SOH P-61 project

[MudMarine]

On youtube there is a P-61 pilot training film. In the film they demonstrate a low speed, 90mph short field take off. I imagine it would all depend on load out and fuel weight, etc

[warchild]

Thanks Marine..
That gives me the third part of an equation to isolate the root of a different problem, but will solve several issues..

[fliger747]

You could takeoff at 95 mph, depending greatly on weight, however such would not be a standard procedure. Operationally real situations made this less desireable than in FS, our engines aren't as prone to failure or damage during the acceleration phase from detonation and overheat. I had a discussion the other day with one of my DC6 driver friends on the subject and how they seek to maximize forward speed for cooling and minimum drag before the first power reduction.

With a two engine aircraft, minimum control speed is an issue. It was operationally desireable to minimize the dwell in the area between takeoff speed and minimum control speed.

Figure 47A (P-32) in the POH gives the stalling speed with various weights and flap settings.

As to the R2800 25 engines, only five were ever built, apparently used in some P-61 aircraft on a trial basis. The moral, Wiki is a secondary/tertiary source and not always correct.


Cheers: T

[warchild]

yeahhh, then i've been out of the ballpark. However if you were able to decrease the ift on the tail plane and move the cg backwards then perhps we have a hope ..

[N2056]

Here's my first crack at the armored glass, along with the tubing that the gun sight will be attached to :salute:

Attachment 15802

[Cag40Navy]

Lookin real good!

[warchild]

Thats frikkin sweet looking glass great job.. love the contrast it adds without reducing the brightness or color..

[jankees]

excellent!

[warchild]

ok.. ots 4M.. gotta admit i spent most of the night flying Miltons commanders, and painting one of them.. I'd forgotten just how much i loved those things.. but it gave me time to think, and thats what was needed..
Fliger has been doing an excellent job with the flight model and thats been a godsend as my own time is still being driven by commitments not only to other developers, but to the group of people i'm in charge of at the peer center.. Thanks Fliger .

Before we get too far into it, theres an issue Fliger brought up that needs to be addressed and discussed.. and it includes all the non paint personnel..

the absolute top speed onf this beast is reported typically as 351 MPH.. We can only assume that that top speed is available only wuth WEP active, and therein lay the crux of the matter..

If WEP is engaged for more tan 30 seconds the engine starts piling on the damage however WEP is automatically engaged at 95% throttle. now, we have two ways we can deal with this, three if we get fancy.. The first way, is to shrug it off and leave everything as is ( WEP is constantly available 100% of the time ). The second option is, to set maximum throttle for 94% and develope a gauge for activating WEP. The third option is to note to the end users not to take the throttle past 94%.

lets talk this out and see what we come up with..

bed time..
Pam

[PRB]

When dcc made his P-38s for CFS2 and FS9, he delt with this WEP issue in a cool way. He had a switch on the panel that activated WEP. You had it for 30 seconds, total accumulated time. If you exceeded that, the engines lost huge amounts of power, essentially failed. I don't know if the P-38's WEP was actually engaged by the use of a switch, maybe that was just dcc's way of dealing with this. His P-38s can be flown with the throttle lever's maxed out as long as you have gas, you just don't get WEP power without hitting the switch. Another possibility.

Just finished reading The Long Way Home, a book about the Boeing B-314 Clipper that was stranded in New Zealand at the start of the Pacific War and had to get back to the States "the long way" around. When they took off from Leopoldsville, Africa, they kept the engines at max power for a couple of minutes, and had the CHT in the red for a scary long time. Book says THOU SHALL NOT STAY IN MAX POWER FOR MORE THAN 90 SECONDS." But they had too, get off the Congo River, see? And while, they were really worried the engines would fail, they didn't... The point is, a hard 30 second timer and then "poof" (as Fliger says) the engines are gone, may be a bit annoying, and mayhap a tad unrealistic. But, I understand you have to deal with this somehow... I would be ok with a timer of some kind, maybe twice the published time limit?

[fliger747]

On the DC2 project we had a damage scenario linked to the CHT, and a timer. The problem with CHT in FS is that it is almost totally linked to RPM, back to some gray beginings as a gen av sim with fixed pitch props.

