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Guest topley

Sound effects during approach

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Having flown the -700 for several months, I invested in the 800/900 upgrade last weekend when the updates were released. I've noticed some interesting sound effects that start at some point during the approach which I'm sure weren't there in the -700. It sounds something like somebody scrunching paper or eating crisps. It lasts only for a couple of seconds and I can't correlate it to anything I'm doing with the controls. I thought it might be related to inadvertently letting the airspeed drop below VREF, but further experiments have convinced me that this is not the case. It's also not related to flap deployment, and I'm pretty sure the 1st officer is not eating crisps. Does anybody have any idea what this sound represents?Kim TopleyBAW310

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Probably the speed trim motor working! Apparently it is very noisy.Hope it helps,

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> Probably the speed trim motor working! Apparently it is very noisy.Thanks for the info. I'm familiar with pitch and rudder trim, but I've never heard of the speed trim motor before. What does it do and what am I doing to bring it to life?Kim TopleyBAW 310

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The autoplot is probably retriming the elevator during the approach. It's easy to identify the sound. On ther ground or when hand flying, hit the elevator trip up and down. You should hear the same sound.

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I know the sound you're talking about and wondered the same thing. I initially thought it was a bug with my sound card. Then I bought one of the "Just Planes" videos that featured the 737-700. The footage was all in the cockpit. As I was watching them take-off, I all of a sudden heard the EXACT same sound. At that point, I knew that PMDG had modelled even the sound effects as well. I still don't know what it is, but it sounds like it's the trim motor. The point of my response, though, is that the sound is expected and is exactly as it sounds in the real aircraft.Jay

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What you are hearing is the Bias Trim that happens abt 400 RA, this occurs with a Dual Autoland... Best Wishes,[h4]Randy J. Smith[/h4][h3]P M D G's 747-400[/h3][h4]coming to a runway near you[/h4][/font color]Caution! Not a real pilot, but do play one on TV ;-)AMD 64 3200+ | ASUS KV8 DELUXE | GFORCE 5700 ULTRA @535/1000 | Maxtor 6Y080M0 SATA 80 GIG | 512 DDR 400 | Windows Xp Pro | Windows Xp Pro 64 |

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"The autoplot is probably retriming the elevator during the approach. It's easy to identify the sound."I don't think there is a noise associated with 737NG elevator trimming??? Unless you have trapped a rattlesnake between the elevator and the elevator trim tab when you push/pull on the control column :(Perhaps you meant to say Autoland Bias Stabilizer Trimming? (or Stabilizer trimming in general?) ;-)Cheers.Ian.

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Just completed a flight EGKK to EIDW, paying attention to the sounds during approach. You are correct - I get this noise when I adjust the pitch trim to keep the aircraft on the glideslope. I never fly the aircraft in autoland and during the 10-mile final approach, I must have heard this noise maybe half a dozen times. It's made me very aware of when I retrim, which I must have been doing without thinking about it in the past, since I hadn't made the connection between that and the sounds until it was pointed out to me here! Do real-world NG pilots flying a manual approach change the trim that often, or is my flying technique a little unusual? :)

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Don't say that, Surely It's more likely to be the F/O wrapping up the remains of the cheesetray and cramming as much as possible into his briefcase - while the skipper has his hands full.Chris.

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I trim the aircraft constantly on approach when flying a Cessna or Piper RA. On approach I like to adjust the elevator trim so I have to pull back ever so slightly on the yoke to maintain my approach speed. When I flew the 767-400 Sim at an Airline Training Center a couple of years ago, I also used the trim ( mounted on the Yoke) constantly to maintain my airspeed and keep the pressure necessary on the yoke to a minimum. If you were out of trim on that Sim, you really had to apply alot of force to the yoke to change the pitch. I do the same thing with my PMDG and CH Yoke which when the PMDG is out of trim actually is a little bit like the RA in that you have to pull or push the yoke against the yoke springs in order to maintain your desired pitch. When I re-trim I get that "ratcheting" type of noise which is apparently the elevator pitch trim sound. The first time I heard that sound was on the DC3 aircraft in FS9. I think that is what the PMDG is using for the "trim" sound. When I use APP, I hear the aircraft constantly retrimming itself when I reduce the airspeed to approach speed. By the way, this is the sound that disappears from time to time when loading a flight and can be recalled simply by reselecting the PMDG aircraft you want to fly in the FS9 "Select Aircraft" menu.

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>When I flew the 767-400 Sim at an Airline Training Center a>couple of years ago, I also used the trim ( mounted on the>Yoke) constantly to maintain my airspeed and keep the pressure>necessary on the yoke to a minimum. If you were out of trim on>that Sim, you really had to apply alot of force to the yoke to>change the pitch. >Is the trim on the yoke in all the Boeing aircraft? I was in the747-400 simulator at Heathrow a couple of years ago and chose notto use the trim on approach because I would have had to lean overto reach it. On my joystick, it's convenient because the button isright there in easy reach. I wasn't told at the time that there wasan easier way to change the trim in the "real" aircraft and, as you say, some force was needed to make pitch adjustments without it.Kim TopleyBAW310

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Among the very loud GPWS annoucements, the trim sound on approach is another one that makes me jump out of my seat when I hear it because I'm so focused on the approach.

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"Is the trim on the yoke in all the Boeing aircraft? I was in the747-400 simulator at Heathrow a couple of years ago and chose notto use the trim on approach because I would have had to lean overto reach it."The trim switches are found on the yokes on all Boeings, Kim. The switches you refer to close to the thrust levers were probably the Alternate Trim switches... These are used if the yoke and autotrimming systems are inoperative.Cheers.Ian.

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Hi Jay,How did you like the video? I'm now looking for a 737 video myself. I'm particularly interested in the cockpit noise. I did spent most of my flying fine-tuning my PIC767 sounds (noise levels, engines vs wind, wtc ;) ) and now I'm on a new plane and I'm getting back to that sound tweaking again :)It'd be nice to have some footage to match the sound to!

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