Ep 17 The Hindenburg Disaster

The episode begins with a special segment on Women in Engineering to celebrate International Women`s Day (March 9th) and National Engineering Month in Canada.

This week`s engineering failure is the Hindenburg Disaster. Before there were airplanes, there were Zeppelins (9:50). In 1937, the Hindenburg Zeppelin caught fire during landing (18:00), engulfing the entire ship in flames in under a minute; ending the Zeppelin Era for good.


Women in Engineering:


Episode Summary

Hi and welcome to Failurology; a podcast about engineering failures. I’m your host, Nicole, and I’m from Calgary, Alberta.

  • It feels like we lost 2020 due to covid, and 2021 is already 16% complete! Crazy. And I’m over here, just yesterday, dating a file for March 2020.

  • International Women’s Day March 9th – this year’s focus/topic celebrate the social, economic, cultural and political achievements of women

  • National Engineering Month – events are taking place across the country of Canada to celebrate engineering and showcase to today’s youth what they can accomplish if they chose a career in engineering.

  • And thanks to covid, as terrible as it is, everything is online. So you can attend an event anywhere, at any time. I am actually attending an International Women's Day event which is hosted in Australia, which is really cool to hear from women in STEM across the world.

  • As a special segment for the month of March, in place of the news, I will be talking about Women in Engineering.


  • APEGA (Association of Professional Engineering and Geoscientists of Alberta) salary survey 2020 – the coveted salary survey. Did you know it also includes gender information?

    • Looked at 6 professional roles, including entry, experienced, senior, specialist, expert and pre-eminent

    • professional (57-78%) men, (12-25%) female

    • And 4 management roles, including team lead, manager, senior manager, head manager

    • management – (49-76%) male, (9-14%) female

    • Across all levels, men make 1-8% more than women in similar roles

  • Women As Levers of Change 2017-2018 – global study across fourteen legacy industries in the following sectors (energy, utilities, materials, industrials and consumer products (alcohol/tobacco)

    • Construction and Engineering 18% (1 in 5) of employment, 14% (1 in 7) in management, 10% (1 in 10) on executive boards

    • When comparing companies with the lowest percentage of women in executive management roles vs those with the highest percentage, there was nearly a 50% (a 47%) increase in profitability for companies with more women leading the charge

    • (32%) companies were 1/3 more transparent when they had the highest percentage of women serving on their executive boards

      • I can speak to this a little, although I can’t speak for all women. I don’t really have time to play politics. What is the problem, what is the solution, let’s move forward.

    • Women on boards in fourteen industries (energy, utilities, materials, industrials and consumer products (alcohol/tobacco)

      • 60% reduction on energy consumption

      • 39% improvement on greenhouse gas emissions

      • 46% reduction in water usage

      • 74% increase in corporate responsibility

  • Linked in – total connections vs female – I took a look through my linked in connections, I would say less than 20% of them are female. Ladies, if you’re listening, connect with me on linked in. There is a link in the show notes to my profile.

So you may be wondering why there are so few women working in engineering roles, specifically in management; and what we can do to improve this.

Limiting factors

  • Work life balance challenges – feel that

  • Unwelcoming culture

  • Perceived lack of career mobility – as evidenced by the lack of women in management roles.

  • Negative industry image

  • Gender imbalance in education – circular process

  • Maternity leave – impacting promotion and re-entry after leave

Tune in to next week’s episode for part two of this segment; where I will talk about what we can do as an engineering community to increase recruitment and improve retention. Now let’s get into the failure. What really happened to the Hindenburg?!?

Now on to this week’s engineering failure; the Hindenburg. Full disclosure, I was not aware until I started researching this episode that Zeppelins were a method of commercial travel around the world for over 30 years. I’ve just been walking around thinking that the Hindenburg disaster happened during a research and development process that went horribly wrong. Boy do I feel silly. Maybe I’m not alone though. Whatever the case, after this episode, we’ll all know what happened.

Before I get into the episode, I want to play a clip of news footage of the Hindenburg explosion and Herb Morrison's reporting of the event

I can’t imagine what it would have been like to stand there watching the airship come in to land, likely to meet a loved one who was travelling on the ship. And then to have the whole thing just go up in flames like that. It’s devastating. Today, mostly everything is caught on film. But back then, in 1937, this was one of the first disasters ever caught on radio and photographed.

