A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Hanno Ix
Date: 2014 Nov 22, 19:30 -0800
To the average yachtsman, MOB! Is the emergency cry “Man over board!”. Something totally different in aviation navigation I think! Loved your article on the Madeira flight. Must get me a Polhemus. These graphic, slide rule type solutions seem to be intuitively good for spherical trig for non mathematicians, hence my interest in the Brown-Nassau. As a semi retired medic , I’m ok with statistics, but not so good with trig equations. Logs via a slide rule like the Bygrave also seem right to me as well.
I have the Chichester books, but thanks for the pages from Hughes and Wright. Also your MOB article, brilliant. The Polhemus computer looks interesting.
Chichester used his Bygrave for the basic calculations. What he developed was a version of the "Motion of the Body" correction table used by more modern flight navigators. See my explanation of the MOB correction method:
I scanned in Chichester's book about the Tasman sea crossing, I have emailed it to several members of the list. If you want a copy send me your email address.
From: Francis Upchurch <NoReply_Upchurch@fer3.com>
Sent: Friday, November 21, 2014 10:21 PM
Subject: [NavList] Re: Early methods of air navigation
Fascinating stuff. I think Brown used a standard sextant with spirit level attachment to give AH/bubble?
Don’t think he had the Booth bubble in 1919, did he? But he did have the “Baker navigation machine” which looks interesting, rolling continuous chart with pre-computed Altitudes?
Curious that for his 1931 Tasman sea flight, Chichester had tried the Booth bubble sextant, found his navigation 700 miles out and reverted to a standard sextant and natural horizon altitudes. He claims to have invented his own “pre-computed sun Alts” system. Would he have been aware of the already invented Baker machine?
Any views Gary?
This should answer your question, see attached.
From: Fred Hebard <NoReply_Hebard@fer3.com>
Sent: Friday, November 21, 2014 9:21 AM
Subject: [NavList] Early methods of air navigation
The discussion of the Brown-Nassau CN Plotter brought to mind the following question. What methods did the early pioneers of trans-Atlantic flight use for navigation, such as Alcock and Brown? Brown was the navigator on that flight. They made landfall near their intended destination. Running down a line of latitude would be a clear choice, but how measure the latitude? They flew at low elevations, so
perhaps using the actual horizon? Dip scales as the
square root of elevation. The error for being 50 feet off in elevation is less than two minutes of arc at 200 feet. In contrast, Admiral Coutinho installed levels on his Plath in 1919. Had the British? Then there is RDF, which was available in the U.S. by the Point Honda disaster.
Those are some guesses. What does the documentary evidence say?