Hi all in the forumPreparing a flightplan from EPWR to EGSS (using Vroute free version) two points on the plan I did not understand the format of. These were:RASUT/N0340F280 andNAROX/N0450F360In my ignorance I ignored the number part and just entered the names which the CDU accepted and had a great flight. I am now bothered that I do not know what the numbers mean and cannot find any reference to them on the net.Any help with an explaination would be welcome as sleep will be very minimal till I find out.Kind RegardsJohn Calleja (Armchair pilot)

Not sure, but perhaps they are block altitude restrictions. For RASUT you have to be below FL340 and above FL280, perhaps? I think I'm wrong though.Maybe they are coordinates. But then I don't know what the F stands for...Curious about these waypoints as well...

the numbers are showing the airspeed and the altidue you should have there i think... N0340 says (for example to the ATC) there you will have around 340 knots of airspeed, the F280 means, that you want to fly there at FL280 (28.000 feet)I hope i helped you :)

Hi John,The numbers you refer are as follows.RASUT/Airspeed and Flight Level 280NAROX/Airspeed and Flight Level 360Hope that helps Blueskies!!!!!

Hi John,The numbers you refer are as follows.RASUT/Airspeed and Flight Level 280NAROX/Airspeed and Flight Level 360Hope that helps Blueskies!!!!!

True airspeed or Indicated airspeed? Because if you go 340 KTS IAS, that would be overspeed...

True airspeed or Indicated airspeed? Because if you go 340 KTS IAS, that would be overspeed...

I think it's TAS (True airspeed).

Confirm it is TRUE airspeed

Hi GuysThanks for the heads up on this one, can sleep easy nowKind RegardsJohn Calleja (Armchair pilot)

Why would fix be restricted to a certain TAS? I would understand the altitude restriction, although with some reservations, but I can't get it for a TAS restriction... I think we are not getting this right guys. Speed restriction are always in IAS anyway.

Why would fix be restricted to a certain TAS? I would understand the altitude restriction, although with some reservations, but I can't get it for a TAS restriction... I think we are not getting this right guys. Speed restriction are always in IAS anyway.

It is probably the aircraft nominating a speed change (for whatever reason) and change of FL, not necessairly an ATC restriction.

Hi GuysDid a bit of further research on this as some doubt had arisen in some of the replies, so here is a cut and paste from a post from the Vatsim forum dated 2004 and the author's name is "image" explaining it is a format used for Step Climbs within a flight plan.NxxxFxxx means change of speed and/or altitude, N0421 means speed (true airspeed, TAS) 421 knots, F340 means Flight Level 340and in a further post by Chris Boustead VATUKF2 he shows that it cam also be in the format NIBOG/M080F350 guessing M is a Mach speedThanks to everyone for chipping in, it is of great help for learning.Kind RegardsJohn Calleja (Armchair pilot).

They aren't "restrictions", they are your filed planned speeds and levels. The reason they are in TAS (or Mach) rather than IAS is because your groundspeed is what ATC want to calculate for planning purposes (to maintain separation). I'm not entirely sure when Mach is filed for - I suspect it's when procedural separation is being used for example in oceanic ops when radar is not available for a long period, although it seems to me TAS would serve just as well in that context, so I'd like to hear from someone more knowledgable who knows when it's used.When you file, your stated cruising level and speed are the _first_ enroute speed and level, so after that you need to put it in the flightplan if you're changing speeds or levels. Like this:You'd initially planned for N0200 at FL250 (you've put this in the "speed" and "cruising level" boxes on the flightplan), you're doing that direct to FOO then following airway Z99 to BAR (at the same speed and level), then at BAR you want to accelerate to 300 KTAS and climb to FL380 to continue to QIK:DCT FOO Z99 BAR/N0300F380 DCT QIKSo the level and speed change starts after BAR. The speeds are N for knots, K for km/h, M for mach (eg. M080 is 0.80 mach), the levels are A for altitude and F for flight level

Hi Boris am not more knowledgeable than you but I guess I have had a few more beers and in my slightly intoxicated state I guess that Mach is better for oceanic separation as you can dial a Mach no into the MCP and you can't dial in TAS. Of course you can dial in IAS but at the levels used in oceanic crossings Mach is better.

Yes, you're probably right - I guess it might also be to do with level rather than oceanic, since above a given level everyone's operating on Mach number, so it makes sense to do it that way, and Mach number is directly related to TAS anyway (it's TAS divided by the local speed of sound).

Very commonly used with Concorde flightplans to advise ATC of altitude and speed changes as in the following real world flightplan. Heathrow – New York (FPL-BAW1-IS -CONC/H-SRWXY/C -EGLL1730 -N0563F280 CPT L9 MALBY DCT C/UPGAS/N0740F280F430 SL2 MERLY SL2 LESLU SL2 C/5041N01500W/M200F450PLUS NATSM 4700N05000W 4246N06500W 42N067W SM2A KENDA/M100F490 DCT LINND DCT OWENZ DCT CAMRN DCT -KJFK0328 KEWR -EET/EGGX0046 20W0058 30W0118 40W0139 50W0202 53W0209 60W0226 65W0239 67W0245 KENDA0258 LINND0303 OWENZ0310 CAMRN0318 REG/GBOAG SEL/BHFJ RMK/TCASEQUIPPED DOF/031023 IFP/RVSMVIOLATION ORGN/EGLLBAWD)