Bird strikes seem to be in the news a lot recently, especially since geese brought down a US Airways Airbus 320, leading to the "miracle on the Hudson" and the article I wrote in the May 2009 issue of Flying about Things That Go Bump (Often at Night). There are other objects in the sky that present a collision hazard to powered airplanes, usually during daylight hours. Some present very little risk. For example, even though hundreds of weather balloons are launched each day in North America, there is no record of a collision between an airplane and a balloon or its instrument package. The balloons climb at around 1,000 feet per minute, and the instrument package, which generally does not weigh much more than a pound, descends rapidly under a small parachute. The weather observer is required to postpone the launch if there is an aircraft in the area, and to coordinate the release with ATC if it is within five miles of a controlled airport.
Skydivers are another matter. While collisions between airplanes and skydivers are rare, when an airplane strikes something weighing around 200 pounds, the results are often fatal for the skydiver, the airplane's occupants or both. In November 1993, a Piper PA-28-161 collided with a free-falling skydiver while in cruise flight over the Northampton, Massachusetts, airport. The NTSB report states that the pilot of the jump aircraft contacted Bradley Approach Control immediately after departing Northampton Airport and informed the controller he was climbing to 8,000 feet with jumpers. The controller had already assigned a discrete transponder code earlier in the day and requested the pilot to inform him one minute prior to releasing the jumpers, which he did.
The controller made the usual transmission on the approach control frequency: "Attention all aircraft, one minute to parachute jump, vicinity of Northampton Airport, surface to 8,000 feet." Neither the controller nor his supervisor observed any conflicting traffic at the time. The first jumper out the door observed an airplane coming right at him about five seconds later. He thought he would miss the airplane but collided with the tail. The skydiver survived with serious injuries, but the Piper went out of control and all four people on board were killed. The NTSB inspected the radios on the Piper and determined that the pilot had been monitoring the tower frequency at Bradley International Airport.
This accident helps to illustrate the steps pilots can take to reduce the risk of a collision with a skydiver:
• Check your sectional — airports with jump activities have a small blue parachute superimposed over the terrain in the vicinity of the airport. Information is also published in the Airport/Facility Directory.
• Check notams — notams are issued for jump activity in other locations.
• Be alert even at higher altitudes — jumpers may exit the airplane at altitudes up to 15,000 feet.
• Monitor the appropriate frequency — a warning is generally given before the jump both on the CTAF for the airport being used and over the appropriate approach control frequency.
• Don't relax at night — jumps are occasionally conducted at night.
• Alter course — because parachute jumping generally occurs within a few miles of an airport, the risk of a collision can be eliminated simply by adjusting your course to avoid parachute jumping areas on low-altitude flights if you are not planning to land at that airport.
Gliders represent a third risk to airplanes, as illustrated by a collision between a glider and a Hawker 800XP that occurred south of Reno, Nevada. The Hawker was descending out of 16,000 feet on approach to Reno when the captain saw a glider out of the corner of her eye. She barely had time to try to avoid the glider when it collided with the nose of the Hawker. While the jet was substantially damaged and one engine flamed out, the crew managed to successfully accomplish a gear-up landing at Carson City, Nevada. The glider pilot bailed out of his crippled glider.
While glider operations are also marked on sectional charts, gliders can operate over a large area (current record is 1,554 miles) and at very high altitudes (current record is 50,671 feet). Due to their construction, they are usually invisible to radar. While some high-performance gliders have battery-powered transponders, the pilots often turn the transponder off to save battery power for the radio, making the glider invisible to TCAS-equipped airplanes.
According to the NTSB report, the glider pilot stated that he was not sure of the remaining charge on the battery due to previous flights that day, so he had turned the transponder off to reserve his battery power for the radio. Gliders are not required to have transponders unless they are operating above 18,000 feet and have not activated a glider operation box with ATC. While the rules do specify that "each person operating an aircraft equipped with an operable ATC transponder … shall operate the transponder, including Mode C equipment, if installed," this rule does not take into account the limitations of a transponder being run off a battery.
The NTSB researched the NASA Aviation Safety Reporting System data and discovered that the greatest number of near-miss reports between jet aircraft and gliders occurred in the airspace around Reno. This is not unexpected, because Reno has one of the highest concentrations of high-performance sailplanes in the country, with three soaring operations within a 35 nm radius of the Reno airport. The collision occurred at a location popular with soaring pilots, called Pine Nut Ridge, where there is often good lift from thermals. That area is in a corridor used by ATC when traffic at Reno is arriving and departing to the south.
I experienced a similar situation when I got checked out in the Civil Air Patrol Schweizer 2-33 at Pleasant Valley Airport northwest of Phoenix. It is just outside the Class B airspace and just north of a major VFR transition route. I was really concerned about the amount of traffic in the area. On one occasion, I was circling in a thermal when a turboprop went zooming past not far from me. The combination of my tight turn and my need to look at the vertical speed indicator to center in the thermal made it very unlikely I would be able to spot high-speed traffic early enough to avoid a collision.
All three glider operations in the Reno area try to educate pilots about the jet traffic in the area and encourage pilots to use a transponder. The NTSB reported that local air traffic controllers have assigned a transponder code of 0440 for gliders operating below 15,000 feet within 50 nm of Reno. However, the pilot involved in the collision was not from that area, and he had borrowed a glider from a friend, so he did not receive a briefing about jet traffic from any of the local glider operators.
As a result of this and other accidents, the NTSB has recommended that the FAA eliminate the glider transponder exemption, and that the FAA establish a national transponder code for gliders. The NTSB has also asked the Soaring Society of America to encourage its members to use transponders and communicate with ATC whenever possible. It is obviously critical that pilots be especially alert for gliders in high-glider-volume areas like Reno, but smaller glider operations can be found near many metropolitan areas, leading to a reduced, but very real, collision risk.