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goinv
Topic Author
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Joined: Wed Jan 05, 2005 11:16 pm

You flying a commercial airliner.

ATC give you an instruction to head a certain direction - lets say 185 degrees. However there is a wind factor.

Do you head 185 degrees but then let the wind blow you to say heading 180 or do you head actually 190 degrees so that, after the wind component, you will be heading 185 degrees?

Also, as for speed. If you are told to maintain 200knts. Do you maintain 200knts but then actually go faster / slower depending upon the wind or factor the wind in so that you may have an Ground Speed of 220 knots but a TAS of 200 knots?
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Starlionblue
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### RE: Turn Left Heading 185

Your heading, that is the direction you are going, will be 185. The nose of the aircraft will be offset right or left depending on winds. However your heading will still be 185. The aircraft is moving towards 185, but is flying slightly sideways.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

oly720man
Posts: 5813
Joined: Fri May 21, 2004 7:13 am

### RE: Turn Left Heading 185

 Quoting goinv (Thread starter):Do you head 185 degrees but then let the wind blow you to say heading 180 or do you head actually 190 degrees so that, after the wind component, you will be heading 185 degrees?

This is why aircraft have a rudder. The wind won't blow you to a different heading, it'll blow you sideways so you use the rudder to point the aircraft into the wind so the net effect is that you will head in the right direction.

Illustrated here.

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 Quoting goinv (Thread starter):Also, as for speed. If you are told to maintain 200knts. Do you maintain 200knts but then actually go faster / slower depending upon the wind or factor the wind in so that you may have an Ground Speed of 220 knots but a TAS of 200 knots?

For flight control purposes the aircraft moves through the air and the instruments use that motion to determine the speed, so ATC instructions are airspeed. Groundspeed only, really, tells you when you're going to arrive at the destination. With a strong headwind and a small aircraft you can fly backwards, relative to the ground.
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goinv
Topic Author
Posts: 255
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### RE: Turn Left Heading 185

But surely, if I leave Heathow heading 270 ( lets say this is the direct heading to Washington) and there is a southernly wind, I will end up in New York?

So if ATC send me on a heading of 185 degrees I may end up further left or right of where they intend to send me.
Be who you are, The world was made to measure for your smile. So Smile.

oly720man
Posts: 5813
Joined: Fri May 21, 2004 7:13 am

### RE: Turn Left Heading 185

 Quoting goinv (Reply 3):But surely, if I leave Heathow heading 270 ( lets say this is the direct heading to Washington) and there is a southernly wind, I will end up in New York? So if ATC send me on a heading of 185 degrees I may end up further left or right of where they intend to send me.

Yes, if you did nothing to correct the flight for 8 hrs, or whatever, which is how people get lost. So there are beacons (or recognisable objects) that are aimed for, or the aircraft's inertial navigation system that gives the location of the aircraft and where it's aiming for and the autopilot does the work.

I suppose, more accurately, I should have said head to the right location, not in the right direction, above.
wheat and dairy can screw up your brain

xero9
Posts: 124
Joined: Thu Feb 22, 2007 3:12 am

### RE: Turn Left Heading 185

 Quoting oly720man (Reply 2):This is why aircraft have a rudder. The wind won't blow you to a different heading, it'll blow you sideways so you use the rudder to point the aircraft into the wind so the net effect is that you will head in the right direction.

This would only be true on final. I'm still only a student pilot (a pretty high hour one, mind you), but you would never use your rudder in flight to change the direction of your nose to compensate for wind. This would only create drag. Instead you would crab in to wind.

So to answer the OPs question, your plane would need to track 185 degrees along the ground. The direction your nose points is irrelevant to ATC.

IAHFLYR
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### RE: Turn Left Heading 185

 Quoting xero9 (Reply 5):So to answer the OPs question, your plane would need to track 185 degrees along the ground. The direction your nose points is irrelevant to ATC.

Sorry but that concept is not correct. ATC assigns magnetic headings to fly and that is the heading the crew is expected to turn to and fly. Should ATC discover that heading is not good due to wind they will/should correct it accordingly.
Any views shared are strictly my own and do not a represent those of any former employer.

CosmicCruiser
Posts: 2510
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### RE: Turn Left Heading 185

Don't make it complicated. ATC says fly heading 185 you fly heading 185. As far as ATC is concerned all planes on a 185 hdg are all tracking the same. On most older jets, eg 727, you don't really know what your track is anyway unless you're flying a given course, vor, loc, etc. On newer jets you will see your track as well as the hdg.

