Macon “Post-Mortem”

kingFuture C-in-C Fleet Admiral E. J. King, then RADM and Chief of BuAer (photo), issued BuAero letter Aer-La-MW 5/1 directing that the Macon and Sunnyvale officers reach consensus and report on lessons learned from operations with rigid airships, especially the Navy’s flying aircraft carriers, the USS Akron and Macon. He was in a hurry do get this done while the impressions were still fresh, less than two weeks after Macon sank. When drafting the response, protocol forbid criticism of senior leadership’s  understanding of, and fleet experiments with, these unique aircraft. From the Akron’s first exercise (to look for a destroyer), to the Macon’s final act of unnecessary risk of operating with a known if underestimated structural deficiency, it is clear senior leadership failed to grasp a flying carrier’s full open-ocean search capabilities. Dr. R.K. Smith wrote, “There is something grotesque, pathetic, and deplorable about this three-million-dollar aircraft with its unique, very-long-range capability being obliged to stooge around in a cramped air space in an effort to execute missions better executed by a $25,000 scout bomber or a $150,000 flying boat.”

4-goofy-copyLike the person who created this image did not understand why such a photo is impossible, the Flag ranks simply didn’t get what the ZRS ships offered the Fleet. Even after Wiley’s bold demonstration of finding the vacationing Roosevelt’s cruiser several days out in the open Pacific,  Smith continued, “There is no suggestion that anyone on the staffs of CinCUS, ComBatFour, or ComAirBatFor was assigned to work out a place in the Fleet’s operations which would exploit the special characteristics of this expensive machine. Nor did CinCUS request a liaison officer from Moffett Field. The Macon was simply thrown in to sink or swim with Admiral Sellers’ orders to “scout tactically.”

image-27-copy(Actual image of Akron over San Francisco) There had been no change to the Navy’s scouting manual to accommodate the dirigible’s airplane scouts, let alone the report’s projected uses of two or more flying carriers and their planes forming a scouting line. In that case, a passive “station” type scout line could have been placed along the enemy’s suspected track. Ultimately, with the Congress assigning the rigid airship to the Navy, credit for their successes and blame for their failures cannot be placed elsewhere.

5-bow-mast-1Responding to RADM King’s order, the massive “Macon post-mortem” report was completed in April and forwarded to BuAer. (While a copy was sent to Lakehurst, nothing in the report specifically mentions unique experience there. ) Very little in this report cast light on the causes of the accidents that lost both ZRS-4 & 5, nor made design recommendations for any new ship solely based on such perceptions of specific failures. The report reflected the solid experience of operating the all the previous airships. As hoped for, the “wish list” generated to direct the creation of the next-generation dirigible was based on real-world conditions. It is reasonable to assume the ZRCV would have gained from this documented experience, rather than only around real or imagined grievances or design flaws concerning the losses of both Akron and Macon. 

In a most passionate paragraph, the report urges, “In making recommendations for future developments it cannot be too strongly stressed that the maximum accomplishments can be attained only by constant participation in fleet activities and by working out the airship problem in conjunction with fleet exercises, to the end that a common knowledge be gained of the problems of surface craft and airships. At the same time scheduled period should be allotted to the airship commander for developing the technique of airship handling, navigation, weather and meteorological study, plans operations, plane navigation from the ship, and for the general indoctrination and training of personnel during long distance cruising.” True Navy professionals, the officers composing the report devoted many pages to the art of scouting for the Fleet. Included were practiced and theoretical techniques, including “shadowing” an enemy—reporting his position while remaining out of his weapons range— the way Zeppelins once frustrated British Fleet efforts to remain unobserved.

5-mast-liftoffA large percentage of the report notes successes, failures and room for improvement in the existent Akron/Macon design, reading like sort of a logbook of experiences and operations manual. While specific sections recommend design features to be included in the next rigid, ideas for that future airship were also intertwined in the factual reporting and comments about actual experience.

