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avjones

Pmdg 747 Fs9 Autopilot Problem

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I purchased the PMDG 747 two weeks ago and everything has been working fine up till now. The last three flights I've encountered an autopilot problem, as an example:I will use FSBuild for my flight, start the engines and set up my FMC as required. Set my Vref in the FMC, turn A/T on, F/D on, Altitude and speed (250 knots). As the vref speed are called out I rotate the aicraft as I climb I press the SPD button on the console and nothing happens, I press the V/S button and it light up. The SPD then lights up, then I press the CMD button. The CMD button will not lite up, after several clicks of the button it fianlly lites, when that happen the rate of climb which was set at 1500fpm increases to 4000fpm or more, even though the V/S is set at 1500fpm.Also my speed is slowing down, that I expect, I check the FMC and cannot find any possible reason for the V/S not to control the rate of climb. I have to DISENGAGED the A/P and re-engage it to restart the SPD and V/S button. IF I immediately click the L NAV and V NAV after departure the rate of climb is normal. I rather control by aircraft lateral and vertically unitl I'm on course for the L NAV and V NAV is needed. I have completely search this forum and others and cannot find anyone with this problem all though I feel like somebody has in the past.Alfred JonesVP-26 Patrol Squadron

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There have been a couple of threads in the past discussing V/S during initial climb; in summary, this is not a recommended practice. Airspeed and pitch should be primary. The normal method is to enable VNAV/LNAV before takeoff then activate A/P at 400 ft AGL. The A/P will manage the climb at V2+10 until acceleration height then the target IAS (30 REF + 100) until the transition altitude. See 9-9 in the manual if you want to try hand flying this segment of flight.

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There have been a couple of threads in the past discussing V/S during initial climb; in summary, this is not a recommended practice. Airspeed and pitch should be primary. The normal method is to enable VNAV/LNAV before takeoff then activate A/P at 400 ft AGL. The A/P will manage the climb at V2+10 until acceleration height then the target IAS (30 REF + 100) until the transition altitude. See 9-9 in the manual if you want to try hand flying this segment of flight.
that i have never done before enable the VNAV and LNAV before takeoff, i will try this next time. thanks for the info

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Set the Vnav active. Lnav or heading doesn't matter,You're pushing it too late!At takeoff when your spooling up the engines, push the hidden speed button on the panel that in real life is on the yoke. Do it before the engines reach 50% or 75% (I forget) and the speed will activate for takeoff.Otherwise you'll have to activate it later on in the air.(An Amazing Sim Aircraft!!!)Mike

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Do it before the engines reach 50% or 75% (I forget) and the speed will activate for takeoff.
I think it's more like 15%......ooops

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I think it's more like 15%......ooops
Advance throttles to N1=70% as per the manual.Check EGT and N1 are stable.Call out "stabilized" and then "takeoff".Push the TOGA button and start the stopwatch.At 80 kts call out "eighty knots", confirm and call out "checked".Look for THR HLD in the FMA and crosscheck it with N1 value.Call out "power is set" and "I have control".At V1 "Vee one" and hands off the levers. (Lufthansa pilots say "go")At Vr "rotate"...etc etc

