V-366 Landing Gear Studies

 Additional design study work was requested by the BuAer for the F7U development program. The V-366A/B/C had listed "undesirable catapult take-off characteristics, unprotected fuel tanks, insufficient vision over the nose and insufficient strength to meet current Bureau strength requirements." The V-366, (improved F7U-1) with Westinghouse 24C jet engines (J46) and improved radar, armament combination.

The BuAer requested the contractor to study landing gear arrangements other than the conventional tricycle gear for application in the design. It was an attempt at solutions to the "problems associated with operating a swept wing airplane off an aircraft carrier."

The conventional tail wheel was "not satisfactory due to high bearing loads in the strut and the adverse effect on airplane balance."

Tricycle gear with addition of a small tail wheel was evaluated next. This arrangement allowed the airplane to rock back on the tail wheel as the bridle and holdback are tensioned. The catapult bridle was planned to maintain the airplane on the main and tail wheel after the catapult was fired. This study with others led to a better solution of an extensible nose wheel strut removing dependency on the catapult bridle maintaining take-off attitude.

The third arrangement was a bicycle arrangement which was more difficult to implement due to fuselage space arrangements and weight. The fuselage would need reinforcement for the landing gear loads, the out riggers had to be heavy due to barrier crash loads.

In the end it was concluded that none of the configurations considered offered improvement over the conventional tricycle landing gear of the V-366 proposal

The Mysterious Loss of XF7U-1 122473

Previously, the short life of XF7U-1 122472 was presented in this blog along with a photo feature. This post covers the second XF7U-1 BuNo 122473 with the few details available from it's accident summary.

Here is a shot of 122473 prior to it's first flight (VAHF Collection)

122473 first flew on February 15, 1949. It's brief life also included a wheels up landing just three days later on February 18, 1949. The wheels up landing resulted in repairs that grounded the aircraft until March 5, 1949 when it returned to flight status.

Several photos showing damage after the wheels up landing on February 18th. (USN Photos)

The aircraft started field carrier landing tests for flights 6 through 13. The short career of 122473 ended when it crashed on it's thirteenth flight.

Here are the details of 122473's final flight. 

W. Millar, a CVA test pilot, took off from NAS Patuxent River, Maryland on March 14, 1949. The flight was to be a routine shakedown and the US Navy was going to take some aerial photographs of the jet. The photographic mission was accomplished and Millar broke off from the formation presumably entering the pattern to land. 

The summary states: "Aircraft was never heard from again. Pilot never reported any difficulties." A widespread search of Chesapeake Bay was initiated and eventually pieces of the missing aircraft were located. The summary continues " From pieces of wreckage it was presumed that aircraft entered water gear down and slats out in a left roll."

The cause for the accident was never determined.

V-389 More Details

     Continuing with V-389 information is a look at the actual J57-P-4 engine installation into the A2U-1 airframe. This installation drawing shows the placement of the engine and afterburner assembly into the A2U fuselage. 

     Basically aft of fuselage station 265.1 a structural production break the fuselage is new. One major internal change is the changing from a central shear panel (formerly between the two engines) to two shear panels (one on either side of the engine) to absorb fuselage bending loads and fuel inertial loads. 

     All the changes to the fuselage still enable the same wing root rib to be used with the slight exception at the tail cone.

Clip from CVS-37356 V-389 Engine Installation Profile View

Clip from CVS-37356 V-389 Engine Installation Plan View

     Changes to the wing center section was fairly mild. The center-section pylons are moved 9.7 inches aft of the A2U location. The pylons attached to the main wing beam and aft beam instead of the front beam and main beam. 

CVS-37358 V-389 Comparison of V-389 and A2U-1 Plan View

     In addition to the pylons the aft end of the wing root was to be changed to adapt to the new aft fuselage cone for the single exhaust.

CVS-37358 V-389 Comparison of V-389 and A2U-1 Plan View

     Under the skin lighter electrical and hydraulic systems were incorporated. The electrical system would incorporate a separate AC and DC circuits with AC generation taking place by a bleed air turbine generator. Weight would be saved by removing one DC generator, internal battery, and two inverters.

