SOH P-61 project

[jankees]

small update from this side of the pond: after restarting, I now have 4 viewpoints, including the VC.
Even on one engine, it handles beautifully:


but on two, it will go anywhere:

(OK, I stalled in the end..but recovery was easy)

[warchild]

Those are gorgeous Jan.. simply gorgeous Thank You ..

[N2056]

To expand a bit more on Pam's comment about the left MP needle: I'm using seperate throttles, and I'm not getting this with any other multi so I believe it's not the hardware. The right needle is precise, goes where you put it. The left, however, tends to wander of its own accord before finally settling roughly where I want it. In some cases, it is an extreme movement, covering almost half the gauge when I'm only making a fine adjustment. Other times, if I move the throttle the needle heads off in the wrong direction before correcting itself.

I spent some time playing with this sitting on the ground, and (of course) here they are both acting as expected. I am assuming you are looking at the VC gauges? The animation codes are the same for each needle except for the driving parameter, so I doubt it's a model issue. Can you duplicate this on the 2d panel? If yes that tells me it is not my code (which is good for me to know).

[N2056]

I have added some stuff to the lower panel

Attachment 19705

[stansdds]

It's looking good!

[warchild]

I've started working with the ground effects in this version in an attempt to model the correct floatiness of the wing. In a related effort, I was asked if the plane could be made to keep its front wheel off the ground for a rime after landing. At this moment, it cant, and with the placement of the wheels, the downward pitch from the flaps, and the overall amount of plane in front of the cg i'm not certain that air braking is possible with this plane at all.. I would appreciate some insight here..

Roll rate has been re-corrected back to 87 degrees per second. Yes, i know that means that it cant bank with the best of them, but considering the size of the plane its better than anything of equal size..

I've increased the wheel drag causing the plane to use more than a thousand feet for takeoff.. its back to where it should be, and we havent lost anything of the actual lift and takeoff characteristics that are otherwise known and noted..

My challenge now is to polish the deges of the flight model, without disturbing or losing anything that Fliger and i originally developed. its a fun ride. ...

ALSo..

Robert uploaded the latest panel and gauge update. there is now a gauge for the cowl flaps and a new exterior model with changes in the cowl flaps that reflect the real ones better. Its looking absolutely gorgeous.. the file name is 23sep.zip.. You'll want to download it soon..
Pam

[delta558]

Did you have to, Pam? I was really getting into the Stearman but now I'm just going to have to go and get the new bits!

[warchild]

Did you have to, Pam? I was really getting into the Stearman but now I'm just going to have to go and get the new bits!

:::LOL:: Enjoy Paul .. I made amistake on my quoted roll rate.. Its supposed to be 77degreesper second, not 87.. Big difference there, especially when added to the latency for the wing to actually start dropping during a bank.

I'm slowly adjusting the brake pressure.. she now stops in 1370 feet approximately, from a 100 mph landing speed.. but that will be in the next fde..

PS.. yeahhh, that Stearmans a cutie.. I need to get you and Dan together.

[fliger747]

77 deg/sec, hope you are talking about another plane.....

Slowly all the bits and pieces coming together.


Cheers: T

[warchild]

Wellll, its difficult.. I just did a stop watch test with this video http://www.youtube.com/watch?v=Lo-f2x8T7d8&feature=fvw. She's quick.. very quick for something that size.. 77 - 85 degrees per second..

And yeahhh,, the bits and pieces are definitely beginning to fall into place

[N2056]

More panel work...

Attachment 19791

[warchild]

77 deg/sec, hope you are talking about another plane.....

Slowly all the bits and pieces coming together.


Cheers: T

I redid he timng after robert watched it and made observations.. One of them was that the roll looked casual.. it wasnt a hard toll.. another is that the pilot never took the pane past 90 dgrees.. Guess i need new glasses.. Using roberts observations and timing the roll with the seconds counter at the bottom of the film, i was able to time the plane doing 90 degrees in two seconds.. If that was a casual roll, then a hard roll would pit the roll rate somewhat higher.. Perhaps not 77 degrees but certainly 60 degrees..

