29 November 2015

Delta Air Lines and the Boeing 747-100

On 9 September 2015, the very first Boeing 747-400 built, N661US, touched down at Atlanta from Honolulu as Delta Flight 836 for the last time in revenue passenger service. Ship 6301 was the Boeing 747-400 prototype which was then delivered to launch customer Northwest Airlines on 8 December 1989 and came over to Delta with the 2008 merger. There are twelve remaining 747-400s flying with Delta, all of which came over from Northwest. Current fleet planning will have these 747s retired in 2017. Delta did however, for a brief time, operate the first variant of the 747 family, the 747-100, from September 1970 to April 1977. Only five aircraft were taken on strength with Delta and while the 747-100 was but a short historical footnote in Delta’s history, its legacy looms large to this day with the airline.

My own profile art of Delta’s first 747-100, N9896 “Ship 101” as it looked on her delivery in 1970.
(JP Santiago)

In order to understand what the 747 was for Delta at the time, one has to consider that as the 1960s were drawing to a close, Delta was in the midst of transition on several fronts. The first change change came with the Southern Transcontinental Route Case of 1961. Prior to deregulation, airlines often had to make a case for the opening of new services and routes to the Civil Aeronautics Board. Often these cases consisted of years of deliberation and often politics played a central role in airlines winning favorable rulings from the CAB. In the 1950s, the CAB favored interchange services as a means for airlines to open up new markets without saturating a given route with an excess of seats, harming profitability. Having a predominantly Southeastern US-anchored network, Delta linked up with several other airlines to offer interchange services which allowed it to fly as far west as California. As traffic grew on the interchange services to the West Coast, Delta petitioned the CAB to operate the West Coast services on its own and in one of the more historic decisions made by the CAB, both Delta and National were given route authorities to California from the southeast in what was called the Southern Transcontinental Route Case. Starting in 1961, the previous interchange agreements were declared redundant and Delta opened up a range of nonstop services to San Diego, Los Angeles, and San Francisco from Atlanta, Dallas, and New Orleans. Within a year, Las Vegas was added as well as Miami which for the first time made Delta a transcontinental airline. By 1963, the CAB permitted Delta to carry West Coast traffic to its Caribbean destinations via New Orleans and onward to Florida (Orlando and Miami) via Atlanta. In an unrelated decision by the CAB, Delta was allowed to interchange on routes to London from Washington Dulles with Pan American and soon Delta’s DC-8s were flying to Europe as part of that interchange agreement.

The second and biggest of these changes came with the death of Delta’s founder, C.E. Woolman, on 11 September 1968. In his 1841 essay “Self-Reliance”, Ralph Waldo Emerson wrote that “An institution is the lengthened shadow of one man...all history resolves itself very easily into the biography of a few stout and earnest persons." From Delta’s founding in 1927 to his death in 1968, no other individual was so closely identified with Delta than C.E. Woolman. He became the airline’s president and general manager in 1945 and became its chairman of the board only a year before his death. Though viewed as a stern autocrat by the press, Woolman was beloved by Delta employees. On his 25th anniversary with Delta, the employees presented him with a new Cadillac and though he had own several other cars, he kept that Cadillac until he died. Though ably succeeded C.H. “Charlie” Dolson, W.T. “Tom” Bebe and David Garrett, there was no question it was still Woolman’s airline for years to come.

The last change that frames the selection and operation of the Boeing 747-100 by Delta was its 1972 merger with Northeast Airlines. Throughout its history, adversity plagued Northeast which always seemed be hobbled by the CAB with a small network and when Northeast finally did break out of New England in 1968 with new routes to Florida, it ran square into the crosshairs of Eastern which was the incumbent giant of the US East Coast at the time. With Northeast literally going from cash crisis to cash crisis, its New England route authorities soon proved to be ripe for acquisition via merger. The first suitor was Northwest Airlines in 1969. Interestingly, the CAB approved the merger in 1970 but it would be without some of Northeast’s more attractive route authorities like Miami-Los Angeles. Northwest withdrew its merger offer in 1971 as a result. Eastern and TWA then offered merger terms, with Eastern in particular seeing a merger as a way of knocking a competitor out of the New England-Florida market. Those negotiations also fell through and ultimately it was Delta that came through with a suitable merger offer that also met with the approval of the CAB. On 19 May 1972, President Richard Nixon signed off on the Delta-Northeast merger (since foreign routes were involved).

So these are three events in which to put the context of the Delta’s order of the Boeing 747-100- the Southern Transcontinental Route Case of 1961, C.E. Woolman’s death in 1968, and the merger with Northeast Airlines in 1972.

Prior to the launch of the Boeing 747, the “big jet” of the day were the Douglas Super Sixty series DC-8s which had surpassed the Boeing 707 in utility and passenger capacity. While the 747’s launch has been historically associated with Juan Trippe and Pan Am, at the time, Boeing was keen on getting one up on Douglas and the 747 was the aircraft that would capture the “jumbo” jet title from the DC-8 Super 61/63. Delta representatives had visited Boeing to view the progress on the 747 program and were suitably impressed with the aircraft. Despite their favorable views on the 747 though, it was clear to all of Delta’s management from the outset that the 747 was too much airplane for the airline which had a predominantly short- and medium-haul route network with its longer routes suitably (not to mention cost-effectively) served by the DC-8 fleet. On the other hand, two of Delta’s biggest competitors, Northwest and American, had already placed orders for the 747. Delta’s fellow “southern transcontinental route” airline, National, was also expected to place orders for the 747 as well. The writing was on the wall- Delta’s DC-8s were no match for the expected spacious comfort of the big Boeing and the prudent move was to get the 747 as well, even if was just a small number on a temporary basis. In April 1967, Charlie Dolson, the airline president of the time, announced Delta’s order for three 747-100s for $20 million each with options for two more aircraft. It marked the very first time that Delta had ordered from Boeing. Preparations were made at six Delta destinations and three alternate cities for operation of the massive jet. When Pan American launched the world’s first 747 passenger services in January 1970, Delta had two representatives aboard the inaugural passenger flight.

