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captain420

Why is it necessary to set HDG/TRK to match the runway?

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I've seen a few people set the HDG/TRK on the MCP on the 737 prior to take off to match the runway, So if they're taking off from runway 28L, they set the HDG/TRK to like 279, what is the purpose or reasoning behind this, because I've never done this and I'm able to take off without any problems.


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On most runways in the event of an EFTO, you'll abandon the SID and climb on runway heading to 3,000', that's why people set the heading on the MCP before takeoff as it's one less thing to have to do in event of an EFTO.

 

Regards,

Ró.


Rónán O Cadhain.

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.


Krister Lindén
EFMA, Finland
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I see, but what's ETFO? 


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Thanks, so I guess I should make this a habit even if I fly without failures. So do we use HDG or TRK when making this selection. I get confused between the 2 and which to use.


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Heading is the direction the aircraft is pointed, track is the path it takes over the ground. Basically track is effected by crosswinds, heading isn't.

 

Typically you'll fly runway heading, but either track or heading is valid depending on the equipment installed on you aircraft.

 

Regards,

Ró.


Rónán O Cadhain.

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I don't remember a flight when I was not instructed by ATC to 'fly runway heading' after takeoff, It sure makes those few minutes before directed to fly waypoint easier if you have a bug to follow esp at night and poor vis.

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I don't remember a flight when I was not instructed by ATC to 'fly runway heading' after takeoff, It sure makes those few minutes before directed to fly waypoint easier if you have a bug to follow esp at night and poor vis.

 

You mustn't fly in Europe / Everywhere in the World other than the USA, we use full SID procedures over here unlike the States that have some bizarre notions about SIDs and STARs...  :rolleyes:

 

Regards,

Ró.


Rónán O Cadhain.

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Hi Aaron,

 

I've seen you ask some good questions for a non-RL pilot, and this is another one.  It's great to see someone want to learn the basics and understand why things are like they are.

 

In the US, when departing a runway, often you will get a clearance to turn to an assigned heading on take-off.  At least at a towered airport and on an instrument flight plan (when VFR the instruction at a towered airport is more likely to have you fly towards an object that is easily seen).  And in other cases you might not get the verbal instruction from ATC, but the SID/DP might have an initial turn to another heading as well.

 

In both of these cases (once again in the US, I can't speak for other countries), you should always fly the runway heading until both of the following have occurred:

 

1. You are at the end of the runway (you have flown the entire length of the runway), unless instructed otherwise.

2. You have climbed to 400 feet above the runway

3.  And for some larger aircraft / airliners, and/or some airlines,  I have heard that a further requirement is gear retracted.

 

Points 1 and 2 are to maintain obstacle clearance (a topic that would take me the entire day to write about).  Obstacle clearance becomes important when you can't see where you are going (in IMC), although is always important.  Point 3 (which never affected me) relates to aircraft performance- don't turn until the drag from the extended gear is gone.

 

So that you can maintain runway heading until these conditions are satisfied, I always have set the runway heading on the HDG and just fly using that as a guide.  Since you rapidly lose perspective of what the runway is as you approach the end of the runway, having it dialed in on the a/c is a help.  And if you go IMC, you will need it anyway.

 

Another benefit is that, with runway heading set prior to entering the runway, you have another verification that you are on the correct runway.  this doesn't help with R/L/C runways, but does help with runways having other alignments.

 

I am writing about GA flying-  lots of things change when you progress up to the "heavy metal", and I'm sure that your question reflects an airliner and not a Cessna  :) .    But in most cases, the "heavy metal" flying is a progression from the smaller GA world,  which is why we spend years in little Cessnas before progressing to more complex aircraft...    but I know that's not what the virtual world is like  :)

 

Thanks,  Bruce.


ASEL, Instrument.

KBJC, Colorado.

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Bruce thanks for your thorough explanation. However I don't fly using ATC, so is it still good practice to set the HDG to the runway you're taking off from? Also what is IMC? 


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Bruce thanks for your thorough explanation. However I don't fly using ATC, so is it still good practice to set the HDG to the runway you're taking off from? Also what is IMC? 

I think Ro has answered the IMC question (thanks)

 

Even if you don't fly with ATC, if you want to ensure a good and uneventful takeoff, flying to 400' AGL (Above Ground Level) and to the end of the runway before turning is still a good idea. I always try to make sure that everything in the aircraft is "working"-  if I get a visual approach clearance on a day that is clear and no clouds, I dial in the ILS (if there is one) and set the runway heading on the HDG knob so that I have instrument references, even if I never use them.  The alignment of the HDG to runway heading on departure is just that- making everything work in the cockpit.

 

A typical departure clearance I would get might be: "Skyhawk 12345, cleared for take-off 29 Right, fly heading 320"  (Note that no altitude is given as that would have been provided to me in my clearance delivery as my "initial altitude").  I have seen pilots set 320 on the HDG-  understandable when you think that that's the clearance you were given-  but the need to get to the end of the runway and up to 400' AGL is implied in the clearance- ATC assumes that you know all of this stuff.  And, for those pilots that set 320 on the HDG (in this example), I have also seen them automatically align the plane with the 320 heading right at the moment that they look at the heading indicator- there's a very strong instinct to "fly to the needle", where they should be flying "runway heading".  

 

I hope that this helps....  I'm off to go hiking on a great Saturday afternoon on the Rockies !  :)

 

Thanks,  Bruce.


ASEL, Instrument.

KBJC, Colorado.

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Aaron-  i'd also like to qualify my response to you.  the 400' AGL altitude to reach is a minimum (and like I stated above, you won't find it on charts).  But at times there may be a greater altitude to achieve than 400' AGL before turning from runway heading, and that will be on a DP chart, or could even be referenced on an airport diagram.

 

Thanks,  Bruce.


ASEL, Instrument.

KBJC, Colorado.

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Great info everyone, so is there a rule as to when to put the landing gears and flaps up after take off? I'm assuming once you reach 400' AGL that's when it happens?


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