Who's Going to Spot?
How often have you been in the situation where someone has asked, "Who's going
to spot?", and at that point you made sure eye contact was avoided with the
person asking the question? Sound familiar? Knowing how to determine the exit
point of an aircraft is the responsibility of every skydiver. If you are not
comfortable with the thought of looking out and determining where to exit, I
suggest you try it and make yourself learn the art of spotting. Spotting is a
skill that must be developed. Reading about spotting takes care of the theory,
but does not replace the practical application.
The following are guidelines to take into consideration when determining where
and when to exit any aircraft. Taking the time to follow these steps will lend
itself to building self-confidence about your spotting abilities, as you and
others on the plane trust your judgment.
There are several very important factors that need careful consideration when
determining where to exit an aircraft.
1. Preparation Time (Prep Time): Very important and too often the maker of a
bad spot. All too often the point of exit for your group, and the groups that
follow, take longer than anticipated. Guess what? You are walking. When you
think the exit point is too short, and feel you should wait that extra ten to
fifteen seconds, begin your climb out. The time taken here is exactly what
Prep Time is. Waiting the additional time lends itself to a long spot.
Climb out usually takes longer than you think. You may be surprised when you
realize how far the aircraft travels across the ground in ten seconds. The
next time you are in a DC-3 look out the door and make sure you are looking
straight down. Find a heading on the ground and count to ten seconds. See
how far the aircraft has traveled. Use this mental picture when calculating
Prep Time. A DC-3 will cover a considerable distance across the ground in
ten seconds traveling at a speed of 80KTS or 92MPH.
Compare the distance traveled when you repeat the same exercise the next time
you are in a Twin Otter, Cessna or local DZ aircraft. Use the mental picture
of the distance traveled across the ground when determining the point of exit.
Using this technique on high upper wind days could prevent a potentially
dangerous situation when jumpers from two groups cross into each others
airspace during a track.
A skilled spotter will take Prep Time into consideration for all groups on the
pass. Load the aircraft in such a way as to allow easy exit for each of the
groups on a pass. Determine the experience level of each group on the aircraft
so you can take into consideration the time necessary for climb out and exit.
Lower experienced groups will take longer to climb out. Each group on a pass
should, without exception, allow a minimum of 10 seconds before exiting the
aircraft to allow for adequate separation between groups. Always put the highest
opening jumper out last.
Remember:
a) When arriving at the DZ watch other groups exit to give yourself a mental picture
as to where the exit point should be.
b) Find out who the spotter was on a load that recently landed and ask them
what the upper winds are doing, and where the spot is.
c) Communicate with the pilot. Don't expect the pilot to know how you want
jump run flown.
2. Upper Winds (Free-Fall Drift): While climbing to altitude ask the pilot
how fast the upper winds are blowing at altitude, and from which direction the
upper winds are coming. The information is easily obtained from Flight
Services. *(See Footnote) Depending on the pilot, you could get a couple of
different responses. For example you may be told, "The winds are 25 out of
36," or in a less cryptic tone, "The winds are blowing at 25KTS from the north."
The former is a compass heading. 0 degrees or 360 or 36 all indicate the winds
are from the north, and 18 or 180 indicate the winds are from the south.
Knowing what the winds aloft are is critical. The technique in knowing how far
to take the aircraft upwind to allow for Free-Fall Drift takes time and
repetition. If in doubt ask a more experienced skydiver, who you know can be
trusted, to look over your shoulder. When you arrive at the DZ watch another
group exiting to see how much 'Free-Fall Drift' or push they get. Upper winds
blowing at >50KTS can cause drift of up to a mile or more if exit altitude is
13,000'.
Look at the following example:
The rate of speed at which an aircraft travels across the ground is known as
the Ground-speed. The speed at which an aircraft travels relative to the air
is called the Air-speed. Ground-speed and Air-speed are two factors not to be
confused. The discussion here focuses on the speed the aircraft travels across
the ground as rated in knots. The distance across the ground for one knot is
approx. 6080'.
