By: Rénald Fortier
Ingenium – Canada's Museums of Science and Innovation
“It is only with the DAIS that one can see rightly; what is essential is invisible to the eye” – A respectful look at a great Canadian aerospace invention, the Diffracto DAIS non destructive testing equipment, and a bit more, part 2
An Institute for Aerospace Research staff member conducting an inspection on a Shuttle Remote Manipulator System, or Canadarm, around 2000. National Research Council Canada.
I see you could not stay away, my reading friend. The history of the D-sight Aircraft Inspection System (DAIS), a non destructive testing equipment developed by Diffracto Limited of Windsor, Ontario, is indeed a fascinating one. Shall we pick up where we left off?
Between 1988 and 1991, the National Aeronautical Establishment (NAE), a National Research Council of Canada (NRC) branch known from 1990 onward as the Institute for Aerospace Research (IAR), conducted thousands of test inspections using the DAIS. Most of items used came from the so-called Aircraft Specimen Library, a collection of over a thousand aircraft and helicopter structural elements created some years before.
Those test inspections allowed NAE / IAR researchers to classify the various problems or conditions encountered (corrosion, cracks, impact damage, delaminations, loose or failed rivets, etc.), and identify specific areas of interest which could be checked with other non-destructive testing methods.
On one occasion, a system was adapted to permit the observation of a specimen placed under cyclic loading in a test machine. For the first time ever, researchers had a real time view of the uneven load distribution in a corrosion-damaged joint.
On several occasions, NAE / IAR researchers had to modify their approach in order to deal with items which could not be covered with the degreasing product mentioned in the first part of this article.
In one case, water mixed with a wetting agent was used to inspect the rudder of an aircraft with a fabric-covered wooden structure. The flying machine in question was an Avro Type 504 biplane trainer owned by what was then the National Aviation Museum, today’s Canada Aviation and Space Museum, in Ottawa, Ontario.
As well, NAE / IAR researchers proved that the technology developed by Diffracto could be used to identify altered Canadian and American passports and counterfeit currency. It was their hope that the technology would be of interest to police and security forces in Canada and elsewhere. Some researchers even thought that a type of device could be used to compare bite marks on victims of violent crimes. I kid you not.
No later than 1994, researchers were able to spot the complete maker’s mark of a late 17th century and early 18th century New France silversmith / gunsmith / arquebusier named Soullard, presumably Jean Soullard, on the barrel of a weapon which belonged to the Canadian War Museum. Using standard techniques, the museum’s staff could only see a letter S.
As this was taking place, Diffracto was also looking for new markets for its product. By the late 1980s, it had developed a version of its D-sight system which could inspect aircraft windshields or canopies. The firm was also investigating the use of its technology in thermal imaging and wind tunnel research.
Sadly enough, there seemed to be a market for the product Diffracto was developing. You may wish to note that what follows was tragic.
In April 1988, a Boeing Model 737 operated by an American carrier, Aloha Airlines Incorporated, suffered a massive midair explosive decompression caused by metal fatigue and corrosion. The jet-powered airliner landed in one piece, minus 5.5 or so metres (18 or so feet) of the skin of its upper fuselage, but the chief flight attendant, Clarabelle Lai Moi “C.B.” Lansing, born Ho, lost her life when she was swept out of the cabin. Her body was never found. Sixty-five or so passengers were injured, several of them seriously.
That appalling accident resulted in a huge search for corrosion damage. People using Diffracto’s devices discovered the first examples of a previously theorised but never found type of corrosion which had contributed to the Aloha Airlines disaster.
The sheer amount of work which needed to be done overwhelmed the inspection teams and the hand-held devices commonly used at the time. A D-sight based system like the one offered by Diffracto offered a potential solution to the airline industry’s problem. It was after all an easy and fast way of highlighting small distortions or deformations caused by corrosion or impacts on flat and moderately curved surfaces.
Diffracto’s D-sight system also offered a solution to another issue faced by the airline industry, namely the ever increasing importance of composite materials in airliners. Said industry was gradually realising that it would need to keep an eye out for barely visible impact damage. Able as it was to inspect large surfaces quickly and efficiently, Diffracto’s technology would allow airline technicians to identify problem areas which could be inspected in depth using other types of equipment.
Diffracto perfected its DAIS, an acronym which stands for D-sight Aircraft Inspection System, in 1991, with the help of the aforementioned IAR.
As was said (typed?) in the first part of this article, the initial version with the DAIS-1000 inspection head was resized for use on the composite elements of the fleet of McDonnell Douglas CF-188 supersonic fighters of the Canadian Forces’ Air Command. That version was funded by the Canadian Forces. A unit with a smaller viewing area and different geometry optimised for corrosion detection, the DAIS-250C (“C” for corrosion), was developed in 1993.