What started the fire? And why did it burn so quickly? Well, there are a number of theories on what happened to the Hindenburg. The most widely accepted theory is that a static spark ignited leaking hydrogen. I’m going to get into that in more detail shortly, and I’m also going to briefly touch on all of the theories. 1 because I think they are interesting, and 2 because I think it's important to show that without adequate information to forensically analyze a failure, it can be quite difficult to determine what really happened. Even with adequate information, you’re always going to have varying opinions on what happened.

For example, a few weeks ago I was reviewing a pipe failure to try to determine why it failed. But the contractor who repaired it didn’t save the broken piece. And I got it, it was broken, he thought it was garbage. But one person’s trash is another person’s treasure. Had we had that piece, it could have been analyzed. But we didn’t. Luckily we had a photo of the failure in place that we could review. But for the most part, our analysis of the failure was speculation and included quite a number of assumptions.

Now I’m not saying this is what happened specifically on the Hindenburg. There was an investigation and I believe that all or part of the ship was taken back to Germany for review. But it was 1937, technology was fairly limited back then. And also, there was world war 2 to factor in. It started just two short years later. In fact, the Hindenburg was funded by the Nazis, which I also didn’t know. So I wouldn’t say that Germany was overly forthcoming or transparent with their findings.

Ship design

  • While Zeppelins had been in operation for decades, The LZ 129 Hindenburg model was only in its second year of commercial service - Hindenburg were largest Zeppelins ever to fly – first flight March 4, 1936, retired 1939

  • Think of like the Ford Pinto I covered in episode 5. Zeppelin would be the manufacturer like Ford, and the Hindenburg would be the model like the Pinto; ironically both of which exploded. That was a better example than I thought (laugh)

  • 245m long – 41m diameter – longer than 3 Boeing 747s end to end – longer than 5 Goodyear blimps end to end, only 24m shorter than the Titanic – if you haven’t listened to the Titanic episode, go check out ep 11.

  • Zeppelin - rigid airship – fabric covered rigid metal framework, 15 transverse rings which were numbered by the metre along the length of the ship - and 36 longitudinal girders –

    • inside the ship there were 16 individual gas cells – number started at 1 at the back or stern of the ship and worked forward

    • designed to be filled with non flammable helium for buoyancy, but due to US monopoly on the non-flammable gas (Helium Control Act of 1927 prohibited export of any other country), they were filled with hydrogen

    • The gas cells were originally made from goldbeaters skin made from intestines of cattle (grosse) – Hindenburg gas cells were made from sandwiching layers of gelatin film between two layers of cotton – this seems like very early on fiberglass

    • 14 manually controls maneuvering valves – operating by main gas board in control car – electric meters measured volume of each cell – pressurized relief valves on the cells

    • Valved 1-1.5 million cubic feet of hydrogen on each north Atlantic crossing – 7 million cubic feet total

  • Propelled by several engines, mounted in gondolas or engine cars outside the structural framework – some provide reverse thrust to maneuver during mooring – based on design for German E-boats (high speed torpedo boat) – 1320 hp x 4 engines (850hp in cruise) – started, stopped and reversed in flight – each drove a metal sheathed wooden propeller

    • Mounted in four engine cars, two at ring 92, two at ring 140

    • Mechanical stationed in each engine car

  • Auto pilot – gyroscopic compass to control the rudder and elevators to stay on course

    • Rudder controlled the left or right movement

    • Elevator controlled the pitch – tried to keep as level as possible

  • There was a walkway along the bottom of the ship that allowed crew to access the command centre, engine cars, fuel and water tanks, passenger and crew quarters, mail room, radio room, etc

  • There were ladders up from the bottom walkway to access the axial walkway along the top of the ship

  • Passenger space is part of the interior of the overall vessel – passenger rooms insulated from the exterior by the dining area – the grande piano was made with aluminum to reduce weight

  • water that cooled the front engines was used to warm air that was circulated throughout the ship. Its cool to hear about reclaimed heating from the 1930s

  • Viewing windows open during flight – no pressurization necessary, low flight ceiling

  • Positively pressurized air-locked smoking room – no flame allowed, one single electric lighter couldn’t be removed from the room

  • Carried twice the volume of lifting gas that previous Zeppelin models, due to larger diameter

  • Proposed designs, not implemented

    • When it was intended to be filled with helium – double wall gas cells, inner hydrogen, outer helium – to valve hydrogen and conserve helium – but they couldn’t get helium

