Chinook - Still Hitting Back 3 (Merged)

[Robin Clark]

Various

..congrats to all the campaigners , good outcome.....

..for the sake of completeness there are a couple of observations I would like to put on record before the thread is closed....

...there is an error in the AAIB report on page 33 , para 5.10 , third line ,

"bearing of 012°G(015°M(L)"

should read "bearing of 012°G(21.5°M(L)" or alternatively "bearing of 012°G(016°M(OS)"............as per the definitions on page 31 of the same report .........a bit academic really.......

......as the local magnetic variation at the Mull was found to be 12.5 degrees West , this changes some of the other bearing information
for example the heading of 35 degrees found on the HP console , less 12.5 , gives 22.5 degrees , very close to the true heading flown in the period immediately after waypoint change as indicated by the GPS data....(22.23Deg.T)........
...so the chinook could have left the Irish coast using the 7.5 degree west variation published for the region.........and discovered that
this was no longer accurate as they approached the Mull......this should have directed them further west away from land........but may have formed a distraction for a time and may have prompted them to yaw to port and starboard in order to check heading info.??.....and
to compare and cross check the GM9 info with the TANS heading display....
......as we know they were flying closer to the Mull than planned due to accumulated errors on the waypoint location and GPS signal.....and this possible distraction may have delayed their awareness of their proximity until too late ........
...this compass difference may never have been noticed on a good VFR day , as the navigation is then done mostly visually with little reference to instruments..

...............I had refrained from mentioning this last point before , as it seemed somewhat unlikely.......but should be considered.........in plotting the locations of waypoints A and B , the co-ordinates appear to have been rounded down , which moved both waypoints to the South and East of the probable intended locations , exacerbating the danger of proximity to higher ground ........
.......all crew ( and probably most of their colleagues) it appears had served in other theatres such as Bosnia and the Gulf ................where their location was East of the Greenwich meridian ............in which case any rounding down of a co-ordinate in those theatres would move a location to the South and West of the true location.........
............In operating from NI , a posting significantly West of Greenwich this habit may have been applied automatically
and resulted in the waypoint moving inshore instead of offshore........

.....as suggested by others.........a combination of events which would each be insignificant when considered in isolation , may have added up to cause the accident.......

rgds Robin Clark....