B744 "silent A/T disconnect"

[Guest The_Glideslope]

This is what I called the "Silent Auto-Throttle Disconnect"I started my flight in VHHH. All sytems were working fine and all speeds, restrictions, cost index, you name it I had it.Climbing to FL340, I discovered the airplane was loosing speed with no apparent reason.It also halted in 24000ft with not Vert Speed indication. Stabilized.I found it weird since MCP was properly programmed to FL340, LNAV and VNAV activated, AP on, F/D on, A/T arm also on. To my surprise I noticed the EICAS was indicating 90% N1 in CLB mode. I looked at how the levers in my GoFlight TQ6 were and noticed a pattern. I moved the throttle and I noticed it was responding to inputs, meaning the A/T din't kick in, or at least it "silently" shut off.But the VNAV was on. I only recovered Auto-Throttle mode by pressing FL CH and/or SPEED and press VNAV again.This has happened before and I always thought it was my operating error. But I bought Mike Ray's 747-400 Simulator Checkride, studied the AOM and couldn't find a flaw in my operation.I usually fly manually until T/C. When I do that I activate LNAV and VNAV with no problems until something which I am not aware, triggers this. I also tried to activate VNAV immediately after gear retraction, and the problem persists randomly.I also found this problem when I saved the flight and loaded it. I always need to make sure the A/T is on. So I move my levers and it's responding, so I press FL CH or SPEED and then VNAV Again like I said above.I also tried with another throttle system (Joystick slider and a CH throttle thingy) same results, hardly Goflight issue.Software Error? Operational Error?Thanks in advance.PS. Why didn't you include the later 744 panels? (engine Auto-start, etc)? Some of this panel's systems belongs in the earlier versions of the 744, still pleasant and very accurate, though...

[Mats_J 2]

Jon>I usually fly manually until T/C. When I do that I activate>LNAV and VNAV with no problems until something which I am not>aware, triggers this. I also tried to activate VNAV>immediately after gear retraction, and the problem persists>randomly.I don't know what caused your problem. But you need to keep track of the different autoflight modes in the flight mode annunciator (FMA) to detect these kinds of problems early. It is located at the top of the PFD. Three fields. Leftmost is speed, or A/T mode, centre one is vertical mode and rightmost tells you what lateral mode you're in. If speed mode field is empty you don't have any automated speed mode active. If you are in VNAV you should be able to reengage A/T mode by pushing the VNAV button.>I also found this problem when I saved the flight and loaded>it. I always need to make sure the A/T is on. So I move my>levers and it's responding, so I press FL CH or SPEED and then>VNAV Again like I said above.IIRC this is a known issue. Please check the FMA and reengage any A/T mode if necessary.Hope it helps,

[Prycon 1]

I have had this problem too, loosing speed during climb, and overspeed during descent. The Auto throttle is active but the throttle is not moving to correct the speed, this ending in stall and crash. I noticed too that I could move the throttle and it would respond to my input. I don't know why it happen, it seem to happen sporadicly and not on every flight. It might be that there was a rapid change in wind speed and direction, but I can't confirm this since I don't have this problem anymore. It seem to work fine after I reformatted my hard drive and installed it again, but it didn't work by only reinstall the 747 software, I tried that a several times with no luck.

[Chaos81 110]

>PS. Why didn't you include the later 744 panels? (engine>Auto-start, etc)? Some of this panel's systems belongs in the>earlier versions of the 744, still pleasant and very accurate,>though...Like what?

[Guest The_Glideslope]

Ok B744Here's what happens.I reloaded the flight a took off again. The problem didn't show up until I cruised.Then it halted after the 10000ft step and I noticed the A/T was off BUT the switch was on, VNAV on and all the pattern I told you before.On the PFD the indications were:(BLANK) | LNAV | VNAV PTHIf I pressed the VNAV button as you suggest, SPEED lights up on the left indicator and it kicks in A/T.So, it seems the problem isn't my operation or interpretation of the panel warnings, I suppose. Although I don't know what triggers it, it's pretty obvious I don't touch the vnav button during flight.Then again, shouldn't this be ALERTED to the pilot with a Caution note? This is serious. It's a silent threat.About the question on the newer panels in the 747.Engine Autostart switches (as opposed to manual start) can be found above the ELEC ENG Control buttons in newer 744's. THIS IS CRITICAL SINCE AUTO-START IS A TIME SAVER.Anti-Ice selectors (Wings, nacelles, etc) are now Switches instead of buttons.Even though it's a module, Autobrake selector is set in the CO-pilot's side of the lower console and not the left side.Although not functional, the data printer is an older model.No smoking/Seat Belt sign module has more features in later airplanes (Lav Door Sign, Crew Rest call, Obs Audio Ent). Not really important...Lateral Stand-by Dual HSI optional, very rare on later models. But it is an option.I guess the Crew Call selector (there but not functional) and Engine Auto Start were two things I would like to see.This is something for you to think about.MOST of the FMC inputs in real life require to press the EXEC button.IRS alignment for example, requires you press the EXEC on ANY input on that page. But not the PMDG 744. I'm not sure this is airline option, but sure is critical.All inputs that mess with aircraft weight, position, course, must require the EXEC key press.Some Airlines procedures actually require only one crew member to operate the CDU and the other crew member to confirm the input and press EXEC.At least that's what the AOM says... :)

[Mats_J 2]

Jon,>I reloaded the flight a took off again. The problem didn'tThis is what I would say is the crucial statement. If you loaded a saved flight I said in my previous post that this is a known problem and there is a workaround.>Then it halted after the 10000ft step and I noticed the A/T>was off BUT the switch was on, VNAV on and all the pattern IA/T was armed (switch on) but not active (no mode in FMA).>If I pressed the VNAV button as you suggest, SPEED lights up>on the left indicator and it kicks in A/T.There you go! ;-)>Then again, shouldn't this be ALERTED to the pilot with a>Caution note? This is serious. It's a silent threat.Pilot's rarely reload flights either so check your FMA after you reload the flight.Hope it helps,

