Franek, well known and liked member here, is a researcher of Polish aviation with a number of articles and two books published, as far as I know.
His first book, published in 2017 is an analysis of the July 1943 aircraft crash at Gibraltar that took the life of 16 of the 17 passengers and crew aboard, including Gen Sikorksi (Prime Minister of the Polish Government in Exile and Officer Commanding the Polish Army), his daughter, and several other senior Polish personnel and UK MPs.
Franciszek Grabowski Liberator AL523 - Analiza Techniczka Katastrofy Gibraltaskiej (Instytut Pamlieci Narodowej, Warsaw 2017)
Franek's own FB note (translated from Polish, so e&oe, Sir...
"It has been 80 years since the investigation into the most important air disaster in Polish history began. A catastrophe with dramatic consequences for the Polish state and nation. So far, the causes of the disaster have not been formally clarified. It can be done, as evidenced by my publication published 5 years ago with a hook, but nobody is interested in it. Why? Whether it is ignorance or perhaps fear of precedent, I cannot decide."
More than one book has been published on this disaster in the years since, at least two of them in English.
It is unfortunate that Franek's own 2017 Polish work, apparently the latest of these, is not readily found in the usual book listing sites like bookfinder.com.
It's a shame it doesn't rate a mention in the Bibliography and Further Reading sections of the Wikipedia page: https://en.wikipedia.org/wiki/1943_G...or_AL523_crash
though Franek himself might like to update at least the Further Reading section there.
The publisher, Instytut Pamlieci Narodowej (Institute of National Remembrance) fortunately kindly provides an English edn of it's Books pages.
Unfortunately, Franek's Liberator AL523 is not listed there at present.