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    Re: Most Probable Position (MPP)
    From: Howard G
    Date: 2022 May 14, 19:04 -0700

    Hi Ed

    MPP came up in the Amelia Earhart conversation and is typically (if not the origin of the idea) from military air navigation concepts. I have on my book shelf The Royal Air Force AP1234A - Ministry of Defence Jul 67 - Air Navigation Vol 1 - Theory and Practice of Air Navigation - section 1 Chap 6 - MPP .... and I will not quote but as David quite rightly says - it is a statistical discussion (in the book) of working out the most likely position the aircraft is from the information you have at hand - and is essentially a lot of plotting and a lot of guesstimating - for an abintio navigator - mostly theoretical and by the book but for an experienced on aircraft type line navigator - a lot of experience of the navigation accuracy of the systems in that aircraft, the dR plotting and inertial nav posn and or simple DR plot against any type of fixing done - Loran/Astro/ADF/TACAN/etc etc

    As David said - the aircraft is travelling forward quickly - by the time you 'decide' where you 'probably' are it is old information - and if you are below safety height in the dark - you are behind the 8 ball!!!! - a dangerous position.

    If you are transitting on a long airways trip - and at 30000 no big deal you can play around with things.

    Whilst not wanting to regenrate the Amelia Earhart story - or Fred's navigational errors to his final destination - or attempt to - I just do not think he applied the concept of MPP to the concept we learnt in the military and he was most likely well north of his position and low on fuel - and that is just the worst scenrio you can be in whilst flying.

    Back to MPP - in essence (whilst my memory is old - 1980) - the working out of the MPP as part of your regular plotting cycle just became an exercise in experience and knowledge (if you lacked good fixing information) - and whilst this forum talks about astro accuracy - a good cocked hat of 10 nms on a stable P3B Orion at 30000 ft was a reasonalbe norm - but you had time and room to do this - operating at lower altitudes in a 10 hr holding pattern in the North Pacific operation zone over a Ruskie Boomer area at night - with every nav aid off - except astro was a different story especially when you are laying a huge sonobuoy pattern and you need to plot each sonobuoy in a pattern that maybe a 1000 nms long.

    So the concept of MPP, though in theory is statistically based in reality - it was a measured guestimate based on a lot of experience on type.

    Howard G

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