Airships: Hindenburg
Flight Procedures and Controls
Normal Cruise Altitude
Hindenburg had a normal cruising altitude of 200 meters (650 feet), but was often flown much lower to stay below the clouds. Hindenburg’s officers believed it was important to observe cloud formations before entering them, to be able to assess the nature of the clouds and avoid thunderstorms, and Hindenburg flew as low as 100 meters (330 feet) when necessary to stay below the clouds.
It was also a fundamental premise of zeppelin operations taught by Hugo Eckener that ships should avoid traveling close to their pressure height, because of the possibility of ascending above pressure height and valving hydrogen, which always presented a certain risk of fire, especially in electrically charged environments.
Hindenburg’s low cruising altitude also provided passengers with spectacular views.
Normal Cruise Speed
Hindenburg’s engines were operated at a cruise setting of 1350 RPM during passenger operations, giving the ship an airspeed of approximately 125 km/h (approx. 67 knots, or 76 MPH), and this setting was rarely adjusted during a normal passenger flight.
Hindenburg’s normal cruise setting produced 820 h.p. and consumed 130 kg/hr of diesel fuel. If needed, Hindenburg’s engines could be operated up to 1520 RPM for full power, which produced 1050 h.p. and consumed 180 kg/hr of fuel.
Heading Control
Hindenburg’s heading was controlled by its rudders, which were manipulated by the helmsman (or rudderman), whose primary job was to keep the ship on its assigned heading.
The rudderman stood at the front of the control room, facing forward, and steered by reference to a repeater compass mounted in front of the wheel, which was controlled by the master gyroscopic compass located on the ship’s electrical room. The rudder station also had a magnetic compass, and pointers indicating the angle of deflection of the upper and lower rudders.
Pitch and Altitude Control
Hindenburg’s pitch was controlled by the ship’s elevators, which were manipulated by the elevatorman, whose primary job was to keep the ship as level as possible, primarily in the interest of passenger comfort.
The elevatorman was also expected to keep the ship at its assigned altitude whenever possible, but a much higher priority was placed on maintaining level trim than holding a fixed altitude. Pitch angles exceeding 5 degrees were considered to cause discomfort to passengers (an angle of 8 degrees or more would cause cups and glasses to slide off tables), and also increased fuel consumption, and Hindenburg’s officers also believed that steep angles of pitch placed a strain on the ship’s structure. Elevatormen were therefore expected to keep the ship as level as possible, even if it meant deviation from the assigned altitude, or required severe control inputs to counter the movement of the ship.
The elevatorman maneuvered his wheel partly by the feel of the ship, but primarily by reference to the instruments on the elevator panel, which included pointers to indicate elevator deflection and inclinometers to indicate the ship’s pitch. Each inclinometer was a curved glass tube containing a bubble which moved with changes in pitch, on the same principle as a carpenter’s level. The elevatorman was expected to “chase the bubble,” in other words, to spin the elevator wheel so his reference pointers chased the bubble in the inclinometer to keep the ship level.
The elevatorman also maintained a continuous scan on the other instruments on his panel, which displayed information about factors which would influence the ships’s pitch and altitude. These instruments included thermometers indicating ambient and gas cell temperatures, a hygrometer indicating humidity, a statoscope indicating small changes in altitude, a variometer (or vertical speed indicator) indicating the ship’s rate of climb or descent, and an altimeter.
Automatic Pilot
Hindenburg was equipped with a gyroscopic compass and automatic pilot system made by the Anschutz Company of Kiel, which used servo motors guided by the ship’s gyro compass to control the rudder and elevators and maintain the ship’s heading and pitch.
The master gyroscopic compass was located in a compartment just forward of the electrical room and controlled five repeater compasses (one at the rudder station, three in the navigation room, and one at rear of the control car).
The Anschutz automatic pilot system, after some initial adjustments, was accurate and effective, and in smooth weather it could hold a straighter course, and with application of smaller rudder angles (usually less than 3 degrees), than could be done by an experienced helmsman. When calm conditions prevailed, the auto-pilot sometimes remained engaged for as long as 40 hours.
The system was used only in calm conditions and at higher altitudes; when rough weather was encountered, or when the ship was operated closer to the ground, the system was disengaged and the elevators and rudders were manipulated by hand.
