Powerline detection system FAA certified for Bell 206

 - January 30, 2007, 11:05 AM

Some three-and-a-half years ago, Safe Flight Instrument of White Plains, N.Y., received supplemental type certification for its Powerline Detection System (PDS) on the company’s own Aerospatiale SA341G Gazelle. Since then the Safe Flight system has been certified and installed on Eurocopter AS 350s, EC 135s and AS 365s and Mil Mi-17s flying in Australia, Korea, Russia, South Africa, Switzerland and the U.S.
The Bell 206 JetRanger is the newest helicopter to join this group.

Earlier this year, AIN flew Safe Flight’s Bell 206B-3, which the company used to get the STC for the model. New to the PDS in the JetRanger is an amplifier and antenna coupler, which extends the detection range, according to the company.

Like the system certified in the Gazelle in 2001, the current version of the PDS senses only “live” power lines–those with electricity coursing through their wires–by detecting the electromagnetic field the current generates. The greater the electrical power in the lines, the farther away the system will detect them.

When the system senses an electromagnetic field, it illuminates the red “warn” half of the annunciator on the PDS detection/display unit mounted on the instrument panel and simultaneously triggers an audio signal in the headset that sounds similar to the clicking of a Geiger counter. The frequency of the clicking increases as the helicopter gets closer to the detected power line.

The system includes a mute switch to silence the audio warning only; when the mute function is engaged, the yellow “mute” portion of the annunciator illuminates. A gain control allows the pilot to reduce the sensitivity of the unit when flying over “noisy” areas, those with a heavy concentration of power lines. Before the company installed the gain control, flying over such areas at a low enough altitude triggered almost constant warnings.

Our flight with Adrian Rosenberg, Safe Flight helicopter pilot and assistant engineer, demonstrated the value and limitations of the system. We flew about midday in a cloudless sky with unlimited visibility over snow-covered terrain in northern New Jersey. In other words, in excellent flying conditions–not the kind in which one would expect to need a power line detection system. However, although we could see electrical towers a long way off, we frequently could not see the power lines themselves until we were almost directly overhead, and sometimes even then the lines would blend into the background. Meanwhile, the Safe Flight device worked as designed, clicking away in our headsets and illuminating the red warning light.

System Limitations
The obvious downside of the system is that it cannot detect “cold” lines, those that do not have electricity flowing through them. Since there is no way to know which lines have power and which don’t, seeing and avoiding power lines still requires pilot vigilance. The placard installed next to the Powerline Detection System display unit emphasizes the point: “Warning: The PDS is a pilot aid only and should not be relied upon as a sole means of avoiding power lines.” The system also does not warn of radio and cellphone towers, microwave relay arrays and radar antennas.

Another limitation of the system is that it does not provide an indication of the location of the source of a warning. A detected power line could be directly in front of your direction of flight or at an angle on either side, above, below or at your level. In addition, more than one power line could be triggering the warning.

Despite these limitations, the PDS provides a good early warning of live wires. The system triggers its alert well before a power line is a hazard to flight. If you’re nap of the earth when the audio begins ticking rapidly, you know it’s time to take immediate evasive action if you haven’t spotted the detected power line yet.

System Specifications
The PDS is approved for the complete range of Bell 206s. Price (uninstalled) is $11,800. A typical installation takes a maximum of two days, with the cost depending on the labor rate. Because the Powerline Detection System is a receiver, field approvals are usually possible. Safe Flight is currently developing a network of authorized dealers and installers to distribute the PDS.

The PDS, complete with antenna, detection/display unit, amplifier and wiring, weighs three pounds. The Bell 407 is covered under the same STC as the Bell 206 series but will not be approved until EMI testing is completed.