LNAV engagement criteria

[Manicured garden]

Hello,

One of the B737 LNAV engagement criteria is :
(outside of 3 NM, airplane must be on intercept course of 90 degrees or less.)

So according to that criteria; suppose that
* you are flying on heading 300 degrees,
* airport has 1 runway, 09-27 rwy, and 09 in use.
* airport is at your north (360 degrees), 10 NM ahead of you
* on ND, magenta line is straight from RWY09 (direct intercept)

When you press LNAV, would you see ARM or get NOT INTERCEPT COURSE?
In this case, what should be the max heading to intercept in this kind of situation?

.

[daf]

I’m wondering why no one replied to this thread. Let me answer: cause this knowledge is theoretical and not needed for operational use. Day to day operation I never wonder if I am within the degrees specified in the FCOM vol.2 chapter automation page Xxx.

If I one day wonder why a/c did not intercept the LNAV and I have time in FL430. Then I will open the book and look for the answer. This is why we always have to be aware what is written in the FMA. If your FMA is not writing LNAV armed or engaged..... guess what.... it is not and probably you didn’t fill the engagement criteria’s. So be it.... move closer to your magenta line and try again....
how many ways is there to disengage a 737 autopilot?? 7 but who counts?

Those people not agreeing with me and think that this knowledge is necessary, please tell me how many fan blades are on your specific aircraft or how many degrees it takes before the bleed system overheats.... these things are not operational necessary...

Sorry for bitching and bear with me. We are pilots, not astronauts... not talking about manual skills or the other popular subjects nowadays with “package pilots” I’m sure u know what I mean.

DAF

[Skyjob]

* you are flying on heading 300 degrees,
* airport has 1 runway, 09-27 rwy, and 09 in use.
* airport is at your north (360 degrees), 10 NM ahead of you
* on ND, magenta line is straight from RWY09 (direct intercept)

You will NOT see ARM ever, LNAV will be annunciated when criteria are met.
In this case, the angle between 090 inbound course and flown course of 300 is 150 degrees, thus it does not meet 90 degree intercept angle requirement.

If my above reading of your situation is incorrect, maybe a picture of your situation may be useful

[Avenger]

MG, you have already selected DIR CRS 009 in the legs page and put the inbound course in the scratch pad to draw your magenta line. You current lateral mode is HDG SEL. Pushing LNAV:Push – •
LNAV Switch
commands AFDS roll to intercept and track the active FMC route annunciates LNAV as roll mode and illuminates LNAV switch light.
•
LNAV Mode
In LNAV mode, the FMC controls AFDS roll to intercept and track active FMC route. Active route is entered and modified through FMC CDUs and can include SIDs, STARs, and instrument approaches.
LNAV engagement criteria in flight:
• commands AFDS roll to capture and track selected VOR or LOC course
• annunciates VOR/LOC armed or engaged as roll mode and illuminates VOR LOC
switch light.

So, LNAV will do as intended and intercept the inbound CRS that is active in the legs page, presumably as the airport is only 10 miles ahead you will select the appropriate mode for the approach you are attempting , VOR LOC, APP, LNAV etc etc, however, until intercept HDG SEL will be Green and above it LNAV in white (depending on A/C fit)