Elevator and Rudder Inputs
There were no specific procedures limiting the rate or angle of rudder and elevator deflection. While there was a general understanding among the crew that full ruddder and elevator inputs should be used judiciously, especially in rough air, the controls were sometimes put hard over as rapidly as the wheels could be spun.
Sharp turns were occasionally made without significant concern for possible strain on the ship, and rudder angles up to and exceeding 15 degrees were observed. For example, a memo by U.S. Navy observer Lt. Cdr. Francis Reichelderfer described a flight on Hindenburg in August, 1936, and noted:
During the flight over Washington Captain Lehmann was asked by a passenger to change course to pass over a spot which was close aboard. In response to Captain Lehmann’s orders to the steerman full rudder angle was applied with maximum possibly speed with no apparent questions by any of the officers in the control car. The air at the time was very rough…. My impression from that observation is that the ship was turned in the rough air typical of a summer afternoon overland, as sharply as a turn could be made and that the maneuver which appeared to me to be undesirably rough use of the controls was taken as a matter of course by the several Hindenburg officers in the control car.
The elevators were also frequently put hard over when necessary to keep the ship level, and Hindenburg’s officers believed (perhaps erroneously) that steep angles of pitch placed more strain on the ship than the hard maneuvering sometimes required to avoid them.
Applying sufficient elevator input to keep the ship in trim often required great physical effort, and a U.S. Navy observer, Lt. (j.g.) M. F. D. Flaherty, reported:
On several occasions the elevatorman was seen to change elevator angle from fifteen degrees up to fifteen degrees down just as fast as he could spin the wheel. Flying under bumpy conditions required a great deal of physical exertion…. After about twenty minutes on the elevator the operator became soaked with perspiration… In order to reach eighteen degrees up elevator angle to counteract a down inclination of the ship it seemed to take all the strength that the operator could apply… The maximum angle of inclination the ship assumed…was about five degrees up by the bow.”
Maintenance of Static Equilibrium
While Hindenburg usually began a transatlantic flight with its full capacity of slightly more than 7 million cubic feet of hydrogen, it usually landed with between 5 and 6 million cubic feet of gas remaining in its cells.
Hindenburg’s watch officers attempted to keep the ship from flying more than three degrees heavy or two degrees light, and the ship was generally flown within a half degree of static equilibrium; valving hydrogen during flight was an important part of that process.
The officers paid considerable attention to keeping the ship in equilibrium to avoid the need for steep angles of pitch, which would disturb the passengers, decrease speed, increase fuel consumption, and strain the ship. Having a level ship with full elevator control in both directions also made it safer to fly at lower altitudes, and since Hindenburg frequently flew only a few hundred feet above the surface, to stay under clouds and observe weather conditions in the ship’s path, it was considered especially important to keep the ship in static equilibrium. And Hugo Eckener had long warned airshipmen of the danger of driving a ship “dynamically to death; that is, to demand so much of her dynamically that in the event of a…stoppage of the motors the static resources will not suffice to keep her airborne.”
Since an airship becomes lighter as it burns fuel during flight, in order to maintain static equilibrium it is necessary either to generate additional ballast or to release lifting gas. Hindenburg’s engines were not equipped with water-recovery equipment (to create water from engine exhaust), and the ship’s system of rain gutters did not provide a reliable supply of ballast.
Without a dependable source of additional ballast, gas was valved freely to maintain equilibrium, and the ship routinely valved up to 1.5 million cubic feet of hydrogen during a North Atlantic crossing.
Valving, Replenishment, and Purity of Hydrogen
Hindenburg’s liberal valving of hydrogen to maintain level trim required the addition of about 20% fresh hydrogen every seven to ten days, which increased operational expenses, but had the benefit of maintaining the ship’s lifting gas at a high level of purity.
Maintaining a high level of purity (in other words, avoiding contamination of hydrogen by air) was an important safety feature in dealing with the flammable gas; pure hydrogen is difficult to ignite, but hydrogen mixed with air is highly volatile, so the purity of the gas was closely monitored.
