shorter!
• so when turning more then 180° you must turn in steps smaller 180°. e.g. in this case you first turn the bug left to 190° - and shortly before the actual heading reaches that 190°continue to move the bug to the 090°!!

• NAV (Radio-Navigation) switches to follow the course set in "NAV1“. The AP will then try to intercept the radial set in the OBS and follow it according to the CDI. You should be on an course fitting for an interception (<60° deviation to the radial) - otherwise you cannot be sure if the interception ends up in the "TO" or "FROM" direction! In any case verify the course after the interception!

• APR (Approach) activates the ILS-Approach - i.e. the Glide-Slope will be activated too (if available).
• The newest version of the c172p does not require any more to wait till the GS-needle is horizontally prior to activating the GS!! 
• But older version (prior 2.0) will need it - for other models you have to find out yourself (or be careful and just do not activate the GL too early)
  

• REV (Reverse) switches to the reverse of the localizer radial. When you are on APR it will switch off the GL automatically!
  

• ALT (Altitude) activates the altitude control
• if the actual altitude is different to the wanted ALT we will climb or sink as defined by the UP/DN! Did you notice the problem? The UP/DN is winning! So if you are at 2000 and set the wanted ALT to 4000 ft -- it depends on the UP/DN whether you climb or descent. If in this case UP/DN is set "-500 ft" you will descent from 2000 ft down do crash, because you never cross the wanted altitude of 4000 ft!
• clicks on "UP" or "DN" switch into the "VS" mode and increases or decreases the rate of climb/descent - see the following UP/DN.
  
• click on the ALT switches the indicated function from "VS“ to "ALT" and back

• PT-Indication:
• There may appear a blinking, vertical written "<PT>" indication between the displayed "ALT" and "4000" in the above picture. That is a suggestion to you to trim into the indicated direction. (Remember: The big trim-wheel on the center-console? Use the keys 7/1 or mouse-wheel over the trim, etc.). There will be no direct problems if you do not trim - except: As soon as you switch off the AP the airplane is not trimmed at all - you might be in for a surprise!
  

• UP/DN (up/down) increase/decrease the rate of climb/descent (watch the negative sign in front of the number - that is often overlooked!)

As said before: These settings take precedence over the ALT setting - so there are some very remarkable actions possible

• actual (cursing) altitude	actual "preset" altitude	set UP/DN	Action
  3000	4000	(+) 500	we will climb to 4000 ft with a rate of 500 fpm
  3000	4000	-500	we will descent to crash with a rate of -500 fpm
  3000	2000	(+) 500	we will climb until crash with 500 fpm  (or land on the moon)
  3000	2000	-500	we will descent to 2000 ft with -500 fpm
  3000	3000	(+) 500 then -500	"jump" over an obstacle and then return to the set altitude

• ARM activates the dial below it to preselect the wanted (cruising) altitude. Use the mouse-wheel or push the left mouse-button to change by 10 ft each, or the center button (or wheel) for changes in 100 ft each.
  

• BARO activates the dial below it to define the barometric pressure.
• NOTICE: That "barometric pressure" for the AP is independent of the barometric pressure set (usually) by the knob at the altimeter!!!

1. A blinking display does not indicate an error - it is just the warning you that a new function has been selected and will be activated soon!
2. Especially when switching off the AP it may take some time before you get back full control. The active settings will be saved for that session!

DME

• With the switch in the center you switch the unit on/off

• The selector at the left switches between the two NAV-radios N1 and N2 (but be aware that not every VOR has a DME!)
• the center position "HLD" stands for “hold”, and means “retain the current frequency, regardless of whether NAV1 or NAV2 are getting re-tuned”. For example, if we switch from N2 to HLD, the DME will continue to display (and update) the DME-information of the last NAV-2 setting. Even if we re-tune NAV2, the DME will remain tuned to e.g. Manteca. This is handy, because it basically represents a third independent receiver, and on IFR-flights two receivers just never seem to be enough. (see the above ILS-example at EDDF!)
  

