29 December 2015

The First American Covert Overflights of the Soviet Union

1st Lieutenant Bryce Poe II, USAF
(Gathering of Eagles Association)
The introduction of nuclear weapons at the end of the Second World War had a profound influence in many combat doctrines and none nowhere else as much as that of airborne reconnaissance. In November 1945, General Henry "Hap" Arnold of the US Army Air Forces warned the US government that in the future, American leaders would require "continuous knowledge of potential enemies, including all aspects of their political, social, industrial, scientific and military life" if the United States was to avoid a surprise attack with nuclear weapons. Traditional reconnaissance doctrines had the use of airborne assets in support of ongoing combat operations. General Arnold and many of his contemporaries at the dawn of the Cold War recognized that airborne reconnaissance was needed to provide an assessment and early warning of potential enemies, namely the Soviet Union that was rapidly tightening its grip on Eastern Europe. The start of the Berlin Blockade in June 1948 pressed the issue further that up-to-date reconnaissance was needed of the Soviet Union should tensions escalate to an all-out conflict. Interestingly while the highest levels of the US government tried to determine the best way to make such an assessment, the United States Far East Air Forces (FEAF) based in Japan took the initiative to begin its own assessment of Soviet forces in their region in response to the rising tensions during the Berlin Blockade. The commander in chief of the US FEAF, Major General George Stratemeyer, ordered the 8th Tactical Reconnaissance Squadron and its Lockheed RF-80 Shooting Stars to begin a series of covert overflights of the Soviet Far East. Based at Yokota Air Base, Stratemeyer ordered the 8th TRS to deploy to Misawa AB on the northern Japanese home island of Hokkaido. Two pilots were selected with 1st Lieutenant Bryce Poe as the primary pilot for the secret missions to assess Soviet air strength in the region. The RF-80s were modified with larger wingtip tanks for longer range. Poe was instructed that if the coastline was free of clouds, dash into Soviet airspace, photograph the targets and dash back out and head back to Misawa as fast as possible. 

The first reconnaissance overflight (and USAF jet reconnaissance mission) of the Soviet Union took place on 10 May 1948 with 1Lt. Poe departing Misawa AB to overfly targets on Kuril Islands. Missions were flown to photograph targets on Sakhalin Island as well further to the north. The first overflight of the Soviet mainland took place on 10 March 1950 to photograph bases around the port of Vladivostok. Most of the airfields Poe had photographed were full of not just only Lend-Lease Bell -39 Airacobras and P-63 Kingcobras, but also late model Lavochkin piston fighters like the La-9 and La-11. Although jet powered, the RF-80s had increased drag and lower speeds with the larger external tanks needed for the recon missions which cut down on the performance margin over the Lavochkin fighters which often tried to give chase to the missions. 

Lockheed RF-80 with the enlarged camera nose section
What was impressive about these first overflights is that they were done at the initiative and discretion of General Stratemeyer without any prior clearance from Washington and they were done in the face of significant technical and logistical obstacles. The reconnaissance cameras used on the RF-80 were designed for piston-engined aircraft and lacked the capability to do stereo images in a high speed aircraft like the RF-80. Spare parts were in constant short supply and given that Misawa at the time was on the far northern part of a still rebuilding Japan, insuring even basic food rations for the 8th TRS personnel deployed north proved challenging. Many F-80 units based in Japan at the time found themselves the subject of "moonlight parts acquisitions" so the secret overflights could continue. 

Despite the failure of the Berlin Blockade which was finally lifted on 11 May 1949 and the formation of NATO, tensions remained high with the first detonation of a Soviet atomic bomb on 29 August 1949 followed by Mao Tse-Tung's Communist victory in China on 1 October 1949 over the Nationalists. With Stalin feeling more confident about the Soviet posture on the world stage, on 25 June 1950, the North Korean Army smashed across the DMZ on the Korean Peninsula, igniting the Korean War. In order to prevent further escalation the conflict, American reconnaissance pilots were instructed to avoid Chinese and Russian air space, however, the advance of North Korean forces meant that 1st Lt. Bryce Poe was called upon again by General Stratemeyer to begin a new set of secret overflights. In August 1950, he was called to FEAF HQ to again deploy out of Misawa and fly a series of missions against Soviet airfields in the region. While Soviet fighters tried more aggressively to intercept the RF-80s, none came close to getting shot down. By this point, the intelligence from Poe's flights was deemed critical by the Joint Chiefs of Staff and on 28 July 1950, the JCS requested official permission from the Secretary of Defense, Louis Johnson, for overflights of Chinese bases on the coasts adjacent to the Korea. Just four days later, President Truman gave his approval and again, because of his prior expertise, 1st Lt. Bryce Poe flew the missions against Chinese coastal targets and additional missions by other pilots were flown against Chinese ports opposite of Taiwan to make sure no amphibious assault preparations were underway to move against Taiwan. 

