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Thread: SOH P-61 project

  1. #351
    Home finally!

    A few notes about CG: A speed stable aircraft will have it's trim vary a bit over the speed range. If it did not it would not be speed stable, dropping the nose with loss of airspeed and tending nose rise with increasing airspeed. CG changes with loading and often with fuel consumption. So there is no perfect CG that remains involiate.

    With an aft CG longitudinal stability is reduced, and can become negative! Forward CG requires a large tail downforce and is very stable, perhaps so stable as to not reduce manuvering capibility, such as being able to execute a flair on landing. FS does not directly model tail force and CG stability, but applies modifiers to the wing moment.

    So a plane with a CG such that it requires zero trim for takeoff or iniial climb will have to be trimmed for cruise, and on and on. It really is a matter of coming up with a CG that works for the range of possible loadings and stays within the handling envelope for various speeds and manuvers. Fighter aircraft with straight wings tend to have little CG movement, depending on location of droppables and ammunition and their location. Some fighters such as the P-51 that had aft fuselage tanks had quite a CG movement during flight. A good thing as the handling was quite poor with the initial aft CG. A transport aircraft, such as the DC2, that I worked on, required consultation of a load sheet to set the proper trim setting for takeoff, as loading over a long fuselage could result in widely varying CG's and trim values. By contrast the F4U had most of it's consumables and fuel near the CG and a takeoff set of trim settings could generally be specified.

    So the question remains, where in the speed range do you desire the plane to be a zero trim?

    Cheers: Tom

  2. #352
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    My basic rule of thumb for zero trim is the cruise speed, or in this case slightly faster than cruise at 250 mph. That speed still lends a feeling of authority to the plane while covering a decent amount of ground without making a person fel like its taking forever to get somewhere..
    I personally plan on making this my primary aircraft to fly in fsx, its just that good. So needless to say, i'm looking at all the things i would expect from my own personal aircraft..
    Although i totally agree and concur with you regarding CGs, the driving impetus to finding the "exact" static CG is that when i reach a speed to maintain during a flight, i only want to set the trim once and be able to leave it alone.. to do that, the plane has to be perfectly balanced. I understand the difficulties involved in that. When i was building the p-36, i achieved it, as i did on the F-14 and Vulcan, but other planes have not been so agreeable, and the P-61 is one of the latter. Well get there though .. I have confidence in our skills and abilities..

  3. #353
    A plane without the need to trim has no speed stability. Perhaps not too imporatant in FS as we have generally no real speed feedback feel through the controls. We manuver visually with regard to view and insturments, whereas much of the manual flight of aircraft is through the feel of the aircraft interfacing with desired speed and flight path. Almost all of the plane I have flown need a lot of trim adjustment through the various phases of flight. Many jets have considerable trim changes with thrust. This can be usefull as (for instance) one can make a very fine speed and path adjustments on say an ILS via thrust alone.

    My Supercub needs a bunch of turns of the trim crank with speed change and flap extension. Speed stability is an important factor in the ablity to fly a very precise approach with good speed and path control. Especially important in carrier aircraft!

    To test for speed stability, reduce the power without any trim or elevator inputs, does the nose fall and tend to keep the aircraft tending toward the initial trimmed speed? Negative speed stability would have the nose rise with power reduction (ignoring any thrust induced pitch).

    In real (not FS) aircraft speed (and pitch) stability is largely determined by the relative positions of the CG and the CL. As the downforce on the tail varies with speed (no trimming change) the applied pitch moment changes. However if the CG is at the CL, the plane will have no pitch stability and almost no force required to effect very large pitch changes. At this point it becomes like ballancing a pencil on your finger. Aft of that the plane becomes dynamically unstable and without continuous inputs the plane will dynamically diverge into uncontrollable flight without intervention. Computer fly by wire systems can be used in fighters to fly an otherwise dynamically unflyable airframe and take advantage of manuverabilitues that result from such configurations.

