Mu-2 roll trim

[av8r]

I see there were some talks in support forum regarding the roll tendency of Mu-2 on take-off. It seems that even the author of the tutorial thinks it's too much pronounced (MU2 Tutorial, pg 15) :

"There has been much discussion during x-scenery's MU-2 development about the roll torque and whether a real MU-2 exhibits behavior to the same degree. I have piloted a real MU-2 on takeoff many times and the effect is not perceived to be as pronounced in reality but it is certainly there. If you release the yoke during climbout in a real MU-2 with neutral roll trim, it will most assuredly roll to the right."

As someone who never piloted real MU2 I can only speculate about the degree of roll/torque on that particular aircraft, but I must say that it "feels" wrong or better - too pronounced. Since we are talking counter rotating props, high-wing a/c, RL experience is usually that of less pronounced tendency to roll.

Now, I must say that I don't know a single thing about process of making a/c for X-Plane, never did it, probably never would do it. But I have some friends who are RC enthusiasts. The moment I described to them roll problem with MU2 on X-Plane, they told me 2 things:

a) - engine sidethrust/dowbnthrust parameter

- rule of "enlarge stabilizer and fin areas by 10%" that they apply when building a scale model. The 10% increase in total area is visually undetectable, and, apparently, works miracles for flight behaviour.

Don't know if this helps, just my 2 cents.

[tkyler]

Thanks for you 2 cents av8r, but just so you know...I won't change a thing.  If you have the correct version of x-plane (9.31 or later) and are using the latest version of the MU-2 (version 1.1.1...though I don't think I labeled it well in the download...time to fix this!)  anyhow, if you're using those and the roll is "TOO" pronounced, then you're not flying it right.  Also, you mention "counter rotating" props..and the MU-2 does not have these...they rotate in the same direction.  

This x-plane version flies almost exactly like the real thing.  NOW in  the documentation, I recommend a bit of left trim on takeoff.  Now we never used left trim before takeoff in the real MU-2, but if you watch a few cockpit videos on youtube of real MU2 takeoffs.

http://www.youtube.com/user/mtnairpilot#p/a/u/0/wCxOx30rdow

..you'll note that we just yank the yoke to the left quite a bit after we get airborne, THEN we adjust the roll trim as needed after dealing with gear, flaps and bleed air.  Actually, your hand moves between all four controls until the plane is stablized..

rotate...bit of left yoke  input,  gear up, flaps up one detent, adjust roll trim, bleed air from off to left, flaps up another notch, adjust roll trim...speed up a bit, bleed air to both....adjust roll trim, stablize at climb speed, adjust roll trim...and that's how it goes.

Now as one who HAS flown the MU-2 and used computer hardware, I'll be the first to tell you than a yoke at home doesn't feel like a yoke in the MU-2.  No big deal to hold the yoke to the left while really flying..you just did what was natural, but on a home hardware system, with the spring loaded hardware, it just feels wrong I agree... holding the yoke to the left.  Sooooo, I recommended using roll trim before takeoff to "ease the pain" of everybody who has never really flown an MU-2.

Also, notice I said "perceived" in my comment, not "TOO", please don't put words in my mouth, that is a "pet peeve" of mine....that means our brains interpret the phenomenon different, even if the phenomenon is the same...and personally, I think the x-plane model is pretty darn close to the real thing.  The answer to the roll issue is not changing the flight model to make it easier for you to fly..the answer is changing your knowledge of flying it (and the correct versions) and learn to fly it correctly.

[av8r]

Thanks for advice but I already trim one notch to the left *before* t/o run (as per included manual) so taking-off is realy not of an issue here in a sense that I do not need a few extra hands to have fully coordinated take-off. Also, I realy wasn't asking for you to make the model easier to fly, which would be, actually, quite pointless in seriuos sim like x-plane, so, please, do not put the words in my mouth. :-)

Leaving that aside, I must say that for some reason I was sure that we're talking counter-rotating props. I stand corrected and in my defence all I can say is: do not read simultaneously two or more a/c manuals! Video is great, but "over the (pilot) shoulder" shot would be even better.

Thanks for the answer.

[tkyler]

no worries av8r..sorry if I came off a bit terse.  I tend to get a bit defensive when I think folks who've never flown an MU-2 are telling me how the MU-2 should fly.  Certainly you didn't  go that far, but others have enough to make me twitchy.  I do thank you for your thoughts and input as I'll be considering all things for future updates.

[Jacoba]

I think the real problem with the MU-2 is not its fault or the fault of its designers. It has more to do with many, many years of people being told by both other payware developers and freeware developers that a certain flight model is as real as the real thing, or as real as it gets, or was tested and verified by real pilots, etc...

This creates a certain "belief" and in this case a misconception within the ranks of users, so when they finally come along and discover one that behaves with real characteristics it floors them.

In all my years of simming and all my years of flying real planes I have never encountered a plane, pay or freeware that flies or feels like the real thing.

You occasionally come across one's that "behave" like their real world counterparts.

But with the MU-2, its a very unique plane in real life, requiring lots of time and training to master.

From what I've seen, the XS MU-2 is about as close to the actual flight characteristics as one can get. This comes from both the talent of the planes designers as well as the unique abilities that X-Plane gives the plane designers to work with.

No sim will ever be able to fully create the experience and feel of the real plane, but I think with X-Plane we are getting closer to one that will behave like the real one.

 

[riccardo74]

I purchased MU2 in may 2010. Since that date any other update?

I haven't really piloted a real MU2. But I noted in x-plane this aircraft has a BIG tendency to bank to the right and I make a great effort to keep it leveled. Is so difficult as in real one? or maybe I need an update it to fix this problem?

Many thanks,

Riccardo

[Cameron]

No, no new update released at this time.

Yes, the right roll is a true characteristic.

[Dozer]

The current version is (I think) v1.1.1, but v1.5 is very close to completion according to Tom's posts in the MU-2 Update Thread.

The manual says you need to add in a healthy dose of right-roll trim before takeoff - that should help. There was a video Tom posted years ago, which I can't find anymore, showing a Mu-2 pilot taking off. The camera was attached to the copilot's seat, fixed to show the pilot, control column and instrument panel. As the aircraft rotated the pilot applied a lot of right-hand aileron - about 45°.

Control-column forces are different in an aircraft than they are with a spring-loaded desktop joystick or yoke. When I'm driving my car, I don't really think consciously about how far I had to move the accelerator pedal or the steering wheel - I just move the controls automatically until the vehicle is doing what I want. It's probably the same for a MU-2 pilot - you see the aircraft beginning to roll to the left, you don't want it to roll to the left, you just automatically catch it with the yoke and maybe don't even realise how far you had to move the controls to do so.

(I wonder if the MU-2's roll spoilers feel different to conventional ailerons?)

edit: Now I feel silly. Your question and my answer were exactly what was asked and answered in this thread, nearly two and a half years ago. I could have saved myself some time by just quoting Tom's post above!

You are using roll trim, aren't you?

Edited February 18, 2012 by Dozer

[riccardo74]

Many thanks Dozer. I use roll trim, but hand pilot this a/c is very difficult. I can't keep a safely straight-in flight. I must activate autopilot for a level flight.

What are 1.5 feature update? any rumors?

[Dozer]

Many thanks Dozer. I use roll trim, but hand pilot this a/c is very difficult. I can't keep a safely straight-in flight. I must activate autopilot for a level flight.

What are 1.5 feature update? any rumors?

According to Tom, it's very very very close. Just documentation to complete and then it will be shipped. That is what was said in the MU-2 update thread.

[andyw248]

...but hand pilot this a/c is very difficult. I can't keep a safely straight-in flight...

That sounds exactly like me before starting working on my instrument rating. Now, about 35 hours into it, I'm amazed how I can fly for an hour and a half without ever getting off the assigned altitude by more than 50ft and the assigned heading by more than 5 degrees. To me it seems it's just practice...

...but in a sim it also depends on the equipment. Do you use yoke and rudders? Makes a huge difference to using the keyboard, is expensive, but also yields huge rewards.