Differences Between Manual Flight Computers

Discussion in 'Pilot Training' started by Rory, Dec 20, 2017.

  1. Rory

    Rory Pre-takeoff checklist

    Joined:
    Dec 17, 2017
    Messages:
    151
    Display Name:

    Display name:
    Rory
    I've been a bit curious about this and spent some time yesterday tracking down the history.

    At this point, there are two styles of manual computer, the E6B (which has a slide that fits into the main body of the computer) and the CR, which is circular and has no slide.

    Philip Dalton, a pilot with the U.S. Naval Reserve, invented and patented the E6B, and his 1936 patent application can be read via a search on Google Patents. On the marketing side, he worked with Philip Weems, whose name will be familiar to mariners here as one half of Weems and Plath.

    Siegfried Knemeyer, both an active military pilot and head of technical development for aviation for the German Reich, invented the predecessor of the CR for use by the Luftwaffe. In 1955, a pilot named Harold Raymond Lahr, together with his employer, United Airlines, patented a version of Kneyemeyer's computer and assigned the patent to Jeppesen. The Lahr/United Airlines patent can also be read via a search on Google Patents.

    The main difference between the E6B and the CR is that the latter takes a more mathematical, trigonometric approach to solving wind triangles. One result is that the CR is more compact (indeed, this is stressed in the patent application), but perhaps a bit harder to grasp.

    Philip Dalton died when his plane crashed while instructing a new Naval aviator. After the War, the U.S. decided to "invite" Knemeyer, along with von Braun and other prominent German scientists, to become a U.S. citizen. Lahr went on to become the principal spokesman for the argument that TWA Flight 800, which in 1996 crashed off Long Island with major loss of life, was shot down by a missile, and that the U.S. Government, including the NTSB, the CIA and the FBI, have engaged in a massive coverup ever since. Ray Lahr, or people associated with him, continue to maintain a web site in his name dedicated to the cause, most recently updated two years ago.

    The Patents on both styles of flight computer have long since lapsed. The Pooley's CRP computers (dominant in the U.K.) are based on the E6B. There are several companies making copies of the CR. The "new" ASA E6B Circular Flight Computer, released in 2014, is not an E6B at all. It is a copy of the Jeppesen CR. I guess that ASA thought that the name "Circular E6B" would sell better.

    If you look at instruction manuals from 30 years ago, they stress the wind functions and treat the rest as secondary. Newer manuals stress such useful features as converting liters and U.S. gallons to Imperial Gallons. Hey, there are apparently a couple of Caribbean islands that continue to use the latter, and wind computations are a bit harder :)

    Yes, I have too much time on my hands :)
     
    Last edited: Dec 20, 2017
  2. Matthew

    Matthew Touchdown! Greaser!

    Joined:
    Apr 18, 2005
    Messages:
    13,729
    Location:
    kojc, kixd, k34
    Display Name:

    Display name:
    Matthew
    I have one of each.

    I got the CR so I could have something else to play with.
     
    Rory likes this.
  3. Matthew

    Matthew Touchdown! Greaser!

    Joined:
    Apr 18, 2005
    Messages:
    13,729
    Location:
    kojc, kixd, k34
    Display Name:

    Display name:
    Matthew
    It's been a long time since I've messed around with the CR wind side. My recollection is that it's really easy to calculate xwind components. But it's pretty easy to take a quick glance at the xwind chart printed on my kneeboard, too.
     
  4. Rory

    Rory Pre-takeoff checklist

    Joined:
    Dec 17, 2017
    Messages:
    151
    Display Name:

    Display name:
    Rory
    You might find this interesting (A Tale of Two Whiz Wheels): http://www.stefanv.com/aviation/flight_computers.html
     
  5. MauleSkinner

    MauleSkinner En-Route

    Joined:
    Oct 25, 2005
    Messages:
    3,898
    Display Name:

    Display name:
    MauleSkinner
    I carried a CR-5 in my pocket for about 30 years...quite handy. I'd plot all the wind dots while getting my FSS briefing, and grab an average for computing time enroute. Normally within 3 minutes on a 3+ hour flight if ATC didn't fum up the works too much. Pretty handy in the cockpit, and easier for me to work one-handed.
     
  6. BillTIZ

    BillTIZ Final Approach

    Joined:
    Sep 3, 2008
    Messages:
    5,000
    Location:
    0L7, VGT
    Display Name:

    Display name:
    BTIZ
    I’ve carried both, I never really used the wind side of the CR. I needed the Mach compression on the front side.
    Mostly I used the speed dividers and tempered the SAC standard wind based on the season. 270@50 in the flight levels, no wind for low level.

    Low level at 540KGS, the speed dividers are packed away. No time for whiz wheels, it’s mental math, TLAR and rely on the aircraft computers. Keep that INS tight with radar fix point updates, no GPS in the bird until after I retired.
     
  7. HAPPYDAN

    HAPPYDAN Pre-Flight

    Joined:
    Sep 3, 2017
    Messages:
    66
    Display Name:

    Display name:
    HAPPYDAN
    Thanks, Rory, for an interesting and revealing discussion. The Museum of Flight in Seattle might find that an interesting display. If not there, maybe the EAA Museum in Oshkosh. I vaguely remember a manual method, done with paper, pencil, ruler, and a protractor. A Boy Scout leader, and former WWII AAC pilot, taught us a stubby pencil method to find the appropriate magnetic heading. It was the early '60s. I'm officially old.
     
    Rory likes this.
  8. Rory

    Rory Pre-takeoff checklist

    Joined:
    Dec 17, 2017
    Messages:
    151
    Display Name:

    Display name:
    Rory
    Hi Dan,

    Great that you found it interesting.

    There are internet pages, and indeed a couple of YouTube videos, that show how to solve these problems as you were originally taught.

    The patent applications for the navigation computers do a good job of explaining what problems they were intended to solve and how they operated. I doubt that many people have ever seen the applications. Until Google started its Patent Project, they would have been very hard to unearth. Now, all it takes is a simple search:

    Dalton's 1936 Application for what became the E6B: https://patents.google.com/patent/US2097116A/en?q=navigation&inventor=philip+dalton

    Dalton also took out two earlier, related patents, that can also be easily found. Indeed, there are links on the above page.

    Lahr's 1954 Application, which I believe is heavily indebted to Kneyemeyer's computer for German military and civilian aircraft, for what became the CR: https://patents.google.com/patent/US2775404A/en?inventor=harold+lahr

    Note that on the above pages there are links to download .PDF versions. These are very good images of the original applications and supporting drawings. They are easier to read, definitely recommended.
     
    Last edited: Dec 21, 2017
  9. Larry in TN

    Larry in TN Line Up and Wait

    Joined:
    Nov 16, 2013
    Messages:
    926
    Location:
    Nashville, TN
    Display Name:

    Display name:
    Larry in TN
    Once I learned it, I preferred the CR-style computer. Fits in a pocket and it has the corrections for compressability and ram-rise that most E6B computers lack.