1. #21
    R_Target's Avatar Banned
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    Originally posted by vocatx:
    A friend of mine performed the same test under the same conditions just yesterday. Here are his findings for the Hellcat:

    F6F-5 HELLCAT
    Deck: 317mph
    3km: 336mph
    5km: 351mph
    7km: 375mph
    Published: 303mph @ Sea Level. 375 to 386 at 7km, depending on source.

    Did you correct for true airspeed, or are your figures indicated airspeed?

    He is testing several other aircraft as well. Watch for Joop's test results to be posted soon on the Warbirds of Prey forums. (He's having surgery tomorrow, so it may be a few days.)
    Yup, TAS from the gauge in no-cockpit view, and then just converted. Those numbers are close to mine. If you converted to TAS from IAS on the speedbar, that may explain the slightly slower results from your friend's test.<div class="ev_tpc_signature">

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  2. #22
    Nimits's Avatar Senior Member
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    Sorry but my book on navy aircraft in ww2 says that the f6 WAS a direct response to the zero
    That is an understandable myth, born through a couple of coincidences, and published in many books. The F6F was the exact right plane to defeat the A6M, heavier armed, faster at all altitudes, and more manuverable at high speeds and altitudes. The timely capture of an intact flyable A6M several months before the F6F entered service then lead many to believe the F6F's performance had been tailored against former's test results. Finally, the career of the F6F somewhat parallelled the A6M, entering service in 1943 while the Zeros still remained competative, beginning to be phased out in late 1944 in favor of the F4U after a majority of Zeros had either been destoryed or assigned to secondary duties, and being quickly replaced by the F8F and F4U in as soon as the war was over and their were no more Zeros to fight.

    Originally posted by WOLFMondo:

    The Hellcat is within 5% of any figures anyone has produced in regards to its speed.
    Which could still be 20mph to slow. Whether or not that is acceptable in a survey sim with a over a hundred aircraft (not counting variants), I really cannot say. It seems to me, even if achieving perfection is not possible, the speed could be brought a little closer to reality, say within 2%-3% of real life top speed.

    The real issue, though, may be that those performance figures are off. Supposedly tests were made where the F4U and F6F flew side by side, yet the F4U indicated airspeed was considerably slower (around 20 KIAS, if I remember correctly). It has been supposed that poor placement of the pitot tube resulted in incorrectly too slow air speed indications for the F6F. Even if the plane flew spot on at its published figures, it might still be flying 20 knots too slowly in the game, relative to everything else . . .

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  3. #23
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    Here's the side-by-side comparison by Corky Meyer:

    Navy taste test...: Hellcat vs. Corsair
    Meyer, Corky

    If the contest between the two airplanes had been for beauty of design, we would have given in immediately. Our baby, the Hellcat, was beautiful to us, but in comparison with the graceful lines of the Corsair, the Hellcat looked more like the box it came in than a new Navy fighter. We always used the euphemism "functional looking" instead of "ugly" to describe it

    We were sure that Vought would have a difficult time meeting the Navy's demands, as most of the Corsair's deficiencies would require major changes in configuration. We were also steeped in the tradition that Grummanites could always make better Navy fighters than Connecticut clam diggers; thus, our tasks would be accomplished in a trice. Our performance-improvement challenge turned out to be much easier than we ever hoped, but the aileron problem turned out to be nearly impossible.

    The Navy was right

    As long as we had the enemy in our hangar, we decided to conduct a witch-hunt into its entrails. In my first flight, I discovered the Corsair did indeed indicate 20 knots faster and did have really smooth and powerful ailerons compared with our Hellcats. But, as we had heard and as was completely obvious, the cockpit was wretched from many standpoints. The most glaring deficiency was the absence of a cockpit floor! Behind the rudder pedals, only two, small heel panels offered any protection against dropping a pencil, a chart, or earphones, etc., into a three-foot-deep, yawning black hole. Consider the havoc this would cause if the pilot's relief tube dropped down there on a very, very long mission!

    To simplify the evaluation and reduce data, we decided to test-fly the Hellcat and the Corsair in close formation. Instead of comparing complex calculations, performance could then be compared directly at the critical altitudes of the main stage, high and low blower altitudes of the engine's superchargers, and from cruise to high-speed, level flight with water injection. We also included some formation dives to learn which airplane was the slickest

    Performance almost equal

    Except for the Corsair being 20 knots faster than the Hellcat in the main, sea-level, supercharger stage, both fighters had almost exactly the same speed at the low and high blower stages from 5,000 feet altitude up to service ceiling! In essence, they had the same performance. Our formation flights showed that both airplanes (with similar power settings) were in closely stabilized formation at all altitudes tested above 5,000 feet Sometimes, the Corsair would slowly gain a lead of 100 to 200 feet after five minutes of stabilized power flight, and sometimes, the Hellcat would do the same. Considering that both airplanes had the same engine, propeller, gross weight, wingspan, etc., they should have had about the same performance. We did notice that during these runs, the Corsair always had about a 20-knot indicated airspeed (IAS) advantage! We didn't realize just how embarrassing it would be to solve that dilemma.

