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JS41 - Just a couple of questions

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I am sure the answers are in the AOM if I look hard enough but in case anyone is feeling charitable:1. What does the APR arm switch do?2. When should one use prop sync and is it's effects modelled?3. When would you use the fuel enrich switch?Thats all for now.Thanks


Bill Miller

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Hi Bill, It's not that I'm not feeling "Charitable", but I just got the JS41 tonight/this morning, and haven't got the slightest clue.However, just to help with an easy trip to learning and finding easy answers fast. Open any of the PDF's, doesn't matter which. Then press "CTRL+Shift+F" on your keyboard.This will open an advanced find and you can tell it to search multiple pdf docs at once. It will list all of the finds in a nice easy to follow format giving you an excerpt from the sentence it was used in making finding these types of answers fairly fast.*This will work for the JS41 docs, but one thing to keep in mind is it will search all of the PDF's in the folder, so for manuals like the MD-11, you may want to copy them all into the same folder first and make life a little easier ;-)Hope this helps,


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Dan Prunier

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Thanks, I will try that and see if the answers lies somewhere in the AOM. If not, any advice would be gratefully received.Regards


Bill Miller

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APR is approach. Prop sync and fuel enrich are required only during abnormal procedures.

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The APR switch I think he means is the Automatic Performance Reserve, which to my knowledge (AOM doesn't cover it very well from what I have read) if armed (during takeoff) during a engine failure will give a slight performance increase to the remaining good engine.Prop Sync is used to reduce the irritating sound that can occur when the props are out of sync, considering the prop RPM is always so close for me I have never noticed if it is simulated.Fuel enrich is used during manual engine start, during normal auto start process this is done automatically.

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I'm sure I read that prop sync is turned on after setting climb power; then turned off before final approach. I believe that's considered normal procedures.Curt Branch

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Prop sync should be turned off before landing in case you need to push the throttles for go around, prop sync should only be used at a constant power setting. Changing power settings with prop sync on will eventually cause a prop sync failure. The out of sync throbbing (hetrodynning) is modeled in the JS41 but you need to move one throttle (not both) to sense it.


Dan Downs KCRP

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Hi Bill, I'd just like to add a little more detail on what other folks have said. As Jay said, APR is not really explained in the PMDG documentation, although the system does function, so it's excusable to ask :( 1 - APR, or Automatic Performance Reserve should be active for takeoff and landing ONLY, it also arms the Negative Torque Sensing (NTS), which is basically autofeather - No one really seems to have explained the latter point so far. APR senses if an engine flames out and automatically increases the available horsepower from the remaining live engine, using the fuel enrichment system. It will increase the torque from the engine to 113% of what was set, although this limited to the 100% red line. It will also raise the EGT limit by 40'c to prevent operation of the Torque and Temperature Limiter (TTL). For more details see page 45 of http://www.smartcockpit.com/pdf/plane/bae/...41/systems/0007As regards the NTS system, in the event of an engine flameout it senses that the propeller is windmilling (i.e. turning the engine) and will reduce hydraulic pressure in the propeller hub, allowing the propellers to move to a higher blade pitch and hence reduce drag. Even with NTS operation, it is still necessary to perform a manual feathering drill, as the propellers will begin to unfeather after a short period (when the windmilling engine begins turning the propeller again). The system is entirely mechanical and based around oil pressure. http://www.smartcockpit.com/pdf/plane/bae/...1/systems/0007/ it's discussed there on pages 8, 9 and 36 if you are interestedUse of APR requires a takeoff be conducted at full power, with all IECs and TTL operational. APR will not operate below 65% torque and 99% prop rpm, regardless of wherever it is armed or not - should an engine fail during landing and you need to go around, pushing the levers beyond 65% torque will activate APR. APR can only be used for a maximum of 10 minutes... unless you want serious problems with your remaining working engine! To reinforce the point, if the APR system is activated, it adds 300 hours to the engine run time and is logged by the IECs.2 - Prop Sync, or the Propeller Syncrophasing System, automatically matches the propeller's speeds and holds them, by using the propeller governor to subtly adjust the blade pitch. Before the system is armed, the props must be manually set to within .5% of each other. Once the system is active, it may take up to 30 seconds to fully match the rpm's, and they'll remain matched until the condition levers are manually moved. The purpose of it, as several have already stated, is to reduce unpleasant sounds Mr Downs described, by holding the props in the appropriate "phase relationship". Also as Mr Downs said, prop sync should be turned off before changing power settings, and ALWAYS OFF for takeoff and landing.3 - Fuel enrichment is used during a manual engine start, the purpose of it is to maintain EGT near 695'c during the start procedure, until 60% RPM. The Fuel Enrichment system is not energised until the manual start knob is placed in the IGNITE position, although I wouldn't advise you press the button before then. When 60% is selected, the system will be "de-energised", although again you should still press the FUEL ENRICH button to be sure. You will not need to use it during a normal start conducted with the IECs, as they automate this function for you.Chris (廖傑英)