Delta marketed the upper deck lounge of its 747s as the “Private Penthouse”.
(JP Santiago)

While Delta was making preparations for the arrival of the 747, it was carefully considering its future widebody needs which were better met by a smaller aircraft in the form of either the Douglas DC-10 or the Lockheed L-1011. Delta’s technical staff liked both aircraft and it was believed the DC-10 was favored given Delta’s long association with Douglas Aircraft and its extensive use of both the DC-8 and DC-9 in the 1960s. Delta’s close association with Douglas as one of its most loyal customers was the product of a friendship between C.E. Woolman and Donald Douglas. In the 1960s, Douglas encountered repeated financial and technical difficulties with both the DC-8 and DC-9 programs that resulted in financial losses that led to its merger with McDonnell Aircraft in 1967 which effectively put Donald Douglas out of the executive suite. And keep in mind it was the following year that C.E. Woolman passed away. In a sense, Delta was now a “free agent” no longer tied to Douglas. Lockheed, eager to put its reputation back on good standing after the issues with the Lockheed L-188 Electra, pulled out all the stops in the Tristar program, engaging potential airline customers aggressively and early on in the Tristar development, resulting in an aircraft that at least in Delta’s eyes, was practically custom-built for them. Delta did, however, order five DC-10 Series 10s as insurance against the Tristar program when Rolls Royce ran into serious financial trouble during the development of the RB.211 engine used on the Tristar.

Delta’s 747-100 order was fulfilled quickly with N9896 being handed over to Delta on 25 September 1970 with the aircraft arriving in Atlanta to great fanfare on 2 October 1970. N9897 was delivered on 25 October 1970 and N9898 was delivered on 18 November 1970. While Pan American was first to launch 747 services on 22 January 1970 on its New York JFK-London Heathrow route, mostly domestic 747 services were launched in quick succession that year:

25 February: Trans World Airlines, New York JFK-Los Angeles (first domestic 747 service)
2 March: American Airlines, New York JFK-Los Angeles
26 June: Continental Airlines, Chicago-Los Angeles-Honolulu
1 July: Northwest Airlines, Chicago-Seattle-Tokyo
23 July: United Airlines, New York JFK-San Francisco
25 October: National Airlines, Miami-New York, Miami-Los Angeles
25 October: Delta Airlines, Atlanta-Dallas-Los Angeles
21 December: Eastern Airlines, New York JFK-Miami
15 January 1971: Braniff International, Dallas Love Field-Honolulu

By the end of 1970, Delta put the other two 747-100s into service with flights to Chicago, Detroit, and Miami. The options for the two aircraft were exercised the following year with N9899 being delivered to Delta on 30 September 1971 and N9900 arriving on 11 November 1971. While Delta’s 747-100s flew amongst Atlanta, Dallas, Los Angeles, Chicago, Detroit and Miami, they were also put to use on the Pan Am interchange services between Washington Dulles and London Heathrow. In the space of just over ten years, Delta went from a mostly regional airline anchored in the southeastern United States with some Caribbean routes to a transcontinental airline operating the Boeing 747 with limited interchange services to London. Never before in Delta’s prior history had it grown so much. But its fleet was quite diverse as a result of the merger of Northeast Airlines- it had twelve different aircraft with eight different engine types in service- in August 1972, Delta had three variants of the Douglas DC-8 in service, three variants of the Douglas DC-9, two variants of the Boeing 727, the Boeing 747-100, the Convair CV-880, the Fairchild-Hiller FH-227, the Lockheed L-100 Hercules for its cargo division, and it was anticipating the arrival of both the Lockheed L-1011 Tristar and the Douglas DC-10! In the interests of reducing the maintenance costs, standardizing operations, and holding down spare parts inventories, the fleet types had to be pared down. By this point, David Garrett had become president of the airline and it was his legacy that Delta streamlined its fleet which gave it record breaking profits in the late 1970s. Garrett’s primary imperative was fuel savings- the 1973 OPEC oil embargo that followed the Yom Kippur War in the Middle East caused a sharp spike in the cost of fuel.
The Pratt & Whitney JT9D was the first production high bypass turbofan used on a production airliner.
(JP Santiago)

For smaller markets and the short- to medium-haul flying, Delta standardized on the Douglas DC-9 Series 32. For medium-sized markets and medium-haul flying, Delta standardized on the Boeing 727-200. It had acquired them via its merger with Northeast Airlines and found them to have superior economics to the Convair CV-880s and to some degree even the DC-8s. In addition, the 727-200 used similar Pratt & Whitney JT8D engines as the DC-9. There were thirteen 727-200s that came over with the merger with Northeast and Delta wanted more- in March 1972, Delta returned to Boeing once again, this time with an order for fourteen 727-200s (the order was placed before final approval of the Northeast merger by President Nixon)- Boeing even took Delta’s remaining Convairs as a trade-ins on the 727 order. By 1977, there would be 88 727-200s in Delta’s fleet. Delta’s first experience in working with Boeing on the 747-100 order was so favorable the airline was eager to work with Boeing quite readily again. The arrival of more 727-200s allowed Delta to dispose of the Convairs and the oldest DC-8s first. While most of the Series 51s and Super 61s were sold off, a sizeable number were kept on for several more years with some of the Super 61s getting the Cammacorp re-engining with the CFM56 to become Super 71s.

By this point it was clear the Lockheed L-1011 Tristar would be the long-haul workhorse of the Delta fleet. The DC-10s were eventually sold off to United. The first Tristar arrived in Atlanta on 12 October 1973 with the first passenger services on 15 December 1973 on the Atlanta-Philadelphia route. By 1974 there were ten Tristars in service but their spacious underfloor cargo holds meant they carried 25% of Delta’s cargo despite being less than 10% of the fleet. That allowed the L-100 Hercules transports to be sold off that year. When the Boeing 747-100 was ordered in 1967, it was with the understanding it was too big of an airplane for Delta but it was needed to compete in the marketplace. With the Tristar quickly proving itself, the 747-100’s days were quickly numbered and arrangements were made for the first two 747-100s to be sold off but the last three stayed on just a bit longer until more Tristars were in service. Delta’s last Boeing 747-100 service was flown 23 April 1977 Las Vegas-Atlanta.

Of the five original Delta 747-100s, only the first one, N9896 “Ship 101” can still be seen today at the Evergreen Aviation Museum.
(JP Santiago)

The fates of Delta’s five 747-100s:

N9896: Returned to Boeing 1974, leased to China Airlines 1976-1978, operated by Pan Am 1978-1991, then flew with Evergreen International. Preserved at the Evergreen Aviation Museum in 2010 (it’s on the roof as part of the waterpark with waterslides coming out of it!)

N9897: Returned to Boeing 1977, operated by Flying Tiger 1977-1989 (leased to El Al Israel for a year), operated by FedEx 1989-1991, operated by Air Hong Kong 1991-1996, then Polar Air Cargo, now scrapped.

N9898: Returned to Boeing 1975, operated by China Airlines 1975-1976, leased out by Guiness Peat Aviation 1976-1984, operated by Pan Am 1984-1991, operated by Evergreen International starting in 1991 and converted to a water bomber “Evergreen Supertanker”, retired with Evergreen’s bankruptcy in 2013. In storage at Pinal Air Park.