Suppose an aircraft is traveling at 75KTS. With no upper winds, the aircraft’s
ground speed is 75KTS, or 126.7 feet/per/second across the ground. The aircraft
is carrying three groups. Group 1A is a 10-Way, Group 1B is a 6-Way and Group
1C is a 4-Way. The upper winds are minimal; under 10KTS. If Group 1B takes
a 6 second delay before exit the horizontal distance between Groups 1A and 1B
will be approximately 760'. Sounds like a lot, doesn't it?
Now assume the upper winds are blowing at 30KTS. The aircraft is flying
directly into the upper winds. The ground-speed of the aircraft is reduced to
45KTS, or 76 feet/per/second. Horizontal separation between groups is reduced
from 126.7 feet/per/second to 76 feet/per/second. Group 1B only allows 5
seconds for separation time after Group 1A has exited the aircraft. Using the
factor of 76 feet/per/second, the horizontal distance between Groups 1A and
Group 1B is approximately 380'. Horizontal separation of 380' is dangerous,
especially when you take into consideration the distance covered across the
ground during a track.
For this example, lets assume Group 1A's break-off altitude is 3,500'. A
skydiver in a max-track position can achieve horizontal speeds up to 60MPH, or
52KTS. If a skydiver were to start tracking between 3,800'-3,500' and hold the
track until 2,500' (approximately 6 seconds), then flair, waveoff and pull, the
skydiver could achieve an average of almost 88 feet/per/second, or
approximately 528'. The result would be the potentially dangerous situation
whereby one or more skydivers from different groups on the same pass could
possibly cross each others airspace.
Taking this example a step further, assume the upper winds are now 65KTS. The
air-speed of the aircraft remains constant at 75KTS, however, the ground-speed
(distance the aircraft travels across the ground) has been reduced to 10KTS, or
16.9 feet/per/second. Based on this example, taking up to 45 seconds before
Group 1B exits is not excessive in an effort to gain adequate separation and
avoid a potentially dangerous situation. Canopy collisions can and do kill
skydivers.
3. Body Position: Face forward and look towards the front of the aircraft.
If you are new at spotting do not sit sideways to the door; sit facing forward.
Pitch your head sideways and look straight down. Now look up toward the wing
tips followed by scanning the horizon. Doing this will help you determine
whether or not you are looking straight down and if the aircraft is flying
level. Continue to do this motion of looking down, wing tips, scanning horizon
and looking down. Compare the horizontal axis of the wing to the horizontal axis
of the horizon. Are they horizontally relative to each other? Are they at an equal
plane? A couple of degrees off can be a mile or more, especially when the upper
winds are blowing. Know if you are looking straight down.
4. Forward Throw: Depending upon aircraft type, Forward Throw carries a group
a considerable distance. Take Forward Throw distance into consideration when
exiting aircraft such as a DC-3, C-130 or higher airspeed type of aircraft.
Although the transition sweep from horizontal throw to vertical decent is a
short distance in time, the distance across the ground can add up.
5. Ground Winds: There are times when ground winds exceed the upper winds.
Factor into consideration the ground winds in addition to the upper winds for
determining the spot. Maybe you will have to take some additional Prep Time
allowing the groups to remain up wind of the target. For student and novice
jumpers recently off of student status, and depending upon the exit altitude, throwing
a Wind Drift Indicator (WDI) may be necessary to help determine the push of the
ground winds. Spot for the ground winds when they exceed the uppers.
6. Type of Reserve: Never overlook the skydiver having a round reserve. If
you are spotting make sure you take into consideration the person with the
round reserve.
Learning to spot takes time and repetition. The next time someone asks,
"Who is going to spot?" say, "I will."
(Footnote) *In many geographic areas Flight Services can be contacted directly
for upper wind conditions. Contacting Flight Services directly is not
inappropriate for determining upper winds prior to the first load of the day. Blue Skies
Eric Bernstein
D-9298
ericber@oz.net
