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 Post subject: Re: Well the MU2 is a nice ride, especially the Crossno expr
PostPosted: 05 Jul 2018, 20:29 
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The short bodies in particular are short relative to the amount of power, which means the rudder plays an outsized role in order to exert enough force to balance the torque around the vertical axis. That's why they build planes with trim. :shrug:

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 Post subject: Re: Well the MU2 is a nice ride, especially the Crossno expr
PostPosted: 06 Jul 2018, 01:09 
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Username Protected wrote:
One question I do have regarding the MU2 experience is in regards to rudder trim. It required quite a bit of adjustments with airspeed changes. Curious why that’s so and if it’s a common characteristic to the type.

The MU2 requires rudder trim tweaks if you change power setting. The engine torque can vary from about 1750 ft lbs per engine at full power to perhaps -250 ft lbs per engine at flight idle, a difference of 2000 ft lbs over the throttle range, and there's two engines doing that. So you can't make significant power changes without countering the change in torque. That requires a rudder tweak given the short wing and short tail.

It isn't all that much of an adjustment, pretty small, so many times you don't do it until the change gets significant.

There is a key moment in MU2 flying when you understand how to trim the MU2. Once you know how to do that, flying it becomes much easier. Prior to that point, you tend to end up fighting it somewhat. I've flown the MU2 about 1300 hours so far, and trimming is so second nature that I don't really remember doing it. You are an MU2 trim expert when you can trim it out so it flies hands off for minutes.

A fellow pilot once said this about flying an MU2: "You fly with your left hand, but you think with your right." Meaning how you adjust power, flaps, and trim truly determines your flight more than how you move the yoke.

Mike C.

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 Post subject: Re: Well the MU2 is a nice ride, especially the Crossno expr
PostPosted: 06 Jul 2018, 02:54 
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Turbo Commander TPE331 perspective:

My 680V has a smaller rudder than later 690 models and you can really feel that at times. She gets really squirrely on go-arounds from a close-to-idle situation. In fact, I really don't like to pull her back too much on approach, as the risk for uneven power application in case of a go-around gets exaggerated. Those TPE's come on qick and they come on hard. It can be hard to control them evenly with sudden power lever increases. Steady and slow does it.

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Last edited on 07 Jul 2018, 00:02, edited 1 time in total.

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 Post subject: Re: Well the MU2 is a nice ride, especially the Crossno expr
PostPosted: 06 Jul 2018, 09:15 
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Username Protected wrote:
Is there no Yaw Damper in MU2?

Both the M4D and SPZ500 autopilots in the MU2 have yaw damper, but the MU2 doesn't really need it. When hand flown with YD off, you don't have any tendency to yaw oscillate and yaw disturbances are nicely damped.

FAR 23.181(b) talks about dynamic stability in yaw and that they must be damped to 10% in 7 cycles or less. I flew that test on the MU2 and it was about 1 cycle to be under 10%, which is very nicely damped.

Thus the YD is not a required system like it is on some airplanes and you could certify an autopilot without any rudder control if so desired.

I don't ever hand fly with the YD on. The MU2 doesn't develop bad yawing motions in turbulence.

Mike C.

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 Post subject: Re: Well the MU2 is a nice ride, especially the Crossno expr
PostPosted: 06 Jul 2018, 12:41 
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Username Protected wrote:
One question I do have regarding the MU2 experience is in regards to rudder trim. It required quite a bit of adjustments with airspeed changes. Curious why that’s so and if it’s a common characteristic to the type.

The MU2 requires rudder trim tweaks if you change power setting. The engine torque can vary from about 1750 ft lbs per engine at full power to perhaps -250 ft lbs per engine at flight idle, a difference of 2000 ft lbs over the throttle range, and there's two engines doing that. So you can't make significant power changes without countering the change in torque. That requires a rudder tweak given the short wing and short tail.

It isn't all that much of an adjustment, pretty small, so many times you don't do it until the change gets significant.

There is a key moment in MU2 flying when you understand how to trim the MU2. Once you know how to do that, flying it becomes much easier. Prior to that point, you tend to end up fighting it somewhat. I've flown the MU2 about 1300 hours so far, and trimming is so second nature that I don't really remember doing it. You are an MU2 trim expert when you can trim it out so it flies hands off for minutes.