Actually the R2800 liked being at WEP with water meth better than dry at TO (Mil) power. Many factors determined how boost would affect the engine, a prime one being air temperature. Cool temps were much better, hot ones much less so.

Ther is a really good chart in Hundred Thou which gives the max speeds vrs altitudes for both mil and WEP power, so I think we can work this out OK.

T

[warchild]

Sooo, "this" is the engine behind all the legends> The Engine that can take anything except a bad mechanic. The engine that will run even with a missing cylinder head. ::Chuckles:; yeah, I know, its a little romantic for this early in the morning but i just woke up..
Ok Fliger. You got my trust on this..
The problem with a switch as Iris found out with afterburners is that it adds in a second afterburner/wep on top of FSX.. i was thinking about that last night, but if the engine can take that kind of pounding and still keep going then perhaps its not an issue at all???

[fliger747]

In the large engines, really any aircraft engine, heat is the primary enemy and the primary issue is getting rid of it. The more compact and powerful the engine (desireable from a performance aspect) the bigger a problem. Heat in an aircooled engine is gotten rid of in three ways, aircooling of the cylinders through fins and airflow, heat carried away by lube oil, and by the mass flow through the cylinders and carried out by the exhaust. In the cylinder heat is generated by comprssion of the mixture, by combustion, and carried out by the expansion and removal. There is the mass of the air and of the fuel. Heating and vaporising the fuel takes quite a bit of heat away, and richer mixtures are (1) harder to ignite (2) provide more mass and fuel to evaporate and hence inhibit detonation, which is premature ignition of the mixture well before top dead center, causing a reduction in power and very severe stress on the pistons, cylinders and crank assy.

Water injection (with meth for antifreeze) increased the mass flow through the cylinder and took a very large amount of heat away due to it's heat of vaporization and alowed a better fuel/air mixture, closer to best power without risking premature detonation. So a better mixture could be used, and a higher MP. When working a very good system and often the engine liked this better than Mil Power. The rate of water consumption and it's weight made this impractical for long duration application! Some aircraft did have fairly good sized tanks, but this only permitted several applications of the water injection, such as for takeoff, and perhaps a combat application or two of short duration.

These engines were not expected to have long lives such as the present day commercial applications such as the CB16 in the DC6 which do benefit from TLC.

Had the pleasure of seeing both a C-46 and DC6 startup and fly in Anchorage before blasting off yesterday evening.

Cheers: T

[Milton Shupe]

Ah Tom, I love to read your explanations and experiences. Great stuff!

[N2056]

This evening I worked on the pilot's gunsight...

Attachment 15907

[PRB]

Looking great! I know this is going to be a blast to fly!

[Cag40Navy]

Looks really good! Sorry i was not on tonight Robert.

[warchild]

I just uploaded a new fligyht model. Once fliger is able to get me his latest updates, i'll marry them withy this one. till then, i'll keep improving on it as i can..
The file version is Alpha 1.6, and theres a ton of improvements.. roll rate, pitch rate, trim moment etc.. Take off with no adjustments in load is 110 mph,, dont retract the flaps till you hit 146 mph ( first step ) and 175 mph ( full retract ) or you'll sink like a rock..
download it and replace the files you now have with it. its in the FDE folder of the file browser..
Enjoy.. Pam

[Ferry_vO]

Good to see this project being continued! For a while I thought it was as cursed as the Fokker G.1, of which plenty were started but none ever finished since Fs2000....

The Fs9 early build I have had a lot of promise with a solid flight model and a very smooth exterior model!

[warchild]

this one Is getting lots of love .. I wont let it be cursed. Whatever it takes, we'll get it done. i hadnt had a chance to fly the fs9 version but this one is getting whole new everything, including a flight model sculpted by fliger, myself and my team at JFTC. i wont say we're experts or know it alls, but we aint too shabby .. Stay tuned and i promise you a plane you will enjoy for a very long time to come ..
Pam

[stansdds]

I'm happy to see the P-61 FSX project moving along so well.

The FS9/FSX F7F project seems to have stalled, no one has stepped up to make the VC.

