How to read an approach chart..?

I made an detailed explanation of how to read an approach chart as requested by different people, please do not hesitate to ask any question after reading my post. All comments that are not related to this tutorial will be deleted.

As you can see, this is the ILS DME runway 27R approach for London Heathrow.

On the top there are a few frequencies, I will not talk about those as they are not important for IF. So lets start:


LOC IRR 110.3, This is the primary navaid for this approach.
LOC = Navaid type
IRR= Navaid Identifier
110.3 = Navaid frequency

Final Apch Crs 271 = Final approach course bearing.


GS D4.0 IRR 1410’ (1332’)
Approach ban: “An approach procedure, for which continuation is prohibited beyond a specific point, and or specified height, if the reported visibility or rvr is below the minimum specified for the approach.

So in this case the approach ban is at 4.0DME of the LOC IRR at an altitude of 1410 feet baro or 1332’ feet AGL.
CAT IIIB ILS NO DH, This box shows the lowest DA (height) or MDA (height) for the approach. In this case the lowest is “NO DH” and the approach is a cat IIIB which means an autoland.
CAT I, II & IIIA ILS refer to minimums, on the bottom of the chart we can find the minimums for the other approaches. That’s where we have to look incase we want to know them. I’ll explain this later.


Apt Elev 83’ Airport Elevation 83 feet
RWY 78’: Touchdown zone or threshold elevation: 78 feet.


MSA LON VOR: Minimum safe or sector altitude based on LON VOR. The normal coverage is 25NM radius from the facility or fix or airport reference point (ARP), in this case London VOR.

The sector defining radial / bearing, always depicted pointing TO the navaid or fix or ARP.


MISSED APCH: Here you can find the missed approach procedure written in text, later on we will see it also in a picture . This is also refered to as “the published missed approach procedure”

Climb straight ahead, when passing 1580 feet barometric altitude or 0.0 DME of the LOC IRR, whichever is later, make a right turn while climbing on track 318 degrees to 3000 feet. Then as directed.

Altimeter setting information:
Alt Set: hPa, this is the unit used for the altimeter setting. In this case Hectopascal. For the USA for example it will be in inches of Mercury
Rwy Evel: 3hPa, 1 hpa stand for 27 feet so 3 x 27 = 81 feet . As every hPa is 27 feet the few feet difference with the actual 78 feet is like non excisting as this is 3 feet or 1 meter.
Trans level by ATC: The transition level is decided by ATC
Trans alt: 6000’: The transition altitude is set as 6000 feet.

Quickly some more info to make this more understandable:
Transition Altitude: The altitude in the vicinity of an airport at or below which the vertical position of an aircraft is controlled by reference to altitudes (MSL)
Transition level: , Translation level is the lowest flight level available for use above the transition altitude. In IF this is standard FL180.
Transition layer: The airspace between the transition altitude and the transition level. Aircraft descending through the transition layer will use altimeter set to local station pressure, while departing aircraft climbing through the layer will be using standard altimeter setting. 1013.2 hPa or 29.92 inches of Mercury.

This is the plan of the approach with all kind of extra information like:

  • Obstacles
  • MSA
  • Holdings
  • Navigation aids
  • The routing.
    Here a picture from IF, you can see the same beam that brings you to runway 27R with the points IRR75 / IRR04 / IRR01. This are the exact same points as from the approach chart.

Let’s continue:

LOC (GS out) Here you can find the “non precision recommended altitude descent table”. This table is used as a reference to crosscheck your altitudes incase the glide slope part of the ILS approach is unserviceable. It uses IRR DME as a reference and it gives cross checks for 1 / 2 / 3 / 4 / 5 / 6 & 7 DME.

Here you can see the profile of the glide slope for the approach we want to fly. You can see on the left side the runway threshold as RWY 27R 78’ this means, runway 27 right 78 feet.

  • TCH 58’: Runway threshold crossing height associated to the charted glide slope or vertical descent angle. In other words, you should cross the runway threshold at an altitude of 58 feet on this approach.
  • Other important information are the altitudes crosschecks and distances. For example you can see the approach ban as well which is at D4.0 IRR or D5.3 LON at 1410 feet on the glide slope.
  • The small numbers 0.5 / 2.0 / 1.0 / 3.5 are DME distances between the different points.
  • 271: Final Approach Course bearing.
  • You can see a point D7.5 IRR / D8.8 LON @ 2500 feet. This is called the FAP or Final Approach Point. This is the beginning of the final approach segment for precision approaches. Here you should be capturing the glide slope. To make be on the glide slope at this point you should start your descent 0.2 nm before reaching this point.


Descent / timing conversion table:
In this table you can see the vertical speed that you require for a given groundspeed to follow the glide slope. For example at 140 knots groundspeed you will need 755 ft/min as vertical speed to follow the glide slope.
The 3.00 is very important, this shows that this ILS has a 3 degrees glide slope which means it is suitable for auto land.
MAP at D0.5IRR, Missed Approach Point at 0.5 DME of IRR. This we can disregard as this is for a non precision approach and the ILS is a precision approach.

This box shows the runway lighting:

  • HIALS-II, High Intensity Approach Lightning System number 2
  • PAPI, Precision Approach Path Indicator, on the left of the runway.

The following boxes are a reminder of the first steps of the go around procedure which we already saw in the beginning.
Straight ahead to 1580 feet or D0.0 of IRR whichever is alter, then a right turn on track 318 degrees

Remember in the beginning we saw the text CAT I / II & IIIA refer to minimums. Are you ready??

Standard: This is an indication that the published landing minimums are compliant with EU OPS. For US OPS it will say TEPRS instead.

