XV. FETCHING THE UIVER FROM CALIFORNIA

Like most of my colleagues, I received my flight training at the Military Aviation Department in Soesterberg. The year of my training ranks among the most pleasant times of my life. I look back with great gratitude to 29 November 1926, the day I reported to Captain Versteegh at Soesterberg, who remains the head of the Military Flight School.

I was assigned Sergeant-Major P.J. v.d. Griendt—now a Warrant Officer—as my instructor. The patience and dedication of this irreproachable flight instructor, who taught me the fundamentals of flight in his own inimitable way, laid the foundation for the success of my aviation career.

From a young age, it had been my ambition to become a commercial pilot. Thanks to the cooperation of Captain Versteegh and the Commandant of the Aviation Department, I was seconded to KLM very shortly after obtaining my military wings.

The excellent training I received at this company soon opened my eyes to the many possibilities within commercial aviation. From the start, I endeavoured to specialise as much as possible, both theoretically and practically, in the profession I so ardently desired.

On 1 May 1929, I received a permanent appointment as a commercial pilot with KLM. My greatest thrill came when I landed in Paris for the first time as a captain in a Fokker F VIIa with eight passengers.

I owe a great deal of gratitude for my training as a commercial pilot to Mr I.A. Aler, KLM’s Head of Flight Operations, and especially to my senior colleagues. I would like to mention specifically the names well known to you all: Sillevis, Geijsendorffer, Smirnoff, Beekman, Duimelaar, and Tepas.

KLM’s Director tasked me with studying all aids to ensure the safety of night flying, and in connection with this, I was sent to America in October 1933. I flew as a co-pilot on all the major American night-flying services. This included two round-trip flights from the Atlantic to the Pacific, crossing America twice via different routes. I gained extensive experience in night flying and received great assistance and hospitality from the American authorities and airlines.

In the summer of 1934, I was appointed to take delivery of the Douglas DC-2 from the Douglas factory in California and fly it to New York, together with Hendrik Veenendaal, KLM’s American representative and chief engineer. Thus, in early July, I arrived at New York harbour aboard the SS Volendam, where Veenendaal and several American friends were waiting for me.

I must tell you more about Mr Veenendaal, who is known in America as ‘Curly’ on account of his hair, as he played a very significant role in the delivery of the Douglas.

Curly Veenendaal has been with KLM since its inception. He had already made several trips to America and, on this occasion, had been sent out a few weeks ahead of me. He is a man of exceptional qualities. Besides his technical talents, he is a jack-of-all-trades and a fine comrade.

After some discussions in New York, we left for California a few days later. We flew from New York in a Boeing aircraft belonging to United Airlines via Chicago to Kansas City. There, we were to transfer to a machine from Transcontinental & Western Air (TWA). It was incredibly hot during those days. When we descended from the cool altitudes into the sweltering heat of Kansas City airfield, it felt as though we had stepped into an oven.

It was then about ten o’clock; the aircraft that was to take us to Los Angeles was scheduled to depart an hour later.

Repeated flashes of lightning pierced the western sky, and I saw Curly pull a doubtful face as he paid for the tickets. I tried to reassure him: ‘It’s just a local thundershower. It’ll blow over before eleven.’

However, the storm grew increasingly fierce. To make matters worse, a whirlwind kicked up so much sand that we had to take hasty refuge in the terminal building. We went to the meteorological service to enquire about the outlook. They informed us that it was a local storm front that would soon disappear in a south-easterly direction.

By eleven o’clock, however, Curly was still staring at the western horizon, where the lightning continued with unabated intensity. As often happens, the storm front refused to head south-east, despite all meteorological laws, and stubbornly held its position. This led the TWA pilot to decide to wait for the next weather report.

Meanwhile, Curly had begun a very animated conversation. He thought it a pity that one saw so little of the beautiful landscape when flying at night. He suggested that travelling by train would be a nice change of pace and argued that the Douglas wouldn’t be ready yet anyway. He also pointed out that our flight would probably be cancelled, and that an express train for Los Angeles was leaving Kansas City at five past twelve—and so on, and so forth.

