On Friday, March 13, due to the heavy volume of air traffic in the immediate area of interest for the eclipse (est. 15 eclipse flights plus crossing trans-Atlantic traffic), Isavia (Icelandic Air Traffic Control) issued a directive restricting eclipse flight operations only along two specific "tracks" designated "Eclipse East" and "Eclipse West".  The names reflect Isavia's intention to develop two specific corridors flanking (and roughly but not exactly parallel to) and equi-spaced by about 8 NM on either side of centerline.  Our flight (AB B737-800/DUS; later designated AB 1234) was an assigned a flight level of 35,000 ft (FL 350) on the East track, the other two Air Berlin flights (AB A320-200/DUS and AB A320-200/ZHR) were respectively assigned FL350 and FL340 on "Eclipse West".  At that point I was asked to develop revised Totality Run scenarios for all three AB flights for delivery to (and approval by) Isavia by way of AirEvents and Air Berlin.

The Isavia"tracks" were defined by way points of their creation provided in the directive to be used with "no deviation".  The way points, however were quantified in units of 15 minutes of arc (!) in Lat/Lon, so could not (and did not) exactly "parallel" centerline, and in fact had inflections (course changes!) at the way point track vertices.  Moreover, to ascertain the location of centerline in defining the "east"/"west" approximations for the two-tracks, Isavia consulted the NASA (Fred Espenak's) eclipse web site -- apparently not realizing the information provided there in was for sea level only!  As a result the "east" track was shifted by about 15.5 NM from centerline (at 09:43:30 UTC), while the "West" track was actually very close to centerline, for aircrafts operating at ~ 35,000 ft.  As a result, with replanning summarized below, the two AB A320 flights on the "west" track ended up very close to at-altitude centerline.

Click HERE for the FINAL (approved) revision for the three AB flight totality runs, defined simply by three waypoints conforming to the Isavia restrictions.  For "simplicity", and confined between Isavia waypoints, in iterated replanning I had put all three AB totality runs with mid-eclipse intercepts at 09:43:30 UTC, with the two A320's on the "west" track altitude stacked by 1,000 ft (so AOK for the same time-correlated UTC for mid-eclipse).

Note that the predicted duration(s) of totality I had given in the above linked summary document were for a no-wind condition only used for planning purposes.  With actual winds aloft, to maintain the requisite time-correlated ground-track, the aircraft ground speed (and thus duration of totality) would be different.  The "no wind" prediction (with lunar-limb profile corrections, of course) for "AB 1234" (the AB B737/DUS) flight was 03m 42.7s on the "east" track, and 03m 45.7s for the two A320 flights on the "west" track.


From a frame-by-frame examination of the original (15 Mby) images, the duration of totality as measured from the complete extinction of all photospheric Baily's Beads was 03m 39s ± 0.5 s. In (additional) detail (as provided to our pilots), an intermediate time-correlated way points for C2 was hit nearly dead on (1/2 second late), but C3 was hit appx 3-1/2 seconds "early".  The difference? WIND (as expected).

Here is the rest of the story... Just as we were completing our totality run and staring our turn back to Dusseldorf, I went back onto the flight deck to get a winds aloft reading from the aircraft FMS (flight management system) display.  You can see that as 46 knots from 341 degrees true (top left of the right hand display).  This was just about 6 minutes after mid eclipse, and the winds MAY have had some variability during the totality run, but this is a  first-order approximation much better than the a prior simplistic "no wind" condition.

With that wind vector, below is a re-computation of our (B737-800) totality run, with 1 minute time granulatity:

