Date: 201811
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Weather elements / visibility: Snow; Rain; Icing; 9
Light: Night
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Takeoff / Launch; Parked
Aircraft component: Turbine Engine
Reporter organization: Air Carrier
Reporter function: Lead Technician; Inspector
Reporter qualification: Maintenance Airframe; Maintenance Inspection Authority; Maintenance Powerplant
Human factors: Communication Breakdown
Second reporter function: Technician
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter FOD
Detector: Person Flight Crew; Person Maintenance
When detected: In-flight
Result: Aircraft Aircraft Damaged; Flight Crew Overcame Equipment Problem; General Maintenance Action
Contributing factors: Manuals; Weather; Procedure; Human Factors
Primary problem: Human Factors

Narrative: MX was finishing up an inspection on Aircraft X. After the inspection was complete and I was finished auditing the inspection package; I received a phone call that our aircraft had been 'booked' for a revenue trip. I called for a fuel truck to upload 50K LBS of fuel onto Aircraft X and then went outside to wait for the fuel truck.A FBO worker (who supplies our fuel) showed up to take a metro-liner back down to the FBO; so I asked him when a fuel truck would be down to fuel Aircraft X. He stated that he was backed up right now; but that he would be down in a bit. He then asked if Aircraft X would need de-iced. I told him yes; to please de-ice the wings and tail. He then asked if he should de-ice the engine inlets too and I replied 'yes' a second time.I then went up a flight of stairs into the cockpit to make sure all of the avionics equipment was turned on and warming up as a revenue trip had been booked. When I was exiting the cockpit; but still at the top of the set of stairs; [personnel] in Operations texted me and asked if Aircraft X needed de-iced before it departed. I responded 'YES' and sent 2 pictures of Aircraft X's left wing; which has snow on it. [The Ops personnel] then responded 'Okay; thanks.'I then went inside to sign off the inspection and in the Airworthiness section on the same log page. After that paperwork was completed; I left work and went home. At approximately XA AM the next morning; I received a text from Chief Flight Engineer that the on-call weekend mechanic should go into work and look at the engines for possible FOD. I instructed the mechanic to do just that and he found the Number 1 engine with FOD to the C1 and C2 disk blades. When I received this news I asked the Chief Flight Engineer if the flight crew had de-iced Aircraft X after I left but prior to departure. He stated that the flight crew did not de-ice. He was with the aircraft all day and witnessed it takeoff so he would know.I'm not certain if I violated any FARs by signing off the inspection before the aircraft was de-iced but I wanted to document this in case I had and ice from the aircraft caused the damage to the Number 1 engine. The Number 1 engine is being replaced at this time and we hope to have the aircraft back in service safely within a few days. I have no idea why the flight crew canceled my request to de-ice Aircraft X; but I wish they hadn't.


Second narrative: The Aircraft was sitting in freezing rain for about 2 days on the ramp. The Aircraft was held for an inspection that are due every six calendar months. There was information given and received multiple times for De-ice from dispatch to the on duty flight crew; which being said the chief pilot is responsible for ensuring the aircraft is airworthy before takeoff. I was the mechanic on duty I was here until the plane departed and asked multiple times if they were going to be de-iced. The response I received from the Flight Crew was no; and this was the response multiple times of me asking. I asked again right before departure and Flight Crew said no; but can you come out with a ladder and a broom to remove some snow/ice on the wings and I said OK; With this being said and everyone on the active flight crew and off duty flight crew had been informed they needed de-ice and confirmed their message. I have not been trained to detect aircraft icing properly; meanwhile both the on and off duty flight crew have been trained properly. The active flight crew then proceeded to taxi; then on rotation on takeoff I see three small wisps of flames come from the aft of the aircraft engines and me and two others watch the full taxi and takeoff at the same time; off duty flight crew [is] with me and I express to them did you guys see the flames as well and they say no and they remark they 'kinda heard a weird noise' and I say should we call to have them turn around using our radio by contacting ATC and they say no after the look on their phone using Flight aware and then stating 'they didn't turn around so it must be fine' and I said are you sure and they say yes we will see what happens when they return and I said OK I guess; this being said I have no experience in contacting and using ATC; I have only been in aviation for a few years vs their 40+ if not more years of experience being pilots and other roles in aviation.


Synopsis: Two air carrier Technicians and flight crew reported engine damage caused by possible ice FOD during takeoff.  Reportedly; the aircraft had been sitting in freezing rain for two days and was not de-iced prior to takeoff.