All gliders should be required to operate with devices that alert air traffic controllers and other aircraft to their presence, federal regulators recommended Tuesday, citing 60 near-collisions over the past two decades.
Gliders and other aircraft without engine-driven electrical systems are exempt from a rule the Federal Aviation Administration imposed in 1988 requiring transponders for aircraft that operate near primary airports and in airspace above 10,000 feet.
NTSB Chairman Mark Rosenker recommended in a March 31 letter to the board that the glider exemption be eliminated in part because of an NTSB investigation into a collision between a glider and a private jet about 40 miles southeast of Reno in August 2006.
In that case, the glider pilot — who parachuted to safety — had a transponder on his aircraft but had turned it off to conserve battery power. The Hawker 800XP airplane he collided with was significantly damaged but was able to land safely at Reno-Tahoe International Airport.
"As evidenced by this accident, aircraft that are not using or not equipped with transponders and are operating in areas transited by air carrier traffic represent a collision hazard," Rosenker wrote in the letter first made public on Tuesday.
"This hazard has persisted more than 20 years since the Safety Board initially expressed concern," he said.
Many gliders object to required use of transponders, saying they are expensive and energy-consuming.
Of the 60 near mid-air collisions from 1988 to 2007, nine occurred in northern Nevada. That's due primarily to the large number of gliders that fly along the Sierra's eastern front where thermal air flows create what enthusiasts describe as "world-class" gliding conditions.
Other frequent sites of near-collisions were Chicago and Washington, D.C., with four each. Colorado Springs, Colo., had three.
More than 10 years before the latest incident, the FAA's Reno Flight Standards District Office had warned FAA investigators that gliders were invisible to radar because they do not have transponders.
"In addition, due to the design of the gliders, they are very difficult to see unless the air carrier is very close to them, which may be too late to avoid the glider," the office manager wrote in a memo April 11, 1997.
In the latest accident, both pilots reported they saw each other for only a second or less before impact.
The 1997 memo said that the FAA flight office in Reno suggested gliders carry transponders, communicate with the control tower at the airport or both, but that "the glider community does not want to adopt the FAA's suggestions."
In the new recommendation, the NTSB praised the glider community and others for taking "steps in the right direction" to educate pilots about dangers and take safety precautions.
But the NTSB concluded that "transponders are critical to alerting pilots and controllers to the presence of nearby traffic, so that collisions can be avoided and that gliders should not be exempt from the transponder requirements."
The FAA has 90 days to respond to the NTSB's recommendations, FAA spokesman Ian Gregor said.
"We take NTSB recommendations very seriously," he said from Los Angeles.
Leaders of the Soaring Society of America, based in Hobbs, N.M., and other gliding enthusiasts oppose the NTSB's move. They advocate alternatives including increasing awareness among pilots of areas where gliders are often in use and implementing technology already used in some parts of Europe that provides low-cost, real-time information to pilots.
"The SSA is disappointed that the NTSB took a very narrow view of the causal factors and did not address some of the changes we specifically recommended," said Stephen Northcraft, chairman of the group's government liaison committee.
Leo Montejo, president of the Minden Soaring Club south of Reno, advocates the use of transponders but said they should be allowed to be turned off when flying over remote areas away from normal air traffic patterns.
Most modern gliders have solar-powered batteries that help conserve power, but even those don't help on longer flights, which can stretch eight hours and cover 500 miles, he said.
"Having a transponder on all the time becomes a real problem with energy conservation on your glider," he said.
Fred La Sor, an owner of Soaring NV in Minden who helped develop new safety plans for the Reno area after the last accident, said it costs $2,200 to $3,000 to put transponders on most gliders.
Besides, he said, most collisions or close calls involve not a glider and a jet, but two gliders — something he said transponders would not affect.