2011-02 · NASA ASRS report 937482
A CE560XL crew reported an engine nearly over tempted during a cold weather start when N1 failed to rotate until about 22% N2. Fuel was cutoff then reintroduced after the ITT dropped but was cutoff again due to an engine vibration.
Event occurred during a fuel stop. Weather conditions were approximately 600-800 overcast with light snow. Due to weather conditions; we needed to de-ice aircraft. FBO personnel informed us we were number three in line to de-ice behind a couple of airline aircraft. We were on ground approximately forty five minutes to one hour before event occurred. Captain notified me de-ice personnel would call us on radio to let us know when they were finished de-icing airline. During this time; passengers were re-loaded and briefed. As I was getting buckled into my seat; FBO de-ice personnel called us on radio to let us know they were finished de-icing airline and were heading to the designated de-icing area. The de-ice area was in a different location than our aircraft was on FBO ramp; so we needed to start engines and taxi to de-ice area. At this time I grabbed the checklist to commence the Engine Start Checklist. I'm not 100% sure when during the checklist the Captain had commenced starting the Left engine. Being caught off guard I made a split second decision to finish checklist to ensure it was done. Hindsight being 20/20 I now realize I should have stopped and focused on engine start. Immediately after finishing checklist I looked up at engine instruments and started scanning. First thing I noticed was the ITT near but below red line and falling. As I noticed this the Captain was simultaneously returning thrust lever to idle cut-off which caused ITT to immediately reduce further. I had looked for N1 rotation immediately after ITT caught my attention and noticed N1 was spinning. As ITT was cooling the Captain immediately re-introduced the thrust lever out of idle cut-off. Engine restarted and ran with normal indications on engine instruments. During this process I asked Captain if he had seen the ITT go above redline. I was not 100% sure if I saw the top out of the ITT as I initially saw it below redline and falling. Captain said it did not. Captain stated he saw N1 start rotating around 21-23% N2; and ITT started rising rapidly at same time; that's when he took thrust lever to idle cut-off. After this sequence; the engine was running normal within parameters on engine instruments. At this time; I was gathering my thoughts with what I had seen to determine what had happened during engine start. Captain then started the right engine. I focused on the starting of the engine. Engine started normally within parameters. Shortly after the right engine stabilized I noticed a vibration that I hadn't felt since we had been flying the aircraft. I asked the Captain if he felt it; he did. After discussion of the left engine start and potential hot start that may have occurred; we decided to shut down the left engine to see if vibration went away. The vibration ceased after shutdown of the left engine. We decided to shut the right engine down. The Captain called the Assistant Chief Pilot (ACP) on duty while I briefed the passengers. Five to ten minutes after Captain's conversation with the ACP the ACP called the Captain and informed him that he conferred with Maintenance and would like us to 'dry motor' engine for thirty seconds; then to restart to see if vibration has gone away. Captain dry motored the left engine for thirty seconds then started engine. Engine started normally within parameters; however; vibration was still present. Captain shutdown engine and called ACP. During final walk around I noticed the right engine fan spinning with the wind; but left engine was not spinning. Captain said he had noticed the same thing during his walk around. The weather was overcast with light snow. The wings had collected snow on them which made them too slick to climb upon and check to see if the left engine fan was frozen. As a crew awareness of the weather conditions and extra vigilance during engine start is crucial in these conditions. Completing checklists per SOP's and ensuring both crew members are prepared for engine start allows for full attention to be provided preventing such occurrences from happening. For myself: During the engine start; being caught off guard; I made a split second decision to complete the checklist. Shortly after the event occurred I walked my way back through the entire sequence. Although the Captain commenced starting the engine prior to checklist completion; I realize I should have adverted my attention away from the checklist to the engine start. This would have provided attention from both crew members during entire engine start. It's a mistake I made on my part and have learned much from this experience. More importantly; going forward; I will ensure the crew continues to follow checklists and SOP's to prevent further events such as this one. At this time; I am unsure whether or not a Hot Start had occurred on the left engine.
During engine #1 start up N1 occurred at 21-23% N2 but ITT shot up (stayed in the green) so I immediately pulled the throttle to cut off. ITT immediately dropped so I put throttle back into idle. Engine ran normally at first but then started a vibration so I shut it down. Since we had passengers on board I called the duty Assistant Chief Pilot (ACP) and told him what had happened. He said that he would get with Maintenance and get back to me. While waiting the First Officer briefed our passenger and I submitted a write-up to Maintenance via phone. The ACP called back and said that they thought I may have introduced excess fuel into the engine when I put the throttle back into idle while it was shutting down which could have caused the vibration so they asked me to motor the engine for a good thirty seconds and then try a restart and call back with results. I motored the engine for thirty five seconds and restarted. The restart was normal but the vibration was still there so I shut it down immediately.
The engine did not fail.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.
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