Welcome to the NavList Message Boards.


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

Compose Your Message

Add Images & Files
    Re: Fairchild A-10A in practice
    From: David Pike
    Date: 2017 Jul 6, 08:13 -0700

    Bill Morris you wrote:  The median is preferred over the mean because it is a more robust estimate of central tendency in that it is less sensitive to skewed results and outliers. It also requires no calculation.

    That’s an interesting concept Bill which our mathematicians will argue over for weeks.  However, as automatic ‘pecking’ is deemed preferable to manual ‘pecking’; you’d need an automatic pecker as in the A10-A.  You’d still need to find the 31st mark manually.  Do you know if in pre-digital times anyone ever patented an automatic median indicator?  My initial question was ‘How hard was it to find the 31st mark around the disc in the air in a dimly lit noisy navigator position'?  I’d also be interested to know, because my A10 and A10A are both jammed, how many degrees of sextant altitude correspond to 360 degrees of disc rotation?  

     You also wrote:  Additionally, the period of slow oscillation of many aircraft, called "phugoid oscillations" by Frederick Lanchester, is about 2 minutes, so 60 observations in 2 minutes tended to become the norm.

    It’s interesting that the poor old phugoid, which takes place in the longitudinal plane only, has been rather made the scapegoat for acceleration errors, and it is responsible to some extent for errors in fore and aft (ETA) observations.  However, probably the greatest errors are due to the effect of track changes upon beam (Tracking) observations (see attached notes).  Now whilst these are corrected for, they don’t get the same mention in popular culture, probably because the reasons are harder to quantify.  Also, the period of Dutch Roll, which takes place in the lateral and directional planes, is usually less than the phugoid, so if you span the phugoid, you probably span two or three Dutch Rolls.  However, the motion is by no means connected with Dutch Roll only and during trials it was found that for beam observations too, a two minute observation was about right. DaveP


    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    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 Settings

    Posting Code:

    Custom Index

    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