Please bear in mind that I am neither a CFI (FI) nor a CFII (IRI) and that what I describe hereby is what I've learned myself all along my flight simulation years of experience by consulting literature or knowledgeable people. A very good source for IFR content and emergency procedures is Code7700 website. I really encourage people who wish to learn in depth IFR procedures, to visit this website.
For the seek of clarity in my explanation, we will use as example the approach plate of Martin State KMTN and more specifically the VOR/DME RWY15 approach.
There are plenty of sources available on internet (or using an aviation app like Avare that I presented in one of my articles on this blog) to find the approach plate that you will need for the approach intended to be flown. For the USA, one of them is Skyvector website. In addition to the VFR, low/high IFR navigation charts, various plates can be found including airport diagram, SID/STAR charts and obviously the IFR approach plates which are most of the time up to date. By the way, this should be your first reflex:
Check the validity period of the plate to ensure you will be using the most current one! This validity period is found on the left hand side of the chart, outside the border line.
Most of the time, one just needs to read because this is crystal clear and self explanatory. However, some specific indications require clarifications.
Let's start by reading the top of the plate (I will assume that you already know what a VOR & DME equipments are):
"VOR/DME" or TACAN Z RWY 15" obviously means that the approach plate describes a VOR/DME or a TACAN Z approach for the runway 15 at Martin State (MTN <-- FAA location identifier of the airport).
TACAN stands for TACtical Air Navigation which is basically a military navigation system. It is a combination of a VOR and a DME which uses the UHF radio frequencies range.
You will often find a letter with something like VOR A or ILS Y RWY31L for instance. If there is a letter that means that for the approach, a minimum of one of the conditions below exists:
1. There is an offset from the final course equal or above 30°
2. The final approach course is different from the beginning of the runway
3. The approach requires a descent gradient of at least 400ft/Nautical Miles (NM)
In case multiple approaches exist for a given runway using a VOR or a NDB, then the approaches will be identified with a specific letter: VOR A RWY 31L; VOR B RWY 31L; VOR C RWY 31L...etc. Note that these approaches will be identified with a letter starting from A going upwards in the alphabet.
It is the same principle for the ILS, TACAN approaches except that the identification will start from the letter Z going downwards in the alphabet.
At the top left hand side, one can find the frequency of the VOR of Baltimore (BAL) used for this approach 115.1 mHz or channel 98 in case a TACAN system is used (that is also the channel used by the DME).
Next to this information, it is stated that this procedure uses an ARC approach with a radius of 14.7 NM (the ARC flight path will be located 14.7 NM away from the VOR of Baltimore).
Progressing to the right, one finds the runway length in feet "Rwy ldg"; the Touch Down Zone Elevation "TDZE" in feet which is self explanatory and finally the Airport Elevation (Apt Elev) in feet: this is the elevation of the airport above Mean Sea Level (MSL).
On the line below and left hand side, a negative T (white T on black background) is depicted and indicates that non-standard Take-off minimums are applied. In this case, one should look at the "TAKE-OFF MINIMUMS" chart to check the specific minimum weather conditions allowing to take-off (not for Part 91).
Standard Take-off miniums for commercial part 121/135 are 1 Statute Mile (SM) visibility for single/twin engines or 1 and a half SM for 3/4 engines and with a minimum climb gradient of 200ft/NM unless otherwise specified by an Obstacle Departure Procedure (ODP).
The negative A indicates similarly non-standard alternate requirements are in use.
In this case, the minimums one needs to check are listed at the bottom of the plate but we will have a look later.
The standard alternate requirements follow the 1-2-3 rules:
The flight plan does not need an alternate field if the weather 1 hour before and after the Estimated Time of Arrival (ETA) has a ceiling of 2,000 ft AGL (Above Ground Level) or higher and a visibility above 3 SM.
If the minimum weather conditions listed above are not reached, then the flight plan does require an alternate field. Is considered as a valid alternate field, an airport that has a minimum of 2 SM visibility and 600 feet AGL ceiling for a precision approach or 2 SM visibility and 800 feet AGL ceiling for a non-precision approach.
Some quite obvious written remarks are found to the right of the negative T and A. It states that in case the local altimeter setting is not available, the altimeter setting in use at Baltimore.Washington International must be utilized and so safety margin are applied by raising all the Minimum Descent Altitude (MDA) by 60 feet and the minimum visibility is raised depending on the category of airplanes and if one flies a straight in approach for runway 15 (S-15) or a circling approach.