[txnetcop]

You are building a BEAST...and the panel work is outstanding!!!! WAY TO ROCK this build! What a great TEAM!

[Dain Arns]

You are building a BEAST...and the panel work is outstanding!!!! WAY TO ROCK this build! What a great TEAM!

Hear hear! What a beautiful work of art you folks are making!

[delta558]

Can you duplicate this on the 2d panel?

Yup - so it's not a gauge problem.

[fliger747]

Never ever use a training film to time anything. You have no idea if the rate of play is correct to the original timing. Firstly the camera used some unknown frame rate, it was palayed at some unknown rates and then changed to a video introducing some additional variables and then again edited at least once. You don't even know if for war time purposes the play rate was altered. You have no idea what the load configuration was per fuel distribution, or even if it was a production standard aircraft.

We have published data, best to stay with the published data. Comparing to other published data for well known aircraft we should fitr into the pecking order of roll rates. 50 deg/sec max isn't too shabby for a plane this size. Actually pretty good. Even the really good rollers such as the F4U did about 90 deg/sec. Pilot comments note that the roll rate was not good by fighter standards.

The roll rate WAS right previously.

As to nose wheel. ill take a look at this. I did a FDE for a F86 a couple of years ago and was able to accomplish this. However the danger with a plane that has a variable longitudinal loading is that it may fall on its AZzz. The wheels cannot be moved from their actual locations as it causes a verticle displacement of the wheel at any but a level attitude. Usually this shows as the wheel submerging on takeoff or landing while at a positive body angle.

So you have to move the CG... which changes everything else..... All fixable, but a lot of "fixing".

Cheers: T

[warchild]

the reason i had to correct the roll rate was because every time we changed the something else in the fde it effected the roll rate. every time i tweak an entry in here whether its the center of lift, prop efficiency, elevator and rudder profiles, doesnt matter, i have to go back through and reset lift drag and roll back to their original behaviors that you and i agreed upon. For example, without touching the roll rate in any way whatsoever, at the point i knocked it back down, last night, it was rolling at over 90 degrees per second.
As for the movie? I used to manage theaters and learned about being a projectionist at the ripe old age of 12. I know about the different frame rates used, and your right, at the beginning of the war, they still hadnt standardized on the 24 fps rate. Some still used the slower 18 FPS, but that caused flikering that was was noticeable. So By the time Bob Hope and Bing Crosby started doing their "Road" shows, they had standardized across the board. which was about 1943.

With the air braking. I believe Robert was referring to the behaviour most commonly seen when a jet lands. The front wheel stays off the ground for a ways. In the vulcan they used this to their advantage as keeping the nose wheel off the ground produces an extreme amount of drag below the wing and slows the plane down. They called it air braking. Our plane doesnt do that.. and even if we moved the CG it couldnt, unless we can move the CG behind the main gear, which we cant, and even if we could i wouldnt, because you and i have worked too damned hard to get her as close as it is to change it now..

Remember, i had to correct wheel drag as well, because in order to get it to meet another published and documented ability ( it would fly itself off the ground ) i had to adjust several tables, and by the time i achieved that, the plane was taking off in 900 feet and wheel drag had to be increased once more. BUT, clean stall speed is now 95 mph, she can take off between 70 and 80 mph, she stops in 1300 feet from a 110 mph landing, which gives her excellent short field characteristics.

I regret not having access to the same documentation you have. I cant afford it. I'll try and get a copy on the third when i get my social security. At least maybe then we can both be on the same page, literally.

Regarding it being a poor fighter.. In order to get one divisions general to even think about using the P-61, John Myers had to fly a mock dogfight against a P-38. Naturally, having also been the test pilot on the P-38 he knew its weaknesses and used them, but he did win.. So was the plane a poor plane, or were the pilots poor pilots?? 95% of all the planes shot down during the war were shot down by 5% of the pilots. Thats a quote directly from Chuck Yaeger and backed up by Bob Hoover. It leaves a lot to wonder about the quality of the majority of pilots, and their reports.