    • Silica gel water recovery system to capture vapour from engine exhaust – partly compensate for fuel burned by the engines

    • Use engines that burn hydrogen – limited power output, 300hp – plans to add fifth engine to compensate for lower power output

    • Recover and launch fixed wing aircraft – hook an aircraft – Dark Knight Rises – attempts not successful

  • More than 30 years of passenger travel – tens of thousands of passengers – 2000 flights

  • Luxury interiors that are unmatched, even today – check out pictures on the episode webpage

  • Earlier that year it had completed a single round trip passage to Rio de Janeiro, Brazil

  • Departed Frankfurt Germany on May 3, first of 10 round trips between Europe and US

  • may 6, 1937

  • Delayed landing due to afternoon thunderstorms – strong headwinds during Atlantic crossing – half a day late

  • Flying moor – high landing – drop landing ropes and mooring cable at high altitude and be winched down to the mooring mast – common for US airships, Hindenburg had only performed a few times in 1936 – the ropes are important, remember that for later.

  • caught fire during attempt to dock

  • Lakehurst Naval Air Station, Manchester Township, New Jersey

  • 36 passengers, 61 crew – 13 passengers, 12 crew, 1 ground crew died – 23 passengers, 39 crew survived


  • 7pm made final approach

  • 709 pm turned away ground crew not ready

  • 711pm turned back to landing field

  • 717pm wind shifted direction, S-shaped flight path to mooring mast

  • 721pm 90m altitude, mooring lines dropped, starboard first then port, port line overtightened as it was connected to ground winch, starboard not yet connected to winch

  • 725pm – witness accounts differ

    • fabric of upper fin flutter as if gas was leaking

    • dim blue flame (static electricity or st elmo’s fire)

    • first flame appeared on the port side of the port fin, followed by flames burned on top

    • fire beginning lower and behind the rudder on the starboard side

    • on board – muffled detonation, felt shock in the front as the port trail rope overtightened – officers in the control car initially thought the shock was caused by a broken rope

    • port side yellow-red flames jump towards top fin near ventilation shaft of cells 4 & 5

    • helmsman stationed in lower fin – muffled detonation – bright reflection on front of bulkhead of gas cell 4 which “suddenly disappeared by the heat”

    • 4 newsreel teams and one spectator filming the landing – no footage or photos of the moment the fire started

  • fire spread more to the starboard side, ship dropped rapidly – consuming cells 1 to 9, rear end exploded

  • two tanks (water or fuel, not sure) burst out of hull from the shock of the blast

  • stern lost buoyancy, bow lurched upwards, burst of flames out the nose killing 9-12 crew

  • still gas in bow, continued to point up as stern collapsed down

  • hydrogen fuel burned up relatively quickly – diesel burned for hours

  • time it took was 32-37 seconds – flame spread estimate across fabric skin 15m/s (would have taken 16 seconds)

  • official board of inquiry at Lakehurst

There are a lot of theories on what happened to the Hindenburg. How did it catch fire and why did it burn so quickly? As I said, static electricity and a hydrogen leak is the most widely accepted theory.

Static electricity

  • Hugo Eckener – fire started by electric spark from static build up, ignited hydrogen on the outer skin

  • Some argued that skin wasn’t constructed in a way to allow the charge to distribute evenly throughout the airship – skin separated from the frame by non conductive ramie cords, lightly covered in metal to improve conductivity – insulation of fabric skin from flame was considered a design flaw – were able to recreate the spark and ignite the hydrogen, but the fabric didn’t ignite – not well publicized test and covered by to avoid embarrassment of an engineering flaw

    • Another spark theory – spark between ungrounded fabric segments caused the fire, igniting the highly flammable outer skin – cotton skin with “dope” finish (plasticized lacquer to provide stiffness, protection and lightweight, airtight seal) in liquid form, dope is highly flammable, but dry it depends on the base constituents

    • Discovery Channel show Curiosity “what destroyed the Hindenburg” episode – ignition took place above hydrogen vent, near where st elmo’s fire was seen, ignited hydrogen and channeled down the vent to create a detonation similar to what was described by crew

  • Weather delay was high humidity and high electric charge – mooring lines could have become wet when they were dropped to the ground (was raining), ropes grounded to the frame, but not the skin – spark jumped from skin to frame igniting the hydrogen

