I was privileged to know and on occasion work with Darrol over about 15 years. As a much younger engineer with a lot of responsibility quite young, he was good enough on a number of occasions to bluntly - but very helpfully - share his vast experience with me when he felt I was talking cobblers. With practice I learned that the best way to tap into his experience, was to start an argument in his hearing about something, and he felt the need to put us all right.
He was an absolute one-off, and a fantastic mentor for a young aeronautical engineer to have had - I was fantastically lucky.
I can recall one particular occasion - I was giving a paper on light aircraft design at a Royal Aeronautical Society conference where he was sat in the front row taking apparently copious notes. This surprised but very much flattered me. A few hours later I was sat in the audience behind him - and he was still scribbling away. Peering over his shoulder, I realised he was ignoring the lecture completely but was busy writing his next book. My ego was restored to an appropriately small size!
I was privileged to sit with him on the judging for several rounds of the RAeS light aircraft design competition. His knowledge was encyclopedic, and his inputs always consise and meaningful.
I did ask him once how many types he'd flown, he said he had no idea because he'd stopped bothering to count at 150.
I absolutely agree - his books, at first sight really quite simplistic cover a massive amount of breadth at just the right and useable levels of complexity. The material is incredibly useful, and remains in my mind better than most of the newer textbooks. His flight testing book is certainly better than anything else readily available.
A truly great aeronautical engineer and test pilot, and I will certainly be at his funeral service.
G