Navigation
Hindenburg navigated across the ocean primarily by means of dead reckoning; celestial navigation was rarely used, and when sightings were taken they were almost always for training and instruction rather than for navigation. Hindenburg was also equipped with direction finding equipment which could take fixes on radio stations on land or at sea to confirm the ship’s position, but radio navigation over the ocean at the time was rather primitive, and it was not considered nearly as accurate as dead reckoning.
Dead Reckoning
Hindenburg’s extremely precise dead reckoning was made possible by the accuracy of the ship’s drift measuring equipment and gyroscopic compass, and by the fact that the ship generally flew at a regular speed; Hindenburg’s engines were operated at a cruise setting of 1350 RPM during the course of a passenger flight, and this setting was rarely altered during flight.
Pressure Pattern Navigation
Like Graf Zeppelin, Hindenburg often used the technique of pressure pattern navigation which had been pioneered by Hugo Eckener during LZ-126’s crossing to America. Pressure pattern navigation takes advantage of the Coriolis effect, which causes wind to circulate in a counter-clockwise rotation around areas of low pressure in the northern hemisphere. During a westbound crossing of the north Atlantic, therefore, an airship can pick up a tail wind by skirting the northern edge of a storm, and during an eastbound crossing the ship can do the same thing by skirting the southern edge of a storm. Rather than avoid storms and fronts completely, therefore, Hindenburg’s officers frequently took advantage of them to increase speed and efficiency.
The Weather
The weather was perhaps the single most important factor in zeppelin operations. As Captain Lehmann once told a group of passengers on a tour, the meterological space “is where our mental processes begin; we study the weather and then we plan our flights.”
Weather Maps
During a north Atlantic crossing, the officers of Hindenburg drew four weather maps a day, based on information received by radio from land stations and ships at sea, as analyzed and relayed by the Deutsche Seewarte at Hamburg and radio station NAA of the United States Weather Bureau. Hindenburg would also contact ships sailing over its intended course for additional weather information, and a chart showing the location of seagoing vessels on the Atlantic was maintained for this purpose.
Hindenburg’s officers spent much time preparing the daily weather maps and consulted them extensively while flying the ship. The first duty of an officer beginning his watch was to make a detailed study of the most recent weather map.
The officers used these maps both to avoid dangerous fronts and squalls when possible, but also to take advantage of storms to increase speed and efficiency through the technique of pressure pattern navigation.
Two of the daily maps were large scale, covering the entire area from the interior of the United States to Russia, while two of the maps were less extensive, and covered primarily the Atlantic ocean. The relative scarcity and frequent inaccuracy of the weather reports passed on by ships at sea, however, was a source of of difficulty for the officers relying on this information to chart the weather.
Thunderstorms
While the German officers generally viewed Hindenburg as an all-weather ship, they were very sensitive to the danger of thunderstorms and generally kept their ship below the clouds so they could observe and assess threatening clouds before entering them. In Hugo Eckener’s 1919 instruction guide for zeppelin operations (the closest thing the crew of the Hindenburg had to a flight manual), Eckener stated: “The fundamental principle covering squalls and thunderstorms is: If possible, avoid such cloud formations!”
Thunderstorms presented two principal risks; the potential for structural damage, and the possible ignition of hydrogen by electrical activity. The Germans were very sensitive to the possibility of structural damage caused by the violent convective activity in and around thunderstorms (such as the structural failure which destroyed the USS Shenandoah). The Hindenburg’s officers were also aware of the danger posed by thunderstorms when operating with hydrogen as a lifting gas. Since the strong updrafts of a thunderstorm could cause the ship to rise above pressure height, resulting in the automatic release of flammable hydrogen in an electrically charged environment, Hindenburg’s officers generally went to great lengths to avoid operating in or near thunderstorms, and one of Hugo Eckener’s basic operating rules was that a zeppelin should never valve hydrogen in a thunderstorm.
Hindenburg Flight Manual
No flight or operations manual exists for the Hindenburg or the Graf Zeppelin, and neither the DZR (German Zeppelin Transport Company), which operated the Hindenburg, nor the LZ (Zeppelin Construction Company) which built the Hindenburg and built and operated the Graf Zeppelin, ever prepared a manual for operational or training purposes. There was no formal ground school for flight personnel, and all training was done by the apprentice method.
