Date: 201910
Local time of day: 0001-0600
Location: IAH.Airport, TX
Flight conditions: VMC
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
Aircraft component: Engine Control
Component problem: Design; Improperly Operated
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Not Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Time Pressure; Confusion
Second reporter function: Captain; Pilot Not Flying
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Taxi
Result: Flight Crew FLC Overrode Automation; Flight Crew Returned To Gate; General Maintenance Action
Contributing factors: Aircraft; Human Factors
Primary problem: Ambiguous

Narrative: Normal sequence up to push; cleared to start #2 engine. Turned packs off; momentarily went to FLT start then moved switch to GND start; hacked clock. I am not sure when I added fuel as I usually do it at 25%N2 but today I cannot remember verifying that step but I know I did move the start lever to the idle detent; then saw EGT increasing past normal indications; kept watching thinking there is no way it was going to go past red line. N2 was at 42%; never got any higher than that. EGT went through red line; and I should have cut it off but I was under the understanding it was supposed to cut off itself for a hot start. Looked up the reference for the auto cutoff last line reads 'Current versions of EEC software (7.B.Q and later) automatically turn off the ignition and shut off fuel to the engine for an impending hot start or stall.' Not sure if this software was applicable to our jet today; and this certainly slowed my reaction time in getting the start lever to off. I was slow to cut off the start lever and did so once prompted by Captain. Got to 841 degrees. Performed IAI. Went to QRC then QRH. Back to gate and Maintenance came out.


Second narrative: During a routine pushback from gate to spot A at IAH I commanded engine number two to be started once the 'all clear' was issued by the tug driver. The aircraft had just been pivoted from the nose in (towards terminal) around to the nose out position (towards taxiway) as the FO (First Officer) began the engine start procedure. All of ZZZ data had been loaded and executed; the FO was unencumbered by any other tasks.Since the aircraft was approaching the release point I was not monitoring the engine start at all as I anticipated the 'set parking brake' instruction from the tug driver and was looking outside to ensure that the aircraft was no longer moving.Once the brakes were set I thought to myself that I had not heard the starter-cutout and I glanced down at the N2. The N2 was at 42% and not accelerating. I then glanced up at the starter switch as I was a bit disoriented; subjectively thinking that the start was taking a long time and that the starter had cut-out but that I had not heard it. As I was orienting myself to what was happening with the engine start the tug driver made his required calls and I informed him to remain in contact with me via the intercom. Once I saw the starter still engaged I looked back at the N2 which was still at 42% and I said to the FO 'it looks like a hung start.' As soon as I uttered my thought that we had a hung start I looked up at the EGT which was already approaching 800C and I said Hot Start. You are going to have to abort the start' to the FO. The FO replied that the aircraft had an auto-abort function that should abort the start. I commanded an aborted start again and told the FO that it made no difference what the book said; that the engine start had to be aborted and I reached for the start lever. At this point the FO aborted the start. I called for the QRC and then to go to the QRH. The aborted start procedures were completed and I contacted Maintenance for a return to the gate.


Synopsis: B737 pilot crew reported a possible hung start and aborted start up.