Menu Sign In Contact FAQ
Banner
Welcome to our forums

IFR Route Planning Questions

Hi,

I’ve had two questions recently that I wasn’t certain about the answer on. Maybe an experienced IFR pilot can help answer?

1. When planning/flying a route – does the IFR pilot need to plan around danger areas or do you aim for the most efficient route and let ATC keep you safe? How about danger areas in CAS vs OCAS? What are the chances of being cleared through a live danger area?

2. How strictly do ATC expect you to follow the vertical profile of planned routes? What if in the middle of a route the only logical waypoint combination is at FL150 but you don’t want to fly higher than FL100? Does it mean you file a totally illogical segment to get around it or just put in FL150 knowing you can’t climb?

If anyone has general tips from experience on routing planning ‘reality’ vs ‘planned’ I’d welcome that too!

DMEarc

1. Yes, the CAS vs. OCAS distinction is important. In CAS, you don’t have to worry too much about it, as ATC will have the chore of keeping you outside of any active military areas or at least to coordinate with them. When OCAS, you have to do the same planning as if you were VFR.

That said, you probably know that ICAO does not forbid flight through an active danger area. It’s only in the UK where they do their own thing and make (many) active danger areas become de-facto prohibited areas.

2. In Europe, ATC knows that a lot of today’s flightplanning is fiction and that pilots are often constrained by some stupid airway restriction and such. So yes, they will not expect you to fly that profile. They are not even interested in the flightplanned altitude. When you arrive in their sector, in level flight, and you don’t speak up, they assume you are happy with your present altitude and leave it at that.

The exception obviously comes when the MEA or MORA becomes a factor. Also, there are cases like Frankfurt or Brussels, where there are fixed minimum overflight altitudes.

Last Edited by boscomantico at 23 Mar 21:46
Mainz (EDFZ) & Egelsbach (EDFE), Germany

Bosco, that’s very helpful, thank you. So to clarify.
1) OCAS fly as if you were VFR (i.e. manager your own crossing clearance) with regards to danger areas, except what if ‘cleared as filed’ at your departure airport?
2) It’s okay to plan routes you’ll never fly vertically as well as horizontally. The Eurocontrol restrictions of not crossing ‘POINT1 to POINT2 below FL145’ doesn’t matter. It’s not a matter of ATC saying – ‘Sir, you better get upto FL150 as per your plan if you want to fly there’, assuming MEA/MOCA ok.

Last Edited by DMEarc at 23 Mar 21:55

It has to be said that there is far more latitude vertically than horizontally.

Horizontally, ATC give you a lot of leeway but often they are really strict. On recent flights I have done I has never-ending “active miltary” areas. It seems that France especially is preparing for WW3. Maybe they are, in light of recent events?

Vertically, once you are above whatever the minimum for the CAS base is, you could probably go to FL600 if your plane could…

As Bosco said, IFR OCAS is for all practical purposes as VFR i.e. you are on your own. You might be getting a radar service but they aren’t likely to help you avoid some prohibited airspace. I busted a French nuclear power station area under a radar service and while they asked for the name of the pilot afterwards (obviously a very unusual thing to ask) they could not care less about telling me I was heading for it. There are some anecdotal differences e.g. in the UK if you are IFR in Class G you are going to be taken more seriously than if you were VFR in Class G, but ATC will normally deny this is the case, and anyway it could just be that the IFR pilot normally does a better job of the radio… which also helps with ATC but they also tend to deny that is the case

Administrator
Shoreham EGKA, United Kingdom

So therefore, OCAS, assuming from your departure airport you’re ‘cleared as filed’, can you take a scenic detour from POINT1 to POINT2 if there is a danger area in between? Or do you need to inform ATC of the deviation? Uncontrolled IFR seems confusing!

On a recent flight, ATC kept asking my next waypoints, does the flight plan got dropped after leaving CAS and sometimes not get picked up again on re-entry to CAS?

Last Edited by DMEarc at 23 Mar 22:30

What country was this?

In the UK, there is no such thing (practically) as IFR OCAS. It is just a VFR flight on which nobody cares what you are doing – because IFR non-radio is legal.

If ATC is asking your next WP, you must be OCAS and they don’t have a flight plan for you (London Info, Farnborough, etc). Essentially you are speaking to the wrong sort of ATC, but there is no choice anyway. If you were on a proper Eurocontrol IFR flight (almost totally in CAS) they would not be asking you anything like that because they have you in their computer, end to end.

A flight plan for a non Eurocontrol IFR flight goes basically nowhere. It’s a waste of time filing one (except for S&R purposes).

I would suggest a quick read of this

So therefore, OCAS, assuming from your departure airport you’re ‘cleared as filed’,

That is another meaningless traditional phrase. You could depart say Biarritz (Class D) and be “cleared to EGKA” but they have no idea EGKA is in Class G, and any IFR clearance will de facto end when London Control (or the French, if you are too low leaving France) drop you. The saying “cleared to XXXX” is just a tradition, because a 747 going JFK-LGW will be in CAS all the time.

