Well lets start with a Tristar story.
A Gulf Air Tristar hit a flock off birds on take off at Karachi early one morning and abandoned and returned to the gate. The fan blades were bent. I was in Bahrain at main base and four of us flew out to KHI
on the next flight with boxes of fan blades. The flight took ages and stopped at least twicw and we arrived there at sunset. The pax had been in the terminal for 12hours!
We did two things. Two of us replaced the fan blades, na dthe other two prepared the aircraft for a two engine ferry, in case there was more damage. We had to boroscope all 3 engines and do other checks , and had just started when the flight crew turned up. Will you be long? Yes. Anyway we finally got every thing ready, fan blades replaced and aircraft prepped for a ferry, (with the blades fitted as there was no damage) when the passengers appeared! We thought we were going out for a vibration run, but the crew and the local management had decided it wasn't necessary. So the plane filled up with the pax who had been in the terminal all day, and we got on board. I was in a cabin crew seat by R1 as the flight was packed. I got a beer and was ready to open it as we left the runway. At 100kts we abandoned as the same engine was still vibrating! The pax went beserk, and I was not too pleased as the beer was still unopened. We returned to the ramp and offloaded everything, all pax containers catering water cabin crew, in fact anything that moved, and most of the fuel. Then started up the two good engines and taxied out again. (Glad I wasn't in the terminal with the SLF).
Then a two engine take off. It was now past midnight, and I started at 0600. The flight engineer explained that if one of our two engines failed in the first 10 minutes we were going down, so I opened mu beer and had a drink. We had Nbr 3 failed so after lining up on the runway they opened up Nbr 1 to T/O and waited a minute, all OK
so back to idle then opened up Nbr 2 to about 90%, (It was a -524 so would not go to 100% static!) and a minute later let the brakes off. Nbr 1 was accelerated until it produced 100% ay 100kts and off we went. Home to BAH
at about 0400.
Well the outcome of the whole story is that we were conned.
The set of fan blades were numbered 1-33, and that is how we fitted them. What they didn't tell us is that we should have had a sheet of paper which said..put nbr 1 blade in hole 22, nbr 2 in hole 7 etc., which was written on the Rolls test bed when they finished balancing it.