By the summer of 1950 discussions had been taking place at the Pentagon about using the more-capable North American RB-45 Tornado for overflight missions of Chinese and Soviet targets, but the aircraft being a bomber, it was felt at the time to be too politically risky, particularly as the Pentagon was seeking authority for overflights of Soviet targets in Europe as well as in the Far East. By this point Allied fortunes in the Korean War had improved following the landings at Inchon. Poe was once again called to FEAF HQ for a third set of covert overflights but the other pilot that he had been working with on the prior sets of overflights had been killed in action, so for this next set of missions, Bryce Poe would be the only pilot flying. Due to the secrecy of the missions, Poe did all his own flight planning. He was told by General Douglas MacArthur and General Stratemeyer what information they needed and Poe himself figured out the targets, routes, photographic equipment, times and altitudes. Despite the ongoing war in Korea, Poe found that the defensive posture of the Soviet airfields had only modestly increased, but as a precaution, F-80 Shooting Star fighters would meet Poe on his outbound leg to make sure no Soviet fighters were trying to tail him. 

Major General Bryce Poe II before retirement
Once he landed, the film was developed by one warrant officer and Poe himself did all the photo interpretation work and then hand carried the imagery to brief General MacArthur as well as General Stratemeyer and his FEAF deputy. It was a remarkable degree of authority given to a 1st lieutenant! Stratemeyer felt only barest minimum of individuals needed to be involved in the secret overflights. Bryce Poe rotated back to the United States in January 1951 after making nineteen secret overflights of Chinese and Soviet territory as well as 90 unclassified tactical reconnaissance missions in support of operations in Korea. After Korea, Poe flew as an exchange pilot with several NATO nations before serving as the executive officer to General Bernard Schriever at the Western Development Division where ICBM development was taking place. He then served as an Atlas ICBM missile officer with the Strategic Air Command before returning to reconnaissance in time for Vietnam. As vice-commander of the 460th Tactical Reconnaissance Wing, he flew 213 recon missions in the RF-4C Phantom in Vietnam. He later commanded the 26th Tactical Reconnaissance Wing with the United States Air Forces Europe. Following his USAFE assignments, he assumed command positions with the Ogden Air Logistics Center in Utah and at Wright Patterson AFB in Ohio. He retired in 1981 as a very decorated four-star general and veteran of two wars, flying west on 20 November 2000. 

Sources: Shadow Flights: America's Secret Air War Against the Soviet Union by Curtis Peebles. Presidio Press, 2000, pp 4-39.

24 December 2015

Saving Lockheed for Christmas

Carl Squier
I had written this article a year ago for Christmas but I think it's worth reposting given this is Christmas Eve. There are a lot of folks in aviation little known to history but whose actions footnotes of the time set the stage for larger events in history. Carl Squier is one such individual- the 13th licensed pilot in the United States, in 1917 he became an Army pilot and flew in France in the first World War and became a long time friend of American ace Eddie Rickenbacker.

In 1928 he became the VP of the Eastman Flying Boat company after a career barnstorming after he returned from the Western Front. That year Eastman was bought by the Detroit Aircraft Company and they sent him to California to manage a struggling subsidiary they had just also acquired, Lockheed Aircraft in Burbank. While running Lockheed for the parent company, he found himself a home in aviation and became a patron of the employees at the Burbank plant.
With the stock market crash and the Great Depression, Detroit Aircraft went bankrupt and it dragged Lockheed into the red. No one was sure if Lockheed would survive. A few days before Christmas, he sent the employees home early from the Burbank plant and at the exit, handed each demoralized employee a ten dollar bill (a hearty sum in those days) and wished them a Merry Christmas. All one-hundred ten employees of Lockheed Aircraft went home that evening with ten dollars, all from Carl Squier's own savings which he emptied for his employees. The following January he mortgaged his own car and home to make payroll for the employees. When Lockheed finally succumbed to bankruptcy a few months later, Lockheed only had three employees- his secretary, an accountant, and a stock clerk who doubled as the night watchman for the Burbank hangar of the company.