I used all my eloquence to change his mind, claiming the depression was bound to move on and that we would save time and travel in much more comfort. Suddenly, a rattling peal of thunder sent Curly running to the ticket office. He decided to play it safe and, for once, take the train. He got his money back, and ten minutes later, we were in a taxi heading for Kansas City station.

We spent two days and nights in a railway compartment. The landscape was indeed very interesting: deserts, mountains, and steppes, where the skeletons of cows that had perished from the drought lay on either side of the tracks. The temperature fluctuated between 49 and 54 °C. On the train, we met various Americans who complained bitterly about the heat. We, however, acted as though we felt perfectly comfortable in such temperatures and killed time by telling the most fantastic stories about the temperatures we had experienced ‘back home in Baghdad or Jask.’

It was Saturday night when our train rolled into Los Angeles station. Over the last few hours, it had become considerably cooler. The climate in California’s coastal towns is very pleasant indeed. We took up residence in a hotel in Hollywood, unaware that we would have to spend two months there instead of a few weeks.

The following Monday morning, we paid our first visit to the Douglas factory in Santa Monica, where a large series of DC-2 airliners was under construction. Transcontinental & Western Air had ordered forty of these machines, among others.

We had already heard in New York that there would be a delay in the delivery of our aircraft. Naturally, we were burning with curiosity to see how far our Douglas had progressed and when the first flight might take place.

In the factory’s enormous hall, a large number of fuselages stood in a row—the production line. When we asked where our machine was, they led us to one of these fuselages at the very beginning of the line: ‘This is number 18, the KLM machine.’

It was easy to see that our plane was still only in the early stages of construction. The Douglas factory calculated that the aircraft would not be able to make its first test flights until the second half of August, instead of 15 July, which had been the initial delivery date.

Curly and I calculated that this would likely be too late to get the aircraft to Holland in time for the Melbourne race. It was a great disappointment, but Curly was less pessimistic than I. ‘It’ll be fine,’ he said. ‘I’ll bet you there is something we can do about it, and that in three months’ time, you’ll be in Australia with this plane.’ Thus, I placed my first bet regarding the MacRobertson Race—and I sincerely hoped to lose this time.

The delay was due to various circumstances: a shortage of materials, factory renovations for a new manufacturing system, and so on. Naturally, the Douglas factory was very keen to deliver our machine on time so it could participate in the Melbourne race, but they were somewhat bound by contracts with American airlines.

In the end, we managed to have our machine assembled a little earlier, so delivery could still take place in time, even if it meant considerably less time for preparation and test flights than originally expected.

In the meantime, this delay gave us a splendid opportunity to study the Douglas construction system thoroughly and to follow the entire build of our aircraft from start to finish.

As is well known, Douglas aircraft are made of metal, primarily ‘alclad’. This is an aluminium alloy consisting mainly of duralumin, a very strong and light metal, with a protective layer of aluminium applied to the outside to prevent oxidation. The alclad sheets are joined together with ‘refined’ aluminium rivets. This riveting takes place while the rivets are kept at a very low temperature in refrigerators to keep the material—which has previously undergone heat treatment—in a soft state.

The peculiar thing about the Douglas construction is that longitudinal stringers are used almost nowhere. The necessary stiffness is achieved because all stresses are absorbed by the skin, the alclad covering. Thus, the entire fuselage is essentially nothing more than a hollow cigar, with thin transverse frames but no longitudinal stringers. Yet this construction is extremely solid and has the great advantage of being exceptionally light.

On one side of the factory are assembly jigs where the frames are riveted together with small sheets of alclad. As soon as the fuselage shape is ready, it moves into the production line for further finishing. Here, the entire cabin lining, soundproofing, electrical installation, instrument panel, controls, and so on, are installed. The fuselage keeps moving forward until it reaches the middle of the factory.