• In the display above "Miles" there is shown the distance to the selected VOR

• With the white button in the center you select to display on the right either
  
1. the "Speed above Ground" in KTS
2. or the "Minutes" until you will arrive at the VOR (in case speed and direction remain constant)

IAP: The"IFR-Approach-Procedure"

• for the USA e.g.:
• http://flightaware.com/resources/airport/KLVK   (just change the Airport-ID at the end)
• → "IFR-Diagrams“ = IFR Airport Procedures (/IAP)
• → "ILS Runway 25R“ (the only ILS equipped rw. at KLVK) – this one we need to use for our IFR approach!

• or http://www.airnav.com/airport/KLVK
• the approach-procedures are far down on that Internet-Page!
  

• for Germany e.g.:
• http://www.vacc-sag.org/?PAGE=airport_overview
• see e.g. for EDDF the "IAC VOR RWY 25R“ etc. ect. - EDDF has some more procedures than KLVK (yes: There are even more at KJFK, KATL, or...)
• but also see that tiny little Sylt (EDXW, e.g. "NDB/DME 14“) (in that same table): Also that one needs those approaches because of the vacation-guests coming by air! Of course you also need it to make sure that these stupid pilots do not always fly over the houses of the V.I.P.s.
  
• You might want to study this tiny IAP first, in order to get the general idea!

e.g.: KLVK ILS RWY 25R

These Approach-charts are not really standardized worldwide - but they all contain some common informations: (Sorry. usually those are not as nicely colored as seen here!) In the upper white part you see general informations like the name, frequencies, etc.  In the central pink part is the actual plan, as seen from above, especially for the headings to use In the lower yellow part you see the same from the side, for the altitudes to keep 2+3 together shall give you a 3D view of the IAP. I admit: That is not really easy to read and understand if you are not a graduated Architect or Mechanic - but try to use it more often and your problems will disappear (I hope!). There are usually a lot more informations at changing locations on the charts. e.g.: There may be "minimum values" for an approach, e.g. You may approach only if there is a minimum visibility, you have a minimum Radi-Equipment, etc. (See here in the green box) The "Missed Approach Procedure", i.e. what to do next if you cannot Touch-Down. (See here in the white box at the top)  Minimum Altitudes per direction you come from, e.g. when on one side are mountains, or buildings, or so.  Those restrictions are in a little circle, cut into directional pieces. (See  the circle at the right, inside the pink area) and an airport-layout. (See the white box at the left side). etc.

Analyzing the IAP:

1. In the center of the pink area you find the LOM/IAF REIGA: This is a NDB with 2 functions:

• As LOM it defines a unique point on the final-approach (we will see/use that later. It is located 6.1 nm out from the Touchdown Area of the runway at an altitude of 1039 ft). Did you find those values?
  
• "6.1 NM" in the yellow part at the bottom, 
• "1039" at the NDB symble in the center of the pink part! 

• As IAF it is the starting point for the IAP. Based on the NDB it is easy to find: Just set the frequency 374 into the ADF and follow the needle. Defining the minimum altitude to start is a little more complicated, because of the dual function of this point! As defined here that minimum altitude is 1039 (for the LOM) plus 2409 above that == 3448!
  

2. At the right center of that pink area you see the second IAF, that one is named TRACY. There is a "Procedure Turn" attached to that one - so in real life ATC might send us there to wait, when there is much arriving traffic. Finding this one is not that easy - but we learned how to do that in the chapter" Finding a FIX-point": Here we would find it for e.g. a "missed approach procedure"  (see in the white box at the top!) by two VOR-radials:
   
• 157° FROM VOR "SAC" (SACRAMENTO) on 115.20
  
• 229° FROM VOR "ECA" (MANTECA) on 116.0

• We are coming from the south so we will use the IAF nearest to us: The "IAF REIGA"

• On first sight that looks very easy from there: We just turn left and follow the localizer to the runway - BUT:
• we are not on the right altitude of 1039 ft as required at that point (the: LOM)
• and the IAP shows a big fat line to the right that ends in a line with a half-arrow pointing to the north-east (marked with 030° and 210°)!

That means we have to do a "Procedure Turn" to the right, away from the airport!




