Bitter disappointment: The F-101 in SAC war plans

Yesterday's news reports of the publication of a declassified 1956 Strategic Air Command study of proposed targets has for many reasons already garnered worldwide notoriety.  The report may be viewed here at the National Security Archive: http://nsarchive.gwu.edu/nukevault/ebb538-Cold-War-Nuclear-Target-List-Declassified-First-Ever/

What has not been mentioned is that along with the B-47s, B-52s, and missile systems was SAC's strategic fighter of the future, the F-101A Voodoo.  By the time the study was commissioned in February 1956, the entire F-101 program was suffering multiple problems that would nearly lead to its cancellation.  While the pitch-up problem was garnering most of the headlines, its still-secret armament concept, the McDonnell Model 96 weapon-fuel pod, was causing tremendous problems of its own.  To this day, it remains virtually unknown even among those who otherwise know the Voodoo pretty well.  But this study illustrates what the F-101A weapon system was intended to accomplish in the event of a general nuclear war, a supersonic intruder using unimaginably powerful weapons to blow gaping breaches in Soviet defenses in front of streams of B-47 and B-52 bombers with the intent of utterly destroying the Soviet Union.  The scale of these SAC war plans for the late 1950s is mind-boggling, and it should give pause to both historians as well as those who today would propose the same mode of warfare against a different enemy.  This history serves as both a lesson and a warning.  It must never be revisited.  The following is a re-edited section from my recent book on the F-101, incorporating new information based on SAC Report SM 129-56: Atomic Weapons Requirements Study for 1959: 


Bitter disappointment: The F-101 in SAC war plans and the end of the Model 96

Still far above the fray as all hell began to break loose with the Voodoo and the strategic fighter concept in general, the Joint Chiefs of Staff commissioned a study of atomic weapons requirements for 1959 as SM 129-56 on 15 February 1956, published four months later on 15 June 1956.  Anticipating both new bomber and missile capabilities available to Strategic Air Command by that time, the study assessed and prioritized a burgeoning list of strategic targets within the Soviet Union and allied states.  Target categories for Strategic Air Command were: 1.) Soviet nuclear bomber, air defense, and tactical aircraft; 2.) air bases, launch sites and depots; 3.) atomic stockpile sites; 4.) military and government control centers; air industry and resources directly supporting enemy air capability.  Further strikes would be directed against Soviet population centers.  SAC medium and heavy bomber forces  in 1959 were projected to consist of 1,267 B-47, 225 RB-47, 495 B-52 aircraft, along with strategic missile forces consisting of 64 Snark ICCMs, 60 Rascal air-launched cruise missiles, 72 Crossbow missiles, and 180 IRBMs.  Aircraft payloads would consist of MK 6 B and MK 6 C fission weapons, MK 15 boosted fission and MK 27 thermonuclear weapons, forming the primary armament for the B-47 force.  High-yield MK 36 weapons would primarily be reserved for the B-52 force.  RB-47s were programmed for the MK 28 as primary armament, with the MK 27 as alternate.  

Also among the SAC assets directed against 3,400 projected targets, or Designated Ground Zeroes (DGZs) were a projected 150 F-101A Voodoo strategic fighters by 1959, enough to equip two combat wings.  Given the relatively short range and earliest arrival of forward-based F-101A strategic fighters, their primary targets would have consisted of Soviet fighter and interceptor bases and air defense sites, although a handful of forward bomber bases would also be within range.  As listed in SM 129-56, the primary weapon for the F-101A was to be the MK 28 bomb, with the MK 27 as an alternate weapon.  Unlike the lower-yield MK 28-Y2 versions slated for other nuclear-capable fighters like the F-100D and F-105, as a SAC aircraft the F-101A would carry the more powerful MK 28-Y1 producing 1.1 megatons yield, ten times the destructive power of the W-5 weapon that the Voodoo had been redesigned to carry a few short years previously.  The MK 27, slated as a primary weapon for both the B-47 and the Rascal air-launched cruise missile, had a yield of 2 megatons.  Against airfield targets, ground burst was specified to maximize blast radius, ensure the collapse and destruction of any underground facilities, crater runways, and produce enough heavy local fallout to prohibit repair or use of the target.  Under visual delivery conditions, the expected accuracy for the F-101A was a Circular Error Probable (CEP) of 600 feet.  The unparalleled combination of fighter speed and megaton-level punch of the F-101A constituted an extremely formidable weapon in the hands of SAC planners.  But as the report was being written, it was all becoming for naught.

Model 96 LABS and “Over-the-shoulder” delivery flight paths.  When this study was published on 22 June 1954, the 100-kiloton W-5 fission weapon was the planned payload for the Model 96 store, along with 849 gallons of fuel.  With the rapid development of lightweight, small-diameter hydrogen bombs, by early 1956 the 1.1 megaton MK 28 was slated as the primary weapon for the F-101A by 1959, with the larger and more powerful W-27 warhead earmarked for carriage in a modified Model 96 pod.  This would have made the Voodoo by far the most heavily armed fighter aircraft ever conceived.   Department of Energy.

By the beginning of 1956, McDonnell had more pod concepts on the drawing boards, but flight test of the F-101/Model 96 combination was continuing to reveal serious problems.  By this time, F-101As had arrived at Kirtland AFB, NM and were undergoing flight testing with the 4925^th Test Group (Atomic), including 53-2441.   McDonnell had developed two new electronic warfare versions of the Model 102 store, with formal design work beginning in November 1955, both retaining the original shape of the Model 96 store.  The Model 102H contained both fuel and electronic countermeasures equipment.  Interchangeable nose and tail assemblies were available, containing AN/ALT-6, AN/ALT-7, and/or AN/ALT-8 “noise” jammers, and an 11-carton capacity AN/ALE-1 chaff dispenser.  The Model 102J store was not provided with jamming equipment, instead carrying 943 gallons of fuel along with an ALE-1 chaff dispenser with 20 cartons capacity.  These were followed in March of 1956 when work began on a new design, the Model 117A store.  Intended for both the F-101 and RF-101, the newer pod could contain various combinations of ALT-6B and ALT-8B dispensers along with an ALE-1 unit with a 20-carton capacity.  Unlike the previous designs, the Model 117A apparently did not contain fuel.  The equipment in these pods were standard for SAC B-47B-II and B-47E-II Stratojet aircraft that were upgraded with Phase III ECM equipment beginning in late 1954.  By the beginning of 1956, SAC had made the decision to get out of the fighter business and would begin to deactivate its existing strategic fighter units.  Given the change in mission and the forthcoming “Blue Cradle” EB-47E aircraft with Phase IV ECM to provide escort jamming support for the bombers, and the fact that the equipment was not standard for TAC (which in any case considered electronic countermeasures of little importance) work on these new ECM stores for the F-101 would eventually be cancelled.

JF-101A 53-2427 with the Model 96.  The final warhead considered was the XW-27 hydrogen weapon, much improved over the earlier and heavier TX-15 boosted-fission design.  With a yield of two megatons, the XW-27 / Model 96 would have made the F-101A by far the most heavily-armed fighter ever to enter service.  Instead, the development of this vital component of the WS-105A strategic weapon system stalled and it was never deployed.  Gerald Balzer Collection, Greater St. Louis Air & Space Museum.

Unfortunately, it was becoming clear that the problems of the Model 96 store on the F-101 were nowhere near being solved.  In addition to the continuing deficiencies in both directional and lateral stability, another serious problem cropped up during testing.  The Model 96 shape added a great deal of cross-sectional area to the forward and middle of the aircraft, with a sharp drop-off in cross sectional area aft of the wing.  Under the recently discovered “Area Rule”, this sharp discontinuity in the area distribution would have led to higher than anticipated transonic drag.  Given that the F-101 cruised and fought in the transonic region, this increased drag resulted in a reduction in mission radius and increased buffeting and associated control problems at altitude. 

JF-101A 53-2428, the second “special weapon” test aircraft, at Lambert Field with a T-63 training “shape” for the MK 7 fission weapon.  Both the T-63 shape and lower and aft fuselage of the Voodoo are tufted for flow studies. Gerald Balzer Collection, Greater St. Louis Air & Space Museum.