N9899: Returned to Boeing 1977, operated by Flying Tiger 1977-1989 (leased to El Al Israel for a year), operated by FedEx 1989-1991, operated by Air Hong Kong 1991-1995, then Polar Air Cargo, now scrapped.

N9900: Returned to Boeing 1977, operated by Flying Tiger 1977-1989, operated by FedEx 1989-1993, operated by Air Hong Kong 1993-1994, operated by Kalitta 1994-2008. Stored at Oscoda, then scrapped 2015.

As an interesting historical footnote, the first officer on the delivery of Delta’s first Lockheed Tristar was Captain Jack McMahan who at the time was one of only two men in the United States certificated to fly the DC-10, L-1011 and 747. The other pilot was an FAA examiner. He was asked by a reporter on his impressions of all three widebodies- he praised the handling of the DC-10, the overall design of the 747, and the advanced systems of the L-1011. He remarked “Flying the three planes is like going out with three sisters. They have the same background but different personalities!

This article was originally posted on AirlineReporter.com on 23 October 2015.

Sources: Delta: The History of an Airline by W. David Lewis and Wesley Phillips Newton. University of Georgia Press, 1979, pp 340-392. Delta: An Airline and Its Aircraft by R.E.G. Davies. Palawdr Press, 1990, pp 76,80-86,96-97. 

24 November 2015

The Most Decorated Flight Crew in Vietnam: The Story of Cherry Six

The most northerly air base in South Vietnam during the Vietnam War was Da Nang Air Base which was located only 85 miles south of the demilitarized zone (17th Parallel) that demarcated North and South Vietnam. Once a limited airfield inherited from the French, it wasn't until the early 1960s that the South Vietnamese expanded Da Nang into a modern military air base. The first US advisors with the Military Assistance Advisory Group (MAAG) arrived in 1961. Over the next three years as the US military presence ballooned, Da Nang AB became a vital base for close air support for the US Marine Corps operating in I Corps, the military operating area just south of the DMZ that was centered on Da Nang. With it became necessary to increase the USMC aviation presence in I Corps, Da Nang AB was practically over capacity and a second air base had to be built in 1965 about 56 miles to the southeast of Da Nang at a location called Chu Lai. Elements of Marine Air Group 12 (MAG-12) were based at Chu Lai, including Marine Observation Squadron 6 (VMO-6) and their Bell UH-1E Iroquois "Huey" helicopters. During the Korean War, VMO-6 was the first Marine Corps helicopter squadron in history to enter combat, flying observation, reconnaissance, and escort missions at the Pusan Perimeter in 1950. VMO-6 had just converted to the Huey in 1964 and commenced operations at Chu Lai AB in September 1965.

Newly arrived Marine UH-1E ( Huey ) from VMO 6 at Chu Lai, Viet Nam; Sept. 1965
Marine UH-1Es looked like this 1965 example at Chu Lai. By 1967, the yellow warning stripe was removed as well as the US insignia with "Marines" titles in black to reduce their visibility in combat.

It would be a four-man UH-1E flight crew from VMO-6 in 1967 that would become the most decorated flight crew of the Vietnam War. On 19 August 1967, an Army Boeing/Vertol CH-47 Chinook was enroute to Chu Lai AB with a load of injured soldiers. Twenty miles out, the Chinook came under heavy small arms fire from Viet Cong in the area. They set down on a beach where the the Song Tra Khuc River empties into the South China Sea to assess the damage. While several of the crew were outside of the helicopter examining the damage, Viet Cong troops in the area laying in wait opened fire on the helicopter. In a rush, the pilot took off, leaving four crewmen behind on the beach. He radioed immediately on the emergency guard channel that his aircraft was all shot up and he was trying to make for a safer location adding "I still have four men on the ground, the VC are trying to take them prisoner or kill them; God, can somebody help them?"

Captain Stephen Pless was flying an armed UH-1E with the callsign CHERRY SIX on a medevac escort mission when he received the transmission of Americans in immediate danger. Pless discussed the radio call with his copilot, Captain Rupert Fairfield and Pless decided their original mission, escorting the medevac of a single injured Korean Marine, didn't need their escort services and they flew to the location of the trapped men on the beach. Overflying the area, Pless noted that the trapped men were under heavy machine gun and mortar fire. Seeing three jets overhead as well as four Army Hueys orbiting offshore, Pless noted they were all reluctant to move in on account of the heavy fire coming from the VC advancing on the beach. He then asked his crew "How do you feel about going in?" getting a thumbs up from Captain Fairfield and his two crew chiefs, Gunnery Sergeant Leroy Paulson and Lance Corporal John Phelps. 

Stephen Pless was no ordinary Marine officer. He joined the officer corps from the enlisted ranks but he still had great affection for his enlisted men. He frequently socialized with the Marine enlisted at Chu Lai and it's said he spent more time in the enlisted quarters at the base than the officers' quarters. He had several hundred missions under his belt already and some of the Marine crew chiefs had flown secret missions with him into Laos. Pless knew his men would follow him down to that beach with no hesitation and anyone would have done it with Pless as their commanding officer. 

On their initial approach to the trapped men, the first elements of the VC force of about 40 to 50 men were already upon the men, disarming them and hitting them while the rest of the VC moved out from the treeline onto the beach. Since the VC soldiers were too close to use their rockets, Gunnery Sergeant Paulson opened up with M60 machine gun, scattering the VC soldiers. As they ran back for the safety of the treeline, Pless fired white phosphorus-tipped rockets into the mass of fleeing VC. Wheeling the Huey around for several passes, Pless fired more rockets as well his side mounted guns into the treeline, taking heavy small arms fire in the process. On most of his attacks he was less than 50 feet above the ground, in some cases so low that mud thrown up from his own weapons splattered the Huey's windshield. With his rockets nearly expended, Pless then landed his Huey near the trapped men, facing the ocean using his helicopter as a shield between the VC and the trapped men. 

