Airbus Energy Circle

[Bagoongathipon]

Can someone elaborate the airbus definition of Energy Circle

It is the required distance to land.. but what does that mean.. can someone expound on this one.. thanks

[TyroPicard]

Airbus don't expand on it.. it is the distance required to go down, slow down, configure the aircraft and land at destination. In a straight line, not taking account of the F-PLAN route. Not displayed in NAV, only in HDG or TRK lateral modes.
How to use it? Imagine a straight line to the runway, and a/c on the centreline.. if the energy circle is beyond the runway, you have too much energy and will have to take appropriate action. If the circle lies between you and the runway - no problem.

[FLEXPWR]

Hi,

It's the required distance to ground (AAL?) based on current altitude/speed, that the A/C will need to decelerate on a standard schedule, get configured, and stabilised by 1000' for landing.

Not sure this is the exact full explanation, but that's what I remember, I'll be back in the books again soon.

Flex

[Torque2]

ENERGY CIRCLE
The energy circle is a green arc, centered on the aircraft’s position and oriented towards the current track line.
It is displayed on the NDs during descent, when HDG or TRK mode is selected. It represents the required distance to land from
the aircraft’s position down to airport elevation at VAPP speed, considering all speed constraints on the vertical profile.

Guess thats about it.

[hetfield]

In my bus it was yellow.
That's why we called it the banana.

[Microburst2002]

They don't write much about it, in the FCOMs

Does it take into account...

actual airspeed or econ speed, or .78/300/250?
actual wind or fmgs inserted wind?

I think it is quite accurate. It usually coincides with my own calculations within a couple of miles, a few more at the TOD, within one mile below 10,000. If it doesn't it means I haven't accounted for unusually heavy or light or slow or fast or windy.

[John Citizen]

How do you use this energy circle ?

What if you are being radar vectored and not heading directly to the runway ?

[FLEXPWR]

Hey, the energy circle is a nice additional tool, but it doesn't means pilots have to stop thinking...

You can make up a very good estimate, while being radar vectored, you can say you need XXX track miles to touch down, just by looking at the display.

Whatever the case may be, I like to keep 300 feet per mile for my own calculations, so I know it fits the picture (i.e. 3NM final= 900', etc)

Flex

[Bagoongathipon]

:)

thanks for the info..

lastly about descent..

We have this formula to estimate the TOD: altx3 + 10,

but have you heard of the formula

(somethhing like this)

(airspeed-200)+altitudex3 = Trackdistance on the given altitude.

Can someone confirm if this formula is correct.

Thanks

[Busserday]

The most trustworthy formula is only as good as the data inputs. Wind, ISA deviations to temperature and pressure, aircraft weight, velocity at start of descent, velocity at end of descent, specific aircraft capabilities, etc., etc., etc. A complex formula is as likely to give as good consistant results as a simple one with a little mid descent correction required often as not for both.

I always found the 3 to 1 with a mile per 10 knot decel was ball park enough to add a little tail wind or subtract a little for head wind to, try dividing the wind by 3, a normal descent is around 20-30 minutes but the wind usually decreases as you go down. If it's really cold add a few, if it's really hot subtract .037 nm per degree K above 425 degrees. Then go back to the first calc. and compare.
BD

[Jimmy Hoffa Rocks]

dont trust it, it can and will be wrong, cross check it

[Akrapovic]

Personally - I never use the energy circle - it has no idea about winds aloft and the methods listed above are just as reliable.

[planeboy_777]

In FCTM it says Energy Circle, (displayed if HDG or TRK modes and
indicating the required distance to descend, decelerate and land from present position)
and In Fcom its written Gliding at Vapp from PPos till ground level..