    The reason the Corsair was faster in the main stage blower was that its engine and carburetor were provided with ram air coming in directly from the forward-facing wing duct, whereas the Hellcat had the carburetor air coming in from the accessory compartment of the fuselage just behind the engine, with no ram air effect Our airplane was getting carburetor air at the same pressure as it would have were it motionless on the ground, and the Corsair was getting carburetor air supercharged by the speed of the airplane giving it more power (speed) in the main stage blower. In both aircraft, however, the designs were similar in that they provided ram air to the low and high blower stages. Our engineering department defended its position because taking the warmer air for the main stage blower would prevent inadvertent carburetor icing engine failures. Many Wildcats that had ram air in the main stage like the Corsair were lost because pilots failed to take precautions in time to avert this type of disaster. The Hellcat design was reviewed and approved by the Navy. I had had a carburetor icing accident during final approach on my first flight in a Wildcat a few months previously; it resulted in my first deadstick landing and a vertical ground loop. I therefore heartily agreed with the Navy's decision.

    IAS performance equalized-the hard way

    After noting the 20 knots indicated airspeed difference that had caused all the "lower performance" ruckus for our Hellcat, we eagerly decided to change the airspeed system so that it would read evenly with the Corsair when they were in formation. We had taken a lot of flak from all who had flown both airplanes (but not in formation) and, therefore, everybody 'mew' that the Hellcat was inferior in high-speed performance. We liked our simple and less complicated airspeed system with the static and dynamic orifices on the same boom, but we decided to go whole hog and put the static orifice on the fuselage (like the Corsair) to tailor the system to read 20 knots higher. We tried several orifice locations to get the required reading. After I had done a thorough testing of the final system over the entire flight envelope-or so I thought-I proudly flew the airplane to the Naval Air Test Center at Patuxent, Maryland for an evaluation. We soon found out that we had not purloined the Corsair airspeed system design thoroughly enough.

    We soon received the Navy's glowing report of the new system; and it went on to say that the Air Test Center had never tested an airplane with such remarkable low-speed performance in its entire history. They found that in a left side slip with the wheels and flaps extended, the Hellcat could fly at zero airspeed. Wonder of wonders! Grumman led the industry again! Upon re-evaluation, we found that the engineers, inexperienced with flush static airspeed systems, had designed ours with only one orifice on the left side of the airplane, and it was very unbalanced with the flaps down. As the senior engineering test pilot, I was in deep doo-doo for not testing the new system in all side-slip conditions. A dualorifice system way behind the lowered flaps (similar to the Corsair's) finally provided a satisfactory means to give the Hellcat a cockpit indicated airspeed reading comparable to the vaunted Corsair's. That was the last we heard of the Hellcat's performance gap with the Corsair. Performance case closed.

    Hellcat ailerons improved-the NACA way

    During this time, our flight-control engineers designed all kinds of aileron contours and shapes. We tested them to their limits, but to no avail We just could not get the same delightful low forces and high rolling performance as the Corsair had so ably demonstrated. We eventually realized that the high dihedral angle of the Hellcat's wing produced exceptionally high lateral stability, which was the cause of the low rolling rate of our ailerons. To change the dihedral of the wing meant completely redesigning the complicated wing-fold mechanism where the dihedral angle of the wing was formed. That was a real no-no in wartime production. We even went as far as making an exact set of molded plywood ailerons to the Corsair's contours, but we met with zero success. The very low lateral stability that we measured in the Corsair gave its ailerons great power and produced the fabulous rolling rate. They were sim ply not fighting as much inherent lateral stability as we were. We finally incorporated the newly invented NACA spring tab for the aileron; it did the trick by lowering the aileron stick forces over 50 percent, thus allowing the pilot to get full aileron deflections at speeds of 100 knots faster than he could before. Navy pilots agreed that the spring tab ailerons did close the rolling performance gap of the two competitors.

    To everybody's happiness (except the Japanese's) these ailerons were introduced on the F6F-5 early in 1944. To further increase Japanese joy, we retrofitted many of the 3,000-plus F6F-3s that had been delivered to the Navy without spring tab ailerons with spring tabs.

