What Is Aircraft Health Monitoring?

What is Aircraft Health Monitoring? and what do aircraft health monitoring engineers do?

Let’s imagine you are an aircraft operator or an airline that operates a fleet of aircraft. To keep your aircraft flying on time and on the planned schedules, you’ll need to ensure that your flying machines are always airworthy with the highest levels of dispatch reliability. Meaning that whenever you need the aircraft, you are confident the aircraft can fly and carry your passengers safely without any technical disruptions.

To begin with, regardless of whether you’ve chosen to outsource your aircraft maintenance or leave it in the capable hands of your engineers, you’ll always feel the need to foresee your aircraft health and technical performance and capabilities. Why? Because probably the last thing you want to see in the aircraft maintenance log during an operational day is a technical fault written up by pilots or line maintenance engineers. As a rule of thumb in commercial aviation, whenever a maintenance fault or defect is reported against the aircraft, there should be a corrective action taken that clearly justifies the airworthiness of the aircraft post rectification, or there should be a regulatory document that allows the aircraft to fly with the defect. In either case, a significant amount of time and man-hours should be allocated to find and troubleshoot the root cause which are highly likely to cause you operational disruptions, technical delays, and the loss of passenger satisfaction.

This is when aircraft health monitoring (HM) comes into play. A preventive maintenance department that is becoming an inseparable part of leading airlines. HM helps you foresee the upcoming technical issues before they take place. You might be asking yourself “Is that really possible to anticipate how the aircraft is going to behave?”. Well, that might sound a bit weird, but the answer is “Yes. It is possible to foresee aircraft’s behavior.” I am using the word ‘behavior’ because as an aircraft health monitoring engineer who is dealing with the health and technical performance of the aircraft on a daily basis, I consider them as human beings with attitudes and I believe they behave to how they are treated by humans. They communicate. HM engineers ask them questions and ask them what they’re looking for and they reply with information. In simple words, these communications are done via CMC (Central Maintenance Computers), FHDB (Fault History Database) and QAR (Quick Access Recorder). These are the most common means of communicating with aircraft. Of course, the written language they communicate in is not like something that an average human being is used to read and it requires to be decoded first. Also, aircraft like to talk a lot. Sometimes when you ask them questions, they give you thousands of recorded bits of data and leave you with them to filter out what you want.

So health monitoring engineers communicate with aircraft through stored data in aircraft computers and filter and analyse data to monitor the aircraft’s health and technical performance. The essence of the matter to be investigated defines the depth of HM analysis. Sometimes, HM engineer is investigating a particular defect or occurrence which just happened once in a long period of time, they might need to filter out 22,000 flight parameters and thousands of record files and narrow them down to just a single recorded file that contains data they are looking for and then filter that specific record file to the second that a fault or occurrence took place. That’s just when the fun part begins. HM engineers will then have to decide which parameters and recorded signals on the QAR and FHDB they want to compare to find the root cause. Sometimes, it is required to create and set up formulas to measure different parameters in a system for comparison or investigation. If it is a fleet-wide issue to be investigated, they can set up a visual dashboard as a tool to do comparisons among several aircraft. Using these graphs, tables and formulas that get created during the investigation, trends get formed that allow operators to see which aircraft is behaving better with regards to a particular system and which one is acting, or starting to act a bit abnormal. When you compare these trends over time intervals, you can see that some aircraft defects and faults give you a heads-up before they make your aircraft AOG (Aircraft On Ground / No Dispatch).

To recap my explanation above for what Aircraft Health Monitoring Engineers do, I would say:

HM engineers are aircraft doctors who specialize in airworthiness health of aircraft and help airlines foresee aircraft defects and prevent technical disruptions by analysing aircraft systems data and setting up action plans to troubleshoot the root cause.