  • One observer claimed to have seen st elmo's fire


  • Most widely accepted

  • Airship was stern heavy before landing which could suggest a leak – mixing with oxygen and filling space between skin and cells

  • A couple claims of skin fluttering suggesting a leak

  • Pictures show the fire burning in straight lines, along the edges of the cells, rather than the continuous skin

  • Crew members in the stern reported seeing burning cells

  • Theories for gas leak

    • Snapped bracing wire tore gas cell open

    • Maneuvering or automatic gas valve was stuck open at cell 4 – no failure reported during or before landing

  • The fire was bright red, by hydrogen burns blue if visible – other materials consumed by fire could have changed the colour

  • Stern heaviness was normal during approach and corrected when the ship stopped (sent 6 men to the bow)

  • Gas cells were not pressurized – leak wouldn’t have resulted in fluttering

In addition there are other ignition and fuel theories.

Ignition Hypotheses

  • Sabotage

    • Hugo Eckener, former head of the Zeppelin Company, initially claimed sabotage as the cause, before he was briefed on the disaster – later endorsed the static spark hypothesis

    • Charles Rosendahl, commander of Naval Air Station at Lakehurst – in charge of ground based portion of landing – believed it was sabotage, he even wrote a book about it in 1938

    • Max Pruss – captain of the Hindenburg throughout the airship’s career – flew on almost every Graf Zeppelin since 1928 until the launch of the Hindenburg in 1936 – claimed that on two trips to South America, the airships were struck by lighting and were unharmed so it must have been sabotage

    • Couldn’t agree on whether a passenger or crew member

  • Lightning

    • Airship vents hydrogen as it lands, which can mix with oxygen and create a combustible mixture – this scenario occurs during landing but not necessarily during flight

    • No witness accounts of lightning

  • Engine failure

    • One engine, thrown into reverse for the hard turn (remember the S turn as it came in to land), backfired and caused a shower of sparks, igniting the outer skin

    • Hugo Eckener rejected the idea because exhaust temperatures (482C) were too low to ignite the hydrogen (500C)

    • Zeppelin carried out testing and the hydrogen didn’t ignite – fire seen at top of airship not near bottom of hull where engines were located

Now there were also a number of fuel theories. What fueled the fire and burned so quickly?

The incendiary paint, or doping compound on the ships outer skin was flammable to an extent and could have fed the fire. But investigations found that the skin burned too slow to fuel the fire like it did and that theory was ruled out.

And there was also a theory that believed that a fuel pump the day before the disaster created diesel vapours which could have been ignited from overheating engines. But several witnesses claimed to see the fire begin at the top of the shop, not at the bottom where the engines were located, so this theory was ruled out as well.

Now I don’t really know what happened, I wasn’t there. It could have been the static spark, combined with a leaking gas cell that caused the ship to burn up so quickly. Or it could have been a combination of some of the other theories I’ve listed. With concrete evidence or a credible investigation, I would say the theories are speculation at best.

One thing we do know is that airship travel ended pretty quickly after this.

  • What happened to zeppelin travel after this?

  • Not the worst Zeppelin disaster, just the first to be caught on camera and shared with the public; effectively ending airship commercial travel right then and there. No deaths from German airships though until the Hindenburg

So there you have it. The almost, but not quite story of what happened to the Hindenburg. How a luxurious airline went up in flames in less than half a minute. Effectively ending zeppelin travel for good. While it took 3 days to cross the ocean in a Zeppelin, which is far too long for me; it would be cool to travel in the luxurious cabin. With my own room and a dining lounge area. That sounds way more comfortable than 10 hours sandwiched into a metal tube with 100 strangers. At least in the Zeppelin you could stretch your legs.

For photos and sources from this week’s episode, head to failurology.ca; there’s a link in the show notes. I’ve also included links to the APEGA salary survey, women as levers of change survey and the national engineering month event calendar that I mentioned at the top of the show

If you’re enjoying what you’re hearing, please rate, review and subscribe to failurology, so more people can find it. And tell all your friends! If you want to chat with me, my twitter handle is @failurology, you can email me at thefailurologypodcast@gmail.com, or you can connect with me on Linked In. Check out the show notes for links to all of these.

Thanks everyone for listening. And tune in next week to hear about the John Hancock Tower in Boston. The tower had several problems, but most notably, over 10,000 panes of the exterior glass had to be replaced during construction because they kept falling off the building. But more on that next week. Bye everyone, talk soon!