HUMS Ascension

"Helicopters are really a bunch of parts flying in relatively close formation; all rotating around a different axis. Things work well until one of the parts breaks formation."

- Anon

Helicopter operators are HUMS-ing a happy tune as advancements in technology continue to improve safety while saving time and money in the maintenance shop.

It’s been said that flying a helicopter is like simultaneously patting your head and rubbing your stomach — a real test of a pilot’s coordination. Well, if that’s true, then maintaining one is like patting your head and rubbing your stomach while balancing on one leg — doable, but it takes considerable effort.

Helicopters require significantly more maintenance than their fixed-wing cousins because they’re significantly more complex. As "Mr. Anon" pointed out, with parts wanting to go off in different directions, it’s a wonder the darn things fly at all. Just look at a modern helicopter’s transmission and rotor system: you’ve got up to three engines mounted in one direction with drive shafts and gears going another direction to drive a hub that’s got more moving parts than a Swiss watch, which needs to hold on to long rotor blades that have to twist and turn to carry the weight of the whole machine while centrifugal forces try to rip them off the hub. And you thought your life was stressful....

And that’s just one system. Today’s helicopters have volumes of parts, pieces and systems that all need constant care and attention. And even with all that, parts fail and catastrophic things happen.

HUMS — Just Tell Me Where It Hurts

Health and Usage Monitoring Systems (HUMS) were introduced in the civilian helicopter market in 1991. That’s when the first flight of a certified HUMS equipped helicopter was completed on an offshore helicopter in the North Sea. "The real strong motivation was safety," explained Andy Heather, technical director, GE Aviation. "It came out of some high profile incidents — a lot of pressure from the oil companies to do something about the safety record of the vehicles that their workers were flying to the oil rigs."

A HUMS installation places a variety of sensors in critical areas throughout an airframe, powertrain and rotor system to actively monitor the "health" of these key components. While monitoring systems have been developed for fixed-wing aircraft, it’s the helicopter operators who benefit most from the system’s ability to not only record engine and gearbox performance, but to also provide rotor track and balance data.

Once collected, that data can not only be used to monitor system health, it can also be used to modify both required maintenance intervals and procedures and the flight crew’s operational actions. In addition, by catching problems before they progress beyond a critical point, HUMS data can help extend the service life of critical components.

How has HUMS worked? Well, statistics prove that since the introduction of HUMS, the ratio of the number of helicopter accidents caused by mechanical failures have reduced by more than half in comparison to earlier accident data. You can’t ask for a better endorsement or ROI than that.

Safety First, But Saving Money is a Very Close Second

The reports from the "reduced maintenance costs" front are just as encouraging. "When the Army used our system on a battalion in Iraq right alongside a sister battalion that didn’t have our equipment, the customer had a dramatic measurement of HUMS benefits," explained Kip Freeman, business director, Government Systems, Goodrich Sensors and Imaging Systems. "The unit flying with our system set a new record for the most hours flown by a battalion within a 12-month time frame. They were able to fly 27 percent more missions than their sister division.

"The Army documented a minimum $45 million in maintenance labor, flight and parts savings," he said. "They were also able to eliminate the need to replace engines and gearboxes due to the accurate monitoring the [HUMS] system provided on those components. We also eliminated hundreds of pre- and post-maintenance functional flight checks due to the sophistication of the HUMS system and the information it is able to provide."

"It’s not only that the system gives what has been a truly amazing safety record for the aircraft that have been fitted, but people want to get more value from the information that is available now," Heather added. "As a business, while safety is clearly really, really important, the bottom line to the operator is their operating costs. So how do you use this equipment to effectively make your operations more efficient? How do you improve availability? How do you reduce scheduled and unscheduled maintenance costs?"

"I would say that the biggest change what we are experiencing since the product was introduced is the significant increase in demonstrated results our system is delivering to our customers," said Bill Lawler, VP sales & marketing, Intelligent Automation Corporation (IAC). "From virtually eliminating rotor track and balance maintenance test flights to the early detection of component faults our HUMS is helping to change the way maintenance is done today.

"Mechanics that use our system love it," he added. "It reduces their workload and finds faults that current maintenance and procedures can’t find."

HUMS — Not Getting Older; Getting Better

While today’s HUMS can do more to actually improve both safety and maintenance procedures than its originators imagined, the best, as they say, is yet to come. Fifteen or 20 years ago, companies were pushing the boundaries of technology just to put systems of this complexity on the aircraft. Today, they are not only making HUMS equipment smaller, lighter, more accurate and less costly, they are also finding new ways to make it easier to extract more information, and then turn that added information into additional benefits.

One big step that the companies that manufacture HUMS equipment have made has been to find ways to offset the "maintenance penalty" that installing these sophisticated systems caused early on.

"When we first fitted these systems it was really all about safety," Heather said. "The philosophy was, ‘If you could monitor something, you should monitor it.’ That led to some very complex installations and the optimum economic installation may not have made it so complex."

Heather explained that every sensor, every wire, every connector and every box you put on an aircraft incurs a maintenance penalty in its own right. The HUMS itself has to be maintained. "Probably from day one that you install a HUMS you are arguably making the maintenance penalty for the aircraft worse until you start to use the information and get some net positive benefits," he said. "Today we are seeing much simpler installations on aircraft.

