Date: 201708
Local time of day: 1201-1800
Location: PDX.Airport, OR
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class E P80
ATC / advisory: TRACON P80
Aircraft component: Trailing Edge Flap
Component problem: Failed
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Confusion
Anomaly: Aircraft Equipment Problem Less Severe
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew FLC complied w / Automation / Advisory; Flight Crew Landed in Emergency Condition
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: I was the Captain and Pilot Monitoring for this flight. On vectors; and approaching the final approach course for Runway 28L in PDX; the FO (Pilot Flying) announced 'below 240' and asked for flaps 1. I verified the speed and put the handle to 1; but the flap indicator needles did not move out of the 'up' position; nor did the amber leading edge FLAPS TRANSIT light illuminate to indicate that any leading edge device was in transit. We had no leading edge devices and no trailing edge devices with the flap handle in the flaps 1 position. I checked hydraulic pressure and the overhead hydraulic panel and all indications were normal. Just then; the Approach Controller cleared us from 5;500 ft to 3;000 ft and cleared us to intercept the localizer; but I requested that we remain at 5;500 ft and asked her for further vectors while we troubleshoot a problem. She approved 5;500 ft and issued vectors. I reminded the FO that he has the airplane and added that he has the radios; too. Then I got into the QRH to work the problem.I ran several QRH flap configuration checklists; as required; beginning with the Trailing Edge Flap Disagree checklist; and ultimately ending with the Trailing Edge Flaps Up Landing checklist. In accordance with the Trailing Edge Flap Disagree checklist; I fully extended the leading edge devices and attempted to extend the trailing edge flaps; using alternate flap extension. We encountered a trailing edge flap asymmetry between flaps up and flaps 1; so I discontinued alternate flap extension in accordance with the checklist. At this point; when I discovered that we would be landing flaps up; I [advised] approach control and requested ARFF. I completed the final QRH checklist for the Trailing Edge Flaps Up Landing.In an effort to help others in the future; I would like to comment on the brief confusion I encountered while running the first checklist that addressed our problem - the Trailing Edge Flap Disagree checklist. In our case; the flaps were up before we ever entered the checklist. They did not fail in an intermediate position; nor was there any asymmetry at first; since the flaps were up. Because of this; when I got to step 6 in the checklist; I was left without any good options to complete that step. Step 6 says; 'Check the Non-Normal configuration landing distance from the B737 Land application; or from the following 3 tables...' I chose the Land application; since it's what we use every day. But when I got the 'Failure' dropdown menu on the Non-Normal page; I felt that none of the options were perfectly appropriate for our situation. I chose 'FLIGHT CONTROLS;' and from there; I had several choices. But none of the choices in the dropdown menu were quite right at this point in the checklist. Our flaps were still up. We hadn't yet extended them via alternate means; because we weren't yet at that point in the checklist. The failure choices available to me within the application were all titled in accordance with the various Non-Normal checklists. I was appropriately in the Trailing Edge Flap Disagree checklist; but all of the Trailing Edge Flap Disagree choices in the dropdown menu were for flap settings other than up. For this reason; none of those choices struck me as appropriate.I also saw two other dropdown menu failure choices that better fit our scenario - 'All Flaps Up' and 'Trailing Edge Flaps Up Landing.' But; I had not yet entered either of those other checklists; so it seemed inappropriate to choose one of those failures without knowing with certainty which checklist would eventually conclude our configuration changes. I then thought; 'Well; I guess I'll use one of the 3 tables within the checklist instead.' But; no. The 3 tables within the checklist were also for flap settings that did not match our current flap setting of up. This caused some brief confusion. Although it felt a little uncomfortable; I elected to continue the Trailing Edge Flaps Up Disagree checklist by skipping step 6 and moving on to step 7; assuming (correctly; it turns out) that I would eventually be guided to a more appropriate Landing Distance solution.Continuing with step 7 of this first checklist (Trailing Edge Flaps Disagree); I attempted to extend the flaps via Alternate Extension. When the two needles split during alternate extension (to approximately .5 on the left and .8 on the right); I released the switch to stop the extension; as