A flight manual was apparently in the process of being prepared at the time of the Hindenburg disaster; in a memo dated August 23, 1936, U.S. Navy officer Garland Fulton described a conversation with Ernst Lehmann about crew recruitment and training and noted: “The new manual on airship, which has been in preparation by the Germans for some time, is not yet complete. Captain Lehmann hopes to see its completion next winter. Meanwhile, the old manual prepared in 1918 by Dr. Eckener (“Brief notes and practical hints for the piloting of Zeppelin Airships”) is still a good guide as to German doctrines and practices…. There is no ‘ground school’ as such.”
An operations manual was not really needed by the flight personnel of the Hindenburg, since most of the officers and crew had been flying on zeppelins for decades (many began their zeppelin careers during World War I, and a few had even worked for the DELAG in the years before 1914). Training was all done hands-on, with new crew members learning their jobs from experienced hands. And the Hindenburg was also, in many ways, an experimental aircraft; it was the first in its proposed class, and was used as a flying laboratory for the development and testing of both equipment and procedures. If the planned expansion of the zeppelin fleet had taken place, more formalized training and reference materials would have been required, based on lessons learned from the Hindenburg, and these materials were apparently being prepared.
The DZR did have a “Crew Manual,” but it only briefly mentions operational matters (e.g. job descriptions for the elevator and rudden men, a list of landing station assignments by position, and a description of the Standby Watch duties of various crew members). Most of the Crew Manual discusses matters such as rank insignias and detailed uniform requirements and allowances (senior officers received RM 100 to purchase uniforms from a tailor of their choosing), and certain rules and regulations (“In using the wash rooms and toilets, every one should be careful to be neat and clean”).
The Officers and Crew
Hindenburg, like all large rigid airships, was not piloted like an airplane or a blimp, but commanded like an ocean-going vessel. Flying the Hindenburg was a complex operation which required the coordinated efforts of many individuals to operate and maintain the airship, monitor and respond to the weather, and navigate across long distances.
The Flight Crew
The ship was flown by a minimum flight crew of 39 officers and men (not including passenger service personnel such as cooks and stewards) under the command of the captain:
Captain
3 Watch Officers
3 Navigators
3 Ruddermen (helmsmen)
3 Elevatormen
Chief Rigger (Sailmaker)
3 Riggers (Sailmakers)
Chief Radio Officer
3 Assistant Radio Operators
Chief Engineer
3 Engineers
12 Machinists/Mechanics (assigned to engine cars)
Chief Electrician
2 Assistant Electricians
In addition to the flight crew, the ship’s passengers were served by a Chief Steward, a Chief Cook, and 10-12 stewards and assistant cooks. Hindenburg also began carrying a doctor in 1937.
Crew Watches
The ship’s personnel stood watches, as aboard a surface vessel. The watch officers, radio officers, engineering officers, and most other personnel stood a 4 hour watch, then had 4 hours of rest, and then spent 4 hours on standby watch (Pikett-Wache). Certain crew members stood 2 hour watches during the day and 3 hour watches at night, when conditions were generally calmer; these included the rudder men and elevator men, whose jobs were both mentally taxing and physically exhausting; the mechanics, who dealt with the noise and vibration of the engine cars; and the riggers, who prowled the ship inspecting and repairing gas cells, covering fabric, and other structural elements.
Crew members were assigned secondary duties during their standby watch; for example, the Radio Officer was responsible for handling the mail and making lists of passengers, the 1st rudder man was responsible for maintenance of the crew’s living and sleeping quarters , etc.
As on a surface vessel, the commanding officer stood no watch, but was of course always available.
Organization and Coordination of the Flight Crew
The flight crew was divided into two divisions; the navigation department (similar to the deck department on a steamship), who worked in and around the control car, and who were responsible for flying and navigating the ship (this group included the captain, watch officers, elevatormen, ruddermen, and radio operators), and the engineering department, who worked in the hull and engine cars of the ship, and who were responsible for the gas cells, power plant, fuel and ballast supply, and the structure of the ship (this group included the engineers, mechanics, electricians, and riggers). [Passenger services were provided by the stewards, headed by Chief Steward Heinrich Kubis, and the cooks, headed by Chief Cook Xaver Maier.]
