At the Empire Test Pilots School (ETPS) in England fifty-three years ago, my training was much broader than I had expected. It even included a deeper knowledge of how to communicate effectively. After all, a test pilot has to describe his experience and present his views to people who can design aeroplanes but know very little about flying. It is almost like explaining colours to a blind person. Thus, I was taught to be correct, clear, concise and convincing, the vital Four Cs. These traits were essential for test flight reports. If I missed something, it was called an oversight. If I had gone to the USA for training, oversight would have meant supervision by instructors to ensure that I was doing my job properly. In American English over means super and sight means vision. Hence oversight equals supervision. As you can see language can help to communicate but confuse just as easily. According to George Bernard Shaw a common language divides the Brits and the Yanks.

I unravelled other mysteries of the English language. The word 'test' came into English from old French where it identified a pot in which metals were heated to ascertain their quality. No wonder some test pilots seem very potty, especially as viewed by designers. By the 16th century, the word test described an examination of properties or qualities. The word pilot has an origin closer to home. In Indo-European, pada was the foot, and also the oar of a boat. The Greeks made it pedotes, meaning rudder or helmsman. Latin converted it to pilotus. That’s where English got it from, but at first pilot referred to steering of ships. By the 18th century, it was applied to guiding hot air balloons. An aircraft driver was called a pilot only from 1907; four years after the Wright Brothers flew the very first aircraft.

After having worked in six aircraft factories in UK, India and Egypt, I took charge of the Aircraft & Armament Testing Unit (A&ATU). With the help of Flight Test and Instrumentation Engineers, we tested aircraft and many systems. A&ATU was upgraded to Aircraft & Systems Testing Establishment (ASTE). The new name recognised the importance of testing of various airborne systems fitted in aircraft. And the addition of training of test crew gave it the title of Establishment, as required in the armed forces terminology. But apart from testing planes, it gets very busy testing systems. If you are wondering what systems are, an explanation follows.

Systems are what go into the famous black boxes. These boxes may be getting painted black to lose heat as quickly as possible. Systems by their very nature tend to be really hot-blooded. If you still want to know how systems in an aircraft work, read on at your own peril. While in charge of ASTE, I first tested an Inertial Navigation System (INS) in 1972 on a Harrier two-seat aircraft visiting us from the UK. The INS is sometime also referred to as an Inertial Guidance System (IGS). It was not an easy system to understand. How could inertia tell you where you were or where you should have been or even where you had to go next? But long live the Internet. It has much useful stuff on it, if you know where to look. After a bit of surfing, I came across a lucid explanation of the INS. If you patiently follow the explanation of the INS system you will surely be the better off for it. This system is used on all military fighters and some trainer aircraft. It is fitted on the LCA and will also fly on the Intermediate Jet Trainer. Almost all civil transport aircraft today have one and the larger aircraft more than one in it.

No one is sure who was the author responsible for the following explanation of the inner workings of an INS. However I feel that this is probably the best, clearly defined, technical description of the magic that resides within the aircraft's black boxes. The article titled, "Inertial Guidance System Simplified" is from the Canadian "Airspace Newsletter", Issue 1/94 printed by Transport Canada. Almost all articles printed in its Newsletters are a collection of letters from pilots. Hence we may safely assume that this one is distilled from the experience of handling the INS and efforts to explain it to others by a number of pilots. Distribution of articles from this source is actively encouraged, as long as reference is made to the Airspace Newsletter. Hence, please do print copies of it and give them to whoever needs to understand how an INS works. I hope this lucid explanation will help you as much as it assisted me to understand the INS. The article says: -     Quote "The aircraft knows where it is at all times. It knows this because it knows where it isn't. By subtracting where it is from where it isn't, or where it isn't from where it is (whichever is the greater), it obtains a difference, or deviation.

The Inertial Guidance System uses deviations to generate error signal commands which instruct the aircraft to move from a position where it is to a position where it isn't, arriving at a position where it wasn't, or now is. Consequently, the position where it is now, is the position where it wasn't; thus, it follows logically that the position where it was is the position where it isn't.

In the event that the position where the aircraft now is, is not the position where it wasn't, the Inertial Guidance System has acquired a variation. Variations are caused by external factors, the discussions of which are beyond the scope of this report.

A variation is the difference between where the aircraft is and where the aircraft wasn't. If the variation is considered to be a factor of significant magnitude, a correction may be applied by the use of the autopilot system. However, use of this correction requires that the aircraft now knows where it was because the variation has modified some of the information which the aircraft has, so it is sure where it isn't.

Nevertheless, the aircraft is sure where it isn't (within reason) and it knows where it was. It now subtracts where it should be from where it isn't, where it ought to be from where it wasn't (or vice versa) and integrates the difference with the product of where it shouldn't be and where it was; thus obtaining the difference between its deviation and its variation, which is a variable constant called error." Unquote.

As test pilots become senior they attend many seminars and sometimes even speak at seminars on flight-testing and how to do it safely. The word seminar comes from semen, and is related to seed. At one seminar the lecturer was startled to see a chap walking to and fro in the rear row. A kind neighbour guided him back to his seat. The Good Samaritan explained to the lecturer that the gentleman had the habit of walking in his sleep. The audience usually sleeps during seminars, sometimes with eyes open. Perhaps going to seed has something to do with it!     At one symposium also on flight-testing, a well-educated test pilot kept asking, right through many lectures and discussions, when it would begin. Finally he was asked to stop interrupting the proceedings. He said that he was keenly waiting for the symposium to begin. When exasperated organisers asked for an explanation, he referred them to a thick dictionary. A symposium from Greek times referred to a get together with friends for drinks. The Greeks usually lubricated their intellectual discussions, or music concerts, with liberal doses of alcohol. Our friend was surely very thirsty. Hopefully, at the next symposium on flight-testing or flight safety, organisers will ensure that it lives up to its name. Perhaps a good Bangalore pub would be the best place for it.