Emblem of VMO-6 "Tomcats"
As several VC tried to approach the helicopter, Lance Corporal Phelps fired his M60 from the left side while Gunnery Sergeant Paulson jumped out and ran to the trapped men- he was able to get the first man aboard as he was still able to walk and Paulson then ran back to the next man while under heavy fire. Captain Fairfield then exited the cockpit to help Paulson with the second man. As he jumped out, Fairfield saw three VC only 10 feet away. He quickly unhooked one of the M60 machine guns and killed all three with a short burst. He then ran to Paulson to help get the second man aboard while Lance Corporal Phelps provided cover fie with his M60. Getting the second man aboard, Fairfield and Paulson then ran for the third man, but he was heavier than the other two- Phelps gave his M60 to the first injured man, Staff Sergeant Lawrence Allen, who was propped up against the back of Pless's seat. He cradled the M60 with his injured arm and continued providing suppressive fire with his good arm. With Fairfield, Paulson, and Phelps carrying the third man to the Huey, a single VC with a hand grenade approached. Phelps dispatched that soldier from ten to fifteen feet away with six shots from his service pistol. Fairfield and Paulson also fired their service pistols as well as they carried the third man to the helicopter. 

With the third man aboard, Fairfield and Paulson ran back for the fourth man but he was already dead. As they jumped back into the Huey, Pless began to takeoff but the three extra men made his helicopter significantly overweight. With the only reasonable avenue of departure being over the ocean as the VC small arms fire intensified, Pless bounced off the waves repeatedly until the helicopter had enough airspeed to climb away from danger. He then had the crew jettison or throw overboard anything that wasn't needed to get to Chu Lai only 20 miles away. Enroute, Paulson and Phelps rendered medical aid to the three injured men. 

Unbeknowst to the crew of CHERRY SIX, one of the Army Hueys Pless observed orbiting offshore made a run in to provide additional covering fire. Flown by Warrant Officer Ronald Redeker, he made multiple strafing runs with his door gunners until their ammunition was exhausted. 

The flight crew of CHERRY SIX: (L-R) Phelps, Pless, Fairfield, and Paulson
(Defense Department/Valor Remembered)
Seven days later, the commanding officer of VMO-6 wrote a letter that passed up through the chain of command to the Secretary of the Navy recommending Captain Stephen Pless for the Congressional Medal of Honor. In the same letter he also recommended Captain Fairfield, Gunnery Sergeant Leroy Paulson, and Lance Corporal John Phelps for the Navy Cross, the second highest award from bravery after the Medal of Honor. The awards were all approved- not only making Captain Stephen Pless the only Marine Corps aviator to earn the Medal of Honor in Vietnam, but also making the entire crew of CHERRY SIX the most decorated flight crew of the Vietnam War. 

Sources: Marine Air: The History of the Flying Leathernecks in Words and Photos by Robert F. Dorr. Penguin Books, 2007. Assault from the Sky: US Marine Corps Helicopter Operations in Vietnam by Dick Camp. Casemate Books, 2013.

19 November 2015

C.E. Woolman and the Founding of Delta Air Lines

C.E. Woolman (Minnesota Public Radio)
Collett Everman Woolman was born in Indiana in 1889 and was raised in the academic environment of Champaign-Urbana, Illinois, where his father taught physics at the University of Illinois. Woolman's interest in aviation began at an early age when he and his friends appropriated every clothesline in his neighborhood to build a giant passenger-carrying kite which fortunately for history, crashed before anyone tried to take flight in it. As a freshman, he even built a crude airplane which had to make a forced landing on his university campus. In his sophomore year of collge at the University of Illinois, he learned of the first aviation world meet to be held in Reims, France, and the ambitious Woolman managed to get a job tending a herd of 800 travelling calves to get to France. On his return, he helped pioneer aviator Claude Grahame-White overhaul a rotary engine in the passenger steamer's cargo hold in preparation for an airshow in Boston. 

He graduated in 1912 from the University of Illinois with a bachelor's degree in agriculture. That's right, farming. The legendary founder and head of Delta Airlines studied agriculture in college, hardly the field to propel him into aviation, but in those days, aviation as a business and industry hardly existed and was more the realm of half-cocked mad scientist types to be shunned by the general population. In fact, if you wanted to look up Glenn Martin's aircraft company in Los Angeles in those days in the phone book, it was listed under "Amusements"! With a fresh degree in agriculture, Woolman moved south to farm various locales in Mississippi before becoming the manager of a 7000 acre plantation in northern Louisiana. 

In 1913 he joined the extension department of Louisiana State University at Baton Rouge as an agricultural sciences instructor who travelled out to farmers to pass on the latest techniques. In 1914 the US Congress passed the Smith-Lever Act which formalized the extension cooperative system in which universities would reach out to farmers to formally educate them on the latest developments in agriculture. With this new law, the young C.E. Woolman became LSU's first extension agent in Lousiana and based his operation in Monroe, Louisiana. 

Travelling throughout Louisiana, he not only met with farmers and plantation owners but also consulted with financial institutions on investing in agriculture as well as liasing with the agricultural scientists back at the LSU campus. It was during this time that the boll weevil infestation was ravaging the US cotton crop. A chemical had been developed which was effective against the boll weevil; calcium arsenate was a dry powder which worked well, but was cumbersome and inefficient when applied from the ground. 

The federal government had experimented with US Army planes in rudimentary crop dusting efforts, but a grant was given to an entomologist by the name of Dr. Bert Coad at the US Department of Agriculture's Delta Laboratory in Tallulah, Louisiana. Coad had difficulty finding an airplane that possessed a good load carrying capacity to carry enough calcium arsenate powder to dust an entire cotton field. Coad hooked up with a small company called Huff-Daland which was trying to market a military training biplane. Struggling for cash, Huff-Daland eagerly cooperated with Bert Coad in his crop dusting trials.

Huff-Daland Duster at the National Air & Space Museum
(Smithsonian Air & Space Museum)
Given Woolman's job with LSU's agricultural extension, he observed many of Coad's trials with interest. Encouraged by Woolman's favorable assessments of the effectiveness of aerial crop dusting against the boll weevil, Coad tried to get more federal grant money to expand the enterprise. Woolman had enthusiastically spread the word to area farmers that there was a new weapon against the boll weevil and soon Coad found he didn't have the resources to meet the demand. But the US Department of Agriculture saw Coad's trials as only an experiment and failed to provide more resources. 

In 1923, the vice president of Huff-Daland happend to stop by Tallulah, Louisiana, on his way to Texas to demonstrate a Huff-Daland trainer to the US Army. There he ran into Coad and Woolman at the airport and found their work intriguing and thought it would make for a great commercial opportunity with the right amount of investment. He convinced Huff-Daland to set up a crop dusting division in northern Louisiana and he put Coad in charge. But Coad wasn't the best of salesmen and he asked Huff-Daland to hire C.E. Woolman as it's head of sales. Huff-Daland Dusters was originally based in Macon, Georgia, with the bulk of their original business being the spraying of peach orchards. However, by 1925 the company moved to Monroe, Louisiana, with the promise of local investment that Woodman had secured. Coad's former laboratory in Tallulah was close by and Woolman's work with the farmers there brought them a ready-made clientele. Woolman, in that classic Southern genteel style he would become famous for, convinced local business leaders in Monroe to invest in Huff-Daland Dusting Company and by the mid 1920s, Woolman had expanded the dusting operation to include Texas, Arakansas, California, North Carolina and even a contract to do crop dusting for the Peruvian government. In a few short years, Huff Daland Dusters would have one of the largest private fleets of aircraft in the United States, even more than some of the airlines of the day.

