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Guest Ian_Riddell

"RAM DOOR FULL OPEN" (Minor) Anomalies

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This message wasn't intended to be a mini-tutorial, but... :-)I was just reading about the "RAM DOOR FULL OPEN" annunciator light in a 737-700 maintenance manual (-800/-900 ops slightly different).The Airconditioning "Packs" can use outside air to cool hot engine or APU bleed air for cabin air pressurization/passenger comfort. The hot engine/APU bleed air is cooled by feeding it through a kind of radiator known as a "Heat Exchanger". The cool outside air is blown over the heat exchanger (not actually mixed with the engine bleed air). The outside air is scooped up by one of two "Naca" scoops (one per Pack) and fed to the heat exchanger via a duct.http://members.ozemail.com.au/~b744er/737/RamAirInlet.JPGJust inside the entrance to this duct is a two-piece hinged door which is moved automatically (electrically) to control the flow of cold air into the duct. This door is known at the "Ram Air (Inlet) Door". On the ground, the Ram Air Door is always driven wide open automatically. After the aircraft takes off, but with the flaps still extended, the Ram Air Door closes a certain amount, but it won't close any more until the Trailing Edge (T/E) flaps are completely up. Even though the Ram Air Door has moved a certain amount towards the closed position after takeoff, the RAM DOOR FULL OPEN light remains illuminated (normal). All OK in PMDG so far.(Sidenote)The Left Pack Ram Air Door can fully close when the T/E flaps are up (as sensed by the "Flap Control Unit" in the Main Gear Well).The Right Pack Ram Air Door closes when a T/E flaps up signal is detected by the "Flap Slat Electronics Unit" (FSEU). T/E Flap position transmitters relay the position to the FSEU.However, PMDG logic appears to link the Ram Door to the Leading Edge Flaps rather than the trailing edge flaps (could someone confirm this for me please?). The light only goes out when the LE's are all the way up.If the light remains illuminated after the T/E flaps have retracted, this may be a sign of:1. an electrical problem of some description2. a blockage in the Ram Air system3. a dirty Heat Exchanger In flight with the T/E flaps up and the Pack on, a controller (small computer) monitors Aircon Pack discharge temperature. If too hot, this computer sends a signal to the ram air inlet door to open it wider. If too cold, it closes the door.If a Pack is shut down in flight, the associated Ram Air Door fully closes to improve aerodynamics. On the ground, if the Pack is shut down, the associated Ram Air Door remains open and the RAM DOOR FULL OPEN remains on. However, in PMDG the light appears to go out(?)There is a protective door/flap just in front of the Ram Air Door (in the NACA scoop) which helps stop debris entering the duct when the aircaft is on its takeoff run (Not modelled in PMDG). After takeoff, however, this folds flat, allowing the scoop to do its job properly.Hope this makes sense!Cheers.Ian.

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After years of reading your posts on the PS forum, can you even type a note that isn't a mini-tutorial? :-lolRay

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I always enjoy reading your posts but would love for you if possible at the end of your presentation *summarize* A: PROBLEM with 737NG currently- *Ram door lights are not displaying correctly*B: How the real 737NG works in this regard- *The real 737 Ram door lights are tied too...*C: Further suggestions for replicating this correctly (if possible) in FS.- *The lights could be tied this way...* ;) [h5]Best Wishes,Randy J. Smith [h4]P M D G 7 3 7 NG[/h4]http://img.villagephotos.com/p/2003-8/196432/mineimage.jpg [h3] Realism on the horizon [h5]AMD XP 2200 |MUNCHKIN 512 DDR RAM |ECS[/b ][i] K7S5A MB[/i] |GF2 MX 32 MEG and still runs GOOD!|WIN XP PRO |MITSUBISHI DIAMOND PLUS 91 19"[/h5]

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"I always enjoy reading your posts but would love for you if possible at the end of your presentation *summarize* "Point taken, Randy ;-)(Although at 4 in the morning with a bout of insomnia and a dose of flu, you tend to forget about these things :-lol)Cheers.Ian.

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Ian-I have to dig into my notes on the operation of the RAMAIR DOOR. There is some logic that was linked to flap position- and the squat switches- but I programmed that system so long ago I'll be durned if I can remember it... ;-)More info in a bit...