Carl Squier with Howard Hughes
Squier so believed the Lockheed name was too good to pass into history and the people he came to lead too good to abandon, he convinced an investor, Robert Gross, Gross' brother Courtlandt, three other men, and what he had left of his own savings to purchase Lockheed's remaining assets. Gross wanted to run an aircraft company of his own and in 1932 the group purchased what was left of Lockheed for $40,000. In the bankruptcy courtroom that day sitting in the back was none other than Allan Lockheed himself, who on his way out told Gross "I hope you know what you're doing". With a shoestring staff led by a young engineer they recruited, Hal Hibbard, Lockheed came back to life with its Lockheed Model 10 Electra. The Model 10 Electra was Amelia Earhart's aircraft on her ill-fated 1937 around the world flight. As Lockheed had limited resources and facilities at the time of the program launch, much of the wind tunnel work was done at the University of Michigan. Much of the tunnel work was done by a master's student at the school, a young engineer named Clarence "Kelly" Johnson. It was Johnson's suggestions based on the tunnel work on the Electra design that the aircraft switch from a single tail fin to twin tail fins as well as the deletion of the original large wing root fillets. When Kelly Johnson completed his master's degree, he was hired full time at Lockheed. 

Hal Hibbard and Robert Gross would go on to build Lockheed into one of the giants of American aviation and Kelly Johnson would design some of the most iconic aircraft of the century, but it all started with the passion, generosity, and salesmanship of Carl Squier. It was said that if it wasn't for Carl Squier, there wouldn't be a Lockheed. He retired in 1956 as the VP of sales and flew west in 1967.

Source: The Electra Story: Aviation's Greatest Mystery (Bantam Air & Space Series No. 9) by Robert Serling. Bantam Publishing, 1962, 1991.

19 December 2015

Navy Observation Squadron SIXTY-SEVEN (VO-67): Sub Hunters on the Ho Chi Minh Trail

Squadron patch of VO-67
(VO-67 Association)
Given the restrictions by the Johnson Administration that adopted as policy in prosecuting the war in Vietnam that the port of Haiphong was off limits as well as overland supply routes from China, the only way to stem the material support and infiltration of South Vietnam was the interdiction of traffic along the Ho Chi Minh Trail that ran west of Vietnam through Laos and Vietnam. Supplies and personnel flowed down the trail to Viet Cong insurgents operating throughout South Vietnam. Despite Laos' neutrality established in 1962, North Vietnam moved freely through Laos up and down the supply routes. In April 1965, with the permission of the Laotian government, the United States initiated Operation Steel Tiger to try and disrupt trail traffic. All targets on the trail were identified visually, a challenging proposition with dense jungle and often uncooperative tropical weather. Army ground teams were introduced to Operation Steel Tiger in October 1965. A progressive ramp up of airborne and ground reconnaissance failed to deprive the Viet Cong of the virtual river of supplies flowing through Laos. Needless to say, this state of affairs preoccupied the Secretary of Defense, Robert McNamara, who believed technology could provide a solution. Through the summer of 1966, academic and technology experts came up with the Jason Study. It suggested an electronic fence of detectors combined with airborne assets to stop the flow of materiel down the trail. The Defense Communications Planning Group (DCPG) was established by McNamara in September 1966 to develop and deploy the technology for the "electronic fence". To keep a handle on costs, the DCPG examined existing military technology to see what could be adapted for use on the Ho Chi Minh Trail. 

The modifications that resulted in the OP-2E Neptune
(ARC Forums)
The DCPG found that sonobuoys, used by the Navy for hunting submarines since the Second World War, could be adapted for land use, fitted with not only acoustic sensors but also seismic equipment to detect traffic on the Ho Chi Minh Trail. There were obvious parallels to finding an elusive enemy in the thick jungle and hunting Soviet subs in the open oceans. These land-based sonobuoys could then relay their findings to overhead aircraft to summon air strikes. In January 1967, McNamara briefed the White House on "Practice Nine" which was the code name for what become Operation Igloo White. "Muscle Shoals" was the code name for the electronic surveillance of the Ho Chi Minh Trail- "Igloo White" referred to the technologies used in adapting the Navy's sonobuoys into what were called spikebuoys (equipped with seismic sensors) and acoubuoys (acoustic sensors). Camouflaged and their aerials designed to look like branches, the spikebuoys implanted themselves in the ground while the acoubuoys were designed to snag the branches of the jungle canopy and hang in the trees. Given that the sensors were based on sonobuoy technology, the US Navy was tasked with seeding the Ho Chi Minh Trail by air with the new devices. 

