On Friday, January 29, 2016 at 2:31:47 PM UTC-5, Jonathan St. Cloud wrote:
I would like to see the experiment method described in detail.
Below are some snipped relevant paragraphs from the most recent conspicuity study I could find online. I recall reading several others, including one that was referenced in this thread recently, but the conclusions were the same, IIRC.
Speaking as a former engineer, the methodology designed and employed by Dr. Head and his associates for the important "head-on-converging" scenario seems reasonable. It's likely a worst case "no relative movement" converging tracks situation. I agree that red/orange tips and tail are pretty visible on the grid, across a thermal, looking up at the sky, or even looking down against a contrasting background. But the scenarios most of us worry about are those where two aircraft are converging at similar altitudes with little relative motion for the eye to pick up. There are variations of this, of course, involving another aircraft approaching from the side (as when several gliders converge on an already established thermal from different directions at the same level--one where I've almost been clobbered a few times) or a power plane overtaking from directly behind (another personal near miss). But the one that seems to get the most attention is head on under a cloud street (a la the Uvalde incident some years ago).
The full Bicester report includes details on other trials involving simulated thermaling, mirror film, and black underside paint. I'm sure there are other ways to run these tests but this team seems to have made a competent, good-faith effort to experimentally determine the effectiveness of different types of markings/colors on glider visibility.
Unlike at least one other test I've heard about, this group stopped short of saying that the Day-Glo markings made a glider less likely to be visible. So I guess there's no harm pimping your ride if it makes you feel better. But keep those eyes open.
From "See and avoid?"
Dr Tony Head, from the College
of Aeronautics at Cranfield
University, reports on the
outcome of recent conspicuity
research conducted at Bicester
(from "Sailplane & Gliding", Aug-Sep 2003)
http://uvs-international.org/phocado...sep%202003.pdf
Trial Four: Air Cadets' DayGloİ pattern
during constant-bearing converging paths
The randomisation and the direction of
runs was as for Trial One and Figure 1 (p29).
Weather was excellent with scattered cloud
and visibility in excess of 25km.
[excerpt follows from p29 describing Trial 1 methodology]
Crews flew toward a central point at
2,000ft AGL and 70kts ground speed (as
indicated by GPS). Each pair of crew was
given a set of headings to fly for both outward
and inward tracks. When crews sighted the
other MG, they called "Mark" on the radio
and noted their distance from the central
point as indicated by GPS. Once both MG
had been sighted, crews reversed track and
began the next run. An example of the
randomisation and the direction of runs is
shown in Figure 1, below.
The distance between the aircraft was
calculated by simple trigonometry, the
distances of both MG from the central point
being noted and recorded at the time of
visual contact.
[end of excerpt]
Results: There were no significant
differences in detection distances between
the clean (2.67nm) or DayGloİ MG
(2.82nm). The mean detection distance for
all of the runs was 2.75nm, with ranges
from 0.88 to 5.3nm.
The weather for these trials was ideal,
with sunlight and scattered cloud.
The overall mean detection distance of
2.7Snm was considerably better than in trial
1 (1.69nm) reported here, when the weather
was less than ideal.
In the previous trials carried out in 2000,
where similar DayGloİ patches were
applied to the MG, the overall mean detection
distance was a comparable 2.54nm.
As the crews were different for the 2000
and 2002 trials, there can be no meaningful
statistical comparison. However, the mean
detection distance, in good conditions, with
hyper-vigilant crews, for all MG with or
without DayGloİ, is only 2.64nm. The
crews, who were initially very enthusiastic
about the larger DayGloİ patches,
confirmed that they did not appear to aid
conspicuity.
The two studies, in 2000 and 2002,
that examined conspicuity of MG during
constant-bearing convergence, failed to
demonstrate a significant increase in
detection distance with the use of the
DayGloİ patches. There appeared to be no
measurable negative effect upon conspicuity
either. Any detection was consistently reported
to be due to the silhauette of the MG or
to a glint, and not to the DayGloİ.