Lowest Point of Return (LPR)
As I have stated many times in the past, the essence of safe ballooning lies in the approach to landing. The touchdown (landing) is usually a straightforward maneuver if the approach is executed properly. Approach techniques vary with the wind speed, direction, and the array of obstacles in the vicinity of the intended landing area. High wind landings into a field with reasonable length and no obstacles require a long, shallow glide slope with prime emphasis on clearing the highest obstacle in the path to the field with a slight down angle and as close as possible. High wind landings in more congested areas and those with tall trees require a similar approach to the one described above except that once the upwind obstacles (treetops etc.) are cleared, the balloon should be forced into a steeper descent momentarily (quick vent), decelerated (hard burn), and ripped out before ground contact. This should all be in one fluid motion (yea, right). The moderate to slow wind landings require a controlled descent into the intended landing area with the pilot cognizant of the highest obstacle in the both the path to landing and the abort path.
During instruction, I have had students try any number of techniques when attempting to land. Landing risks escalate significantly when the student “commits” to a landing from too high while in the vicinity of obstacles. My idea of obstacles in the vicinity and theirs is often completely different. This concept has so many variables that it is very difficult to teach. In general, in winds with “flow” (3-6 mph), the pilot must be aware of obstacles at least 20 degrees in each direction of his/her dynamic path. What I mean by dynamic is that if the balloon’s direction turns 20 degrees left on a descent, the pilot must continue to visually pan at least 20 degrees further left (a net 40 degrees off the original path). If a pilot fails to do this, he/she will often be faced with either a collision or sudden landing abort. With this in mind, at what point does a pilot “commit” to a landing amongst obstacles so that the risk of collision is minimized? The answer is to find and acknowledge the “Lowest Point of Return” in every situation.
The LPR (lowest point of return) is that altitude, attitude, and position where the balloon can still fly out of harm’s way if necessary (without radical burning). It is determined by the balloon’s direction (relative to obstacles), attitude (descending, level, climbing), height of the objects in its path, wind speed and burner response. The LPR is critical because it is from there that the lowest risk landings are initiated. Unfortunately, most of the variables defining the LPR are very fluid and can change quickly. In some approaches, the balloon is in the LPR for only a moment. It’s crucial for the pilot to recognize this moment and make the land/no land decision immediately if that is the intention. At other times, it may be possible to stay in the LPR for 20-30 seconds or more while descending (slowly) through an obstacle path. The object for the pilot trying to land is to stay in this LPR zone as long as possible in each approach into congestion hoping that the LPR altitude gets closer to the ground and a low risk landing can be initiated.
The big questions is how does a pilot maintain focus in a congested area approach and notice his/her position relative to the LPR? The answer is simple. Practice! How do you practice this? The exercise that paints a clear picture of precisely where the LPR is in each approach is dipping down between obstacles (eg tree lines across a fairway) with the intention of going as low as possible while still executing a controlled exit over the far set of trees. What you will notice on your first try is that your focus is 95% on the far tree line and 5% or so on the low spot in between. With more practice, the timing required to clear the highest downwind obstacle at all points during the descent becomes second nature allowing you to safely fly the balloon lower and lower within the congested area and still have a way out. After developing this skill to an advanced level, a pilot can eventually reach and maintain flight at the “absolute LPR” (the very lowest point of return regardless of skill). Once that skill level is reached, the only variable becomes the performance of the balloon. The real “magic” of the maneuver occurs when your skill level allows a descent and flight down at the absolute LPR and you find wind shifts that allow very low risk, opportunistic landings that you would have never expected at the start of the descent. A common scenario illustrating this “magic” is making a landing in a small opening in a heavily treed area with a good breeze at tree top level. The first time a pilot tries this, it doesn’t look makeable based on his/her groundspeed above the trees. However, once the balloon descends low enough to penetrate the slower air below the tree tops, there is suddenly plenty of time to land. The LPR is changing dynamically with the descent through slower wind speed, eventually making the absolute LPR the ground in many cases.
LPR levels around other types of obstacles very often offer surprise safe landing sites as well. Imagine a junkyard full of rusted steel and old cars. If the wind is gentle enough (3-5 mph), I always descend between the junk piles to the LPR just to see what will happen. Quite often, I get a favorable turn and a little slowdown over a small open space. If I had to put a number on it, I would say that in the course of maintaining my flight at the absolute LPR in a junkyard, the balloon would take me over a “no-brainer” pop vent/tap ground landing 60% of the time. I’m speaking of an area that from the initial descent looked more like a balloon graveyard than an opportunity to land.
Practicing ever lower descents into congested areas will begin to point out the single key obstacle to focus on (avoid) at any given moment. Once the ability to isolate this key single focal point from all of the obstacles is developed, your definition of a “congested area” will change dramatically. You don’t need to worry about looking for the landing spots while flying at the LPR. They will be obvious when they emerge because you will be right on top of them at a very low height.
Happy Tight Landings!