By this point in the war, the North had fortified the trail with anti aircraft guns and there were discussions on how best to deliver the sensors. While the US Air Force prepared for the delivery of the sensors with F-4 Phantoms which would be less vulnerable, the Navy provided interim capability with a twelve-aircraft squadron using heavily modified Lockheed P-2 Neptunes. As the Navy's maritime patrol mission was being taken over the Lockheed P-3 Orion, surplus Neptunes were readily available. Martin Aircraft outside of Baltimore was tasked with the modification process which entailed the removal of the ASW equipment from the P-2s. Extensive armor plating was installed to protect the crews while the defensive weapons included underwing gun pods as well as two hatches in the aft fuselage for pintle-mounted M60 machine guns. A terrain-avoidance radar was added in a chin radome along with a whole host of defensive electronic warfare equipment. 

The MR tail code led to its radio call sign "Mud River"
(San Diego Air and Space Museum Archives)
With Navy crews well versed with low level sonobuoy delivery, there were no issues with delivering the acoustic sensors which would hang in the jungle canopy. However, the seismic sensors had to be dropped from higher altitudes as they had to implant themselves in the ground to detect truck traffic. The altitudes needed were much different than that used for sonobuoy delivery and it was found that old Norden bombsights in the nose worked well following a convincing demonstration at Eglin AFB in Florida. Twelve Norden sights were secured from storage and overhauled- since the bomb sights hadn't been used in years, the Navy had to locate retired Norden bombsight technicians to carry out the work. The USAF supplied an instructor who used to train bombardiers on the sight and he was sent to NAS Alameda to train the crews of the new secret Navy squadron which was designated VO-67. A training film on the use of the Norden was found at the Smithsonian Institution and was sent to VO-67. 

Designated the OP-2E Neptune, the first three VO-67 aircraft departed NAS Alameda on 6 November 1967 for RTAFB Nakhon Phanom in Thailand (nicknamed "Naked Fanny" by US crews or simply abbreviated "NKP"). At NKP, the crews of VO-67 flew with USAF forward air controller (FAC) pilots to see for themselves their operating areas over the Ho Chi Minh Trail. In fact, VO-67 personnel formed a close working relationship and even friendship with the USAF FAC pilots. FAC pilots who had just returned from patrols over the area often were met by VO-67 crews to review what the FAC pilots encountered over the trail. Each crew planned its own mission- the acoustic sensors were dropped at high speed and at low altitude, usually 500 feet, with plenty of jinking to avoid AAA fire. Terrain masking was frequently used. Often the Neptune pilots would dive down from 12,000 as they approached their target areas, drop a string of acoustic sensors and then use the terrain to egress the area. Seismic sensors were initially dropped from 2500 feet, later 5000 feet. Some Neptune crews would dive down during their seismic sensor drops to build up speed for the egress. Often times the underwing gun pods and rear M60 mounts were used for suppressive fire to keep the enemy's heads down during their target runs. 

CDR Paul Millius
(US Navy)
The missions were demanding and losses did take place- January 1968 (one aircraft lost), February 1968 (two aircraft lost). The last of the modified OP-2E aircraft joined the squadron at NKP just days after the third loss. During the Tet Offensive, the Marine fire base at Khe Sanh was under siege by an estimated 200,000 North Vietnamese troops. Along with some of the most intensive close air support of the Vietnam War, the Neptunes of VO-67 also dashed into the area to lay acoustic sensors to help detect NVA advances. By May of 1968, the USAF was ready to start delivering the sensors with its Phantoms with the job assigned to the 25th Tactical Fighter Squadron (part of the "Wolfpack" 8th Tactical Fighter Wing). The Phantoms would be less vulnerable than the lumbering Neptunes over the increasingly thick air defenses over the Ho Chi Minh Trail. The last VO-67 sensor drop mission took place on 25 June 1968 with the squadron being disestablished on 1 July 1968 and its personnel and aircraft returning to the United States. 

During its brief tour of duty, VO-67 lost one-quarter of its aircraft and 20 crewmen- and thanks to the airmanship of the crews and the invaluable help of the USAF FAC pilots who worked with VO-67, this loss rate is only half of what was expected at the start of VO-67's deployment. One pilot, Commander Paul Millius, was lost in action after his aircraft was hit at heavy caliber anti aircraft fire. One crewman was killed instantly and he kept flying until the other seven of his crew could bail out and survive. He was seen bailing out last, but was never found. He was promoted to the rank of Captain in 1972 and in 1978, he was presumed killed in action and posthumously awarded the Navy Cross. In 1995, the Navy launched the Arleigh Burke-class AEGIS destroyer USS Millius (DDG 69) in his honor, one of the few ships named for a naval aviator. The motto of the ship is "Alii Prae Me" (Others before me).

Related reading: 

Sources: Batcats: The United States Air Force 553rd Reconnaissance Wing in Southeast Asia by Jack Sikora and Larry Westin. iUniverse Publishing, 2003, pp 11-18, 73-75. VO-67 Association's Squadron History page at http://www.vo-67.org/vo67_history.html. 

