“Try not to crash land on the airstrip below on this crazy steep descent overlooking Hawaii's North Shore.”
— Lost Justpastnowhere
Mountain bike access in this area is under constant scrutiny and will only continue if bikers avoid skidding corners and respect other trail users.
You probably don't want to hike up this trail with your bike. This means you'll be accessing it after a long climb from either Mokuleia Firebreak Road
or Kuaokala Firebreak Road
. Consider the full Peacock Flats
Loop if you've got time and stamina.
Kealia descends down to the coast above Dillingham Field. The descent seems to get more and more steep as you near the airfield. The first 1.5 miles is not too bad - a well earned descent on a wide trail. When you get to a clear viewpoint at about the halfway mark, (you'll know when you get there), stop to enjoy the view because you won't want to take your eyes off the trail after that. This is also a good point to strap on any armor if you've carried it all this way and make sure your will is up to date.
Once you depart the viewpoint, it seems like you're riding on the edge of a cliff until you reach the airport. This portion of Kealia trail is a narrow singletrack with probably 20 sharp switchbacks to be negotiated along the way down and all at 20-30% grade with some rocks thrown in just for good measure.
The views of Dillingham Field, the North Shore (which often has huge waves for advanced surfers), and the expanse of the Pacific Ocean are continuous along the top half of the descent and quite spectacular if you can take your eyes off the trail. Don't take you're eyes off the trail for too long though, because a fall could send you careening over a cliff and quite a ways downhill and any flying should only be done from the airport.
Also keep in mind, this portion of the Kealia trail is popular with hikers so that is another reason to keep it under control.