In January 1955, the Air Force Special Weapons Center (AFSWC) stated that application of the thermonuclear XW-27 warhead to the Model 96 appeared feasible. With regard to the payload of the Model 96 store, word came down that major structural changes would be necessary for the Model 96 to accommodate the XW-27 warhead.  Meanwhile, the W-5 warhead that the Model 96 was built to carry was already obsolete as smaller, lighter, and higher-yield weapons such as the MK 28 were on the horizon.  These smaller weapons would offer at least as much yield as the Model 96 with negligible aerodynamic effects on the F-101 and, due to decreased weight and drag penalty, a similar combat radius when carrying one centerline weapon with two 450-gallon fuel tanks.  Seeing rapidly diminishing returns ahead for continued development of the F-101/Model 96 combination, the XW-5/F-101 and XW-27/F-101 programs were canceled in March 1956 in favor of future integration with the MK 28.  In the interim, the F-101 would make do with the relatively puny MK 7 weapons used by the F-84 once the Voodoo became operational with SAC strategic fighter wings.  The upshot was that, while the F-101A remained useful for the nuclear delivery mission, it lacked the needed range and strategic-level “punch” that had been expected of the high-yield warheads to be accommodated in the Model 96 store.  As with the air superiority mission, the F-101 was now unable to fulfill the anticipated vision of the “strategic fighter”.  This meant that even before SM 129-56 was published in June 1956, the targeteers of Strategic Air Command had to go back to the drawing board to account for a strategic fighter that now appeared completely useless for its apocalyptic mission.

"Zip" Fuels: the F-101 and Research on Borane Fuels

Last week saw the celebration of the 61st anniversary of the first flight of the F-101 Voodoo, on 29 September 1954.  Ship No.1, 53-2418, had a very interesting career after initial flight testing.  She was soon "bailed" to General Electric for tests with their new J79 engine, then under final stages of development for the Convair B-58A Hustler and Lockheed F-104A Starfighter.  Due in part to the persistent compressor stalls encountered with the Pratt & Whitney J57-P-13 engines, the J79 garnered considerable interest from McDonnell for developed versions of the Voodoo.  While it did not offer the fuel efficiency of the standard Pratt & Whitney engine, the J79 produced more thrust from a lighter engine and, most importantly, was free of compressor stalls, even with the initial Type I inlets that had caused so much grief for both the Air Force and McDonnell from its first flight.  But as the J79 began to mature into an established engine, General Electric was already at work on a very advanced derivative, the much larger J93 engine intended for the North American B-70 Valkyrie bomber.  Initial flight testing would take place with the J93-GE-3 engine, using hydrocarbon fuel.  Six of these engines would propel the massive stainless steel bomber to speeds of over Mach 3.  But design work proceeded on another version, the J93-GE-5, using a completely new, synthetic type of fuel that was so volatile it did not exist in nature.  Rather than using petroleum-based hydrocarbon fuel, the new fuel was composed of a class of chemicals called boranes.  Ground testing, in cooperation with the NACA, began in the mid-1950s using a modified J47 engine as a testbed.  But by 1957, the time had come to begin planning for flight testing of modified engines with the new fuel.  Given that the J93 was essentially a scaled-up J79 engine, the twin-engine General Electric Voodoo was selected for those historic tests.  Below is the rest of the story:

Ship No. 1,  bailed to General Electric and carrying modified YJ79 engines, conducting the first-ever powered flight using high-energy borane “zip” fuel on 28 September 1958. Gerald Balzer Collection, Greater St. Louis Air & Space Museum.

Pursuant to the 21 June 1955 request for a study of the J79 engine for the Voodoo, Ship No. 1, 53-2418, was bailed to General Electric in 1956 and modified with a pair of YJ79 engines in place of its Pratt & Whitney J57s.  The keel area was reworked to accommodate the new engines and the intakes were modified with longer ramps.  53-2418 first flew with theYJ79 installation on 3 November 1956 with an initial fit of two YJ79 Phase 0 engines.  Later that year, the NF-101A was modified with improved YJ79 Phase I engines modified with the Basket Burner Test Package and the Parker afterburner selector valve.  During its service with G.E., the aircraft also flew with YJ79-GE-3 and YJ79-GE-7 engines.  In 1958, 53-2418 became the first aircraft to flight test exotic borane-based high-energy “zip” fuel (HEF). This was done as an adjunct to the General Electric J93-GE-5 program.  The J93 was an enlarged derivative of the J79 intended for use with the B-70 Valkyrie and F-108 Rapier.  The kerosene-fueled J93-GE-3 made it to the hardware stage and was extensively flight-tested on the XB-70.  Waiting on the drawing boards was the J93-GE-5 engine, substituting borane compounds for traditional hydrocarbon compounds as fuel.

Instrument panel of 53-2418 on 2 October 1958.  The master switch for the borane fuel supply can be seen on the upper right, marked "HEF". Gerald Balzer Collection, Greater St. Louis Air & Space Museum.

Borane fuels were the focus of a great deal of research in the 1950s, with hundreds of millions of dollars quietly spent on their development.  These materials reacted with oxygen like traditional hydrocarbon fuels, but offered nearly twice the energy for the same weight of fuel.  In theory, an airplane using these fuels would need to expend less fuel to produce a given amount of thrust, resulting in greatly increased range.  This made borane fuel an extremely attractive option for the B-70, a six-engine, Mach 3-capable aircraft that required intercontinental range without refueling.  However, there were very serious drawbacks to the use of boranes as a practical fuel.  Besides being extremely toxic, boranes are also extremely reactive.  The same qualities that make them an excellent fuel also explain why they do not exist in nature—chemically, they are very unstable.  Boranes have to be synthesized, a very expensive process.  Diborane, the basic building block of all other borane compounds, is a gas that combusts simply on exposure to air at normal temperatures and pressures.  Pentaborane, a liquid, spontaneously combusts at temperatures above 78°F and was itself too unsafe to use as a practical fuel.  Decaborane, which is stable at normal operating temperatures, received serious attention from researchers as both a jet and rocket fuel, but is a solid at room temperature.  Decaborane could be added to the air mixture of a turbine engine as a fine dust or mixed with a hydrocarbon liquid such as benzene.  Unfortunately, the combustion products of borane fuels form a highly corrosive mixture of boric anhydride and water as well as extremely refractory deposits of boron carbide. (Slightly less hard than diamond, boron carbide is presently used as an industrial abrasive and has been used for cockpit armor on the Ling-Temco-Vought A-7D Corsair II).  Injecting borane fuel into the combustion chambers of a turbojet would soon result in a wrecked engine.

In order to be usable, boranes had to be injected into the afterburner section, well behind the more delicate engine components.  This was the arrangement planned for the J93-GE-5.  Borane fuels were flight-tested with this configuration for the first time on 28 September 1958, using the NF-101A with modified J79 engines as the test bed.  The flight tests themselves were successful, but the borate deposits left in the nozzle and afterburner section seriously degraded the usable life of the engines.  Also, the borane fuel produced a great deal of smoke, enough for some to judge it as being impractical and to be potentially unsafe during takeoff.  Despite the promise of borane fuels, their benefits were greatly outweighed by safety concerns and by production and maintenance costs.  Although not an important consideration in the late 1950s, widespread use of these fuels with their acidic combustion products could have also posed significant environmental problems.  One borane compound, triethylborane (TEB) found use as a catalyst for the ignition of the high-flashpoint JP-7 fuel of the SR-71.  The Department of Defense abandoned work on the J93-GE-5 in 1959, in large part due to the results of the flight test work performed by the NF-101A.  However, general research on borane fuels continued for some time afterwards.

By May of 1959, the NF-101A had had its J79 engines removed before the open house at Edwards AFB that year.  Thus, the unwanted and little-heralded Voodoo played an integral part in what had once been thought one of the most important and promising research programs of the Cold War.  Fortunately, this historic aircraft has been preserved.  After the J79 installation was removed, 53-2418 was moved in 1960 to Amarillo AFB Technical Training Center and used as a hydraulics trainer until placed on stands outside of the base as a “gate guard”.  With the closure of the base in 1970, the aircraft was later sold as excess property and purchased by Mr. Dennis E. Kelsey in February 1975.  After residing on the grounds of Bell Helicopter Co., 53-2418 was issued FAA Number N9250Z on 7 April 1976 and moved to Pueblo, Colorado on 11 January 1977.   At this writing, 53-2418 has been moved from Pueblo and after extensive restoration work has been on display at the Evergreen Aviation and Space Museum in McMinniville, Oregon since 2013.