14 December 2015

BEA Gets the Trident and More

BEA Trident 1C in the original delivery colors
A while back I had posted about a short lived proposal between Boeing and De Havilland for the former company to license build the DH.121 Trident in the United States. That was but one of many twists and turns in the rivalry between the DH.121 Trident and the Boeing 727. Building on the success of the 707 family, Boeing next launched the 727-100 for the short-haul market and like the Trident, was a T-tailed three-engined aircraft built broadly to the same specifications. But having cut its teeth on the commercial market successfully with the 707, the 727 quickly gained fame as a technological and aerodynamic success that could fly near its limiting Mach number at 37,000 feet smoothly yet possess the high-lift wings to allow it to land at speeds as low as 100mph and serve short airfields and smaller communities. The Trident, on the other hand, wasn't designed for short field performance and had the nickname "Gripper" by its pilots on account of its long takeoff run. Its engines weren't as powerful as the new Pratt & Whitney JT8Ds on the 727 and De Havilland actually pitched the Trident as an "economy aircraft" on contrast with the hot rod performance of the 727. 

De Havilland originally had designed a larger aircraft that could have boasted the seat-mile economics of the 727, but as the aircraft was being designed to British European Airways (BEA) requirements for European services, BEA wanted a smaller aircraft and the first version of the Trident carried only 78 passengers. It ended up having to compete with the successful Caravelle in capacity below the Trident and the Boeing 727 on the top end of the capacity segment. De Havilland even tried to pitch a version of the Trident to American Airlines which at that point hadn't made up its mind yet on the 727 whereas Eastern and United had already committed their launch orders. But in August 1961 American followed United and Eastern in ordering 25 727-100s in a crushing blow to the British sales effort. And to add insult to injury, De Havilland was having a difficult time pleasing BEA, its planned primary customer as BEA kept changing its requirements and asking for changes to the Trident design. Once changed and approved for production, BEA would come back with another set of changes resulting in a small production block with several different variants to suit BEA's wishes. Some in the De Havilland program felt that BEA was trying to sabotage the Trident with its requests while Boeing turned out 727s in only two basic versions by the hundreds. Even later versions of the Trident with higher-powered Rolls-Royce Spey engines and longer fuselages to carry more passengers failed to dent the 727 worldwide sales juggernaut as order after order bypassed the Trident in favor of the 727.

BEA Trident Two- the aircraft was progressively improved
On 22 November 1965 the British Minister of Aviation, John Stonehouse, affirmed the government's support for the longer ranged Trident Two version which interested BEA more than the Trident 1 versions (despite the Trident 1 being built to BEA's own specifications). Parliament even approved funding to launch the Trident Two program. But in the following year, the head of BEA, Sir Anthony Milward, not only said BEA needed less capacity than the Trident Two, but that he had also had discussions with Boeing and Douglas. Some historians feel that Milward was engaged in brinkmanship with the UK government to get the Tridents as the lowest price possible. Milward himself stated publicly that "BEA wanted to buy British, but that it could not afford to buy British if the product was not the best on the market." De Havilland then went on to create the Trident Three, BAC offered a stretched version of the BAC One-Eleven and even Vickers proposed a short-haul version of the VC-10. But the 727-200, 737-200, and the DC-9 were also on BEA's table for discussion. 

With the election of a new Labour Party government keen on supporting British industry, Milward warned that "If a British aircraft was available to do this job at the right price we'd be delighted. At the moment there are no signs that such a British aircraft is available." It was well-known that BEA had asked for approval to purchase 35 727-200s and 737-200s. De Havilland was astonished that after creating larger versions of the Trident, BEA said the market had an overcapacity, but then turned around and wanted order larger American aircraft. 

BEA Trident Three in British European's final livery
Already the Labour government was under fire for campaigning to support British industry but had already ordered the McDonnell Douglas F-4 Phantom, the Lockheed C-130 Hercules, and the General Dynamics F-111 to replace the canceled TSR.2. Despite BEA's desires for American jets, the political winds in London of the day dictated that they had to buy British, no matter what. BAC offered the Two-Eleven successor design to the One-Eleven, but BAC required millions of dollars in launch aid to start work on the Two-Eleven. Eventually the Two-Eleven project had to be abandoned and support had to be shifted over to the penultimate version of the Trident, the Trident Three. BEA was directed to purchase this aircraft and Milward made plain that the Trident Three was BEA's third choice and if it were compelled to operate the Trident Three, then BEA should receive compensation from the British government for not getting the more economical 727-200s and 737-200s they wanted. 

