VOR/DME approaches better than ILS

[SierraHotel2873]

The second one looks like the RNAV Transition to RWY25L. It is setup to give ATC “space” for separation. With this transition you will always recieves vectors to the ILS (IF SOTIL), as the “outbound” leg (HDG65deg) goes to infinity and you would run out of fuel if no ATC would give you vectors :-). Mainly used for IFR, Airliner arrivals.

Most likely and this is just an assumption. You would arrive via CLE, heading towards BLE443, if you are important enough (maybe the King of Spain or so ;-)) and the airspace is not busy they would give you vectors from or before BL443 to SOTIL, which ends up looking as your first routing picture.

And yes you would choose a STAR to connect you to the IAF (in this case CLE) e.g. ALBER1W.

(Edit: you need to look at the maps to get this info. The MS FP wont help and creates a “shortcut” to SOTIL, which does not exists in the original).

[Habu2u2]

IRL, the biggest factors for commercial airlines are company policy, and the biggest real-life factor for everyone from PP to ATR is the weather and currency. VOR/DME, or localizer approaches are non-precision approaches, meaning they don’t have glide slope information. Those approaches normally entail several step-down altitudes as you get closer. You fly the final altitude in level flight until you see the runway or hit the missed approach point and go around or go away! This Minimum Descent Altitude is virtually always higher than the Decision Height for ILS approaches, which give you a (normally) constant descent angle that gets you to a (normally) lower altitude DH. That allows you to fly into lower weather ceilings and visibility than a VOR/localizer type approach. Look at @marccreal’s charts. The VOR MDA is 530’, whereas the DH for the ILS is 208’. (by the way, U.S. terminology, here for simplicity, but the concepts are the same, just minor terminology differences for the most part).
In the sim, fly it like you want, since there’s no FAA looking over your shoulder!! But if you’re going to simulate bad weather and low ceilings/visibility, then you might want to use the appropriate approach for the conditions.
Other than the full-on Cat III landings, all landings end with a visual approach. Some just have lower start points than others!
Regards

[DanDaredum]

One of these days I’ll learn the approach plates and all that IRL stuff. Guess I’m lazy haha. I’m just a hobbyist.

[TheBigBeefcake]

That’s added a lot to me personally as far as flight simming goes. There’s lots of great YouTube videos out there to explain how charts are used. There’s plenty of free sites too (SkyVector is a great one if you are flying primarily in the US).

[CaptainRude91]

@wazitdoinnow

Airliners tend to get routing via SIDs which leads to a FAF (Final Approach Fix) at a determined height and, critically, speed to allow landings every 3 minutes.

Try Standard Instrument Arrival (STAR), SID stands for Standard Instrument Departure (SID) which leads to the en-route segment, not to a FAF .

@wazitdoinnow

VOR/ DME Approaches tend to be used by smaller aircraft already at a lower height and able to “nip” in between.

Hardly ever happens, most commonly aircraft get cleared to intercept the ILS from a lower altitude than published (often called “short approach”) or fly a visual approach if possible, I have never been cleared for a non-precision approach where a precision approach is available just to cut short. Non-precision approaches are not shorter anyway! Since there is no glide-slope most airlines fly non-precision approaches completely configured from the FAF, which means flying the whole approach at lower speed, so no “nip” in between.

[CaptainRude91]

@Habu2u2

Those approaches normally entail several step-down altitudes as you get closer. You fly the final altitude in level flight until you see the runway or hit the missed approach point and go around or go away!

This is 10 year old info, almost all non-precision approaches are flown as CDFA (Continuous Descent Final Approach) nowadays using the MDA + margin as DA. The charts posted by someone is this thread are over 10 years old, before / during the introduction of CDFA, RNP / RNAV has become more dominant etc.

@Habu2u2

That allows you to fly into lower weather ceilings and visibility than a VOR/localizer type approach.

Just to clarify, the lower minima is not because the ILS is flown using a constant descent angle, as explained above, almost all non-precision approaches in Europe are flown as CDFA. The lower ILS minima is due to higher precision.