    The pilots mantra: Trim, trim, trim.....

    FS makes things easier and we can get away with a lot.

    Cheers: T

  4. #354
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    But now see, when i wad flying a cherokee, we set the trim once for climbing, and then once again for cruising and after that just used the yoke to maintain even flight.. With many planes in FS, even with a yoke more sensitive than a mama's boy, you gotta trim every three seconds or so, even if your speed remains the same.. Thats what i would like to avoid.. i dont mind the idea of trimming every few minutes, thats just realistic, but every three seconds is a bit over the top..
    As it sits, i'm trimming out the P-61 at a rate of about once every two minutes, which is plenty fine in my opinion.. Its an exceptionally enjoyable aircraft to fly.. The pitch moment may be a little low, but nothing serious.. Its just very sensitive which i would expect in a combat aircraft anyway..

  5. #355
    Pam:

    Due to the vagaries of Dialup I lost contact wit the TS server, but did download the new flight model.

    Definetly a hoot to fly and getting down to a matter of interpretation. I can tell from the contact points we are dealing with different, but not that different visual models. I noticed the comment about the video, which was fun to view, that as you stated earlier the visual components are still being worked on. Mine, the old one does have all the working animations and the textures are on the fuselage.

    Slowly the project comes together, I hope that with all the give and take that the folks will get a better understanding of the process of these things coming together, and of some of the workarounds necessary to deal with the way FS interprets the world.

    It's big, heavy and sometimes a bit of a sled! However using it's energy it can be pretty awsome. I have been flying this around in the new Solomomns Island scenery, great fun!

    We should try this in a fighter flyoff on line as part of our testing, might learn a few things!

    Best wishes: T

  6. #356
    well I'll tell you - this is a most interesting thread, very interesting with many different disciplines apparently coming into play including but not limited to, research, A&P knowledge, programming and a measure of artistic 'feel'

    I am compelled to stay tuned
    enter..the Sandman

    visit Heywood Planes - YouTube

  7. #357
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    Quote Originally Posted by fliger747 View Post
    Pam:

    Due to the vagaries of Dialup I lost contact wit the TS server, but did download the new flight model.


    It's big, heavy and sometimes a bit of a sled! However using it's energy it can be pretty awsome. I have been flying this around in the new Solomomns Island scenery, great fun!

    We should try this in a fighter flyoff on line as part of our testing, might learn a few things!

    Best wishes: T
    No worries on dialup. I understand completely.. Iddly, when i was making a good income i couldnt afford cable so had only dialup, but now that i'm on fixed income and broke, i can afford fiber optics?? ::lol:; Man has the world changed in the last ten years...

    The planes weight definately qualifies her as a sled. When i first saw that dive in the video ( the one directly from the side ) it made my heart skip. That plane diving at 350 mph is either the most impressive sight, or the scariest sight ive seen from anything. Its just sheer raw power. I love it .

    And yes, most definately we should be flying this online. Of course, everyone watching will be seeing 400 mph cessna's but, oh well. We'll get there ..

    I did a flight tonight from Bend to San fransico by way of Mt Shasta. I only used about 30% of my fuel with standard loadout, which seems about right to me.. Beautiful flight. she cruised easily at 21000.

  8. #358
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    Quote Originally Posted by heywooood View Post
    well I'll tell you - this is a most interesting thread, very interesting with many different disciplines apparently coming into play including but not limited to, research, A&P knowledge, programming and a measure of artistic 'feel'

    I am compelled to stay tuned
    There's definitely a lot to it, some almost metaphysical ( i could swear some days my uncle is thumping me on the ears. He was an instructor in the army air corps, and died ferrying p-40s to england ). We still need sound, though at the moment i'm tempted to get on my knees and beg aerosoft for use of their B-17 soundset as it fits so perfectly with this plane. The engines are massive, and with a 12 foot prop on there i can only imagine a heavy drone for sound.. ..
    Definitely stay tuned.. ..