The new Minister of Aviation, John Mulley, found himself backed into a corner by BEA and the British government. BEA had to buy the Trident Three at the direction of the government but BEA wanted compensation to offset the higher operating economics of operating the Trident Three. 

On 13 March 1968, BEA announced it was ordering 26 Trident Threes with options for 10 more. Four months later, the government announced what was called the "Mulley Pledge"- approximately US$50 million was transferred to BEA and was calculated to be the cost difference between the higher seat-mile costs of the Trident Three versus the 727-200. And additional 50% of that initial transfer would be made available later to BEA, fufilling the Labour government's pledge to support the British aircraft industry. 

09 December 2015

The Boeing 767 and the Birth of ETOPS

Federal Aviation Regulation (FAR) 121.161 states "Unless authorized by the administrator, based on the character of the terrain, the kind of operation, or the performance of the airplane to be used, no certificate holder may operate two-engine airplanes over a route that contains a point farther than 1 hour flying time (in still air at normal cruising speed with one engine inoperative) from an adequate airport." The rule was written in the days of the propliner when piston engines didn't have the reliability of modern jet turbines. When the Boeing 767-200ER entered service, it was the first commercial twin-jet capable of crossing the oceans*- when Boeing's director of engineering, Dick Taylor, first approached FAA administrator Lyn Helms in 1980, Helms responded "It'll be a cold day in hell before I let twins fly long haul, overwater routes." Helms even felt that the 60-minute rule was too generous. Despite his opposition, though, in 1982, the FAA began technical discussions with aircraft manufacturers, airlines and ICAO (they had formed a study group of their own in 1982) on the possibility of extended twin-engine overwater flights. At an ICAO meeting in Montreal that December, the FAA asked airline operators of twin jet aircraft to compile a database of inflight events and engine shut downs. Since long range commercial twins were relatively new to the market, the FAA needed a database to draw upon in figuring out the regulatory details of what would become ETOPS flying. After the Air Canada Flight 143 incident (the "Gimli Glider) where fuel starvation resulted in a skillful emergency landing on an old Canadian military air strip, some thought it a set back for what Dick Taylor had been pushing for with the Boeing 767. However, in a speech to the Royal Aeronautical Society in London in late 1983, he argued that fuel starvation would have shut down all the engines regardless of whether you have two, three, or four engines. 

N767BA, the Boeing 767 prototype
(Seattle Municipal Archives via Wikipedia)
In 1980 three- and four-engined aircraft handled all the long range routes, particularly those that were overwater. There was a joke that stated "The reason I fly four-engined aircraft across the ocean is because there are no five-engined aircraft." But modern technology and computerized systems brought to the Boeing 767 a level of redundancy, safety, and efficiency not seen in any prior commercial aircraft. And it wasn't just the reliability of the engines, the various systems of the 767 facilitated the development of ETOPS- Extended-range Twin-engine Operational Performance Standards- the ability of a twin engine jetliner to exceed the old 60-minute rule.

*I should point out at this point that before the 767, some Airbus A300 operators were flying overwater routes beyond the FAA's 60-minute rule under ICAO regulations, but that's beyond the scope of this article and I'll be touching upon the A300 in a future article on ETOPS history. 

For two years Boeing collected reams of data on the first 767 operations, compiling information on every shutdown and failure of any system including the engines in the first two years of commercial airline services. This was supplemented by the FAA/ICAO database that was started in 1982. In April 1984 El Al Israel Airlines became the first airline to operate the 767 on trans-Atlantic services between Montreal and Tel Aviv, but the aircraft's routing complied with the 60-minute rule. Not long after, El Al, Air Canada, and Trans World Airlines (TWA) received exemptions to operate no more than 75 minutes from a suitable diversion airport. This would open up some trans-Atlantic routes and Caribbean routes to the 767. In fact, Air Canada was the first to crack the 60-minute barrier having earned its 75-minute exemption in late 1983. By this point Lyn Helms was no longer the FAA Administrator, the post now assumed by Donald Engen who was more open minded to extended twin overwater flights. (Engen would later become the head of the National Air & Space Museum) Interestingly and perhaps not surprisingly, one of the biggest opponents of ETOPS at the time was McDonnell Douglas, who saw the future of the DC-10 line threatened by the 767. 

