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    Re: Sextant mount in B-36
    From: Robert Eno
    Date: 2013 Jul 06, 20:53 -0400
    Very interesting information. Thanks Gary.
    Add me to the list of B-36 afficionados. I was first introduced to this remarkable aircraft through the movie "Strategic Air Command" which remains my all-time favourite movie. I think James Stewart was actually the co-star. The real star was the B-36.
    Over the years, I have collected quite a few books on this aircraft. Someday, I would love to make a pilgrimage to the US to see one of them. Alas, by the time I was born, they were being phased out. Never saw one fly.

    ----- Original Message -----
    From: Mike Burkes <m_burkes@msn.com>
    Date: Saturday, July 6, 2013 1:34 pm
    Subject: [NavList] Re: Sextant mount in B-36
    To: enoid@northwestel.net

    Hi PH, wow, thanks so much for the great info on such a great plane.
    Mike Burkes

    From: cfuhb-acdgw{at}earthlink.net
    To: m_burkes{at}msn.com
    Date: Fri, 5 Jul 2013 21:55:21 -0700
    Subject: [NavList] Re: Sextant mount in B-36

    Gary LaPook wrote:  > Interesting panoramic of a B-36 cockpit. Scan upwards to see the Kollsman periscopic sextant mount.  >  > http://www.nmusafvirtualtour.com/media/062/B-36J%20Engineer.html    Initially the B-36 had six sighting domes for the gunsights that  remotely controlled the turrets. There was a astrodome, too. By the end  of its career, the "Featherweight" modification had deleted all guns  except two in the tail. The six unneeded gunner stations and the  astrodome were replaced by flat hatches. I think all were removable for  emergency egress on the ground or in flight.    The last B-36s were delivered as Featherweights from the factory. I have  read the final configuration even deleted thermal insulation on the crew  compartments in an effort to attain the highest possible altitude.  Portable plug-in electric heaters were provided to augment the  pressurization and heating system. Nevertheless, a long flight at high  altitude was not comfortable. One pilot wrote that all the hot air was  needed to keep the windshield clear. The rest of the greenhouse canopy  would be opaque with frost. When the plane descended the water would  drip on everyone.    When clear the canopy gave good visibility, like sitting in a bay window  and flying an apartment house according a former B-36 pilot. Still, the  cockpit crew could see little of the powerplants and landing gear. They  relied on reports from the gunners. This function was so critical, a  special interphone circuit connected the pilots, engineers, and two  scanner stations in the aft compartment. It had a separate emergency  power supply.    As far as I know, the B-36 was the first aircraft to generate electicity  at 120 V 400 Hz with 3-phase alternators connected in parallel, as is  still standard on large aircraft. This requires the alternators to be  phase locked, and thus driven by very precise and reliable constant  speed drives.    In those pioneering days "reliable" was often in short supply. To quote  the flight manual, total AC failure was "an extreme emergency," since  the B-36 was heavily electrified. Only the landing gear, brakes,  nosewheel steering, and bomb bay doors were hydraulically operated - but  AC motors drove the pumps! The reciprocating engine propeller, mixture,  cooling air, and turbo controls were electric. So were the jet (but not  reciprocating) throttles.    Bombing and navigation were "electronified" to an unprecedented degree  in the Sperry "K system". With the help of 360 vacuum tubes it displayed  real time dead reckoning latitude and longitude computed via connections  to pitot static tranducers and the heading system. It was tied to the  radar too, so the crosshairs would automatically track the target. If  they drifted off, the radar observer could select a mode which  automatically updated the winds when he drove the crosshairs back on  target. No more driftmeters and hand computations. Present position  could also be updated directly from the radar.    A three-man navigation crew occupied the nose compartment. The navigator  sat on the left, forward by the windows, though his table and the loran  partly blocked the view. Aft on the right was the radar observer, who I  think was the senior navigator. Then there was the observer, who  assisted both men and operated the nose turret sight at the right  forward end of the compartment.    When I arrived in Strategic Air Command in 1980 as a new B-52 bombing  navigation system maintainer, the B-36 guys were long gone, but the  group mind retained some of the memories. I was told there used to be a  seat and pedals atop the radar antenna in case the azimuth drive failed.  It may have been possible, as the antenna protruded below the belly.  However, I've never seen anything to confirm that legend. At altitude  the "cyclist" would have needed an oxygen mask in the unpressurized  compartment.    The system on the B-52G and H models I worked on was made by IBM, not  Sperry. But the principles were similar. So was the tube count. There  were hundreds but we never saw them. They were in hermetically sealed  modules which were repaired at the depot. The exceptions were the  magnetron (radar transmitter), klystron (radar receiver local  oscillator), and thyratron (radar modulator). Most people wouldn't even  recognize the first two as tubes.    I was lucky to get into SAC in the final years of the vacuum tube era.  Some day I may write a little more on the old ASB-9A system. Did you  know the navigator had a pair of pedals to...    Speaking of Strategic Air Command, in the movie of that name (Paramount,  1955) a navigator (played by Alex Nicol) is one of the main characters.  The man is skillful but bitter because he was involuntarily recalled to  active duty. Jimmy Stewart's character is in the same situation but  handles it with more maturity. Eventually he's able to turn the nav's  attitude around, and together they transition from the B-36 to the new  B-47. The nav stations in both airplanes are shown.    Paramount paid unusual attention to technical accuracy. The preflight  checklist calls and responses are verbatim from the B-36 flight manual,  and the eyes and hands of the actors go to the right places in the  cockpit. When the flight engineer (Harry Morgan) advances the throttles  to set takeoff power, you can see the needles on his panel respond.    The movie shows them starting jets after taking the runway. That too is  correct. The reciprocating engines required two run-ups: an elaborate  one at least 24 hours before flight to allow time for maintenance to  clear discrepancies, and an abbreviated run-up after starting engines  for flight. But you didn't even start jets until on the runway, an  indication of the superior reliability of the turbine even in the early  jet age.    One discrepancy is that the nav team rides in the nose compartment  during takeoff. They're supposed to be aft in the radio compartment for  safety, according to my flight manual. However, the production predated  the manual, so maybe the procedure had changed.    Both takeoffs in the movie are remarkable. When Stewart takes his first  B-36 flight, the camera stays in formation at the 8 o'clock position  from the beginning of the takeoff roll through unstick and gear and flap  retraction - without a cut. This shot was taken from a modified B-25  flown by the legendary Paul Mantz, killed in the production of "Flight  of the Phoenix".    In the spectacular B-47 RATO takeoff, Paramount wanted a shot looking  directly aft from the cockpit to capture the rocket plume and receding  runway. But the canopy was in the way. The wing commander refused to let  one of his crews fly an open cockpit B-47, so the film's technical  advisor, Col. "Rapid Richard" Lassiter, did the flight himself. (I'm a  little skeptical of this story. Perhaps one of the rear transparencies  in the canopy was removed instead of the whole canopy?)    The crisis at the climax of the film begins during a trans-Pacific  flight when the reformed navigator (holding an E-6B) tells Stewart  they've picked up a headwind 50 knots more than forecast. Their B-47  will flame out short of the destination unless they come up with some ideas.    --  I filter out messages with attachments or HTML.  
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