  9. #359
    Gauge work continues...:salute:

    Attachment 16800

  10. #360
    N2:

    It is by the interior work that is going on that much will be judged! I was involved in a minor way in the testing of a soon to be released commercial product (which will be great!) and they were luck enough to have on the team a real aviaonics technician who could verify the accuracy of all of the installed instruments. Of course this one is a much older aircraft with most of the instruments long gone, even form the warbird circuit.

    Keep up the great work!

    T

  11. #361
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    Quote Originally Posted by fliger747 View Post
    N2:

    Of course this one is a much older aircraft with most of the instruments long gone, even form the warbird circuit.

    Keep up the great work!

    T
    The chinese have the one they own up for sale at 1.2 million dollars.. Saw that on a web site somewhere.. ..

    Folks, I've been watching N2056's work on the gauges and talk with him daily, and even better, i get to test the gauges out in the plane as he develops them .. The movement is smooth as silk, and even though i'm not an avionics type person, i can tell they are pretty darned accurate.. Keep watching this space.. Your gonna like what you see ..
    Pam

  12. #362
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    Ok, so tonight, while re-watching the army training film, i decided to adjust engine temps and pressures. I believe i have all those set properly now.
    I'm trying to get the sdk installed so i can install a scenery editor. i'd like to do the scenery for Le Shima which was the base where lady in the dark flew out of and one of the last strategic bases used in wwII as well as home to several fighter and bomber groups. Not many pictures of it though..
    For anyone wanting to fly out of there, the icao is rore .

  13. #363
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    ok, i know i'm losing it BUT..
    tom mentioned the idea of doing test flights online the other day, and i heartily agreed with it. Then I started researching a plane called "lady un the Dark" a P-61B from the 458th NFS. They started out in Hawaii, passed through the Mariana's, and ended up on le island ( le jima ) along with a lot of other fighter and bomber groups. Now, all this research has been because i'd really like to have a paint of Lady in the Dark for our release ( not to mention to fly myself ), and then i went one step further and started entertaining th idea of not just testing online, but forming a P-61 fighter squadron for some online fun and combat against other players ..
    Let me know what you think
    Pam

  14. #364
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    NEW FDE, V. 1.7

    I just uploaded the latest version of the FDE to the file browser. Version number is 1.7_Alpha.
    Changes made:
    adjusted trim for finer divisions
    Adjusted pitch rate control for a less sloppy action on the stick.
    dropped roll rate 3-6 feet per second.

    The end result is that the plane flies much more accurately. You can point it at a spot and it goes there. Trim is now more stable, and requires adjustments only every couple minutes or so.. roll rate does not take your head off any more..

    Please delete your existing flight model ( unless your Fliger )and replace it with these files..

    Also in the file browser are N2056's latest interior models with gauges. These models will work with all older external models and make the plane an absolute dream to fly.. Please be sure to download them as well..

    Pam

    PS:; The plane is heavy in a turn so judge your turn appropriately. It will keep going in the direction it was flying till the wings grab enough air.

  15. #365
    I imagine one will need to pay attention to fuel and payloads before flight - so as not to try to land her anywhere near her max load capacity....you might be surprised to know that a lot of virtual pilots simply load a plane for free flight in full default fuel and payload configuration - and then complain about performance and stall speeds etc...I imagine that this plane - like most medium fighter bombers - will have at least two personalities dependent on overall weight (loaded vs near empty)

    what is the optimum approach speed in the Lady - and how is the 'mush' factor near stall speed?

    what min. runway length is recommended both for max payload takeoff - and for landing rollout (hopefully with low fuel and no ordy)
    enter..the Sandman

    visit Heywood Planes - YouTube

  16. #366
    Without the externals loaded, (currently they are // out but there) he plane weighs in at less than 30,000 lbs. For takeoff right around 2000 ft ground run is needed. We were pretty close in there, but the latest version shortens the run by a couple of hundred feet, might need to adjust the flap drag a snitch.