In June 1984 Boeing showcased the new 767-200ER's long legs with a 7,500 mile delivery flight from Washington Dulles to Addis Adaba, Ethiopia to bring the 767 to Ethiopian Airlines. The flight required a special one-time FAA waiver to take place. In October 1984 Air Canada took delivery of the first ETOPS-qualified 767-200ER which was permitted to go 75 minutes from a suitable diversion airport. The International Civil Aviation Organization (ICAO), the International Federation of Air Line Pilots Association, the US-based pilots' union Air Line Pilots Association (ALPA) and the FAA made several recommendations to Boeing that resulted in the 767-200ER having a fourth electrical generator independently powered by a hydraulic motor, additional fire suppression features and equipment for cooling of the CRT displays in the cockpit.

By 1985 Dick Taylor at Boeing was lobbying the FAA hard for extension of the 75-minute rule to 120 minutes which would open up a large number of trans-Atlantic routes to the 767. Already several airlines led by TWA had petitioned the FAA for an ETOPS extension to 120 minutes but before the FAA would grant the extension, Boeing had to show "statistical maturity" by equipping a number of 767s with special data gathering equipment to show unparalleled standards of inflight reliability and the Pratt & Whitney JT9D engines had to log 250,000 consecutive flight hours on passenger flights with a very low rate of shutdown.

Trans World Airlines made the first 120-minute ETOPS flight in 1985
(Jon Proctor Collection via Wikipedia)
On 1 February 1985, TWA Flight 810 departed Boston for Paris on the first revenue passenger flight in history under the 120-minute ETOPS rule. The new ETOPS rule shortened the flight distance and it would replace a Lockheed L-1011 Tristar that normally served the route. Before Flight 810 departed, sixteen TWA pilots went through specialized ETOPS training on international requirements, intensive time in a simulator and landing procedures for the airport at Sondrestromfjord in Greenland, the designated 120-minute diversion airport. Eleven observers from the FAA were aboard TWA 810 and the fuel burn was found to be 7,000 lbs an hour less than that of the L-1011 Tristar on the same route. TWA was so convinced of the efficiency of the 767 with the 120-minute ETOPS rule that it spent $2.6 million per aircraft retrofitting all of its 767-200s for 120-minute ETOPS compliance.

But Boeing and Dick Taylor didn't stop there. The existing 120-minute ETOPS rule wasn't enough to get the 767 to Hawaii from California. But Boeing continued to compile failure and shutdown data on the 767 on the trans-Atlantic route to prove the the FAA that it was possible to safely operate the 767 to Hawaii from the US mainland. In 1989, the FAA approved the ETOPS extension to 180 minutes which opened up Hawaii to the 767, as the halfway point between Hawaii and the US mainland is approximately 150 minutes' flying time. But to gain the 180-minute extension, a particular aircraft and engine combination had to show 12 consecutive months of 120-minute ETOPS flights and meet stringent engine failure rates. The first 180-minutes ETOPS flights were made by American Airlines on the DFW-Honolulu routing starting in 1989. By 1993 the entire 767 family, both the -200 and the -300, as well as the possible engine options of GE, Pratt & Whitney, and Rolls-Royce, gained full 180-minute ETOPS extensions.

The first commercial 180-minute ETOPS flights were made by American 767-300ERs DFW-HNL
(Aero Icarus Collection via Wikipedia)
By 1991 the number of passengers crossing the Atlantic on 767s exceeded the number of passengers crossing on three- and four-engined aircraft for the first time in history. By 2000, over 50% of all trans-Atlantic crossings were being made by the 767 family of aircraft. By that time, all brand new 767s rolling out at Boeing's factory in Everett were certified for 180 minutes ETOPS extensions.

It will be the legacy of the Boeing 767 to show that any place in the world could be crossed safely and efficiently with only two engines and it set the stage for the arrival of the Boeing 777 and Airbus A330 family of aircraft that routinely fly routes today that were once the exclusive domain of multi-engined aircraft like the Boeing 747, A340, DC-10/MD-11 and L-1011 Tristar.

Source: Boeing 757 and 767 (Crowood Aviation Series) by Thomas Becher. The Crowood Press, 1999, p145-155.

04 December 2015

The Humble Birth of Grumman Aircraft

Leroy Grumman (Time Magazine)
In October 1920, the head of the Loening Company, Grover Loening, had been supervising the construction of a two-seat naval floatplane at two locations- at Loening's own plant at 31st Street on the East River in mid-town Manhattan and at the Naval Aircraft Factory in Philadelphia. It was in Philadelphia that Loening convinced one of the Navy's test pilots to resign his commission and join his company. That young 25-year old naval lieutenant was Leroy Grumman. The young Grumman rose quickly to the top ranks of Loening's company and by 1924 Loening had hired two other talented individuals to support Grumman- Jake Swirbul and Bill Schwendler. Loening's company prospered right until the 1927 when Lindbergh's solo flight across the Atlantic sparked the imagination of American business which was already riding a bull market in Wall Street. Though well-run, Loening began to falter and in 1928 Grover Loening sold his company which was to be absorbed by the Keystone Aircraft Company which at the time was building a twin-engine bomber for the US Army Air Corps. In less than a year, Keystone itself was purchased by Curtiss Wright. Under the terms of the sale, Loening's Manhattan factory would be shut down and all the employees were assured employment if they moved to Keystone's main facility in Bristol, Pennsylvania.

