Better engine vibrations when holding brakes

[nico87]

The engine vibrations whould be higher when the engine is at full power, on the ground, with aircraft stopped and brakes hold.

[Danita]

I experienced this a few days ago on an Aeromexico flight that had to start the no. 1 engine using pneumatics from the already running no. 2 engine because of an inoperative APU. They set the parking brakes and accelerated the no. 2 engine to a good measure. The aircraft was shaking like a cocktail mixer.