What’s the significance of this video were you on board

Obviously….

According to an experienced pilot, the sound was,

“The thud occurs just after lift off. It is when the Body gear oleo that holds the undercarriage assembly extends fully to its stops as it unloads. Following this, the wheels are unloaded on their bearings and making a loud rumbling sound until the brakes are automatically applied during the retraction sequence to stop them completely. The cameraman is located almost over the body gear bay which is why it is so loud. The body gear lies behind the wing gear bay (which is located just ahead of the flaps) and it just extends straight down, with the attachment point just below the cabin floor.”