Leroy Grumman and his two closest friends, Jake Swirbul and Bill Schwendler, weren't happy about having to move to Pennsylvania as they had settled in the New York City area and had families that would have to be moved. So in 1929 the trio decided they'd form their own aircraft company and stay in the New York City area. Since Grover Loening and his brother were barred from forming another aircraft company as part of the terms of the sale, they decided that investing in Grumman's fledgling enterprise would be the next best thing. Their first act was to hire Loening's treasurer who also happened to be from a prosperous New York family that offered to invest with Grumman as well. In contrast to the businesses of the day, however, Grumman decided that control of the company would rest only with a few individuals and to not canvas Wall Street for further investors. It proved to be a wise move with the Wall Street crash just over a month away. 

Grumman then set about to recruit the thirty most skilled employees at the Loening plant. His years of service under Loening endeared him to many of the Loening workers and all asked, with the exception of one or two, threw their fate into Grumman's hands. In addition, Grumman, being a financially cautious individual, decided that his new company would only seek the business of the US military, preferably the US Navy given Grumman's background as a naval aviator and their long history of doing business with the sea service during their employment with Loening. In order to fund their day-to-day operations, they would repair existing Loening amphibians at a rented facility in Long Island. 

On 5 December 1929, Leroy Grumman and his five founding associates met for the first time and the following day the Grumman Aircraft Engineering Company was born. Much of the company's initial capital came from Grumman's severance pay from Loening. Jake Swirbul's widowed mother worked for a wealthy Long Island family that so much of her that they lent Swirbul enough money to become the first vice-president of Grumman. A few months later in March 1930, the rest of the tiny company's employees were allowed to purchase stock (On the eve of the maiden flight of the Grumman F-14 Tomcat, those employees' initial investment over 40 years had multiplied by a factor of 7,700!). 

Their first design proposal was for the US Navy, which at the time had a two-seat scout biplane, the Vought O2U Corsair. The Corsair could be fitted with floats for operation from cruisers and battleships or it could be fitted with landing gear for operation from aircraft carriers. Grumman's proposal was for a new float that was not only lighter and stronger than the existing main float used on the Corsair, but it would also incorporate a fully-retractable landing gear to allow true amphibious capability. In 1930, fully-retractable landing gear were a novelty- on the Loening amphibians, the landing gear simply swung upward out of the way but what Grumman and his team proposed was a streamlined arrangement in which the gear would be fully retracted into the sides of the central float. 

Vought O2U with the Grumman-design center float (Wikipedia)
The Navy was intrigued by this modification of its O2U scoutplanes, and asked Grumman for a demonstration. Many in the Navy were skeptical that a float lighter than the existing float could be stronger, let alone be strong enough to accommodate a full-retractable landing gear. But Grumman's design was an early pioneer in monocoque construction in which the skin of the float carried a good portion of the stress loads and as such, didn't need a heavy internal framework that was the standard in aircraft construction of the day. The Navy paid Grumman $33,700 for two such prototype floats for testing at the naval yards in Anacostia in Washington, DC. The floats would be attached to Vought O2Us that would be launched from test catapults as that was the most stress anticipated on such a float arrangement. The landing gear was manually operated, but was designed so that either mechanical or hydraulic power could be added.

On the day of the flight tests, the Navy couldn't find an observer willing to sit in the second seat of the modified scoutplane. Many thought Grumman's float would either crumple up on launch or collapse on landing either on land or on water. Not wanting to delay the flight tests, both Leroy Grumman and Jake Swirbul both volunteered to sit in the observer's seat on different flights to prove their faith in the monocoque design. The day's test flights were of course successful and Grumman walked away with his first Navy contract for what was called the Grumman Model A float. In addition, the Navy had asked Grumman the possibility of using the retractable landing gear on its single seat carrier fighters. Grumman offered to go one better and on February 1930 began work on what would be come the first Grumman fighter, the FF-1. Grumman's landing gear design would go on to be used on not just the FF-1, but also the F2F and F3F biplane carrier fighters and on the F4F Wildcat used in the Second World War. 

Source: The Grumman Story by Richard Thruelsen. Praeger Publishers, 1976, p17-41.

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.