Editing LZ 129 Hindenburg (section)

===First commercial passenger flight===
[[File:Zeppelin Passenger Pins.jpg|thumb|right|upright|Zeppelin passenger lapel pins]]
[[File:Hindenburg in Rio 1936.jpg|thumb|left|The ''Hindenburg'' after its first flight to Rio in April 1936. There is a temporary repair of the lower fin after the accident at ''Die Deutschlandfahrt''.]]

With the completion of voting on the referendum (which the German Government claimed had been approved by a "98.79% 'Yes' vote"),<ref>"Hitler gets biggest vote: Many blanks counted in, 542,953 are invalidated.  Some 'Noes' Not Counted; Confusion Causes Counting of Blanks and Many May Have Shown Opposition". ''The New York Times'', March 30, 1936.</ref><ref>"Foreign News: May God Help Us!" ''Time'', April 6, 1936</ref> ''Hindenburg'' returned to Löwenthal on March 29 to prepare for its first commercial passenger flight, a transatlantic passage to [[Rio de Janeiro]] scheduled to depart from there on March 31.<ref>Mooney 1972, pp. 82–85.</ref> Hugo Eckener was not to be the commander of the flight, however, but was instead relegated to being a "supervisor" with no operational control over ''Hindenburg'' while Ernst Lehmann had command of the airship.<ref>"Transport: Von Hindenburg to Rio." ''Time'',  April 13, 1936.</ref> To add insult to injury, Eckener learned from an [[Associated Press]] reporter upon ''Hindenburg''{{'}}s arrival in Rio that Goebbels had also followed through on his month-old threat to decree that Eckener's name would "no longer be mentioned in German newspapers and periodicals" and "no pictures nor articles about him shall be printed."<ref>Mooney 1972, p. 86.</ref> This action was taken because of Eckener's opposition to using ''Hindenburg'' and ''Graf Zeppelin'' for political purposes during the ''Deutschlandfahrt'', and his "refusal to give a special appeal during the Reichstag election campaign endorsing Chancellor [[Adolf Hitler]] and his policies."<ref>"Eckener Refused Election Plea for Hitler: Name Barred From the Press as a Result." ''The New York Times'', April 3, 1936.</ref> The existence of the ban was never publicly acknowledged by Goebbels, and it was quietly lifted a month later.<ref>"'Eckener's Disgrace Ends: Zeppelin Expert is Victor in Clash with Goebbels." ''The New York Times'', April 30, 1936.</ref>

While at Rio, the crew noticed one of the engines had noticeable carbon buildup from having been run at low speed during the propaganda flight days earlier.<ref>Dick and Robinson 1985, p. 119.</ref> On the return flight from South America, the automatic valve for gas cell 3 stuck open.<ref>Dick and Robinson 1985, p. 118.</ref> Gas was transferred from other cells through an inflation line. It was never understood why the valve stuck open, and subsequently the crew used only the hand-operated maneuvering valves for cells 2 and 3. Thirty-eight hours after departure, one of the airship's four [[Daimler-Benz]] 16-cylinder [[diesel engine]]s (engine car no. 4, the forward port engine) suffered a [[wrist pin]] breakage, damaging the [[piston]] and [[Cylinder (engine)|cylinder]]. Repairs were started immediately and the engine functioned on fifteen cylinders for the remainder of the flight. Four hours after engine 4 failed, engine no. 2 ([[Fore and aft|aft]] port) was shut down, as one of two bearing cap bolts for the engine [[crankshaft]] failed and the cap fell into the crank case. The cap was removed and the engine was run again, but when the ship was off [[Cape Juby]] the second cap broke and the engine was shut down again. The engine was not run again to prevent further damage. With three engines operating at a speed of {{cvt|100.7|km/h}} and headwinds reported over the [[English Channel]], the crew raised the airship in search of counter-[[trade wind]]s usually found above {{convert|1500|m}}, well beyond the airship's [[pressure altitude]]. Unexpectedly, the crew found such a wind at the lower altitude of {{convert|1100|m}} which permitted them to guide the airship safely back to Germany after gaining emergency permission from France to fly a more direct route over the [[Rhone Valley]]. The nine-day flight covered {{convert|20529|km}} in 203 hours and 32 minutes of flight time.<ref>"Two Motors Crippled as Zeppelin Lands." ''The New York Times,'' April 11, 1936.</ref> All four engines were later overhauled and no further problems were encountered on later flights.<ref>Lehmann 1937, pp. 341–342.</ref> For the rest of April, ''Hindenburg'' remained at its hangar where the engines were overhauled and the lower fin and rudder received a final repair; the ground clearance of the lower rudder was increased from 8 to 14 degrees.