On the other side, the wing centre sections with the engine nacelles are manufactured. The fuel tanks, control cables, and rods for the engines and wing flaps are installed here.

The manufacturing system is based on a complete fuselage from one side and a fully prepared wing centre section from the other arriving simultaneously in the middle of the factory, where they are joined together. The assembly then moves backwards into the so-called mounting line, where the landing gear, tail surfaces, and engines are fitted, and the various lines and connections are hooked up.

The fuselage, now standing on its own legs and with the centre section and engines already giving a clear impression that this product is destined for higher regions, rolls ever further. Finally, when both wing halves have been attached, the aircraft reaches the rear part of the factory bordering Clover Field. The large sliding doors roll open, and the new Douglas DC-2 stands glistening in the rays of the Californian sun, ready for final inspection and its maiden flight.

Every time a plane was rolled out of the back door onto the airfield, I was present to take part in the initial test flights, which were conducted by pilots from the Douglas factory and the American airlines. In this way, I gained considerable experience on this type before our own machine was ready.

Furthermore, I made test flights in several other American aircraft built in California, including the Lockheed ‘Electra’ airliner—a construction similar to the Douglas but of much smaller dimensions. Fokker has also acquired the European manufacturing rights for this aircraft, which possesses excellent flying characteristics and a cruising speed of 320 kilometres per hour.

I shall now list some interesting details regarding the Douglas aircraft.

The Douglas system is built upon results obtained from many experimental Northrop machines. The Northrop construction is the foundation of the Douglas; before the Douglas Company took over the Northrop factory and financed the further development of this system, vast sums had already been spent on it. These costs covered all scientific research from the very beginning: numerous wind tunnel tests, years of material research, inventions in the field of metal treatment, and many costly experimental constructions. Over the years, millions were swallowed up. Even so, the construction of the first twin-engined Douglas aircraft still cost approximately $500,000.

The ‘soundproofing’ of the cabin using sound-absorbing material was carried out by the scientific department of the Sperry Company in New York. The result is that one can carry on a quiet conversation in the cabin without raising one’s voice. There is certainly less noise during flight than in some trains, which is particularly pleasant for passengers, especially over long distances.

The high speed is achieved through the aircraft’s excellent streamlined form. The retraction of the landing gear is done hydraulically—that is, by means of oil pressure. For this purpose, there is an oil pump in the cockpit with which pressure can be pumped into a long cylinder containing a piston. This piston is connected to the landing gear by a rod.

If oil is pumped into the cylinder below the piston, it is pushed upwards, and the connecting rod takes the landing gear up with it. This significantly reduces parasitic drag and considerably increases speed and climbing power. However, the wheels do not disappear entirely into the nacelles but protrude by about 18 cm. This makes it possible to set the aircraft down on the ground without damage even with the landing gear retracted; only the propeller blades will bend.

To extend the landing gear again, one need only turn a valve, which connects the oil reservoir to the part of the cylinder above the piston. By using the same oil pump, the landing gear is lowered until it reaches the correct position, where it is automatically secured by a safety lock.

In the early aircraft, it happened a few times that pilots forgot to lower the landing gear before landing, resulting each time in serious damage to the very expensive propeller blades.

Control lights are installed in the cockpit; only when the green light is on is everything safe for landing. To prevent the pilot from forgetting to check this signal, a system was devised that works as follows: if the landing gear is not fully extended, or if the safety lock has not functioned, a red light shines in the cockpit instead of a green one. If the pilot fails to see this and still attempts to land, a horn begins to blare right by his ear as soon as he pulls back the engine throttles. Since then, no more propellers have been damaged through inattentiveness.

