Hello , Dear Captain. You have had a very busy week! I love the take off, especially the sound of the engines! Also, very lovely scenery. Stay safe and bless you. 🌹💝🌹
More like a turbine blade "fluttering" or perhaps some ball bearings needing lubricant/replacing ? In any event the flight arrived safely or we would not have the video and it did not seem to impact the thrust/mass ratio during takeoff. On some Douglass (DC) flights the flap motors can sound like that.
Curious ... is that "grinding" vibration sound considered "normal" ? It obviously had no impact on thrust but a long trip with that noise would drive me crazy ! It might be something in the cabin rattling in response to a smaller engine vibration. It did reduce some after that flight gained altitude. I also didn't hear it on a BRU landing with similar equipment.
You hear it on takeoff and the beginning of climb (only if you are in front of the engine tho), and as you climb the air gets less thick and the sound is less loud, so basically you hear this in the first 20/45 minutes (depending on a lot of things) :)
The "roar" comes from the fan blades going trough the speed of sound. This occurs at a certain RPM (you can calculate it if you have the radius). The higher up you go the faster and the more air sound will be heard, thus decreasing the overall effect of the roar. In cruise you cannot really hear it.
