Barfly

Great post Otto as an experienced pilot I agree completely. There probably should be sufficient airspeed and prop wash for relatively easy control of yaw and roll at around 40mph /100kph, just an educated guess. Other forces acting on the aircraft seem appropriate, but without flight controls having some effect at relatively low speed and without any apparent aerodynamic stability developing well before takeoff speed....things are only very narrowly managed... there should be a lot more room for control surfaces to counter yaw and roll before loss of control....

Yes I understand... usually manuals are more clearly worded. The -2 or maintenance manual if their is such a thing available would probably have more specific guidance. Edit: See pg 450-451 of this manual: http://www.scribd.com/doc/34812228/P51D-Mustang-Maintenance-Manual There is a detailed description of post flight checks after wep use, and a note that clarifies 5 total hours of logged wep use requiring teardown. The linked manual is fantastic, every detail of possible field maintenance is included, with lot's of pictures.

Better worded in this revision of that page: http://i91.photobucket.com/albums/k304/Major_Sharpe/P-51WEP1.jpg

The radiators corroded and cooling passages corroded over time...causing higher that normal coolant temps and potentially more than normal restriction on power settings, and I think that's what you see here. They probably just have some bad data points from an old airshow bird that isn't in the condition of a wartime example, it isn't cooling properly. The fact that it works well enough at the power settings used by a modern demo pilot but not at higher settings is a clue. Most examples of late war fighters were relatively low time during their active use...and would not suffer from debilitating corrosion and overheat problems. I posted a link in Complex Engine Management section for a Merlin overhaul shop that discusses this issue: http://forums.eagle.ru/showthread.php?p=1966170#post1966170

You can get a pretty good feel for how effective an actual Mustang's radiator was by reviewing various max power tests at: http://www.spitfireperformance.com/mustang/mustangtest.html http://www.wwiiaircraftperformance.org/mustang/eglin-p51b-climb.jpg In the second link is a chart showing max power climbs from surface to 30,000 ft : "Climbs were made to thirty thousand feet at the standard, and at the test war emergency ratings. Climbs at seventy-five inches Hg. required about one minute less than was required when climbing at sixty seven inches Hg. All engine temperatures were normal during climb at the increased power." Time to climb for each max power setting was around 11-12 minutes, using 3000 rpm and fully opened radiators.

Associated with that are a lot of anecdotes on both sides about tired, worn out engines... No doubt to a large degree too much boost for too long. Certainly a lot of use variables come into play- some of the late war mustangs had 200+ hour overhaul intervals, mostly due to long missions at low power settings and relatively few engine start stop cycles. Some of that was also probably lessons learned and improved maintenance and operating procedures. Some MW50 equipped DBs lost cylinder pressure and performance from new engines getting run hard in relatively few hours by not complying with the factory prescribed breakin schedule (cant remember what it was... 5 - 15 hrs maybe?). Of course late war German aircraft were expected to last an average of 15 hrs given attrition, so that was kind of a moot point, and many Mustangs and their pilots just cruised around and didn't see anything, never putting undue stress on the birds. I'll keep digging for potentially useful info.

Here's a link to Merlin coolant system maintenance... some interesting details, may already be known by the developer: http://www.51-factory.com/cooling_system_maintenance.pdf Also, some notes about problems with cylinder head temperature increase with high time motors, due to "corrosion and scale in the coolant jackets inside the heads"... something you wouldn't see on a new motor: http://www.51-factory.com/documentation.htm Fascinating company... they have many cool pictures on their website of complete Merlins and parts in various conditions.

I'm sure boost limitation exceedences are not failure points in the Merlin as they are depicting in this sim. Max continuous is designated to meet TBO requirements for the engine and it's subsystems, it's not a point of failure and it is highly unlikely running at higher power is outside the automatic cooling system's parameters. Max power limitations (wep or "mil") are points past which there is an increasing, and unacceptable probability of excessive engine wear, failure of various parts or loss of power, or coolant overtemp, or some combo etc.... it's not a single point of likely or certain complete failure. IMO making limitations failure points, then degrading the effectiveness of the coolant or oil systems to meet that point of failure, is not accurate. I think under certain conditions of engine and operating environment the engine could overheat at wep, but not normally... To give an example of engine durability at high power, any use of wep in a Merlin (in US use) required an inspection for damage. 5 hours of logged wep required a complete engine teardown, even if there was no evident damage. If the engine is that durable, with repeated use of wep (even if they didn't exceed 5 min per use), I wouldn't expect lower power settings to routinely cause failure or coolant problems. There are more obvious points of material failure I think, from combat damage etc, rumaway prop loss of fluids etc, reliability issues with certain parts, but I think wear and tear from high power and engine cooling capability needs to be further considered. It may be going too far, but a Merlin overhaul shop like "51-Factory" could probably shed some light on what wears out, what fails, and why under what use. I think they have guys that have been overhauling Merlins in every conceivable condition for decades. Anyway, just a few thoughts :) This sort of thing stands out as a minor issue IMO against what is a really impressive sim effort.

So far so good with a Logitech 3d stick and Saitek rudder pedals. Any thoughts on force feedback? Does it broadcast onset of high aoa approach to stall (accelerated) in a reasonable fashion / match the visual indications? I lieu of decent force feedback, it would be nice to have adjustable buffet sounds... they may currently be at a realistic volume, but absent peripheral vision and physical feedback, louder buffet would be a reasonable substitute IMO for PC sim purposes.

Thanks for the welcome, and input guys. I've modified the curves a bit and get a much better result now... still not quite there yet, gonna continue to fiddle with it. I assume a linear response curve in the Axis Tune Panel is a straight, not curved line?

I agree completely with MikeWilliams perspective and a few others here.... arguments about the fidelity of the sim physics aside, the DCS mustang would be more flyable and much more realistic with a desktop joystick oriented input curve as standard... maybe give a control option for that fraction of users that want a full length control stick... "Realistic angle of deflection" or whatever you want to call it. Have as standard a blended input for desktop joysticks, with perhaps a "finger-tip" level of control for the first 1/2 inch of top stick travel or so, blended into full control throw input at full angle of joystick deflection. I think that scheme works well for some of the better aircraft in FSX, and perhaps other sims, and would work well here. I know that's not how the sim is coded, and apparently the input response curves don't seem to allow that range of adjustment... at least they don't in my limited experience with them. As a sim, the DCS Mustang is certainly exceptional, with it's strong points being that it's a comprehensive systems, weapons, and combat environment simulation, with a very detailed FM engine, but the flight feel in large part just isn't there in my case. Some of that comes from an unwillingness to put extra time into adapting to the chosen control scheme, some is lack of suspension of disbelief because IMO the complex and varied parts of the FM don't mesh well enough to give a thoroughly believable flight experience throughout the envelope. Just my opinion. As for the feedback from the Mustang pilots, it's easier for them to replicate the experience of flying an aircraft they know well in a simulator that is a reasonable facsimile of the real thing, but that's not necessarily the level of detail necessary to 'inform' a PC simmer of the exact characteristics of the real thing... if that makes any sense. There was certainly a lack of detail in the pilot's feedback that is telling... particularly with respect to control response and axis stability. Those are things you can work around to get a good result in a sim if you are a decent pilot, but not necessarily adequate for a sim to stand on it's own as representative to someone not familiar with the type. If that makes any sense...