From The Mag

Digital Altimeters for Students

Digital Altimeters for Students by Nils Predstrup | April 2013 Blue Skies Magazine | Photo by Delphine Huet
Digital Altimeters for Students by Nils Predstrup | April 2013 Blue Skies Magazine | Photo by Delphine Huet
Written by guest author

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Originally printed abridged in issue #42 (April 2013) of Blue Skies Magazine.
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By Nils Kløcker Predstrup

Until now students have generally been using analog altimeters in the first jump course. In the meantime, digital altimeters have gotten more and more popular among experienced skydivers.

During the 2012 season at Skydive Voss in Norway, we introduced digital altimeters to our AFF students. The experiment was initiated on request from the head instructor (HI) Espen Høst, and executed with approval from the Norwegian air-sports federation’s (NLF) experimental department. Although the operation is run according to Norwegian regulations and the majority of the instructors are NLF members, the instructors working at the AFF school also include members of other organizations such as the U.S. Parachute Association (USPA) and Australian Parachute Federation (APF). The instruments we have been testing are the visual digital-display VISO and the audible OPTIMA manufactured by Larsen & Brusgaard.

The question is: Why should students only use analog visual altimeters when other, more advanced, and more accurate instruments are the standard for experienced skydivers? The arguments against are often grounded in assumptions rather than actual experience and so this experiment was initiated to cast light on the pros and cons of using digital instruments for students.

The study included all 126 of our new AFF students at Skydive Voss. During the ground school, students were introduced to the VISO (digital visual altimeter) and to the OPTIMA (audible altimeter). The students were made aware of the fact that they were participating in an experiment. At the same time, ALTITRACKs (an analog-display visual altimeter manufactured by Larsen & Brusgaard) were introduced to see if the analog face was intuitively preferred by some of the students. The students were given the option of choosing an analog-display visual altimeter if they so desired. Three of the 126 students used the ALTITRACK/OPTIMA combination: one had previous experience in paragliding, one was an old-time skydiver refreshing after many years not jumping, and the last was a glider pilot—so they chose what they were used to. Although a few more students ended up using a combination of ALTITRACK and OPTIMA, none of our first-time students chose the analog display before the digital.

The students were briefed to use the VISO as their means of altitude awareness in freefall and above 900’under canopy. Below 900’ the audible OPTIMA would become the primary altimeter and the VISO should then be used only if the student felt the need to visually check or confirm the altitude. This was taught in order to promote full visual focus on the actual surroundings and other traffic.

Under canopy the OPTIMA would be set to beep first at 900’ indicating the altitude where the student should start the landing pattern, leave the holding area, and come on to the downwind leg. The second beep from the OPTIMA would be set to 600’ to indicate the altitude where they should turn 90 degrees and come on to the base leg. Between 600-300’ the OPTIMA would be set to sound a sequence of 10 beeps guiding the student toward and onto final approach. The last beep at 300’ would indicate that the student should initiate no more turns, and should prepare for landing.

The freefall alarm on the OPTIMA was set to beep at 2,800’ so the students would not hear it before they were trained to open at 5,500’. So the student would still need to remember to stay actively altitude aware in freefall.

During ground training the students used the replay mode on the VISO to practice freefall maneuvers for the first jump in real time and at the same time to familiarize themselves with the instrument. The OPTIMA was introduced and explained during the canopy landing pattern module. We briefed the students to use the audible as their primary altimeter on the landing pattern under 900’ to allow full visual focus on the actual surrounding terrain and landing area as well as possible canopy traffic and other obstacles. Emphasis was made on “No turns! Only small corrections to avoid obstacles.” after the last beep at 300’.

Digital Altimeters for Students by Nils Predstrup | April 2013 Blue Skies Magazine | Photo by Delphine Huet

Digital Altimeters for Students by Nils Predstrup | April 2013 Blue Skies Magazine | Photo by Delphine Huet

After passing AFF level 7 the students answered five questions regarding their experiences with the instruments. The questions were:

1. Did you at any point have problems reading the altitude on the VISO in freefall or under canopy?

Three students noted that they had to look an extra time at the instrument in freefall to be sure of the altitude. None of the cases required interference from the instructor.

