by Tommy H. Thomason

Sunday, November 29, 2009

F6F Drones

At the end of World War II, the Navy had more carrier-based propeller-driven fighters than it knew what to do with. The F6F Hellcats were apparently judged to be less useful for air group operations than the F4U Corsairs, so they were assigned to training squadrons and drone operations, among other things.

The F6F drones were initially developed at the Naval Air Development Unit at Johnsville, Pennsylvania. At least one of these was painted a yellow-orange overall and another may have been an odd shade of blue. The extended tail wheel was a feature of these aircraft, which were recoverable.

There appear to have been at least three major uses for the F6F drones. The first was a fleet of aircraft that sampled airborne radioactivity after atomic bomb explosions during Operations Crossroads in 1946. These were painted bright red with different color empennages, apparently to denote radio frequency. The national insignia lacked the red bar.

The second use was as targets. In 1947, VU-7(a) was based at NAS Santa Ana for the continuation of pilotless aircraft evaluation. The squadron was assigned Culver TD2C / Grumman F6F Hellcats as target aircraft for surface-to-air gunnery training with Beech SNB Expeditors as the drone controllers. OLF Palisades was used to launch and recover the drones. (On-board pilots ferried them to and from Santa Ana.) The squadron was relocated at MCAS El Toro in 1948. Target drone operations were subsequently established at China Lake and Point Mugu for missile-test purposes and at other locations, again using utility squadrons, as targets for training. Some aircraft were modified with “tip tanks” and large wing tip fairings containing flares to simulate a jet exhaust, and therefore be of appropriate interest to the heat-seeking Sidewinder missile being developed… In December 1952, an XAAM-2 Sparrow missile was used to intercept and destroy an F6F flying from Point Mugu, supposedly the first successful air-to-air guided missile kill.* In September 1953, the Sidewinder made its first successful interception, again destroying an F6F, this time being operated from China Lake. In general, these aircraft were painted either bright red or florescent red overall.

The third use was as a crude surface-to-surface guided missile. There were six missions launched from Boxer between 28 August and 2 September 1952 during the Korean War against bridges, tunnels and power plants. Guided Missile Unit 90 had been formed at Naval Air Development Unit at Johnsville, Pennsylvania. AD-2Qs were used as controllers. The F6Fs carried a TV camera in a pod under the right wing for targeting. An antenna for transmission of the TV image to the controller in the AD-2Q was mounted on the upper surface of the right wing above the pod. The attack drone F6Fs were overall glossy sea blue with standard national insignia and branch of service markings. They were differentiated with V1 through V6 markings on the cowling. Note that these aircraft did not have the extended tail wheel (they weren’t coming back) or tail fins on the bomb (it wasn’t going to be dropped). Of the six missions, there was one hit, one abort (then what?) and four misses.

*An F6F drone was reportedly used to launch the first Sparrow from an aircraft because there had been a couple of fatal accidents at China Lake as a result of rocket launches. This picture, furnished by Phillip Fridell, shows an F6F drone (note the extended tail wheel) carrying a Sparrow, although it was being piloted at the time.

For more pictures of this F6F drone, see the entry in Phil's excellent blog here.

Friday, November 20, 2009

F3H-G/H

This is another work in progress. There are various drawings of the F3H-G/H that preceded the AH and subsequently the F4H. This is one rough draft I've done from an early F3H-G McDonnell drawing (the 10 cm scales it to 1/72nd) with J79 exhausts that were included on the drawing side view as an option; I had to correct the front view rather extensively:


This a later McDonnell three-view. It's similar but the landing gear has been shortened and there are other detail changes like the shape of the vertical fin and rudder. It doesn't show different engine exhausts, but I assume that the draftsman just didn't bother:





The F3H-G/H mock up was also a bit different in detail and doesn't seem to have had a landing gear at the time. The inlets appear to be larger and there is yet another variation of the vertical fin. It did depict the different sizes of the Wright J65 and General Electric J79 afterburners, with the J79 on the right side of the mockup and the J65 on the left.




Sunday, November 8, 2009

Early Phantom IIs

12 September 2011: Added stabilator changes
26 May 2011: Revised Configuration Matrix
23 November 2010: Added cockpit illustrations
10 November 2010: Added information on configuration differences between early and late F4H-1s
12 November 2009: Updated Configuration Matrix

Also see: http://tailspintopics.blogspot.com/2011/05/early-phantom-iis-redux.html

The F4H (F-4) Phantom II was originally intended to be a single-seat, supersonic attack airplane, the AH, powered by two afterburning Wright J65s. Because of an urgent need for a supersonic, two-seat, Sparrow-missile-armed fleet air defense capability, the fighter class desk at the Bureau of Aeronautics hijacked the program and repurposed it, substituting more powerful General Electric J79s for the Wrights. The second seat was crammed into the avionics bay of the AH.