Chief Engineer Rudolf Sauter at the engine telepgraphs in the Engineering Room along the keel.
Chief Engineer Rudolf Sauter
There was a distinct division between the two departments, who worked more or less autonomously under their respective chiefs, with surprisingly sparse communication about operational matters. In general, the captain and watch officers confined their attention to matters of navigation and flight control, and had confidence that the engineering department would keep the rest of the ship in excellent operating condition without much direct oversight. For example, one U.S. Navy observer noticed that when an engine was stopped during flight, the watch officers seldom asked the engineering officer to explain the cause of the stoppage, but were content simply with the engineer’s estimate of how long the engine would be out of service.
Crew responsibilities sometimes varied from the official job descriptions, however, in recognition of the backgrounds and specialties of particular individuals. For example, Captain Albert Sammt, who served as a Watch Officer, had years of experience with the construction and maintenance of gas cells and fabric covering, and so Chief Rigger Ludwig Knorr, in the engineering department, reported to Captain Sammt, in the navigation department. (Sammt and Knorr, along with Knut Eckener and Hans Ladwig, were the riggers who repaired the torn fin covering during Graf Zeppelin’s first flight to America.)
The Zeppelin Culture of Responsibility and Independence
There was, in general, a great deal of independence, autonomy, and discretion entrusted to individual members of the Hindenburg’s crew. For example, watch officers had the authority to valve gas, drop ballast, change the ship’s assigned altitude, and even alter course without the direct involvement of the captain. Of course, Hindenburg’s senior officers all had decades of service in zeppelins, and watch officers were generally qualified as airship captains themselves. Similarly, elevatormen were usually highly experienced, and were given wide discretion in the performance of their duties, as were ruddermen.
Landing Procedures
The way landings were conducted in the control car exemplified the independence and responsibility entrusted to the ship’s senior officers: Landing orders were given and executed by three watch officers acting on their own initiative, with the ship’s captain observing the landing evolution as a whole. Each officer, as well as the elevatorman and rudderman, had considerable discretion in performing his individual duties, and the commanding officer seldom issued a direct order. The captain observed the entire operation as a whole, but generally intervened only in the case of difficulty or if he disagreed with the actions of his officers.
Several of the United States Navy officers who flew as observers on the Hindenburg described the landing procedure, which was notably different from the procedure followed aboard American naval airships, in which the commanding officer actively directed the landing.
Lt. J.D. Reppy, who flew on four transatlantic flights of the Hindenburg, wrote:
Captain Lehmann of course would be on the bridge for the landing but generally acted in the capacity of observer and only gave an order when he considered that [some] phase of the landing was not going as it should. One officer handled the engines and he used his own judgment as to slowing, stopping, or backing the engines to have little or no ground speed at the instant of landing. Another officer had charge of the ballast and here also he exercised his own judgment as to when to drop ballast and also as to when to valve hydrogen…. The remaining officer coached the elevator man as to altitude and sometimes would order the ship valved if it appeared necessary. He also watched the rudderman to some extent but in general the rudderman maneuvered the ship himself, as necessary, to keep in the wind and pointed towards the landing point.
A similar description was provided by Lt. Cmdr. Francis Gilmer, who was an observer during four other transatlantic flights:
At “take offs” and “landings” the three senior watch officers are in the control car, in addition to the Commanding Officer. The officer with the watch is charged with the maneuver and one of the other watch officers directs the use of the elevators, the valving of gas and the dropping of ballast; the remaining watch officer directs the rudderman. There is excellent team work between the three. The Commanding Officer is of course in charge but seldom issues and order.
A Note About Sources:
As discussed above, the DZR (German Zeppelin Transport Company), which operated the Hindenburg, never produced a flight manual describing airship operations. The information on this page has been pieced together from a number of sources, including contemporary flight logs, photographs, the DZR Crew Manual, and Hugo Eckener‘s 1919 flight manual for the DELAG, and most importantly, on the reports and memoranda produced by American Navy officers who flew on the Hindenburg as observers, as well as the reminiscences and observations recorded by German zeppelin officers and by Harold Dick, the American representative of the Goodyear-Zeppelin Company who was based in Friedrichshafen and flew on numerous flights of the Hindenburg and Graf Zeppelin.