2. Do you have any positive or negative experiences using the VISO?

All of the students answered positively on this question, including the ones who answered less than positively on the first question.

3. Did you hear the OPTIMA beep under canopy on all your jumps?

All students except one answered yes to this question. The one student who did not hear the beeps on one particular jump noted that she was very stressed out at that particular time and therefore did not hear the beeps.

4: Was the OPTIMA helpful to you on your landing pattern at 900’, 600’, and 300’?

One student answered no. He explained that he had previous jump experience and had the habit of looking at a visual altimeter. An additional note was given by this student stating that it was very nice to have accurate, easy to read altitude at all times.

One other student answered both yes and no. He explained that when he initially had set up wrong on his 900’ point and had to adjust during the rest of the landing pattern, he found the beeps confusing in that particular situation. All other answers to this question indicated the students found the OPTIMA to be helpful.

5. Did you look at the VISO during your landing pattern under 900’ or was it enough to listen to the beeps and only use the OPTIMA?

Sixty-nine percent answered that they used the VISO in addition to the OPTIMA on every jump; 14 percent answered that they only used the OPTIMA under 900’; 17 percent answered that they used the VISO in addition to the OPTIMA on some of the jumps only.

PD New Beginning

The students’ answers to question 5 indicate that, especially in windy conditions and if for some other reason the navigation into landing got more challenging, the students liked to use the VISO as well. Also, a tendency for many of the students to rely only on the OPTIMA under 900’ seems to be present as they gain trust in the beeping sequence after a few jumps.

It is interesting to report that some of the AFF-certified graduates experimented themselves with using the analog altimeter instead of the VISO during their solo consolidation jumps. This was mostly due to that fact they were sharing equipment with other students and sometimes availability of VISO instruments was limited. They mentioned that they did not have any trouble with them in freefall or under canopy but some were dissatisfied with the precision and preferred digital over analog displays.

Instructor Observations in Freefall

Initially we were using wrist mounts for the VISO but we changed to the glove mount because it allows flexibility in the wrist for better angling without having to bend the elbow. In Norway it is mandatory for students to wear gloves so it made sense to use this option and it worked really well for us. One student did start the pull sequence at 6,500’ after reading the “6” as a “5.” This happened when we still were using the wrist mount and the mistake was due to looking at the instrument at a very shallow angle. This incident was one of the main reasons we changed from the wrist mount to the glove mount.

There were a few students initiating the pull sequence a bit high, at 5,900’ instead of waiting for 5,500’ on the first jump. But after informing subsequent students about this possible mistake during the initial instrument briefing, the tendency was eliminated. (Note: Because of elevated terrain around the DZ we have students lock on at 6,000’ and pull at 5,500’.)

Other than those few isolated cases we did not experience any problems with the usage of the digital display; the students were generally very altitude aware throughout the test period.

In those cases when the student lost altitude awareness because they simply forgot to actually check the instrument, reminding the student to check their instrument resulted in the student promptly regaining altitude awareness.

In the test period we experienced some very extreme conditions: -30C (-22F) in altitude and a humidity level that caused full-face helmets to fog up extensively, but still in those conditions the VISO worked as normal.

Instructor Observations under Canopy

Since we started using the VISO and the OPTIMA instead of analog altimeters we have seen a tremendous improvement in our students’ canopy control skills. In Voss we don’t use radios for our students, so to see the students fly an easily recognizable and “by the book” landing pattern, all by themselves right from the beginning, has been a delightful experience and a big improvement. This is the most significant difference we as instructors witnessed when using the new instruments, and in my opinion in itself is reason enough to give the students these instruments.

It is comforting as an instructor to know that when you ask the student to fly the standard landing pattern, you can also give them the tools to actually execute the task and decide when they are at a given altitude under 900,’ which can be very difficult with only an analog altimeter. Also the fact that we have not seen a single student doing a low turn since we introduced the new instruments is a valuable result.