ckyliu, proud supporter of ViaIntercity.com. i5 12400F, 32GB, GTX980, more in "About me" on my profile. 

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Guest BlueRidgeDx
As regards the NTS system, in the event of an engine flameout it senses that the propeller is windmilling (i.e. turning the engine) and will reduce hydraulic pressure in the propeller hub, allowing the propellers to move to a higher blade pitch and hence reduce drag. Even with NTS operation, it is still necessary to perform a manual feathering drill, as the propellers will begin to unfeather after a short period (when the windmilling engine begins turning the propeller again). The system is entirely mechanical and based around oil pressure. http://www.smartcockpit.com/pdf/plane/bae/...1/systems/0007/ it's discussed there on pages 8, 9 and 36 if you are interested
Chris,Just to clarify, if APR isn't armed, the prop will NTS cyclically as you describe until manually feathered. But if APR is armed, the Auto-Relight function will continuously attempt to relight the failed engine until RPM has decayed to either 40% or 45% (I can't remember which), then the Auto-Feather function will feather the prop without pilot intervention.

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Thanks Chris for the comprehensive explanation of prop sync and APR. Very interesting.Regards


Bill Miller

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Just to clarify, if APR isn't armed, the prop will NTS cyclically as you describe until manually feathered. But if APR is armed, the Auto-Relight function will continuously attempt to relight the failed engine until RPM has decayed to either 40% or 45% (I can't remember which), then the Auto-Feather function will feather the prop without pilot intervention.
Thanks for correcting me there, my memory is failing me! Indeed it says NTS and auto-feather are separate systems on the document I referenced, maybe I should refresh my memory in future before opening my trap lol.

ckyliu, proud supporter of ViaIntercity.com. i5 12400F, 32GB, GTX980, more in "About me" on my profile. 

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Please do not refrain from opening your "trap"... :( I learn a lot from these trap openings, and if there is a small error in one of the openings, then someone quickly tidies that up...I am so glad that1: You guys with the knowledge here share it, and2: The aircraft has the fidelity to be able to put that knowledge to some use here!Thanks everyone!Andrew

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Just to add that after some testing/playing around I've found the auto-relight doesn't appear to modelled (not that it would be much use in FS), although everything else does (APR, Autofeather, NTS etc), in fact the prop even NTS's cyclically if you fail to feather the prop when APR isn't active. The autofeathering is very swift however, the prop stops almost instantaneously.Additionally, the unfeathering action performed by the IECs during an in-air relight is not done either, to perform a restart you must unfeather the props yourself first (hover over the appropriate condition lever and ensure the tooltip does not read "FEATHER"), obviously you also need to ensure the condition lever is out of the CUT-OFF/feather gate, then you can press the appropriate START p/b on the overhead and the IEC will do the rest.


ckyliu, proud supporter of ViaIntercity.com. i5 12400F, 32GB, GTX980, more in "About me" on my profile. 

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Guest BlueRidgeDx

I was never able to induce a flameout in order to test the Auto-Relight function. I think the only way to do it is to use the FSX failure menu, and the only option present is "total engine failure" which, when set precludes restarting of the engines. Did you try another method? And the last time I checked it out (a few weeks ago) I confirmed that the automatic windmilling start wasn't working correctly either. Though I'm positive it was ok at some point during the Beta when I originally tested it. I have to admit, I don't get very many opportunities to fly the sim and when I do, I avoid failing things that make me divert.I'll be sure to revisit the issue when it's time for the planned update.EDIT:There was also another post about this a while back. Mostly the same information, but worth a look if there are any lingering questions:http://forums1.avsim.net/index.php?showtopic=261686

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