     The hydraulic system incorporated an emergency ram-air-turbine driven hydraulic pump and alternator. The utility system reservoir was redesigned to accommodate the lower fluid volume requirements. One utility system pump was eliminated due to a new higher efficiency pump and the hydraulic oil cooler was eliminated.

     Another subtle change was the installation of only two MK12 guns above the right-hand inlet duct with provisions for a second set over the left-hand inlet duct. 

CVS-37360 V-389 Gun Installation Profile View

The gun muzzles are staggered and located aft of the duct lip instead of in the air duct lip like the A2U-1.

CVS-37360 V-389 Gun Installation Plan View

Source Chance Vought Engineering Report 8847 V-389 Attack Airplane Design Report, NARA II

V-389 Attack Aircraft

  

     A January 1954 Chance Vought V-389 proposal was for an improved performance attack aircraft based upon the A2U-1 Cutlass. The proposal featured a single Pratt and Whitney J57-P-4 engine replacing the twin Westinghouse J46 engines. A new fuselage section from the inlets aft would be required to house the single engine. The V-389 would share major components of the A2U-1 including wings, vertical tails, landing gear and forward fuselage.

The powerplant change caused a significant increase in radius of action, 280 nautical miles for a total radius of 605 NM while using only internal fuel and carrying two 2,000 lb bombs. 

The V-389 equipped with external fuel and a “special weapon*” had a radius of 815 NM.

AIRPLANE	V-389		A2U-1
ENGINE	J57-P-4		TWO J46-WE-18
Loading	Two 2,000 lb Bombs	3,500 lb Store, 300 Gallon Drop Tank and 220 Gallon Fuel Pack	Two 2,000 lb Bombs	3,500 lb Store, 300 Gallon Drop Tank and 220 Gallon Fuel Pack
Gross Weight	34,830 lbs.	38,170 lbs.	33,950 lbs.	37,330 lbs.
Combat Radius (NM)	605	815	325	500
Max Speed, Sea Level Clean Configuration (kts)	598	598	593	593

There appeared to be little official interest in the proposal and eventually the entire A2U-1 program was canceled. The V-389 is left as another interesting “what if”.

Data from Vought Report 8846 NARA II 

*The F7U-3 was cleared in separation tests to carry the Mk 7, 8, 11, and 12 stores.

The A2U-1 cancellation occurred November 19, 1954

Other A2U related posts: (here) (and here)

F7U-3 129558

     Here is a set of factory images of F7U-3 129558 as she looked factory fresh in October 28, 1953.

     129558 was the 42nd F7U-3 built. The initial delivery date was April 28, 1954. The aircraft returned to CVA for modification on November 20, 1954. The aircraft was then delivered to VA-12 on December 13, 1955. 129558 was Stricken at Cecil Field, FL October 5, 1956 after a fire on the ground.  NARA II RG72AC photos

CVA-18346-F7U-3-129558-Left-Side-View-19531028

CVA-18348-F7U-3-129558-Front-View-Rocket-Pack-and-Pylons-19531028

CVA-18349-F7U-3-129558-Left-Front-View-19531028

CVA-18350-F7U-3-129558-Right-Front-View-19531028

CVA-18351-F7U-3-129558-Right-Rear-View-19531028

CVA-18352-F7U-3-129558-Left-Side-View-Wings-Folded-19531028

CVA-18353-F7U-3-129558-Front-View-Wings-Folded-19531028

CVA-18354-F7U-3-129558-Right-Side-View-19531028

CVA-18355-F7U-3-129558-Front-View-19531028

CVA-18357-F7U-3-129558-Rear-View-19531028

F7U-3P Part Three

     Final installment on the F7U-3P Mock Up. These final three images illustrated the access door on the upper fuselage to allow camera installation and film magazine servicing. Along with hold open rods for the door, the hoist for raising and lowering the cameras is installed. It still would have been quite a challenge changing cameras and install in film magazines 12-14 feet off the deck!

