by McKinley Conway
Breaking New Ground
Introduction (What did you do in the war Daddy? For many of us who have been negligent in documenting our WWII experiences, time is running out. Thus, we decided to write this report to answer questions now coming from our grandchildren.)
During the latter part of WWII a formation of naval training aircraft was returning to base in San Diego when a strange aircraft pulled up alongside. That was no big deal. Student pilots were accustomed to seeing odd things.
What was noteworthy was the concurrence among several reliable observers that the airplane was a single engine fighter type which was maintaining speed and altitude with its propeller feathered. The result was a string of stories told, spoofed, defended, embroidered, and retold among naval personnel throughout the region.
Some stories had the strange aircraft performing a variety of aerobatic maneuvers; others had it cruising inverted -- all with the propeller standing still. In any event, witnesses agreed that the pilot of the strange craft, after putting on a show, cranked up his engine and sped away, leaving a mystery that was not cleared up until after the war.
What the incredulous witnesses had seen was one of the first flights of the Ryan XFR-1 "Fireball" -- perhaps the most unusual airplane to come out of WWII.
Because of timing, the Ryan was also one of the least publicized new fighters of its time. An evaluation squadron was operating when the Japanese surrendered; no aircraft had gone into combat; and the production contract was canceled on VJ-day with only 66 units delivered.
Yet, the Ryan jet deserves a place in aeronautical history. It was the Navy's first fighter equipped with a jet engine and the first jet to operate on a carrier.
The Germans had flown an experimental land-based jet fighter, the Heinkel HE-178, in 1939. As news of this development reached Allied strategists the pressure was on to respond.
By 1941, the British got their first Gloster-Whittle land-based jet into the air. Soon the U.S. Army had an experimental land- based jet using the Whittle engine.
For the Navy, however, finding a suitable response was more difficult. The early jets required long runways and had very short range -- characteristics very unfavorable for carrier operations.
The answer from the Navy's Bureau of Aeronautics was a "composite" aircraft which would have two engines -- one a reciprocating engine driving a propeller, and the other a jet engine.
The concept was to take advantage of the best features of each power plant. The recip-prop unit would give satisfactory takeoff performance, while the jet would give speed at altitude.
An account of some of the events leading to development of the XFR-1 has been provided by William Wagner, long-time Ryan official who now assists the San Diego Aerospace Museum.
Wagner reports that in January, 1943, the Navy approved a sketchy plan by Ryan chief engineer Ben Salmon and work got underway. The task was to design and build, within months, an aircraft which could meet the Navy's criteria for carrier service -- including the small escort carriers being built at that time.
The airplane was designated the Ryan XFR-1 and was later given the name "Fireball". The first contract called for 3 experimental airplanes.
The first airplane entered flight testing in June, 1944. Concurrently, another airplane was flown to the NACA(1) Ames laboratory at Moffett Field, California for full-scale wind tunnel tests. These tests continued during 1945 and into 1946.
I was a project engineer assigned to the Ryan test program at Ames. In particular, I handled the work related to the power plant installations. I had just been transferred from NACA HQ in Washington where I had worked for several years with the committee on aircraft power plants and the new subcommittee on gas turbines.
This was an exciting time at the Ames lab. The new 40x80 foot tunnel was just being put into full operation. It was the biggest wind tunnel in the world, a huge structure covering an area bigger than a football field and towering some 12 stories high.
Adding to the excitement was the arrival of the new super-secret Ryan experimental aircraft. From the flight operations ramp the aircraft was towed to a hangar area inside the wind tunnel building. There, the manufacturer's representatives looked on anxiously as we drilled holes in their new airplane to install hundreds of wires, tubes, and other instrumentation.
A critical phase was getting the airplane into the wind tunnel test section. This was done by attaching a sling to the aircraft and lifting it via a giant crane more than 100 feet above the pavement, over the top of the wind tunnel test section, and down onto the support struts. These struts ran through the test section floor to scales which measured lift and drag.
The 40x80 was like most other wind tunnels in that it consisted of a duct which made a complete circle. In one large section were six 36 foot propellers driven by electric motors. At the test section where the airplane was mounted the cross-section reduced to 40x80 feet -- hence the name.
The Ames tunnel was one of only two capable of testing real airplanes rather than models. (The other was the older 30x60 tunnel at the Langley lab in Virginia). The Ames electric power requirements were so great that a substation in the building was connected directly to the grid from Grand Coulee dam.
When the wind tunnel motors were started, the tunnel operator had to be very careful to avoid a surge which would dim or black out every light in Sunnyvale, Mountain View, and the surrounding area. There was a notice posted on the control console which stated that any naval personnel responsible for such a blackout would be subject to court martial.
As a lowly Ensign, I read that with considerable trepidation.
And that was not the only hazard. The massive 40x80 structure had catwalks, ladders, and an impressive array of high-voltage lines in exposed copper busses. There had been several fatalities during the recently-completed construction.
At times, projects required someone to swing in a bosun's chair (a flimsy seat like a child's swing) several stories above the steel deck. Working in the test section we used vertical crank-up ladders which swayed drunkenly at the height of their extension.
The tunnel was designed to "fly" the test airplane using remote controls in a room under the test section. However, during the war there were test schedules which could best be met by having someone in the airplane.
That was an absolutely unique flying experience! A ladder lifted you up to the airplane, you climbed in, the ladder was removed and then the doors over the test section were closed. These were huge clam-shell doors weighing tons, and when they slammed shut you knew you were on your own.