Although the vertical profiles got revised to be CDFA the minima are still MDAs rather than DAs. Be aware that Jeppesen copies the MDA and calls them DA on non-precision approaches! Navblue does the same but at least they don’t call it a DA. You need to add a correction depending on aircraft type for altitude-loss during go-around as not to descent below MDA. FAA might be different but in Europe the state only publishes MDA for such approaches and chart manufacturers directly copy those.

[CaptainRude91]

Those are really old charts! Over 10 years old (revision 2008) a lot has changed since, introduction of CDFA non-precision approaches, PBN, RNP approaches etc. RNAV has become more important, conventional arrivals have largely disappeared etc.

These are the most recent ones, you can see the vertical profile has been completely revised. The minima remained the same, which really is a MDA still instead of a DA, so you have to add a correction to these minima to use them as a DA.

[marccreal]

Thanks a lot for all the explanations! I just took the first chats I could find as I only wanted to add some illustration to the original question.

In the new chats, there is interestingly no mention of neither the term MDA nor DA. So they let this to the interpretation of the user?

One question about CDFA: what is the reasoning behind this change from stepwise? Do they suppose that aircraft/pilots nowadays are better capable of correctly fly the continuous decent?

[CaptainRude91]

I don’t know exactly from which direction you were approaching so I just took a random arrival. The first thing to understand is that the arrival / approach to an airport is split into segments:

1. Arrival
2. Initial Approach
3. Intermediate Approach
4. Final Approach
5. Missed Approach (which itself is split into the same phases above minus arrival)

Each of those phases serve a purpose in maneuvering, slowing down and configuring the aircraft for approach.

Arrival

The Arrival segment starts from where the en-route segment (airway) is left and ends at the Initial Approach Fix (IAF). This segment is used to slow down the aircraft and descent for approach, it often ends in a holding pattern over the IAF.

Initial

The initial approach starts at the IAF and ends at the Intermediate Fix (IF) the IF is located on the extended centerline (point of localizer intercept) usually a few miles (minimum 2 nm) prior glideslope intercept or start of descent on non-precision approach.

Intermediate

Intermediate approach is the usually straight segment between the IF and the FAP - Final Approach Point (Precision or APV approach) or FAF - Final Approach Fix (non-precision approach).

Final

The final approach starts at the FAF or FAP and ends at the Missed Approach Point (MAPt). The MAPt is usually the point where the glidepath intercepts the Decision Altitude. The approach is then either continued to a landing if sufficient visual references are attained or a missed-approach is executed if not.

---

Where can you find each of those phases?

En-route Segment

If you open Skyvector you can see the point PUMAL I’m using in the example below, is the point where you leave the en-route (airway) system. This is where the Standard Instrument Arrival (STAR) starts.

Arrival Chart

The Arrival segment, commonly referred to as Standard Instrument Arrival (STAR) can be found on the arrival chart, I’ve included an example below:

Transition

The initial approach can be on a separate chart called a “Transition”. The “transition” refers to the transition from the IAF and the IF. On some approaches and on smaller airports there isn’t a transition and the initial approach segment is depicted on the instrument approach chart.

Below you can see a transition to the ILS 25R via the North. It looks like a snake, usually you’ll receive vectors or receive shortcuts from one end to the other, you rarely fly the whole transition. For example if its really quiet you can expect to fly from CLE direct TEBLA, shortcutting the whole transition (from IAF direct to IF) or receive similar vectors.

Approach Chart

Intermediate, final and missed approach are depicted on the instrument approach chart and in some cases the initial approach as well as discussed above:

If you now compare this chart with the VOR approach you will notice that the ILS approach chart starts at the IF, so the intermediate, final and missed approach are on the approach plate. The VOR approach plate starts at the IAF so in addition to the intermediate, final and missed approach segments the Initial approach is also depicted (no complex transition on a separate chart).

I think FS2020 automatically selects the whole transition which makes the arrival look like a long snake, if you can post a screenshot we can figure out for sure what is going on, but that is my guess.

[CaptainRude91]

@marccreal

In the new chats, there is interestingly no mention of neither the term MDA nor DA. So they let this to the interpretation of the user?