• So we follow the advise of the chart, ending in an ILS approach
  
• from the NDB REIGA we follow that fat line on a heading of 075° - away from the airport (above the other traffic on final approach!)
• before the outer 10 nm circle (see the mark in the yellow field, top right) we turn left to a heading of 030°
• we follow that 030° while slowly starting to descent to 3300 ft
• after 2 min we turn right to a heading of 210°

• Now we start a standard ILS-Approach    (if you forgot how-to: See above)
• we stay on 210° until intercepting the Localizer  I-LVK (heading 255°, frequency 110.5)
• then we follow that localizer while descending to 2800 ft
  
• and stay on 2800 ft until we intercept the Glideslope for our final descent

• Next we cross our old friend NDB REIGA on 1039 ft.
• REIGA is now not our IAF but welcomes us as "Outer Marker" (LOM) with a blinking blue light and a sound of 400 Hz
• and thus we know: We are  6.1 nm before "Touch Down"!

• But you also need to be prepared for a "MISSED APPROACH": If you look into the upper right corner of the IAP there is a box telling about a Missed Approach (Procedure), and in the lower green part you see the infos to it:
• i.e. for the "S-ILS 25R" you must initiate a "Missed Approach" if you do not see the runway at an altitude of 597 ft (200 ft above the runway)!
  

Parts of that procedure are shown in several places on the IAP: at the top, where it says “MISSED APPROACH” in the plan view, where you can see a dashed arrow coming off the end of the runway at the dashed oval on the right,  a pattern symbol at the right of the picture and a series of boxes at the bottom repeating graphically what to do. In our case, these all tell us to: 1. Climb straight ahead to 1100 feet 2. Make a climbing right turn to 3000 feet 3. Fly to REIGA (compare the frequency and Morse-code!) 4. Fly outbound from REIGA at 062◦ 5. Fly a holding pattern at the TRACY intersection The holding pattern, as you might have guessed, is a place where you can “park” while sorting things out, and has its own set of procedures and techniques which we won’t go into here, because . . . (but have a look into the chapter "Procedure-Turns" in the part "KnowHow".)

Map

	You (the yellow plane symbol in the lower right) just started at KRHV, now flying on runway-heading 310° towards the "airway  334", which follows the (cyan) Radial "SJC 009", which we have set before into our NAV-1, and which we will intercept soon. The next check will be the crossing of the radials "SJC 009" and "OAK 114" (which is set in NAV-2)  near the fix "SUNOL", which is not marked here by name, because the "Fixes" are not activated (see in the upper left corner!)! But because "Navaids" are activated you see » the VORs "OAK" and "SJC" in cyan, because they are active in your 2 NAV-radios » e.g. in the lower left quadrant you see another VOR "OSI" not in cyan and without Radial, because we do not use it.   "LV" (in the right upper corner) is the identifier for the NDB "REIGA", which is the IAF for our planned approach to KLVK.  Because "Traffic" is activated, you see the Multiplayers flying in your area. See e.g. "alex" to the left of you and "Godwin" on the dark blue ILS towards KSFO. You should also notice the pointers at those targets: » "alex" is flying in direction SW and is relatively fast » compared to "Godwin", who is relatively slow on Final to "KSFO runway 28"
	In this picture we changed already the NAV-2 from "OAK 114" to "ECA 229", and are on our way from Fix "SUNOL" to the NDB "REIGA". The two radials cross at fix "SUNOL" - this time its name is visible because "Fixes" is now activated. Also activated is "Data", thus we see additional descriptions to the major navigational aids. See e.g. » KLVK with the runways "07L/25R"  that are 5236 ft long. The magnetic headings are 91°/271° » REIGA with the identifier/morse-code "LV" and frequency 374 Khz See also the Fix's "FOOTO" to which we will turn over "REIGA" on heading 75°. And also notice that this segment of way is directly against the traffic on the ILS towards KLVK - so we better keep a safe altitude.
	In the above we headed for "REIGA". In the meantime » we turned to a hdg of 075° over "REIGA" towards "FOOTO" » which is defined by our course of 075° and the crossing radial "ECA 229" » there we turned to 030° » and after 2 Min. we turned 180° to a new heading of 210°, back towards the ILS-Localizer REIGA On this heading 210° we are now going to intersect the ILS 25R of KLVK. Did you notice that that ILS is now in color "cyan"? And the radial "SJC 009"  is not shown any more! Sure: We do not need the "SJC 009" any more and thus switched the NAV1 to the "ILS 25R"! Also notice that we are close to "TRACY" - the other "IAF" (Initial Approach Fix), and thus very close to the 10 nm radius, that we were not allowed to exceed!