Reproducing the entire report here is impossible, but we will attempt to highlight the most important points.

akron-general-copyThe report was satisfied with the ZRS hull shape, but recommended that more interior space be devoted to gas rather than wasted in dead air. A return to the single lower keel was recommended.  Stronger girder structural members were on the wish list. (In fact Goodyear-Zeppelin was already experimenting with variations to and improvements on the girder technique seen being used in the construction of LZ-129.)

The outer covering was seen as satisfactory, but it was hoped better watertight integrity and sealing against leaks would be possible. (Ironically, the same emphasis about not taking on water weight in rain was then being worked on the LZ-129 in Germany… and would become the fatal link in the chain that made LZ-129 vulnerable to the environment that infamous night.) While C.P. Burgess had hailed the metalclad as “the ultimate airship,” nothing in the report suggests a mono-coupe hull was a desirable option by the rigid airshipmen.

20150626_142912They felt the need for more cells, in keeping with the German practice, or at least less difference between major and minor cell capacity. Since the ramie cord netting was constantly stretching and breaking, wire cell netting was recommended, with smaller squares to prevent bulge-through. The use of hydrogen anti-ballast and /or gaseous fuel was not seen as paying off its complexity. (Success of the LZ-127 notwithstanding, it should be noted BuAer LTA engineer CP Burgess specifically called out for gaseous fuel in his 1935 memo for an experimental non-rigid airship to apply lessons learned from the K-1, the so-designated K-2.) Likewise, a return to wire-braced bulkheads were desired because the deep main ring’s elastic bulkhead’s resiliency devices (arrow) required constant maintenance and many were difficult to access.


There was a most emphatic desire to return to exterior power cars, using the more efficient water recovery, possibly adjacent, if not in, the car. The early plan of two engines per car was suggested. A 60 degree thrust vector was considered satisfactory and needed only on the forward power cars. (The Germans had experimented with a vectoring gearbox arrangement on LZ-127’s forward cars, photo.) Not all agreed that gasoline tanks should be larger, but there was consensus that all fuel should be droppable from the control car.

It was suggested a two-bladder bag be adopted so drinking water could share a bag with seawater or exhaust-recovered water. A “grey water” setup to recover wash water to use as flushing water would help reduce take-off weight. Ballast baggage, valves and plumbing would need anti-corrosion protection, particularly if seawater pickup was developed further. Bags were never trusted with full water loads and, like most of the rest of the water systems, they had to be replaced annually.

dsc00784There was also universal dislike for the in-line engine-propeller arrangement. (Photo: Entering an engine room. Arrow: Voice tube, which ran on both sides all the way aft to engines 1 & 2. ) Rosendahl later summarized, “The aftermost propeller was at Frame 57-1/2 and the vibrations “snowballed” to their heaviest aft of that point.  It is more than merely conceivable that these transmitted cumulative vibrations accelerated the deterioration of the already deficient Frame 17-1/2.”  The Durand Committee called it out emphatically: “This arrangement was prejudicial to propeller efficiency, each propeller except the leading one working in the slip stream of those ahead.  Severe vibrations also developed with all engines in operations, especially in the vicinity of the after propeller.”

A tool control crib, or at least better co-ordination between departments to prevent duplicate tools being carried, was recommended to save some weight.

imag0042-copyThe airshipmen noted their sluggish aerograph and inaccurate psychrometer made these readings less useful, suggesting a better protective thermo-shelter in any future ships. (Drift gauge in use, photo; see below about its proposed mounting on the cloud car.) Instead of the 12 hour weather reports, airshipmen proposed eight-hour intervals as more practical, and suggested more aerologists be trained to be familiar with LTA operations. They suggested weather reporting from ships at sea be improved and US Government-subsidized ships be required to make regular weather reports. There was no specific mention for better communication of the weather situation to the bridge and/or navigator, but the report called for better intra-ship communication. Voice tube communication to extreme ends of its system were called out as being noisy and ineffective.

