emvaos

Ah yes. Since we touched on SPD INTV here are another two differences with basically all Boeing airrcfat before. 1/ When you speed intervene (open speed window) the active pitch mode will remain VNAV PTH and AT mode SPD provided current IAS is within the magenta speed band (as noted already above). In previous Boeings that would only happen when the FMC is on-approach mode. 2/ When you close the speed window and go back to FMC speed then if the last commanded speed intervention target is LESS than the FMC speed (e.g. ECON descend speed) then the FMC target is updated to that lower last speed intervention target value (protected by minimum allowed ofcourse). Sort of works like direct altitude intervention without creating a MOD. So if control asks you to decelerate from an ECON speed of say 280 to 250 knots all you have to do is "open" the speed dial on the MCP dial in the new lower target speed (here 250) and close the speed window. You will see line 2 left on the VNAV DES page updated into SEL SPD 250.

Simon correct. OPT ALT is basically a function of weight. It will not take into account forecast wind and it will also do not take into account the fact that for a given cost index ECON SPD will vary between current CRZ ALT and STEP TO ALT. RECMD ALT on the other hand is quite a bit more technical. The algorithm performs simulated runs (ie solves the equations of flight) from 9000' below to MAX ALT above as if the airplane was cruising at those altitudes for the next 500nm of the active flight plan (that is for about the next hour or so of flight). RECMD ALT takes into account foreact wind (and temperature) and the variation of ECON SPD changes. The fuel consumed at the end of all those "simulated" runs is recorded and compared and the most economical run (even by 0.1 kilo) is the answer (for the next hour I repeat). RECMD ALT will NOT take into account the extra fuel burn cost of the step. Now what might happen mathematically under some circumastances is this : for certain outside air pressure distributions and ISA deviations at very high altitudes and cost indices, near MAX ALT, the VNAV operational envelope might be enforced ie. mach number might be restricted resulting thus in an equivalent lower cost index number. That is while ECON mach number at MAX ALT might be say .855 the environment might result in a 0.3g-buffet limit of .845. As a result the RECMD ALT solver will calculate a run for this "protected" lower Mach number (at least for a part of the 500NM) and save a couple of kilos. So care should be applied. NOTE : The cost of extra fuel burn to climb is accounted for when you create a MOD/ACT with a new CRZ ALT. The fuel remaining figure (as all other variables such as time) does take into account the CRZ CLB part. Best, Vangelis

Gents, I thought I'd quickly insert a couple of paragraphs of the VNAV Differences manual regarding the -8 to clarify the issue (my underlining). (NG FMC) The descent gives path control priority and is constructed as a flyable, non-idle descent path, to allow VNAV to control speed and maintain the path with minimal flight crew input. To support path control priority, when on path in descent, the VNAV mode is VNAV PTH and autothrottle mode is SPD. (NG FMC) The offidle descent path is constructed slightly shallower than a traditional idle path descent to allow a margin of speed control during the descent. The VNAV descent mode is VNAV PTH and autothrottle SPD for the entire descent profile, similar to today’s 777 or 747-400 on-approach mode logic. This enables the autothrottle to remain active during the descent and automatically make small thrust adjustments to maintain the descent speed while remaining on path. (NG FMC) With thrust levers at the idle stop in an accurately forecast VNAV PTH descent, the aircraft decelerates approximately 5 knots over 3000 feet altitude. This is heavily dependent on the accuracy of forecast winds. The more accurate the forecast, the more accurate the FMC calculates predictions and generates the descent path. Speed brakes may be required. This is exactly how we have modelled it. I hope this is the definite answer to questions as it comes directly from the manufacturer. Best, Vangelis

It has an EEC (simpler) not FADEC. The amber limit uses TAT (total) and true altitude.

For TO limits the FMC is using static air temperature (not total) and current true altitude (ie true altitude above sea level).

My guess is that your dismounting your yoke results in some serious electrical disruption. It appears you are losing both #2 and #3 AC buses. WHat have you mapped on control levers and buttons ? RUDDER RATIO is a latched status message. Will stay there until you de-power the airplane for the engineers to see on ground.

It is indeed due to throttle HOLD. In this case the AT is disconnected and thus it will NOT move thrust levers to adjust for those tiny differences. Remember take off thrust is calculated on the ground using outside temperature and a stationary plane. Within the first few hundred feet your OAT will change and the aircraft's speed will also change and thus table interpolation will give a tiny (1% ?) difference. As soon as HOLD goes to THR REF at 400ft the AT will resume its work.

