2011-07 · NASA ASRS report 960763
Anchorage Center took exception to what they considered an early turn by a Learjet flying the obstacle clearance departure procedure from PAWG to LVD VOR; thence on course to YYJ VOR.
We departed PAWG on the obstacle departure procedure toward LVD VOR. Our next waypoint was YYJ; which was approximately a 140 degree turn to the left. After accelerating above 10;000 FT (we had been cleared to FL280); our FMS commanded a predictive turn toward YYJ before crossing LVD. During the turn; we selected direct YYJ; which centered our course needle and our turn radius decreased. Some time after this; Anchorage Center established radar contact with us and asked us if we had crossed the LVD VOR on our departure. We explained the FMS predictive turn but the Controller implied that we had made a lateral navigation error. We were not informed of any pilot deviation nor given a phone number to contact during or after the flight. At no time was obstacle clearance an issue for us; but we felt that we didn't want to cause any confusion with the controlling facility. In the future; we will fly this procedure using short range navigation source (raw data) to prevent having our waypoint dropped by the FMS and turning early as it anticipates the course change. We will also avoid using the direct command on the FMS; as the resulting course line may be shifted from what ATC is expecting to see.
While in the turn I selected a 'direct' YYJ which increased our bank angle and reduced the radius of our turn. The result was an new flight path slightly east the direct course from LVD to YYJ.This situation can be avoided in the future by 1. flying LVD as a 'fly over' not a 'fly by' waypoint; or 2. by using VOR as the primary navigational source.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.
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