If I had to guess, the sound is a reminder that the trim IS in motion. It's probably mechanically generated since the system is a holdover from earlier times. From what I've read, some planes without the trim wheel have some sort of tone to let you know something's happening...others don't.

In the real aircraft the whirring noise is the sound of the electric motor driving the trim wheel like crazy and the clicking is the motor control relays operating as the trim switches are moved. Because it's all mechanical there's no need for a reminder. Most modern aircraft, without trim motors in the pedestal, have trim in motion noise makers. For example, the 747's noise maker is simply a thin piece of plastic flicking against a toothed wheel which makes a clicking noise. The 737 stabiliser trim is like it is because it has to be highly geared to enable the pilot to move it manually. Many trim wheel turns for one unit of stab trim movement. That's why the wheel moves at such a high speed when it's being driven electrically. Kevin Hall

Yea, I kind of figured that was the case in order to gain mechanical advantage with the system. Personally, I think it adds some character to the plane.

It took me over a year to get the trim wheels spinning correctly in my home cockpit.They are made from hard plastic but are on a real 737 TQ. I love the trim wheels spinning. They are so.........................737 !!

I wonder if some hot dog ketchup or mustard falls into the wheel while spinning what's the procedure to clean it wisely.......

I wonder if some hot dog ketchup or mustard falls into the wheel while spinning what's the procedure to clean it wisely.......

I'm sure there are "untold stories" of trim wheel fun out there...

I'm sure there are "untold stories" of trim wheel fun out there...

Yes I agree. some real pilot could chime in and tell us the real truth. I am under the impression the many hot dogs themselves could be involved too.

I was an Intruder and Hornet mech in the USMC and I know we had our fair share of fun (run out from underneath a hangar queen jet, going out for a test flight, with a towel stained red with hyd fluid, look at the pilot, shrug shoulders, pause a moment, then give a thumbs up, heh)...and I know the pilots did as well. I'm sure hilarity ensued with that thing at some point, lol.

The Horizontal stabilizer is controlled by a electrical stab trim actuator, That is installed on the jackscrew gearbox. This gearbox is installed in the tail section of the A/C in front of the horizontal stabilizer. The stab trim actuator can be controlled by the Autopilot or manually with the trim switchesThe jackscrew gearbox can also be manually operated by hand, The gearbox is mechanically linked with control cables that is attached to a cable drum located in the nose section of the A/C underneath the pedestal, the cable drum is than connected with a chain to the trim wheel's in the flightdeck. The trim wheel noise you hear is the turning chain when you are trimming the horizontal stabilizer. When you are riding a bicycle you hear the same noise.

The Horizontal stabilizer is controlled by a electrical stab trim actuator, That is installed on the jackscrew gearbox. This gearbox is installed in the tail section of the A/C in front of the horizontal stabilizer. The stab trim actuator can be controlled by the Autopilot or manually with the trim switchesThe jackscrew gearbox can also be manually operated by hand, The gearbox is mechanically linked with control cables that is attached to a cable drum located in the nose section of the A/C underneath the pedestal, the cable drum is than connected with a chain to the trim wheel's in the flightdeck. The trim wheel noise you hear is the turning chain when you are trimming the horizontal stabilizer. When you are riding a bicycle you hear the same noise.

'The Wright Flyer had one engine, why can't flying be that simple anymore?

'The Wright Flyer had one engine, why can't flying be that simple anymore?

Because the Wright Flyer didn't have a 2000+ miles range, ETOPS capability, and couldn't fit 150+ people sitting on their bellies inside, while flying at FL350 :)

The Horizontal stabilizer is controlled by a electrical stab trim actuator, That is installed on the jackscrew gearbox. This gearbox is installed in the tail section of the A/C in front of the horizontal stabilizer. The stab trim actuator can be controlled by the Autopilot or manually with the trim switchesThe jackscrew gearbox can also be manually operated by hand, The gearbox is mechanically linked with control cables that is attached to a cable drum located in the nose section of the A/C underneath the pedestal, the cable drum is than connected with a chain to the trim wheel's in the flightdeck. The trim wheel noise you hear is the turning chain when you are trimming the horizontal stabilizer. When you are riding a bicycle you hear the same noise.

Exactly And, on the real one, some cautions must be taken to ensure that the wheel handle is stored before using the electrical trim (expecially with flaps not up) because the handle can hit the pilot leg.

It's knee buster !!!. specially when the flaps are down.

Back to my original question (this wasn't a joke - I am really curious).Is it true that the 737 is the only Boeing in production that uses this trim wheel? I don't see it on the 767, 747, 777. If it is the only one - why?

Back to my original question (this wasn't a joke - I am really curious).Is it true that the 737 is the only Boeing in production that uses this trim wheel? I don't see it on the 767, 747, 777. If it is the only one - why?

Yes, the 737 is the last Boeing airframe still in production with this stab trim system. Kevin Hall

Back to my original question (this wasn't a joke - I am really curious).Is it true that the 737 is the only Boeing in production that uses this trim wheel? I don't see it on the 767, 747, 777. If it is the only one - why?

Why - the answer is money, of course. Boeing wants to keep as much tech on the plane the same so it can be a common type rating. If they monkey with too many things, the FAA will make airlines give more training. That's one of Boeing's selling points. Newer tech exists, but it's expensive to train pilots to use it. I thought a lot of the noise came from the handle getting knocked around.