You do not necessarily need CREATE AND LOAD TO FSX if you load the same flightplan in AS2016 or ASN. Active Sky reads standard FS flightplans. Instruct your flight planner to export one in FS format too. This, by the way, also enables DES FORECAST. PS. Read also what Kyle suggested above

LEGS PAGE then 6R to RTE DATA. Press 6R and a request will be sent. Wait for it for a few seconds. You ll receive an ACARS message. Press LOAD> and EXEC. You ll receive DES FOREACST winds too. Go to VNAV PAGE 3 (DES) click FORECAST then LOAD those too (DES FORECAST does not need EXEC). PS. 777 is the same by the way

Check your progress page. The fuel remaining at destination (4th line) is less than required reserves entered in the PERF INIT page. You need to add more fuel (MENU/FS ACTIONS/FUEL) PS. OT: Do not forget to load winds aloft if using AS2016/ASN

The AP even in single channel will drive the plane to the runway. You lose all redundancy however in case of failure + all other autoland features (e.g. stab trim bias, rollout, rudder and de-crab control etc)

Your controls are not centered John. AP operation has nothing to do with flaps. The same button used for flaps is perhaps affecting elevator and/aileron position. Give away is strikeout in the FMA pitch and/or roll mode prior to AP disconnect. There is an option in the menu that instructs AP to ignore control inputs.

This functionality is not there in the modelled FMC.

Flaps 10 ?

Before removing the GPU (ie. EXTernal power) connect the APU generators [1 and 2]. Your ship will thus suffer no AC power interruption. Your APU of course must be running. PS. As noted above no you cannot re-align, full or quick align the IRS in the air. On the ground and virtually stationary. You 'll have to recycle the IRS mode selector switch to OFF and then to ALIGN->NAV to do so.

Erm.. No ! On FLCH the thrust limit will switch to either CLB (all engines operating) or CON (engine out). FLCH does not necessarily drive the throttles to max available thrust. See why in post(s) above

As Kyle noted above power interruption. Your centre IRS is dead. Re-align.

SImbrief is adding too long waypoint names, beyond PMDG flightplan specs. As I responded in the other thread the problem is now solved (by adding protection) and there is just a little wait for the next update.

Thank you Alex

When we advertised difference performance for different engine variants we were not lying! As far as flight dynamics and FMC database goes these are three different aircraft. The numbers you see are straight out of very very detailed manufacturer data and related mathematical functions and graphs. All ECON speeds (including climb, cruise, LRC, driftdown/EO and descend) are the real ones. The same applies to v-speeds, buffet speeds, OPT/MAX ALT (4/3/2 engines) etc etc. Only VREF and take off trim settings are common. Enjoy!

This was probably due to odd ISA deviation. In VNAV (and FLCH) the FMC will protect the plane from exceeding the envelope (as you saw).

I believe so. This nice feature is there since the 757 for all Big Boeings ie. the 57/67/47 and 77 chronologically. I believe Boeing introduced this given the vast weight-to-thrust differences these airplanes can have in different flight conditions and as an incentive for the pilot to use FLCH rather than VS. FLCH always protects the plane from going outside the speed envelope while VS does not. Makes sense also for small altitude changes and pax comfort. On a light 744 going from 5000 to 7000 at full thrust it might become a 6000 fpm maneuver. On the other hand, it can be a PITA if you intend to climb only 1000 ft and you have to do it at 500 fpm (use VS instead). Our 777 if you own it has the exact same model. Best, Vangelis

You cannot define cruise speed segments using the 747-400 FMC. You do it old style When entering a NAT you set SEL SPD in VNAV CRZ and when exiting you select <ECON or <LRC same page.

Leif, I've seen the video. First : FLCH is an FMC driven mode aiming to reach next altitude in 125 seconds or more. It will accordingly set appropriate thrust (not necessarily max as in VNAV SPD). This why you see THR and not THR REF in the FMA window when you climb in FLCH. In this example at the altitude engaged it is shooting at around 1000 fpm or slightly less at target climb speed in MCP window and current flaps! Not a lot of thrust required for this. Second: you retract flaps 20 knots below the green marker. You go from 20->10 at the 10- marker and 10->5 at the 5- marker. Not 10->5 at the 10 marker as in the video. Otherwise you have the aircraft hanging out at a very high angle of attack and hit the wrong side of the drag curve. Take also into account that you order the plane to accelerate too and you got very low climb and acceleration rate. PS. FLCH and VNAV SPD do NOT let the aircraft (any Boeing plane in fact) sink in a climb or climb in a descend! Best,

Ciao Fabrizio, Had a look at it from a ticket forwarded from support. It is a SimBrief issue saving a custom AIRAC object with a name too long against PMDG flughtplan specs. Added protection against that so please wait for the next update. Grazie, Vangelis