F4U Low Drag Wing Study Part 4

In researching the proposal for the F4U-5 with a low drag wing, I came across this drawing, CVS-13544 for the landing gear in the low drag wing. Major item of interest is the main landing gear would be completely different installation than shown in the general arrangement drawing I provided here (CVS-13541).

This drawing shows a main landing gear that is attached outboard and retracts inboard, This is quite a change over the rearward retracting, rotating wheel version used on the production F4U Corsairs.

On the outboard panel you can see where  "retractable ailerons" (circular arc spoilers) along with short span conventional ailerons are located.

Information from the Vought Aircraft Historical Foundation.

Previous posts in this series:
Low Drag Wing Study Part 1
Low Drag Wing Study Part 2
Low Drag Wing Study Part 3

F4U Low Drag Wing Study Part 3

Rework and new fabrication to support the new wing design included:

• Lateral control would be through the use of "retractable ailerons" (circular arc spoilers) along with short span conventional ailerons.
• Landing flaps will be slotted type extending from the fuselage to approximately 80% of the span of the wing. Whereas the fixed hinge flaps on the F4U-4/-5 only covered 55% of the wing span.
• Armament would be 4 20mm guns with 200 rounds of ammunition. Also eight Mark 9 rocket pylons and two center section bomb or fuel carrying pylons. A centerline pylon completes the external stores provisions.
• Wing folding would be improved to allow operation in winds up to 55 knots.
• Main landing gear would be similar geometry but extensive redesign to fit the low drag wing airfoil. The main tires would change to 30 x 7.7 10-ply high pressure tires instead of the 32 x 8 tires of the F4U-4.
• Due to angle changes the wing to fuselage joint would be reworked.
• Some strengthening to the aft section and stabilizers would be necessary.

Expected Performance Improvement

• The maximum speed at combat power in clean fighter configuration compared to the F4U-5 would be  16 mph at the combat power critical altitude.
• The maximum speed difference at sea level would only be 7 mph.
• Stalling speed reduction of 1.3 mph than a standard F4U-5 with the flaps down.
• Stalling speed increase of 3 to 4 mph with the flaps up over a standard F4U-5.
• The angle of bank in the first second and rate of roll is estimated to be as much as a 10% increase at 300 mph over the standard F4U-5.

Four things led to the increased speed estimates:

• Higher critical mach number due to the change in airfoil from NACA 230 series to a NACA 64 series.
• Improvement in critical mach number for the wing inlet duct
• Reduction in drag and surface roughness due to the use of Metalite wherever practical
• Elimination of wing flap external hinges.

Previous posts in this series:
Low Drag Wing Study Part 1
Low Drag Wing Study Part 2

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."

New Birdcage Corsair Reference Book!

Aircraft Pictorial #7 F4U-1 Corsair Volume 1 by Dana Bell has been published!

Before I write further, I corresponded with Dana during some of the research on this book. I do not have anything to gain from the success of this fine volume. It will do well without my help!

Dana has produced a volume for those of us interested in the technical details of the aircraft. I personally enjoy reading about and seeing the mechanical details of aircraft. How the Engineers innovated new ways to advance the technology and the modifications required have always been of interest to me.

This is not a rehash of the famous stories and myths about the Corsair. This slim volume of 72 pages is packed with information both textually and visually appealing to those interested in the air frame, it's modifications and the colors it wore. Where else do you get to see Vought supplied work stands, stall strips and flap gap doors? Even better a Corsair with outer wing panel drop tanks, now that's something new to see!

This volume fits well with the Kingfisher and Vindicator books already published in this series. If you are looking for another combat history of the F4U this is not your book. If you are looking to learn some details about the Corsair that you didn't know, this is the ticket!

I am looking forward to the "raised seat version" of the F4U-1 that will be the companion volume to this one. For the time being, I am going to dig out my 1/32 scale Birdcage Corsair for a closer look.

Special SU-2 Bureau Number 9095 1932-33

Command aircraft of the US Navy in the 1930's were painted in special schemes. In the case of this Chance Vought SU-2 is is Admiral Blue fuselage, Chrome Yellow upper wing with the other color being aluminum. There was also a flag older mounted on the side of the aircraft for noting when the Commander was on board. 

