shake rattle rumble and roll..............not to worry.
Scarbagjack,
Los Angeles is a busy place, four runways two for departure and two for arrivals. There are airplanes coming in from all four cardinal directions. From the West the Pacific traffic from the Hawaiian Islands, New Zealand and Australia. From the north domestic traffic from San Francisco, central California, the Pacific Northwest and Alaska/Asia. The south brings in our “compadres” from Central and South America as well as the traffic from Mexico. From the East come the arrivals from central/eastern Canada, Europe and the Eastern Seaboard of the U.S.A.
From LAX dozens of carriers and freight operators launch everything from piston-powered twins to the newest 380s going to virtually every corner of the globe. In close proximity to LAX are several other major airports (Long Beach, Orange County, Ontario and Burbank). Throw into this mix a healthy number of Business/Corporate jets and many general aviation airplanes and you have congested airspace.
A single flight arriving into Los Angeles does not have the luxury of having an uninterrupted descent (unless you happen to be some VIP head of state getting special treatment). Often air traffic controllers change the parameters by assigning a different speed or altitude several times during a descent. Or they are concerned about maintaining the required separation between airplanes they are controlling. Sometimes they will ask the pilots to expedite their descents. And then there are times I do not calculate correctly my rate of descent and need to take additional action to get my airplane where it is supposed to be in the descent.
One of the tools at my disposal are the “speed brakes”. The speed brakes are metal panels on the topside of the wings close to the body of the jet towards the back part of the wing. They are normally held close to the wing. However by using a lever I can direct hydraulic pressure out to the speed brakes and make them begin to stand up away from the wing and into the air passing over the wing. When I move the handle and extend the speed brakes it makes the wing less efficient in producing lift and at the same time causes the air passing over the wing to become much more turbulent. You will hear a rumble and feel the shake as the air passing over the wing is disturbed by the extended speed brake.
The faster I am flying the more you will hear and feel the effect of the speed brakes. Their extension adds much “drag”, resulting in a greater rate of descent.
There is nothing wrong with your wing, pilot or flight. The manufacturer built in this capacity and gave your pilot the speed brakes as an additional tool to be used to manage their descent rate and speed. There is no reason to become anxious when you notice the speed brakes being deployed, your pilot has decided to increase their rate of descent and/or reduce the forward airspeed of your jet to get your jet to a certain point in the air at an assigned altitude and airspeed.
When your pilots add power to the engines to begin their takeoff roll you also have a much-increased noise level and vibration. That probably does not concern you as it is to be expected. A similar thing is happening on descent the noise and vibration is increasing, but this time it is the shape of the wing causing the rumbling rather than the amount of power being demanded of the engines. There is no reason for you to be concerned at all. Because you understand what is going on you can now sit back relax and enjoy the experience. Once your pilot has achieved what they needed to do they will once again “stow” the speed brake and you will notice both the vibration and noise level decrease.
Respectfully,
Northbeach
Last edited by Northbeach; 1st Apr 2010 at 16:59.