I agree that if it matters, one of the aircraft will be assigned a new heading, but not a track. In the vast majority of the cases, the speeds will be matched close enough and the runway spacing will provide for separation. Some airports such as at KSFO will stagger departures off of the parallel runways because they are too close to one another.
The PCG is perfectly clear for FAA ops:
RUNWAY HEADING- The magnetic direction that corresponds with the runway centerline extended, not the painted runway number. When cleared to “fly or maintain runway heading,” pilots are expected to fly or maintain the heading that corresponds with the extended centerline of the departure runway. Drift correction shall not be applied; e.g., Runway 4, actual magnetic heading of the runway centerline 044, fly 044.
QuoteTwo aircraft departing from parallel runways will maintain separation from each other if they both fly the heading.
If they are flying at the same level and the same speed, yes. But not if the faster one is overtaking the slower one. The linear crosstrack drift will depend on how long the aircraft has been airborne, and so the original separation will be reduced by the crosswind velocity times the difference in airborne time. That could easily be half a mile. So I think any controller who wanted to ensure separation would give you a number to fly, and adjust it as necessary.
The fact that there is any debate about this is a good reason to avoid the instruction in any circumstances where it matters, to the precision of the drift angle, what the pilot does.
In the US, if assigned a heading to fly, we are not expected or permitted to apply a wind correction and fly a track instead. If a procedure has a DR heading leg, we fly the heading and the TERPS has already considered a planned worst case wind effect from the point of view of obstacle clearance. When operating at a towered airport with parallel runways and given instructions to fly runway heading, we are expected to fly a heading that corresponds to the runway magnetic alignment. Two aircraft departing from parallel runways will maintain separation from each other if they both fly the heading. If the down wind aircraft decides to fly a track, they can cause separation to be lost and get too close to the aircraft on the upwind parallel who is following instructions and flying a heading. If the initial leg is part of a SID or ODP and includes a course or track, then that is flown as a track. I don’t ever recall receiving a departure clearance from a towered airport in the US to fly a track that is not part of a procedure.
As I suggested there will be many people like yourself who know more how that sort of thing would be managed. Whether or not that is a probably scenario isn’t really what I was aiming to achieve. I just don’t see why it would be sensible/expected to fly a track when you are told to fly a heading, especially when there is phraseology available for asking to maintain track, and yes I appreciate that no one should perhaps be saying “runway heading” but at the end of the day, plenty do.
So my thinking is that as an example, if at airport XYZ, there is a E/W runway and a transiting aircraft flying parallel to the runway, then a reasonable method of separation would be to ask a departing aircraft to maintain runway heading (perhaps not correct, but have had the instruction myself in the uk) until instructed by radar. This gives a good chance of separation until radar gets hold of you and sees you have climbed above/fallen behind/gone ahead of the other traffic and can turn.
So the runway is 270 and there’s a strong southerly wind at 3000 ft. The transiting aircraft is at 3000 ft 3 miles to the south tracking 300 and is on a radar heading of 270. An aircraft gets airborne and needs to be separated from the transiting aircraft. Do you really think the controller is going to say “maintain runway heading” and assume that the pilot of the aircraft getting airborne will allow it to drift 30 degrees right of the extended centreline as it climbs through MSA? Even assuming that the wind at the surface is the same as at 3000 ft, which it typically isn’t.
From the Original Post:
“…In my opinion the instruction did not make sense. You cannot maintain something you do not have – the runway heading. I was flying runway track….”
Just a nuance in language usage here for interest…in the US when the controller says for example “maintain 8000ft” and you are at say 5000ft he means (in European language) “climb and maintain 8000ft”…..so “maintain” in that case doesn’t mean keep what you have…
I will concede to being wrong / against the grain of the general agreement then.
As I see it saying runway heading is just an easier way of saying the actual number. If the runway heading was 360 I would fly runway heading as heading 360 with no wind. Likewise I would fly heading 360 as heading 360 (of course).
Anyone that knows better, please enlighten me if I am wrong, but having visited a fair few local towers to get to know how the ATCOs in the area work, I know that they much prefer to give direct to waypoints, and use headings mainly for separation with other traffic. It is reasonable to expect that two similar aircraft flying the same heading will follow more or less the same track. This breaks down a bit if they both try to fly a track and one of them for example is using a GPS derived track and the other is using a forecasted wind from 6 hours ago which could not uncommonly be WAY off the mark.
So my thinking is that as an example, if at airport XYZ, there is a E/W runway and a transiting aircraft flying parallel to the runway, then a reasonable method of separation would be to ask a departing aircraft to maintain runway heading (perhaps not correct, but have had the instruction myself in the uk) until instructed by radar. This gives a good chance of separation until radar gets hold of you and sees you have climbed above/fallen behind/gone ahead of the other traffic and can turn.
I am not arguing here that I am correct, merely trying to explain my thoughts on why I think it makes more logical sense to flying the instruction ‘runway heading’ as a heading.
I don’t see why there should be any confusion about what runway heading means. A heading is a heading is a heading.
It’s not that simple, unfortunately. PANS-OPS is the standard document for flying and constructing procedures. Almost on the first text page in PANS-OPS volume I, it is stated:
All procedures depict tracks. Pilots should attempt to maintain the track by applying corrections to heading for known wind.
…and then the word “heading” is in effect used to mean “the heading which will maintain the appropriate track”.
So it is not at all unreasonable that “maintain runway heading” should mean that the pilot should select a heading to (attempt to) maintain a track along the extended runway centerline.
I googled several discussion about this in PPRuNe and it seems to be a general agreement that if you fly in airspace designed according to PANS-OPS, you should correct for wind. If you fly in airspace designed according to TERPS (U.S. regulations) you should not.
The phrase " maintain runway heading" is not used in the UK. Two forms are permitted:
BIGJET 347, after departure track extended centre line
BIGJET 347, after departure climb straight ahead
ICAO Doc 4444 PANS-ATM (or at least the last version I’ve got) says
[AFTER DEPARTURE] TURN RIGHT (or LEFT) HEADING (three digits) (or CONTINUE RUNWAY HEADING) (or TRACK EXTENDED CENTRE LINE) TO (level or significant point) [(other instructions as required)];
BTW I see no reason to interpret maintain runway heading as “point your aircraft in the direction of the runway”. It could equally be interpreted as “maintain the heading that tracks along the runway”. The ambiguity was one of the reasons for the UK’s abolition of the phraseology.
