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Bobsk8

Question on takeoff heading select and Vnav lights.

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Been flying the 737 for many months. Lately I notice that if I select Vnav and heading select prior to takeoff, when I line up and hit TOGA, both the heading and V Nav light on the MCP both go out, and I have to reselect them after liftoff. Am I doing something wrong, or did I just not notice this before? 

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There is an AFS option in your aircraft specific settings for roll mode after takeoff, "Determines which roll mode the flight director goes into while in TOGA mode after takeoff. Note that wings level results in a blank FMA roll mode." Verify it's set to your preference.

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There is an AFS option in your aircraft specific settings for roll mode after takeoff, "Determines which roll mode the flight director goes into while in TOGA mode after takeoff. Note that wings level results in a blank FMA roll mode." Verify it's set to your preference.

 

Thanks...

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Look at the FMA to see what's active, not the MCP.

Exactly! The FMA is the only way you should confirm what is active.

 

-OPERATOR SPECIFIC-

 

After Take-off our AFDS commands heading select unless LNAV is armed

 

LNAV armed

 

After pushing TO/GA HDG SEL engages, LNAV remains armed and will engage at 50ft RA and follow your magenta line.

 

HDG SEL armed or no roll mode selected

 

After pushing TO/GA HDG SEL engages and will remain engaged until another roll mode is selected.

 

After 400ft PF will verify the FMA or call for a different roll mode if required. Sometimes ATC will request us to remain runway heading after departure, you usually have to match the magenta heading bug into the heading pointer (which is usually set to runway heading) so you don’t drift either side (We always have a crosswind in the UK!!!!)

Good luck!

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Exactly! The FMA is the only way you should confirm what is active.

 

-OPERATOR SPECIFIC-

 

After Take-off our AFDS commands heading select unless LNAV is armed

 

LNAV armed

 

After pushing TO/GA HDG SEL engages, LNAV remains armed and will engage at 50ft RA and follow your magenta line.

 

HDG SEL armed or no roll mode selected

 

After pushing TO/GA HDG SEL engages and will remain engaged until another roll mode is selected.

 

After 400ft PF will verify the FMA or call for a different roll mode if required. Sometimes ATC will request us to remain runway heading after departure, you usually have to match the magenta heading bug into the heading pointer (which is usually set to runway heading) so you don’t drift either side (We always have a crosswind in the UK!!!!)

Good luck!

 

Every time I think I have a pretty good handle on the 737, I find out that there are many things I still haven't figured out yet,,,,, :wink:

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Every time I think I have a pretty good handle on the 737, I find out that there are many things I still haven't figured out yet,,,,, :wink:

 

Almost 4 1/2 years and 3200 hours on type and I still learn something new everyday...

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Sometimes ATC will request us to remain runway heading after departure, you usually have to match the magenta heading bug into the heading pointer (which is usually set to runway heading) so you don’t drift either side (We always have a crosswind in the UK!!!!)

 

Interesting, in the US the fly runway heading clearance means exactly that and if there is a cross wind then ATC knows that everyone is going to be tracking to the left or right or the extended runway centerline.  Obstacle clearance is assured for crosswinds in the TERPS process.  They prefer we don't anticipate their anticipated clearances.

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OPERATOR SPECIFIC-

 

After Take-off our AFDS commands heading select unless LNAV is armed

 

With the NGX and LNAV armed for tkoff, it kicks you out after engaging CMD A or B. Surely thats a bug?

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Interesting, in the US the fly runway heading clearance means exactly that and if there is a cross wind then ATC knows that everyone is going to be tracking to the left or right or the extended runway centerline. Obstacle clearance is assured for crosswinds in the TERPS process. They prefer we don't anticipate their anticipated clearances.

Years ago I did a Citation type. I was having difficulties in the sim. The instructor kept busting my chops for straying off course. I was following the profile and clearance. He wanted me to maintain track, not heading. Things got a lot easier after that was cleared up.

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Yeah, this is a common misconception. Just like vectors, if everyone is flying the same heading, they will all essentially be drifting at the same rate. For this reason, if a controller says to fly a heading or maintain runway heading, you're expected to fly the heading. Obviously, if you're in a situation where an examiner is saying otherwise, just shut up and nod, but fly the heading in practice. If you're feeling bold, perhaps point said examiner to the excerpt below...after getting your cert from him or her  :P

 

 

When cleared to “fly or maintain runway heading,” pilots are expected to fly or maintain the heading that corresponds with the extended centerline of the departure runway. Drift correction shall not be applied; e.g., Runway 4, actual magnetic heading of the runway centerline 044, fly 044.

 

FAA PCG R6 and R7.

 

NOTE: If you're flying an RNAV departure, you will be tracking those lines, but in those situations, you won't hear "fly heading" or "fly runway heading."

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About the heading or track deal, I have always listened to the Heading command. But I and a host of other airplanes don´t fly with LNAV. Whatever you maintain, could it be that the only important thing is that the aircraft does not violate the other side of the runway centerline ?

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Lot's of country/continent specific requests I guess regarding what ATC want you to maintain.

 

I've had in Europe instance where ATC request to maintain runway heading and they actually want you to "Track" the runway as opposed to maintaining a radar heading after take-off. I must correct myself regarding procedure in the UK. ATC will instruct you to "Climb Straight Ahead" or more uncommonly "Track Extended Centreline" during a departure clearance which means exactly that, they want you to track the extended centreline.

 

Most the time as soon as we're airborne PM usually matches the bug with the heading anyway before you engage the A/P and the MCP becomes yours, very rarely complete a SID and straight onto vectors anyway!

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