Narrative:

We diverted to cos from the west. We were flying south towards cos and cleared direct to a fix (flood); which was south of our position. The subsequent clearance was turn to a heading of 100 after reaching flood. We had flood on the top line of the legs page. We were able to get the ATIS for cos and they were landing ILS 17L. I then programmed ILS 17L from the arrival page for cos. Since we were in a -300 without a map; or even a bearing pointer to the field; we had minimal situational awareness of our true position; other than we were 25 miles north of flood. I closed the discontinuity from flood to the first point on the ILS 17L. This gave us a descent ETA and fuel on arrival; which dispatch asked for via ACARS. Thinking we had plenty of time before reaching flood and turning to the 100 heading; I used the right CDU to ACARS dispatch with the information. Just after I hit send; the plane started turning left; and flood was no longer on line 1 of the legs page. I then hit heading select 100 degrees while the plane was in a left turn. We did not recognize that the LNAV started turning seven miles prior to flood to meet the course for the first point on the ILS. The turn was about 160 degrees; so the lead required was substantial. In the turn; ATC said we were heading for restricted airspace to the east and gave us an immediate vector back to the south. We did not enter the restricted airspace; but our situational awareness on its location was nil. It took us a while just to find out our position relative to flood; because it had already dropped off the legs page. The controller was very helpful; and we told him we weren't certain why the plane started the early turn; and thanked him for the heads-up. We were on a vector from there until on final for 17L at cos. We were kind of set up for failure on this one. The divert kit has no arrivals for cos; so we needed vectors. We were given one point; and then a heading. I should not have closed the discontinuity between flood and the ILS. But being so busy with the weather; a divert to an off line alternate; and coordination with dispatch on the particulars; that piece of knowledge just slipped by me. Any B737 with the map display would've graphically shown our route and significantly increased our positional situational awareness. With no map; and a VOR/LNAV switch in the -300; we don't even have a bearing pointer to the field in the LNAV position. Trying to gain/maintain positional situational awareness; in the weather; during a divert to an unfamiliar field is no small challenge. At least the fly-over versus the fly-by fix will be in my bag of tricks now; and more prevalent in my thinking since I've been burned once.

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Original NASA ASRS Text

Title: A B737-300 aircraft with no map is diverted to COS; an off line airport. The FMS was programmed for the arrival but the crew had very poor situational awareness and turned early. ATC issued vectors to keep them away from restricted airspace.

Narrative: We diverted to COS from the west. We were flying south towards COS and cleared direct to a fix (FLOOD); which was south of our position. The subsequent clearance was turn to a heading of 100 after reaching FLOOD. We had FLOOD on the top line of the LEGS page. We were able to get the ATIS for COS and they were landing ILS 17L. I then programmed ILS 17L from the arrival page for COS. Since we were in a -300 without a map; or even a bearing pointer to the field; we had minimal situational awareness of our true position; other than we were 25 miles north of FLOOD. I closed the discontinuity from FLOOD to the first point on the ILS 17L. This gave us a descent ETA and fuel on arrival; which Dispatch asked for via ACARS. Thinking we had plenty of time before reaching FLOOD and turning to the 100 heading; I used the right CDU to ACARS Dispatch with the information. Just after I hit send; the plane started turning left; and FLOOD was no longer on line 1 of the LEGS page. I then hit Heading Select 100 degrees while the plane was in a left turn. We did not recognize that the LNAV started turning seven miles prior to FLOOD to meet the course for the first point on the ILS. The turn was about 160 degrees; so the lead required was substantial. In the turn; ATC said we were heading for restricted airspace to the east and gave us an immediate vector back to the south. We did not enter the restricted airspace; but our situational awareness on its location was nil. It took us a while just to find out our position relative to FLOOD; because it had already dropped off the LEGS page. The Controller was very helpful; and we told him we weren't certain why the plane started the early turn; and thanked him for the heads-up. We were on a vector from there until on final for 17L at COS. We were kind of set up for failure on this one. The divert kit has no arrivals for COS; so we needed vectors. We were given one point; and then a heading. I should not have closed the discontinuity between FLOOD and the ILS. But being so busy with the weather; a divert to an off line alternate; and coordination with Dispatch on the particulars; that piece of knowledge just slipped by me. Any B737 with the map display would've graphically shown our route and significantly increased our positional situational awareness. With no map; and a VOR/LNAV switch in the -300; we don't even have a bearing pointer to the field in the LNAV position. Trying to gain/maintain positional situational awareness; in the weather; during a divert to an unfamiliar field is no small challenge. At least the fly-over versus the fly-by fix will be in my bag of tricks now; and more prevalent in my thinking since I've been burned once.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.