The wheel pants really give the aircraft a cool 1930's look to what is normally a plain wheel and tire assembly. Something interesting about the photos. In the upper photo the tail hook is clearly visible, but in the next two photos the tail hook is scratched off the photos.

According to John Elliot's book this aircraft belongs to Rear Admiral John Halligen, Commander Aircraft, Battle Force. This image looks similar to the image in Elliot's book. Reference page 37 of  "The Official Monogram US Navy & Marine Corps Aircraft Color Guide Volume 1 1911-1939", Photos from the VAHF Collection

What a beautiful airplane! I bet she had a distinctive sound with those short, individual exhaust stacks.

V-354 Two PlaceTrainer

     In late 1945, the concept of a Two Place Trainer version of the F4U was in discussion between Vought and the Bureau of Aeronautics. The potential program was given a Vought number of V-354.

The trainer is a conversion of the F4U-1D from a single place to two place aircraft. The airframes converted would be from surplus US Navy stocks, there would be no new build airframes. By late January 1946 the Navy had ordered 50 F4U-1Ds held for possible use in the program. 

To convert a F4U-1D into a Two Place Trainer the fuselage front section would be exchanged for one containing two full sized cockpits. The single large fuel cell would be traded for four smaller fuel cells. The new fuel cells would be located under the cockpits (2) and one each in the outer wing panels. The outer wing fuel cells would displace two of the machine guns and ammunition from each wing leaving the aircraft with only two guns, one in each wing. The aircraft would retain full arresting and catapulting provisions to support aircraft carrier operations. Lastly, the V-354 would retain the same engine, bomb and rocket provisions as a standard F4U-1D.

Money was approved for the conversion of one aircraft for a mock-up and in May 1946 it was inspected and approved. 

Money was allocated for the conversions in July 1946. It was also determined that with the current level of engineering work on the V-346 (Cutlass) there was no capacity in-house to take on the Corsair Trainer conversions. 

The Navy department attempted to have the work performed by Naval Aircraft Factory or possibly Goodyear Aircraft. Eventually it was decided to obtain a proposal from Edo Aircraft that had sufficient capacity at the time to accomplish the project.

As Edo was preparing the proposal to perform the engineering work and manufacturing of two prototypes in mid August 1946, the feeling was the current spending reductions and a tight budget from President Truman might have a negative affect on the project.

By early December 1946 the project was cancelled due to a slashing of Navy Department funding. The Navy retained interest but it was gradually shifting to a two seat jet aircraft instead of the propeller driven Corsair.

As a result, there was only a mock-up of the Corsair Two Place Trainer ever assembled.

Reference material from the Vought Aircraft Historic Foundation Archives, National Archives RG72

Type Spec 149 and the V-416 Vigilante

     In 1957 the United States Navy issued a Type Specification 149 for a carrier based all weather attack aircraft. Of the eight companies that responded, three made the short list including the ultimate winner Grumman with the A2F Intruder and Vought's V-416 Vigilante.

Report 10934A Page 3 Rev 7/29/57

"Chance Vought Aircraft has been invited to participate in a design competition for an all-weather, low-level, carrier-based, two-place, attack airplane in accordance with Type Specification No. TS-149 dated 19 February 1957 as modified by Amendment No. 2 dated 24 May 1957."

"Two separate configuration will be proposed - one a twin J-52 engine airplane which meets the specification requirements and contains Contractor furnished and developed electronic equipment called out in Type Specification and Government TS-149 that the Contractor considers essential for optimum mission accomplishment. This airplane will be identified as the Model V-416A. The second configuration will be identified as the Model V-416B and would differ from the Model V-416A in that it will contain Contractor and Government furnished and developed electronic equipment which meets all the requirements called out in Type Specification TS-149."


V-416 General Arrangement

     As with any aircraft, maintenance considerations dictate significant demands on the design. Ease of maintenance to enable the aircraft to be operated at a lower overall cost and the ability to turn the aircraft around after a mission are important. Here is a drawing showing some of the maintenance access panels.

     Interesting is the non-retractable aerial refueling probe attached to the number 2 (right) engine nacelle unlike the design Grumman adopted on the A2F that was right in front of the crew that was also not retractable.

     Also of interest the major components identified for the production process.

     Finally the external stores diagram to illustrate both the locations and the types of stores the aircraft would have carried if it had entered operational service.

      Here is a closeup of the various external stores combinations that were proposed for the V-416.

