Date: 201404
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: Marginal
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Final Approach
Airspace: Class B ZZZ
ATC / advisory: TRACON ZZZ
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Human-Machine Interface; Situational Awareness
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Fuel Issue; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Diverted; Flight Crew Landed in Emergency Condition; General Declared Emergency
Contributing factors: Procedure; Human Factors; Weather
Primary problem: Ambiguous

Narrative: I was flying; at 3;000 FT on vectors for the RNAV (GPS) with a Circle to Land. After turning on to a heading of 130 degrees I selected VNAV/LNAV (before I was actually cleared for the approach). The autopilot initiated a turn to intercept the final course and by the time I realized it the jet had turned approximately 10 degrees to the right. When I did realize it I attempted to turn the airplane back to a heading of 130 degrees; at which time VNAV/LNAV dropped off. Concurrently I was cleared for the approach and while trying to re-engage LNAV/VNAV I overshot final. The Controller cancelled my approach clearance and I was given a heading and climb to 3;000 FT. Also at this time a windshear report of + 25 KTS was reported and the controllers informed all airborne of an approach change to the ILS. We were told that before any of us could shoot the ILS airspace would have to be released! We were told this would take an additional 10-15 minutes. Fuel on Board was 4;900 LBS and I elected to divert. ATC immediately did start vectoring me; however with the weather and traffic the controllers were quite busy and I felt that being in the normal lineup was not compatible with my fuel state. With my eye on the fuel I elected to declare an emergency to expedite and receive priority. What was pointed out to me after the fact that my use of the terminology 'Emergency Fuel' might have led to confusion on the part of the controllers. I was given the RNAV approach. I was again on a 90 degrees leg to final; but had not received an intercept heading to the final approach course. As we came within a half mile of the approach course I again reminded ATC that we were emergency fuel. After crossing the final and at 2;900 LBS of fuel; without an approach clearance; I initiated a right turn back to final and a descent and commenced the approach procedure. ATC had to move some traffic 3 miles in front and 500 FT below us. We continued the approach to landing and touched down with 2;500 LBS of fuel on board. We taxied to a gate and after deplaning all passengers (passenger service decision) and flight attendants (self initiated) we fueled and ferried the airplane. In the heat of the moment I used somewhat vague terminology. I was reminded that the two terms applicable for my situation were either 'Minimum Fuel' or 'Emergency.' Somewhere in between probably added to the confusion. I also talked to a TRACON Supervisor the next day about my incident. What he did explain to me is that the corporate knowledge amongst controllers was probably being thinned out (my words not his) due to the relatively new hires. He said that at his experience level of 30+ years when he hears anything containing the word 'Fuel' he's going to start asking questions of the cockpit! On the other side of the coin a controller at 6 years probably does not have the institutional knowledge and it might not invoke the same level of attention. He also said if in doubt plain spoken descriptions probably would have raised the flag sooner and higher! He actually pulled the tapes and listened to them. He was going to have the Controller at the scope that night and the Supervisor review them as a sort of training session for my situation. I was grateful to be able to speak with this TRACON Supervisor!


Second narrative: Flight was scheduled to ZZZ. But after an aborted approach and subsequent runway change at ZZZ; we didn't have enough fuel to wait out the runway change; so we diverted. Enroute; the Captain declared emergency fuel with Approach. Approach told us they were vectoring us for the RNAV (GPS); and then vectored us thru final. We queried Approach and told them again we were emergency fuel. They told us to turn right and intercept the LOC. We told them we were expecting right runway. Approach gave us a new heading to intercept the final for RNAV to the right and told us to maintain 3;000 FT. Approaching the final course between ZZZZZ and ZZZZZ1 still at 3;000 FT; we asked for lower. Approach said they were unable due traffic to parallel runway. The Captain said we needed lower and then exercised his Captains Emergency Authority to begin descent before being cleared for the approach or being cleared lower. At about 2;400 FT Approach cleared us for the RNAV 22R approach. No TA/RA occurred and the remainder of the approach was uneventful.


Synopsis: B737-800 flight crew reports the Captain's (pilot flying) early selection of LNAV/VNAV during vectors for an RNAV approach; resulting in a track deviation and ultimately a missed approach. Holding instructions are issued while the landing runway is changed and the crew elects to divert to a near by alternate. Emergency fuel is declared and the flight ends up landing with 2;500 LBS of fuel. When ATC is slow to clear the flight for the approach due to traffic on a parallel runway the Captain initiates the approach on his own; reminding ATC of his emergency status.