[warchild]

rhis might answer a few questions better than i can with words..
http://www.youtube.com/watch?v=DRaOFjHMdok

[fliger747]

With enough trials and tribulations it will be a great plane, in many different ways.

Below is the roll data that I had posted a long time ago in this thread. I know well about the change one thing and everything else changes scenario.

I did go back and fly the F86 last night, and it is possible to hold the nose wheel off, for a while. Generally one has to adjust the position of the CG aft near the rotation limne of the main gear so very little "tail down force" is needed. Another somewhat weak area of the FS engine. We should endeavor to be able to use the lift the nose and let it fly off technique.

I don't think aerodynamic braking was used much during the war for prop aircraft as an idling prop has a drag coefficent almost as high as a parachute canopy of the same diameter. It was a feature of some of the early cold war jet era. We had an Airforce guy that though he was still a hot fighter pilot and used aerodynamic braking with the 747-200, and drug the tail and got fired. Brakes are better today and the thought is to get the weight on the tires to prevent skidding, brake locking etc. Hence the use of ground spoilers.

I don't know, but if a clip was filmed at 18 FPS and played at 24 FPS, the flickering would go away? That might coincide better with the published data.

Someone made a P-61 for CFS2 and I remember doing some dog fights with it with sucess. It rewarded good use of energy techniques and good marksmanship. A couple of years ago I reworked the FDE of an Ito one for FS9. This one is getting about another order of magnitude of flight engineering devoted to it!

If you have any data that you need that I might have I will certainly post it!

Cheers: Tom

[N2056]

To clarify what I was talking to Pam about...my main issue has to do with the nose gear slamming down upon landing. It seems to to me that you ought to be able to let the nose down a little slower than we have right now.

[Sundog]

For a ground based aircraft with tricycle landing gear, the tip back angle is usually around 15 degrees, maybe slightly more. This means when the aircraft is parked level on the ground, draw a line angled 15 degrees ahead of the vertical line running through the main landing gear strut, assuming it's vertical, pivoted around the point where the main gear tire contacts the ground. Of course it would be on this line somewhere in the fuselage, I would just assume it would be on the longitudinal axis with a lack of references. Of course, on the P-61, being a naturally stable aircraft, it's going to be ahead of the AC as well, which would be at approximately 25% back from the wing LE at the 1/4 chord line. Just for reference. Do with these numbers what you will.

Also for reference, on Navy aircraft this angle is around 25 degrees or more, since the Navy parks their aircraft with the tails hanging over the side of the ship, they don't want them tipping and falling off before they're tied down in rolling seas. This is also why navy aircraft can't aerobrake while landing on runways like air force aircraft; i.e., they can't hold the nose up as long as ground based aircraft can. This is one of the reasons why it's always easier to make a naval aircraft land based than it is to make a land based aircraft work on a carrier. It was also one of the problems with the F-111B, which is why the production version would have had it's main landing gear moved back, among other fixes.

[N2056]

One of the things I was struck by when I first got started on this was how cluttered up the cockpit is! Here are some new bits that help illustrate what I mean...Track IR folks are gonna have fun in this thing!

Attachment 19957 Attachment 19956

[PRB]

That cockpit is looking tremendously awesome. As a P-61 nut from way back, I am getting excited about this project. Bravo Zulu to all involved. Between Tom and Pam, I'm sure the Fm will be great as well.

[N2056]

Paul, thanks for the comments on the cockpit. Based on your comment about your interest in the real plane over the years I can't help but wonder if you might be able to help with any research type questions I endlessly come up with while modeling. It doesn't take me long to make a given part, but lately it has taken hours to figure out what that given part should look like!

[PRB]

... We had an Airforce guy that though he was still a hot fighter pilot and used aerodynamic braking with the 747-200, and drug the tail and got fired ...

Dang!