     Once again the information from this post came from the Vought Aircraft Historical Foundation archive material.

NASM OS2U-3 BuNo 5909 Kingfisher

I had the opportunity to take a few pictures of this veteran Kingfisher over the weekend. OS2U-3 BuNo 5909 served in WWII aboard the USS Indiana among various assignments.Here is a link to my photo set on Flicker: OS2U-3 BuNo 5909

A2U-1 Cancellation

     The reason for the cancellation of the A2U-1 program was in a November 19, 1954 press release from Chance Vought Aircraft.

In part it read: " Unavailability of suitable engines for an attack version of Chance Vought Aircraft's twin-jet Cutlass fighter has resulted in Navy cancellation of a order for 96 attack airplanes.

          F.O. Detweiler, president of the company, emphasized that the cancellation applies only to the attack version, designated the A2U-1. Other versions of the F7U-3 Cutlass will continue in production.

          The Navy announced in Washington that cancellation of orders for 200 F3H-2 Demon fighers scheduled to be built by McDonnell Aircraft, of St. Louis, Missouri, for the A2U airplanes and for engines, engine spares, radar equipment and other aircraft components for the two aircraft totaled $372,000,000 in a revision of its jet aircraft procurement program.

          The announcement said one of the reasons for the cancellations was delay in development of engines for the airplanes."

     
                                          CVA-29565 F7U-3M General Arrangement. View
                                          Looking Aft With Two 2,000 LB. Bombs On Center
                                          Section Pylon & Outer Panel Pylon Installed. 11-3-55

Press Release and photo from the VAHF archives

Engineering Project Plan Model A2U-1 Airplanes, Summary of 17 March 1953

A departmental correspondence that detailed the proposed changes to transition the production of the F7U-3 to the A2U-1.

"These were the proposed changes to assure delivery of the first airplane by September 1954.

Basic changes:

1. Addition of Aero 14C launchers, three on each outer panel, and five on the fuselage.

2. Addition of outer panel fuel to provide maximum radius of action and endurance. (This is not really a change, as it was previously agreed with Materials and Manufacturing to provide a common outer panel for the F7U-4 (Sparrow), F7U-3P, and A2U-1 aircraft).

3. Replacement of the right hand forward center-section self-sealing fuel cell with a bladder cell. Addition of internal and external inerting for all center section fuel cells (the same type of inerting will be provided on the interchangeable outer panels).

4. Redesign of main landing gear to replace present 30 x 7.7 wheels and tires with 34 x 9.9 wheels and tires. (In order to assure delivery of the first airplane, a special extra ply 30 x 7.7 tire will be purchased which can be used on the present F7U-3 landing gear. As soon as the redesigned landing gear for 34 x 9.9 tires is available, it will be retroactively installed on all airplanes).

5. Rework of fin stub to accommodate 34 x 9.9 main wheels and tires.

6. Addition of armor protection under the pilot, and under the main fuselage fuel cell pumps.

7. Addition of center section trailing edge area between the vertical tails and the fuselage, to provide increased load carrying capacity and proper balance of the airplane.

8. Removal of the Aero 5A fire control system, including AN/APG-30, and replacement with a simple gun sight.

9. Installation of Mk3 Mod4 bomb-director equipment.

These are the basic changes that will be made to convert the F7U-3 into the A2U-1. There is a possibility (still being investigated) that a change will be required in the machining of the main beams, in order to raise the strength of the airplanes.

The changes outlined above are considered to be the absolute minimum that will assure a satisfactory attack airplane when the A2U reaches the Fleet."

Signed F. Mann

                                          An actual picture of a A2U-1 on the production line.

                                        Memo and photo Vought Aircraft Heritage Foundation

F4U Low Drag Wing Part II

A little further research:

In discussions between Chance Vought and the Navy Department, Bureau of Aeronautics in December 1945, it was verbalized that a sound policy of continuous improvement of the F4U-4 and the design of the F4U-5 airplane, which was to be improved to include a low drag wing, with the purpose to bring the top speed up to 500 mph should be pursued. The interest was driven due to the slow development and production of jet airplanes for the Navy. The need to stay competitive at the top end of performance with land based aircraft for Naval Air Forces was partially driven by the Kamikaze experience that was still fresh in the minds of the operational forces.

More later...............