With the XFR-1 our typical starting procedure was to bring the wind tunnel airstream up to about 150 miles per hour, get the propeller windmilling, then start the Wright R-1820 reciprocating engine. To reduce the fire hazard inside the tunnel we usually fed the engine in a test airplane from a special tank outside. For the XFR-1, there were two tanks, one for jet fuel and one for gasoline.
On one memorable occasion we got the valves switched. The Wright engine in the nose coughed and backfired while a spectacular tongue of flame spewed from the jet in the tail. I have often thought of the headlines that incident might have generated if the news media in those days had been able to scrutinize our operations as they do those of NASA today.
Actually, most test programs consisted of days of unexciting routine runs which involved methodical variations of airplane configuration, attitude, and power settings. These test runs might drone on for hours at a time. creating a problem with build-up of carbon monoxide in the air in the enclosed tunnel.
OSHA would never have approved our working conditions! You sat there, wearing an oxygen mask, sweating profusely, deafened by the roar of the engine bouncing off the steel walls of the test section -- thinking that if there was a fire or other mishap, no one could help.
Because it was such a vital wartime asset the 40x80 was operated 24 hours a day 7 days a week. Working in the tunnel at night was a memorable experience. When a test run was finished and the crew went into the test section to work on the airplane it was something like a ghostly movie set.
A bright circle from a battery of spotlights focused on the airplane but faded away to inky blackness in the big voids on either side. Noises were a bit like the sounds in the jungle at night. There were creaks, scrapes, and knocking noises as the giant shell expanded and contracted. Even the noise of a dropped screwdriver would echo around the chamber several times.
The overall program for the XFR-1 consisted of the normal aerodynamic clean-up tests plus some additional tests related to the jet power plant. The clean-up work measured the effect of air inlets, gun ports, antennas, and other protuberances required for a combat aircraft. The basic shape of the airplane had already been investigated via a series of 1/5 scale model tests in a smaller tunnel at Ames.
Another group of test runs examined the aileron control characteristics. For carrier-based aircraft the critical phase is the "wave off" when, just before touch-down, a pilot is waved off, applies full power and attempts to go around. Aircraft lacking sufficient aileron control tend to roll over and splash into the water.
Engine cooling is also a standard item on the test agenda. Assuming that the pilot applies full power for take-off and holds it there for five minutes, will the cylinder head temperatures go over the red line?
During its early years, the NACA organization had won a place in aeronautical history by developing the "NACA cowling" for radial engines. NACA wind tunnel tests showed that by simply putting a ring around the outside of the engine drag could be reduced substantially. More sophisticated designs accomplished even more.
This backlog of cowling test data proved invaluable when, in the course of our tests of the XFR-1, we got an urgent message that a new cowling design was needed.
It seems that a new wide-blade propeller with improved performance had been developed and Ryan wanted to use it. However, when the new prop was feathered it gouged about an inch of metal off the front of the old cowl. Within a few days we were able to provide a new shortened configuration which performed well.
The XFR-1 was, of course, the first jet-equipped airplane to be tested in a full-scale wind tunnel. Thus, we entered a new era with a series of tests which had never before been conducted.
Of particular concern were the wing air inlets. With jet engines, air inlet design is much more critical than with reciprocating engines. The efficiency and performance of the jet depends on maximum recovery of ram air pressure at the compressor inlet.
Also, we needed to explore the characteristics of the jet wake, which would be a new hazard on a crowded carrier deck. For these tests we strung cables across the tunnel behind the airplane and attached thermocouples to measure the temperature profile of the wake at various stations downstream.
At the same time, the new GE I-16 engine launched our education into the operating characteristics of a jet power plant. Remember that we are talking about an untested experimental design in its earliest stage.
The unit delivered to us had a static thrust of only 1600 pounds. Contrast this with current jet engines which deliver more than 50,000 pounds of thrust or the space shuttle boosters which provide several million pounds.
Moreover, the allowable time between overhauls for the I-16 was specified as 50 hours! And, it was necessary after each test run to run a feeler gauge around the tips of the turbine blades to see if any had stretched and started to rub on the casing.
We knew, from experience with turbines then being used in superchargers, that when a turbine wheel broke up it was like a bomb going off in the nacelle, with pieces of metal flying out in all directions. When we did run-up tests on the Ryan we did not stand alongside the turbine wheel!
Despite limitations, the Ryan was a prized research tool. We pounced on it to learn as much as we could from this new aeronautical marvel.
I was intrigued by the heat and velocity of the gases leaving the nozzle. Could this stream be used to vector thrust and control the airplane? Could a vane survive in the nozzle? Would there be a blockage affecting thrust or engine performance?
We had an opportunity to conduct a few crude tests to explore these questions. With the airplane moored outside under a return section of the wind tunnel we rigged a stainless steel vane across the nozzle for a short test run.
Two findings emerged quickly: we could indeed deflect the steam a significant amount -- enough to begin digging a hole in the ground; and, we had a metallurgical problem. The vane was easily deformed and eroded.
Shortly thereafter, I wrote a paper(2) outlining the possibility of controlling airplane flight path by propulsive jets. It gathered dust for years until the space age arrived.
Space vehicles, of course, adopted thrust vectoring from their origin, and, more recently, a variety of aircraft have adopted the concept. Looking back, this may have been the most important contributions of the XFR-1.
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