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Monday, December 22, 2014

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



Thursday, December 18, 2014

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

Saturday, December 13, 2014

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."





Tuesday, December 9, 2014

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.


Saturday, December 6, 2014

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.