Wake Up Call
by Jan Meyer
Most jumpers use visual cues for altitude determination. This was or at least should have been, the way you were trained. You may use your own visually accessible altimeter or one mounted on another jumper. After enough jumping experience, you can use the horizon as a rough altitude estimate. Visibility and terrain colors can mislead your estimate of altitude by a thousand or so feet.
A lot of times you would like to keep your sights on the relative work. You don't want to miss a key. You have to watch for traffic, so you won't collide with anyone. In essence, your eyes have to pay attention to a lot more than just the altitude. It should make sense then to use an audible altimeter, as a backup to your visual cues. Some jumpers even use an audible altimeter as a primary altitude indicator.
A prevailing custom is to set a "dirt alert" near breakoff altitude. If set slightly below breakoff altitude the "beeping" will tell you that you've lost track of time, but it's not too late to get with it. That is, if you pay attention to the sound and take prompt and appropriate actions. Turn and track when you hear the beeping, not a few seconds after it stops.
A different view, proposed by Tom Barnett, about audible altimeters suggests setting them for 1500 feet. Two of every three skydiving fatalities are caused by jumpers failing to initiate emergency procedures at a sufficiently high altitude. The numbers in Table 1 show that 98 of 148 skydiving fatalities from 1982 to 1986 were due to malfunctions or no pull low pulls.
Table 1: Skydiving Fatalities related to
Malfunctions or No/Low Pulls
The incident reports usually read as these examples:
"The deceased tried to clear a malfunction and then cutaway at too low of an altitude."
"Relative work brokeoff low, the deceased experienced a high speed malfunction, cutaway, but did not have sufficient altitude for reserve deployment."
"The deceased lost track of altitude."
"The deceased became distracted by a minor equipment problem."
Could a "wakeup" call at 1500 feet have saved these people? Maybe.
Under normal circumstances you should be slowly descending under a good parachute at 1500 feet. A beeping in your ear then may only be a minor nuisance or it may prompt you to decide where you'll land (an especially good cue for students and new jumpers). However, in an emergency situation, when your senses may become distorted, time appears to slow and you start shaking risers or trying to pull handles, a ringing in your ears may alert you to impending danger. At 1500 feet the beeping should tell you:
"Wake up! Get that reserve out NOW! Cutaway if required. Dump that reserve, stable or not."
Your vision is used as your primary sense for altitude. Hearing is your backup sense. If and when your visual attention to altitude becomes distracted you may rely on your hearing.
When do you want your "WakeUp Call"?
---at 3000 feet on every dive
---at 1500 feet under a normal canopy and an occasional high speed malfunction.
To help you decide, consider which situation is more life threatening if you don't get a "WakeUp Call" and oversleep.
Originally published in Sport Parachutist's Safety Journal V2,
#2 Nov/Dec. 1989.
Dedicated to enhancing sport parachuting safety by disseminating information about equipment, environments and human factors.