A Story of the Stratotanker

Today marks the first flight of the famed Boeing KC-135 Stratotanker on 31 August 1956.  By the following spring, the USAF had a grand total of two KC-135A aerial tankers in its inventory, one based at Edwards AFB and one at Wright-Patterson AFB, Ohio.  By then, the Navy was preparing an attempt on the Los Angeles-to-New York transcontinental speed record with the impressive new Vought F8U Crusader.  The Air Force planned its attempt for the latter part of 1957 to coincide with the 50th anniversary of the establishment of the Aeronautical Division of the Army Signal Corps in August 1907.  The record attempt would be flown by factory fresh RF-101C aircraft assigned to the 432nd Tactical Reconnaissance Group, which had higher fuel capacity and extended afterburner time compared to the existing RF-101A Voodoo.  Success would depend on the jet speeds and high-altitude refueling capability of the new Stratotanker versus existing piston-engine KB-50 and KC-97 aircraft.

RF-101C 56-0166, the first aircraft to launch for the transcontinental record attempt, at Ontario Airport in southern California just before its early morning departure to NAS Floyd Bennett in New York.  The Schrecengost Archives of the late Col. Ray W. Schrecengost, Jr., USAF.

In May 1957, USAF test pilot Maj. Austin A. "Gus" Julian was tasked to fly a Voodoo from Edwards AFB to the McDonnell factory at Lambert Field in St. Louis, Missouri, taking fuel from both of the Air Force's test KC-135A tankers to test and develop procedures for the ultimate record attempt.  On the morning of 27 May 1957, Gus Julian departed from Edwards AFB and headed east toward the first tanker rendezvous point.  In 2012, he related to me the hair-raising story of his flight:

The fuel system had a lot to be desired in the original F-101.  As I said, you have five tanks, strung out along the fuselage and all feeding out to number 1 to the engines.  I remember an incident I had where TAC was setting up an operation they called SUN-RUN, it was a [speed run from] California to [New York].  I was told to see what I could do with the airplane.  So, I set it up to go from Edwards to McDonnell, and was going to use the [new KC-135] for in-flight refueling.  Now up to that time, we had never used [“flying-boom”] refueling, even during Phase VI because, mainly, we didn’t have any tankers.  [Production KC-135 tankers would not be delivered until late summer of 1957.]  The Air Force had kept the first two tankers, one of them at Wright Field, one at Edwards. 

Refueling boom operating limits for KC-135 / RF-101. USAF.

So, using the tanker from Edwards, I took the F-101 and stabbed the tanker about a dozen or so times.  The receptacle was aft of me, over my head.  So, on that day we took off, and my plan was to refuel first over Santa Fe, use the Wright Field tanker over Wichita then on into St. Louis.  But when I took off, the weather was bad over Santa Fe.  Now, normally, you’d drop down to 15 or 20,000 feet to refuel, you would get a better flow rate down there.  But, the weather was over Santa Fe.  Joe Gandy was flying the tanker, so I said to him, “Well, let’s try it.”  I got on to the tanker at 39,000 feet (chuckle) and got a load of fuel.  Now, in that particular airplane, one of the first production airplanes, they had an extra 100-gallon tank in it.  I got 12,000 pounds of fuel and was using one burner, just cracking in to stay on there, but I eventually fell off.  Well, I had enough fuel to continue.  

So the next leg was in burner, going downhill, where I pulled in on the Wright Field tanker, oh, around Wichita.  I had a ready light to get fuel but…I couldn’t take any fuel, and there was a broken overcast below us.  I had now run out of fuel and now I am down to that 100 gallons on those two big J57 engines, or so I thought, so we turned back into Wichita.  But I switched over to the 100 gallon to come to find out that in actuality something had happened up there to siphon it all out.  So that’s what made it so binding to get back into Wichita in through that overcast.  I let down through the overcast and on a high base leg, at Wichita, and shut one engine down as I let down, but I fired up just as I was rounding out for touchdown and flamed out on the rollout.  Come to find out later that when I’d fell off that tanker, I’d practically ripped the receptacle right out of the airplane.  So, we didn’t go on to St. Louis. 

Detail of boom refueling receptacle. USAF.

I spent the night there in Wichita and then I was going to go back to talk to Col. Hanes and bring the airplane back to Edwards.  I knew that I had been running in burner quite a bit, and I needed oil.  Well, it was a new airplane and the only other place that knew how to service the airplane was another Systems Command base which was down in Albuquerque [Kirtland AFB].  So, the next morning, thinking about those Schutz valves, before take-off I’d get up on the wing with a chock and beat along where the valves were (chuckle) under the skin to make sure they were working.  I went down to Albuquerque and landed there.  That’s where I knew I could get fuel and that they knew how to put oil in the thing there.  So, this was Memorial Day, and, of course, the Indy 500 was going on. 

Well, I got up that morning, there was not a cloud in the sky, got up on the wing and beat on the Schutz valves, and took off.  Well, right about over where the big crater is in Arizona [Winslow], I glanced down at my left and saw two great big red lights…a double hydraulic failure.  Well, this is not supposed to happen!  But I remembered that, according to the McDonnell engineers, they had told me that this couldn’t happen but in the event it did, that the last 1500 to 1600 pounds of hydraulic pressure that was trapped in the system could get the gear down.  At about the same time I discovered, also, that my Schutz valves had stopped up and nothing was feeding in to the main fuel tank.  So here I was sucking fuel out of that No.1 tank, which was only being refueled by gravity feed, just barely enough to get on and I was really watching that, so I had to have C.G. on the airplane, I had to contend with that on the letdown, too.  Well, I wiggled the stick and got a little bit of response from it so, I figured, I might as well keep heading west.  I was going to go on to home as far as I could to Edwards and then punch out.  Anyway, I eased that airplane around very gingerly, and I contacted the tower from somewhere over Barstow, eased around to up to the north of the base, got it headed south at 20,000 feet, and then I dropped the gear.  Sure enough, that thing froze up just solid as a rock.  About five…seven seconds, seemed like seven hours….but the gear came down.  Anyway, I got the airplane on the ground and Iven Kincheloe and Danny [Lt. Col. Boyd L.] Grubaugh met me there at Edwards. 

It was a holiday and I went home, and now lived next door to Kincheloe.  Kinch was going to get married pretty soon, so, I told him about the flight for the two days, and how many times I’d had my hands on that “Next of Kin” handle and thinking about bailing out. As I got through, my wife came out and said, “Now let me tell you what happened while you were gone.  One of the kids mashed his finger in the refrigerator!”  But Kinch thought he was going to get married in the next couple of weeks.  Anyway, she went back in the house and Grubaugh, shaking his head, he said to Kinch, “And you still want to get married?”

Regrettably, Gus Julian was never to see the final edition of the book, although he did receive a "paste-up" copy that I had prepared in the spring of 2013.  He passed away on November 13, 2013.  God bless you, sir, and thank you for everything.

Supersonic Propeller Research: The XF-88B Voodoo

Into the early 1950s, both the Air Force and the NACA had maintained a continuing interest in high-performance turboprop aircraft.  NACA was interested in flight testing new supersonic propeller designs that would overcome the thrust limitations of conventional propellers at high subsonic speeds while the Air Force, still faced with the problems of high fuel efficiency and range for both future intercontinental bombers and potential escort fighters, made investments into parallel programs exploring and developing the technology.  Up to that point, conventional propeller designs were restricted to a maximum flight speed of about Mach 0.725.  The goal was to develop an engine-propeller combination that would be capable of sustained speeds of Mach 0.95.

By late 1951, the Boeing XB-52 was preparing for its maiden flight under the power of eight of the new J57 power plants.  Although offering a clear performance advantage over the turboprop engines that had originally been envisioned, many in the Air Force remained skeptical that the turbojet-powered B-52 would meet its very ambitious cruise performance figures.  Meanwhile, the hybrid power plant arrangement of the Consolidated-Vultee XP-81 remained attractive for both escort fighters and strike fighters.  During 1951, the Air Force signed a contract with Republic Aviation for what would become the XF-84H.  In the meantime, both the Air Force and contractors would need flight performance data to work with to pursue any future developments.