The United States Air Force (USAF) was sufficiently intrigued to have an American firm, ARINC Corporation, invite Diffracto and IAR for a demonstration of the corrosion detection capabilities of the DAIS, in 1992. The demonstration was done using a Boeing Model 727 test airframe.
And yes, the photograph at the beginning of the first part of this article showed that test, I think.
In 1993, a Diffracto / IAR team attending an event at the Airworthiness Assurance NDI Validation Center of the Federal Aviation Administration (FAA) took part in another demonstration. The three men did in 36 man-hours what the American agency’s airworthiness directive suggested would require close to 280 man-hours. Their results were used by other invitees to zero in on the problem areas identified by the DAIS.
The results of the 1992-93 trials were so impressive that the FAA, NRC and Transport Canada provided funding to Diffracto and IAR to develop the DAIS for corrosion testing of large airliners. That cooperative project began in 1993 and continued until 1996-97.
Incidentally, the FAA was mentioned many times in our blog / bulletin / thingee, and this since June 2018. Transport Canada, on the other hand, has been so blessed many times since October 2017, but I digress.
As the aforementioned cooperative project was taking place, the USAF and Canadian Forces provided funding for a Large Area Composite Inspection System.
In 1994-95, Diffracto and IAR thus conducted a series of field demonstrations on airliners operated by Air Canada Incorporated and two American carriers, Northwest Airlines Incorporated and United Airlines Incorporated, as well as military aircraft operated by the USAF and Royal Air Force (RAF).
European air forces involved in the EUCLID (European Cooperation for the Long Term in Defence) program conducted their own independent series of trials, in the Netherlands, using a leased DAIS unit.
All of those air forces were impressed. The Canadian device was simple to use and it provided information quickly. Better yet, it was relatively inexpensive.
As intrigued as they were by the new technology, many airlines were concerned by a variety of issues, namely
- the cost of the new equipment. The airlines could upgrade a fair amount of the equipment they already had for the cost of a single Diffracto device.
- the creation of a permanent record (photo and / or computer file). The airlines might have feared the possibility that such records could be used against them in lawsuits launched by the relatives of people killed in aircraft crashes.
- the number and classification of the people who would do the work. The airlines needed to figure out if the individuals who did the routine visual inspections or the non-destructive testing specialists who inspected potential problem areas flagged by their colleagues would carry out the DAIS inspections.
- the amount of data storage space required to preserve the images produced during the inspection of each aircraft in their sizeable fleet. Given the size of the images and the capacity of the big hard drives of the times, this was far from a trivial matter. You see, one of those big hard drives could probably not hold more than 160 or so images. I kid you not.
In any event, Diffracto was sufficiently encouraged by the results of the trials to market a commercial version of its DAIS in 1995. The potential market for a system like the DAIS was in fact simply enormous. Even relatively small air carriers could afford to buy one. After all, the airlines of the world were operating more than 2 000 aircraft completed before 1975. Corrosion was a problem all of them had to deal with.
Mind you, by then, the firm was yet again producing devices that automobile makers were using to measure and inspect parts. Most of its profits actually came from that side of the business.
In any event, again, the Canadian Forces bought two DAIS units in 1995. Among other things, they were used to inspect the entire outer surfaces of two Lockheed CP-140 Aurora maritime patrol aircraft, in 2001.
Acting on behalf of the USAF, the aforementioned ARINC acquired a DAIS unit in 1995, to inspect some of the former’s large aircraft. Better yet, the USAF acquired three DAIS units at some later point. In turn, the RAF acquired a DAIS unit in 1997-98, to inspect some of its large aircraft.
A pair of Siły Powietrzne technician examining a Sukhoi Su-22 supersonic fighter bomber using a Diffracto DAIS unit. Andrzej Katunin et al., “Automated Identification of Hidden Corrosion Based on the D-sight Technique: A Case Study on a Military Helicopter.” Sensors, 11 August 2023, 4.
In 1999, the Wojsk Lotniczych i Wojsk Obrony Powietrznej, in other words the Polish air and air defence forces, acquired a DAIS unit. Incidentally, the Polish armed forces eventually proved to be the most important foreign user of the DAIS, employing the technology to inspect its airplanes and helicopters.
I know, I know, the USAF had more DAIS units. It simply did not use them as much, I think.
The training in DAIS operation and image interpretation that the personnel from the Canadian Forces and foreign air forces received was developed and provided by IAR.
The fact that only air forces used DAIS units to regularly inspected their aircraft was interesting. The issues which concerned the airline industry did not seem to affect them.
Meanwhile, Transport Canada funded the development of a DAIS unit which could be operated by a single individual and did not produce a permanent record. The prototype of that system, which was designed to answer some of the concerns expressed by the airline industry, was field tested in 1997, on a pair of airliners.
Sadly, Transport Canada’s financial support ended that same year. Faced with a definite lack of interest on the part of the airlines, the airliner manufacturers saw no reason to approve the DAIS as an inspection method. As a result, Diffracto did not produce the new DAIS unit.
