kmw510

I get the "unable 270 kts at XXXX" message quite often and can't see any reason why. I fly standard routes from Flight Aware and use the current SIDS and STARS. Is there anything I might be doing wrong or is this common? Kevin Wilson

Thanks Kyle Kevin Wilson

Thanks Ralph, I will take a look Kevin Wilson Thanks Kevin, do you know why the speed is still indicated in the speed window after disengaging both autopilot and auto throttle?

I am getting inconsistent results with auto throttle speed control upon glideslope capture. When in VNAV and selecting APP I obtain VORLOC and then G/S and the speed is controlled properly with auto throttle. When using the MCP to hold altitude and control speed until I get to the IAF I get inconsistent control of speed upon glideslope capture. There are times the speed is controlled in the same way as when I enter via VNAV and other times the speed control window flashes and the speed is not controlled. I am not totally sure what the proper operation is so don't know if this is a bug or my lack of understanding Kevin Wilson

I assumed I did since the FMA indicated "ALT HOLD", however although I know I hit the CMD button I don't recall if the light went on or not. I recreated the event this time intentionally not selecting CMD and noted that the same thing happened. The plane continued its climb although the FMA indicated "ALT HOLD". I now think that the original problem was that I didn't actually engage CMD and thought the autopilot was on since the FMA indicated "ALT HOLD". The question now is why did the FMA indicate "ALT HOLD" if the autopilot wasn't on. Kevin Wilson

Yes, one of the yoke switches is programmed to be aileron trim Kevin Wilson

The FMA showed "ALT HOLD" without the box drawn around it

I began a flight planning to fly without using the FMC. I did not program the FMC and took off manually. When I reached the altitude and speed I wanted I manually leveled the plane and adjusted the desired speed with throttle setting. The altitude I leveled at was not the same as that set in the mcp alt window. I engaged auto throttle and hit the alt hold switch expecting to see ALT HOLD in the FMA and the plane continue at the current altitude. The plane started a climb and exceeded the altitude in the alt window on the mcp and continued until I stopped it.My understanding is that the plane should have held the altitude the plane was at when I hit the alt hold switch given the alt display was a different altitude. Kevin WIlson

Im not sure I understand your statement. I understand that the SID charts show MEAs in segments where applicable, however, Im not sure that the airinc data loaded into the FMC when you select that SID contains those altitude constraints. I can see where altitude constraints defined on the chart at fixes show up as altitude constraints in bold in the FMC but don't see corresponding bold entries for any MEAs Kevin W

When double checking the programming of the FMC for the SIDS and STARS I can see where the program almost always enters hard altitude and speed requirements, however, it is difficult to tell whether or not the segment MEAs are being considered. For the most part it appears that the predicted altitudes do not violate the MEAs but I am unsure as to whether the FMC actually considered the MEAs since the numbers are shown as predicted rather than required values. In only a few cases have I substituted a required altitude to cover the MEA shown on the charts but don't know if this was a mistake in the programming of the STAR or SID or where the FMC just doesn't consider MEAs. Kevin W

Hello Kyle, I am guilty of not explaining my issue correctly in the first place. I have no problem with ascent and descent using VNAV with pauses for altitude restrictions. My issue is making altitude changes between top of climb and top of descent when in cruise. At that point it is necessary to make altitude changes per ATC direction or to try to avoid turbulence or head winds. I have gone through the tutorials and many of the Angle of Attack training videos and haven't seen a consistent method of doing this. I have also seen in some videos the attempt at using alt intv with no response from the plane and a bewildered pilot. I won't bother you again except to ask where the proper procedures are documented. I have looked through the FCOM and FCTM for this and have yet to find it. Thanks again for your time and help