    On one flight during full-power performance testing at 25,000 feet, I had the chance to see just what the practical benefits of the Corsair's low lateral stability would be in an emergency. Pat Gallo, one of our other experimental test pilots, was flying the Corsair; I was flying the Hellcat. We were at full power heading toward Bermuda when I noticed that Pat no longer answered my radio calls. I was trying to remind him to check his estimate of the differences between our speeds. When I finally passed his Corsair, I saw him peering at me very glassy eyed, in a real daze. I also noted that he was wearing one of the unsafe, light gray Mine Safety oxygen masks. I thought we had destroyed those masks many months before after having serious problems with them at high altitude. We were now using the dark green Navy-issue masks with the balloon bag under the pilot's chin; the bag clearly showed the oxygen flow by its expansion and contraction with each breath.

    I immediately realized that I was faced with making one of the most critical decisions I would ever have to make for a fellow test pilot I was unable to communicate with Pat and I knew that in another 10 minutes at full power he would be halfway to Bermuda. He would then run out of gasoline over a very cold and unwelcoming winter Atlantic Ocean. It became quite clear what I had to do, but I worried that my actions could have dire consequences.

    I slowed to formation speed on his left side and closed in to him until my right wingtip was just under his left wingtip. I then gave a strong left push to my stick and rolled him into a 30-degree right bank. His Corsair started down in a long, slow spiral with me in traiL I did not know whether my actions would lead to a steep dive to the water or not, but I knew I had to do something. With the luck of the century, the Corsair's very weak pitch and roll stability slowly took over, and we leveled out heading back to Long Island at about 19,000 feet. Much less hesitantly, I then repeated the maneuver twice until, at about 9,000 feet, he started talking to me in a most querulous and angry tone inquiring which damn maneuver we were going to do next Using my most diplomatic tone I told him that we were very low on fuel and that he should reduce power from full throttle to cruise and return to base with me. His regular fiery temperament seemed all too docile until he said that he wasn't feeling too well and suggested that I talk him through his landing. On the ground, he confessed that he didn't remember anything about the flight from climbing through 10,000 feet to awaking at 9,000 feet before we landed. Needless to say, I now had great comments about the Corsair's weak lateral stability and many more foul ones about the Mine Safety masks still in our ready room lockers.

    A very jumpy takeoff

    Before measuring Corsair takeoff performance, I performed the usual required stalls in all configurations. This model of the Corsair had the new and improved stall tripper wedge on the right wing to improve stalls. It was quite clear to me that the Hellcat was much more docile and controllable during and after stalls, especially in the landing-condition accelerated stalls. The Corsair had more of an abrupt wing drop in the normal stalls and was more difficult to un-stall than the Hellcat. Even worse, the Corsair did a totally unexpected double snap roll when performing a 5G accelerated stall in the clean condition. During these tests, I should have been more impressed with the Corsair's reactions than I was. The Corsair was really talking to me.

    We had found that the Hellcat could shorten its takeoff roll by about 100 feet in a calm wind if the tail was raised to level flight position during the first part of the roll and then slammed down at minimum takeoff speed. We named this a 'lump takeoff' (versus the normal three-point type). This became the standard way to make a short takeoff in the Hellcat-not so in the mighty Corsair.

    My Army doctor brother was visiting me at Grumman on the day we were to perform minimum-distance measured takeoffs in the Corsair, and he was out on the runway to watch the proceedings. After making 10 measured three-point takeoffs in the Corsair, I told the engineers that I was going to start jump takeoffs. I pushed the stick forward and waited until the speed indicated 66 knots; then I slammed the tail down onto the runway as I had many, many times in the Hellcat Lo and behold! As the tailwheel went down on the runway, I got a very strong wind from the left side of the cockpit because the airplane prematurely left the ground, instantly yawed 30 degrees left, stalled, dropped the left wing, fell to the ground and departed the runway promptly to the left without any help from me. We were headed at full power straight into a batch of Hellcats on the delivery line. Navy delivery pilots who have flown from Grumman's Bethpage airport know there isn't much empty space there, and they would thus understand the interesting but unplanned path the Corsair was grinding out for me.

    The Corsair's action was so precipitate that it seemed as if it took me way too much time to start taking prudent defensive actions. I finally yanked the throttle back, raised the tail so I could see what the near future held for me and began a frantic braking on what happily proved to be hard-packed, dry ground. I stopped about 50 feet from the nearest Hellcat in the delivery-line area! I sat there for a while until the earth stopped trembling, then I slowly taxied back to our experimental flightline and decided to call it a day for jump takeoffs. While we were having cocktails that evening, my brother hesitantly asked me if I did that for a living every day.