On 25 July 1949, McDonnell began detail design of a turboprop research airplane to be converted from XF-88 No. 1 under Contract AF33 (038)-7442.  The airplane would be modified with the installation of a 2,500-horsepower Allison T-38 Model 501 F-1 engine in the nose as the McDonnell Model 36J.  The modification program was delayed with the crash of the XF-88A and the need for the first aircraft to stand in during the penetration fighter evaluation.  Restricted funding meant that both XF-88s remained tied down and in storage from the summer of 1950.  Funding for the conversion was finally released in February 1952 to begin installation of the Allison XT-38A-5 turboprop into 46-525 as the XF-88B.  The XF-88 was removed from storage at the end of March and readied for conversion by the beginning of June.  Conversion work commenced in August 1952 and continued into the winter of 1953.

Modified nose structure of XF-88 46-525 prior to installation of the Allison XT-38-A-5 turboprop engine. Gerald Balzer Collection, Greater St. Louis Air & Space Museum.

The Allison XT38-A-5 turbobprop engine during NACA flight testing.  The “rake” arms projecting from either side were not present in the original engine installation.  Jack Reeder Archive, NASA.

1953 photo of original Curtiss Phase I 4-bladed propeller mounted on the XF-88B. Gerald Balzer Collection, Greater St. Louis Air & Space Museum.

By February 1953, the conversion had been completed.  In addition to the new Allison turboprop, the XF-88B was now equipped with J34-WE-34 engines, retaining the McDonnell afterburners of the earlier J34-WE-15 engines.  With the new nose fuselage, the XF-88B was 58 feet long.  A forerunner of the later T-56 turboprop, the Allison XT-38A-5 turboprop engine could produce propeller rotational speeds of 1,700 rpm, 3,600 rpm, and 6,000 rpm using three interchangeable gearboxes.  Curtiss would provide the twelve different research propellers that had been envisioned for flight testing, although as it would turn out only three other propeller designs would be tested over the course of the NACA evaluation; the Phase Va, Phase Vb, and Phase VIIb variants.  The maximum propeller diameter that could be accommodated was 10 feet, consistent with the Phase Vb design.  As built, the XF-88B had a long, conical spinner and a four-bladed Curtiss Phase I propeller.  On 16 February, the XT-38A-5 engine was run up for the first time during a 29-minute ground run.  Two months later, on 14 April 1953, the XF-88B made its first flight from Lambert Field under the power of its J34 turbojets with McDonnell test pilot Philip Houghton at the controls. The XT-38 engine was not started in flight, with the first air-start occurring on the fourth flight.  An abbreviated series of shakedown flights were flown by McDonnell prior to a brief evaluation by USAF and NACA pilots from 23 June 1953.  Capt. John Fitzpatrick flew the USAF acceptance flights and would ferry the aircraft to Langley via Wright Field, while John P. “Jack” Reeder, one of the two NACA project pilots, flew three familiarization flights on 30 June and 1 July 1953.  After the conclusion of this initial evaluation, the XF-88B was ferried to the NACA facility at Langley, Virginia for further evaluation and development work, arriving at Langley AFB on 13 July 1953.  By this point, 46-525 had conducted 188 flights for a total of 142.5 hours.  The first public announcement of the XF-88B supersonic propeller test bed was made on 4 July 1953.

Ground run of XT-38A engine in XF-88B.  Art Davies, Jr. Collection, Greater St. Louis Air & Space Museum.

XF-88B in the air with feathered propeller, during an early McDonnell test flight. Gerald Balzer Collection, Greater St. Louis Air & Space Museum.

NACA Project Pilot Jack Reeder (L) and McDonnell pilot Phil Houghton (R) during acceptance testing of the XF-88B at Lambert Field in late June 1953.  Jack Reeder Archive, NASA.

Handover of XF-88B to NACA personnel at Lambert Field.  From left to right: Project Engineer Jerry Hammack NACA, Art Vogeley NACA, Capt. John Fitzpatrick USAF, Jack King USAF, Project Pilot John  P. Reeder NACA, Project Pilot William L. Alford NACA and Gene Smith NACA. Gerald Balzer Collection, Greater St. Louis Air & Space Museum.

Once the XF-88B arrived at NACA Langley, the aircraft was statically tested before undergoing further modification.  With the original Curtiss Phase I propeller still installed, sound levels were checked and recorded to provide a baseline to compare future supersonic propeller designs with.  NACA test pilots Jack Reeder and William L. “Bill” Alford were assigned as the project pilots for the XF-88B.  The first NACA research flight of the XF-88B took place on 20 November 1953.  In the first series of flights, the XF-88B tested non-rotating “dummy” spinner configurations without blades in order to determine their true aerodynamic characteristics.  The original conical spinner was compared against two “spherical” spinner designs, one with a 45-degree cone and the other with a 60-degree cone.  The 60-degree spinner was selected for subsequent testing by the NACA.  The 60-degree design appeared rather ungainly-looking, but provided suitable flow conditions for the thin, three-bladed, low-aspect ratio Phase Va supersonic propeller to produce section Mach numbers in the region of Mach 1.5.  In this configuration, the spinner contour was formed by a 17.5-inch sphere faired into a 60-degree included angle conical nose section.  The propeller blades were constructed of SAE 4340 steel using a NACA 16-series section varying from 8-percent to 2-percent thickness. Each blade measured 11.1 inches in chord at the spinner surface and 8.4 inches at the tip.  The entire propeller was 7.2 feet in diameter.  Used with the 3,600 rpm gearbox, the Phase Va propeller produced a tip speed of Mach. 1.7 and a design flight speed of Mach 0.95.  Speeds of up to Mach 1.01 were attained by the XF-88B during the course of testing, although during acceptance evaluation at McDonnell the previous June, Capt. Fitzpatrick reached speeds of up to Mach 1.2 which resulted in considerable complaint from residents in and around St. Louis.  While the propeller itself performed well, on the ground it produced noise levels in excess of 130 decibels, measured at 100 feet from the aircraft during static tests.  Flight testing at NACA Langley continued through 1957.

Test instrumentation for the XF-88B during NACA flight testing.  Jack Reeder Archive, NASA.

The XF-88B after modification with the new 60-degree spherical spinner and Curtiss Phase Va blades.  Used with the 3600 rpm gearbox for the Allison XT38-A-5 turboprop, the combination produced propeller tip speeds of Mach 1.7.  Jack Reeder Archive, NASA.

NACA pilot Jack Reeder climbing into the cockpit of the Phase Va-equipped XF-88B, possibly on the occasion of its first NACA research flight on 20 November 1953.  Jack Reeder Archive, NASA.

In an attempt to attain the desired Mach 0.95 design point and reduce noise levels to a range comparable with that of conventional propellers, the XF-88B was tested with a new supersonic propeller design mated with the conical spinner, the Phase Vb.  A four-blade design that would have been ten feet in diameter, it was tested in a three-blade configuration that was 9.8 feet in diameter and optimized for the same flight speed of Mach 0.95 as the preceding Phase Va blade design.  Also using a NACA 16-series section and SAE 4340 steel construction, the new blades varied in section thickness from 8-percent at the root to 2-percent at the tip.  Blade chord was 16.1 inches at the spinner surface and 11.6 inches at the tip.  The conical spinner had a base radius of 17.5 inches and had an included nose angle of 41 degrees.  In this configuration, the propeller operated at 1,710 rpm.  Despite the greater length and similar overall configuration to the preceding Phase Va blade design, the slower rotational rate of the 1,700 rpm gearbox produced a tip speed of Mach 1.3 for the Phase Vb blades.  This reduced rotational speed greatly aided noise reduction efforts.  These tests continued into the early summer of 1957.  Final tests with the Phase Va blades used a new non-rotating elliptical spinner16.57 inches in diameter and 55.1 inches long to evaluate flow conditions and result in less interference with the propeller.  As with the other configurations tested, both the propeller designs and the XF-88B gave good results.  However, the noise and vibration produced by the supersonic propellers was often difficult for ground personnel to endure.

An attempt to overcome the very high noise levels of previous propeller designs was tested in the XF-88B with the elliptical spinner matched to a new transonic blade design, the Phase VIIb, which was 6.85 feet in diameter and optimized for a lower flight speed of Mach 0.82.  As with the Phase Vb propeller, the Phase VIIb used the 1,700 rpm gearbox for the Allison turboprop engine.  With a tip speed of Mach 1.1, the new design provided a modest decrease in noise levels but also exhibited reduced efficiency. 

