A Deep Dive into Engineering to Help Save Lives from the Sky

The Challenge of Certifying SAR Aircraft

 Perhaps the greatest operational challenge for airborne SAR is transforming a commercial aircraft into a search and rescue mission aircraft. It requires a multidisciplinary engineering team that covers many different areas including structural analysis, avionics, system safety and reliability, cabin safety, mechanical systems, aerodynamics, and other specialties. All these areas are needed in order substantiate and approve a modification. 

 A related challenge is taking an aircraft intended to perform civil passenger transport operations and converting it, and more importantly, approving it to conduct SAR operations. “The civil regulations aren’t necessarily built to support that,” according to Paul. So, what’s required is negotiating an acceptable safety standard with the responsible regulatory agency like Transport Canada. 

 The modifications require making changes to nearly every system on the aircraft, some of them significantly. This requires extremely tight coordination within the operations group. It also helps if operations, the Approved Maintenance Organization (AMO) and the Design Approval Organization (DAO) all under one roof, as is the case with PAL Aerospace. 

 A follow-on challenge is then mapping all of those modification onto the airworthiness requirements for cabin safety of the aircraft. So, in conjunction with the basic SAR operations, things like oxygen requirements, flammability, and smoke clearance—all those normal things to be considered in a normal civil certification—must be overlaid with SARS operations. 

Missionizing an Aircraft for SAR

The primary way in which an aircraft is missionized for SAR is by adapting the fuselage to accommodate drop hatches, rafts and other specialized equipment specific to SAR missions. There are also some other modifications that are in common with other missionized aircraft, such as adding an antenna suite, camera or radar pod. But the modification that poses the greatest challenge to missionizing an aircraft is the drop hatch. 

One of the questions posed in the broadcast is how do you ensure there is structural integrity and the load redistributions are managed effectively when introducing a large opening like the drop hatch in the fuselage? Because it is a structural challenge to equip aircraft with those sorts of structural changes. Without giving away too much, one approach, according to Kyle Corbin, Structural Project Engineer, is that “the pressure boundary is extended up to the floor of the aircraft to give access for dropping or jettisoning stores in flight.” By extending the pressure boundary to the aircraft floor, PAL Aerospace enables faster and safer deployment of survival gear or emergency supplies mid-flight, which is critical in time-sensitive rescue missions where every second counts. To gain more insight into this and other challenges, you are encouraged you to watch the broadcast here. 

Adding a large opening such as the one for a drop hatch, the critical load paths of different elements, stringers, frames, intercostal, etc. must be altered to accommodate it. This impacts critical load cases for the whole empennage and fuselage area. 

 Airworthiness compliance also plays a critical role in SAR aircraft missionization. For example, cabin configurations are a critical part of SAR missionization. How are layouts designed for crew efficiency and safety, especially during high-stress operations? The SAR capability is really driven by the payload deployment system. So, there’s workstations, operator station and equipment racks that all have to come together and meet all the cabin safety requirements. PAL Aerospace has 30 years of experience here, so they’ve got some fairly mature cabin layouts that work well. 

Testing for Readiness

Once an aircraft is missionized, it must be tested. First up? Aerodynamics. It’s a critical factor when it comes to aircraft modifications—especially for SAR—and it must be tested. And testing must be all encompassing, including things like airflow disruptions, handling, stability, control and performance. 

 Since a lot of the equipment is somewhat novel in its shape, the ability to test using modeling methods is limited, and will therefore require experimental flight testing. And the safest way to do that is with the “build up” approach. It starts with a single modification, the one with the least risk possible, and build it up from there through a series of experimental flight tests. 

 The first test is the drop hatch, without considering jettisoning stores. The only thing tested here is the changes to the exterior shape of the aircraft, which includes the fairings and so on around the drop hatch. The point of this flight test would be to clear the airworthiness requirements. Stability, control, and performance data are collected during the test. 

 The next test might be with the equipment necessary for drop stores. Then perhaps a series of flight tests involving placing these cameras and other critical safety items. After that configuration, there’s another flight test involving dropping essentially inert dummy stores. 

 The ultimate goal is a test flight for certification, which uses live stores and has all the features involved. It all builds up to the final configuration. 

The Role of AIMS-ISR in SAR Success

A key to SAR mission success is drop accuracy. One way to ensure that is with an intelligence, surveillance, and reconnaissance (ISR) system. And in the case of  PAL Aerospace, that’s the CarteNav AIMS-ISR. 

 According to Chief Pilot Colby Mitchell, “with the AIMS-ISR system on these aircraft, we had procedures in place from other aircraft, but this was obviously something new. So, a lot of the procedures had to be revamped a little bit for our operations. One of the big ones of course was that we just ended up having a single drop hatch tube instead of specific drop tubes, for example, smokes and flares. So, there is a modification of procedures for that.” 

 As a result of these modified procedures, PAL Aerospace is able to use MX-15 and EO in the ISR to capture and identify targets a lot sooner. That enables the SAR mission to get a marine vessel to the target a lot quicker than having to fly directly over the target to get a drop location. In this way, search and rescue assets can to the location sooner. And of course, AIMS-ISR provides the technical data that the operators in the back need. 

PAL Aerospace’s Approach to SAR Engineering

The PAL Aerospace engineering group covers design, engineering, and airworthiness certification required with any SAR modifications to an aircraft, and has done so for 30+ years. And PAL Aerospace has the capability to perform all the modifications at the company’s hangars 

 PAL Aerospace has developed the capabilities to navigate regulatory frameworks, such as addressing special conditions, damage tolerance, etc. According to Trevor Mulder, Engineering Manager, “PAL Aerospace engineering is a Transport Canada DAO, so we’re very familiar. We’ve been doing mod work for a very long time. We’ve got several delegates in-house, so we’re pretty good at navigating the regulatory framework.” 

 PAL Aerospace has all the right engineering disciplines to move from design, analysis, test, substantiation, to cover the full scope of the modification to the aircraft. The company not only leverages experience with the Canadian regulator, Transport Canada, for domestic clients, but also has relationships with foreign airworthiness regulators like the FAA, EASA, and the CAA for international. 

 If you would like to learn more about airborne SAR at PAL Aerospace, you are encouraged you to check out the Airborne SAR broadcast here. Or, if you would like to contact PAL Aerospace directly, you can reach us here.