human
During takeoff, upon trailing edge flap retraction, the flap system locked out. The airplane landed at same airport. Subsequent investigation found Nut on No. 4 trailing edge flap transmission U-Joint had backed off causing the left hand inboard flap to skew and damage adjacent components. As stated in the message; The diverted flight was performed with large trim inputs, but control was not problematic. What was the cause of the problem?
gpt
--- Reasoning ---
1. Is the question multiple-choice question?
No
2. Is it implied multiple-choice question?
No
3. If two experts were independently asked the question, will the final answer be exactly the same?
Yes

--- Answer ---
grounded