In a 6 January 1981 letter to author Richard Koehnen, Jack Reeder offered his recollection of the XF-88B program:

The supersonic propeller program was a joint effort of the Air Force, Navy, and NACA to explore the design and practicability of propellers for economic propulsion of aircraft to cruise at Mach numbers of up to 0.95.  The NACA considered both the B-45 and B-47 as candidate test beds, but the Air Force volunteered the XF-88 number 46-525, which was excess to their needs, and this was modified to become the XF-88B.  The Air Force contributed the required modifications to the aircraft (a 62-gallon fuselage fuel tank was removed for installation of the T-38 power plant), a conventional 4-blade propeller (Curtiss) and the research propellers (built by Curtiss to the requirements of the NACA research program), the propeller gearbox and a spare, which could accommodate three propeller rotational speeds through internal gear changes, whirl tests of the research propellers at WPAFB and acceptance tests and reports of the modifications accomplished.  The Air Force Project manager at WPAFB was Charles Beinnaman.

The Navy contributed the engines to the program.  These included two Allison XT38-A-5 turboprop engines (one spare) to drive the propellers, and four Westinghouse J34-WE-34 jet engines (two of these were in the XF-88A [sic?] airframe.  The afterburners were of McDonnell design.

The NACA was responsible for the research instrumentation, the program and its conduct, the data and reporting of research results.

Acceptance tests were conducted by the Air Force after aircraft modifications at McDonnell in June and early July of 1953.  NACA personnel were in attendance to take part and for familiarization with the final product including flight and operating characteristics of the aircraft…. 

The XT-38 drive shaft and gear box had torque and thrust sensors, respectively.  The thrust meter did not function well and was not used.  The torque meter strain gauges were on the shaft between engine and gear box.  The actual torque absorbed by the propeller was, however, determined from the wake survey rake as was the thrust.  Although provisions for the research instrumentation were made during the conversion work on the aircraft, the actual installation (including the momentum survey rakes) was completed after delivery to NACA Langley.

The XF-88B was ferried, after acceptance, by Capt. Fitzpatrick to Langley with a stopover at WPAFB where it was flown by other Air Force personnel.  It arrived at Langley on July 13, 1953.  The XF-88A, number 46-526, was later delivered to NACA Langley, also, where it served for spare engine and parts support….

In research like this a great deal of work goes on between flights to reduce and examine data so as to decide what should be done on the next flight, and what changes and corrections must be made to the instrumentation, propellers, and propeller governing, gear boxes, etc., as well as to perform required maintenance on the one-of-a-kind equipment from airplane to propellers.  The research proceeds slowly, but not because of a lack of effort.

The XF-88A, which had an all-moving horizontal tail, in contrast to the fixed stabilizer and elevator of the XF-88B, was not flown by NACA because of lack of resources for operating both aircraft.  It was used for spare engines and airframe spares, primarily.  However, the aircraft was used briefly for evaluating a takeoff performance meter concept, but no lift offs were made.  Taking account of weight, temperature, and runway length the takeoff meter indicated whether, upon brake release, the longitudinal acceleration was adequate for safe takeoff under the prevailing conditions. 

When acquired, the XT-38’s were limited to 25 hours before scheduled overhaul, but before such time was acquired it had been extended to 50 hours.  However, at between 6-7 hours of operation foreign object damage was suffered which required compressor blade replacements....  Of course, the spare engine was installed while repairs were made on the first engine.  It’s not surprising that foreign object damage did occur because of the numerous and lengthy ground runs for noise measurements and the vulnerable position of the XT-38 engine air intake. 

The XT-38 propeller gear box ratios for 1700 and 3600 rpm were used in the research, but not that for the 6,000 rpm.  A disintegration of the propeller brake (for-feathered operation) required rebuilding of one gearbox.  Only three propeller blade designs were flown and reported on, the phases Va, Vb and VIIb….  The program was discontinued when it was felt that maximum payoff had been achieved.  An important factor was the rapid swing to jet power (with its speed and productivity potential) for military and commercial use.  Actually, the program was a little late, for the times, in implementation.

The XF-88B aircraft performance for this testbed role was marginal.  Thrust-to-weight ratio for takeoff was 0.3 or less.  Takeoff run, with afterburning, to 155 mph was generally 5000 feet or more (8000-foot runway at Langley at that time).  Fuel limitations with the performance prevailing made the whole operation time critical.  Flight time could not exceed 40 minutes, and usually only one high speed run at altitude could be achieved.  As soon as familiarity was achieved the XT-38 was started at 5000 feet (blade stall flutter was a limitation for takeoff) and the test propeller configuration was used for climb.  Engine nozzles in non-afterburner operation were manually adjusted by rheostats in the cockpit for maximum temperature to obtain military thrust, which was the power used in climb.  Sometimes at full throttle the nozzles would not close in response to rheostat adjustment until the throttles were retarded.  Then they could be advanced again.

The afterburners did not perform satisfactorily.  The thrust augmentation with afterburning was estimated to be about 1.41 in design.  However, ground static tests at Langley assured only 1.12 to 1.19 in actuality.  Furthermore, the tailpipe nozzles, automatically controlled by temperature in afterburning operation, would frequently hunt, causing large fluctuations in thrust which damped poorly or not at all.  The problem lay in the friction in the Arends’ controls (flexible wire enclosed in flexible, anchored guide tubes) used to move the nozzles and did not seem to be amenable, for any length of time, to maintenance steps or lubrication.  Afterburning light off could not reliably be achieved above 20,000 feet, if used.  However, blowout of one or both afterburners frequently occurred above 20,000 to 25,000 feet.  This was hard to detect at times, and a rapid loss of fuel would occur before recognition.  Re-lights were not generally possible without descending.  We eventually did away with the afterburners and replaced them with straight tailpipes.

The aircraft was usually towed to the head of the runway where assurance of prompt takeoff clearance was obtained before engines were started.  Engines were run up with the brakes on and turbine outlet temperature limits set with the cockpit rheostats.  Generally, both afterburners were lit, one at a time, and checked for temperature and steady operation before brake release.  However, one day I was startled by the aircraft sliding down the runway.  I thought the brakes weren't holding.  Actually, the afterburners were putting out their best.  After takeoff, the afterburners were shut down as soon as 230 mph in the clean configuration was obtained.  The XT-38 was started at 5,000 feet and 250 mph and used in climb.  During all operation with the propellers the cockpit noise was similar to that with a reciprocating engine, such as the Merlin or the Allison.  Climb was made with the aircraft position with respect to the airbase in mind so that, when the fuel state dictated, the data run could be started with the aircraft heading toward home.

For a speed over about Mach 0.85, the climb was continued to as high an altitude as the fuel state would permit, generally 30-35,000 feet.  The highest altitude obtained during the NACA program was 39,000 feet over Wallops Flight Center during an airspeed static source calibration using ground radar.  At the highest altitude achieved for a test run the aircraft was accelerated in level flight, data system running, as long as practical.  It was then dived to obtain the speed desired by 30,000 feet, if possible, but not so steeply that the rate of speed change might lead to large off-speed conditions of the propeller or oscillations in rpm.  The governor time constant was adjustable to obtain to obtain good performance, but its setting was only an estimate for each propeller configuration.  The governor never did cause a problem but such dives to obtain the high speeds were not made often enough with a given propeller configuration to become thoroughly familiar with governing limitations.

On one flight, following the installation of a more elaborate XT-38 fire detection and warning system, which sensed temperature rate as well as temperature, the fire warning light came on during a dive.  The throttle of the XT-38 was pulled back, but to no avail.  Finally, the propeller was feathered in the dive at a Mach number of 0.95 at 30,000 feet….  No major adverse effects were noted (or remembered) in this case.  Also, the fire warning proved to be false and adjustment of the warning system sensitivity took care of the problem. 

The elevator control of the aircraft was adequate to achieve the limit load factor or maximum usable lift coefficient throughout the subsonic operational envelope.  At a Mach greater than 1.0, however, full back stick could develop only 0.75 “g” increment, or a load factor of 1.75 “g” for recovery, an indication of the increased degree of longitudinal stability and the loss of elevator effectiveness caused by Mach number effects.  This was of no consequence operationally in this case, however.

The general handling characteristics were adequate, and the drag rise and trim changes (tuck) in achieving supersonic speeds were mild and posed no difficulties.  Buffet at 1 “g” in transonic flight was non-existent, to the best of my memory.  The highest Mach reached was 1.2 by Fitzpatrick in the acceptance tests at St. Louis.  Many public complaints were received from the resulting sonic boom, however, which caused McDonnell authorities to prohibit further supersonic tests.  Therefore, this kind of operation was minimized at Langley. 