    Epilogue

    The Corsair's production line benefited in many ways from its Hellcat evaluation. Reducing the oleo bounce, making further improvements to its harsh stall characteristics and enhancing the forward visibility by extending the tailwheel and raising the seat were easy ones to incorporate into the production line. But several of the needed fixes were impossible to insert into the production line until the major changeover of the F4U-4 model in late 1944. The Corsair's cockpit internal layout, for instance, required a complete redesign, and that was impossible to do with the high wartime production rate that Vought was striving for in 1943.

    Forward visibility for the Corsair was never as good as the Hellcat's because of the design of its wing center section. In a fighter, fuel is usually required to be on its center of gravity to keep the flight characteristics within satisfactory limits. The Corsair was originally designed to have the fuel in the wing center section, and the first few prototypes did have it there. But the inverted-gull-wing design was so complicated to manufacture that those tanks had to be removed and a fuel tank had to be placed on top of the wing in a fuselage extension-where the cockpit had been. Placing the cockpit four feet farther aft gave the Corsair its very impaired forward visibility, especially in the landing configuration. This poor forward visibility also greatly reduced pilot lead estimation capabilities in deflection gunnery runs. The long nose was as endemic to poor visibility in the Corsair as the design of the wing dihedral was to the low rolling performance in the Hellcat

    The Hellcat, with its straight wing center section, could be designed with all of the fuel on the CG. Thus, the cockpit could be positioned just behind the engine to provide excellent forward visibility for aerial gunnery, carrier approach and even after flare-out on landing. It was also attached to so much structure around the center of gravity that it gave the pilot excellent crash protection. Hellcat pilots gave Grumman its nickname "the Grumman Ironworks."

    The lack of satisfactory forward visibility caused many carrierlanding accidents in the early Corsair series until the F4U-4 came into squadrons late in the War. Because of high accident rates, Corsairs were pulled from carrier operations three times during the War. In land-based operations where higher-speed wheel landings could be used to improve forward visibility, the Corsair had a very good safety record.

    In summary, any objective analysis must acknowledge that the United States and the U.S. Navy were fortunate indeed to have Grumman and Vought to produce the "Fustess with the mostess" so soon after Pearl Harbor. Part of the heat in the discussion to decide which was the better airplane was generated by the fact that both planes met the requirements for carrier and land-based uses extremely well

    This writer just might have been a little less biased if the Chance Vought Corp. was sending him a monthly retirement check of the same size as Grumman has been doing for the last 17 years. If, however, the late Boone Guyton, who was the project test pilot for all models of the Corsair (and was an old friend) was buying the beer, I would agree heartily with him that the "bent-wing bastard" was the "greatest fighter in aviation history!"


    Copyright Air Age Publishing Dec 1998<div class="ev_tpc_signature">

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  4. #24
    ICDP's Avatar Senior Member
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    Great read R_Target, thanks for posting it.

    After reading the results of your friends test I decided to test the F6F-5 again under the following conditions.

    Crimea map, 12:00 noon, 100% fuel and internal ammo. 110% power withe WEP enabled. Readings are taken from the TAS view.

    SL 521kph (324mph)
    1K 527kph (327mph)
    2k 517kph (321mph)
    3k 538kph (335mph)
    4k 565kph (351mph)
    5k 575kph (357mph)
    6k 605kph (376mph)
    7k 621kph (385mph)
    7.3k 613kph (381mph)

    Here are those figures drawn onto an official USN F6F-5 speed graph. I believe the line marked 2 on the graph is for combat power. If this is the case then the F6F-5 in PF is around 10-15mph too slow at quite a few altitudes. The chart I linked to earlier in this thread gives the F6F-5 speed of 399mph at 20,100ft. Despite this it is still modelled within acceptable tollerance levels and I doubt it will be fixed. Other aicraft suffer a similar problem and this variance has now become normal for quite a few aircraft in PF.

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  5. #25
    __________________________________________________ _________________________
    ICDP-I had uploaded this file previously to show that the F4U was reaching its official speeds and was not 10mph too slow at SL. I simply linked to it again to save time rather than uploading the original version.
    I hope this didn't cause confussion.
    I haven't tested the F6F for quite a while but at SL it seems pretty spot on and about 10-15mph too slow at critical alt.
    __________________________________________________ _________________________


    I don't think the sea level V-max speed of 355mph for the Corsair is accurate according to the speeds the Navy got in the "clean condition" of wartime combat loaded Corsairs. The problem with IL2/PF is that for the most part Corsair performance has been lumped sumed together for all models without much difference. My dad flew this plane and said he had no problem hitting speeds over 370mph on WEP at sea level.

