Danger! Stay Away : Avionics Challenges in Rotary Wing Aircraft

Manufacturers and outfitters of rotary wing aircraft face many unique challenges when it comes to selecting and installing avionics. Helicopters, like their fixed wing counterparts have numerous and often multiple types of missions. When it comes to...


Did you ever notice the large (usually in red) placard located near the tail rotor on most rotorcraft? Up until recent years, it was my opinion that this was a general statement pertinent to the overall machine. Contrary to popular beliefs in the fixed wing world, helicopters are aircraft too!

Manufacturers and outfitters of rotary wing aircraft face many unique challenges when it comes to selecting and installing avionics. Helicopters, like their fixed wing counterparts have numerous and often multiple types of missions. One day the flight log may reveal transporting VIPs to a company board meeting and the next day flying wildlife management biologists over a stretch of desert. When it comes to equipment selection it soon becomes clear that one package will not accomplish all the requirements.

In the United States the Federal Aviation Administration regulations governing rotor wing aircraft are found in either Federal Air Regulations (FAR) Part 27 for normal category helicopters and Part 29 governs those machines used in a transport capacity.

Equipment Requirements

The minimum required flight deck equipment for a normal category rotorcraft includes an airspeed indicator, altimeter, and a magnetic direction indicator.

Machines that fall into the transport category also require the above mentioned equipment along with a clock, free air temperature indicator, vertical speed indicator, nontumbling gyroscopic attitude, and rate of turn displays with a capability to operate at least 30 minutes independently of normal electrical power.

Operators of the classic Bell 47 with a primary mission of herding cattle might find the minimum required instruments are adequate to fulfill the intended work scope. Airframe manufacturers catering to the VIP transport industry are more likely to produce equipment with an avionics suite that will rival those found in top-end business jets. In fact the AB139 was the first aircraft certified with the Honeywell EPIC flight deck. After all, when the chief executive of a Fortune 100 qualifier gets off the corporate Gulfstream and needs to get from the airport to the company headquarters, a machine that will provide a “continuation of the mission” is preferable to giving the CEO a “helicopter ride.”

Technology in the world of rotary flight is advancing at the same rate as elsewhere in the aviation industry with electro mechanical devices being replaced by those run by software programs. Global positioning systems (GPS) from a simple handheld up to dual units interfaced through flight management systems (FMS) are now the most frequent means of position determination. Many technicians have already expanded their toolboxes to include a PC to allow the viewing of manufacturers’ technical manuals or interact with various airframe and engine electronic control units (ECU) as a means of fault finding or trend monitoring.

Historically the word “avionics” has been associated with radio communications, auto flight, and navigation; however, the most basic definition is “electronics as applied to aviation.” Many maintenance technicians have gotten in the habit of contacting the “avionics person” anytime a black box with more than two wires could be a culprit.

Maintenance Troubleshooting

Standard repair practices are often included in maintenance documents and are an excellent source of precautions, as well as techniques to assist in most troubleshooting projects. The utilization of sophisticated test equipment is in many cases not needed when determining the serviceability of a line replaceable unit (LRU). In fact the majority of troubleshooting at the flight line level can be accomplished with a basic volt ohm meter (VOM). Even with the Honeywell EPIC system, the aircraft inputs are analog (variable voltage, frequency, or current), digital (such as an ARINC 429 data bus), or discrete (ON = 11-14v DC, OFF = 0-3v DC) and all can be tested either by using the central maintenance computer contained within EPIC or as mentioned easily procurable test equipment.

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