NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Celestial up in the air
From: Hewitt Schlereth
Date: 2008 Jul 28, 23:09 -0400
From: Hewitt Schlereth
Date: 2008 Jul 28, 23:09 -0400
Thanks for the tip, Gary. I'll go to the link. HewS On 7/28/08, glapook@pacbell.netwrote: > > You can get a copy of the Air Almanac, it is easier to use in flight > than the > Nautical Almanac, you get it on disk from the Naval Observatory, cost > thirty one bucks, here is the link: > > http://aa.usno.navy.mil/publications/docs/ord_info.php > > Just print out the pages you need for your flight, about 7 pages of > interpolation and correction tables (which don't change and only need > to > be printed out one time) and two daily pages for each day of your > trip. > > gl > > > On Jul 28, 5:30 pm, "Hewitt Schlereth" wrote: > > Hey, thanks for the thoroughgoing response. One reason for my interest > > was that I began to do celestial when I was living in Allentown PA in > > 1965 and got to talking with a neighbor. He turned out to be a > > navigator for JAL. He gave me an expired Air Nautical Almanac - these > > were the days when it was published in three installments; red > > binding, white binding, blue binding, one every four months. > > > > Anyway, I dug out my high school spherical trig book, bought a surplus > > aircraft sextant and started taking sights from the roof, coached and > > critiqued by my neighbor when he was home between trips. > > > > I took celestial to sea when I moved to the east coast in 1969 and > > it's been with me ever since. > > > > Thanks again, Hewitt > > > > > On 7/28/08, glap...@pacbell.net wrote: > > > > > > > > > > Airlines no longer use flight navigators, they have been replaced by > > > specialized navigation equipment. In the past > > > Kollsman periscopic sextants were used which extended through the top > > > of the > > > fuselage in B-52s, C-130s, other military planes and also in Boeing > > > 707s, and DC-8s. Airline Flight Navigators used celestial for oceanic > > > flight up until the early '70s and the military used celestial > > > routinely > > > through the '90s ( they figured the Soviets would turn off their > > > radio > > > navigational aids in the event of war.) It is still in the current Air > > > Force navigation manual, AFPAM 11-216. Flight navigators were > > > replaced when the Boeing 747 came along with inertal navigation > > > systems in the late '60s. And now GPS provides the specialized > > > navigation equipment that allows tranoceanic operations without a > > > navigator. > > > > > Federal Aviation Regulation (FAR) 121.389 still requires a flight > > > navigator unless the pilot can fix his position every hour and pilots > > > can now do that with INS or GPS. I have attached the regulation and a > > > link to its source. > > > > > gl > > > Title 14: Aeronautics and Space > > > PART 121�OPERATING REQUIREMENTS: DOMESTIC, FLAG, AND SUPPLEMENTAL > > > OPERATIONS > > > Subpart M�Airman and Crewmember Requirements > > > > > Browse Previous | Browse Next > > > � 121.389 Flight navigator and specialized navigation equipment. > > > > > (a) No certificate holder may operate an airplane outside the 48 > > > contiguous States and the District of Columbia, when its position > > > cannot be reliably fixed for a period of more than 1 hour, without� > > > > > (1) A flight crewmember who holds a current flight navigator > > > certificate; or > > > > > (2) Specialized means of navigation approved in accordance with > > > �121.355 which enables a reliable determination to be made of the > > > position of the airplane by each pilot seated at his duty station. > > > > > (b) Notwithstanding paragraph (a) of this section, the Administrator > > > may also require a flight navigator or special navigation equipment, > > > or both, when specialized means of navigation are necessary for 1 hour > > > or less. In making this determination, the Administrator considers� > > > > > (1) The speed of the airplane; > > > > > (2) Normal weather conditions en route; > > > > > (3) Extent of air traffic control; > > > > > (4) Traffic congestion; > > > > > (5) Area of navigational radio coverage at destination; > > > > > (6) Fuel requirements; > > > > > (7) Fuel available for return to point of departure or alternates; > > > > > (8) Predication of flight upon operation beyond the point of no > > > return; and > > > > > (9) Any other factors he determines are relevant in the interest of > > > safety. > > > > > (c) Operations where a flight navigator or special navigation > > > equipment, or both, are required are specified in the operations > > > specifications of the air carrier or commercial operator. > > > > > [Doc. No. 10204, 37 FR 6464, Mar. 30, 1972, as amended by Amdt. 121� > > > 178, 47 FR 13316, Mar. 29, 1982] > > > > > Link to regulation: > > > > > > http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=f4449a9057da... > > > > > > On Jul 28, 7:53 am, "Hewitt Schlereth" wrote: > > > > Hi Gary - > > > > > > I'd probably missed the answer to this question because I picked up > > > > the thread in the middle: Is celestial part of your routine duty of > > > > navigating an airliner or is it something you do for its own sake? > > > > > > Thanx, Hewitt > > > > > > PS It's been an absorbing thread to follow. Keep it coming. HewS > > > > > > On 7/28/08, glap...