There was a hope that portable radios in the UHF range, then in prototype, be developed so different “channels” could be arranged for Gunnery and fire control, as well as lookouts and sub-cloud car. In the interim it was suggested these be developed and tested with a non-rigid equipped with a sub-cloud car, like the K-1 or the Army TC-13 then dsc00749flying.  The report noted that the radio-homing gear could be adapted to receive and home in on enemy signals, as well. (Photo, Macon’s radio room with Radioman Ernest Dailey at his post. He was lost with his ship.  Arrow: the hand-cranked wheel by which he deployed or recovered the trailing wire antenna. Voice tube rests near it.) Sadly, even with the perfection of Huff-Duff in WWII and at the height of U-boat success, no such gear was ever mounted in an airship.)

They foresaw major control cabling being simplified by use of servos and gyros. Indicators showing actual control surface position were recommended. They were unhappy with the bow-weighing device, and looked for improvement.

5-1-lateZRS operators had noted a “morning heaviness” trend that caused the airships to be thousands of pounds heavy during the first hour or two of operations. This was generally believed to be due poor hull ventilation, so they recommended lesser wasted air space and better hull vents. West coast operations frequently encountered temperature inversions anywhere from 500 to 2500 feet, where air as much as 30 degrees warmer than the surface complicated full ship operation. (Macon operators specifically called out the “new bridge across the Golden Gate” complicating takeoffs since 1000 foot altitude was required soon after full-weight takeoff.)  Recalling tests done on Los Angeles, they recommended some hot air or steam plant be installed at the mast so the cells could be artificially superheated to allow lift-off in full-load soggy conditions as might come in wartime.

5-topside-copy-copyA wire-mounted, fully articulated seat for the “topside control officer” was to have full 360 degree vision as well as full elevation for overhead vision. Better optics were a must, with a suggestion that the BuOrd “Battery Officer’s Sighting Glass” be combined with sighting for the improved .50 cal anti-aircraft batteries. If a stereoscopic device could not be mounted for ranging, a vertical mill scale could allow distances to objects be approximated. In addition to the request to up-gun to .50 cal was a detailed plan to train the ship’s company in their loading and firing, clearing jams and using the tracer trajectory to adjust the cone of fire. Each student was to receive 100 rounds per practice. The report also discussed possible ship evasive action, including zig zagging when in enemy contested territory, much as a surface ship hoping to evade submarine’s torpedoes.

Again it was recommended that a listening device that could be towed in the water at low speeds be developed for use against submarines. They noted this could be developed with a non-rigid, not realizing this had already been done in New England with a B-ship in 1919, which was then classified into obscurity.

EPSON MFP imageThe report urged more lessons should be learned from operations from expeditionary mast bases, and that recommended improvements in them be made in time to host the new rigid airship.

The Macon’s sub-cloud car was incompatible with airplane ops, so it was recommended to be moved to an independent location and stowed as part of the outer cover.  The report praised the concept and stated, “No military airship should be without this very essential appendage.” The tiny car would allow the airship to hide in the frequently encountered temperature inversion fog commonly occurring in the central and northern Pacific Ocean anywhere from the surface up to 3500 feet.

spy basketAdding a steerable rudder to the car was seen as allowing smaller drift angles to be detected while the ship was enveloped in fog. Putting the drift meter (above, this page) on the car would have allowed navigation with the airship completely obscured. (The occupant would align with the airship’s track, and the drift indicator rotated until objects on the surface pass through the drift indicator parallel to the wires. The drift is then read from the drift indicator direct.) Flares were to be carried for night use.

Macon’s plan to carry bombs with structure already reinforced around the heavy fuel tanks was to be implemented with the obvious refinement that bombing be directed from the sub-cloud car while the airship remained obscured. Recommended training was to include hitting targets up wind, down wind, and cross wind.

