You must begin with an object that looks jumpable and height will be the first test. But height is not the most important factor. If there is nowhere to land, there is no point in considering any other factors. Look beneath the exit point for potential landing areas and ask yourself the following questions.

can you land your parachute in the area you have chosen 100% of the time?

if you have to perform a PLF, or you stall it in, or your canopy has a faster descent rate would you be happy doing it on the surface available? Are you
prepared to cutaway and lose your canopy if you land in fast flowing water or a tree?

as the slope increases you have to decrease your forward speed. This means that you may be near your stall point descending rapidly on a steep slope. If you shut down the canopy you will hit hard and roll back down the slope. A flatter landing area will allow you to come in with more speed, which gives better flare. Can you accurately time your flare depending on the slope?

if you miss your chosen area is there somewhere else that you can land or are you 100% accuracy confident?

are the obstacles in the landing area easily avoidable?

do guy wires, trees, buildings, or pylons interfere with your final approach to the landing area? Will they alter your angle of descent (and hence speed) or the direction you have to land (downwind or towards a less forgiving landing area)?

can you get back home from the landing area (especially relevant on cliff jumps in remote wilderness locations)?

discussed in another section. There is specialist equipment available that will satisfy most criteria. Is your canopy large enough (low wing loading) to allow a stalled approach
and does it have the appropriate glide ratio to get you there?

taking into account freefall delay, deployment height, malfunctions (they eat up altitude), and the glide ratio of your canopy, are you capable of reaching the landing area?

air density decreases with altitude, which leads to faster descent rates and harder landings. Is your wing loading (canopy size) appropriate for the faster descent rate?

skill and experience lead to confidence. But if you are confronted with a difficult situation such as a tight landing area, will you cope or be overawed (i.e panic)?

- likely to be surrounded by streets of varying widths. Streets have a large array of obstacles including power lines, trees, overhanging street lights, moving vehicles, pedestrians, monuments, other buildings, etc. If you are lucky there may be a park nearby.

- there will generally be a field (any size is possible) surrounding the antenna. If the antenna is located on a hill it is very likely that the surrounding area will be sloped. Most
antennas have 3 guy wires emanating from the structure. They will restrict your flight path.

- many variations exist. The most common will be a riverbank surrounded by trees. Other possibilities include: fast flowing water, roads, fields, parks, nasty rocks and trees and
steep slopes. During construction temporary roads are often built and land is cleared to accommodate machinery.

- cliffs share characteristics with spans. Generally speaking though, cliffs exist in wilderness areas and will have a sloping talus below them (with trees). This talus will probably
end in a waterway, field, road, or forest.

Height will determine what type of jump you can do from an object and what equipment you can/should use. Options increase with altitude.

Most man made objects and popular landmarks already have some indication of height recorded somewhere. Otherwise, drop testing is the most common method for determining cliff height. If you are performing a drop test make sure there is nobody below. You should wear either your primed rig or a lanyard when standing on the edge in case you fall off.


Subtract the greater of one second or 10 to 15% from your measured time to allow for errors in measurement. The following table is an approximate indication of height fallen and freefall time. Please review freefall table.

floor heights vary between buildings. Commercial buildings tend to be higher than residential buildings. All buildings range between 8 and 13 feet. To confirm, measure the
height of one floor yourself and multiply by total number of floors, or contact either the building engineers or a real estate agent. If they ask why, say you are a real estate investor

: each colored section of antennae indicates a particular height depending on its color. This varies between countries. Once again, contact the owners. If they ask, tell them you're a curious pilot.

: usually there will be signage. If not use a drop test.

: topographic maps and drop tests are the easiest way to determine cliff height.


As a general rule,

• the further the landing area is away from the object
  
• the longer the intended canopy flight duration (i.e to fly around obstacles)
  
• the more difficult the landing area (need more time and altitude to set up)
  
• the harder the landing area (solid as apposed to water)
  
• the slower the opening (slider, older gear, larger canopy, high closing loop tension)
  
• sail slider = slow opening, mesh is faster, no slider is fastest
  
• the smaller the pilot chute
  
• the larger the slider size
  
• the longer the intended free-fall
  
• the harder the intended (planned) maneuvers
  
• the more under-hung the object
  

..... THE MORE HEIGHT YOU NEED


Each BASE site is different, you need to estimate the canopy opening altitude (AGL) that will give you enough time to safely reach the landing area under existing conditions. Subtract that distance from the exit altitude and you will know the distance that you can spend free-falling AND deploying your canopy. Allowing for safety margins, assume that a full slider up deployment will take 3 seconds and slider off/down 2 seconds.


UNDER-HUNG OBJECTS: If you are intending to jump from an object that is under-hung or has protruding obstacles, then you need to follow a positive launch with a good track. Tracking takes affect after approximately six seconds, therefore if a rock drop test strikes an obstacle in < 6 secs = you have an unavoidable free-fall obstruction - don't jump.

You need a stable place to launch from and you have to be able to get to the exit point

---

BLiNC Magazine strongly encourages readers to comment on its content. Read the Disclaimer and the policy on Site Naming. Posting a comment releases it in the Public Domain. These comments will be moderated. If you see inappropriate content, please notify the administrator
All rights reserved. No republication of this material, in any form or medium, is permitted without express permission of the author. All images and words are protected by U.S. and International Copyright laws. Copyright 1994-2011