Range To Altitude Arc
New to us in update 19.4 we have a few helpful features to us to assist with our planning as a pilot. For those who may have struggled or had issues with climb and descent planning, this topic is just for you. Behold, the Altitude Arc. In aviation, we as pilots commonly refer to this as the “Banana”. Without further-ado, let’s discuss, what is this thing?
The Altitude Arc is a visual curved line, blue/cyan in color, on our map that depicts where we will reach our target altitude given our instant:
- Vertical Speed
- Current altitude
What does it look like?
Image of the Altitude Arc
If you look closely on your end, you will notice that this line is slightly curved; hence, the name “the Banana”.
So, how does this work?
Before departing the origin airport, set your altitude select to your desired altitude. This may be your cruise altitude or a step altitude that ATC gives you. For now, we’ll just call our cruise altitude to order. In this example, 8,500ft.
After departure and above 400ft agl engage your autopilot. On your map, you’ll find that this blue arc will scale away from your aircraft quite rapidly. This is normal.
Open up your map/minimap and search for the altitude arc. This will always be off the nose of the aircraft. Even if have a turn in your flight plan, the arc will not follow the flightplan. It will stay at the 12 o’clock position relative to your aircraft.
Adjust your Vertical Speed and/or Airspeed to move this arc. The closer the arc is to your aircraft, the steeper the climb will be, and a higher engine power demand will be needed.
As mentioned before, this tool is useful during the climb and descent phases of flight. If anything, you will find this useful during descent.
Say you’re at FL350 in an airliner and you’re looking to get down to FL180 (the max altitude you should be contacting Approach at). As you begin your descent, you’ll dial in 18,000 into your ALT select. You’ll then want to set an adequate VS that will get you down in time. In a descent, speed is king. You’ll want to reduce your speed to assist the most in a constant rate descent. If winds are relatively calm, you won’t have to mess with the VS or SPD very much. The altitude ARC should move very little but it is expected.
- Looking to cross a waypoint at a certain altitude? Set the altitude you’d like to cross a waypoint at in your Autopilot controls. Adjust your speed and VS to move the altitude arc (banana) over the waypoint you wish to cross at.
I've set up my autopilot for the climb/descent but can't find this altitude arc.
Perhaps your VS is not steep enough. Because you’re so high with such a shallow descent, your arc may be 300nm in front of the aircraft. Steepen the descent/climb a little bit and zoom in on your map. Its there! 🙂
My altitude arc is jumping around a lot (getting further and closer without me touching anything) Is this normal?
Yes, it is. The reason for this is the change in the VS as well as your groundspeed. Because the autopilot doesn’t hold a solid VS, it tends to fluctuate some.
Will the altitude arc work when the autopilot is off?
No. It will not work when the autopilot is off. The autopilot will need to be enabled for this to occur with VS selected and an ALT set.
What will happen to the altitude arc when I change the altitude while I'm climbing or descending?
The arc will either get further or closer to you depending on what you’re doing. If you’re climbing to FL340 and want to stop at FL300, the arc will be closer to you because you’re closer to FL300 than you are FL340. The opposite is true in a descent. If you’re descending out of FL340 for FL280 but would like to go down to FL180, the range arc will scale further out and away from your aircraft. Why? Because you have a lot more altitude to lose, you’ll end up covering a lot more distance and that distance = time.
The blue/cyan line that extends from your aircraft nose when changing the heading is the heading line. This will be depicted on your map for no more than a few seconds after a heading is set. This line will reappear when you change the heading.