 Quoting oly720man (Reply 2):This is why aircraft have a rudder. The wind won't blow you to a different heading, it'll blow you sideways so you use the rudder to point the aircraft into the wind so the net effect is that you will head in the right direction.

Maybe you're just thinking of a x-wind landing.

ANITIX87
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### RE: Turn Left Heading 185

This yields a question on my end.

If you're on HDG mode for the autopilot, and you input 185 into the heading selection knob, will the plane point its nose at 185, or will it point at the angle required for the aircraft to TRAVEL at 185?

Similarly, which heading will be indicated on the flight direction display?

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PapaChuck
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### RE: Turn Left Heading 185

When ATC assigns a heading, don't worry about your ground track. Just fly the assigned magnetic heading. I always try to compensate for the wind when giving vectors, especially for slower aircraft. It basically becomes ATC's job to correct for the wind when they start issuing vectors.

The same applies for speed assignments too. If I assign 250 knots to an aircraft at FL300 with a 100 knot tailwind, I don't expect his groundspeed to be anywhere close to 250 knots. A good controller will compensate for this. Just fly the assigned speed. Hope this helps.
In-trail spacing is a team effort.

CosmicCruiser
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### RE: Turn Left Heading 185

 Quoting ANITIX87 (Reply 8):If you're on HDG mode for the autopilot, and you input 185 into the heading selection knob, will the plane point its nose at 185, or will it point at the angle required for the aircraft to TRAVEL at 185?

check my post....don't confuse heading and track. They're two different things.

N353SK
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Joined: Thu Jun 08, 2006 5:08 am

### RE: Turn Left Heading 185

 Quoting xero9 (Reply 5):So to answer the OPs question, your plane would need to track 185 degrees along the ground. The direction your nose points is irrelevant to ATC.

If ATC tells you "turn left heading 185" they want you to point the nose to a heading of 185. You're probably not the first plane they've seen all day so the controller has a general idea of what sort of wind correction angle you'll need. I know you probably don't fly assigned headings very often as a VFR student pilot, and you're right that eventually the crew will need to worry about ground track over heading.

Moose135
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### RE: Turn Left Heading 185

 Quoting IAHFLYR (Reply 6):Sorry but that concept is not correct. ATC assigns magnetic headings to fly and that is the heading the crew is expected to turn to and fly. Should ATC discover that heading is not good due to wind they will/should correct it accordingly.

Thank you...I know it's been a while since I have been in the cockpit, but I was beginning to wonder if things had changed. If ATC give you a heading, you fly that heading, or you can expect to get another heading change, with a "gentle reminder" about following instructions, before too long.
KC-135 - Passing gas and taking names!

xero9
Posts: 124
Joined: Thu Feb 22, 2007 3:12 am

### RE: Turn Left Heading 185

 Quoting IAHFLYR (Reply 6):Sorry but that concept is not correct. ATC assigns magnetic headings to fly and that is the heading the crew is expected to turn to and fly. Should ATC discover that heading is not good due to wind they will/should correct it accordingly.

Okay I stand corrected. As I mentioned, I am only a student pilot.

I stand 100% behind my rudder statement though.

njxc500
Posts: 219
Joined: Mon Dec 24, 2007 6:47 pm

### RE: Turn Left Heading 185

Could anyone hazard a guess at the percentage of aircraft flying that have the equipment to distinguish between track and heading?

50%??? Take into account GA, and assume the battery in your handheld is crapped out.

If the procedure was to fly your track at 185, how would these "less" equipped airplanes do this? Celestial Navigation I guess could work.....

Oh, don't forget, the compass is that thing your GPS is propped up against in the 172.

Cue the compass jokes.

"Put your compass on 'E' and get out of my airspace."

IAHFLYR
Posts: 4353
Joined: Sat Jun 25, 2005 12:56 am

### RE: Turn Left Heading 185

 Quoting xero9 (Reply 13):Okay I stand corrected. As I mentioned, I am only a student pilot.

Hey we should all be a "student pilot" IMHO, or else you have given up learning and that is not a good idea.
 Quoting ANITIX87 (Reply 8):If you're on HDG mode for the autopilot, and you input 185 into the heading selection knob, will the plane point its nose at 185, or will it point at the angle required for the aircraft to TRAVEL at 185?

