I'm sure this can be answered very quickly as I should know the answer :unsure: When given an instruction for a heading of 210 by ATC, do I follow the disply on the MCP or the one on the ND, which is often different, presumably because it's due to the wind aloft or magnetic track? So, which one guys...? Cheers...

Heading is Heading. ATC needs to account for wind corrections.

If ATC tells you to fly 210, just enter 210 on the MCP, except when they specify TRACK.

Thanks for the speedy reply Thomas, appreciated.

Navdisplay! the MCP should match it but your flying on the heading on the navdisplay. I dont even look at the MCP heading. I rotate the HDG knob to the heading assigned on the navdisplay. Or an HSI. Small aircraft equipped with HSI doesnt even have a heading readout. You turn the knob on the hSI to the heading indicated. I understand this is 737 but the practice is the same.

Interesting.... two alternatives!

Howard, it probably insignificant in a MCP equipped aircraft and the answer is probably both. Affirming heading on the Navdisplay. In all logic they SHOULD match. I look at it like you care your are flying on the heading the ND is indicating (Which is a high tech compass) not the AP/MCP. I was taught in smaller aircraft to read the ND or HSI first and I believe that is a good practice..

 

Some MCP's, like the CRJ, wont have the HDG reading on it. You have to go by the ND needle. This kinda confirms reading the ND would be good practice.

I simply set the heading on the MCP. I never ever change the heading on the MCP to make up for winds or whatever. If ATC tells you to fly a heading of 210 you enter that in the MCP and that's it. I think the 737NGX AP is clever enough to make sure you are actually flying that heading, whatever the wind is. And if you should stray off, ATC will tell you which heading to take to make up for it.

Navdisplay! the MCP should match it but your flying on the heading on the navdisplay. I dont even look at the MCP heading. I rotate the HDG knob to the heading assigned on the navdisplay. Or an HSI. Small aircraft equipped with HSI doesnt even have a heading readout. You turn the knob on the hSI to the heading indicated. I understand this is 737 but the practice is the same.

 

No, you're confused between heading and track. Heading is where the nose of the aircraft is pointing with respect to magnetic north (unless you're flying in polar regions, in which case it'll be true north). Every aircraft, even a Cessna 150 is capable of following an instruction to fly a heading even without an HSI (just look at the DG/compass).

 

Interesting.... two alternatives!

 

If ATC tells to you fly a heading, that's the number you put into the MCP, simple!

Rendi.

you don't make any sense... even on a small plane with only HSI, you can't fly a radial if both HDG and OBS are the same, with a crosswind or so....

I simply set the heading on the MCP. I never ever change the heading on the MCP to make up for winds or whatever. If ATC tells you to fly a heading of 210 you enter that in the MCP and that's it. I think the 737NGX AP is clever enough to make sure you are actually flying that heading, whatever the wind is. And if you should stray off, ATC will tell you which heading to take to make up for it.

 

Heading: Where your nose is pointing

Track: Where you are actually going.

 

Wind will change your track, but never your heading. If ATC tells you to fly a heading (they usually do) you don't have to compensate for wind, just point your nose in the ordered direction. If ATC tells you to fly a track you need to compensate for wind (i.e. turn slightly into the wind) in order to make sure you're actually flying in the correct direction.

Thanks for all the explanations fellas. I guess it wasn't such a dumb question after all!

It sure wasn't. But keep in mind, many commercial airliners have two different options, either at purchase(eg. 737) or via a switch/ button(eg. 777). You can have the ND displaying Track or Heading, but in the 737 the MCP will always indicate your heading, not your track.

So when ATC tells you to fly heading 210, they are already correcting for winds, you don't need to.

 

I'm not sure whether the MCP on something like the 777 can display HDG and TRK, I'm sure somebody will chime in with this info.

Cheers Thomas. The reason why I ask, is that I was on a flight today from EGKK to LPFR, with the MCP set in LNAV mode following a flightplan generated by PROATC, when halfway through the flight ATC instructed me to make a course change that was different to what was showing on the MCP, this meant I had to engage HDG select to follow the instruction. It was only a 5 degree change, but nevertheless different to what I was flying in LNAV mode. I am a little confused why they would have given that instruction....(?)

It sure wasn't. But keep in mind, many commercial airliners have two different options, either at purchase(eg. 737) or via a switch/ button(eg. 777). You can have the ND displaying Track or Heading, but in the 737 the MCP will always indicate your heading, not your track.

So when ATC tells you to fly heading 210, they are already correcting for winds, you don't need to.

 

I'm not sure whether the MCP on something like the 777 can display HDG and TRK, I'm sure somebody will chime in with this info.

 

I think what you're talking about is "track up" or "heading up" on the ND. This is maintenance set rather than pilot option. The ND still shows the heading triangle and track line that you're used to, the only thing that changes is which one is shown directly at the top of the display and which one displaces left/right when wind means they're no co-incidental.

 

The difference between the 737 and the 777 is the "heading" dial on the MCP. On the 737 this can only be used to set a heading. On the 777, a button on the MCP allows the pilot to switch the "heading" dial between heading and track. This is separate to the track/heading option.

I'd use the MCP since:

1. Your hand will be there, anyways

2. You'd point to it in a two-crew environment.

 

For little corrections enroute, I'll just "marry the bugs" on the ND.