UTC Intercept: 09:43:30.3 | Duration of Totality: 3m 39.1s (limb profile corrections applied)
Flight Level:     35000ft | Apparent Horizon Depression: -3.3° w.r.t. astronomical
Course at mid-ecl: 42.59d | Cnt  hh:mm:ss.s  Alt-d Azm-d P-d     Cnt  hh:mm:ss.s  Alt-d Azm-d P-d
True Air Speed:   447.4kt | 2nd  09:41:39.3  +18.8 132.8 75.1    3rd  09:45:18.4  +19.2 134.5 240.9
Wind Speed:        46.0kt | Latitude:   63° 04' 24.8" N          Latitude:   63° 21' 48.0" N
Wind Direction:    341.0d | Longitude: 007° 30' 38.6" W          Longitude: 006° 47' 48.6" W
====================================================================================================================
        ________Center of the Umbral Shadow__________   ____________________________Aircraft________________________
 UTC    Longitude  Latitude  Width  Speed   Azm  Alt    Longitude Latitude Mid-dT   Mid-dD  LOS   Brng  Azim  Alt
HHMMSS    deg        deg     km     km/h     deg  deg    deg       deg        sec     NM     deg   deg    deg deg 
093430  -13.65115 +60.16720  474.2  3281.4 124.3 17.7   -8.86545 +62.49702   -540   -64.1   +3.0  46.50 129.5 18.1 P
093530  -12.94773 +60.50988  472.8  3256.2 125.3 17.9   -8.67958 +62.57825   -480   -57.0   +2.6  46.66 130.0 18.2 P
093630  -12.25438 +60.85634  471.4  3235.8 126.3 18.0   -8.49269 +62.65922   -420   -49.9   +2.1  46.83 130.4 18.3 P
093730  -11.56990 +61.20674  469.8  3219.9 127.3 18.2   -8.30478 +62.73995   -360   -42.7   +1.7  47.00 130.9 18.4 P
093830  -10.89314 +61.56120  468.2  3208.2 128.3 18.3   -8.11585 +62.82042   -300   -35.6   +1.2  47.17 131.4 18.5 P
093930  -10.22301 +61.91989  466.4  3200.5 129.3 18.4   -7.92588 +62.90063   -240   -28.5   +0.8  47.33 131.8 18.6 P
094030   -9.55851 +62.28295  464.7  3196.6 130.3 18.5   -7.73487 +62.98059   -180   -21.4   +0.3  47.51 132.3 18.7 P
094130   -8.89865 +62.65057  462.8  3196.2 131.3 18.6   -7.54282 +63.06029   -120   -14.2   -0.1  47.68 132.7 18.8 P
094230   -8.24250 +63.02293  460.9  3199.3 132.3 18.7   -7.34972 +63.13972    -60    -7.1   -0.6  47.85 133.2 18.9 T
094330   -7.58913 +63.40023  459.0  3205.7 133.3 18.7   -7.15556 +63.21889     -0    -0.0   -1.1  48.02 133.6 19.0 T
094430   -6.93765 +63.78267  457.1  3215.5 134.3 18.7   -6.96033 +63.29779    +60    +7.1   -1.5  48.20 134.1 19.1 T
094530   -6.28717 +64.17049  455.1  3228.5 135.3 18.7   -6.76404 +63.37642   +120   +14.2   -2.0  48.37 134.6 19.2 P
094630   -5.63681 +64.56393  453.1  3244.7 136.3 18.7   -6.56667 +63.45478   +180   +21.4   -2.5  48.55 135.0 19.3 P
094730   -4.98566 +64.96325  451.1  3264.2 137.3 18.7   -6.36823 +63.53287   +240   +28.5   -2.9  48.73 135.5 19.3 P
094830   -4.33282 +65.36875  449.1  3287.0 138.3 18.7   -6.16870 +63.61067   +300   +35.6   -3.4  48.90 136.0 19.4 P
094930   -3.67736 +65.78074  447.1  3313.1 139.3 18.6   -5.96807 +63.68820   +360   +42.7   -3.9  49.08 136.5 19.5 P

(see HERE for explanitory notes.)

Note the duration of totality: 3m 39s -- as measured by complete photospheric extinction with frames from the 2 fps imaging camera.  I do not know the wind vector for the two AB A320 aircraft, so I cannot compute the exact circumstances for those aircraft.  However, as they were "only" ~ 30 NM away, and at the same/similar altitude, it is likely the winds were similar during the totality run, and hence one may expect a very similar reduction of ~ 4 sec in their duration of totality.

---

And... as known, we were not alone.  Here (below) a visualization of the "crowded" skies from flightradar24.com.  Looks like, somehow, one aircraft (FYG = Flying Group, Belgium) ended up between the Isavia East and West tracks.  Further, it seems that two regularly scheduled Turkish Airlines (THY) flights from Chicago and Toronto to Istanbul were serendipitously at the right time and place.  From their headings as depicted, it seems the pilots may have gotten a great view of totality. However, it looks like the angle to the Sun too oblique for the starboard side passengers to have gotten a view of totality.


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Last update: 27 March 2015

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