As CosmicCruiser has already mentioned, do not confuse the vector heading issued by ATC and a track over the ground, they are not the same.

The times I've heard/issued a ground track it was issued from a waypoint/intersection/NAVAID and the expressed as "depart IAH on a ground track of 185". The aircraft equipped with advance navigation systems would the build a waypoint from IAH bearing 185 degrees at some distance from the fix and off they go. Again, that is not a vector heading.
Any views shared are strictly my own and do not a represent those of any former employer.

bikerthai
Posts: 3976
Joined: Wed Apr 28, 2010 1:45 pm

### RE: Turn Left Heading 185

 Quoting njxc500 (Reply 14): Cue the compass jokes.

"Roger, Roger"

Sorry, couldn't help myself . . .

bikerthai
Intelligent seeks knowledge. Enlightened seeks wisdom.

Fly2HMO
Posts: 7184
Joined: Sat Jan 24, 2004 12:14 pm

### RE: Turn Left Heading 185

Alright, lets set some things straight:

GROUND TRACK: put simply, the direction of the plane over the ground, regardless of where the nose is pointing.

HEADING: where the plane's nose is pointing, always magnetic.

Heading and ground track will NEVER be the same unless you have no wind, or you have a completely parallel headwind or tailwind.

ATC always assigns headings (unless told otherwise, which is extremely rare).

I guess you could say that's pretty much a bearing or radial to be flown.

 Quoting njxc500 (Reply 14): If the procedure was to fly your track at 185, how would these "less" equipped airplanes do this? Celestial Navigation I guess could work.....

You guesstimate, simple as that. If you're flying the 185 radial of a certain VOR and keep getting blown off to either side you find a heading that will keep you centered. There are formulas to figure the winds and the correction angles but frankly once you've flown enough hours you know how much you need without having to do complicated math. If you keep getting blown left off course that means you have a right crosswind, therefore you fly a heading of say, 180 and see if it is enough to keep you from drifting off course.

Here is how you would fly a radial from a VOR, which would mean you would have to keep a constant ground track to remain on said radial:

[Edited 2010-08-26 10:04:06]

N353SK
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Joined: Thu Jun 08, 2006 5:08 am

### RE: Turn Left Heading 185

 Quoting xero9 (Reply 13):I stand 100% behind my rudder statement though.

And you're right.

 Quoting njxc500 (Reply 14):Could anyone hazard a guess at the percentage of aircraft flying that have the equipment to distinguish between track and heading?

100%, assuming the aircraft is flying in visual conditions. The equipment? Eyeballs. But any sort navigation equipment (VOR, NDB, GPS etc.) use ground track and the pilot can compare heading to ground track.

SPREE34
Posts: 1750
Joined: Tue Jun 29, 2004 6:09 am

### RE: Turn Left Heading 185

 Quoting CosmicCruiser (Reply 10):don't confuse heading and track. They're two different things.

DING!

Heading is from the compass/DG. Track is not.

PapaChuck
Posts: 111
Joined: Mon Aug 16, 2010 2:51 pm

### RE: Turn Left Heading 185

Think of it this way:

A pilot navigating from point A to point B will have to apply some kind of correction for the wind if they expect to stay on their desired ground track. Whether they use GPS, VORs or the good old E6B to figure it out doesn't matter. The pilot assumes responsibility for their own navigation and makes corrections to their track as needed.

However, as soon as ATC issues a vector, all that goes out the window and ATC becomes responsible for navigation. This remains the case until the pilot is informed otherwise, hence the term "resume own navigation." While on a vector, just fly the magnetic heading assigned and let ATC worry about the rest.
In-trail spacing is a team effort.

IAHFLYR
Posts: 4353
Joined: Sat Jun 25, 2005 12:56 am

### RE: Turn Left Heading 185

 Quoting Fly2HMO (Reply 17):I guess you could say that's pretty much a bearing or radial to be flown.

You could say that however, it's been used to have aircraft fly a very precise repeatable route over the ground, almost exactly the same as an RNAV leg between two waypoints not is not a charted RNAV procedure.
Any views shared are strictly my own and do not a represent those of any former employer.

Fly2HMO
Posts: 7184
Joined: Sat Jan 24, 2004 12:14 pm

### RE: Turn Left Heading 185

 Quoting IAHFLYR (Reply 21): You could say that however, it's been used to have aircraft fly a very precise repeatable route over the ground, almost exactly the same as an RNAV leg between two waypoints not is not a charted RNAV procedure.

