Newsletter Volume 30, Number 11

Calendar

Great Tentative Lineup of Programs

November	FSS Speaker, then plan on a November 14th Fly-In to Oakland FSS.
December	Holiday Party @ Mr. Steer's!
January	Doug Groom's Adriatic Adventure
February	Christoph Bohmann's Aviation in Europe

Happy November Birthdays to:

Pravin Tulachan on the 6^th
Mark Hernandez on the 8^th
Doug Groom on the 9^th
Lindell Wilson on the 13^th
Christoph Bohmann on the 18^th
John Gould on the 26^th
Jerry Morgan on the 28^th
Edmond Yuen in September. Omitted, with our apologies.

Next Month's Article

Sailing Cercei: The Adriatic Adventure. By Doug Groom

Perception and Flying: Installment 3

This is the final installment of my series on perception and flying. If the reader recalls from the first installment, the incident, which precipitated this series, occurred on February 6, 1999. In that episode I promised to relate how perception and the environment may have effected that incident. That will be done at the end of this article.

Night flying clearly results in the diminution of the pilot's ability to perceive his environment. According to the AOPA Safety foundation, the most likely month for an accident to occur is December. The reason given is not the weather, as one might expect, but rather the fact that the shortest days occur in December. It is easy to fly into unseen clouds and much harder to navigate over unlighted terrain at night. These things are obvious to most pilots. There are other more subtle effects.

Even before the sun goes down, the change of light as night approaches can cause problems for the unprepared pilot. It is common for pilots to experience both the sun glare and reduced visibility from haze. While flying into the sun, haze often seems to appear out of nowhere. As the sun lowers, it illuminates particles in the air and can quickly turn that beautiful VFR day into a near IFR experience. To add to the uncertainty, the sun shining directly at the pilot can make the instruments very difficult to read exactly when you need them the most. This is due to the contrast in lighting between the bright sun outside and the shadow inside. That great looking set of pilot glasses can add to the problem. Another dilemma, which frequently occurs at sunset, is called flicker vertigo. The light glowing through haze and viewed through the spinning propeller can cause a strobe effect. This consequence can cause a pilot to experience serious disorientation.

As one flies toward the west at sunset they should always be prepared for these problems. The use of instruments by the VFR pilot may be necessary if haze obscures the horizon. Remember you may be invisible to other aircraft in the area under these conditions. Don't be afraid of letting the tower or controlling authority know your problem and ask for help avoiding other aircraft or finding the airport. Upon encountering flicker vertigo look away from the propeller and try changing the RPM of your aircraft.

Most pilots understand the physiology of the eye and the relationship of rods and cones to night vision; therefore that will not be discussed here except to say that rods are used primarily for night vision and cones for day vision. As night ensues, adjustment to the darkness can take much longer than most believe. Studies have shown that the residual effect of bright daylight can last for hours before full night vision is achieved, and one bright light can decrease the effectiveness of night vision for over one half an hour. Unfortunately for pilots flying at night, the rods in the eyes are far more sensitive to oxygen deprivation than cones. This means that although oxygen may not be legally required below 12,500 feet, night vision can be effected significantly at much lower altitudes. Recent information indicates that night vision can also be effected by dehydration. The dry cold air at high altitude evaporates moisture from human lungs at an extremely rapid rate and that moister must be replaced to prevent a reduction in night vision.

At night there are many optical illusions which may effect the unwary pilot. The lights from a road can create a false horizon causing the pilot unknowingly to enter a bank. A strong distant light off the wing tip can subconsciously cause a pilot to keep that light in the same position. This would result in him deviating from his course towards the light. Fixed lights can appear to move. A combination of good navigation and instrument skills as well as attentiveness while at the controls, should keep these problems to a minimum.

According to studies done by the AOPA, landings are the most likely phase of flight for an accident to occur in general aviation. Most of the reasons for this fact are obvious with a little refection. Pilots are going to be tired at the end of a flight. Long flights are more likely to end at night. Fuel exhaustion may be more likely to occur toward the end of a flight.

Most pilots are aware that landing at unfamiliar airports can cause problems. An upslope runway can make an aviator believe he is high, when in fact he is to low. A narrow runway can have the same effect. At night these problems are compounded. The surrounding terrain, which gives us help with our perspective, is often not visible. Landing lights can help, but many general aviation aircraft do not have landing lights and it is hard to judge ones flare when the runway looks like a black hole drawing all celestial objects into it.

