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Guest Ian_Riddell

Thrust Reduction Height

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Is the Thrust Reduction Height setting on the Takeoff Ref page active in PMDG? I set it for 3000', but the appearance of "CLB" on the Engine Display (above the N1 indications) didn't seem to appear until about 3500' (3400' above the airport, KSFO). I didn't have VNAV engaged, but the Bulfer Manual says that this is not necessary. Are there any other prerequisites?Thanks.Cheers.Ian.

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Ian,Conditions are (straight out of the code) :- phase of flight is takeoff (was on ground with speed > 80 knots)- AGL reported by MSFS/FSUIPC is >= to set thrust reduction alt- current thrust lim is TO or TO-1 or TO-2When those conditions are met, thurst lim will go to armed climbed thrust lim...VNAV is not necessary, as you mention.Bizarre... Did you pause the sim, go to / out of 3D, or set any menu items while initially climbing ? This *could* set the sim in a sort of limbo state where state info *might* be incorrect ?anthonyAnthony MertonPrecision Manuals Developmenthttp://www.precisionmanuals.com

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"Bizarre... Did you pause the sim, go to / out of 3D, or set any menu items while initially climbing ? This *could* set the sim in a sort of limbo state where state info *might* be incorrect ?"Hmmm... That may have been the problem, Anthony. I noticed on one climbout that when I paused to get a screenshot, after summoning the CDU and flipping through a few pages (but not changing any values), the TO annunciation changed to CON !Anyway, I'll give it a few more tries later on today.Thanks for the response :-)Cheers.Ian.

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"Conditions are (straight out of the code) :- phase of flight is takeoff (was on ground with speed > 80 knots)- AGL reported by MSFS/FSUIPC is >= to set thrust reduction alt- current thrust lim is TO or TO-1 or TO-2When those conditions are met, thurst lim will go to armed climbed thrust lim...VNAV is not necessary, as you mention."By VNAV not necessary, Anthony, do you mean VNAV engagement, or VNAV engagement and arming... or neither. I haven't yet figured out how the NG sets the thrust mode.What I know, so far....Thr Lim Mode annunciation is determined by FMC and position of N1 Set Control knob (under glareshield).The modes are...TOR-TOCLBR-CLBCRZCONGA- - - (no computed data)On a 737NG what will cause "CLB" to appear? I noticed that when I did a TOGA takeoff in PMDG, not engaging the A/P or touching any buttons on the MCP, the thrust mode changed to CLB at something like 5700', but I'm not sure why. On the 747-400, I believe the thrust mode will not change to CLB in this situation (contrary to the programming of some sims).I suppose manual selection of mode through the CDU Thr Lim page will cause a change to CLB also (overriding the current mode)?Will pitch mode selections like MCP SPD, V/S and LVL CHG cause a change to "CLB" (and if so, before Thr Red Height?).... On the 747-400, I seem to recall that some A/P pitch modes used the existing thrust limit (TOGA) in initial climb and climb, but I can't recall if they changed if they were below the Thr Red Height/Flaps 5 trigger point.The 767 seems to force a change to "CLB" with an A/P pitch mode change (if currently in TO mode).Anyway, as always, I stand to be corrected :-) There just aren't any definitive books on this subject... You have to look at half a dozen and then see if they all fit together.Cheers.Ian.

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Going off of memory Ian, I know at 800' in TO mode the AT goes to ARM. At flap retraction altitude you push N1 which sets climb thrust and shows CLB on the TMD and reference N1 bugs. Will have to check into other modes...[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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Ah no, that's something else : engine protection. After 5 minutes of TO thrust, thrust lim will automatically revert to CON to avoid burning the engines.anthonyAnthony MertonPrecision Manuals Developmenthttp://www.precisionmanuals.com

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>By VNAV not necessary, Anthony, do you mean VNAV engagement,>or VNAV engagement and arming... or neither. I haven't yet>figured out how the NG sets the thrust mode.Whatever the state of VNAV : off, armed, engaged.>On a 737NG what will cause "CLB" to appear? I noticed that>when I did a TOGA takeoff in PMDG, not engaging the A/P or>touching any buttons on the MCP, the thrust mode changed to>CLB at something like 5700', but I'm not sure why.Thrust reduction altitude reached.Other ways of going to armed climb thrust :- if you change TOGA to another pitch mode- if you press the MCP N1 button when AT announciator announces ARM- if you change the thrustlim with the CDU N1 LIM pageand... you'll go to MAX CON after 5 minutes of TO thurst, for engine protection.cheersanthonyOn the>747-400, I believe the thrust mode will not change to CLB in>this situation (contrary to the programming of some sims).>>I suppose manual selection of mode through the CDU Thr Lim>page will cause a change to CLB also (overriding the current>mode)?>>Will pitch mode selections like MCP SPD, V/S and LVL CHG cause>a change to "CLB" (and if so, before Thr Red Height?).... On>the 747-400, I seem to recall that some A/P pitch modes used>the existing thrust limit (TOGA) in initial climb and climb,>but I can't recall if they changed if they were below the Thr>Red Height/Flaps 5 trigger point.>>The 767 seems to force a change to "CLB" with an A/P pitch>mode change (if currently in TO mode).>>Anyway, as always, I stand to be corrected :-) There just>aren't any definitive books on this subject... You have to>look at half a dozen and then see if they all fit together.>>Cheers.>Ian.Anthony MertonPrecision Manuals Developmenthttp://www.precisionmanuals.com

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There are a few customer options in this area Ian. Some include: (Option - Without automatic thrust reduction after takeoff) * automatic thrust reduction to climb power occures when VNAV, ALT ACQ or ALT HOLD is engaged. Until 2 1/2 minutes after liftoff, automatic thrust reduction is inhibited when engaging LVL CHG or V/S modes (Option - Automatic thrust reduction after takeoff, FMC update 10.1 and later) * automatic reduction to climb thrust occures upon reaching the selected thrust reduction altitude which is shown on the FMC CDU TAKEOFF REF page 2/2 during preflight, or when the airplane levels off in ALT HOLD or VNAV PTH. Pilot entries can be made to override the default vaule. Allowable entries are 800 feet to 9999 feet... [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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"Ah no, that's something else : engine protection. After 5 minutes of TO thrust, thrust lim will automatically revert to CON to avoid burning the engines."Ah...so. Interesting. Usually it's up to the pilots to do this! BTW, I've noticed I have no trouble at all redlining the N1's on takeoff/climbout when I'm manually controlling the throttles. I thought the EEC's would have kept the N1's in check? I might need one of the engine boffins to explain to me how, with the EEC's constantly updating the engines' datums (Idle, Max Climb, Max Takeoff/Go-Around and Maximum Certified Thrust) based on Airplane Model, Engine Thrust Rating, Ambient Static Air Pressure and Mach Number, that the engines could possibly exceed their N1 limits.Also, I've noticed that the N1 command cursor on the engine display takes a while to catch up with my joystick throttle lever input (or is it just me again?) :-) Is this due to sim instrument speed updating or something else? (I understand why the actual (sensed) N1 value takes a while to catch up with the command (i.e because jet engine can be slow to accelerate to the commanded thrust), but not why the simple command cursor takes so long.Anyway, thanks again.Cheers.Ian.

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Thanks, guys.... Sounds like I need to get some decent AOMs :-)Cheers.Ian.

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>Also, I've noticed that the N1 command cursor on the engine>display takes a while to catch up with my joystick throttle>lever inputYes, this was one of the first things I noticed Ian! These handy cursors should move immediately to a value of N1 predicted by the throttle position.One for the list PMDG?

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