    I think we have pretty well captured the low speed appraoch handling, slow roll rate but a lot of stability, which gives confidence. Typical approach speed was 110-100 mph depending on weight. A pretty easy plane to land, there are reasons for the demise of the high powered taildragger!

    It is not mentioned, but I presume that the published takeoff distances are using Mil power. For the widow, main disposable weights were ammunition, which might not be expended, and fuel, including drop tanks. I suppose you could airdrop the radio operator....

    Cheers: T

  17. #367
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    Quote Originally Posted by fliger747 View Post
    I suppose you could airdrop the radio operator....

    Cheers: T
    ::ROFLMAO:: there were SO many times during my army years when i wanted to do "exactly" that.. Just drop kick him right out the tail of a cargo plane..

    i also havent seen much written about takeoffs, but it is mentioned in the training film on youtube..
    Somewhere my brain is latching onto 984 feet for short takeoff, but i cant remember where i came up with that number.. probably some senility induced halucination or something.. i dont know.. The Movie mentions the WEP being used for takeoff as well as other things..

  18. #368
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    Robert was reporting that the pitch was still a little unruly and even though the training video clearly shows this planes nose bouncing up and down like a basketball at slow speed, i think i'm going to reign it in just a little more ( not very much though ) to make it a tad bit more stable in the vertical plane.. i dont want to lose the flavor, but i dont want to overwhelm everyone either.. I'm used to the plane.. I've been flying it 12 - 16 hours a day all week and so, i'm automatically compensating for things that could possibly be a real pain for others..

  19. #369
    Hunner't thou has the takeoff data, dist vrs weight for SL (p-382, graph 49). Have tested the TO dist recently and is perhaps 200-300 ft short. At 29,000 lbs should be 2,000 ft. Will try adding some LDNG Gear drag, as the airframe, wing drag and thrust seem to about spot on from speed tests at SL and altitude. I am presuming htis data is for a normal TO with two notches flaps and rotation at 85-90 knots depending on weight.

    Plane seems pretty pitch stable to me. When evaluating these planes it is important to turn all weather off as FSX has pretty well developed turbulence which masks almost everything.

    Engine insturment readings: P-37 of the POH has the proper ranges, I think we were closer before.

    Cheers: T

  20. #370
    Gauge work continues...

    Attachment 17083

  21. #371
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    let me break out the POH and see what i can see..

    I've been woirking on LeShima airbase for the last couple hours, and one thing i've nticed is that the steel plate/mesh runway has a lot more surface friction and the plane needs quite a but more runway space to take off from.. Makes me wonder if the distances reported were for asphalt or steel?? i dont honestly know..

    Still working on making corrections.. have oil temp and pressure pretty much dialed in. Fuel press. is good ( 17 pounds)
    will keep whittling it down..

  22. #372
    Robert, (N2056)

    That looks really amazing :salute: Is there a Sperry A3 autopilot beneath the main flight instruments? That black panel looks like a Sperry A3 surround, especially with that 3rd gauge (Suction?) hole.
    Craig Tatley
    No DC-3 without the DC-2

    http://www.dc2-fs.com/

  23. #373
    Hard dry surface, ie concrete etc. PSP probably did have a higher friction, unless it was wet.....

    Using the Solomons scenery, doesn't seem to be too different. Doing my takeoffs at dusk at KPWT and KBFI using ISA conditions. Count runway lights.....

    Cheers: T

  24. #374
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    let me toss LeShima at you when i get further along with it.. see if you see any difference there.. Right now, its just the runways, taxiways and roads.. its a monster of a base so theres a lot of buildings to add yet..

  25. #375
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    So here's what i got for Le island so far.. it aint fancy as i'm not a scenery designer, but hopefully, in time i'll get it to look reasonably like the real thing did in 1943.. I've only been able to find one very fuzzy reference photo of it, and interpretation leaves a lot to be desired. bear with me...

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