Indeed. To further expand on my previous post, even the most basic GPSs I've used allow you to use pretty much any waypoint in the GPS database (airports, VFR reporting points, actual waypoints, etc) as a virtual navaid (OBS mode) and you can create radials from said points. Very useful when you have to hold over an unpublished hold.

[Edited 2010-08-26 13:37:53]

Viscount724
Posts: 19316
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### RE: Turn Left Heading 185

 Quoting oly720man (Reply 2):This is why aircraft have a rudder. The wind won't blow you to a different heading, it'll blow you sideways so you use the rudder to point the aircraft into the wind so the net effect is that you will head in the right direction. Illustrated here.

And here:

bri2k1
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### RE: Turn Left Heading 185

The wind will generally affect planes in the same vicinity the same way, so ATC gets pretty good at issuing headings that make the plane end up where they want it. As with many tasks, approach controllers tend to have the most fun with it, because they have planes descending, slowing, and turning from a bunch of different directions. If there's a strong wind higher up that shears to a different speed or direction down lower, it can get a little exciting to see planes quickly converging, but armed with the knowledge that the wind will change and slow down the rate of convergence, things tend to work out.
Position and hold

Mir
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### RE: Turn Left Heading 185

 Quoting Starlionblue (Reply 1):Your heading, that is the direction you are going, will be 185. The nose of the aircraft will be offset right or left depending on winds. However your heading will still be 185. The aircraft is moving towards 185, but is flying slightly sideways.

You've got heading and ground track confused.

 Quoting ANITIX87 (Reply 8):If you're on HDG mode for the autopilot, and you input 185 into the heading selection knob, will the plane point its nose at 185, or will it point at the angle required for the aircraft to TRAVEL at 185? Similarly, which heading will be indicated on the flight direction display?

The plane will point the nose at 185, and the ground track will be whatever it is. If the autopilot is in TRK mode, then the nose will point at whatever is necessary to fly a ground track of 185.

Think about it from ATC's perspective: it would really suck to have to give different headings to different aircraft depending on their capability to determine ground track. Much easier to just apply a consistent correction to everybody.

-Mir
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Starlionblue
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### RE: Turn Left Heading 185

I did. I stand very much corrected.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

fly727
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### RE: Turn Left Heading 185

If you are flying a heading issued by ATC there should be no correction made, unless it states you to navigate to certain point once that you are able, by your own navigational means.

Quite often, during vectors to an approach or for traffic spacing, ATC (radar able) will assign you headings to fly which corresponds more or less to a track he or she desires to take you. If the wind is strong enough they will notice the drift and will reissue a correction heading.

RM
There are no stupid questions... just stupid people!

IAHFLYR
Posts: 4353
Joined: Sat Jun 25, 2005 12:56 am

### RE: Turn Left Heading 185

 Quoting fly727 (Reply 27):Quite often, during vectors to an approach or for traffic spacing, ATC (radar able) will assign you headings to fly which corresponds more or less to a track he or she desires to take you. If the wind is strong enough they will notice the drift and will reissue a correction heading.

Key is "a headings to fly which corresponds more or less to a track he or she desires"......still a vector is a magnetic heading as you suggest, not a track over the ground.
Any views shared are strictly my own and do not a represent those of any former employer.

Glom
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Joined: Sat Apr 23, 2005 2:38 am

### RE: Turn Left Heading 185

 Quoting goinv (Thread starter):Do you head 185 degrees but then let the wind blow you to say heading 180 or do you head actually 190 degrees so that, after the wind component, you will be heading 185 degrees? Also, as for speed. If you are told to maintain 200knts. Do you maintain 200knts but then actually go faster / slower depending upon the wind or factor the wind in so that you may have an Ground Speed of 220 knots but a TAS of 200 knots?

The basic aircraft instrumentation includes an ASI, which gives indicated airspeed, not groundspeed, and a HI, which gives heading, not track. ATC instructions all assume pilots will use these. The controllers will think, observe and compensate in giving their instructions to achieve the desired tracks and groundspeeds.

 Quoting Starlionblue (Reply 1):Your heading, that is the direction you are going, will be 185. The nose of the aircraft will be offset right or left depending on winds. However your heading will still be 185. The aircraft is moving towards 185, but is flying slightly sideways.

Wrong way round. Heading is where you're pointing. Track is where you're going.

