2
Photo Info

Testing Time

By Vertical Mag | April 30, 2013

Estimated reading time 9 minutes, 52 seconds.

There was a time when test pilots were defined by a black and white British comedy, where the dashing test pilot, with girls on each arm, casually said to the assembled masses after the first flight in the sexy looking airplane, “Tell the designer chappie he did a good job.” Things have changed quite a bit since then.
The first thing to make clear is that in the helicopter world the term ‘test pilot’ is often misunderstood, thanks largely to the U.S. Army’s maintenance pilot course. Graduates of this course are confusingly called test pilots, when a more correct title might be Post Maintenance Check Pilots (that’s what the U.S. Navy calls them). This definition is guaranteed to generate a ton of letters — but, to be perfectly correct, a test pilot is one who is involved in research and development, experimental flying, or doing things that haven’t been done before. I don’t want to sound elitist, but words do have meaning.
So why do we need test pilots? Where do we find them? And what sort of background and training do they get?
Let’s imagine for a moment that a brand new helicopter has just been trucked into your hangar. It’s never been ground run before, let alone flown. Who is going to fly it? Where do they start?
I was involved many, many years ago with a company with more ambition than technical talent. They’d produced a helicopter… sort of. It used a car engine, and the designer, while well intentioned, had absolutely no design experience in aviation matters, let alone something as complex as helicopter rotor heads. Many aspects of the construction were admirable, but some were less than salubrious, and I was there to act as a technical consultant. The team asked if I’d like to see a video of the first flight. Before they ran the video, I asked who had done the flying, and was told that it was a local commercial pilot with lots of hours, but no flight testing background. Reluctantly, I watched in quiet horror for the brief 10 seconds or so that the machine “flew.” It was certainly not under control, and there was no buildup visible. The aircraft was started up, and the pilot immediately tried to fly. I think the machine reached something like 40 degrees nose up and down, and 30 degrees of bank in those brief, heart-stopping seconds. Only the over-designed composite fuselage saved the day as it slammed heavily to earth.
Needless to say, the project no longer exists. 
Another project with which I was briefly involved aimed to hover and cruise at near 400 knots. It was a neat idea, but it had some serious shortcomings in the landing gear (think of a flying saucer with struts and pads, and no wheels) and the advanced flight control system was driven by a joystick that appeared to owe more to computer games than good ergonomics. My suggestion of making a large scale model was rejected immediately, as well as the suggestion that we would need to spend quite a bit of time getting the physical aspects of flight control and control laws sorted out in a simulator. This project also fizzled out shortly afterwards.
Finding a Test Pilot
So, who do you want to have as a test pilot? Not someone who dreams of doing the impossible, or someone who takes lots of risks. In fact, properly conducted, flight testing should be boring — there should be no surprises. If you’re surprised, the flight has been planned or executed improperly.
Do you need to be an engineer? Not necessarily, but a good technical background and a high curiosity level are very helpful.
Most, but not all, test pilots are graduates of test pilot schools — an expensive course in learning the various test techniques and theory behind the way helicopters actually fly, and the closest thing to a post-graduate course in piloting that exists. Those who don’t have the opportunity to attend such a course typically undergo a lengthy in-house, on-the-job training program with their employer. No-one leaps fully grown into the flight test business without some careful vetting — at least no-one who lasts a long time.
It takes a lot of time, money and effort to get a helicopter design right, and even more time to check out all the things necessary for the flying public (pilots and passengers) to operate it safely.
Remember in the beginning that there are no checklists, no flight manuals, no written limitations. Someone has to develop all of these. All we have to go on is the assistance of the design team of engineers, and a set of requirements in the Federal Aviation Regulations (FAR). If it’s a small helicopter, it will be covered by FAR 27. Fortunately, someone has written a book to decipher the relatively tersely-worded regulation, and it’s called Advisory Circular 27-1B. I would not recommend it for bed-time reading. (The plot is so-so, and the character development not much better…)
In actual fact, the test pilot’s involvement starts a long time before the first flight. He or she will be assisting the design team in a large number of decisions about instruments and cockpit layout, and to make good decisions in this area, a lot of experience of a wide variety of machines is needed. There being no perfect flying machine, it’s useful to learn from the good and bad points of other designs, so some broad experience is a good thing.
Let’s start with looking at some basics. Can you get in and out of the machine easily? What about when dressed in cold weather clothing? If not, why not? Does it meet the requirements for door opening and closing? In high winds, too? How about the field of view? Does it have the necessary instruments with the appropriate markings?
This is all before any metal is cut or composite material laid out. Another concurrent activity before anything takes to the air is the planning of tests, and the assessment of risks and potential problems.
Once the actual testing begins, one of the sterling requirements becomes clear — an ability to observe and report is essential. Certainly there will be lots of instrumentation looking at stresses and strains and the like, but an ability to keenly see what the machine did in response to control inputs, and when and where those responses happen, has often been the difference between the success and failure of a program. It’s also worth noting that sometimes the response to not moving the controls is equally as important.
As helicopters have become increasingly complex, test pilots have had to develop what can best be described as a pathological interest in failures — what happens when this sensor, or that computer fails? How will that affect the rest of the helicopter’s operation? 
The flight tests themselves often have an element of risk, so the test pilot has to know what his personal criteria are for going no further in a test. Tests like the H-V curve have a great deal of qualitative criteria, as well as engineering limits, and the test pilot has to balance risk with safety for the end users of the equipment. The ability to justify why an end point was defined as an end point may require years of experience.
Next issue – what sort of tests are needed?
Shawn Coyle is currently director of academics for Marinvent Corp. and is a Transport Canada DAR flight analyst for helicopters. He has taught flight testing for over 10 years at three major test pilot schools, and certified entry-level simulators in Europe. With over 6,100 flight hours, including time in more than 30 different types of helicopters, he felt he had to write! The author of Cyclic and Collective and The Little Book of Autorotations (available through eagleeyesolutionsllc.com or Amazon.com), he also is involved as an expert witness on helicopters and regularly lectures at seminars and classes related to helicopters and aircraft certification.

Leave a comment

Your email address will not be published. Required fields are marked *

HAI Heli-Expo 2024 Recap

Notice a spelling mistake or typo?

Click on the button below to send an email to our team and we will get to it as soon as possible.

Report an error or typo

Have a story idea you would like to suggest?

Click on the button below to send an email to our team and we will get to it as soon as possible.

Suggest a story