We believe the learning curve is faster with digital versus analog displays. Students can say with precision what altitude they were at a specific moment of their landing pattern—and therefore accept instruction because of the obvious evidence (versus showing approximately where they think the needle on their analog altimeter was). They have a more accurate perception of the actual experience and therefore more accurate debrief.

Precautions and Procedures

The digital instruments function only with battery power and this needs to be taken into consideration to make sure battery power is sufficient at all times. However the VISO and OPTIMA batteries are marketed as being able to last for approximately 1,000 jumps on one battery set. At Skydive Voss we have a procedure of changing every battery in every unit at the beginning of every jumping year.

The VISO will shut itself off after 14 hours (as the CYPRES AAD does) so we build in a procedure of activating the instruments every morning before jumping. Also it is possible to change between feet or meter display, and altitude or speed in the display so the instructors (and students) need to be familiar with the features and ensure it is in the desired mode.

The OPTIMA will sound a sequence of beeps on climb in the plane at 1,000’ to let the user know that it is on and will sound according to settings on the way down, so we have a procedure of detaching the seatbelt and making eye contact with the student who confirms that the unit has beeped.

The manufacturer informs us that if someone is using polarized glasses it may interfere with the clear viewing of the display on the VISO. However we have not experienced this.

If the DZ is located near mountains the students need to be made aware of the fact that the instruments function on air pressure and will not show accurate altitude over the ground if flying over elevated terrain (same for analog).

Conclusion: Digital altimeters can be used for students with great success. We see no particular reason to use only analog altimeters for students.

About the author: Nils Kløcker Predstrup is from Copenhagen, Denmark, now living in Voss, Norway. He started skydiving in 1997, has more than 10,000 jumps, and is a 5-time world freestyle gold medalist (2001-2005).

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  • How about the argument that dials are easier to evaluate with a quick glance in high stress situations?

    • My opinion only here, but it takes me probably five times longer to process an analog clock/alti display in a calm environment. I personally would rather have a digital display in high stress, no question. If someone is used to an analog display and can read that quicker, by all means he/she should use analog. What do you think?

    • Thank You Craig for pointing this out!

      Not so much the interpertation of a dial, but with the yellow /red zone fast approaching, less work required to interpert what information the device is “telling” you! Your mind dosen’t have to work as hard getting information, and when your mind starts to shut down this could be critical because the information requirew less cognative effort to interpert!

  • My concern regarding this research is the not every participant had an equal opportunity to use every style of altimiter. Your indicating research, but with out the equal chance rule being followed the observations are of very little use. Basically if you take groups of newbies, and give each group one type of altimiter, they have no common ground or reference to make decisions. Each group is going to be “happy” with what they are given, because they don’t have the experience to discriminate. Aditionally in time of stress cognitive functions decrease, it has been long known in aviation and other circles that display readability is a diffucult subject to understand. Critical displays are still “displayed” in analog, (picture) form due to the decrease in cognative performance in high stress conditions. This does not bode well for digital displays, however with the manufacturers advertising dollars driving so many decisions, I’m sure they will have some sort of curt comebak and marketing mumbo jumbo…

    • How do you see manufacturer advertising dollars driving decisions, especially in this case? I used to manage the Alti-2 marketing budget way back in the day when Neptunes first came out. I have no idea what their or L&B’s budgets are like today, but I’m 99% positive the money is much, much smaller than what you’re assuming.

    • For sure It’s still early days but the only thing we have found is that some students have locked on a little early. They are told to lock on at 6 thousand as we always have but as some see 6.90 then they lock on and pull a little high. Also as Nils explained in the article a few times they have read 6.5 as 5.5. For sure the concern of being able to read the device was a big concern for us but we just haven’t experienced a negative out come. But of course we continue to proceed cautiously but the way we train our students has nothing to do with manufacturers policy or marketing.

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