CAT corresponds to airplanes that have a Vref (approach speed) at maximum allowed landing weight or if not specified, have an approach speed equal to VS0 times 1.3 that corresponds to:
CAT A: 90 knots (KTS) or less
CAT B: Between 91 KTS and 120 KTS
CAT C: Between 121 KTS and 140 KTS
CAT D: Between 141 KTS and 165 KTS
CAT E: 166 KTS or more
Remarks:
It is quite easy to mismatch acronyms. One has to differentiate DH/DA from MDH/MDA.
For precision approaches (ILS, MLS GLS, TLS to name a few), one uses Decision Height (ft AGL) or Decision Altitude (ft MSL) at which the missed approach procedure must be initiated in case the runway or runway environment (e.g. lighting system) is not visible.
For non precision approaches (VOR, VOR DME, NDB, LDA to name a few), one uses the Minimum Descent Height (ft AGL) or Minimum Descent Altitude (ft MSL) which is the lowest altitude that one needs to stay at until the Missed Approach Point (MAP). When reaching the MAP, if the runway or runway environment is not visible, the missed approach procedure must be initiated.
The missed approach section is quite obvious too and describes in details the missed approach flight path.
On the line below, all the ATC frequencies useful for the approach are indicated. Frequencies such as the ATIS, approach controller, tower and ground and UNICOM can be found.
At the bottom of the plate, important information regarding the flight path are shown. Since it is an ARC approach, the various waypoints are defined using radials from the VOR of Baltimore (e.g. SLOAF is on the Radial 334° from BAL VOR).
For each waypoint the minimum altitude is indicated (it is a minimum because it is an underlined number). In case of a maximum altitude, one would have found a superscript number). So when flying between SLOAF and CUMBE, one should remain at or above 2,600 ft MSL. Between CUMBE and GOVES, one should start a descent so that the altitude will not be lower than 1,800 ft MSL when overflying GOVES...etc.
"Procedure Turn NA" means that procedure turn to start the ARC is not authorized.
"14.7" is the DME indication (distance) from the VOR of Baltimore to execute the ARC approach.
A depiction of the missed approach procedure is also added in this part as a reminder. The arrow turning right indicates that at the MAP, we need to start a right turn climbing to 2,500 ft MSL to join the radial 068° from the VOR of Baltimore. Then when established on the R-068 of BAL VOR, we start an ARC at 11 NM from BAL VOR turning clockwise ("CW" on the chart) until the waypoint BOAST.
The minimums can be found below the flight path according to the category of the plane.
The fields found on the "S-15" line are the minimums for a straight in approach for runway 15.
The fields found on the "Circling" line are the minimums in case a circling approach is flown.
The first number is always the ceiling in altitude (MSL) while the second number indicates the minimum visibility required (be carreful, it is always in statute miles so you will have to convert the visibility given in the ATIS information from NM to SM!).
So for a straight in approach runway 15 with a category A plane, the minimums are a ceiling of 920 ft MSL and a visibility of 1.25 SM (1.09 nm).
The numbers with a slightly lower size are indicated in altitude AGL.
The numbers in brackets are the minimums for military use only.
In the middle section of the IFR approach plate, a depiction of the flight path as seen from above is shown.
Nothing new in comparison with what have been described so far, ex
R-4001A or R-4001B which are the Restricted area in which we should not fly if active (or "hot"). Some restricted area are activated on typical schedules, others are activated via NOTAM (NOtice To AirMen).
A text along a circle with a reference in the middle: in our case one recognizes a VOR symbol. The text mentions "MSA BAL 25 NM" which means that the VOR of Baltimore is taken as a reference point for the Minimum Sector Altitude (MSA) up to 25 NM away from the VOR. The framed number within the circle 2,600 is the MSA of 2,600 ft MSL below which one should not go when flying within 25 NM from the VOR of Baltimore for safety reason (i.e. obstacles)
Triangles with a point drawn in between are the location and elevation (in ft MSL) of the highest obstacle points.
IAF stands for Initial Approach Fix which is the point which the approach procedure should be initiated from.
The description above corresponds to what is most of the time typically found on an IFR approach plate. Sometimes there are some specific indications, but again googling or looking for YouTube videos will be helpful to understand them.
I flew this approach in X-Plane 11 during Instrument Meteorological Conditions (IMC) and the complete approach flight can be found here:
My recommandation is that in order for you to remain current and proficient as much as possible:
Whenever you find something you don't know about on an IFR approach plate or more generally on a chart, make the effort to look at what it corresponds to. This way, you will continue to learn and you will gain a valuable aviation knowledge.
PS: If you spot an error or something I misinterpreted, please reach me out so that I can correct the article.
TIPAH