Kyle/Matt/Oliver- First of all thanks for your replies. I appreciate the time you have spent trying to help. Kyle- After considering your comment about getting the FMC to think it is cruising again and remembering that I received the "chk alt tgt" when I hit VNAV in an attempt to ascend to new altitude after having been in Alt Hold, I scoured the FMOC and determined that when you descend and are left in either ALT HOLD or VNAV ALT the FMC thinks that the new lower altitude is the cruise altitude although the FMC itself stills says the cruise altitude is the original higher cruise altitude. In this case that is why the "chk alt tgt" message appeared since the FMC thinks its cruise altitude is the current altitude leaving the plane between the FMC altitude and MCP altitude. Given this I determined that to properly get back into VNAV after having ascended or descended using a mode that leaves you in ALT HOD or VNAV ALT you must go back into the FMC and set the cruise altitude the the value you want. After doing this you engage VNAV and be left in VNAV Path. Matt-I never try to operate the AFDS in a manner not intended. The problem is the FCOM provides simple case statements relating how each button and mode works but doesn't tell you how to go about performing required maneuvers. The problem is further exacerbated by the fact that no where in the FMOC does it tell you that upon a descent and subsequent altitude hold that the FMC thinks the new cruise altitude is the current hold altitude in contradiction of what the FMC itself displays. And it is a good thing that the flight computers aren't like iPhones otherwise planes would be lost and crashing all the time. In any case the method I have settled on for making ATC directed altitude changes is as follows: To ascend to new altitude-Dial new higher altitude into the mcp alt window then hit ALT INTV. This will reset the FMC cruise altitude to the new altitude dialed in and the plan will ascend accordingly leaving you in VNAV Path at the end. To descend to new altitude-Dial new lower altitude into the mcp alt window then hit ALT INTV. The plane descends and holds at the new lower altitude and enters the VNAV ALT mode. To transition to VNAV PATH set the FMC CRZ level to the new lower altitude thereby convincing the FMC this is the new cruise altitude. VNAV ALT transitions to VNAV Path.

Ok after 3 experimental flights here is what happened. I first flew the flight entirely on lnav/vnav to baseline the fmc programming and verify all aspects of the flight were error free. The flight flew perfectly. The 2nd flight I did the following: At cruise FL315 the pfd showed "FMC SPD LNAV VNAV PATH". I dialed into the mcp window the new lower altitude of FL305 and pressed LVL CHG. The aircraft descended to the new lower level and settled into on the pfd "MCP SPD LNAV ALT HOLD". The FMC still showed FL315 as the cruise altitude. To resume at FL315 and get back into vnav I dialed in FL350 into the mcp alt window. Upon hitting vnav nothing happened and the fmc message window showed "check alt tgt". Looking at what that message means, the aircraft was not between the mcp altitude and the vnav target. The fmc still showed FL315 as the cruise level, the mcp window was set to FL315 and the plane was flying currently at FL305. I then used lvl chg to ascend to the FL315 and settled into a cruise at FL315 with the pfd state as "MCP SPD LNAV ALT HOLD". Vnav can now be engaged with pfd showing "FMC SPD LNAV VNAV ALT" and an fmc message of "reset mcp altitude" The problem now is I am in VNAV ALT and can't get back into VNAV PATH where I should be. I recalled what William had to say and tried setting the cruise altitude to FL315 in the FMC even though the FMC already showed the cruise altitude as FL315. Upon execution of the cruise altitude on the crz page the plane entered into the VNAV PATH mode again and everything was back to normal. This makes no sense to me and appears counterintuitive and doesn't match the FCOM literature as far as I can tell. Don't know if this is the way it works or the pmdg implementation has a bug

Thank you William, however, I do not want to program the FMC to a new cruise altitude, just follow atc direction until they direct me to resume my plan as filed

I am having trouble transitioning between vnav and using the mcp to make altitude transitions. I have stayed away from vatsim flights until now due to my lack of confidence in this area. While flying under lnav/vnav I can easily make heading changes and speed changes due to ATC direction and then get back into lnav/vnav, however, when using level change and V/S to make altitude changes at times I have trouble getting back into VNAV flight. My understudying is that while in vnav engaging mcp vertical path modes would disengage vnav and then when wanting to disengage the mcp vertical path mode simply engaging vnav to cancel the mcp mode. There are times (more often than not) that I am unable to re-engage vnav and don't know if there is a sim issue or some other condition in the plane preventing vnav engagement.