LNAV engagement on the ground

[vonmar 122]

Randy,My post (screenshots) was not a complaint of any kind.I was just adding to the thread, seeing no screenshots had been posted yet.I was wondering if other pilots were seeing the same thing.Anyway.When the LNAV button is pressed (selected/green in FD System Status) is LNAV now (logically) "engaged" or "armed" before the autopilot (CMDA) is turned ON?What should the manual say?

[crvm 0]

Randy,My post (screenshots) was not a complaint of any kind.I was just adding to the thread, seeing no screenshots had been posted yet.I was wondering if other pilots were seeing the same thing.Anyway.When the LNAV button is pressed (selected/green in FD System Status) is LNAV now (logically) "engaged" or "armed" before the autopilot (CMDA) is turned ON?What should the manual say?

Hello again Vaughan, I didn't get that from you, I just choose to respond to the thread through my reply to your post ;)>. I believe thats the PMDG manual and the mention of arm/engage is for general understanding without going into greater detail. The key for simmers is the FMA. When the FMA shows green it means its engaged. While not getting to technical, the aircraft is manually flown and will be directed in F/D with cues from LNAV above 50 RA if its engaged although not really in 'control' without CMD. While some might say this is "armed" it is not - its really engaged whether or not we understanding its function to guide via F/D or to fully control.

[mv737 0]

See the LNAV light on the MCP how automatically goes off once the TOGA is pressed, then it will engage above 400ft AGL.http://www.youtube.com/watch?v=-X01uY0bJs0&feature=relatedhttp://www.youtube.com/watch?v=7HT8c1SlySs&feature=related

[Spin737 102]

This is from a current Boeing FCOM:

• LNAV (armed) – the AFDS is armed (prior to takeoff) to engage LNAV at50 feet RA.• LNAV (engaged) – the AFDS intercepts and tracks the active FMC route.Either of the following capture criteria must be met:• on any heading and within 3 NM of the active route segment• if outside of 3 NM of active route segment, airplane must be on anintercept course of 90 degrees or less and intercept the route segmentbefore the active waypoint.

RW, when you hit LNAV on the ground, LNAV is in small white on the FMA. When the PF hits TOGA, the LNAV in the FMA disappears and at 50' it reappears in green and is now active.I would personally not call any mode active or captured unless it's in the FMA.

[crvm 0]

This is from a current Boeing FCOM:RW, when you hit LNAV on the ground, LNAV is in small white on the FMA. When the PF hits TOGA, the LNAV in the FMA disappears and at 50' it reappears in green and is now active.I would personally not call any mode active or captured unless it's in the FMA.

LNAV is 'engaged' on the ground and is correctly simulated for the 'type' of equipment PMDG choose when producing this product. Roll modes on the FMA are HDG SEL, VOR/LOC, LNAV (g); ARMED MODES VOR/LOC (w). LNAV is green on the FMA and green means engaged not armed. There was not an option for LNAV to appear in white letters on the FMA during the production of this sim even as an option that I am aware of. Now to optional equipment. There are differences in Boeing aircraft mostly related to carrier options. As an example, LNAV within one carrier with different equipment: LNAV engagement criteria on the ground (I will only list differences): 1, Bank angle is limited to 8 degrees from 50 feet to 200 feet and 15 degrees above 200 feet to 400 feet AGL; 2, bank angle is limited to 8 degrees below 200 feet and 30 degrees above 200 feet AGL. Can you provide your OPS ref page/Date? Is it general Boeing or a carrier? I'm curious as to why the changed this.

[Spin737 102]

LNAV is 'engaged' on the ground and is correctly simulated for the 'type' of equipment PMDG choose when producing this product. Roll modes on the FMA are HDG SEL, VOR/LOC, LNAV (g); ARMED MODES VOR/LOC (w). LNAV is green on the FMA and green means engaged not armed. There was not an option for LNAV to appear in white letters on the FMA during the production of this sim even as an option that I am aware of. Now to optional equipment. There are differences in Boeing aircraft mostly related to carrier options. As an example, LNAV within one carrier with different equipment: LNAV engagement criteria on the ground (I will only list differences): 1, Bank angle is limited to 8 degrees from 50 feet to 200 feet and 15 degrees above 200 feet to 400 feet AGL; 2, bank angle is limited to 8 degrees below 200 feet and 30 degrees above 200 feet AGL. Can you provide your OPS ref page/Date? Is it general Boeing or a carrier? I'm curious as to why the changed this.

I won't name the carrier, but this is current and dated 6/15/2009:

Roll ModesLNAV (white) – when the engagement criteria is satisfied, and LNAV isselected on the MCP for takeoff, LNAV will be displayed as the armed rollmode and becomes engaged at 50 ft. LNAV will be armed on approach, whena missed approach exists in the flight plan, and the Flight Control Computersare capable of entering go-around.LNAV (green) – when the engagement criteria is satisfied, and LNAV isselected on the MCP for takeoff, LNAV will be displayed as the engaged rollmode at 50 ft.

I don't know when the change occurred, but most of the Level D sims I've flown don't correctly model this either (they act like the PMDG). Every NG that I've flown (-7,-8,-9) in the past 3 years has operated as described above.

[crvm 0]

I won't name the carrier, but this is current and dated 6/15/2009:I don't know when the change occurred, but most of the Level D sims I've flown don't correctly model this either (they act like the PMDG). Every NG that I've flown (-7,-8,-9) in the past 3 years has operated as described above.

Thanks I found it. It appears that PMDG modelled a specific FMC U10.6 which is what was current and changes to LNAV behavior began in U10.7 which is why I was unaware (been out of the loop for a few years ;)>) Great info though thanks!

[vonmar 122]

Ok,I am wondering now ... what is right and what is wrong?

[downscc 1,327]

It depends :(

[falcon999 24]

It depends :(

On your perspective...

[crvm 0]

Ok,I am wondering now ... what is right and what is wrong?

Well lets just say the NG is outdated a bit in regards to FMC software updates BUT it is not unusual or wrong. As was stated, some airline simulators still follow PMDG in this regard ;)> As for the new amazing PMDG NG it should be modelled as Matt Colles showed in relation to LNAV since this is the newest FMC software (just a guess here ).

[Spin737 102]

As Randy figured out, the PMDG correctly models the U10.6 FMC. However, the current FMC mod is U10.8A. That's why the disagreement exists. (Oops, you beat me to it, Randy.)