[padburgess]

Hi Pam

Please excuse the presumption, but I have been following the discussion on dealing with the problem of WEP on this project. By the way I am seriously looking forward to this aircraft coming out.
My 2 cents worth. Why not leave the WEP at 94% throttle, and with the 90 second time limit (these are generally set by both the heat problem in the engine and the quantity of water meths or what ever other agent was used) and then at the end of the time limit apply a bit of random logic. Look at other parameters (engine age, ambiant temp, altitude etc and use a random generator to either blow the sucker or let her run. This would cover real world scenarios nicely and add a bit of spice to the flight. You just wouldn't know if you were going to have two, one or none turning. Sorry if this sounds simplistic. I have no idea of the coding involved, but I'm sure that you all could breeze it.
Getting back to my enthusiasm for this aircraft. I am a great fan of WWII twins. Any of them. So if you feel the urge to carry on after this one and do say a Ju88, Do217, Fw189, B25, B26, A26, Ki46 Dinah, Ki45 Toryu or any other it will bring me great pleasure.

Cheers
Paul

[txnetcop]

Sorry I have been away from this...the progress you have made is incredible! YOU GUYS ROCK! Fliger is right about the R2800s they loved the WEP effect. This engine was damn near bullet proof, but not under all conditions. They could behave very badly when mishandled. The engine powered not only WWII aircraft. It was made all the way up into 1960 for Convair and Douglas Aircraft. Today these engines are still sought for restoration purposes.
Ted

[warchild]

Hiya Ted, Welcome back
Thanks for the input. With all the input on it, theres a lot to consider and think about.. i trust what you and Fliger said about the engine liking WEP, and air, and intercoolers, and anything that helped keep the heat down. They're 18 cylinder monsters. Pure iron. Its not the coolest running material in the world, so anything that would cool them down was much loved by them..
I know the p-61 had water meth tanks on thm, but what i dont know is how much they carried. Still, I'm inclined to use reality here. You have so much water/meth to use, you can use it when you need it, but when its gone, its gone.. At that point, if we dont throttle back below 95% the engine overheats and seizes up.. How long to give it before it seizes up is a question that will have to be researched. That plane in africa mentioned earlier could have been sitting with engines running for up to 5 minutes ( the length of time a B-17 has before it begins to have troubles ) But sitting on a tarmac is not running at full power. Taking into account the number of hours on the engine as Paul suggested, may at this point be a good idea. The newer the engine, the longer its ability to handle extremes.. and maybe we can create a curve based on that which can be used to seize the engines.. Hope i'm making sense.. its 4:30Am and pretty far past my bedtime so i know i'm rambling a bit here.. however, what im thinking would give us a more realistic result than just setting a 90 second time limit on it, and add a bit of randomness to the scenario..

I was going to wait to ask for this but i can see that waiting would be foolish as theres so much to do. At this time, N2056 is building the VC and gunnery position, but theres so much to be modeled in there that to ask any more of him would be sadistic at best.. That means, we dont have anyone coding for us.. We need a coder, a gauge guru, and with all the gauges in this thing, we need one soon. We need SOH's help and skill there..
We're also going to be needing an effects guru. The P-61 carried four 20mmk canon and four 50cal canon, and it was easily the most devestating fighter of world war two. The combined fire power on this plane when unleased may very well qualify it as americas first gunship. The original Dragon. I'd like someone who could reate the effects of that armament with tracers visible for some time.

I was asked recently how soon the plane could be done. i didnt have an answer, but there's a round the world race coming next febuary and mid december is the date for entrance. Providing the rules allow, this could be a good plane for that race. it may not be as fast as others, but its range would even out the difference as it wouldnt have to refuel as often.. I wouldnt mind seeing her in that race to be honest, and with a three man crew, non stop is a possibility.
Anywayy, i'm rambling and i'm sorry, but please folks, if you can code and enjoy it, please let us know.. we need your help..
Thanks
Pam

[N2056]

Pam, keep in mind that I am doing 3d gauges...unless you think there is really a need for a 2d panel the gauges are already part of my work package :salute: