Hurricane engine torque

[Viper2000]

Originally Posted by Peril

Your a funny man Viper, you think like an opposing team not wanting improvements.

Only if your definition of "improvement" is "change for the sake of change".

Originally Posted by Peril

For info it was a Hurricane II with a Merlin XX, Rotol constant Speed prop, document is 'Measurements of the Flying Qualities of a Hawker Hurricane, by Neilsen and phillips. You could have this test data on your HD already I suppose??

Nope. If I had the data I wouldn't have been asking about it.

Originally Posted by Peril

But if you don't and want to improve the sim, 'please supply more data' would be a good start. I tested the Hurricane in game marked as a Rotol prop Hurricane, not sure if that is a definitive match, it's hard to tell based on that description.

They are different aeroplanes with very different engines (Merlin XX is single stage 2 speed with a redesigned supercharger), a different wings (Hurricane II has a 12 gun/4 cannon metal wing vs the 8 gun metal or wooden wing of the Hurricane I) and a different fuselage length (Merlin XX is longer so the Hurricane II has a longer fuselage).

Obviously these are quite substantial design changes, and for this reason it isn't obvious that the Hurricane II would have the same trim behaviour as the Hurricane I.

I'm all in favour of making the sim as good as it can be, but I don't think that there's much to be said for deliberately asking for trim behaviour to be based upon that of a substantially different, albeit related, aeroplane.

Given a comprehensive "changelog" between the Mark I and Mark II aeroplanes (which I don't have, before you ask; I know the broad brush strokes, but I can't immediately bring to mind the sort of specific details required to get trim behaviour right) we could potentially try to reverse engineer Mark I data from the Mark II data that you've found.

Originally Posted by Peril

So you are aware, I spent the last 6 years building and researching FM for another sim focused on realism, so I have some experience and data to call upon and know what is required. I too didn't modify my FMs without good data but I'm not one to ignore what is logical either. If it is of interest we had to apply on average 0.2 deg of wing twist to obtain an outcome that match reality re roll trims. Sims are great representations but unfortunately they are rarely perfect in result because of using the simplified code they have to use due to the limits of home computing. Before you go off all negative, think about what we have proved here and work backwards from there, I always found the answer could be somewhere in the middle.

Feel free to use any alt, power and the glide test data to confirm, I think you'll find it likely has a problem

That would confirm some changes are needed, some of us are here to 'help' where we can...the only agenda I have is FM realism.

Building sim models is all about matching.

The problem is that there are lots of variables to consider, and depending upon the underlying flight model of the simulator itself it may or may not be possible to accurately match all of the available test data.

For example, you can't make an accurate WWII fighter in X-Plane without recourse to plugins because X-Plane just can't model a WWII engine properly; you can't get realistic supercharger behaviour because it only allows for turbonormalising, and you can't get a satisfactory model of exhaust thrust either. Which means that most people end up with inaccurate airframe drag and/or an inaccurate propeller model in an attempt to match the headline top speed of the aircraft. This then results in incorrect cruise and glide behaviour. Essentially, the tighter you squeeze any one parameter, the more likely the others are to slip through your fingers.

The most dramatic instance of this I ever encountered was a Corsair which flew nicely and looked pretty but was almost impossible to land. What happened was that the guy who'd made the model didn't realise that the R-2800 has a 0.5:1 reduction gear. So he had a very supersonic prop with awful performance, and this had forced him to dramatically reduce the airframe drag in order to match the stated top speed; it was therefore basically impossible to get the thing to descend for landing!

Until such time as the SDK is released and documented, and the major engine bugs are squashed, it's pretty difficult to work out the specifics of the model used in CoD, and therefore it's hard to form a sensible opinion as to how good the models are given whatever the limitations of the overall FM are.