Now it will get a bit more difficult, there is a lot of information in this small table

CAT IIIB / IIIA / II / I are all different approaches where the pilots can choose from depending on the visibility and ceiling at the destination.
C / D is the category of your airplane depending on the landing speed. For an idea of different airplanes and their categories check my explanation:

RVR: The minimum required Runway Visual range for different approaches.
DH: Decision Height based on radio altimeter.
DA: Decision altitude based on barometric altitude.
FULL / Limited / ALS out are differences in the approach and runway lights available, it has no use to explain this all when you want to play IF.

RVR is normally measured in 3 different points for a certain runway,
Mid point
All these points need to reach the minimum value of the approach you want to do to be allowed to fly it. So for a CATII approach you will need minimum 300 meters for all 3, in the metar it will show as: “R27R 300/350/500” for example, this means the Touchdown RVR is 300 meter, midpoint 350 meter and rollout 500 meter.
There are more rules when which rvr measuring point you need but I will not go deep into this

All numbers are based on Decisions so you have to make a decision at this point. This means you should have the runway / runway approach lights insight at this time and you have received a landing clearance. If one or both are not the case you will need to go around at your DH.

LOC (GS out)
This minimums you have to follow when the glide slope is unserviceable and you have to add 50 feet to this because at this point it is a MDA, Minimum Descent Altitude so you are not allowed to bust this altitude. If you make initiate the go around at +50 feet it will assure you that you will not bust the 430 feet.

Circle-To-Land: This is a complex procedure and I will not talk about it.

Extra info:

‘ , this behinds a number means feet. So 78’ = 78 feet.
DME: Distance measuring equipment, you can compare this with kilometres / miles or any unit you want but it is measures in Nautical Miles. NM.
1 NM = 1.852 KM
1 NM = 1.15 Mile
1NM = 6076 feet.

CAT II : A precision instrument approach and landing using the ILS with;
A DH below 200 feet but not lower then 100 feet
A RVR of not less than 300 meters.
CAT IIIA: A precision instrument approach and landing using the ILS with;
A DH lower then 100 feet and
A RVR not less then 200 meters.
CAT IIIB: A precision instrument approach and landing using the ILS with;
A DH lower then 100 feet or no decision height.
A RVR lower then 200 meters but not less then 75 meters.

These are the basics on reading your approach chart, this should be more then enough to start on IF. If you are looking for any approach charts just use google as most of the charts are available on the internet.


Wow, great tutorial! Helped a lot! :)


Awesome, have been waiting for something like this!


Nice one Aernaut!


Ya did it again! Another “Home Run/Goal”! “BZ” Well Done. Max


Are you going to start charging ground school fee’s :) great work


Thank you @Aernout appreciate it. It’s great

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This is truly amazing…really good stuff…much appreciated…thanks much Aernout @Aernout


Awesome thanks

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Great information and deserves to be on top again


Indeed. I keep coming back to this tutorial, really good info.

Hi Aernout,

Firstly, thanks so much for such a great description.

I do have 1 more question though. I completely agree with your explanation but I am having trouble convincing my colleagues.

Regarding the CAT II/III RVR depicted on the chart, does that apply for all 3 zones. i.e. CAT IIIA RVR 200m. There is only the 1 value on the chart, and yet some operators are authorised for RVR 75m for MID and END if they are reported and relevant. So If ATC reports the RVRs as 200/100/100 can you shoot the approach?

I have searched everywhere but cannot find in any EU OPS or Jeppessen doc where it says that the RVR value on the chart is only for the TDZ or for all 3 zones.

Any assistance you could give or a reference would be really helpful.

Many thanks,


Hi @al_wins

This all depends on the approach you are flying.

  • CAT 3A
  • CAT 3B with DH
  • CAT3B no DH.

But the RVR may NEVER be below the charted one, if any RVR is reported and below the charted you can’t land.


Ok, @Aernout, here are my questions (These are in chronological order):

  1. What does 4.0 DME mean?
  2. What is a VOR?
  3. What is the purpose of a transition altitude, and what is it?
  4. What does MSA mean?
  5. What does IRR DME mean?
  6. What does CAT IIIB, CAT IIIA, CAT II, and CAT I mean?

I know I’m not Aernout but I will still try to answer:

  1. Probably a Distance Measuring Equipment (DME) which measures up to 4.0nm. A DME can be used to estimate the distance between the aircraft and the aerodrome if the DME is on-site.

  2. A VOR, also known as a Very High Frequency (VHF) Omnidirectional Range (VOR) is something that aircraft use to land if the ILS is absent.

  3. A transition altitude, according to FAA and IF context, is a layer of altitude where aircraft passing through the active airspace may do so without conflicting with the traffic which are already in the airspace. Otherwise, as what I know, a Transition Altitude is present so the pilot can set the altimeter from the ground pressure to the standard pressure of 1013.25millibars (QNH1012/QNH1013) or 29.92 inches (A2992).

  4. MSA stands for Minimum Sector Altitude which provides a set clearance for aircraft to avoid colliding with anything below the stipulated MSA.

  5. IRR is simply the name of the navaid, DME wise, you know :)

  6. These CATs are categories and Roman numerals are used here so CAT III means CAT 3 and CAT I means CAT 1

Usually CAT I is the clearest of weather and CAT III well not so


Good stuff thanks!

Lol don’t tell me I’ve answered everything correctly that you’re not going to answer 😂

Good enough for the basics, no need to get too deep in it.

Here cat II / III numbers in detail :)


Thank you! Thanks man! Thank you very very much! you’ve just lessened my research… You’ve made it easier…i never thought RW stuff would be available here for tutorials.Great job!You definitely need a handshake

Do you have to use and follow a chart when flying vfr?