Administrator
Shoreham EGKA, United Kingdom

2. How strictly do ATC expect you to follow the vertical profile of planned routes? What if in the middle of a route the only logical waypoint combination is at FL150 but you don’t want to fly higher than FL100? Does it mean you file a totally illogical segment to get around it or just put in FL150 knowing you can’t climb?

If you file a route you should be able and willing to fly it. But in many cases, you can ask ATC for a lower level on the day if terrain permits.

2) It’s okay to plan routes you’ll never fly vertically as well as horizontally.

Basically yes; you can file something that you do not expect to fly. But you should not file for something that you are not capable or willing to fly.

In order to get your flight plan accepted you do need to comply with all kinds of restrictions. And it is not just a matter of complying with MEAs and airport connecting points. There are all kinds of restrictions on airways that are listed in RAD.

Fortunately, thanks to technology, you do no longer need to sweat over these restrictions because the flight planning tools figure them out for you. The same flight planning tools are able to suggest DCTs in order to circumvent other restrictions that would otherwise force you to make big detours, even if you would not end up actually flying these detours because ATC would give you a DCT anyway (unless you end up NORDO). But even when applying such techniques you will end up with cutting some corners thanks to ATC – depending on the country.

Imagining I want to fly back from S-W France to LFPT. I might file something like POI J55 LGL Z295 PEXIR. The MEA for J55 is FL070. The MEA for Z295 is F120 so if I choose to file Z295, that is the altitude I need to file at least for the second segment. But I cannot climb to F120 because of density altitude. Although I know that ATC would allow me to remain at F080, I would not file it unless I was able to fly it. So I have two choices; LGL R111 CAN J116 PEXIR which is 62 NM longer, or LGL H20 EVRUK DCT PEXIR which is just slightly longer than Z295. So I would file the latter and actually expect to get LGL DCT PEXIR from ATC (or I would ask for it).

As bookworm also pointed out, the route you file/plan should not be too unreasonable though, especially because in case of NORDO you might end up having to fly it. And you certainly need to carry the fuel that would allow you to fly the filed route.

At the altitudes we fly there is no other traffic, except around the major airports. Therefore ATC can accept pretty much any altitude you ask for. If you fly low they may need to vector you around some regional airport where there happens to be an IFR departure at the time.

The Eurocontrol restrictions of not crossing ‘POINT1 to POINT2 below FL145’ doesn’t matter. It’s not a matter of ATC saying – ‘Sir, you better get up to FL150 as per your plan if you want to fly there’, assuming MEA/MOCA ok.

Around some of the major airports they may want you high in order not to interfere with SID/STAR traffic to/from the airport, so you will have a lot less latitude to choose your altitude. Apart from that, at least in France, you are likely to get whatever altitude you request.

Vertically, once you are above whatever the minimum for the CAS base is, you could probably go to FL600 if your plane could…

I think that between F280 and F420 it would probably be complicated because it is crowded and at our air speeds we would have a problem “fitting in” It is also RVSM…

Last Edited by Aviathor at 24 Mar 08:00
LFPT, LFPN

I find it is still quite a black box… and some of the RAD are probably stupid and should be just removed.

The other day for an IFR training flight i was supposed to do ELLX – LFJL and return. These are very close and it is known and documented that ELLX will vector you. LFJL is a rather quiet airport.
But still the CFMU will not accept anything without a STAR so the routing end up being totally stupid. My instructor confirmed that I will probably get a DCT MTZ quite quickly after takeoff, and that is also prohibited by the CFMU (LFEE max DCT is 0 NM). So i don’t really see the point of these…

ELLX (Luxembourg), Luxembourg

This damned business is never the same twice.

If you want to fly a route where you know a certain ATC concession is normal and you have checked enroute notams (for military or whatever activity) then you can file a series of waypoints in a manner which bypasses Eurocontrol validation except for the MAX DCT parameter in that airspace which is always checked – example

Shoreham EGKA to Le Touquet LFAT is filed EGKA SFD LYD LFAT and is flown an EGKA-SFD to enter CAS to FL070/080 and then usually DCT LFAT with a handover to Lille.

LFAT-EGKA is flown with the LYD SID which is basically a LFAT DCT LYD FL080 and then Lille hand you to London Control who usually give you a DCT EGKA.

The above routings validate just using the waypoints shown, but you could force the desired route into the system using the method shown here to both avoid a stupid dogleg (which it is known ATC would never enforce) and to sidestep the French MAX DCT of 10nm which seems totally stupid.

I know a turboprop pilot (not on here AFAIK) who used the VORrrrddd method shown in the above link to fly across Europe, but I suspect he was just lucky because he never checked notams, and maybe he had “fun” enroute which he didn’t talk about. So if you are doing a long trip, you are stuck with the Eurocontrol routing from say the EuroGA router though maybe you can hack it around a bit.

In the UK, the EXAM callsign on the IFR flight plan would either avoid Eurocontrol validation totally or the UK ATC system would force the (possibly Eurocontrol-rejected) flight plan into the UK ATC system (I don’t know which). That was used for the IR test routes between the usual ATPL sausage machine places – Bournemouth Oxford Cambridge and such, which would cause havoc all around if you tried to file them for a real flight because they were at a silly low level like FL050.

Administrator
Shoreham EGKA, United Kingdom
42 Posts
Sign in to add your message

Back to Top