B737 Takeoff with VNAV and LNAV disarmed

[tae9141]

Hellow everyone, I am currently undergoing B737 and I got question to ask.

Let us say you were instructed to takeoff and fly runway heading soon after departure,
when you hit TOGA, does HDG SEL automatically selected and shows up on FMA or is it after departure ?

James

[gegemi]

yes. At least on the NG.

[FlyingStone]

It depends on the aircraft, as this is customer option.

It is either HDG SEL for takeoff, which means that as soon as you hit TOGA, you will get HDG SEL on the FMA, or it is wings level in which case the roll FMA will be blank.

[Banana Joe]

Customer options. Ours engage HDG SEL, but there is an airframe or two in the fleet that don't.

[Bergerie1]

As a very old fossil, why don't you just fly the aeroplane?

[733driver]

As a very old fossil, why don't you just fly the aeroplane?

One can do that and at the same time want to understand how the automation behaves i.e. what to expect from it.

[ImbracableCrunk]

If one is doing a course on the 737, why not ask your instructor?

1. Why have this forum if not to ask questions?
2. There are also instructors here.

[Aoyb]

As mentioned it depends. Certainly on the classics and on some NGs the HDG SEL will become active on the FMA at 400’

Until then the roll mode will be blank and FD bars will command wings level

[Jumbo744]

As a very old fossil, why don't you just fly the aeroplane?

Take it easy hero. It has nothing to do with flying the plane. The guy is asking a question about how the automation works on takeoff.

[Derfred]

As a very old fossil, why don't you just fly the aeroplane?

I have a lot of respect for a pilot who is capable of “just flying the aeroplane” when required.

But I have no respect for a pilot who chooses to “just fly the aeroplane” because he actually doesn’t know or understand his aeroplane.

Chuck Yeager apparently would never fly an aircraft until he knew the flight manual by heart and could find every switch blindfolded.

We’d all be wise to fully understand our aircraft systems before we get airborne and be forced to exercise our superior handling skills in an attempt to cover for our lack of study and knowledge.

[Sig229]

At my company all aircraft will stay in TOGA until a lateral/vertical mode is selected. For vector departures we set the heading and call for Heading Select at 400AGL or the charted turn altitude if higher.

[Tomaski]

Wait.... what?? You can actually takeoff with the LNAV and VNAV disarmed?!

Next thing you'll be telling me is that we can fly this thing without Flight Directors!

;););)

[Centaurus]

Flight Director addiction, like tobacco addiction, is a real health hazard.

I say that, having operated with one simulator instructor who screams at his students to "follow the bloody flight director" even though the aircraft is in a gross unusual attitude 30 degrees nose down in a spiral dive.

[anson harris]

As a very old fossil, why don't you just fly the aeroplane?
Bingo! What do I win?

[jmmoric]

As a very old fossil, why don't you just fly the aeroplane?

Old fossils are overrepresented in stall or spin during departure/landings :)

I've read e few reports where they don't use the ASI, but go by their "instincts" getting older.

[misd-agin]

1. Why have this forum if not to ask questions?
2. There are also instructors here.

The instructors at his company will know what options their fleet has. As others have stated "it depends upon which options your company has for their aircraft."

[misd-agin]

I have a lot of respect for a pilot who is capable of “just flying the aeroplane” when required.

But I have no respect for a pilot who chooses to “just fly the aeroplane” because he actually doesn’t know or understand his aeroplane.

Chuck Yeager apparently would never fly an aircraft until he knew the flight manual by heart and could find every switch blindfolded.

We’d all be wise to fully understand our aircraft systems before we get airborne and be forced to exercise our superior handling skills in an attempt to cover for our lack of study and knowledge.

He'd never get airborne in a modern airliner. The manuals are much longer than the manuals of earlier eras. The P-51 flight manual was 78 pages. Switches? In a modern airliner? He can't reach about 1/4 of them.

[Tomaski]

Old fossils are overrepresented in stall or spin during departure/landings :)

I've read e few reports where they don't use the ASI, but go by their "instincts" getting older.

