EZY6942 - reversal turns
 

Not sure if this is the right place to post this, but I was flying Keflavik-Edinburgh last night on EZY6942 and witnessed some strange manoeuvres. I'm not an airline pilot but have been an instructor for some years and also know a reasonable amount about ATC.

I wonder if anyone can shed light on the following?

About 20 minutes after departure from Keflavik, and I think just after levelling at FL390, we rolled into a right turn through at least 30 degrees. But when we rolled out of that turn, we continued rolling straight into a left turn through about the same heading change.

Then, about halfway into the flight, and just before crossing some opposite direction traffic below us, we rolled into a left turn through at least 30 degrees then once again immediately reversed the turn and kept that right turn going on to a new more southerly heading. It also looked like, after more or less levelling the wings, the aircraft was actually sitting right wing low for at least a minute after that turn, i.e. still in a gradual right turn. I got the impression that the aircraft may have been under manual control rather than AP.

On the initial approach into Edinburgh we had another reversed turn - although not as clear as the previous two. Then, when we finally emerged into VMC, we were on a left base leg for 24 from the SOUTH.

All very strange, so when I got home I did a playback on Flightradar24. This showed the "jink" 20 mins after takeoff, and also showed that there was no other traffic anywhere in the vicinity that might have explained the turns.

The playback doesn't show the second turn reversal, although it does show the heading change to the right just as we crossed the opposite direction traffic (which was 5000ft below us).

As regards the manoeuvres on approach to Edinburgh, we appear to have been initially under vectors to STIRA (initial approach fix) then on to an easterly heading, which would be normal for vectoring to a right base for 24. But then we turned right, crossed the final approach at 4000ft, and were then descended and turned left to join a left base. No obvious traffic reasons for sending us to the other side of the approach (although some aircraft don't show up on FR24).

I would have asked the captain as we left the aircraft but he was busy talking to someone else.

Anyone got any ideas?

EZY6942 - reversal turns
 

Maybe weather avoidance.

Sounds like a normal SLOP in when entering and leaving Oceanic airspace. This is when pilots select an offset from the airway by a certain distance, usually to the right of track and usually 1 or 2 miles. This is a normal safety procedure as this is procedural airspace.

EZY6942 - reversal turns
 

Was this "seat of the pants" guesswork, based on feel while in IMC? If so, you might as well discount anything you felt or thought you were doing.

Or it could just have been heading changes from ATC. THis is not uncommon (at least to me) and I often think it must make the passengers wonder what is going on. Quite often we get something like:

"Turn left heading 120"
"Sorry change of plan turn right heading 170"

Or even sometimes when changing frequency to another ATC unit, on leaving the first one they will tell us to resume our own navigation to XYZ which might be a left turn, then on contacting the next unit we are told to turn right back to the original heading.

EZY6942 - reversal turns
 

Or you just turned after passing a waypoint, and then were given a direct to another.

Having flown that very route many times it definitely sounds like SLOP to me. You can of course change a few settings in the FMGC to make the turn not quite so abrupt.

Thanks, all interesting. As regards SLOP:

(a) the first reversal turn occurred at or not long after the INGO VOR, but that's not on a designated Upper ATS Route as far as I can work out - and in any case, it's not in Oceanic airspace, it's in the Reykjavik CTA where there's full radar cover so why fly an offset?

(b) the second reversal turn was in the opposite direction - left then right. That would put the aeroplane on the left side of the centreline (if there was one) - so conflicting with anyone applying the standard right hand offset in the opposite direction.

(c) not long after the second reversal turn, we passed directly over opposite direction traffic 1000ft below us. That would suggest we were not flying any lateral offsets but were flying under radar control. Radar cover at FL390 looks like it is pretty much continuous between Scotland and Iceland, at least with SSR.

I wonder if this might have been an aircraft with a transponder failure, and the turns were radar identification turns?

You still haven't answered one question, where these turns based on you seeing the horizon move out the window, or you "feeling" the turns?

I've flown in IMC into airports where I know the routes and procedures by heart, at one time I could've sworn we made a 360 on the way in. Like you I actually was so curious I mentioned it to the flightcrew, who said it'd been a perfectly normal STAR with no vectoring.

My point being, if you based it on feeling things, and FR24 does not even show one of the turns, they most likely never happened.

He's a highly experienced instructions, he can feel the m turns with his very being.:cool:

I'm interested in this as well, it's something I've noticed on a lot of flights - sitting in the window and looking at the actual wings banking, so definitely not a mistaken seat of the pants feeling.

Often a shortish turn in one direction, before then making a larger turn in the opposite direction. Or vice versa. And on clear days without any visible weather around. I've noticed it more on short haul where I have a window seat more so it's not about entering oceanic airspace. I've always wondered, what else could it be?

I also have noticed the other situation the OP mentions, where the aircraft sits wing low for a loooong time after a turn. I've noticed both these things quite a lot so assume you guys can fill us in, thanks! :ok:

Crazy Voyager: no, sir, I was not "feeling" the turns while in IMC. But thanks for your helpful suggestion.:)

I used to carry out that manoeuvre sometimes when I or P2 wanted to look below at something.:)

On reflection I think those of you suggesting SLOP are probably right, even though this was not in NAT airspace. What I saw would be compatible with:

1. On reaching VOR INGO, opting to take up a track 1nm or 2nm right of track
2. On reaching RATSU, opting to go back to a direct track en route to the STN VOR

Larson has the answer:

http://lolbot.net/pix/20938.jpg

I'm glad NorthSouth figured out the answer, I know I was fixing to start losing sleep over it.

NorthSouth, the whole BIRD area is indeed oceanic by definition and inside MNPS even though most of it around Iceland is covered by radar. Flying from Iceland to northern Scotland, and between Iceland and Norway south of around 66N is fully covered by radar. Nevertheless a oceanic clearance is still required even though being covered by radar the whole route, as per above.


This sounds a bit like a SLOP was being done as other posters suggested.
Having said that, I would put a big questionmark to doing a SLOP when under radar and on a random route. The SLOP is intended and strongly recommended for oceanic flights when NOT under radar and especially on the NAT tracks where you have multiple aircrafts on the same route. I do not see the point in doing that on a random route. In rare cases the NAT tracks do go over Iceland, then and only then it is recommended to stay on a already established SLOP if that is being utilized when transiting through a mid ocean radar area which makes sense if you are on a NAT track.


So I would say doing a SLOP on a "Blue Spruce" route from Iceland to Scotland is a HUGE overkill

ICAO Paris MNPS Rules
 

8.5.3
Consequently, SLOP is now a standard operating procedure for the entire NAT Region and pilots are required to adopt this procedure as is appropriate.


That said you can always offset zero should you wish.


In section 8.5.3 subpart
F: Aircraft transiting ATS Surveillance-controlled airspace mid-ocean should remain on their already established offset positions.

Yes but I would say this section is referring to non-radar area, hence the "as appropriate" and also as per section 8.5.1. even though one cannot really say it is crystal clear.

The locals do not utilise SLOP in that area. Only maybe when westbound and out of radar area as for them it is always a random route.


Iceland AIP wording is a little different:
ENR 1.8.11.7.1. section 5:


"Aircraft transiting oceanic radar areas may remain on their established offset positions."


Keyword here is transiting. Therefore I would say that for a flight to/from BIKF would not be appropriate to do a SLOP in that area and under radar.