How commands work

The rules that apply to every command, whatever it does.

Addressing

To instruct an aircraft, lead with its callsign and a comma:

DLH123, dct ERNAS c 100 s 250 sq 2000

Commands that act on the simulation rather than on one aircraft need no callsign, and ignore one if you leave it in front. pause freezes all traffic even when the line reads as though it were addressed to the aircraft you happen to have selected.

That includes feedback, the problem report, whose text is free prose. report in front of a word is a question to the aircraft, such as report speed, and needs the aircraft's callsign in front of it.

Server commands in a private chat

Server commands also work in a private chat with SERVER. In Aurora, type .chat SERVER to open it, then type the command as you would on the frequency. The answer appears in that chat and nobody else reads it, which is useful for feedback in particular.

Instructions to an aircraft stay on the frequency, and typed in this chat they are refused. pause and resume are also announced on your frequency, because they stop or restart the traffic for everyone. delete needs the callsign here, as in delete DLH123. A command typed in a private chat with another controller is only a message to them. Trainers can also steer an aircraft from its own private chat, see Trainer.

A session started from the private chat calls its pilots on your primary frequency. If your client has not reported one yet, the session is refused, and you can start it on the frequency instead.

Spelling

• Commands are case-insensitive.

• Each command has exactly one spelling. The server does not accept variants; one it does not know is answered with a message saying so rather than being guessed at.

• Most verbs have a short form: the verb cut to a prefix or its initials, and the space before a number dropped. c070 is c 070. Both work and can be mixed in the same line. The space is part of the spelling rather than decoration around it, so the full form always takes it and the short form never does: abv 100 and c100+ are commands, abv100 and c 100+ are not. The hold is the one exception, because its parameters are separated by spaces: h MIQ 270 l 1.5min keeps them, and it is the hold's second short form, below, that drops them for commas. An empty cell in the overview means the verb has no spelling on that tier and nothing else; where the Short cell and both pad cells are empty, the full spelling is the only one. That is true of the three configuration verbs. dct has no short form and does have a pad form. The three spelled-out procedure clearances are the other way round again: their Short cell says "use c<NAME>[,<RWY>]", the short form of clr <NAME>, the one verb that clears any of the three by name.

  A verb that takes no argument has no space to drop, so it cannot separate its two letter forms the way c <ALT> and c<ALT> do. Every verb of that kind is written as two words and shortened to their initials, without exception: cancel speed and cs, cancel app and ca, cancel hold and ch, go around and ga, orbit left and ol, present heading and ph, sq ident and si. If you know the words, you know the short form.

• Six verbs have a second short form, listed in the same cell after the word or: one letter with the argument attached and no space at all. i26L clears the ILS and l26L the localiser; bare, i and l clear onto the runway you noted with expect. hMIQ,270,-,1.5min is a hold with its parameters separated by commas instead of spaces, and a bare h leaves it. s2000 is a squawk, told from a speed by its four digits. #26L notes the runway to expect. They exist for the controller who types these all day; the spelled-out and the first short form do the same thing and are what to learn first.

DLH123, dct ERNAS c 100 s 250 sq 2000
DLH123, dct ERNAS c100 s250 sq2000

Both lines are the same clearance; the second is the first typed short.

The number pad

Most verbs also have a third spelling that lives on the number pad, so a heading, a level and a speed can be typed with the right hand without looking away from the scope. Nobody has to use it. It exists for the controller who works fast enough that typing is what limits them. The pad has two kinds of key, and the reference tables show them in two columns:

• Pad signs are the operator keys, *, /, +, -, and ,. Most of these spellings are a single character carrying one meaning, and instructions are built by combining them.
• Pad digits are the digit keys, 8, 2, 4, 6 and 3, for the six instructions you give all day.

This is written for a German keyboard, where the pad's decimal key is a comma. On a US layout that key is a full stop, and the speed spellings below need the comma from the main keyboard.

DLH123, *+090 /070 ,220
DLH123, 6090 2070 ,220

Both lines are one clearance: right onto 090, down to FL070, speed 220. The first is all signs, the second uses the digits for the turn and the level, with the speed as a sign because there is no digit speed.

The pad below carries every pad spelling on the key it starts with. A digit key names the spelled-out command underneath, so that 8<ALT> and c <ALT> can be seen to be the same instruction; where the digit form takes no argument, as 3 takes no runway, only the verb is named. The sign keys list their spellings, and the two sections after the figure say what they mean.

The signs

Five rules cover the whole of it:

1. * sends the aircraft somewhere. Before a fix it is "go to" (*MIQ, or *MIQ,ROKIL across several), before a number it is a heading (*090), and alone it is present heading. / is the vertical and , is the speed.
2. A bare sign cancels or reverts. , releases the speed and * is present heading.
3. + and - are right and left where a direction in space is meant, and more and less on a scale. Doubled, they are an orbit: ++ to the right, -- to the left.
4. A space separates commands, a comma separates parameters inside one command. *MIQ,ROKIL is a route across two points. *MIQ, ROKIL, with a space after the comma, is read as nothing at all: the trailing comma stops even the first token being taken for a fix, so the whole line comes back unrecognised rather than half of it being flown. This is the easiest mistake to make in the whole scheme, and the server refusing outright is what keeps it cheap. The same rule holds for the route in its other two spellings, which is why route MIQ,ROKIL,ANELA takes commas too; see Lateral for the reason.
5. Every spelling mixes freely in one line, and the order you type them in changes nothing. That is the same rule as for every other spelling; see Combining commands below.

