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Author Topic: Question for the deep thinkers  (Read 1397 times)

Offline Gary Dowler

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Question for the deep thinkers
« on: May 25, 2019, 11:04:05 PM »
Recently I spotted something about the F4U that I had never noticed previously.  I was watching a flight demo, and on a high speed low level pass I noticed that the airplane had a slight, but noticeable, nose down attitude. This was repeated on each low pass.
I wondered if it was something I seeing or imagining, so I looked up several other videos of Corsairs, and noticed the same thing in all low level fly by's.

I surmised that this was due to the AOA of the wing on the F4U, and mentioned this to an old mentor. I was mildly criticized for misunderstanding what I was seeing. I was told this was due to light fuel load on short demo hops.

I wasn't buying it.

I spent some time tonight looking at further videos of other modern flights with various other fighters at similar airshows. P-51, P-47, P-38, Spitfire, Hurricane, FW-190, etc.  All of these, when viewed profile in low level passes at speed, failed to show any peculiar attitude in respect to the wing AOA.

I've seen this with other types such as the B-52, which flies with a noticeable nose down attitude , at least when absent heavy ordinance. 

Is this due to a slight deviation between the long axis of the fuselage and the chord of the wing in the F4U? Or am I deed utterly misunderstanding what I saw in nunerous videos?

Gary
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Offline Gary Dowler

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Re: Question for the deep thinkers
« Reply #1 on: May 26, 2019, 12:07:13 AM »
I may have answered my own question. I found a site with a technical discussion regarding the Corsair design. Turns out I was correct in my assesment that the AOA of the wing is not parallel to the long axis of the fuselage, with the -1's wing being angled up 4 deg, and engine angled up 2 deg, and on the -5 wing angle was increased to 6 deg, and 4 deg on the engine.  The result of it all was that the plane did indeed fly nose down relative to the wing.

Based on this, I would say my original observation was correct. Now to figure out how to explain this without "offending" ......

Gary
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Online Ken Culbertson

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Re: Question for the deep thinkers
« Reply #2 on: May 26, 2019, 05:39:16 AM »
I may have answered my own question. I found a site with a technical discussion regarding the Corsair design. Turns out I was correct in my assesment that the AOA of the wing is not parallel to the long axis of the fuselage, with the -1's wing being angled up 4 deg, and engine angled up 2 deg, and on the -5 wing angle was increased to 6 deg, and 4 deg on the engine.  The result of it all was that the plane did indeed fly nose down relative to the wing.

Based on this, I would say my original observation was correct. Now to figure out how to explain this without "offending" ......

Gary
I was told by my uncle who was a WWII/Korea pilot that it was for better visibility in low level strafing and landing.  Could be an "Old Pilots Tale".

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Offline Ara Dedekian

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Re: Question for the deep thinkers
« Reply #3 on: May 26, 2019, 08:01:09 AM »


      Gary

        Deep thinking gives me an Excedrin headache. So my comment is based on my experience with flying free flight rubber scale.

        Depending on high or low wing models we have to put in two to six degrees of positive angle of attack on the wing relative to the centerline of the fuselage and a zero degree empennage. It's an aerodynamic issue addressing stall characteristics and stability and has nothing to do with fuel load or vision over the nose. I'm hoping the aerodynamicists here will further explain and/or correct me. The FF prop (engine) gets angled down but thats to control the torque of the rubber.

        While we're on Corsair aerodynamics, an under reported feature of the gull wing is that it eliminated the need for wing fillets by attaching the wing to the fuselage at a ninety degree angle. (Aerodynamicists?)

        Ara

Offline Air Ministry .

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Re: Question for the deep thinkers
« Reply #4 on: May 27, 2019, 07:31:28 AM »
Heres One .


Offline Tim Wescott

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Re: Question for the deep thinkers
« Reply #5 on: May 27, 2019, 10:45:46 AM »
Whether it was by design or by mistake, if you build in more positive incidence on the wing, then the airplane will have to fly more nose down to compensate. You may want to check if the F4U was originally designed for ground attack. if it was, that would mean that the designers may indeed have thought about this issue when they designed the wing placement.
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Offline Elwyn Aud

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Re: Question for the deep thinkers
« Reply #6 on: May 27, 2019, 11:11:16 AM »
Another unusual quirk on the Corsair was the addition of a small wedge to the leading edge of the right? wing to get both wings to stall at the same speed.

Online Brett Buck

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Re: Question for the deep thinkers
« Reply #7 on: May 27, 2019, 11:23:10 AM »
The Corsair was also designed to land on a carrier, where seeing over the (very long) nose is also important. They could have raised the pilot's position, or moved it forward (like they did on the Bearcat, or they could dip the nose.

    Even then, it wasn't enough, and the problem was only ever completely solved by the "turning approach" developed by the British.

    Brett

Offline Gary Dowler

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Re: Question for the deep thinkers
« Reply #8 on: May 27, 2019, 11:34:14 AM »
The Corsair was also designed to land on a carrier, where seeing over the (very long) nose is also important. They could have raised the pilot's position, or moved it forward (like they did on the Bearcat, or they could dip the nose.

    Even then, it wasn't enough, and the problem was only ever completely solved by the "turning approach" developed by the British.

    Brett
The prototype XF4U had a very different arrangement. The primary fuel was carried in the wings, which the Navy did not like. Vought was instructed to move the main fuel tanks into the fuselage. The engine was moved forward a foot, and the cockpit moved aft 3' (making the nose 4' longer) to make room for a 233 gallon tank immediately ahead of the cockpit.  If you ever see strips of tape in top of the fuselage right ahead of the cockpit, this was often dont to seal up seams that allowed leaking fuel to get on the wind screen.