Delta's first logo (Delta Flight Museum)
Within a few years, Woolman himself would buy the entire dusting operation from Huff-Daland while Huff-Daland Aircraft itself moved to Pennsylvania and was renamed Keystone Aircraft, one of the pioneering aircraft companies of the day. Woodman wanted a simple name preferably with five letters and it was his long time administrative assistant Catherine Fitzgerald, who suggested the name "Delta". Given its long time service area of the Mississippi Delta region, the name was perfect and the triangle was not too dissimilar to the Huff-Daland Dusting Company logo. One of Delta's first non-dusting contract came from the Army Corps of Engineers who wanted aerial surveys done of the levees along the Mississippi River after some disastrous floods in 1927. Woodman likely was considering starting an airline around that time, a federal airmail survey passed through Monroe and he had been looking at a proposed air mail route that connected Shreveport, Monroe, Jackson, Meridian, Tuscaloosa, and Birmingham. In 1929, he even went as far as got advice from a Minneapolis-based airline (Northwest) who offered him suggestions on operating a passenger-carrying airline. However, Delta's finances at the time weren't in a position to get the Ford or Fokker trimotor airliners used by the major airlines of the day. As luck would have it, in a small town not far from Monroe was a businessman named John Fox who had just started a local air service that concentrated on taking people up for joyrides in Travel Air biplanes. Fox had ordered a larger aircraft, a high-wing monoplane with a six-seat enclosed cabin Travel Air S6000. Fox and Woodman met in 1929 and hit it off well given their mutual aspirations of starting an airline. Delta purchased the assets of Fox Flying Service in exchange for Delta stock which made John Fox the biggest Delta shareholder. Fox was named an officer of the company by Woodman and moved to Monroe to help Woodman get their airline off the ground.  Delta Air Service carried its first passenger from Dallas, Texas, to Monroe, Louisiana in on 17 June 1929. Though Delta's agricultural operations would dominate for a while longer, it was a humble beginning for a Southern farmer and his airline.........

Historical Tangent: Thomas Huff and Elliot Daland started their company in 1920 as Ogdensburg Aeroway Company in 1920 in Ogdensburg, New York. They soon became the Huff Daland Aero Company and in 1924 their chief designer was James S. McDonnell (yes, *that* McDonnell that would go on to establish McDonnell Aircraft in St. Louis during the Second  World War). Thomas Huff sold his share of the company in 1926 and it was acquired by a securities firm who invested a significant amount in Huff Daland and moved the operation from New York to Bristol, Pennsylvania and renamed it Keystone Aircraft. Keystone merged with Loening Aircraft in 1928 and the following year Keystone-Loening was taken over by Curtiss Wright. The Loening plant on the East River in New York City was closed by Curtiss and operations transferred to Bristol. A handful of Loening workers and management, though, all New Yorkers, elected to stay and form their own company to stay in New York. The leader of the group was none other than Leroy Grumman. Yes, *that* Grumman!

Sources: Delta: The History of an Airline by W. David Lewis and Wesley Phillips Newton. University of Georgia Press, 1979, pp 1-24. Delta: An Airline and Its Aircraft by R.E.G. Davies. Palawdr Press, 1990, pp 8-13. 

14 November 2015

Refining Anti-Submarine Warfare: The Grumman AF Guardian

Grumman XTB3F Guardian prototype
(San Diego Air and Space Museum)
By 1944, the United States was already laying down plans for the invasion of Japan and if the stiff resistance in the island hopping campaign across the Pacific was any indication, the Japanese were far from defeated and planners expected the worst may yet to come. Navy torpedoes delivered by Grumman TBF Avengers were notoriously unreliable and required a relatively slow approach of 120 mph during their drops at low level. Navy torpedo research languished in the years before the Second World War and torpedo bomber crewman paid the price in their lives. Wartime urgencies caused a reinvestment of torpedo development by the Navy. New air-launched torpedoes in the works could be dropped at higher speeds and further stand-off distances from enemy warships, but by this point in the war, in order to take advantage of the new designs, something with twice the engine power of the venerable Avenger was needed. The first design Grumman submitted for a new carrier-borne torpedo bomber was for the large XTB2F. With two Pratt & Whitney R-2800 Double Wasp radials, the XTB2F was a big aircraft with a maximum takeoff weight of nearly 43,000 lbs which was 8,000 lbs heavier than the maximum takeoff weight of a late model B-25 Mitchell medium bomber! The XTB2F reached the mock up phase before the program was canceled in June 1944 as it was simply too large of an aircraft for the Essex-class fleet carriers. 

The XTB2F mockup before the program cancelation
(Wikipedia/Grumman Archives)
Under the G-70 in-house designation, Grumman offered several variations of a new single-engined design, some of which were mixed-propulsion designs with a big radial engine (either the Wright R-3350 or the Pratt & Whitney R-4360) and a jet engine in the rear fuselage for extra speed on the target runs. When it became clear the R-3350 and R-4360 radials wouldn't be ready for the planned production schedules for what was designated the XTB3F, the Navy asked Grumman for a redesign with the more widely available Pratt & Whitney R-2800 engine which was the same engine used on the B-26 Marauder and P-61 Black Widow. A Westinghouse J30 would be installed in the rear fuselage- the J30 was the first all-American jet engine to run and was only the second production axial-flow engine in the world after the German Junkers Jumo 004. Using the R-2800 engine only cost the reconfigured XTB3F 30 mph of speed which was acceptable to the Navy. Despite the ending of the war by this point, the Navy still wanted the XTB3F, now named Guardian, as a replacement for the Avenger and on 23 December 1946, the prototype aircraft made its first flight. 

As designed, the J30 turbojet in the rear fuselage of the aircraft had 1,330 lbs of thrust and was fed by air intakes in the leading edge wing roots that fed ducts that ran to the engine. During ground test runs, the intake ducting wasn't big enough and strong enough to handle the mass flow to the J30 and would collapse. The engine was only run on ground tests and never used during the flight test program. Ultimately the intake duct problems resulted in the engine being removed and would be absent from the production Guardians. 

