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Aircraft health management systems


Connected sensors collect aircraft performance data and send it to ground bases for analysis.

By Owen Davies
Contributing Writer

Bombardier Smart Link Plus keeps aircraft connected, giving operators access to real-time data to make better and faster maintenance decisions and improve aircraft availability.

Mention the Internet of Things (IoT), and many of us think of net-connected refrigerators or little boxes transmitting weather observations, warnings of structural defects in bridges, and almost anything in between.

It turns out more complex and bigger IoT devices routinely send gigabits of data for real-time analysis. If you fly a long-range business aircraft, you probably sit in one on every trip. If you fly smaller planes, your mount could be online in 2 or 3 years. In fact, it will be unless your employer has a bad case of the stingeys.

The aircraft health management systems (AHMS) now filtering down to smaller aircraft types have made executive jets and airliners the biggest and most sophisticated “things” connected to the Internet and to specialized data transmission systems.

They use sensors, many hundreds of them, to monitor the condition and operation of the aircraft’s systems and structures. All that data is sent to a box that collects and encrypts it, and then sends it to ground stations for real-time analysis.

Most data is used to help in scheduling condition-based maintenance, but urgent or emergency events are flagged for an immediate response. Many systems now automatically alert pilots of impending trouble.


The first AHMS appeared in helicopters in the 1990s as an answer to the sling-wings’ poor record of continuing airworthiness. Called health and usage monitoring systems (HUMS), they employed sensors distributed throughout the airframe to track takeoffs and landings, engine starts, winch lifts, and some information about the health of engines and transmissions. They stored their data for download after a flight.

Today, HUMS monitor the condition of major components, including all significant spinning and vibrating parts. They transmit the data to ground stations where they can be analyzed in real time.

Fixed-wing AHMS are a lot more complicated. George Tsopeis, Bombardier’s customer success manager for the Smart Link Plus AHMS and aftermarket products and services, reports that the current-generation  system monitors more than 12,000 parameters from engines, control surfaces, electrical systems, and the airframe that can reveal urgent problems or maintenance issues for the next visit to the shop.

Business aircraft manufacturers were experimenting with AHMS in the 2010s, and academics had been developing foundation technologies for them a decade before that. In 2014, Sandia Laboratories partnered with Delta Airlines and a foreign manufacturer to add 100 sensors monitoring the structural health of 9 commercial aircraft. But that experiment may have been a little behind the times, because Bombardier had rolled out its first-generation AHMS a year earlier.

All business aircraft manufacturers now offer sophisticated AHMS that carry out the same tasks and produce roughly the same data. The greatest difference is in the software that organizes and analyzes the data, and gives technicians access to it. The companies all strive to give users intuitive and efficient access to flight data and analyses. Like all software companies, they get to the same goal by different routes.

Techs who work miracles with one manufacturer’s software are likely to struggle with others.

Bizjet OEM offerings

Pratt & Whitney EngineWise provides analysis of engine operational data to better manage engine health and maintenance planning. It improves reliability and keeps maintenance costs under control.

To date, most AHMS are available only on large and very large, ocean hoppers, like the Gulfstream G400 and up, Dassault 900- and 2000-series aircraft, and Boeing Business Jets and their peers from Airbus.

Nonetheless, these systems have made a difference. A survey in pre-AHMS 2012 found that only 60% of  aircraft issues were identified by ground inspections. The other 40% occurred in the air. By 2020, the preventive maintenance made possible by AHMS had reduced in-flight issues to 30% of the total. Three years later, we would expect it to be no more than 20%.

Yet, the goal is to provide AHMS technology throughout the business aircraft fleet. Bombardier seems to be in the lead here. Its Smart Link Plus systems are available on nearly all the company’s current models, and can be retrofitted to older aircraft.

The necessary sensors are built into the planes now being delivered. All that’s needed is to add the box that collects and transmits sensor data, and subscribe to the software/service that makes it available.

With a 3-year subscription, the box is free. Operators of more than 90% of Global 7500s have signed up for it, according to program Tsopeis reports. And when subscriptions run out, the renewal rate is 100%.

Bombardier has not announced when Smart Link Plus will be available for all the company’s aircraft. However, asked whether that would be within a few years, Elza Brunelle-Yeung, senior director, strategic planning and business development, replied that it would be sooner than that. “Much sooner” seemed strongly implied.

Other business jet manufacturers should be no more than a year or 2 behind.

At this point, AHMS have become a big and fast-growing business. Including both airlines and business jets, Allied Market Research valued the AHMS market at nearly $3.6 billion in 2020, and predicted that it would grow to $7.27 billion by 2030. That works out to a compound annual growth rate of 7.65%. Other analysts have put it even higher. Markets and Markets foresaw a CAGR of 10.8% through 2025.

Options from engine OEMs

The biggest health maintenance system does not come from an airframer, and it does not cover entire aircraft. This is the EngineWise ADEM (advanced diagnostics and engine monitoring) and eFAST (enhanced flight data acquisition, storage, and transmission) combination from Pratt & Whitney (P&W).