 Quoting oly720man (Reply 2):This is why aircraft have a rudder. The wind won't blow you to a different heading, it'll blow you sideways so you use the rudder to point the aircraft into the wind so the net effect is that you will head in the right direction.

When you are trying to fly a track-made-good by compensating for wind drift, you turn the aircraft into wind by the appropriate crab angle. That uses aileron with rudder to maintain balance. Of course, if the turn required is small, sometimes giving a little kick of the rudder is better.

 Quoting njxc500 (Reply 14):Oh, don't forget, the compass is that thing your GPS is propped up against in the 172.

Which now misreads because you've put an electronic device next to it.

 Quoting Mir (Reply 25):Think about it from ATC's perspective: it would really suck to have to give different headings to different aircraft depending on their capability to determine ground track. Much easier to just apply a consistent correction to everybody.

Bingo. It doesn't much if everyone is a little off, provided everyone is a little off together. That's the reasoning behind the standard pressure setting. Once you stop worrying about obstacle clearance, it is much safer for everyone to have the same idea of what is 5000ft, even if it isn't actually 5000ft.

swiftski
Posts: 1837
Joined: Tue Dec 19, 2006 6:19 am

### RE: Turn Left Heading 185

 Quoting ANITIX87 (Reply 8):If you're on HDG mode for the autopilot, and you input 185 into the heading selection knob, will the plane point its nose at 185, or will it point at the angle required for the aircraft to TRAVEL at 185?

In HDG mode you will get your nose point at 185.

If it's in NAV mode and you set, say, 185 radial on a VOR it will capture and hold the track 185, using whatever heading needed.

zeke
Posts: 16085
Joined: Thu Dec 14, 2006 1:42 pm

### RE: Turn Left Heading 185

 Quoting goinv (Thread starter):Do you head 185 degrees but then let the wind blow you to say heading 180 or do you head actually 190 degrees so that, after the wind component, you will be heading 185 degrees?

Generally, keep it simple, if ATC asks for a heading, just turn and fly that indicated heading, does not matter if you are flying manually or using the autopilot.

As with most things aviation, with the general rule there is the exception, that is where ATC asks for "fly runway heading". For most countries in the world this means fly the heading as usual, in some others it means fly the extended runway centreline (runway track).

 Quoting goinv (Thread starter): Also, as for speed. If you are told to maintain 200knts.

You fly the indicated speed or mach number asked for by ATC.

Notice I mentioned indicated both times, ATC expects the pilots to fly the indicated airspeed, altitude, flight level, or speed.

 Quoting goinv (Reply 3):So if ATC send me on a heading of 185 degrees I may end up further left or right of where they intend to send me.

They will give you another vector or instruction.

 Quoting IAHFLYR (Reply 6):Should ATC discover that heading is not good due to wind they will/should correct it accordingly.

Correct

 Quoting CosmicCruiser (Reply 7):Don't make it complicated. ATC says fly heading 185 you fly heading 185. As far as ATC is concerned all planes on a 185 hdg are all tracking the same.

Correct, assuming the wind is constant at all levels.

 Quoting ANITIX87 (Reply 8):If you're on HDG mode for the autopilot, and you input 185 into the heading selection knob, will the plane point its nose at 185, or will it point at the angle required for the aircraft to TRAVEL at 185?

The indicated heading will be 185, on some aircraft, like Airbus FBW, they have the ability to fly a constant track across the ground as well as a constant flight path angle vertically, which allows the aircraft to fly a pseudo "ILS" style path horizontally and vertically regadless if the wind speed and direction changes with level.

 Quoting ANITIX87 (Reply 8):Similarly, which heading will be indicated on the flight direction display?

 Quoting njxc500 (Reply 14):If the procedure was to fly your track at 185, how would these "less" equipped airplanes do this? Celestial Navigation I guess could work.....

All pilots with an instrument rating would be able to make their own corrections to heading to fly instrument approaches. Instrument approaches be it a holding pattern, NDB/VOR/GPS/LLZ/ILS approach are based upon flying prescribed magnetic or true tracks. Pilots make adjustments to their headings from cues from their navigational instruments to fly these constant tracks.

So when ATC asks for direct to a navaid, waypoint, or to commence a hold/instrument approach, they are asking the pilot then to start making wind corrections.
“Don't be a show-off. Never be too proud to turn back. There are old pilots and bold pilots, but no old, bold pilots.” E. Hamilton Lee, 1949

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