The same hydraulic system used for the landing gear also operates the so-called landing or braking flaps. These serve to increase the aircraft’s glide angle, allowing for a steep approach over high obstacles such as trees or hangars, while also significantly shortening the landing run. For instance, if one has to come in over a thirty-metre obstacle, one could only touch down 500 metres away without landing flaps. With the flaps down, the glide angle becomes so much steeper that the aircraft touches the ground just 170 metres from the obstacle. Furthermore, the landing speed is reduced from 110 km/h to 93 km/h. This is a very great advantage for landing on small airfields.

It is interesting to note that with the landing flaps down and the undercarriage extended, the aircraft’s total air resistance is three times greater than when the flaps are up and the wheels retracted.

The two Wright ‘Cyclone’ engines installed in the Douglas are of the nine-cylinder air-cooled type, each having a normal output of 700 hp. The propeller is not driven directly by the engine shaft but through a reduction gear, so that the propeller turns more slowly than the engine. The ratio between the revolutions of the engine shaft and the propeller shaft is 16:11. Thus, when the engine runs at 1,600 rpm, the screw only makes 1,100. This increases the propeller’s efficiency and reduces noise.

The large three-bladed Hamilton propellers are of the variable-pitch type and are made entirely of aluminium. The angle of the propeller blades can be changed by the pilot during flight; this allows for a very short take-off and good climbing power, while simultaneously achieving a very high speed.

Variable-pitch propellers have only been in use for a relatively short time; it took several years before a reliable design was achieved. This is hardly surprising when one considers the immense centrifugal forces acting on the propeller blades and shafts in modern heavy aero-engines. Moreover, the pitch-change mechanism must be housed within the propeller hub itself and operated by the fast-spinning engine shaft. The adjustment of the Hamilton propellers is effected by engine oil pressure, which is fed through the hollow propeller shaft. A set of counterweights brings the blades back to their previous position.

The use of variable-pitch propellers has given a great boost to increasing aircraft speeds. To understand this clearly, a further explanation is necessary.

One might imagine a spinning propeller on a stationary aircraft as a disc; the blade tips describe a circle. The plane of this circle is called the ‘propeller plane’. The almost flat back of the propeller blades is always at an angle relative to the propeller plane. This angle is called the ‘pitch angle’, or simply ‘pitch’. With non-variable propellers, this angle cannot change during flight.

The speed of an aircraft depends—besides its aerodynamic shape—on the ‘thrust’ imparted to the engine shaft by the engine-driven propeller. This thrust, in turn, depends on the rotational speed, the dimensions, the number of blades, and the so-called ‘angle of attack’ of the propeller blades.

By angle of attack, we mean the angle at which the flat back of the propeller blade strikes the air particles. It is clear that this angle changes as soon as the aircraft begins to move. In a stationary aircraft, the pitch angle is equal to the angle of attack of the rotating propeller blade; the faster the aircraft moves forward, the smaller the angle of attack becomes.

Efficiency—and thus thrust—is greatest at a specific angle of attack, depending on the profile of the propeller blade. If the angle of attack is too large, the propeller blade is ‘stalled’ and the thrust is low. This can best be compared to an aircraft pulling up too steeply; the angle of attack of the wing then becomes so great that the smooth airflow around the wing profile breaks up, turbulence occurs, and the wing loses lift. The aircraft is then said to be ‘stalled’.

If the angle of attack of the propeller blades is too small, too few air particles are struck by the propeller, and the efficiency is likewise low. With fixed-pitch propellers, one must choose a pitch angle such that the angle of attack is as favourable as possible at the desired flying speed. However, it often happens that an aircraft climbs poorly and requires a long take-off run because the propeller blades, set for high speed, have too large an angle of attack. One must always find a compromise and set the pitch so that efficiency is as favourable as possible at both low speeds (climbing) and the much higher cruising speed. This usually means sacrificing either speed or climbing power, and often both.