If an aircraft is moved by reasonably contemporary P&W engines, operators can use the company’s monitoring systems to make sure they remain in top running condition – or to catch issues before they become problems. This includes executive jets ranging from the Citation Mustang and the Embraer Phenom 100/100EV, to the Airbus ACJ TwoTwenty and some ACJneo. (Many use the CFM Leap-1A.)

Add many other business aircraft to the P&W fleet – the Citation Sovereign and XLS, Dassault’s business aircraft from the Falcon 6X through the 2000 series, Gulfstream’s G400 and G600 bizjets, the Beechcraft King Air line, and even the Piaggio P.180 EVO turboprop.

However, P&W’s market is dominated by airliners. Since the EngineWise program was announced in 2017, the company has signed engine-monitoring contracts with more than 300 airlines in all parts of the world. Most of the roughly 10,000 aircraft P&W monitors are airliners.

Data processing

Foresight MX is a valuable tool for helicopter operators. It collects and transmits data to improve readiness, enhance safety, lower maintenance costs, and improve OEM support capacity.

Watching over so many airplanes is a big task. A single P&W GTF engine generates around 4 million data points in one flight. Dealing with that mass of information should become a little more efficient in the near future.

At the Farnborough International Airshow in July 2022, P&W and sister company Collins Aerospace (both are owned by Teledyne) announced a deal under which the engine manufacturer will send its data across the Collins GlobalConnect system.

As required, GlobalConnect can handle multiple data links, including traditional HF and VHF, legacy satcom, and Internet Protocol connections via broadband satellite, WiFi, and cellular. GlobalConnect will give pilots greater access to real-time data from the ground. It also will automate the acquisition of safety and performance data from the aircraft.

AHMS have greatly improved the efficiency of maintenance programs, and have reduced aircraft downtime and costs for fleet operators. They have made flightcrews and passengers safer by notifying pilots of in-flight issues before they become emergencies. This leaves one group of stakeholders to be considered.

MRO providers

In the early stages of this article, it was obvious that MROs would be heavily impacted by a technology that so has profoundly changed maintenance operations. It also was wrong.

Terry Gallaher, avionics tech manager at West Star Aviation GJT (Grand Junction CO), reports that he has seen only one change. “For the past couple of years, we have been installing data collection and transmission units in 2 Falcon 2000-series aircraft, on average, each month,” he explains. “This is as part of regular maintenance inspections, not a separate job.”

These are upgrades, he adds, not all-new work. The early systems were designed to use 2G networks. They were replaced when 3G came out, and are now being upgraded to use 4G networks.

Peter Zaccagnino is CEO at Park City Aviators, a Part 91 company based at HCR (Heber City UT). PC manages a diverse range of business jets for private operators. Zaccagnino concurs, “We have not seen much impact from AHMS on maintenance practices. In one of the Falcons, a sensor occasionally reports that the APU door is open. It gets checked to see whether it is only a nuisance squawk or something is happening. There are several things like that, nothing major.”

Otherwise, maintenance jobs arrive when the owner needs something done, just as they always have. Zaccagnino does note that one AHMS has slightly changed operating procedures for the pilots. “They are slower to start up the electrical systems,” he says. “They are careful to give the aircraft time to complete each process before starting the next. If they hurry it, sensors can disappear from the system.”

In the horizon

In the near future, we can expect to see some obvious changes in the AHMS universe. New(ish) materials will require planes to carry more sensors. Composite structures, which make up half or more of the largest executive jets adapted from Boeing and Airbus airliners, can be damaged in ways invisible from outside. Even when problems can be seen, a small surface defect often hides  more extensive internal weakness. Embedded sensors are the only reliable way to detect such issues short of major inspections, and they can do it as soon as the defect appears.

Data transmission will need another upgrade – this time to 5G systems. We can expect to see such changes often in the years ahead. Telecoms already are working on 8G systems.

New data compression techniques are likely to reduce the load on data transmission units even as their processors grow more powerful. This will shift a little of the computing to the ground stations, where technological improvements compensate by speeding data decompression and analysis. This will be just as well, as all those new sensors deliver still larger masses of information to be sent and digested.

Here is the bottom line

In the years ahead, fleet operators will find their expenses falling as more sophisticated AHMS further reduce aircraft downtime by converting what once might have become repairs into routine maintenance issues. Pilots and passengers will be even safer because fewer potential problems will slip through to cause trouble in the air. And when emergencies do occur, the AHMS will notify front-seaters while there is still time to deal with them gracefully.

And these benefits will flow down to those who fly smaller, shorter-range bizjets, making the air safer for all.

It is all too easy to think of changes that could make the future worse for aviation and those who make it work. This one will be very welcome.

OwenOwen Davies is a veteran freelance writer specializing in technology. He has been a futurist at Forecasting International and TechCast Global.