With a spacious weapons bay for the Navy's latest torpedoes, the Guardian also had two 20mm cannons in each wing as well as provisions for underwing bomb racks and rocket launchers. Most remarkable about the Guardian, though, was its size. It was the largest single engined piston aircraft to be operated from an aircraft carrier and was 2/3 the size of a Douglas DC-3. In fact, its production maximum take off weight was nearly that of a DC-3! The big R-2800 radial up front was canted down slightly to improve pilot visibility in the carrier approach pattern and it was also canted 3 degrees to the right to help offset the torque of the big engine. It's large tail was to help its stability in low altitude regimes but it did make the Guardian difficult to handle in a crosswind. 

AF-2S and AF-2W hunter/killer team
(San Diego Air and Space Museum)
On the day following the Guardian's maiden flight, the Navy imposed a stop-order on the program to give funding priority to the Douglas AD Skyraider and Martin AM Mauler programs which were also capable of dropping torpedoes and as optimized attack aircraft, were more flexible than the Guardian not to mention smaller in size. It might have been end of the Guardian had it not been for the rapid postwar expansion of the Soviet Union's submarine force. Navy carrier forces needed a specialized anti-submarine aircraft and the XTB3F Guardian best fit that need. As a result, in January 1947, the Navy redesignated the Guardian as the AF (this would be a whole topic for a complete article on how the Navy consolidated the scout, bomber and torpedo roles in the new "A for Attack" designator). Given the state of the art of anti-submarine warfare of the time, though, a single AF Guardian couldn't carry both the necessary detection equipment and weapons, so the Navy brought back the hunter-killer team concept that had worked well during the Battle of the Atlantic were Avengers hunted U-boats and were assisted in their attacks by F4F/FM-2 Wildcats. One Guardian would be equipped with the AN/APS-20 radar in a large under fuselage radome and this would be the AF-2W "hunter". The other Guardian of the pair would be the AF-2S "killer". In operational service, the AF-2W was nicknamed "Guppy" while the AF-2S was nicknamed "Scrapper". 

Interestingly the AN/APS-20 radar started out as a crash program to give the Navy its first airborne early warning aircraft to warn of incoming Kamikaze attacks. Fitted to an Avenger designated the TBF-3W under Project Cadillac, the first AEW Avengers were in Hawaii conducting carrier qualifications when the war ended in 1945. The radome and radar installation on the Guardian was for all intents and purposes, pretty much just moved over from the TBF-3W to the AF-2W. With the J30 engine and its intake ducting gone, space was available for the radar and electronics on the AF-2W and more fuel on the AF-2S. 

Production was launched in October 1947 with an order for 23 early examples which would be devoted to operational testing as well as further flight testing. The first operational examples were delivered to the fleet in September 1950 with VS-24 being the first ASW squadron to get their Guardians. The first carrier qualifications took place that November and in December 1950, VS-24 embarked on the USS Palau (CVE-122) on the Guardian's first operational cruise. Now imagine an aircraft as heavy as a DC-3 that's just 2/3 the size of a DC-3 operating off the decks of escort carriers like the Palau! While a tough and reliable aircraft, a significant number of AF Guardians were involved in deck accidents. Most deck crews were used to handing aircraft half the size of the Guardian and one ASW squadron commander got so frustrated at the incidence of handling accidents just moving the Guardian on the carrier that he required a pilot to be present and in the cockpit if needed when an AF was being moved, even if it was just in the hangar deck!

Operationally, the AF hunter/killer team would form a protective ASW screen around the carrier battle group with the idea to detect and attack any submarines as far away from the carrier as possible. During the Second World War, the protective ASW screen was handled primarily by destroyers and destroyer-escorts- with the arrival of the Guardian, aircraft could now provide the ASW screen for the task force. Guardian teams would fly up to 500 miles out from the carrier with the AF-2W "Guppy" flying a search pattern using its radar to either detect a surfaced sub or a snorkel. Once detected, the "Guppy" would summon the AF-2S "Scrapper". Once in the area, the AF-2S had it's own pod-mounted radar under the right wing (and a search light under the left wing if it was needed at night) to prosecute the attack using vectors from the "Guppy". A periscope sight aft of the wings in the belly was used to release depth charges. If needed, the "Scrapper" could come back around and use rockets and bombs to finish the job. Late model Guardian "Scrappers" designated AF-3S were fitted with magnetic anomaly detection (MAD) gear to improve the chances of note just detecting a sub but sinking it. 

A total of 386 Guardians were built and from 1945 to 1954, it was the US Navy's premier front-line carrier-based ASW aircraft. Of that nine year span, only three of those years was the Guardian truly operational as part of anti-submarine squadrons at sea. Its replacement, also from Grumman, the S2F Tracker, would combine the hunter and killer roles in the same aircraft and the design of the Tracker was heavily influenced by the canceled XTB2F, the design that was replaced by the AF Guardian. Of all the Guardians built, five survived and were used by Aero Union as 800-gallon capacity water/retardant bombers against forest fires from 1957 to 1974. That final year the US Forestry Service instructed its water bomber operators that single engined aircraft could no longer be used. Most were scrapped but a single Guardian was saved and restored to its original configuration and is now on display at the Naval Aviation Museum in Pensacola, the last of its breed in existence. 

Sources: Ironworks: The Story of Grumman and Its Aircraft by Terry Treadwell. Tempos Publishing, 2000, p150-154. "Grumman's Guardian" by Budd Davison. Flight Journal, September 2011.

08 November 2015

Arthur Young Gets Bell into the Helicopter Business

Lawrence Bell, founder of Bell Aircraft
(Airport Journals.com)
In his book The Bell Helicopter Textron Story, David Brown says of Larry Bell, the founder of Bell Aircraft, "Larry Bell was different. With the visionary's eye, he saw his first helicopter and was impressed. When he saw his second (helicopter), he understood that here was an industry waiting to be born." Larry Bell was one of the early American aviation pioneers- after high school he worked as his older brother Grover's mechanic for several years while his brother conducted barnstorming flights. In 1913, his brother was fatally injured in a crash and Bell resolved to stay away from aviation. It wouldn't last, though. He first went to work for his brother's flight instructor, Glenn L. Martin, as a stockroom clerk in Martin's fledgling aviation company. He advanced quickly through the company and ultimately ended up as the Martin Aircraft vice-president and general manager. It was Bell who hired the first college-educated aeronautical engineer for the company- a young MIT graduate named Donald Douglas. It was Bell who got the Army interested in a heavy bomber called the Martin MB-2 that was one of Douglas' early projects. And it was Bell who convinced a brash Army aviator named Billy Mitchell to use the MB-2 to prove that bombers could sink battleships. In 1925, Bell asked to own stock in Martin but Glenn Martin rebuffed his offer of part ownership of the company. Bell resigned and within three years was hired by Rueben Fleet, the president of Consolidated Aircraft. Fleet allowed Bell to own a sizable portion of Consolidated shares and by 1929 he was promoted by Fleet to be the general manager of Consolidated. In 1935, Fleet wanted to move Consolidated from Buffalo, New York, to southern California to take advantage of the better flying weather. Bell didn't want to move, so he resigned but a group of investors backed him in purchasing Consolidated's facilities in Buffalo for the new Bell Aircraft Company. Interestingly, Bell was the third tenant of the factory- it was originally built in 1916 for Glenn Curtiss and at the time was considered the largest aircraft factory in the world. 

