Vectors by ATC (747-400F with all updates)

[lostmoon 0]

Gents,Have any of you experienced the following, and if so, have any of you found a reason/workaround for it? On VATSIM last night, we were vectored away from our planned LNAV path for spacing. We were passing 14,000 for 7,000 on a heading of 358 degrees, when ATC asked us to take a right turn to a heading of 140 degrees. We proceeded to turn the heading bug to the right for the new assigned radar heading, and pressed the HDG button. With HDG SEL on the FMA, instead of turning right, she made her way to the left. Very disconcerting to the ATC controller who chastised me for endangering others in ZLA aerospace. I could not get her to turn right using the HDG SEL mode under A/P authority, so I ended up disconnecting it, and hand flew her to the correct heading. Only then when we were established on the heading, I was able to re-engage A/P for her to obey the HDG SEL. What could be the cause for this behaviour, and what suggestions do you have to correct it?Thanks guys,Tomas

[downscc 1,327]

The difference between 358 and 140 is only 142... I'm surprised that otto was going around the long way. If a heading change exceeds 180 deg then this will always happen. Regardless, the fix is to set an initial heading change of less than 90 deg to set up the turn, then when the turn is established move the bug around to the assigned heading. In your case, tracking 358 and vectored to a heading of 140, set the heading to 90 until your right turn approaches the midpoint (about 45) increase your heading to 140. She oughta steer on around as expected.In real world flying, sometimes I will force a shallow turn by constantly and slowly increasing the heading (in a right turn) keeping it about 10 deg ahead of the plane until I reach the desired heading. But, in the real world I don't have a max bank control like on the MCP.

[lostmoon 0]

Dan,My sentiments exactly. You can imagine the surprise when she started banking left. The HDG bug was not even close to the 180 degree mark. Your suggestion is excellent, and I will taper off a few degrees to get her to move in the proper direction. I'll report back with the results.Thanks DanTomas

[cowpatz 243]

The easiest way to avoid these turn ambiguities is to press the HDG SEL button first and then turn (in the direction of turn) to the desired heading. Make this movement instinctive. The issue you describe happens in the real world too and it sure makes everyone sit up and take notice.CheersSteve

[downscc 1,327]

Good idea but doesn't work for me because my heading bug is where ever I left it last time I was in heading mode. So, before pressing the HDG button, gotta make sure it's set to either the current heading, or something close to it in the direction of the turn you're gonna make. This is kinda what I recommended to begin with. Nothing wrong with your idea, just different way of doing the same thing.

[Chaos81 110]

>before pressing the HDG button, gotta make sure it's set to>either the current headingAs it should be already. ;)

[downscc 1,327]

"As it should be already"Mike: I am missing something... why should the heading selection be the same as your current track when you are flying coupled to LNAV? This is the case most of the time that ATC issues an initial vector for whatever reason.

[cowpatz 243]

Couple of reasons the heading bug should be alligned with the current aircraft heading Dan (not track).1. When ATC suddenly ask you what your heading is it is right there on the MCP. Ever noticed the delay in response to a controller asking a glass cockpit aircraft what it's heading is? Track is easy ....heading takes time. When ATC do give you a heading to take up the orientation is easy and the heading bug easier to find. Hard to locate sometimes when facing behind you. There is also minimal delay to turning onto heading.By the way a DME distance is another nasty question to be asked in this aircraft!!!! Another pregnant pause as you try to figure what DME is indicating what and from where!!!!2. In an emergency to turn off track is just a simple press and turn not find, position, press and turn.None are major issues really just more good housekeeping rules.By the way well done on the procedure turn. Haven't flown it yet but will do.CheersSteve

[downscc 1,327]

I usually just give them my track.. "tracking 144" and they've never asked for my heading instead. Like I said before... just a different way of doing the same thing.

[lostmoon 0]

Steve,Many thanks for the recommendation. I certainly will do that. I try to be aware and keep the HDG bug on the same heading the a/c is on. good practice as you've mentioned.thank you,tomas

[cowpatz 243]

>I usually just give them my track.. "tracking 144" and>they've never asked for my heading instead. Like I said>before... just a different way of doing the same thing. Just be careful giving track as a heading. Only when there is no drift are they the same. In some cases they could differ by 20 degrees or more. This is important when vectoring aircraft for separation. ATC need to know your current heading. The issue is complicated if one aircraft gives a track and another a heading.There are some procedures where a heading must be specically flown ie. RWY 24 0r 25 departures off LAX. A heading of 250 degrees must be flown not a track of 250. This is very important for parallel runway operations to maintain separation. If there is a crosswind ATC expect you to be blown off course but both departing aircraft will be blown off track and therefore maintain separation.RgdsSteve