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I think in general you have a few ideas of 744 operations that are not correct. Firstly I would not setup the MCP with 250 knots on the bug, I've never initial V/S at the early stages of the climb, and as for VNAV and LNAV, those are on before I even start my engines at the gate.My procedure is as follows:Cockpit safety inspectionStart APU and get power establishedPre-flight prep - FMC, flight plan, cost indexes, performance data, setup and determine de-rates and take off data, etc... at the end of pre-flight you should be able to engage the flight directors and switch on VNAV and LNAV as armed modes for pitch and roll, the active modes will be TO/GA TO/GA.. Obviously no thrust mode at the gate! A/T switch remains OFF. MCP would have my V2 speed entered.. not V2+10 or V2 + 5... but V2.. If I want to maintain a higher speed during my initial climb out I can do this myself without any issues..Engine start.. push back, prime hydraulics and fuel pumps, start engines.. then post start items and checks... APU off etc... RECALL.. etc..While waiting for taxi, I set flaps to desired for takeoff and as I begin my taxi and approach the runway.. I will turn on CONT IGNITION as appropriate.While I line up, VNAV and LNAV are still armed modes.. active modes are TO/GA TO/GA... upon crossing the threshold and lining up I will throw the A/T switch to ARM.Once lined up.. N1 to 70% ensure stable engines.. and roll is straight.. if it is.. TO/GA on thrust levers.. throttle advances to takeoff thrust.. THR REF as thrust mode.. then HOLD when it stablises at the thrust setting.. I can now manually control throttles at this point (common misconception, in HOLD you can move the thrust levers manually and adjust as required). Thundering past 100 knots now... then V1.. hands off thrust levers.. I am now departing regardless of failures.. VR.. lift the nose up carefully to about 3 degrees.. wait for positive rate.. V2.. postive rate of climb.. I give it a few seconds to get to about 50 - 100 feet AGL on the radar altimeter before retracting gear... and I pitch up to maintain V2+10 in the initial climb to get maximum perfomance... Throttle is still in HOLD... At accelleration height (1000 feet ish depending on preference).. I lower the nose and allow the speed to creep up by changing it on the MCP (if in manual control) and retract flaps on schedule.. making sure and confirming at flaps 5 the thrust rate changes to the appropriate and pre-programmed CLB thrust setting I have given... Once steady at this point I can switch on the A/P and the aircraft will follow my pre-determined route on the FMC (obviously I will follow this manually too if I need to make a turn before engaging the AP)... If I want to make the climb more comfortable for passengers.. and prevent ducking and diving (bad weather etc).. I may engage V/S and set a comfortable ascent rate, but this is later in the climb out, once the aircraft is clean and at initial climb speed.. and at all times I am monitoring the speed of the aircraft to ensure it is in safe and sensible limits.That is ROUGHLY.. what I do on departures.. I'd never V/S as you have discussed here, nor would I set 250 in the MCP initially.. I usually would engage the AP before acceleration height so VNAV is the active pitch mode, the speed window will blank at this point and the FMC will manage the speed, automatically increasing speed at my pre-determined acceleration height.. it will also take into account current flap position.. (clever eh?)My advice to you would be, take a look in the manual and perhaps a look at some of the DVD material out there, you'll see how to handle takeoffs much better, once you have your process sorted all your problems will just vanish.CheersCraig

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There is one other thing I will mention about the initial climb phases and the modes on the PFD FMA (Flight Mode Annunciator - shows the modes of thrust / roll / and pitch). If your VNAV and LNAV are armed modes before takeoff, during the initial climb, those modes will automatically become the active modes on the FMA on the PFD. As a result your flight director will be showing you the correct course of action with regards to your climb rates, turns etc based on the inputs from the FMC. What do I mean?.. Well initially you will have THR REF / TO/GA / TO/GA on your FMA.. then you'll see HOLD / TO/GA / TO/GA on your FMA, this means that the autothrottle has met the thrust demand for takeoff and the throttles can be manually controlled if necessary, this is in case you need to abort (retard the throttles) or perhaps slightly reconfigure for some other reason. This happens at about 80knots into the roll, that's not a ridgid speed, but approximate, the mode changes from THR REF to HOLD once the required thrust has been reached.You've taken off now, and are climbing, you've pitched up to maintain V2+10 in your climbout now.. and the aircraft is climbing happily with gear being retracted. Once you pass the altitude restrictions on the ROLL and PITCH modes for LNAV and VNAV, they will revert from being the 'armed' modes, to being the 'active' modes. The reason why LNAV and VNAV are NOT active on the ground, is that there are altitude restrictions on their activation, VNAV will not engage until you are 400 feet AGL (above ground level) that is, that your RADIO (I think I wrote radar above... typing before thinking.. oops.. my bad) altimeter is reading 400 feet+.. I think LNAV won't engage till about 100 feet AGL too but I am not totally sure of that one.. ANYWAY.. my point is.. the reason it is NOT the active mode at the gate even though you prime it, is that the system looks at the altitude, sees 0 and thinks 'aahhh.. not above 400 feet, I'll arm VNAV and park it till I am'...So imagine your climbout now... just lifting off.... HOLD / TO/GA / TO/GA.... passing 100... HOLD / LNAV / TO/GA... as a result the flight director is now showing LNAV active, we are now getting roll commands from the FMC.. However A/P is NOT ENGAGED.. you are still in command!.. But the flight director roll indicator will follow your programmed route. TO/GA pitch mode, a steady climbout pitch.. and HOLDing thrust (Pilot In Command but takeoff power set)... as you pass 400... VNAV will engage (VNAV SPD).. You are now in a position where the aircraft is now showing you pitch and roll commands from the FMC which will correspond to your inputted route and performance data..... I engage A/P here... Speed window blanks.. and Aircraft follows the commanded pitch and roll from the FMC..I hope that extra information helps.. CheersCraig

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This is a super simple tutorial by Jared "Smitty" Smith that really helped me out to understand operating the PMDG 747:http://smithplanet.com/fs2004/pmdg/After this you should have no problems with normal operations of this aircraft.Mike

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