CVA-10619-F7U-3P-Door-Stay-Instal-Camera-Access-Door-and-Hoist-19520627

     This next photo shows the Tri-metric mount along with CA-8 and T-6 cameras.

CVA-10445-F7U-3P-TRI-Met-and-Camera-Mount-Showing-All-Configs-19520618

   

     Next up is the mock up of the main instrument board. The main visual difference is the addition of the view finder in place of the gun sight. The viewfinder worked for missions where the aircraft was configured for downward looking cameras for coverage of targets that the photo Cutlass flew over.

CV-10907-F7U-3P-Mock-Up-Main-Instrument-Board-19520729

  The final image shows the oblique sights for camera installations shooting out the sides of the photo Cutlass. A sight was provided on the left and right canopy sills for use depending on the camera configuration mounted in the aircraft.

CVA-10610-F7U-3P-Oblique-Sight-Installation-19520625

     The photos and information for this installment came from Chance Vought Report 7802 Model F7U-3P Mock-Up Photographs dated August 5, 1962. The report was found in NARA 72-AC-30G.

F7U-3P Part Two

     For those of you who are interested in the details of the reconnaissance portion of the proposal there were a number of images surrounding the camera installations in the F7U-3P.

CVA-10317 F7U-3P General Reconnaissance Configuration 19520613

     The general reconnaissance configuration has a P-2 strike camera in the nose with a K17 camera in Station One along with a K17 or a K38 camera in Station Two with a fixed or rotatable mounts. 

CVA-10318 F7U-3P Mapping and Charting Configuration 19520613

     The charting and mapping configuration removes the P-2 camera from the nose and installs a K17 or CA-8 or T-11 camera in Station One. Station Two is configured with a K17, CA-8 or T-11 Tri-Metrogon assembly.

CVA-10319 F7U-3P Beach and Offshore Reconnaissance Configuration 19520613

     The Beach and Offshore reconnaissance configuration removes the P-2 camera in the nose and adds the CAS-2 rotatable camera in Station Two. The equipment in Station One cannot be properly identified at this time. 

CVA-10320 F7U-3P Night Reconnaissance Configuration 19520613

     The night reconnaissance configuration again leaves the forward bay empty. Station One contains a shutter trip control and Station Two contains a K37 camera.

CVA-10325 F7U-3P Sub Cockpit Showing Camera Viewfinder 19520613

     The photo above shows the viewfinder for the camera installations when the photography is taking place forward or vertically. For visual reference the nose of the aircraft is to the right in the photo.

     That closes out this installment of the F7U-3P mockup. The final installment will feature a few more details and additional information on the design.

F7U-3P Mockup

     Typical with the majority of Naval Aviation fighter designs from WWII to the 1950's a photo reconnaissance version of the F7U-3 Cutlass was proposed and 12 examples eventually built. The type was not issued for squadron service.

xF7U-3P-Concept-with-Cameras-Airbrused-Photo VAHF Archive

     The photo above is a combination of photograph and artist rendering showing a shorter nose than was installed on the actual F7U-3P aircraft. Interesting array of cameras displayed in front of the aircraft as well.

     Contrast the artists composite concept above with an actual F7U-3P (BuNo 129750) on the Vought ramp. The length of the nose and camera window details vary from the concept to the actual.

F7U-3P-129750-Left-Front-View VAHF Archives

     Found in RG72 at the National Archives are the following images of the F7U-3P mockup.

First up is this image of the whole forward fuselage and cockpit section of the mockup.

CVA-10328-F7U-3P-Mockup-19520613

     Below a closeup of the camera window protective covers installed on the F7U-3P mockup.

CVA-10612-F7U-3P-Mockup-Camera-Window-Covers-19520627

     The following image is of the F7U-3P mockup nose section with all the servicing panels open. The panels allow a tremendous level of access to the cameras, optical sight and associated equipment. The first major disadvantage is illustrated in the next image.

CVA-10316-F7U-3P-Mockup-Service-View-19520613

     This photo illustrates the major disadvantage to having a photo version of the F7U-3. The nose high stance of the aircraft makes camera installation and servicing difficult. The height requires the use of a specialized stand to gain access to the cameras and film..