Speaking as an old fossil, relying on the airspeed indicator without reference to the attitude and power settings is simply asking for trouble. I can think of quite a few accidents that resulted from chasing airspeed as opposed to setting appropriate pitch and power.

In my "old school" instrument training parlance, attitude and power are "control" instruments. Airspeed, altitude, heading, etc are "performance" instrument. You set the "control" instruments to the desired positions and then cross-check the "performance" instruments to see if you are getting the desired response. If something is out of whack, then you would first cross-check your attitude and power indicators and, if deemed reliable, continue to fly them and then determine if something is wrong with one of your performance indicators. This is a lesson that is easily forgotten in the age of modern airliners. Sadly, there are many pilots who don't get much beyond following the flight director commands, a method that probably works 98% of the time. It's that other 2% that will get you in trouble.......

[Centaurus]

The P-51 flight manual was 78 pages.

You were spoilt. The Pilots Notes Mustang RAAF Publication Mo. 780 dated September 1950 issued to this scribe, only had 50 pages. RAF Dakota Pilots Notes only had 45 pages, while RAF Pilots Notes for the Lincoln (four Rolls Royce Merlins) in 1950 had 54 pages

[reverserunlocked]

My understanding is the RYR don’t use VNAV for departure, cleaning up they flaps first before selecting it.

[poldek77]

Wait.... what?? You can actually takeoff with the LNAV and VNAV disarmed?!



Yes, I can.

LNAV - normally armed on the ground but I have flown some SIDs where it's not possible due to location of the 1st waypoint. According to OM-B:
Note: For LNAV to be armed on the ground, the departure runway must be selected and the course, to the first waypoint, must be within 5 degrees of the runway heading.

VNAV - my company allowed us to arm VNAV on the ground just last year so before that we used it after clean up. Nowadays armed for take-offs except noise abatement departures - some pilots prefer FLCH, others - VNAV+SPD INTV. On PF's discretion.

[N1EPR]

Its been a few years since I retired, but the B757s I flew tracked runway centerline after TO unless something else was selected. This makes a lot of sense since the protected airspace in case of engine failure is along centerline.

[Airone2977]

Yes, I can.

LNAV - normally armed on the ground but I have flown some SIDs where it's not possible due to location of the 1st waypoint. According to OM-B:
Note: For LNAV to be armed on the ground, the departure runway must be selected and the course, to the first waypoint, must be within 5 degrees of the runway heading.

VNAV - my company allowed us to arm VNAV on the ground just last year so before that we used it after clean up. Nowadays armed for take-offs except noise abatement departures - some pilots prefer FLCH, others - VNAV+SPD INTV. On PF's discretion.

When selected on the ground, LNAV engage at 50ft, VNAV at 400ft.
The issue with VNAV armed on the ground is in the case of engine failure after V1. If you didn't carrefully select EO acc Alt on Take off page 2, it will level off and accelerate to VREF40 + 70 at 1000ft AGL. It could be hazardous expecially if you have high terrain in the vicinity

[Tomaski]

When selected on the ground, LNAV engage at 50ft, VNAV at 400ft.
The issue with VNAV armed on the ground is in the case of engine failure after V1. If you didn't carrefully select EO acc Alt on Take off page 2, it will level off and accelerate to VREF40 + 70 at 1000ft AGL. It could be hazardous expecially if you have high terrain in the vicinity

Just a minor, though pertinent observation here. The 'it' you refer to above is the automation (either Flight Director or Autopilot). At my airline, our practice is to not engage the A/P in an engine out situation until the flaps are retracted, but this might be different elsewhere. That being said, the aircraft should not level off unless the flying pilot wants it to level off, which speaks to the issue of automation dependency. One of the biggest challenges of modern airliners is to know when to override what the automation is trying to do. Yes, ideally one should set the AFDS panel correctly, but if this was not done or done incorrectly, then the pilot needs to be able to fly with reference to the attitude indicator and not the FD bars.