LNAV and VNAV

[744pilot]

Can it be armed on the ground??So, that after takeoff it automaticaly engages.I bought some videos from ITVV and they always engaged the LNAV and VNAV in the air. But as far as I can remember is it also possible to arm it on the ground, isn't????THanks,

[Guest jpchabert]

No sir, no activation on ground.LNAV and VNAV modes are only activate above 400 fts AGL.

[Chris Willis BAW976]

It is a bit difficult to state, but here goes.LNAV can be armed on the ground as part of the P2 glareshield preperation, IF and LNAV departure is being flown.However VNAV should not be as it makes adjustments to the FD, below the Aa (usually 1000AGL).Recommended is to arm VNAV after take off as the a/c is accelerating.but that is from an sim pilot not a real pilot, Tero can probably give a better answer.Regards,Chris

[Guest Mark McG]

LNAV & VNAV can both be armed on the ground. They will be annunciated in White on the EADI as they will not become active till after 400ft AGL.It is recommended to select a Roll Mode passing 400ft. It is recommended to select a Pitch Mode passing the Acceleration Altitude - usually 1000ft, but some Airports require 1500ft or 3000ft due to Noise abatement. If you have 3000ft as the Acceleration Altitude you then select the Pitch Mode passing 3000ft and the Pitch Mode remains in the TO setting till then - ie it commands V2+15 to V2+25 knots. Arming VNAV on the ground or activating it passing 400ft ( before the acceleration altitude ) is a dangerous practice. You are reducing the pitch and Rate of Climb of the aircraft very close to the ground in roder to accelerate - the aircraft will want to accelerate to the Current Flap Manouevering speed, followed by 250 knots as you retract the Flaps. You will also bust all Noise Abatement criteria. Finally, If you are flying V2+15 till the acceleration altitude, you are ensuring that the aircraft is capable of flying on 1 engine if you should lose 1. BTW - Tero is a sim pilot, who happens to know a lot about the 757 & 767.

[744pilot]

Here, take a look at www.A340.net and go to multimedia and then Boeing, flightdeck videos. You'll see that the lufthansa arms LNAV and VNAV on the ground and it automaticaly engages in the air, just like Mark said.However, that's a B744 and they have a modern EFIS. All B744 do that, arming LNAV and VNAV on the ground and around 500 feet AGL they engage the A/P.Now back to the B767. As far as I know you can enter an accelaration altitude in the FMC and like Mark said, the VNAV will maintain V2+15 about until reaching the acc. altitude. So, you can arm VNAV on the ground and as soon as you are in the air engage the A/P at around 500AGL. As LNAV kicks in at 50 AGL, the LNAV shouldn't be a problem to arm on the ground.PS. I'm not sure anymore if you can enter a thrust reduction altitude in the FMC takeoff page like that is possible on the B744???And if not possible, wat is the Thrust reduction altitude for the B767??

[Guest Mark McG]

The 767 handles things differently from the 744. Thrust Reduction occurs automatically when you change the PITCH MODE from TO to VNAV. This means that if you have armed VNAV on the ground you get the Thrust setting Changing from TO to CLB thrust passing 400ft. You will continue to get V2+15 commanded climb rate to the acceleration altitude. The default acceleration altitude is 1000ft on the 767 - this value can be changed. Each airline has their own Standard operating Procedures, so you can decide if you wish to follow a particular set of SOP's or if you want to create your own for use within the sim environment.

[744pilot]

Thanks allot Mark,That exactly what I'm looking for!! ;)

[Guest psaul]

>Each airline has their own Standard operating Procedures, so>you can decide if you wish to follow a particular set of SOP's>or if you want to create your own for use within the sim>environment. A general question, where can one find these SOPs? Particularly for Delta? ;)

[Qavion]

Arming VNAV on the ground or activating it passing 400ft ( before the acceleration altitude ) is a dangerous practice. You are reducing the pitch and Rate of Climb of the aircraft very close to the ground in order to accelerate - the aircraft will want to accelerate to the Current Flap Manouevering speed, followed by 250 knots as you retract the Flaps.[/i}Mark....Wouldn't VNAV only vary the pitch above the set accel height? (i.e. default 1000' (or 1500' on some airlines) or whatever accel value you have manually inserted into the FMC? 1500', 3000', etc)I think your main worry with prearming VNAV would be the automatic commanded thrust reduction at 400'. The 744 doesn't have this problem as thrust reduction can be set at a particular height above the airport... or upon selection of FLAPS 5.I've been told that LNAV/VNAV arm on the ground is optional on the 767, but I haven't been able to independently verify this.Cheers.Ian.

[Guest Soulman]

Not a 767 SOP, but on our 737's it is standard procedure to arm LNAV at the gate, with VNAV not engaged until after clean-up (which occurs at 3000AGL), so it isn't selected until around the 4000ft mark.When do you arm the A/T Ramon?

[marcom]

I believe the 767 has quite a few options available in this regard (or updates).Most folks would say that you can't engage the AP in TO mode for example (ie it reverts to V/S and hdg hold or att) - but there are 767's around that do have this option - just like the 744.Regards,Mark

[744pilot]

>Not a 767 SOP, but on our 737's it is standard procedure to>arm LNAV at the gate, with VNAV not engaged until after>clean-up (which occurs at 3000AGL), so it isn't selected until>around the 4000ft mark.>>When do you arm the A/T Ramon?I personaly engage VNAV for the accelaration at 1200-1500 AGL, when cleaned up and no speed restriction is active I use spd intv. or FLCH to accel. to 300Kts about. All of this occurs if I do SID dep.If I have a visual departure or vectors I use FLCH at 1200-1500 AGL.All these things implay for the 737NG. In the earlier days of FS2002 when I flow the B744 from PSS I engaged VNAV and LNAV on the ground already.

[Guest ace]

Hej Gents.I am Flying for UPS(Star air)In europe(EDDK) B757-200 and B767-200.We arm L-nav at 400ft AGL and v-nav at 1500 ft AGL A/T on the runway when engines are stable.Star Air has leased 11 B767-200 over the next 12 years and more to come.:-) Best regardsULT/Thomas ulstrup

[Guest B Van Caulart]

>>Not a 767 SOP, but on our 737's it is standard procedure to>>arm LNAV at the gate, with VNAV not engaged until after>>clean-up (which occurs at 3000AGL), so it isn't selected>until>>around the 4000ft mark.>>>>When do you arm the A/T Ramon?>>I personaly engage VNAV for the accelaration at 1200-1500 AGL,>when cleaned up and no speed restriction is active I use spd>intv. or FLCH to accel. to 300Kts about. All of this occurs if>I do SID dep.>If I have a visual departure or vectors I use FLCH at>1200-1500 AGL.>All these things implay for the 737NG. In the earlier days of>FS2002 when I flow the B744 from PSS I engaged VNAV and LNAV>on the ground already.>Ramon, In LDS767 you will be able to program the conditional SID information into the FMC, this includes the VECTOR departures. ;0)Pg 115 of the LDS manualTherefore,the need of FLCH and SPD intervention will not be required, unless of course you get a failure.