I had not known the British developed the turning approach. Interesting. Recalling many film clips from the war, I do recall always seeing our planes on a straight in approach. Interesting.

Gary
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Online Brett Buck

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Re: Question for the deep thinkers
« Reply #9 on: May 27, 2019, 11:40:56 AM »
The prototype XF4U had a very different arrangement. The primary fuel was carried in the wings, which the Navy did not like. Vought was instructed to move the main fuel tanks into the fuselage. The engine was moved forward a foot, and the cockpit moved aft 3' (making the nose 4' longer) to make room for a 233 gallon tank immediately ahead of the cockpit.

   Hence, the need to see over the (very long) nose.

   Brett

Offline Howard Rush

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Re: Question for the deep thinkers
« Reply #10 on: May 27, 2019, 01:22:01 PM »
There appear to be several correct answers.  Besides wing incidence to improve visibility, both light loading and fast flying reduce the angle of attack needed to get the lift required to fly level.  All that stuff adds up for a negative body angle while flying fast with a light airplane.
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Offline Dan McEntee

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Re: Question for the deep thinkers
« Reply #11 on: May 27, 2019, 01:45:49 PM »
   The gull wing was incorporated to avoid having landing gear that would have been excessively long, because the prop was going to be the biggest ever used at that time. They knew enough about carrier ops at that time to know that the landing gear had to be beyond tough. The Bearcat was on the same path but the devised a landing gear that got shorter as part of it's retract system. The turning approach was developed by the British, as they were given examples  as part of Lend/Lease and loved it's capabilities. our Navy was ready to pack it in on it and make it a sole Marine mount and eliminate carrier operations from it's use until the Brits showed them the way. The design went through many upgrades and revisions through the years culminating in the Super Corsair powered with the P&W 4360 as a kamikaze chaser near the end of the war. 14 examples were built by the time the war ended, and the Navy kept them around. The War ended and the Cleveland Air Races started back up again, and cheap surplus fighters made good racing mounts. The Mustang was showing well for itself in post war racing, and a navy Reserve officer name Cook Cleland convinced a higher up admiral to make three of them available to him for Cleveland so the Air Force airplanes would quit showing up the Navy pilots. One was abandoned and eventually was scrapped, the other two were purchased for scrap by a man named Bob Soplata that recognized their worth and took them back to his farm in Ohio and added them to his growing collection of significant war birds. They were eventually purchased by Bob Odeguard and restored to flying condition as they raced as Cleveland. I got to see the red #57 just after it's certification time was flown off and was flown to Reno in 1999. The Blue #57 was finished several years later after some court wranglings, but unfortunately was destroyed in a crash that also claimed Bob Odeguard's life. I think there was a total of seven of the Super Corsairs still around in museums and such, which is amazing given the small number built originally. Corsairs are one of the most difficult to repair and rebuild because of the complex gull wing center spar, but modern technology makes it possible to happen when needed. They are really awesome to see in the air and when in a high speed dive you can hear the noise that cause the Japanese to give them the name  "Whistling Death."
    Have a safe Memorial Day Holiday everyone,
   Dan McEntee
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Offline Gary Dowler

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Re: Question for the deep thinkers
« Reply #12 on: May 27, 2019, 03:04:21 PM »
Dan, I've been privileged to get up close and personal with one of the F2G's back when it was in Doug Champlain's collection in Mesa AZ.  I arranged permission to go in ahead of the crowds to photograph it for a friend.
I got to crawl all over it and take pictures of everything , but was forbidden to get in the cockpit.  Paul Allen owns it now, and it resides at Paine field.   Beautiful plane, and there are only 2 examples remaining. Technically it's airworthy, but he has no intention of flying it.

Gary
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Offline Ara Dedekian

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Re: Question for the deep thinkers
« Reply #13 on: May 27, 2019, 05:42:33 PM »
Another unusual quirk on the Corsair was the addition of a small wedge to the leading edge of the right? wing to get both wings to stall at the same speed.

Offline Air Ministry .

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Re: Question for the deep thinkers
« Reply #14 on: May 28, 2019, 01:34:27 AM »
Drifting off a bit , BUT :

Used to pass this lot around mid / depleted late 60s . Wasnt aloud to have one , even tho it might be ' about 50 pounds ' . I did ask . A deprived childhood . Every 5 year old should have a Vought Corsair ! . >:(




The Kiw's flew the Corsair in Ground Attack , Bombing ( usually ) and Staffing ( usually as well ) in the ' Mop Up ' operations , in the Pacific . With the ' Island Jumping ' Stratagey .
Was still the odd mislayed Jap about in the 70s . Some still hiding from ' the Enemy ' as they were a bit slow in picking up that the War might be Over .



Some more pictures of the boneyards here : https://www.pinterest.com.au/ritchnz/rukuhia-ww2-boneyard/
There were more P-40s , but for some reason I wanted a Corsair .

The Aussies used the  C.A.C Boomerangs at tree top hight , to spot the little nippers . And would toss a Smoke Grenade on the camp site ,
The RNZAF Corsairs would at times be ' Cab Rank ' style , Above waiting for the action .





"  The American government accordingly decided to give New Zealand early access to the Corsair, especially as it was not initially being used from carriers. Some 424 Corsairs equipped 13 RNZAF squadrons, "

Dunno if its napalm in there or hes just flown up from Auckland . S?P

« Last Edit: May 28, 2019, 02:57:42 AM by Matt Spencer »


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