Welcome to the NavList Message Boards.

NavList:

A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Message:αβγ
Message:abc
Add Images & Files
    or...
       
    Reply
    Re: aircraft drift; over wate.r Re: Amelia Earhart's aerial navigation
    From: Clive Sutherland
    Date: 2009 Nov 19, 22:39 -0000

    George;
    In my experience although it is a long time ago now there are two methods
    that can be used. The first is as you say. If the wind is strong enough, the
    drift meter can be aligned to match the direction of movement of the wave
    tops while the pilot  keeps a constant heading. The scale of the drift
    graticule is calibrated w.r.t. the axis of the aircraft  The drift angle can
    be  found to an accuracy of  about 1 or 2 degrees. White horses have a
    lifetime of about 10 to 30 secs and if the altitude is about 1000 ft enough
    of them will be seen in the field of view to do this quite easily and
    several observations can be averaged.
    
    The second is for the pilot to fly a pre-defined triangular course with
    careful rated 120deg turns and with equal legs (about a mile long.) If there
    were no wind the aircraft would return over its start position.
    The exercise would start with the navigator dropping a Smoke float at the
    start of the run and the run timed to the finish when the aircraft crosses
    the smoke trail again after two 120 deg turns. The difference between the
    start and finish positions would be the drift during the time of the run.
    The direction was found by flying downwind or upwind, in the direction of
    the smoke trail.
    ** -----Original Message-----
    ** From: George Huxtable [mailto:george{at}hux.me.uk]
    ** Sent: 19 November 2009 19:36
    ** To: navlist@fer3.com
    ** Subject: aircraft drift; over wate.r Re: [NavList 10758] Re: Amelia
    ** Earhart's aerial navigation
    **
    **
    ** As one quite ignorant about air navigation, a few questions come to my
    ** mind.
    **
    ** I can see the relevance of some sort of drift angle meter when flying
    ** over
    ** land, in establishing ground track direction from  relative motion of
    ** landmarks seen passing below.
    **
    ** But how does that work over the sea? Presumably, one would be seeing
    ** whitecaps on the waves, or white-horses, that will tend to drift
    ** downwind,
    ** as the wave-tops move downwind. Is that speed of motion quite negligible,
    ** compared with the airspeed of a light aircraft? Is there some way of
    ** allowing for that motion? Or does this just add an additional uncertainty
    ** to
    ** the estimated track-angle of the aircraft? If so, what level of
    ** uncertainty
    ** would that be?
    **
    ** George.
    **
    ** contact George Huxtable, at  george{at}hux.me.uk
    ** or at +44 1865 820222 (from UK, 01865 820222)
    ** or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    **
    ** --
    ** NavList message boards: www.fer3.com/arc
    ** Or post by email to: NavList@fer3.com
    ** To unsubscribe, email NavList+unsubscribe@fer3.com
    **
    ** No virus found in this incoming message.
    ** Checked by AVG - www.avg.com
    ** Version: 8.5.425 / Virus Database: 270.14.73/2512 - Release Date:
    ** 11/18/09 19:41:00
    
    
    
    --
    NavList message boards: www.fer3.com/arc
    Or post by email to: NavList@fer3.com
    To unsubscribe, email NavList+unsubscribe@fer3.com
    

       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Join NavList

    Name:
    (please, no nicknames or handles)
    Email:
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.
    Email:

    Email Settings

    Posting Code:

    Custom Index

    Subject:
    Author:
    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site