737 Approach Autothrottle Question

[VHOJT 165]

Hi there chaps:Probably the 737 is the last thing on most minds at the moment, however, I have a question to ask as I attempt to master the aircraft after lots of long hauling in the 747. Admittedly I have only tried this at one airport/approach.Coming in to YMHB Hobart for the runway 12 ILS, I press the APP button on the MCP and engage both autopilots and the PFD annunciates VOR/LOC and GS green as I would expect. However, the APP button does not light up. Moreover the problem is the autothrottle: it reverts to the ARM annunciation and refuses to maintain speed, even if I switch it on and off and try and press the SPD button on the MCP. On the 744, this would cause the autothrottle to enter SPD mode, is this the same as the 737? I had to manually control the speed during approach before I disconnected the AP.Am I doing something wrong?I was previously in LNAV/VNAV. I'll attach a screenshot just in case it may be helpful. Would it have anything to do with the RWY CRS APP ERROR message the FMC gave me before starting the approach? I imagine not. I assume this is because the FMC thinks ILS course is 122, whereas the charts and ILS frequency in FS say 120. I set the CRS and HDG selectors on the MCP to 122 to agree with the FMC, just to see if it made any difference from flying the approach with the selectors at 120 as I normally do, and it didn't.Any help would be much appreciated! Thanks in advance,RudyPS also just noticed - shouldnt't the thrust limit be G/A, rather than CON, at this stage?

[Orlaam 306]

The APP and VOR LOC buttons extinguish after a certain point, I believe when the G/S is captured. I never use the autoland mode, so I can't remember if it says autoland, but since it says FLARE under your G/S FMA message, I think that means it's ready to autoland. I can't say anything looks abnormal there.The RWY CRS APP error message is exactly that, it sees your course isn't matched to the FMC, but a couple degrees won't matter, although it should match FS even though the FMC data is newer. It's up to you what to use for your course setting, but you can mostly ignore the error message as long as you know what's right.As to your A/T problem, I don't know. Was your throttle (hardware) idle so is didn't interfere with the A/T? The A/T should be commanding 152 or the speed set in VNAV. If it drops below 143 Vref, then it's possible the throttle you use manually is messing with it. This is another thing I really can't remember having problems with.I have no idea when GA thrust is set, but perhaps the A/T issue was throwing it off.The A/T in the 744 is so different IMO. I've always had trouble understanding it, but the 737 is simple. It does what you think it should.

[VHOJT 165]

The APP and VOR LOC buttons extinguish after a certain point, I believe when the G/S is captured. I never use the autoland mode, so I can't remember if it says autoland, but since it says FLARE under your G/S FMA message, I think that means it's ready to autoland. I can't say anything looks abnormal there.The RWY CRS APP error message is exactly that, it sees your course isn't matched to the FMC, but a couple degrees won't matter, although it should match FS even though the FMC data is newer. It's up to you what to use for your course setting, but you can mostly ignore the error message as long as you know what's right.As to your A/T problem, I don't know. Was your throttle (hardware) idle so is didn't interfere with the A/T? The A/T should be commanding 152 or the speed set in VNAV. If it drops below 143 Vref, then it's possible the throttle you use manually is messing with it. This is another thing I really can't remember having problems with.I have no idea when GA thrust is set, but perhaps the A/T issue was throwing it off.The A/T in the 744 is so different IMO. I've always had trouble understanding it, but the 737 is simple. It does what you think it should.

Hi there, thanks for your reply. Yeah, I was thinking the autoland must have been okay as it was annunciated fine.Yeah, the joystick isn't set to override in the PMDG options, under throttle or surfaces, so I suppose that rules that idea out. I don't suppose you or anyone has any other ideas?

[FlyChuck 3]

Buttons on the 737 MCP panel only light up when they can be deselected. You can see your active modes on the FMA (on the top side of your PFD). The reason that APP does not light up means that by pushing the APP button again, you will not deselect the VORLOC and GS modes. You can only deselect them by toggling the flight directors or hitting TOGA. About the Autothrottle, you shouldn't have the ARM indication. Normally coming from Lnav and Vnav you would get an altitude capture first, causing the A/T to go to the speed mode. And getting an G/S capture should trigger the speed mode also. And especially if you are hitting the speed button, so I cannot think of anything that would give these indications. Time for a manual landing :( Cheers!Tom

[Guest fencer88]

Hi Rudy,Just one question : do you see this problem at other airports as well?And also, regarding your problem at YMHB Hobart (runway 12 ILS), is is a default airport or are you using an add-on scenery?The reason I am asking is I wonder if you could have a conflict between default and add-on scenery ILSs. An easy way to check would be to run ScanAFD.exeWhile you are at it, it doesn't hurt to check also the registries (FS_Registry_Repair.exe on the flight 1 site : http://www.flight1software.com/files/FS_Registry_Repair.exe ). I assume you are running FS9/WinXP;The truth is I am not sure at all that it will help but I must admit I am out of ideas and these checks won't take long (or hurt) anyway.Cheers,Bruno

[Tabs 2,790]

It's been a while since I've done anything with the NG... I'll try to go test this approach at some point and see what I get... it's been a wee bit busy with the MD-11 release, so I'm not sure exactly when, but I'll report back on what I see.