During the course of development, a larger radar dish was deemed necessary to increase the detection range of incoming bombers, which resulted in a larger nose and raising the cockpit slightly. The engine inlets were also refined, in part due to higher than expected speeds being achieved with early uprating of the J79. As a result of these and other changes, there were detailed configuration differences among the first few dozen Phantoms. The first 47 were redesignated F4H-1F in May 1961, primarily to differentiate between airplanes with the J79-GE-2s and those with the -8s. In the 1962 DoD-directed redesignation exercise, the F4H-1Fs became F-4As and the F4H-1s, F-4Bs. (Click on this and any other image for a larger picture.)



The first F4H (not yet named Phantom II) first flight.
 
The larger radar dish required a larger radome, which resulted in raising the canopy line to restore visibility past the nose for the pilot's view of the carrier approach aids. As much of the original structure was retained as possible, reportedly up to the canopy sills.
As noted in the configuration matrix, not all F4Hs with big noses got the raised canopy. This is BuNo 145313.
The inlet change went through several iterations. The first XF4H, BuNo 142259, had a hooded inlet with a narrow fixed ramp and the external portion of the variable ramp was non-porous.

The next step appears to have been making the variable ramp porous. In some cases, the early porous variable ramp did not have the discharge chute at the bottom; in others, the chute was present at both the top and bottom of the ramp as on Skyburner and the second Sageburner.

The first F4H in early 1959 with a porous variable ramp and only the lower discharge chute; the "hood" on the top of inlet has been removed. Note that there is now a McDonnell ejection seat in the rear cockpit.

143389 (#4) on 4 December 1959 with the original hooded intake and no discharge chutes (note the addition of the infrared detector under the small nose and the different air inlet aft of that compared to NACA inlet in the picture above):

The second Sageburner. Note that this inlet has also been modified to remove the hood and the chutes are clearly scabbed on:

On the production inlet, there was both a lower and an upper discharge chute, but the latter was smaller. The fixed ramp was a much larger portion of the ramp area. The ramp angles were also changed during inlet development. The fixed ramp was originally set at an angle of 5 degrees and subsequently increased to 10 degrees. The variable ramp angle range was also increased.

The early Phantoms used a McDonnell-furnished seat:
Another major change, introduced with F4H #6, was the addition of Boundary Layer Control and inboard leading edge flaps in order to reduce the approach speed. My guess is that the cambered leading edge was also added to the stabilator as part of this redesign. The original stabilator had a symmetrical leading edge:

The cambered leading edge curved up to increase the down force from the stabilator at the same angle.

Interim stabilators had a zig-zag pattern at about 20% chord where the new leading edge was incorporated. Note that production stabilators integrated the camber as part of the basic structure so there is no zig-zag.

This redesign to increase lift and reduce approach speed delayed the carrier qualification trials.

Initially, the F4H had two emergency turbines, one in each wing under the inboard leading edge. When it was decided that the airplane needed inboard leading edge flaps, these were replaced by a single RAT in the upper left side of the fuselage. (For more on this installation, see http://tailhooktopics.blogspot.com/2012/12/early-f4h-rat.html)

The early F4Hs had perforated spoilers like the F3H as shown here on BuNO 143390. The holes were subsequently deleted, likely on the next airplane—which incorporated the inboard leading edge flaps—and probably to improve roll control effectiveness at approach speeds.
 This is the 6th F4H used for the initial at-sea evaluation on a subsequent visit to a carrier in different markings.


Thanks to Larry McCarley, I now have more illustrations of the cockpits of the early Phantoms.

The Airborne Missile Control System display was very different in the early F4Hs. Note that it wouldn't have been installed in the first aircraft.
The early aircraft probably had the area reserved for the pilot's radar indicator and missile controls filled with flight test unique instruments.

Contrary to speculation, some aircraft with the low canopy line did have a McDonnell ejection seat installed in the aft cockpit as shown in the picture of the first F4H above. However, the ejection seat was probably not installed in the aft cockpit of at least some of the early aircraft that didn't have the missile control system installed. It was likely filled instead with research instrumentation equipment. This is the rear seat equivalent of the pilot's early missile control system:
Note that the instrument panel in the aft cockpit was slightly different depending on the bureau number with the major change being the addition of an artificial horizon and airspeed indicator:

Sunday, November 1, 2009

Nuclear Banshees

As soon as the atomic bomb got small enough to be carried by tactical jet fighters, the Navy adopted the McDonnell F2H Banshee for it, first the F2H-2 as the -2B and then the -3/4.

