Boeing Climb Thrust!!!!!!!

[michelmvd]

Hi Thunder 175

VNAV is a rather complex mode item and not working all the same in the different Boeing aircraft. The "system" is working differently in the "older concept" B737 than in the more modern B747/777 type of auto-flight management. This makes it even more difficult for PM to implement it correctly in their software.

I can't speak for a B737, but as a good exemple how autoflights are working in real, this is how VNAV should work for the B744 / B777.

According SOP, VNAV must be armed on the ground (together with LNAV)

Command Speed VREF+20 after rotation

VNAV becomes active at 400ft RA

At the moment LNAV/VNAV becomes active, the TOGA modes end (which is a F/D mode only).

VNAV will command a pitch down at the preset altitude of the FLAP/ACCEL.HT in the TAKEOFF REF page of the CDU and command a VREF+100 speed. (On heavier T/O weights this can be higher than 250)

(exemple : 10/1500 : aircraft speed will be set to VREF+100 and will pitch at 1500 Ft to start the flap retraction scheme.

VNAV will command CLB speed (or CLB+1,2) at the moment the preset factor in the THR REDUCTION (TakeOff page) is reached.

'exemple : FLAPS5 CLB1 : aircraft will come in CLB1 speed mode at the moment FLAPS5 are set. TO thrust mode (or TO1/2) ends at that moment.

All this must happen with or without A/P on. (F/D mode - bars command) In most SOP, for T/O in complex airport SIDS situations / noise procedures, A/P is on after 500ft.

This is how it works in the real B744, VNAV behavior in PM for B744 is unfortunately totally unrealistic. I suppose for the B737 is it futher developped, as actually these days, the PM software is more focussed on the B737. I heard from the real life pilots, there isn't such a high degree of automatisation in the little boeing.

To have a good behavior, it is also very important to use a proper airfile, as it all depends on good airspeeds/ climb pitches performances etc at the correct altitudes. That is also the reason some guys has problems with it and others not. Airliners are flown by the numbers and their behavior can be very different if these are not correctly followed or set.

B. Rgds
Michel

[Thunder175]

Thanks for the awesome reply! I'm mostly flying the 738 so its probably a good thing PM is geared toward the 737 series! Course I am using a panel-less PMDG 737 at the moment so I don't know how much better the flight dynamics can be. I'm anxious to try out the new POSKY 747 v4 with the v9.7 FDE files.

[michelmvd]

Well Thunder175, it is of course good for the B737 fans, but a pitty for all others as the original idea of PM was to develop a cockpitsystem for a lot more types What the B744 concerns, a lot is done, but some major differences still need to be adressed in the VNAV and MCP/CDU operation matters.
Via PMSystem we can do a lot of the logic ourselfs, but not all.

If you have good results concerning the new Posky B744 FDE, pls inform us here.

See you

Michel