FMC ISA Deviation and Intersect

[BaBene]

Hi,

I've been playing around with the FMC lately and noticed two small thins that seem to be wrong from my point of view

PERF INIT -> ISA DEV:

1.) When entering an ISA DEV of 0°C the FMC reads 32°F  0°C. Well 0°C is 32°F but what matters here is the deviation and shouldn't the deviation be 0°F as well?

2.) When entering a deviation =! 0°C the T/C OAT gets adjusted correctly, but when deleting the deviation with the DEL key the T/C OAT stays the same (i.e. does not revert to ISA OAT)

TAKEOFF REF -> INTERSECT

First of all I'm struggling to find a good explanation of what INTERSECT actually means and how to enter the data correctly. From my understanding it's used for intersection take offs (as the name suggests ;)) But then I don't really understand the format ---/-----. Could someone clarify this for me?

1.) Basically the INTERSECT field just takes almost everything you throw at it. For example: Just press delete and click on intersect, it reads DEL/----- then. Or you might want to attempt to enter something after the "/" by entering "/200" for example, it then reads "/20/------".

 

Hope this helps!

 

Best regards,

BaBene

 

[byte512]

Just noticed the following on a flight as well:

On 31.5.2016 at 11:39 PM, BaBene said:

1.) Basically the INTERSECT field just takes almost everything you throw at it. For example: Just press delete and click on intersect, it reads DEL/----- then. Or you might want to attempt to enter something after the "/" by entering "/200" for example, it then reads "/20/------".

I entered a 0 in intersect, thought to myself, "i don't really know what this does, let's delete that again."

Result:

I hope, that this image is helpful.

Regards, byte

Edited June 3, 2016 by byte512
clarified quote

[BaBene]

@byte512 Thank you for supplying the Image, I guess I should've done that in the first place

[Litjan]

The intersect field will take data for a runway intersection takeoff - either the displacement in meters, or the name of the intersection.

In the real plane the position of the FMS will update to the runway beginning when you press the TOGA buttons. If you take off from an intersection, this update would be erroneous, since you are not actually at the beginning. So you can enter an intersection value (i.e. 900m) and the updated position will be correct.

If the FMS position is being fed GPS data, this update will not be taken into account - so it does not matter if you enter anything or not. The IXEG 737 will always have GPS updating, so entering anything (or nothing) into this field will have no effect.

Cheers, Jan