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I have a simplified schematic of the Left Ram Air system if you're interested, Rob.... However, I'm having trouble "driving" it. I can see how the system transitions from ground mode to flight (with flaps extended) to flight (flaps up), but I can't reverse the process (It seems to go from flight mode (flaps up) directly to ground mode). We may need some 737NG pilot input here (Need to ask him/her if the RAM DOOR FULL OPEN Light only reappears on touchdown).Cheers.Ian.

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Ian,While your digging, check to see if there isn't some kind of time delay associated with the doors opening after landing. I know some A/C close the doors on touchdown to prevent inducting water/Ice into the pack inlets on the rollout. RegardsPaul Gollnick :-coolTechnical Operations/Customer Operational SupportPrecision Manuals Development Groupwww.precisionmanuals.com

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It is very easy to simulate RDFO light:Flap not up = RDFO lightA/C on ground = RDFO light.With Ram door full open - the deflector door (prevent slush/gravel from nosewheels to enter) is deployed.There is no time delay on touch down - RDFO already at first flap selection during approach.Reason for RDFO with A/C on ground (regardless of flap pos):Turbofan activated for airflow through ram air system....By the way: Giving up the 737NG with FS2002 - But good news, installed FS2004 last week and the 737NG runs perfectly. Time to ask for reg key I guess?Too bad the navdatabase site is not working.eker

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"While your digging, check to see if there isn't some kind of time delay associated with the doors opening after landing. I know some A/C close the doors on touchdown to prevent inducting water/Ice into the pack inlets on the rollout."No mention of time delays I'm afraid, Paul. However, with a bit of sleuthing... and some serious soulsearching at airliners.net, I may have figured out what's going on.In this brilliant (probably the best I've ever seen) pic by Patrick Lutz... :-)http://www.airliners.net/open.file?id=297683... the Ram Door Full Open lights appear to be on for the approach. This makes me think that unless there was a huge problem with their aircraft, the approach Ram Door sequence is almost a mirror image of the takeoff sequence (even though the simplified Boeing schematic seems to disagree with this). Having the Ram Door Full Open light ON for the approach means that the Ram Air Door has already started moving towards the open position (so definitely no touchdown time delay here). Note here that the RAM DOOR FULL OPEN light is poorly named. It comes on when the Ram Air Door electric (wormdrive) actuator has already travelled about half its length (towards full open). This may or may not mean that the Ram Air Door is halfway open (as you have to consider non-linear movement of linkages).Looking at pics at airliners.net, you can compare the different configurations of the Ram Air Door and the easier-to-see protective flap just in front of the Ram Air Door (a.k.a. rhe Ram Air Deflector Door) in the Naca scoop/duct. The Deflector Door is mechanically linked to the Ram Air Door. When the Ram Air Door is about 1/3rd closed, the Deflector door is fully closed.In this pic of a 737 at rotation, you can clearly see the Deflector Door protecting the entrance to the Naca scoop/Ram Air Door (the aircraft is still in ground mode).http://www.airliners.net/open.file?id=324714In other shots taken seconds after lift off, you can see the Deflector Door stowed and the Ram Air Door partially closed.http://www.airliners.net/open.file?id=380883In approach shots, you can see the Ram Air Door partially open.http://www.airliners.net/open.file?id=402698In "rollout" shots you can see the Deflector door fully deployed (and, with a bit of imagination, the Ram Air Door fully open) :-)http://www.airliners.net/open.file?id=343706Clear as mud :-)Cheers.Ian. P.S. Looks like Eker has confirmed my findings :-) Welcome back, Eker!

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Clear as mud. :-)I would have to agree with Eker on how to best implement this into FS but I thought this was how we had decided to do it already. Will have to revisit. Thanks for the research GuysRegardsPaul Gollnick :-coolTechnical Operations/Customer Operational SupportPrecision Manuals Development Groupwww.precisionmanuals.com

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"However, PMDG logic appears to link the Ram Door to the Leading Edge Flaps rather than the trailing edge flaps (could someone confirm this for me please?). The light only goes out when the LE's are all the way up."Ooops..... Cancel that bug item! (The bug was in me :-roll ). The PMDG logic is ok... I forgot that the LE flaps deploy at the same time as the TE's on a 737 (unlike 747's, 767's, etc....where the T/E's don't start moving until later). Soorrrryyyy.Ian.

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Well as long as YOU sign off the write-up its o.k. by me :-)Had me wondering for a bit there, I thought I had checked that out :-lolRegardsPaul Gollnick :-coolTechnical Operations/Customer Operational SupportPrecision Manuals Development Groupwww.precisionmanuals.com

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