Setting HDG SEL before takeoff instead of LNAV

[guest77]

What is the difference(s) between setting LNAV or HDG SEL on the ground? How does the FDs beheave? As far as i remember if i choose LNAV before i press the TOGA, it holds wings level until 50 ft. How does it beheave on selecting HDG SEL before pressing TOGA? Thanks

[NigelOnDraft]

If you gave us a clue what type / FMS standard you are talking about we might be able to help

NoD

[No_Speed_Restriction]

hopefully with at least PIP otherwise you tend to observe the aircraft at a different postcode once lined up.

[guest77]

my question was for a Boeing 737-800

[ahramin]

I do not fly the 737 but on my collins flight director/universal fms if i select lnav it heads for the first waypoint right from the ground.

In the FMS database on the 37 does it contain vector SIDs? Runway heading until radar vectors departures?

[Coastrider26]

If you refer to the 738 it will disconnect the HDG SEL mode and you can select it again once you're through 400 ft AGL