CVA-10618-F7U-3P-Mockup-Camera-Bay-Access-Ladder-19520627

     Mockup photos from the National Archives RG72, College Park, MD

XF7U-1 122472 September 9, 1948

     Here are some images taken on a mostly cloudy day at the Chance Vought Hartford, CT facility on September 9, 1948, some 67 years ago. The subject is the first XF7U-1 prior to the start of taxi tests. 

     These views show the wings folded with the instrumentation booms that were removed after the first flights due to the vibration caused by them. The wing booms were replaced by a single nose mounted probe. The nose mounted cannons of the F7U-1 are easily visible. Without the full coat of Glossy Sea Blue (ANA 623) paint a number of panel and material details can be seen more clearly. 

CV-31467 XF7U-1 122472 Under tow 19480909 VAHF Collection

     The tall stance of the design is readily visible hand in hand with one of the criticisms that would influence the Crusader and Corsair II is the readily apparent need for stands to access the aircraft. The number, size and complexity of maintenance stands becomes a problem in the crowded spaces of an aircraft carrier.  

CV-31469 XF7U-1 122472 19480909 VAHF Collection

CV-31466 XF7U-1 122472 19480909 VAHF Collection

     While the Cutlass program was moving towards the first flight date it is important to remember that another significant event was taking place in the life of the Chance Vought Aircraft company. During WW II the Government had built a number of modern inland production facilities. Post war a number of these facilities sat idle. The Navy Bureau of Aeronautics approached Chance Vought Aircraft in the fall of 1946 to consider moving to an industrial reserve aircraft plant in Dallas, TX. 

Aerial photo of the former North American Aviation industrial reserve plant in Grand Prairie (Dallas), Texas 1948 VAHF Collection

     During the war North American Aviation had used the facility to build T-6, P-51 and B-24 aircraft. After reviewing the facility and other locations it was decided to ink an agreement with the Navy to move to the  Dallas facility. The announcement was made by the Navy on April 18, 1948 that Chance Vought was going to move to Dallas, Texas. In an internal update to the Dallas move two days prior to the Cutlass photos (in this post) being taken the company reported the following statistics on the move to date:

Total carloads (rail) shipped to Dallas: 164
Total weight of materials shipped: 7,271,972 pounds
Total shipments of household furnishings to Dallas: 132
Total Chance Vought people transferred to Dallas: 204
Total Texans hired: 595

The short life of the first Cutlass XF7U-1 122472

Here is a photo of XF7U-1 122472 on the ramp prior to the application of the last three of the BuNo to the verticals. The photo is probably taken prior to the first flight. Test pilot Robert Baker took her up on the first flight September 28, 1948. Note the date.

From the flight test report "After a series of high speed taxi tests the aircraft was flown once around the airport while the wind conditions were still favorable. The flight was not very extensive due to an overcast at 8000 feet. Handling qualities appeared normal and satisfactory."

The aircraft was lost in a take off accident at Ardmore, OK on September 28, 1949 with test pilot Paul Thayer at the controls. This was flight number 132 for the aircraft.

According to the flight test report 'The purpose of this flight was to have been a further investigation into the high Mach number characteristics of the airplane with differential rudders, two external stores pylons, and with a dummy tank installed on the right hand pylon, The investigation was to be done above 20,000 feet with the afterburners "on"."

"The aircraft was observed to yaw slowly to the left and slowly drop the left wing. The aircraft hit the ground with the landing gear partially retracted and skidded to a stop with extensive damage. The pilot was not injured and no fire developed." (Chance Vought Report 7707 Investigation Of Accident -  XF7U-1 Airplane, BU. No. 122472 On 28 September 1949, page 3)

After an extensive investigation the following summary was provided in the same report on page 12.

"To summarize, the accident is concluded to be the result of a stall either directly or in the process of application of corrective action to the yaw and roll occasioned by low direction stability and late application of corrective action of the rudder and aileron. In the latter case, the low directional stability and the type of corrective action take are contributing factors to the accident."