[rgamurot 1]

This topic has actually been discussed many times and a few patterns have been discovered. For one, sometimes if you open a menu in FS9, your engines do a temporary flame-out before coming back in. The A/T disconnects at that point and must be reconnected. Other than that though, I can't think of a real reason it would disconnect with that frequency. I actually haven't had this happen to me in a while. It stopped after I armed LNAV and VNAV at the gate. Then I arm the A/T during taxi and also use TOGA to take off. I guess you could try this and see if it still happens. Above all else I would say to keep and eye on your FMAs and see when the A/T disconnects.About your questions about the panel. I would like to see a newer panel too but I agree when you say the panel is very funtional. But about the Autostart. You sound as if there is no Autostart but I've been wrong before. If I am right (which is a miracle), you will find the Autostart by the start switches.If you would really like an extra dose of realism, I would recommend taking a look at FS2Crew. I find it a real help. You finally have a Co-pilot to manage things like the lights and checklists and you also have a flight attendant. Considering the price of other must have addons, I personally think that FS2Crew is fairly low cost but trust me, it's high quality. Just like PMDG. (The quality part, not so much the price but you have to admit, it's more than worth it.):)Ryan GamurotLucky to live Hawai'ihttp://www.precisionmanuals.com/images/forum/supporter.jpg

[Qavion 19]

"Engine Autostart switches (as opposed to manual start) can be found above the ELEC ENG Control buttons in newer 744's. THIS IS CRITICAL SINCE AUTO-START IS A TIME SAVER."PMDG has a single button Autostart (as found on RR and GE powered aircraft). What you describe is the P&W version (P&W took a long time to catch up with the other engine manufacturers). PMDG is essentially based on a GE powered aircraft (Ignition, electrics, pneumatics, hydraulics, etc)."Anti-Ice selectors (Wings, nacelles, etc) are now Switches instead of buttons."Switch type defines whether the aircraft has Ice Detectors or not. This is an option. Our airline originally chose 744's without ice detectors (I think the older systems were less reliable). Our later aircraft still only have Ice Detectors fitted to the NAI system, not the WAI."Even though it's a module, Autobrake selector is set in the CO-pilot's side of the lower console and not the left side."Location is an airline option. You could stick it in First Class if you really wanted to :("Although not functional, the data printer is an older model."Have you tried clicking on any of the printer buttons in the VC? The paper may come out of the wrong slot, but the printer does something."No smoking/Seat Belt sign module has more features in later airplanes (Lav Door Sign, Crew Rest call, Obs Audio Ent). Not really important..."All optional again."Lateral Stand-by Dual HSI optional, very rare on later models. But it is an option."It would have been nice to have every 744 option known to Boeing, but you have to draw a line somewhere (or the sim would never be finished... and would take up half your hard drive if it was)"I guess the Crew Call selector (there but not functional) and Engine Auto Start were two things I would like to see."Most airlines now have special door switches related to cockpit security (and camera systems), but, for obvious reasons, these were omitted. "MOST of the FMC inputs in real life require to press the EXEC button.IRS alignment for example, requires you press the EXEC on ANY input on that page. But not the PMDG 744. I'm not sure this is airline option, but sure is critical."What do you mean by IRS alignment? I do IRS alignments almost everyday on various airlines and have never had to push the EXEC button. Where are you getting this information from? Are you a 744 pilot or engineer?"All inputs that mess with aircraft weight, position, course, must require the EXEC key press."ALL inputs do NOT require EXECution on all the airlines I've worked on (British Airways, Singapore Airlines, Malaysian Airlines, JAL, Qantas, Air New Zealand, Korean Airlines, Atlas, China Airlines, ... Which real world 744 airline do you work for and who makes your FMC's?)PMDG was beta tested by lots of real world engineers and pilots from a number of different airlines. Yes, there may have been a few discussions on what they wanted in the sim, but they managed to reach a compromise at some point :-beerchug Hope you understandCheers.Q>

[Guest The_Glideslope]

About the operation that caused VNAV erratic behaviour.Ok! I got it. It persists upon loading the flight. Also noticed the problem of going into the FS9 menu.About the panel versions.Thanks for the insight. I am not a real pilot, I just like to read, sometimes too much. While some people read Dan Brown's novels, I read the 744 AOM and Mike Ray's 744 Simulator Checkride manual.lol...AH! The EXEC need. I found in the UAL 744 AOM and Mike Ray's book. I seems only natural these options require EXEC press.But if you say so, then I'm game!:)

[Qavion 19]

"AH! The EXEC need. I found in the UAL 744 AOM and Mike Ray's book. I seems only natural these options require EXEC press.But if you say so, then I'm game!"Interesting.... I never got around to reading that manual, but I've heard of it. Also, I haven't worked on a UAL aircraft for a few decades, apart from a few hours last month (when their line-station engineers needed a 744 Avionics specialist). UAL do have some interesting options, but I don't know why there would be this kind of FMC option. I'm wondering if Mike Ray and the AOM were just making generalizations?Cheers.Q>

[Jet Tech 31]

Gentelmen,Hear is a reference to an extensive thread that discussed this problem in depth some time ago and should help solve the problems you are seeing.http://forums.avsim.net/dcboard.php?az=sho...ing_type=searchRegardsPaul Gollnick :-cool Technical Operations/Customer Operational SupportPrecision Manuals Development Groupwww.precisionmanuals.comhttp://www.precisionmanuals.com/images/forum/devteam.jpg