Bell's first aircraft was the YFM-1 Airacuda (Bell Model 1) which was a heavy bomber destroyer twin engined fighter. Only thirteen of the unique pusher twins were built and only a single squadron of Airacudas was activated as it was an aircraft ahead of its time. But the US Army Air Corps liked Bell's innovative thinking and asked him for a heavily-armed single engined fighter and this became the Bell Model 12, better known as the P-39 Airacobra which first flew in 1938. It was a remarkable start for Bell's fledgling company and in 1938, President Franklin D. Roosevelt asked Bell to join a group of American industrialists who had been invited tour Nazi Germany. Roosevelt wanted an expert opinion of Germany industrial capacity from the group and Bell was asked to join to assess the Nazi's aviation capabilities. Bell witnessed a flight demonstration of the Focke-Wulf Fw 61 helicopter flown by Hanna Reitsch and he considered the most impressive thing he'd seen on his tour of Germany. 

That was the first helicopter Larry Bell saw- to get to the second helicopter he saw in 1941, we have to step back a bit to look at the story of a unique inventor named Arthur Young. A native of Pennsylvania, while a student at Princeton University, Young was very interested in philosophy and tried to develop an original line of philosophical thought but was unsuccessful. He decided that he wouldn't be able to do so without some real-world experience solving problems. Graduating from Princeton in 1927 with a mathematics degree, Young searched for a technical challenge. He scoured city libraries in the East Coast and made regular visits to the US Patent Office in Washington in his search. He came across a book in his searches by German helicopter pioneer Anton Flettner who had invented a ship that used the Magnus effect from rotary drums to sail across the Atlantic. Flettner had described improving windmill efficiency by using small propellers at the tips. Young thought Flettner's concept could be applied to aircraft and of course that aircraft would be the helicopter, one of the unique flying machines of the day. He set himself on the task of developing a successful helicopter. 

Arthur Young and one of his late helicopter models
(State Archives of Florida, Steinmetz Collection)
Young set up an experimental workshop in a barn on his wealthy family's large estate in Pennsylvania. He refined his ideas using small models and his first design flew in 1931 using parts he obtained from a local toy shop- using rubber bands, hand-carved wooden blades with propellers at the tips and a balsa structure, his first model had a rotor diameter of six feet and it flew for only ten seconds. For the next nine years he worked at improving the Flettner concept, moving to the use of electric motors. He went through so many crashed models he literally learned how to mass produce his own helicopter blades. One of the problems Young encountered was getting his models into a stable hover. Over time he used his mathematics background to calculate stresses and build his own components based on his stress calculations. In doing so, he developed many of the concepts and tools used to measure rotor lift, propeller efficiency as well as equations to calculate a variety of power requirements for helicopters. 

In 1938, Young attended a conference of helicopter designers and learned of the pioneering work of Igor Sikorsky. Sikorsky himself gave a lecture on the use of a tail rotor to counter the torque of the main rotor. Young was fascinated by Sikorsky's lecture and set about to revise his model testbeds with tail rotors, disposing of the complex gearing that he had been working on to drive tip propellers. Stability in a hover continued to plague his efforts- he had tried a pendulum within the fuselage, but the pendulum arrangement he designed couldn't distinguish between the force of gravity and the force of acceleration. He then came up with the stabilizer bar- a bar with weights on the end that was perpendicular to the rotor. The weighted bar when spinning acted as a gyroscope that stabilized the helicopter in a hover. He used an electrical control system that ran to a box where he controlled the helicopter with extreme precision. He took his models on demonstrations to various aircraft companies where he showed how he could fly his helicopter models indoors and even in and out of doorways. He even gave a demonstration to the Army's aeronautical development center at Wright Field in Dayton, Ohio, but failed to find any financial backers. 

Dr. John Sharp was a physician who had seen one of Arthur Young's demonstrations. Sharp had a unique hobby in that he designed gearing systems in his free time and was working on a new gearing concept for a variable pitch propeller was pitching his ideas to Bell Aircraft. In 1941, Sharp was meeting with a Bell engineer named Jack Strickler and in casual conversation, Sharp spoke highly of Young's helicopter flight demonstrations. Strickler than passed on what Sharp told him to Larry Bell himself. Since Bell was impressed with what he had seen with the Focke-Wulf Fw 61 helicopter in his 1938 tour of Germany, he invited Arthur Young to come to Buffalo to give a demonstration of his helicopter design.

On 3 September 1941, Young arrived at Bell's Buffalo plant and was taken to a hangar where P-39s were prepared for delivery. Bell ordered the personnel in the hanger to stop work and move the P-39s outside to give Young room for his demonstration. Not only did Young fly a successful demonstration for Larry Bell, he also reviewed with Bell films showing his previous design efforts and showed him his notes on the design process he had developed to solve the problems of vertical flight. Bell was enthralled by Arthur Young and wanted to hear Young's ideas on a full-size piloted helicopter design. In a matter of weeks they reached an agreement where Young would come to Buffalo and work for Bell in developing a new helicopter based on his designs. Young assigned his patents to Bell Aircraft and Larry Bell funded the development of two full-sized helicopters. Young wanted two aircraft in case one crashed and Bell insisted that the second prototype be a two-seater so he could go on a ride! 

The rest, as they say, was history! That first helicopter, the Bell Model 30, will be the subject of a future article here at Tails Through Time. Stay tuned!

BONUS: A three part interview with Arthur Young in his later years about his design efforts

Sources: The Bell Helicopter Textron Story: Changing the Way the World Flies by David A. Brown. Aerofax Publications, 1995, pp 1-19. "Arthur Young: Maker of Bell, Part 1" by Robert Tipton, http://www.arthuryoung.com/maker1.html. 