The F2H-2B was externally similar to the F2H-2, but had some local strengthening of the wings so that the aircraft could carry a 1650-lb Mk 7 or a 3230 lb Mk 8 nuclear bomb on a big pylon underneath the port stub wing. The flaps on that side had a small cutout for clearance of the store. An in-flight refueling probe installation was subsequently developed that could be installed in place of the upper right 20mm cannon.

The -7 was a very large weapon which required increasing the pressure in the main landing gear strut to provide even minimal ground clearance. This is my guess at the pylon shape and bomb location; note that the shock strut has not yet been extended to provide a modicum of ground clearance. (Read on for a description of this system on the F2H-3/4, which may also have applied to the F2H-2B.)  I've subsequently discovered (see below) that the tail cone had to be rotated clockwise (viewed from the rear) to provide clearance with the J34.


The F2H-2Bs were deployed only a few times, the first as a VC-4 detachment aboard Coral Sea to the Mediterranean beginning in April 1952. Other known detachments are VC-4 Det 7 aboard Franklin D. Roosevelt (CVB-42) and Det 44 aboard Lake Champlain (CVA-39) in 1953. Det 5 aboard Midway from December 1952 to May 1953 may have operated F2H-2Bs as well. There are also pictures of VF-82 F2H-2Bs aboard Champlain on its September 1954/April 1955 deployment and with VF-101 aboard Midway in 1955, shown here.

This is a picture of VC-4 F2H-2Bs aboard Lake Champlain sometime between June and November 1953. Note the flat-bottomed inboard stores pylon which was probably used for the Mk 8.


The F2H-2B was reportedly manufactured alongside the "stock" F2H-2 and -2Ps on the McDonnell production line. 27 were listed in an appendix to the F2H maintenance manual (Also see comment below).


125030/125031
125054
125056
125058/125059
125061/125062
125064
125066/125067
125069/125070
125500
125502
125504/125505
125650/125651
125653/125654
125656/125657
125659/125662

For some reason, the location of both the refueling probe and the bomb mount were switched  on the F2H-3/4, with the bomb now being carried on the right side and the refueling probe installed on the left side of the nose.
 

Whereas the F2H-2B had the cutout only in the left side flaps, the F2H-3/4 had the cutout in both flaps.
 Mk 7 clearance was still a problem, however.

Thanks to the Gerald Balzer collection via Mark Nankivil, I now have better pictures of the Mk 7 and Mk 8 being carried by the F2H-3/4.
Note that all the shock struts are fully extended to provide a modicum of ground clearance. This also shows how the tail cone on the Mk 7 was rotated counterclockwise (looking forward), in order to clear the jet tailpipe.

Thanks to Larry Webster of the Quonset Air Museum, who provided a copy of the F2H-3/4 maintenance manual section on the main landing gear special strut extension, I can now accurately describe this feature. It was accomplished by adding two separate hydraulic fluid tanks. The fluid in both tanks was added to both shock struts to extend them fully for taxi and takeoff. (The nose gear strut extension was a separate system that was used on all F2H-3/4 catapult takeoffs.)

The struts were only partially deflated automatically when the landing gear was retracted "to permit a landing with stores still aboard" (presumably not on a carrier), which was why there were two separate tanks. To remove the remainder of the extra fluid from the struts for normal strut action, the pilot had to actuate a switch on the left console after he had lowered the landing gear.

This strut extension capability was provided by a kit, suggesting that it was only added to aircraft designated for the mission. I have read that the F2H-2B strut extension was provided with "sleeves" added over the exposed piston. These reportedly dropped away after lift off. However, I don't have any documentation on that yet so I can't say that's myth or fact. It may have been an early kludge to provide the capability before the strut extension kit was developed. I also don't know whether just the bomb-side strut was extended on the F2H-2B or both sides. My guess would be both.


The Mk 8 picture was even more welcome. It was mounted on a slightly different pylon and also required the shock strut extension to provide clearance for the tail fin group. Note that this aircraft is equipped with the inflight refueling probe replacing one of the 20mm cannons and the fairing on the belly associated with this modification.

The shape shown below is the BOAR, a Mk 7 with a rocket attached for better separation from the instant sunshine it created.) Note again that the main landing gear shock strut is fully extended to provide what clearance there is but the nose strut has not yet been extended.