Navblue is never mentioning if its a DA, DH or MDA, I guess to prevent confusion, its often up the operator anyway to specify their own minima. For the turboprop we use MDA +30ft for example, for jets we use +50 ft in the company I work for. I’m pretty sure Navblue can modify the charts for a specific operator needs, probably at a price. Jeppesen makes a complete mess out of things by taking those old MDAs and actually call them DAs, it has caused (and still causes) so much confusion. All the DAs Jeppesen publishes on non-precision approaches are MDAs!

@marccreal

One question about CDFA: what is the reasoning behind this change from stepwise? Do they suppose that aircraft/pilots nowadays are better capable of correctly fly the continuous decent?

Its just a very outdated technique to descent using stepdowns and level-off at an MDA to a MAPt on non-precision approaches. It just doesn’t fit in with modern day stabilized approach concepts etc. Nobody flew those approaches as non-CDFA anymore anyways. You are not gonna level-off your fully loaded Boeing 747 at 530 ft MDA and fly level to the MAPt, then cut the thrust when runway insight and dive for the runway, you could maybe do that in a Cessna, not with an airliner.

To make things worse, there is no guarantee that the aircraft is still in a safe position to continue for a landing upon arriving at the MAPt, in some cases the MAPt is even BEHIND the runway! So most airlines were already flying non-precision approaches as CDFA by just drawing a 3 degree glidepath from the threshold up, making sure it is at least above all those stepdown fixes (if not, fly the approach steeper than 3 degrees), add a few feet to the MDA and instead of levelling off, use it as a DA. Basically what we are doing now.

Non-CDFA approaches still exist, there are airports with only one beacon and no DME, in those cases there isn’t really another way of creating an instrument approach, you could do something with groundspeed and timing, you also see that for some approaches for example at 30s after FAF altitude should be X feet etc. Otherwise its still the old non-CDFA technique.

I had some examples of those, the old non-CDFA technique and timing, but it seems both airports have since removed those procedures and now have RNP approaches instead…

Edit: just came accross this article:

How To Fly A Continuous Descent On Final Approach (CDFA)

[CaptainRude91]

Found one of those approaches which use timing, this approach aims to fly a constant profile by checking the time from passing the FAF with groundspeed to get the correct altitude. On this approach also the MAPt is being defined as a time after passing the FAF. So when reaching minima or the MAPt (time) whichever occurs first a go-around is initiated.

It seems to be quite difficult to find a non-CDFA approach nowadays, so I took an old Jeppesen plate I still had on my computer somewhere. This approach is constructed using only a single (NDB) beacon, you can see the missed-approach point is BEHIND the runway even! Not authorized for performance category C and D for obvious reasons .

@marccreal, sorry seems I’ve been responding to myself .

[SierraHotel2873]

Wow Nijntje. You really put some work in these posts. I would encourage the moderators to pin this permanently as reference/ tutorial.

Thanks.

[wazitdoinnow]

Quite right Nijntje,

Got my SID and my STAR mixed up.

Excellent write up. Thanks.

[jfoguet61]

Very interesting thread, thanks for all explanations and insights…
If I may just add (slighlty off-topic), in El Prat (LEBL), RWY 25L/07R is usually used only for day-time take off, while RWY25R/07L (longer) handles the normal landings (the exception being the large intercontinental airliners, such as the 380, which also use the longer 25R/07L for taking off).
Landing in 25L/07R would be very uncommon, at least with the high traffic pre-COVID.
Being Barcelona my hometown, I used to fly very often from El Prat (as passenger, pre-COVID times), and I always loved the landing in 25R, where you see the city to the right.
I recreated this landing in MSFS with the following short video:

Microsoft Flight Simulator - Barcelona El Prat (LEBL) RWY25R Landing (4K)

[DanDaredum]

Yes, this was a very interesting read.

[DanDaredum]

Been to Barcelona many times. One of my favorite cities in the world.

[jfoguet61]

@timinorlando yeah, Barcelona is great. And, in MSFS, it has one of the best photogrammetries available. So it is worth taking a small aircraft and exploring the city from the air…