@pacbell.net wrote: > > > > > > > For example, using the page from the Air > > > > > Almanac found on page 206, a day when the H.P is 60', and an altitude > > > > > of 36� we find the parallax in altitude correction to be 48' and this > > > > > > > would be the correction to use with a bubble sextant. (Page 206 of > > > > > AFPAM 11-216.) > > > > > > > Additionally, formulas for these correction are found on pages 393 and > > > > > 394 of the same manual. > > > > > > > gl > > > > > > > On Jul 28, 5:24 am, glap...@pacbell.net wrote: > > > > > > One more thing to discuss before giving an example of in flight celnav > > > > > > is corrections to sights taken in flight. We discussed this back on > > > > > > December 14, 2007 in the thread "additional corrections... (just > > > > > > search "additional corrections") which include an excerpt from AFPAM > > > > > > 11-216. You should download the entire manual here:http://www.e-publishing.af.mil/shared/media/epubs/AFPAM11-216.pdf > > > > > > > > Review chapters 10 through 13. > > > > > > > > I want to add to the manual on this. > > > > > > > > Coriolis can be handled in a number of ways. You can move the A.P. to > > > > > > the right (northern hemisphere) 90� to the course (track) prior to > > > > > > plotting the LOPs by the amount of coriolis correction shown in the > > > > > > table in the Air Almanac and in H.O. 249 (previously posted). Or you > > > > > > can move the final fix the same way. Or, the most complicated way, is > > > > > > to make a correction to each Hc by multiplying the coriolis correction > > > > > > by the sine of the relative Zn, the Polhemus makes this relatively > > > > > > painless. > > > > > > > > Rhumb line correction is avoided by steering by directional gyro > > > > > > during the two minute shooting period and this is what is normally > > > > > > done anyway. > > > > > > > > Wander correction is small at low airspeeds and it can be avoided by > > > > > > making sure the heading is the same at the end of the shot as it was > > > > > > at the beginning of the shot. It doesn't matter how the heading > > > > > > changes during the shot (within reason) as the errors will average > > > > > > out. > > > > > > > > Ground speed correction can also be avoided by making sure the > > > > > > airspeed is the same at the end as at the beginning, any changes in > > > > > > between will also average out. > > > > > > > > Auto pilots do a good job of maintaining airspeed and heading for the > > > > > > two minute shooting period so eliminating the need for the above > > > > > > corrections. > > > > > > > > The AFPAM states you must figure the refraction correction based on > > > > > > the actual Hs as opposed to using the refraction correction based upon > > > > > > the Hc but this is a needless refinement and keeps you from completing > > > > > > the pre computation prior to the shot. Look at the refraction table in > > > > > > H.O. 249 (previously posted) and you will see for altitudes exceeding > > > > > > 10� that the brackets are at least two degrees wide. So only in the > > > > > > rare cases where the altitude is almost exactly at the break point > > > > > > could you come up with a different refraction correction using Hc > > > > > > rather than Hs and even then it could only be a difference of one > > > > > > minute of altitude. For example the break point between a 5' > > > > > > correction and a 4' refraction correction is 12� so if Hs were 11� 50' > > > > > > and Hc were 12� 15' then using Hc would get you a 4' correction and > > > > > > using Hs would get you a 5' correction. This is actually only 1/2 of a > > > > > > minute error because the corrections are rounded to the nearest full > > > > > > minute. > > > > > > > > The parallax in altitude correction for the moon is printed on each > > > > > > page of the Air Almanac based upon the horizontal parallax (H.P.) for > > > > > > the moon on that particular day. This parallax varies with the > > > > > > distance to the moon and moves in lock step with the S.D. since they > > > > > > are both related to the distance to the moon. The H.P varies from 54' > > > > > > to 61' during the year. For example, using the page from the Air > > > > > > Almanac found on page 206, a day when the H.P is 60', and an altitude > > > > > > of 36� we find the parallax in altitude correction to be 48' and this > > > > > > would be the correction to use with a bubble sextant. If using a > > > > > > marine sextant and shooting the lower limb we would add the S.D. of > > > > > > 16' to produce a total correction (but not including refraction yet) > > > > > > of 64'. Subtract the refraction correction of 1' gives the total > > > > > > correction of 63'. Using the correction table in the Nautical almanac > > > > > > for the identical parameters you get 63.5'. The Nautical Almanac moon > > > > > > correction table includes a procedure for using it with a bubble > > > > > > sextant and what this does is just backs out the S.D. correction which > > > > > > is included in the correction table and not needed for a bubble > > > > > > observation. Using this procedure produces a correction for a bubble > > > > > > observation of 47.2' which compares with the 48' from the Air Almanac. > > > > > > > > Remember to reverse the signs of these corrections and apply them to > > > > > > Hc to produce Hp (pre computed altitude) which you then compare > > > > > > directly with Hs to compute intercept. > > > > > > > > gl > > > > > ... > > > > read more � > > > --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---