Naturally, as aircraft speeds increased, this became an increasingly difficult problem, leading to more focus than ever on the technical development of controllable-pitch propellers. The propellers used on the Uiver can be used in two positions. At take-off, the blades are set to ‘low pitch’, which provides a favourable angle of attack at the speed at which the aircraft leaves the ground (about 90 km/h). As soon as the aircraft reaches a safe altitude, it switches to ‘high pitch’, allowing the propellers to deliver maximum efficiency at the aircraft’s cruising speed (280–310 km/h).

The manufacturing system at the Douglas factory is based on everyone specialising in making or assembling a particular part. Most parts and the plating are manufactured by machine or from templates. The Douglas factory employed about 3,000 staff, and work continued day and night in three shifts.

Finally, the day arrived when our Douglas was to fly. On 16 August 1934, Douglas DC-2 No. 18, which would later cause a stir across the globe under the name ‘Uiver’, took to the skies for the first time. There followed several busy days: final inspections, acceptance flights, and test flights for the certificate of airworthiness. All tests were carried out by the Vice President of the Douglas factory, Mr Carl A. Cover—himself an excellent test pilot—and me. When everything had finally been settled to the satisfaction of all parties, the journey to New York commenced on 22 August.

The aircraft was fully complete and already bore the Dutch registration letters PH-AJU. The radio, however, was not to be installed until we reached Holland. Consequently, it was decided to make the flight to New York in three or four days, weather permitting.

On the first day, we flew to Abilene, Texas, with a stop at El Paso, where we stayed the night. We departed very early the next morning and encountered a deep depression, which brought us very low clouds and heavy rain. Since we had no radio, we landed successively at Springfield and St Louis, and finally in Dayton, Ohio, where we decided to stay the night and fly directly to New York the following morning.

The next day, however, the weather proved very unfavourable, and there were many interesting sights to see in Dayton. As a result, the clock showed three in the afternoon before the Douglas was back in its element. With a stop in Detroit, we arrived in Buffalo at sunset after a magnificent flight over Lake Erie. We stayed the night there, and the following morning, PH-AJU was at North Beach airfield near New York.

This site had been chosen because it is located on the bay. This allowed the aircraft to be transported by lighter; moving it by road would have presented serious difficulties due to its large dimensions.

Now the task was to dismantle the Douglas as quickly as possible. The wings, tail surfaces, propellers, and other parts had to be carefully packed into large crates, which was done under the supervision of Bluefriesveem. Curly saw to it with the utmost conscientiousness that everything was done professionally, personally marking all parts with great precision.

It was an anxious moment to see the fuselage—though the centre section of the wing with the engines remained attached—hanging from a hoist to be transferred from the airfield onto a lighter for transport to the Holland-America Line in Hoboken. Even more nerve-wracking, however, was the transfer from the lighter to the deck of the SS Statendam, as there was very little room to spare. Everything went as planned, and on 4 September, the Statendam departed New York with the Douglas and yours truly.

Curly did not come along; he had to return to California. As he stood on the pier, I could see how much it pained him that the Douglas was being taken to Holland without him and would have to be assembled without his expert assistance.

The crossing to Europe would also bring some tense hours for me. The two crates containing the wings had been placed on top of each other right against the railing, so that the top one protruded quite a bit above it. In calm seas, this would have posed no problem at all, but halfway across the Atlantic, we hit bad weather. To make matters worse, one of the Statendam’s engines suffered a failure, causing the ship to lose much of her speed. During that stormy night, we tossed violently back and forth amidst the towering waves. In my cabin, I heard the waves pounding against the ship, and in my mind’s eye, I could already see the top crate with the wing of the Douglas—and with it our last hope of participating in the Melbourne race—disappearing into the sea.

Although I was perfectly aware that I would be powerless if fate chose to play such a trick on us, and I was convinced that our Captain and the Chief Officer had done everything in their power, I still went upstairs from time to time to see if there was still a complete aircraft on the deck.

It ended well. We arrived safely in Rotterdam. The Douglas was unloaded and taken to Waalhaven airfield to be assembled by KLM’s Technical Department under the expert supervision of Mr Behage.