One thing the signs deliberately do not do. The vertical carries no direction, so /090 takes the aircraft to FL090 from wherever it happens to be. That costs you a check: c 090 typed at an aircraft above FL090 is refused as a climb that would descend, and /090 cannot be, because it never claimed a direction. Type the letter form where you want the server watching.

That same missing direction is what lets you write a limit on the slash: /100+ is a floor and /100- a ceiling, and neither can contradict a verb that never named a direction to begin with.

The digits

Six commands have a spelling made of digits and nothing else. The first digit is the verb, and where the key sits on the pad is what it means. 8 is at the top and climbs, 2 is at the bottom and descends, 4 is on the left and turns left, 6 is on the right and turns right. Whatever follows is the argument, exactly as it is in the other spellings.

DLH123, 8090     climb FL090
DLH123, 2090     descend FL090
DLH123, 4270     turn left onto 270
DLH123, 6270     turn right onto 270

3 is the approach clearance and 33 the localiser under it, doubling the same way the signs do for an orbit. These two are the only spellings in the whole command set that cannot carry a runway: digits alone cannot write 26L. So they clear onto the runway you noted with expect, and are refused when you have noted none. A runway typed after either one, 326L or 3 26L, is refused with the whole line rather than quietly ignored.

Two things the digits deliberately do not do. There is no digit speed and no digit limit: a spelling earns its place by how often you type it, the speed already has a one-character form in ,, and 8250+ is refused for the same reason c 100+ is. And unlike the slash, the digit vertical keeps the direction check, because 8 and 2 say climb and descend as plainly as c and d do: 2090 at an aircraft below FL090 is refused, where /090 would be flown.

Units

• Headings are magnetic, and take one, two or three digits: t 90 and t 090 are the same instruction. The one place three digits are required is a hold's inbound course, where 27 would be ambiguous with a leg length. A heading above 360 wraps rather than being refused, so t 380 flies 020.
• Altitudes: a bare number is a flight level (× 100 ft), so c 250 is FL250. Add ft for explicit feet: c 5000ft. A trailing + or - turns the target into a floor or a ceiling, so c100+ is "at or above FL100".
• Speeds are indicated airspeed in knots, with no suffix. There is no Mach command.
• There is no altimeter setting. The simulation models no QNH, so every altitude sits on one datum: d 4000 and FL040 mean the same thing, and there is no transition level to work around.

Combining commands

Put as many commands on one line as you like, in whatever order suits you. The server reads the line from the front, takes whichever command fits next, and repeats until the line is used up. Order changes nothing: these two are the same clearance.

DLH123, tr090 c100 s250 sq2000
DLH123, sq2000 s250 c100 tr090

These verbs have to be alone on the line. If anything else is on it, the whole line is refused: emergency · emergency now · emergency pause · emergency resume · emergency cancel · emergency status

These verbs take the rest of the line as their text, so nothing after them is flown: say

One instruction of each kind

A clearance may carry one lateral instruction, one altitude, one speed, one approach clearance, one runway to expect, one flap setting, one gear selection, one speedbrake setting, one squawk and one ident. Two of the same kind contradict each other, so the line is refused and nothing on it is flown:

DLH123, c100 c200        → refused: two altitudes
DLH123, t 090 ph         → refused: a turn and present heading
DLH123, #26L #08R        → refused: two runways to expect

The runway note counts separately from the approach clearance, which is why ca #26R is one instruction and not two of a kind: cancelling an approach and naming the next runway is what a runway change actually is.

Routes, procedures and directs join up

A direct, a route, a SID, a STAR and a transition are runs of legs rather than whole plans, so several of them make one longer plan, flown in the order you typed:

DLH123, dct MIQ cLANDU2A d100 s250

That flies to MIQ, then the arrival, and sets the level and speed on the way. The arrival is filed as LAND2A and published as LANDU 2A: either spelling reaches it.

A turn, present heading, an orbit, a hold, a hold cancel and a go-around are not legs, so none of them can stand beside one of the above. An approach clearance is independent of all of it, and can be given in the same line as the vector that sets it up:

DLH123, dct ROKIL clr ils 26L

If any of it cannot be read

Nothing on the line happens. You are told which part stopped it, so a typo never leaves you guessing which half of your clearance the aircraft took:

DLH123, tr090 c100 xyz   → cannot read "xyz": nothing was applied
DLH123, cNOSUCH c100     → no procedure of that name, and the climb is not flown either

An instruction that was understood but had nothing to do is not a refusal. cancel hold on an aircraft that is not holding says so and leaves the rest of the line alone.

If one part cannot be flown

A line the server understood is a different case, and here the rest of it does fly. Four things are dropped or reduced on their own, each with a note on frequency saying so:

• a climb to a level below the aircraft, or a descent to one above it
• a level above the type's service ceiling, which is lowered to the ceiling
• a flap setting above that setting's limit speed, which comes back to the deepest one allowed
• gear down above the speed the type may operate it at, which leaves the gear up

Everything else you put on that line is flown. Read the reply: it names which part did not take.