The control forces were manageable with boost off in up-and-away flight.  However, one day after I had just made a high-speed, high-propeller-power pass over some high-ranking visiting observers at Langley the hydraulic control system failed.  Although lateral control could be handled below 200 mph with one hand without major problems away from the ground, I found it a different story on the approach.  I carried more speed (about 180 mph) to avoid the lateral trim changes during landing…and also to avoid a “settling” situation if forced to use two hands on the stick, leaving none for throttle operation.  Actually, two hands were required on the stick continually to keep the the aircraft lined up with the runway (it was a real sweat).  I was beginning to be deeply concerned about flaring while keeping the aircraft aligned when, just about at flare height, the boost came back in, allowing me to land decently.  The nose-down attitude during the approach apparently allowed remaining fluid into the system. 

By late 1957, it was clear that turbojet and newer turbofan engines would represent the wave of the future in both the military and civilian spheres, and the NACA supersonic propeller research program was concluded with its final research flight on 17 January 1958.  Over the course of its research career with NACA, the XF-88B accrued 28 hours of flight time with 43 research flights and three familiarization flights over a period nearly 50 months at Langley.  Jack Reeder had conducted 30 research flights, while Bill Alford had 13 XF-88B flights in his logbook.  NACA pilot Robert Champine had two familiarization flights for a total of 0.6 hours in the aircraft, while J. B. Whitten had one.  While Jack Reeder continued in a long career with NASA, Bill Alford was killed the following year in England during a pitch-up event while landing a prototype Blackburn NA.39 Buccaneer. With the end of the supersonic propeller evaluation, the XF-88B was turned over the base salvage at Langley Field for disposition on 16 September 1958.  The XF-88B was then transferred to Eglin AFB, Florida for ordnance testing.  The XF-88B was tested to destruction at the proving grounds and removed from the USAF inventory in February 1959.  Thus was the end to the distinguished career of the first Voodoo.

Lies and Damned Lies! (Followed by Statistics): Night Fighter Ops in the Korean War

While conducting research for a new book on early USAF interceptor development, I wanted to find out about the combat record of F-94s, the first to be equipped with the new Hughes E-series fire control systems that provided the foundation for at least three generations of successful Air Force interceptors.  I was also curious to compare the F-94 with its contemporaries that were also sent into combat over Korea, most notably the Douglas F3D-2 Skyknight.  What I read from recent, highly reputable sources shocked me and, initially, did not pass the "smell test". The first was this little gem from Air & Space Magazine: "Originally assigned to fly B-29 escort missions every other night, taking turns with U.S. Air Force night fighters, the Marines were soon flying nightly, at the insistence of the Air Force general in charge of B-29 operations, who specified the F3Ds for the job...although the Lockheed jet, like the Skyknight, had a second seater, what it didn't have was the F3D's radar system--or its firepower."  Hmmmm.  I have a very well-worn copy of the official USAF history of the Korean War, The United States Air Force in Korea, 1950-1953 by one of the Air Force's most respected historians, Robert F. Futrell.  I sure didn't see anything like that, and from my knowledge of Hughes fire control systems the foregoing made no sense to me.

So, I started digging deeper and found this screamer in an otherwise outstanding book on fighter design, development, operations, and conceptual evolution: "At first, B-29 escort was an every-other-night assignment, alternating with Air Force F-94s.  The F-94 apparently did not impress, because the general responsible for the bomber group eventually insisted that only F3Ds be used for escort."  Putting it as politely and graciously as I can, the latter claim appeared to be completely unsubstantiated.  I've been around enough sailors growing up to be able to recognize a particular type of "sea story" where the plucky old Navy prevails and comes off smelling like a dainty little rose.  I deeply respect the Navy, and come from an Air Force family.  But I served in the Army and we have a suitably eloquent response to such stories: I call "Bullshit!"  So, using available resources I decided to investigate the question on my own.  Those who served before me deserve nothing less than to make sure that the record is accurate.  Now, maybe I am missing something, but this is what I have, detailed below.

Combat experience against Soviet-flown Mikoyan MiG-15 fighters had shown the utter vulnerability of the Boeing B-29 Superfortress during daylight bombing operations, even with protective screens of escort fighters including the best American fighter aircraft, the North American F-86 Sabre.  After a bloody mission over Sinuiju on 12 April 1951 and the infamous "Black Tuesday" on 23 October of the same year, the rapidly increasing loss rate of B-29s venturing into "MiG Alley" where the industrial heart of communist North Korea was located demanded that the old Superfortress bombers switch over to night missions.  The following months were relatively quiet as the emphasis of B-29 missions changed to tactical support of beleaguered United Nations units fending off over fifty divisions of Red Chinese troops pouring into the Korean peninsula.  As the tide turned over the course of 1952 and the fighting turned into a slow, bloody stalemate along the 38th Parallel, B-29s once again ranged north to cut supply routes connecting Red China and North Korea across the Yalu River and destroy critical enemy infrastructure.  At first, the primary threat against the American bombers was flak directed by radar-controlled searchlights, hearkening back to the night raids over Europe during World War Two.  However, the searchlights were soon used to illuminate the targets for waiting MiG-15s as the long, drawn-out bomber streams were tracked on Communist radar and the MiGs vectored in behind each bomber as they approached their target individually, the B-29s predictably spaced three minutes apart over the same target and following the invisible arcs created by SHORAN navigational beacons.  The effects were rudely demonstrated on 10 June 1952 during a raid over Kwaksan when two of four B-29s conducting the raid were shot down my MiGs after being "coned" by searchlights while a third aircraft was heavily damaged and had to divert for an emergency landing in South Korea.

Experiments using F-84G day fighters under friendly GCI control during August and September of 1952 proved very ineffective, while ECM equipment provided mixed results jamming the ground radars that directed the searchlights.  Meanwhile, Fifth Air Force, in charge of all tactical support aircraft in theater, had since June been considering using night fighters to provide better protection of both B-29 medium bombers and B-26 light bombers during their missions over North Korea.  At the time, there were two squadrons of night fighters based in Korea, VMF(N)-513 of the Marine Corps, equipped with 12 World War Two-era Grumman F7F-3N piston-engine aircraft and the 319th Fighter-Interceptor Squadron, equipped with the newer Lockheed F-94B Starfire, with 25 aircraft on strength, at least on paper.  The latter was an interim interceptor aircraft, designed for night and all-weather air defense of North America, and its limitations were well known as it stood in the gap pending delivery of the long-delayed F-89 and F-86D interceptors.  At its heart was the advanced Hughes E-1 fire control system.  Incorporating a 50-kilowatt AN/APG-33 radar system with an 18-inch diameter antenna, the radar could not only perform both search and automatic tracking functions, but once it was locked on the the target the "black boxes" composing the E-1 system provided steering cues and closure rate to the pilot, indicated when within firing range, and provided a breakaway indication at 200 yards range to permit successful interception without even being able to see the target.  As a backup, the F-94B was also equipped with a conventional gun sight.  Contemporary interceptors could detect the target and follow the "blip" to fall in trail behind it, but had to visually sight the target through the gun sight before engaging it.  The process was not automated as it was in the F-94B.  The Hughes system also allowed other, more advanced intercept geometries such as the "collision course" approach then under development and intended for use with rockets.  This was not possible with existing technology, and the Hughes E-1 system would be a windfall for the Communists to develop advanced all-weather interceptors of their own if it ever fell into enemy hands.

Fearing the compromise of the revolutionary technology of the Hughes E-1 fire control system, since its full introduction to Korea in March 1952 the F-94B had been restricted from areas north of the designated bomb line against North Korean targets.  Instead, the Starfires concentrated on "heckler" attacks by slow, primitive, and effective Polikarpov PO-2 "Mule" biplanes conducting night harassment raids in the rear of UN lines.  In this late summer of 1952, this order still stood in place.  That left only the Marines' twelve F7F-3N Tigercats available to provide night fighter support for the B-29s.  Beginning in June 1952, the "Flying Nightmares" of VMF(N)-513 began providing four planes every night to support Bomber Command missions.  Supporting both B-29 medium bombers and Douglas B-26 light bombers, standard procedure was for the Marine night fighters to arrive five minutes ahead of the bombers and then patrol the 20-25 miles between the initial point (IP) where the bomb run would begin and the target, covering the bombers when they were most vulnerable and unable to take any evasive action.  Although they did contribute to the success of a B-26 mission over the sleepy northeastern coast of North Korea in September 1952, the Grumman Tigercat night fighters proved to be nearly worthless due to limited performance and obsolescent radar technology.  Help was soon on the way for the Marines of VMF(N)-513.