03 November 2015

Regulus: The US Navy's First Operational Nuclear Missile

Regulus missile on an aircraft carrier deck.
Following the defeat of Germany in May 1945, the US Navy began experimentation with the German V-1 "buzz bomb" as a submarine-launched weapon called the JB-2 Loon. Both the Navy as well as the Army drew up plans to use the JB-2 during the planned invasion of the Japanese Home Islands, but the war in the Pacific ended in August of that year before the plans could be put into place for use of the Loon. This didn't put a stop to development work, though- in March 1946, Secretary of the Navy James Forrestal approved plans to convert two submarines to operate the Loon on an experimental basis. While the Loon was never planned in the postwar period to be an operational missile, it was planned to give the submarine force experience in operating cruise missiles. In 1947 the Navy began development of several supersonic land-attack cruise missiles- one was the Mach 2 Rigel and the other was the Mach 3.5 Triton, both powered by ramjets. At the time, ballistic missile technology was at a point where they weren't practical nor compact enough to be fired from submarines, so the Navy was hitching its submarine nuclear deterrent on the cruise missile. The level of technology required for the Rigel and Triton were far above what was state of the art for the late 1940s, so while development work continued and technology matured, an interim cruise missile for the sub force was needed and this task was given to Vought Aircraft who then developed the Regulus missile- originally planned to carry a 4,000 lb conventional warhead, in 1949 Vought was directed to use a nuclear warhead on the Regulus, making the first US Navy missile to carry a nuclear warhead. 

The Regulus featured folding wings and a tail fin to allow it to be carried aboard a submarine. Powered by an Allison J33 engine (also used on the Lockheed F-80 and T-33 Shooting Star), Regulus was a subsonic missile with an approximately 500 nautical mile range. It was boosted from the missile by two solid rocket boosters that fell away once the J33 engine took over propelling the missile. The missile guidance was by radio command- the system was called "Trounce" and it directed the missiles nearly all the way to the target. Not only were submarines and ships capable of guiding Regulus using Trounce, but the Navy also had specialized Regulus guidance squadrons equipped with the North American FJ Fury that could be embarked aboard fleet carriers as needed. The first Regulus flight took place on 29 March 1951- this early Regulus missile had its own landing gear to take off and land under its own power and was controlled from another aircraft. Test launches were made from surface ships the following year. 

Firing a Regulus from the USS Tunny.
Two diesel-electric submarines were the first to be converted to carry and fire the Regulus. The USS Tunny (SSG 282, the "G" for missile) and the USS Barbero (SSG 317) were fitted with a rather cumbersome hangar aft of the conning tower which itself was modified to carry the Trounce guidance equipment. Converted at the Mare Island shipyards near San Francisco, the Tunny was recommissioned in March 1953 and the Barbero returned to the fleet in October 1955. The first submarine launch of the Regulus took place on the USS Tunny on 15 July 1953. On both ships, the Regulus missile hangar would hold two missiles- to fire the Regulus, the submarine had to surface and the missile had to be manually rolled out of the hangar and manually unfolded to prepare it for launch. 

While the submarine force got ready for the Regulus, the Navy went ahead and deployed it from surface ships (several cruisers and aircraft carriers deployed with the Regulus) with the 50 kiloton Mk 5 warhead starting on May 1954. The first overseas deployment of the Regulus actually took place with surface ships- in 1955 the cruiser USS Los Angeles (three missiles) and the aircraft carrier USS Hancock (four missiles) deployed to the Western Pacific to cover Soviet targets in the Far East. It wasn't until 1958 that the Regulus went to sea aboard a submarine. Joining the USS Tunny and USS Barbero were two purpose-built diesel electric subs that were modifications of an existing design- the USS Grayback (SSG 574) and the USS Growler (SSG 577) were completed in 1958- the Grayback was built at Mare Island and the Growler was built at the Portsmouth shipyards in New Hampshire. There were plans initially to have Regulus capability on the first nuclear submarine, the USS Nautilus, but it was felt to minimize risk, the Nautilus was completed as a non-cruise missile submarine. However, funds were made available for a nuclear-powered Regulus submarine, and in 1960 the USS Halibut (SSGN 587) was commissioned, giving the US Navy five Regulus-armed boats. 

The first submarine nuclear deterrent patrol took place during the 1958 Lebanon crisis when the USS Tunny was ordered to patrol in the North Pacific to make up for the usual aircraft carrier that would have been present to hold Soviet targets in the Far East "at risk". This was more than two years before the first ballistic missile submarine, the USS George Washington, went to see with the Polaris SLBM. The USS Barbero was assigned to the Atlantic fleet and carried out deterrent patrols there from April 1956 to late 1958 before the Navy consolidated its Regulus subs with the Pacific Fleet. From September 1959 to July 1964, the Navy had at least one submarine on deterrent patrol in the North Pacific- the diesel electric boats would refuel at either Adak, Alaska, or Midway Island, before going out on the patrol. The sole nuclear-powered Regulus boat, the USS Halibut, didn't need the refueling stops. During that period, forty-one Regulus patrols were conducted, sometimes two of the subs were on patrol at once. The Regulus missiles during this period were armed with two megaton W27 warhead which replaced the earlier Mk 5 warhead.

Regulus launch from the USS Halibut.
The successor to the Regulus was to have been the supersonic Regulus II with twice the range and a heavier warhead. The development got as far as having a Regulus II fired from the USS Grayback in September 1958, but three months after the sub launch the Regulus II program was canceled as the decision had been made to accelerate and enlarge the Polaris missile program which was shaping up to be a much more practical system than cruise missiles. The Regulus missiles were retired as the Polaris come on line, the last Regulus deterrent patrol taking place in July 1964 which was five months before the Polaris missile patrols commenced in the North Pacific. Both the Barbero and Tunny were scrapped, but the Growler would become a museum boat in New York City at the Intrepid Sea-Air-Space Museum (it has a Regulus missile displayed in launch configuration). The USS Grayback become a special forces transport and served in this role until 1984. The USS Halibut had an impressive second career as an intelligence platform to carry out clandestine ocean operations. It served in this role until 1976. 

The Regulus ended up being an interim placeholder for the US Navy until the arrival of the ground-breaking Polaris missile. For almost five years, the Regulus subs patrolling the North Pacific were the only submarine nuclear deterrent. In fact, the USS Halibut was the second nuclear sub to be built to operate missile armament- the honor of the first actually goes to the USS George Washington with its Polaris missiles. It was launched five days before the USS Halibut in 1960, but it wasn't until late 1964 that it went on an operational deterrent patrol with Polaris.

Source: Cold War Submarines- The Design and Construction of US and Soviet Submarines by Norman Polmar and KJ Moore. Potomac Books, 2004, p86-93. Photos: US Navy Historical Center, Wikipedia.