Our mishap occurred about 7:00 PM or 7:30 PM on the night of February 6, 1999. It was a very dark night with no moonlight. It was the end of a long flight. The tower at Ryan Field, on the outskirts Tucson Arizona, gave us a progressive taxi to the fuel dock. There were no yellow lines leading from the taxi way to the fuel dock. From the taxi way, the only lights visible were the restaurant lights on the other side of the fuel area and one set of yellow overhead lights above the Fuel Island. The area around island and the space between the taxi way and the island was a sea of blackness with only a small area of light directly under and in front of the dock. Depth perception was almost impossible due to the poor lighting. It was profoundly dark.

As we approached the Fuel Island, a yellow line became visible in front of the fuel dock. It appeared to be two taxi lines converging into one, then paralleling the fuel dock. Yellow lines are used to taxi on and usually assure clearance from fixed objects. As I taxied up to the fuel dock, I began to notice that the yellow line appeared too close to the fuel dock to assure clearance. I gave the aircraft a hard right turn away form the island to avoid the fuel pumps. I was sure the aircraft would clear them. I was in the right seat, furthest from the fuel dock. The left wing tip struck a pole in front of the fuel dock, shattering the wing tip. The pole was very poorly marked and had been very difficult to see under the poor lighting from my position.

The next day I revisited the area and could see the problem. It was obvious from the many paint markings; the pole in question has been struck several times before. It was easy for me to pick out the visual traps I had fallen victim to the night before. They were as follows:

1. Poor lighting.
2. Non-standard markings on the pavement.
3. Poor markings on objects near and on the fuel island.

The poor lighting around the Fuel Island inhibits depth perception. During the day it is easy to see ones distance from the fuel pumps when approaching them. The problem occurs on a dark night. There are no markings on the large new blacktop area around the pump. There are no lighted objects near the pump and absolutely no lighting between the taxi way and the small-lighted area in front of the fuel pumps. This results in a total lack of objects to aid in judging relative distance. The fact that human eyes rely on rods to see in the dark, rather than the cones compounds this problem. Rods are not as good at judging depth as are cones.

The most serious safety hazard at the fuel area at Ryan field is the non-standard marking on the pavement. AIM, PARAGRAPH 2-3-4 (a) through (g). The markings not only do not comply with AIM and they are misleading. Per AIM (b) the taxi way centerline is a single continuous yellow line, 6 inches to 12 inches in width. This provides a visual clue to permit taxiing along a designated path. Ideally the aircraft should be centered over this line during taxi to ensure wing tip clearance ---YOU HAVE A YELLOW LINE PARALLELING THE FUEL ISLAND, ABOUT FIVE FEET FROM THE FUEL PUMPS. I do not know of many aircraft with wingspans less than five feet. I was told it was to mark the edge of the safe distance from the fuel pumps. You would have been better off with no markings. There should have been lines radiating away from the fuel center such that aircraft could see the area needed for wing clearance, as per AIM 2-3-5 (d) shoulder markings or a yellow line which would comply with AIM 2-3-4 (b), as noted above. Double yellow lines are used to show the edges of the taxi way, not single lines as you had at that location. Most pilots are trained to keep there nose wheels on the center line and most aviation fuel islands have yellow lines which lead the aircraft to a safe distance from the fuel area for all but the largest wingspans.

Most fuel depots have safety poles on either end, as does Tucson. The problem I have, is the fact that they have yellow lights, shinning near a pole painted flat yellow with black bands around it. Nothing could make it harder to see at night. Most hunters and animal biologists understand that deer and other lower forms of animals, which rely on the rods in their eyes to see with, have extreme difficulty seeing anything broken with a pattern. We humans also rely on rods for our primary vision in the dark at night. I understand the need for poor lighting and yellow lights in Tucson are due to the local observatories. I also understand the markings on the poles might be standard and required to some extent. My suggestions are to use some yellow reflective tape between the black stripes or increase the lighting around the fuel island.

Clearly these three points were the primary cause of the event, but what other contingencies may have come into play. What other factors may have reduced the likelihood of an incident? What lessons can be learned?

The above incident occurred at the end of two days of flying. We had been flying at 8,000 ft. We had water but did not drink any. We had an oxygen bottle, but did not use it. We landed about one hour after dark and had been flying into the sun. A pilot should not always expect remote and none non-towered airports to comply with regulations. The more remote the airport, the more likely this is to be true. It was the end of a long flight.

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