    You also have to be very careful because many of the speed tests the Navy conducted were with wing pylons & drop tanks. Look specificaly for "clean condition" speed tests.

    Here is a great web site with Official Naval WW2 Flight Tests
    http://www.geocities.com/slakergmb/id3.htm

    Notice the 38lb wing loading on a fully combat loaded Corsair. Also notice the emergency take off rating & distance. IL2 can't match these ratings at all.


    http://www.geocities.com/slakergmb/19728170.jpg

    Navy 366mph sea level V-max in "Clean Condition"


    Notice Sea Level speeds much better than IL2. The Corsair is at least 10mph too slow at sea level in IL2/PF.


    __<div class="ev_tpc_signature">


    The Yo-Yo is very difficult to explain. It was first perfected by the well-known Chinese fighter pilot Yo-Yo Noritake. He also found it difficult to explain, being quite devoid of English.
    ? Squadron Leader K. G. Holland, RAF.


    It is generally inadvisable to eject directly over the area you just bombed.

    ? USAF Manual


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  6. #26
    ICDP's Avatar Senior Member
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    This is an F6F thread Kahuna.
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  7. #27
    Originally posted by 609IAP_Kahuna:
    My dad flew this plane and said he had no problem hitting speeds over 370mph on WEP at sea level.
    What plane ? There were lots of Corsairs, was the F4U4 by anychance?<div class="ev_tpc_signature">

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  8. #28
    ICDP-This is an F6F thread Kahuna.
    __________________________________________________ __________________________________________________ ______________________


    Rgr that but you posted incorrect F4U flight data (V-max sea level speed)and called it correct. Your red underlined sea level speed for the F4U. I hope you are not the guy that Oleg is listening for this speed because it is at least 10mph too slow. If you lool at the Navy Comparison Flight Tests between the P51B vs F4U1-A the sea level V-max speed is listed again at 366mph and with as little as a 5"Hg boost hit 376mph & 435mph at 18,000ft. The Corsair was a very fast bird from sea level to just over 20,000ft.

    I didn't post about the Hellcat yet but if you check R-2800 emergency take off rating in a "calm" or zero wind condition it also applies to the Hellcat's take off distances. Neither the Hellcat or Corsair have the correct take off power, combat loading or take distance on a static carrier according to official US Navy Docs. They are both underachieving in IL2/PF.



    __________________________________________________ __________________________________________________ _____________________
    mynameisroland --What plane ? There were lots of Corsairs, was the F4U4 by anychance?
    __________________________________________________ __________________________________________________ _____________________


    Isn't it great when people try to be smart a_ _ but dont bother to read or even look at the flight test data before responding ?

    If a 1943 F4U-1 Corsair can hit 376mph at sea level and 435mph at 18,000ft do you even have a clue what a F4U-4 would do ?
    What part of this don't you understand ?

    http://www.geocities.com/slakergmb/23d60700.jpg


    F4U-4 Speeds in "Clean Condition" 384mph at Sea Level & 464mph at 20,500ft



    F4U-1D vs F6F Speeds



    F4U-1D vs F6F-5 Climb Rates

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    The Yo-Yo is very difficult to explain. It was first perfected by the well-known Chinese fighter pilot Yo-Yo Noritake. He also found it difficult to explain, being quite devoid of English.
    ? Squadron Leader K. G. Holland, RAF.


    It is generally inadvisable to eject directly over the area you just bombed.

    ? USAF Manual


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  9. #29
    Kocur_'s Avatar Senior Member
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    If a 1943 F4U-1 Corsair can hit 376mph at sea level
    Do I see "Special Flush" at 376mph/65''Hg line in the top chart, dated March 1944 btw?
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  10. #30
    I can see this debate going on for weeks, but if you look at flight tests between the Corsair and Hellcat you will see very similar numbers.

    The Hellcat had the exact same WASP 2800 that the Corsair did. The Hellcat was lighter than the Corsair. It doesn't take a genius to figure it out.

    I'm not saying they both clones, but definantly closer than what Oleg would have you believe.

    Originally posted by Hoarmurath:
    Development of the hellcat started in 1940, and the first prototypes were ordered by USN in 06/41. I don't see how it could have been an answer to the zero.

    The plane was faster than zero, good dive speed, good climbing ability. It had many advantages over the zero. Maneuverability was not one of them.

    It's speed was good, but it was still slower than F4U.
    <div class="ev_tpc_signature">





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