Return to Article Index

Using Flight Plans and a Primary Path

A flight plan is a pre-calculated set of guidelines a pilot will stay within during a flight. Wind and terrain are taken into account and based on these and knowledge of the site, an experienced pilot or instructor can use the plan to manage risks and optimize flights for safety from launch to landing.

Instructors provide a flight plan on almost every flight a student takes during training. In the beginning, these plans are ultra simple and adjustments are not necessary. Later, when lift, sink and flying tasks affect the flight, adjustments become necessary and are incorporated as part of the plan. The students learn to understand the reasons for adjustments and how the flight plan is designed to minimize risks and hazards.

Every time you fly, not just in lessons, a flight plan needs to be in your head with all of the elements that a flight plan can provide. Even cross country pilots plot out their courses near mountains with knowledge of bail outs along a possible flight path.

A primary path is a line from the launch to the landing zone that optimizes terrain features and lift areas to maximize glide and reach the LZ as easily as possible. It is an imaginary line that one flies over in relation to the terrain features below. The primary path is described as part of the flight plan. Most sites have terrain features like ridges that run between the launch and LZ and the flight plan will often stay above some of these ridges on the way to the LZ. The reasons for this is that lift and thermals release from the higher terrain.

Terrain features and vegetation coverage also play a part in how a flight plan is designed. Based on the wind direction and velocity, there can be areas where dynamic (aka ridge lift) will help you maintain altitude on the way to the LZ. Over flatlands and on the way to an LZ, a flight plan can icorporate a primary path over fields that are more likely to produce lift. As important as where to stay, there are also areas to avoid. Avoiding tree covered canyons or other areas known for sink or without possibility of an out landing is often part of the planning.

On Mountain Flights, the primary path is a fall back for a pilot to return to whenever lift or thermals are not found and the pilot begins to descent to a level near the terrain. Even when there is lift, the primary path should be kept within a conservative glide slope from wherever a pilot is in relation to the mountain. If a pilot thermals up 1000 feet above the launch, it is less imperative that they stay directly above the primary path. When lift disappears and they begin to descend back toward launch, they need to return to a point above the flight path.

Avoiding departure from the parameters of a flight plan is key to safety. Once outside of the flight plan, a pilot would lose his or her safety net and have to fly and make decisions without the confidence the plan provides.

Where possible, flight plans also include some bail out options. For example, if you are at a ridge soaring site, if the lift is light or for some reason, a pilot fails to stay up, a plan needs to be in place for landing at an alternate LZ (the beach at coastal sites, or any reachable field below the ridge). At some mountain sites, there are areas where a pilot can land if reaching the LZ becomes questionable. When a pilot is uncertain of their ability to reach the LZ, landing at a spot with some scrub brush would be better than continuing when trees are between that location and the LZ and any possibility of not making the LZ comes into play.

Mountain Site Samples

Below are some examples of primary paths including some of the flight path elements. As part of a flight plan, I normally inlude the landing approach options, but have not included in the below mountain examples for fear that they would be overly complex. Look these over and look for the common qualities (primary path goes over higher terrain, where not to go, where common thermal triggers are etc.)

A basic flight plan for a 300 foot hill might include more options. If lift is encountered, the pilot then has to keep downwind of the landing approach location until the lift has backed off and allowed them to enter the correct height to begin the final approach. The wide S turns might be plenty for a bit of extra lift encountered just after launch. Normally, a figure 8 pattern would not be necessary, but once in a while at even a little 300' hill, a large amount of lift can happen at the same time. The key is to understand the reasons for the plan and why variations are there.

300' Hill at Ed Levin
(No Lift vs Lift Variation)

Clicking on below photos will get larger size window

Light or No Lift flight pattern

When there is lift, the flight plan changes as follows.

Big Sur - Wild Cattle Launch

At Big Sur, there is a shallow sloped ridge below the Wild Cattle Launch. It is about a 5 to 1 glide to stay above this ridge. The primary flight path is to stay above this ridge because there is normally more lift above the top of it compared to the tree covered canyons to the right or left. Sometimes though, if speed to fly is not implemented well, a pilot may start to get low enough that they cannot safely stay above this ridge. If this happens, the plan dictate an alternate. The alternate is to veer to the right if you start to get close enough to the terrain or trees come within range of you glide slope. Veering to the left of the spine is out of the question. It puts a pilot too far downwind from a ridge that also veers left from the end of the center ridge. Going left would also put a pilot in a bigger canyon where penetration would not be as good.

At the end of the center ridge is a ridge that veers off to the right. On flights where you cannot stay above the center ridge, veer to the right and angle toward the ridge that Y's to the right. The flight plan says at this point to find an angle that your glide will clear this ridge as you angle out. Because the ridge descends as it veers to the north, you normally do not have to go very far to the right to clear it. Once past it, you can then head back to the south toward the LZ. Even when pilots have to take this alternate route, they usually end up at the LZ about 500 - 1000 ft AGL on a lighter wind day.

The keys to this plan are to stay above the center ridge if at all possible. If not possible to stay above the ridge, veer to the right until clear above the ridge that runs to the north. Once past that ridge, follow the ridge line south to the LZ.

The below images show you some of this flight plan from both launch and the LZ.

Click Pictures for larger images ...

Potato Hill

Below are some photos of Potato Hill. The Yellow and Blue paths are the two most common flight paths used at this site. Most of the time, I prefer to use the yellow path, but either can work. Both primary paths target higher terrain where lift will be better and increase the chances of reaching the LZ with extra altitude. The spine of the left is very easy to see from launch and any thermals that rise up the slope below the top of the ridge will release above the spine.

On flights where lift and thermals are encountered, a pilot can climb and have a little freedom from continuing towards the LZ. But, whenever a pilot starts to lose lift and begins descending again, the flight plan dictates to stay on the flight path. Once well up in a thermal, moving around a bit above the general area is fine. Once a pilot moves back down toward launch level, moving back to the primary path comes back into play..

Potato Hill - Two Common Primary Paths

I normally find better lift on the yellow path, but either can work good for flight. Many think the Hay Bails is the best thermal, but the most consistent thermal at Potato is the one on the ridge to the left of launch. Also, this path usually provided easier ability to reach the LZ with some extra height.

Click on pictures for larger images ...

View from launch

So, as you can see, flight plans help to manage the hazards at all sites. They give pilots a plan that will help them get into the LZ with abundant altitude and a plan for their landing approach. For students, they give them a fall back if they get overwhelmed by the flight or anything.

Avoid moving outside of the envelope of flight plans. It will help you simplify your flights and help you become a safer pilot.