F-9 pairAs to the mission the ZRS ships grew into, that of flying carrier, the Macon’s trapeze and airplane handling was praised. It was noted three airplanes could be recovered and stowed within ten minutes. Experience with the perch, only four feet away from the ship’s fabric, offered the suggestion that the trapeze’s length might be shortened. (It would be 1937 before the Germans tried such a perch themselves, and it was not a success.) The report noted even average pilots were quite capable of learning the hook-on technique after a few cycles. Note was made of the difficulty of open-ocean navigation in the Sparrowhawk’s tiny cockpit, where even the compass had been moved out on the wing.

dsc02322-copyNot foreseeing a return to external storage, the report stated any interior airplane hangar should be closer to amidships for independence of ship trim when launching and recovering. Since the airplane’s engine should not have been started in the hangar bay, its warmup time once started in the slipstream slowed launch operations. Note was made that the next ship’s planes should have robust oil heaters to shorten the warmup times before launch, certainly a concern for external mounts.

Consensus concluded the proper use of the fighter aircraft as not to fly circles in a defensive ring, but rather to fan out ahead and abeam to observe potential enemies and report back to the ship, which could then take evasive action.  Since recoveries and re-launches could not always be staggered, a second trapeze and fuel-equipped perch stations were seen as a must. Co-ordination of the aircraft called for a flat-top’s “Air Boss” but leadership disagreed. Eventually such duties were included in the role of the Tactical Officer.

dsc00774Late in Macon’s life, officers were considering testing the flying carrier’s role for more than just scouting. They wrote, “Suppose the airship scout should discover an enemy carrier several days before the enemy expects to make contact with our forces. The surprise element and the probable damage which could be done to the planes on deck by a dive bombing attack delivered by the airship’s planes would be of tremendous value. Such a use of the airship-based planes must not be overlooked in the design of new aircraft.”  A maneuver as described above was planned for rehearsal by the Macon planes, but the loss of the ship prevented its execution.

If follows, therefore, that as the new, additional strike mission was forming in airshipmen’s minds, senior leadership would also be hesitant to embrace the revolutionary idea. Nonetheless, though it would still take a while, RADM King’s efforts bore fruit when the Navy’s General Board eventually stated: “If airplanes are carried by an airship the usefulness of both could be enhanced… With two or three times the speed of a surface cruiser, an airship carrying airplanes could advance the scouting line much more rapidly than would be possible by ships carrying aircraft… The conception of utilizing as carriers of airplanes has not been thoroughly explored, but it is the filed in which a naval airship’s greatest possibilities seem to lie. ”

At the same time, the larger question as to the value of the airship to the nation as a whole needed to be answered. SEC NAV commissioned a study by the leading aeronautic minds of the day. Here is the letter ordering the study:

February 18, 1935

To: Dr. Karl T. Compton, Chair, Science Advisory Board

Massachusetts Inst. of Tech., Cambridge, Massachusetts

Dear Mr. Chairman:

Reference is made to Executive Order No. 6238 (The White House, July 31, 1933). It is requested that the Science Advisory Board, under the authority conferred by the reference, appoint a suitable committee to review and analyze the past and present situation as to the design and construction of airships (dirigibles) and to make recommendations as to their future design and construction.

It is to be emphasized that the requested inquiry should be of the broadest scope relating to airships (dirigibles) in general, whether for military (naval) or commercial purposes. The usefulness of airships (dirigibles) for military (naval) purposes is entirely incidental to the general question and, in fact, a matter of other and separate consideration subsequent to the determination of the best design and construction.

Sincerely yours,

(s) Claude A. Swanson, SECNAV


RADM King, however, was not waiting for this so-called Durand Committee report to tell him what he already knew. King moved to expand the US Navy’s interface with the German passenger airship operations, which was just then seeking an agreement with the Americans for the use of American facilities at Lakehurst and Opa-Locka. For now, working with German airships was the only way Americans were going to continue to retain proficiency in rigid airship operations as they entered what has been called “the years of confusion.”

Read on to Durand Committee Reports


Read on to the US Navy and the DELAG


Read on to Tests of the “Years of Confusion”


Read on to Ground Handling Evolution

Purchase SNAFU: The Strange Story of the American Airship

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