I interpreted this to be a flap asymmetry. We now had Trailing Edge Flaps between up and 1 degree; and we had all Leading Edge Devices fully extended. I then entered the Trailing Edge Flap Asymmetry checklist in accordance with the Trailing Edge Flap Disagree checklist. This checklist directed me to the Trailing Edge Flaps Up Landing checklist; which is the checklist that concluded our configuration changes and finally directed me to the Land application again - this time; allowing me to more confidently choose an appropriate failure choice ('Trailing Edge Flaps Up Landing') and compute a Landing Distance.I thought it important to explain the necessity I felt to skip a step in a QRH Non-Normal checklist and the brief 'discomfort' that caused; as skipping QRH checklist steps goes against many years of training.I [advised the] FAs and made a quick PA to the passengers. It was the FO's leg and we discussed the options - his landing or my landing. We agreed that he would continue to fly the approach and land. I asked Approach Control to contact [our company]; and he agreed to do so. We landed approximately 10 minutes after I [advised ATC]. We requested that the fire trucks follow us to the gate. After a moderate to long taxi towards the gate; we stopped short of the ramp to allow ARFF to inspect us more closely and take a reading of our brake temperatures. They were 460 degrees. ARFF recommended that we continue to the gate and we agreed that they would follow us there. Once there; they directed large fans towards our brakes and monitored the temperatures. The temperatures went up before they went back down; as expected. ARFF directed all personnel to remain clear of the aircraft; so baggage handling was necessarily delayed. Once the chocks were in place and the FO visually checked the area and notified the ground crew of our intentions; I released the parking brakes. I checked the Brake Cooling Chart in the QRH and determined that the brakes would normally take 80 minutes to cool under our conditions on the ground; but the fire crew advised me that the brakes were at 190 and 120 degrees respectively before I was finished making all the write-up's in the logbook. So; the 80 minute number was very conservative considering that we had large fans cooling our brakes. When the fire crew left; baggage handling began.Once the parking checklist was complete; I called Dispatch to ensure he got the word. He had not yet been notified of our [situation] but had received a call from 'operations' asking him if he 'knew what was going on with our aircraft.' I filled him in on the details and answered his questions. I then contacted Maintenance Control to discuss the malfunctions and any specifics he might want in the logbook. I wrote up the flap problem and the right hydraulic quantity of 72RF. I also wrote up the touchdown speed; brake application speed; and brake cooling chart results at Maintenance Control's request.Incidentally; I would also like to mention something new I learned about the aircraft from this experience. It only became clear to me after I spoke with Maintenance Control from the arrival gate following the situation. As the Pilot Monitoring; I was responsible for retracting the flaps at the FO's command on departure from ZZZ. When I brought the flaps to 'up' on the climb out from ZZZ; 4 hours prior to the flap extension malfunction; I noticed something unusual. But being fairly new on the airplane (about 16 months and almost 900 hours); I wasn't 100% certain if I was seeing something new; or if I had simply never noticed it before. So I didn't mention anything to the FO. The flaps retracted normally from flaps 1 to flaps up; with no indication of flap asymmetry; and the amber leading edge light went out normally when the flaps were in the up position; but I noticed that the needles suddenly split once they reached the up position. The right needle sat on the up indication; as both needles usually do. But the left needle suddenly drooped slightly below the up indication; and this is what I had never noticed before. I thought it was unusual. But I wasn't 100% sure; so I didn't say anything. But after we encountered the flap malfunction and the inability to extend the flaps; that unusual indication stayed fresh on my mind. When I got a chance to call Maintenance Control after the Parking checklist; I asked him about what I saw on flap retraction 5 hours earlier. He surprised me by saying that it WAS unusual and that it was probably an important clue that would help maintenance narrow their search for the cause of the problem. He said that it probably signaled that one of our left skew sensors failed. I found this to be very interesting and thought it might be helpful information for others who had not yet encountered this indication.




Synopsis: B737-800 Captain reported a flap malfunction and difficulty selecting which QRH flap configuration checklist to use.