"When we fitted HUMS to the U.K. military Chinooks, I think we put over 45 vibration sensors on it. The most recent installation we did for the Special Operations guys in the States probably had closer to 30," Heather said. "With what we know now that’s pretty much giving us a similar level of health management, but you have far fewer wires, sensors, boxes and you pay much less of a weight and maintenance penalty."

IAC’s new SuperHUMS system is an example of a new-generation system that takes advantage of the latest in hardware and software. "We just introduced the pioneering SuperHUMS product line, which is a revolutionary advancement in diagnostic technology for aircraft condition based maintenance applications," Lawler explained. "The patent pending reconfigurable computing architecture features real-time processing using the latest Virtex-4 FPGA (Field Programmable Gate Array) and XtremeDSP technology.

"It delivers more than 10 times the performance at about the same price as our previous generation HUMS," he said. "We are also integrating SuperHUMS with flight operations quality assurance (FOQA), eliminating the need for another stand-alone data acquisition unit."

How can you do more with less? HUMS developers are making some significant inroads with something called "data fusion." Simply, data fusion is finding ways to get the information you need from the sources that are already on the aircraft.

"A few years back we added a cockpit voice flight data recorder into the system as a logical integration of a crash worthy memory to hold all the information we monitor for incident investigations," Freeman said. "This complements the classical flight data acquisition unit functions that are already integrated into our monitor system.

"We are also providing integrated centralized maintenance data computer functionality into one model of our HUMS to act as the source of all aircraft health information, including all the built-in test data from other avionics systems."

"By fusing together information that is already available on the aircraft’s digital databases you can derive or infer the information you need about another system without having to install a dedicated sensor," Heather said. "On an aircraft with a flight data recorder you’ve got many, many parameters already available. You just have to collect them.

"GE is using that technology a lot on fixed-wing military jets right now," he continued. "The customer wants to monitor stress and strain in the aircraft structure. Installing strain gauge sensors is a fairly unreliable technology. We’ve developed techniques that derive that same information from the pilot’s stick position, bank angle, altitude, airspeed and all the other aircraft parameters we already have available."

Getting All that HUMS Has to Give

You know the old saying, "If a tree falls in the woods and no one hears it, does it make a sound?" Well, it’s sort of the same with that data that’s gathered by a HUMS installation. "At the end of the day, if somebody fits a HUMS and collects the data and nobody ever looks at it — frankly there’s no value in it at all," Heather said. "The only value is if the data is analyzed and somebody acts upon it."

So GE Aviation and other major HUMS providers are putting a lot of effort behind finding new and easier ways for operators to collect, analyze and understand what their HUMS sensors are telling them.

"As HUMS vendors we started off thinking our job was to supply a box," Heather added, "then we realized our job was actually to provide a box, the service and the data infrastructure that allows you [operator] to automate that data for interpretation."

Heather said that change in strategy has been in response to the change in the HUMS customer profile. Until recently, HUMS was the tool of the military and large commercial helicopter operators. Both of whom had large staffs of technicians who specialized in taking all of those squiggly lines of data that came from a HUMS sensor and translating it into useful diagnostic and maintenance information.

"Now we see situations like with the AugustaWestland 139 where those aircraft are going out to more VIP operations where they have possibly just one aircraft or a Medivac operation where they may have two or three," he said. "These guys don’t have big technical departments with a HUMS specialist in-house."

So to help make HUMS information beneficial to corporate and special use operators, GE Aviation is developing and providing new automated analytical tools and services specifically tailored to meet their particular needs. "We have a big central data infrastructure where all of our customer data comes to. Helping our customers exploit that data has become as important to us as the development of the physical pieces of hardware on the aircraft," Heather added.

HUMS 2015

What’s next? As HUMS suppliers, airframe OEMs and operators continue to find new ways to extract, analyze and use the data the systems collect, the sky is the proverbial limit. But, a couple concepts are especially intriguing.

The first is one that GE Aviation is working on now. It addresses reducing the considerable amount of labor hours currently needed by technicians to physically extract the collected HUMS data from the aircraft. Typically, that process entails taking a data cartridge off the aircraft and downloading the information into a computer for processing or sharing.

What GE intends to do is to use a process that is currently in use to monitor the health and location of both rail and military land vehicles. "The rail locomotives use the GSM (global system for mobile communications) network to simply send their data back to the base station each day," Heather said. "The operator just logs on to the Internet and he can see the health and status of all the trains.

"This really isn’t rocket science any more. The airlines are using something similar automated methods of transferring data when they pull up to the gate," he said. "It just hasn’t been widely applied to HUMS and rotorcraft yet."

The other new advancement that sounds exciting is the emergence of HUMS technology in the actual manufacturing and testing of new aircraft. "We never expected that the production teams at the OEMs would ask us to use the HUMS to ATP (Acceptance Test Procedure) the entire aircraft when they completed assembly," Freeman said. "I am sure we will have other surprises by many other intelligent people out there who are focused on improving their own area of responsibility and the continuous improvement of their fleet management."