During the early fall of 1952, the "Flying Nightmares" began to transition into the Navy's new jet night fighter, the Douglas F3D-2 Skyknight, known to the Navy as "Willie the Whale" for its large size and lack of engine power.  After limited deployment of four-ship detachments on Navy carriers, the F3D was soon relegated to shore-based duty with Marine aviation units.  The dimensions of the new night fighter were determined by its Westinghouse radar system.  Intended to provide a search range of up to 125 nautical miles against medium bomber-sized targets as well as tail warning of incoming fighters, the Westinghouse AN/APQ-35 radar system was in turn composed of three individual radar systems; the AN/APS-21 search radar with its large 30-inch diameter antenna, the small AN/APG-26 tracking radar positioned in front of the search antenna used to generate target range and firing solutions for the night fighter, as well as a seperate AN/APS-28 tail warning radar with a maximum range of three miles to warn of enemy fighters closing on the tail for a firing pass.  With a peak power output of 200 kilowatts and the large search antenna offering excellent angular resolution, the APQ-35 radar system of the F3D-2 could detect a fighter-sized target out to a range of about 17 nautical miles, far short of the original specification but excellent performance for the day.  Tracking range of the 8-inch diameter, 50-kilowatt APG-26 was limited to a maximum range of 4,000 yards, but could not provide a firing solution until within 2,000 yards or 1 nautical mile.  Given two crew members and two separate radar systems, the F3D had a rudimentary track-while-scan system that often proved useful in the hands of an experienced crew.  However, these capabilities came at the cost of a huge weight penalty and greatly increased aerodynamic drag due to the large frontal area needed to accommodate the radar equipment.  Underpowered due to the failure of the more powerful Westinghouse J46 engine, the F3D-2 had to make do with a pair of Westinghouse J34-WE-36 turbojets, laboring to produce 6,800 pounds of thrust against a combat weight of 21,374 pounds and a maximum load factor of 5.5 G.  The maximum rate of climb at combat weight for the F3D-2 was an anemic 3,570 feet-per-minute at sea level to a combat ceiling of 35,500 feet.  The F3D-2 had a maximum speed of 458 knots at sea level.  In its favor, the F3D-2 had the potent standard Navy armament of four 20-millimeter cannon, married to a MK 20 Mod 0 gun sight and a combat radius of 520 nautical miles.

In comparison, the Lockheed F-94 was built as an interceptor rather than a night fighter.  For the interception mission, speed, rate-of-climb, and combat ceiling are paramount.  Conceived as an interim interceptor design to provide the USAF a night and all-weather intercept capability at the earliest date, Lockheed essentially married the new Hughes E-1 fire control system for the Northrop F-89 Scorpion to the best performing two-seat aircraft in the USAF inventory, the TF-80C (later better known as the T-33).  Adding an afterburner to the basic Allison J33 engine for better climb and altitude performance along with other minor improvements yielded the original F-94A.  While the E-1 system possessed advanced capabilities, the relatively small 18-inch diameter antenna and 50-kilowatt power output imposed performance restrictions on the AN/APG-33 radar.  During tests, the APG-33 radar demonstrated a maximum search range of 10 nautical miles against a B-25 target, however, the scope display went out to 30,000 yards or 15 nautical miles.  Tracking range was about the same as for the F3D, with the range display graduated on the attack display out to 2,000 yards.  Despite the awkward radome spoiling the fine lines of its F-80 predecessor, it faired cleanly into the nose structure to produce a minimal drag penalty for the F-94.  The F-94B that was deployed to Korea benefited from all-weather landing systems, improved avionics and a somewhat more reliable J33-A-33A afterburning engine that produced a maximum of 6,000 pounds thrust against a combat weight of 13,474 pounds, an extremely modest thrust loading by today's standards but respectable for the early 1950s and far better than the numbers for the F3D-2.  For an area intercept mission, the F-94B had a combat ceiling of 45,700 feet, a maximum rate of climb of 7,800 feet per minute, and a maximum speed 511 knots at sea level using afterburner.  Given the small airframe and thirsty engine, the F-94B had a relatively limited combat radius of 288 nautical miles.

In late 1952, the Soviet Union was preparing to introduce its first jet night fighter after six-and-a-half years of design effort and four years of flight test development.  Experiencing many false starts and severe developmental hurdles, Soviet planners had settled on the one system that worked, married to the one proven fighter available with the RP-1 Izumrud ("Emerald") radar system, tested on a modified MiG-15 and accepted for service with the brand-new MiG-17 as the MiG-17P "Fresco-B" interceptor.  An evolutionary development of the MiG-15, the early MiG-17 possessed somewhat higher speed but still made do with the non-afterburning VK-1 engine of the late-model MiG-15bis.  Most of the Soviet effort had been focused on a radar system similar in concept to the early Hughes E-series systems, the Toriy  ("Thorium") radar.  Intended for both single and dual-place interceptors, the Toriy used a single antenna to conduct both search and tracking functions, and as with the Hughes radars was to have an auto-track function once the radar was locked on its target.  The Toriy failed to pass its State trials during early 1952 and a subsequent design, the Korshun ("Kite") was also a failure.  This left the RP-1 Izumrud, developed as a back-up system, as the primary airborne intercept radar for first-generation Soviet night fighters.  Like the AN/APQ-35 system of the Douglas Skyknight, search and tracking functions were divided between two separate antennas, although in the case of the RP-1 system they were much smaller, scaled to fit a small MiG-15 sized fighter.  The tracking antenna was contained in a small bullet fairing centered within the engine inlet while the larger rectangular antenna of the search radar was faired into the nose fuselage above the inlet duct.  Against a B-29 sized target, the RP-1 Izumrud, given the NATO code name "Scan Fix," had a search range of about 6 nautical miles and a tracking range of 1 nautical mile.  Many more experimental radar systems would follow over the course of the 1950s, but until the appearance of the TsD-30 "High Fix" radar in 1959 with the Sukhoi Su-9 "Fishpot" interceptor, the primitive dual-antenna Izumrud would remain the standard radar system for high-performance Soviet interceptors (even then, "High Fix" had very limited capabilities compared to contemporary Western fighter radars).  This background is relevant as it provides context for the decision to allow the Marine F3D night fighters to operate over North Korea while the restriction on the E-1 equipped F-94B remained in place.  In retrospect, exploitation of a captured Hughes E-1 system could have drastically changed the Soviet's developmental trajectory for interceptor radars during the critical decade of the 1950s.  The older technology represented by the Westinghouse AN/APQ-35 system would have done relatively little to aid Soviet efforts, so the F3D-2 interceptors carrying them were allowed to range over North Korea right up to the Yalu River.

Having completed the transition to the F3D-2 by the beginning of November 1952, the Marine aviators of VMF(N)-513 soon enjoyed great success with their new mounts, due in no small part to their naturally aggressive spirit.  On 2 November 1952, a Marine Skyknight claimed its first victory during an escort mission over Sinuiju when GCI from Chodo Island positioned an F3D behind a Communist jet.  The Marines closed in and, based on the exhaust pattern, identified the Red fighter as a Yak-15, peering through the gun sight and opening fire.  As it turned out, Russian records have shown that the aircraft was a MiG-15, not a Yakovlev fighter, which was never deployed to Korea.  The same records also show that the tough MiG survived the attack and managed to return to base.  A second MiG-15 was not so lucky during the evening of 8 November when another Skyknight crew downed a MiG-15 northwest of Sonchon.  At that time, standard procedure for was to provide barrier cover to the drawn-out B-29 bomber streams by taking a position 20 to 50 miles north of the target under GCI control.  As the month of November drew on, Brigadier General Fisher, commanding general of FEAF Bomber Command, noted that the Marine Skyknights provided "some small degree of success."  Meanwhile, frustrated USAF Starfire crews busied themselves with the dangerously mundane task of using the most technologically advanced aircraft in theater to pursue low, slow biplane intruders made with fabric and wire.