Even so, the firm proposed and mocked up another version of its device, in 1997. Even though it eliminated various problems (depth of field, perspective distortion, etc.), that version was not produced either.
A few years later, the firm began to work on a hand-held hail damage detector for use on automobiles and, potentially, on composite aircraft. The software package was still undeveloped by the time production of the DAIS devices came to an end, around 2004-05.
If working with an antique aircraft, the aforementioned Type 504, had been something of a challenge, the IAR was eventually faced with a far more difficult problem when it was asked to test an adhesively bonded metal laminate panel which had to endure elevated temperatures without deforming.
Aware that elevated temperatures would boil off the degreasing product they used, IAR technicians had to develop an entirely new approach. They achieved the required surface reflectivity by conforming a thin sheet of aluminum foil on the object. That approach showed such promise that it led to development of a technique known as SolidHi (Solid Film Highlighting) which was patented by IAR in 1999, and this in both Canada and the United States.
The SolidHi process used air pressure or vacuum to force a thin metal or plastic film into close conformity with the surface of an object in need of inspection.
One such object was a Shuttle Remote Manipulator System, or Canadarm, inspected around 2000. Another was the super secret Northrop B-2 Spirit long range stealth bomber of the USAF. You see, mechanics trying to locate and open the aircraft’s access panels were damaging the unmarked stealth coating which covered them.
In 2004, LMI Technologies Incorporated, as Diffracto was called by then, developed an updated version of its DAIS for the Wojska Lotnicze i Obrony Powietrzny / Siły Powietrzne, in other words the Polish air and air defence forces / air force.
The final DAIS inspection conducted by an NRC / IAR team took place in 2006.
You see, in early March of 2005, an Airbus A310 airliner operated by the Canadian carrier Air Transat Incorporée of Montréal, Québec, lost most of its composite rudder in mid-flight. The aircraft landed safely but that accident understandably caused quite a shock.
The investigation concluded that the inspection procedures used by Airbus Société par actions simplifiée could be improved. As part of the investigation, Airbus inspected every aircraft in service at the time using two manual techniques.
One day, in 2005, in Vancouver, British Columbia, an IAR team began to inspect the rudder of an Airbus jetliner operated by Air Transat, using a DAIS unit. The Airbus team working on the aircraft politely told them to leave, as their device was not one of the inspection methods approved by the firm. The IAR team duly left, but only after completing its inspection.
In 2006, an inspection team examining another Airbus airliner discovered a rudder which had deteriorated beyond acceptable limits. This definitely caused concern since the damage could not be seen as per the certification requirements. A D-sight inspection was hurriedly performed in Germany by an IAR team. The device highlighted the damage within minutes. Impressed, the Airbus people present asked where they could buy that technology. They learned that they could not because production of the DAIS had ended.
All in all, Diffracto Limited and the firms which succeeded it made 15 or so DAIS units. Those units could be found in 4 countries (Canada, Poland, United Kingdom and United States).
Yours truly cannot say if any of those devices remained in service in 2024. This being said (typed?), I have a feeling that at least one DAIS might still be in service with the Siły Powietrzne, in other words the Polish air force, a new name adopted in 2004.
Incidentally, Laser Management International Incorporated (LMI) of Vancouver, British Columbia, a newly formed (1998) firm which had acquired 4 small sensor manufacturers based in 3 countries (Sweden, Netherlands and Canada), purchased a large majority of Diffracto’s shares in January 1999. And yes, one of those small sensor manufacturers was Sensor Adaptive Machines Incorporated of Windsor, an entity mentioned in the first part of this article.
Diffracto might, I repeat might, have become LMI Diffracto Limited in 1999, before turning into LMI Automotive Incorporated, perhaps, not too long after that. In 2003, its name changed to LMI Technologies Incorporated.
Augusta Technologies Aktiengesellschaft, a German group owned by TKH Group Naamloze Vennootschap, a telecommunications group based in the Netherlands, acquired LMI Technologies in 2011. As of 2024, that 3D scanning and inspection firm was based in Burnaby, British Columbia.
And so our story ends, my reading friend.
And please remember that an airliner is the safest means of transport you can use in 2024, apart from perhaps an elevator. It is safer than an automobile and even a train. Whether or not your air travel experience would be as enjoyable as a train travel experience is another matter, of course.
Do you think the airlines, airport authorities, security authorities, etc., know what they are doing, huh? If yours truly may be permitted to quote / paraphrase Daryl Van Horne in the 1987 American supernatural dark comedy film The Witches of Eastwick, we all make mistakes. Of course, when we make mistakes, they call it criminal, or evil. When they make mistakes, they call it… nature. So, what do you think? Are they the innocent victims of circumstances or are they doing it to us on purpose? I really want to know.
Ta ta for now.
This writer wishes to thank the people who provided information. Any mistake contained in this article is my fault, not theirs.
Rénald Fortier
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