Part of the second year Ghost Project that just took place at ITPS, some simulator surgery was performed in order to assess a force sensing vs. a deflection side stick for a low gain air-to-air task. Study included 4 test pilot students and 2 engineers and had some interesting results.
Beside the LOES and Bandwidth MIL-STD-1797 criteria, this time we introduced the Neal-Smith closed loop criterion which is based in human/pilot modelling. Not as straightforward in its application as the other ones, it has its own strengths especially in assessing a A/C+FCS configuration for various pilot gains/bandwidth frequencies. Towards that direction, the Nichols chart is a vastly useful tool. Cool exercise!
I am not new to the paper submission process, but up to now I was always participating as an author submitting the paper. This time I was selected as a reviewer and despite the limited time available, I could not refuse the option. After all, you always have to give something back…
The Variable Stability Learjet flights are a significant part of any flight test training course. If you haven’t had them, you are probably missing a significant part of the standard flight test training. Unfortunately they were not part of my initial course, but eventually I had the chance to get them as an Instructor. Great experience flying with a company and an aircraft that have a long history and huge contributions in today’s aviation.
Weather forecast is not always accurate and that one fall short almost 1 hr and a half. Just 4nm before my destination airfield a white watery curtain decided to give me a hard time. Flying into a fast moving storm was not a pleasure or safe experience, but was a memorable one. With the turbulence generating sudden bank angle excursions of 10-20 deg, landing was not an option. Luckily my little 172 could speed up enough to escape the mighty front and land on a nearby alternate. After an hour the main part of the storm had passed us and there was a short window to fly back to original destination, which was done through a low level and speedy manner. Some good lessons learnt there…
The Cooper Harper Rating (CHR) scale is definitely a universal Handling Qualities reference and the most important scale used in Flight Test. It is probably one of the strongest binding links connecting the 1960’s era of flight testers to those of today.
Developed in 1969 it has since been widely used and studied all around the world. Numerous research projects have been done on the scale’s use and other studies trying to propose modifications or replacements. It has been so widely used and recognized, that even if it has some flaws, it will always be the scale to use for Handling Qualities. Proper use and especially pilot understanding of its use can minimize issues like intrapilot or interpilot variability and errors and make the scale an effective engineering tool.
For those of the flying qualities or flight test engineers and pilots who have extensively studied it and used it in research, the CHR is like a living organism. You always have to respect it, not rush it and acknowledge its weak points. Then using it just becomes a pleasure.
Completing this month 3 years of extensive use and study of the scale, I went back to revise the first Greek version I had created. Surprisingly (or not), I did a significant number of changes to it considering my better understanding of the scale and the language. Will it ever be used? Probably not, because then the whole report will have to be translated to explain the wording used – as for other languages. This translation is mostly for archival purposes and a tribute to Cooper and Harper for their contributions to flight test.
After being involved in long term discussions on a new Variable Stability/In-Flight Simulator aircraft, I was tasked to produce the top-level specification write-up. The final document describes the required technical specifications for a fighter-type VSS from degrees of freedom to safety system, modes of operation and desired performance criteria. The spec document is going to serve as guideline for a feasibility and cost study.
The F-16 VISTA shown in the image above has been by far the most impressive In-Flight simulator ever built. However, the problems it has been experiencing have been multiplied and it is scheduled to get retired in few years, currently with no planned replacement.
Projects like this are fun, as long as you have an appreciation of what it takes to complete them and you are willing to make the effort, pay the cost and take the risk they require.