The situation changed in November 1952 when the Chief of Staff of the Air Force, General Vandenberg, was conducting a personal tour of units in the Korea theater.  Upon hearing about continuing harassment of Bomber Command aircraft by MiGs and the gross misuse of the F-94s of the 319th FIS, General Vandenburg immediately ordered that the Starfires be allowed to conduct missions north of the bomb line between the Yalu River and Chongehon River.  Areas directly along the Yalu River were still deemed too sensitive for the F-94B, but the F-94s began to take the fight up north, used to support missions by Douglas B-26 Invader light bombers while the Marine F3D-2 night fighters continued with the B-29 support mission.  This arrangement would continue for the next two months through late January 1953.  During that interval, four Bomber Command B-29s would be shot down by MiG-15s and many more badly damaged, along with one more special missions B-29 conducting a night leaflet drop while attached to the 91st Strategic Reconnaissance Squadron, which would not have merited an escort of scarce night fighters.  While the Marines earned their hard-won recognition and eventual fame for four MiG kills through the end of January 1953, the historical record shows that it should be tempered by the loss of four B-29 Superfortresses during their watch.  Over the preceding months, the F3D barrier patrols allowed enough MiGs to leak through to conduct 23 firing passes against B-29 formations with their heavy cannon armament, according to Bomber Command's statistics.  By late January, Brig. Gen. Fisher seriously considered withdrawing the B-29 from combat operations over North Korea due to increasing losses, but more advanced B-50, B-47 and B-36 bombers were simply not available, being fully committed to the expanding Strategic Air Command deterrent force.  Improved tactics and timing for the SHORAN-guided B-29 streams could improve the situation, but the fighter support piece had to be addressed, urgently.

A 27 January 1953 meeting at Fifth Air Force headquarters yielded a new plan for improved utilization and coordination of night fighters and resulting joint procedures to better support Bomber Command objectives.  Taking inventory of available mission assets, the GCI station at Chodo Island was limited to controlling four interceptors at a time.  Available night fighter forces were 12 F3D-2 Skyknights of VMF(N)-513 and (at least on paper) 25 F-94B Starfires of the 319th FIS.  Both aircraft, perhaps more notably the F-94, suffered from severe maintenance headaches.  On any given night, the 319th could only manage an 80-percent in-commission rate with an average of five aircraft down for maintenance.  This situation was further exacerbated by a critical USAF shortage of what was still the primary all-weather interceptor defending North American territory as the F-89 and F-86D programs continued to drag on and the newly introduced F-94C Starfire was experiencing the usual teething problems.  While the Marine Air Wing commander requested twelve more "highly effective" F3D-2 night fighters from CINC Pacific Fleet, his request was politely rejected on grounds that the bomber support mission was primarily a USAF responsibility as well as questionable resources to maintain a second squadron of temperamental jet night fighters in theater.  The respective night fighters of each service were assigned different roles.  One great advantage of the F3D-2 was that its Westinghouse AN/APQ-35 radar could detect the identification (IFF) signals of friendly B-29 bombers, making it easy for them to keep close tabs on their charges so the Marines were assigned the close escort mission.

The Marine F3Ds had already adjusted tactics by that point in January 1953 in response to a Bomber Command request for better overhead cover of its bomber streams.  Under the new tactical concept, the F3Ds would position themselves 2,000 to 3,000 feet overhead of the bombers at the initial point (IP) where the B-29s would begin their bomb run and follow the bomber stream through the target and to their breakaway point.  If a bomber was "coned" by searchlights, the F3Ds would fall into position to cover its tail and engage MiGs as they moved into firing position.  Within the next few days left in January 1953, this would lead to two more MiG-15 kills by Marine Skyknight crews to bring their cumulative total to four.  Meanwhile, the Air Force F-94Bs would be assigned to provide barrier counter-air patrols between the MiG bases and bombers, positioned about 30 miles from the target.  Kills by Air Force F-94 crews would also be forthcoming.  During subsequent night fighter support missions, four to six F-94s would be assigned to the barrier patrol mission on any given night under GCI direction from Chodo Island while nine F3Ds (including two spares) would provide close escort for the Superfortresses, most using either "racetrack" or "pacer" tactics alongside the bomber stream while one or two more Skyknights would provide overhead patrols over the target.  Both sets of night fighters were required to check in with the Tactical Air Direction Center (TADC) 20 minutes prior to the bombers' time over target to be vectored towards any detected airborne threats.

Once these and Brigadier General Fisher's tactical changes to reduce the vulnerability of the B-29s were implemented, mission success improved and the B-29 loss of 28 January 1953 would prove to be the final combat loss of a Superfortress over Korea.  A switch back to occasional nighttime tactical support missions as UN forces fought to gain ground while armistice negotiations were under way was also a contributing factor to the decreased loss rate.  As the winter of early 1953 wore on, the commander of the 319th FIS voiced his frustration that the MiGs would not come up to engage his barrier patrols, but their presence coupled with the close protection of Marine F3D crews served as an effective deterrent to Communist MiGs and improved the flagging morale of the B-29 crews.  In early May 1953, B-29 targets began to shift once again towards lines of communication across the Yalu River and logistical targets on the Korean side of the Chinese border as Red forces tried to rush in supplies and equipment in advance of the impending armistice.  Due to the risk of an aircraft being captured by Chinese forces and quickly spirited away before the wreckage could be located and destroyed, target areas immediately adjacent to the Yalu River remained off-limits to the F-94.  Therefore, in the latter weeks of the Korean War VMF(N)-513 would assume barrier patrol duties in addition to close escort of the B-29s as they struck an increasing number of targets along the Yalu.  In the meantime, both units continued to fend off North Korean "Bedcheck Charlie" harassment missions.  The PO-2 biplanes often proved difficult to find within the "ground clutter" experienced by fighter radars at low altitude.  During the spring of 1953 the 319th FIS scored three more kills, including two MiG-15s.  Unfortunately, two F-94Bs were lost during the same period, one due to stalling out at low altitude after shooting down a PO-2 and the second after colliding with another of the low, slow intruders.  A total of 28 F-94B aircraft were lost in the Korean theater, mostly due to operational causes.  Two were lost during combat operations and none to enemy action.  The F-94B crews of the 319th FIS can also remain justifiably proud that no B-29s were lost while they were on duty.

The Marines of the VMF(N)-513 "Flying Nightmares" have earned a place in history as the first unit to make a night kill of a MiG-15 and to have achieved more MiG kills than any other night fighter.  With regard to the Air Force F-94s, the limitations of the aircraft had been acknowledged from the start, yet the record shows that it performed admirably.  In the final analysis, it is difficult to prove the effectiveness of night fighter operations because of what didn't happen, since Western historians have not had the benefit of knowing specific details of enemy planning, intentions, and operations against B-29 incursions.  Nonetheless, the facts do exist for what did happen, and when.  There was no need for Air Force historians such as Robert Futrell or anyone else to burnish the image of the Starfire into a gross historical distortion and grasp after unearned glory.  It would seem to me that some modern historians have done this, perhaps unintentionally, on behalf of their own service interests of Navy and Marine aircraft and units, and have done so at the expense of brave Air Force crews performing a miserable and thankless job during a now forgotten war.  Some of their number are still with us, and they deserve better.  This has been my attempt to give them their due by fleshing out the history and examining it all within a broader context.  The conclusions that I have drawn as a result are quite different and, I would say, better corroborated by available historical evidence.

Selected references:

Futrell, Robert F., The United States Air Force in Korea: 1950-1953, New York: Duell, Sloan and Pearce, 1961.

Futrell, Robert F., United States Air Force Operations in the Korean Conflict, 1 July 1952-27 July 1953, USAF Historical Study No. 127, USAF Historical Division, Research Studies Institute, Air University, 1 July 1956.

Dorr, Robert F., B-29 Superfortress Units of the Korean War, Osprey Combat Aircraft 42, Botley, Oxford: Osprey Publishing, 2003.

Standard Aircraft Characteristics, F-94B, 24 March 1952.

Standard Aircraft Characteristics, F3D-2 "Skyknight," 15 February 1952.

Radar Set, AN/APQ-35, -35A, MIL-HDBK-162A, 15 December 1965.

Buttler, Tony and Gordon, Yefim, Soviet Secret Projects: Fighters Since 1945, Hinckley, England: Midland Publishing, 2005.