A fellow pilot once said this about flying an MU2: "You fly with your left hand, but you think with your right." Meaning how you adjust power, flaps, and trim truly determines your flight more than how you move the yoke.

Mike C.



I don't see torque a direct correlation to rudder trim. It's the asymmetric disc loading , or P Factor that creates yaw and the need for rudder trim. I think in your analysis you were using torque as a measure of power and therefore P Factor, not that torque in itself created the need. Right?

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 Post subject: Re: Well the MU2 is a nice ride, especially the Crossno expr
PostPosted: 06 Jul 2018, 14:05 
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Paul - what’s the definition of Torque? All the Mu-2’s and TPE-331 powerere airplanes I flown, I set power by either fuel flow or torque.


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 Post subject: Re: Well the MU2 is a nice ride, especially the Crossno expr
PostPosted: 06 Jul 2018, 14:22 
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Many years ago I rode along in the right seat with a buddy of mine on his late-night mail run in a long-body MU-2J. At the time I was an FO on the EMB-120 Brasilia, which is a very rudder trim-intensive airplane. Any time you tweak the power levers on the -120, you have to make a corresponding small tweak on the rudder trim, along with some small tweaks of aileron trim. It's a routine in the terminal area with climbs/descents/speed changes; my left hand was constantly moving from the throttles to the trim wheels. I flew a few months as FO on the Metro III, and I don't recall ever touching the rudder trim on that thing.

I hand flew two legs in the MU-2, and my buddy commented that I flew the airplane really well...better than most of the other guys he'd let ride right seat. I said it's easy...just fly it like a Brasilia!


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 Post subject: Re: Well the MU2 is a nice ride, especially the Crossno expr
PostPosted: 06 Jul 2018, 14:28 
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Username Protected wrote:
I've not done measurements, but noisier in the cabin would be my expectation as well.

The King Air props are quite a bit more forward than the MU2 which keeps cabin noise down.

Mike C.


The long body MU2 is noticeably quieter in the cockpit than the short body due to the extra 3 feet forward of the props. I would still expect the C90 to be a bit quieter.


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 Post subject: Re: Well the MU2 is a nice ride, especially the Crossno expr
PostPosted: 06 Jul 2018, 14:35 
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Username Protected wrote:
Many years ago I rode along in the right seat with a buddy of mine on his late-night mail run in a long-body MU-2J. At the time I was an FO on the EMB-120 Brasilia, which is a very rudder trim-intensive airplane. Any time you tweak the power levers on the -120, you have to make a corresponding small tweak on the rudder trim, along with some small tweaks of aileron trim. It's a routine in the terminal area with climbs/descents/speed changes; my left hand was constantly moving from the throttles to the trim wheels. I flew a few months as FO on the Metro III, and I don't recall ever touching the rudder trim on that thing.

I hand flew two legs in the MU-2, and my buddy commented that I flew the airplane really well...better than most of the other guys he'd let ride right seat. I said it's easy...just fly it like a Brasilia!


Your experience with the Metro is what I find with the Merlin regarding rudder trim.


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 Post subject: Re: Well the MU2 is a nice ride, especially the Crossno expr
PostPosted: 06 Jul 2018, 17:23 
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Username Protected wrote:
Paul - what’s the definition of Torque? All the Mu-2’s and TPE-331 powerere airplanes I flown, I set power by either fuel flow or torque.


Torque is a twisting action to cause rotation, but it's not the cause of yaw in an aircraft to be countered by the rudder or rudder trim. Using the amount of torque applied to a propeller shaft is a common way of measuring power output in a turbo prop.


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 Post subject: Re: Well the MU2 is a nice ride, especially the Crossno expr
PostPosted: 06 Jul 2018, 20:01 
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Username Protected wrote:
Paul - what’s the definition of Torque? All the Mu-2’s and TPE-331 powerere airplanes I flown, I set power by either fuel flow or torque.


Torque is a twisting action to cause rotation, but it's not the cause of yaw in an aircraft to be countered by the rudder or rudder trim. Using the amount of torque applied to a propeller shaft is a common way of measuring power output in a turbo prop.



On these engines "torque" is used to define power. Lose an engine and tell me that it's not a factor that needs rudder.
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 Post subject: Re: Well the MU2 is a nice ride, especially the Crossno expr
PostPosted: 06 Jul 2018, 20:26 
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I have flown many many flights in the mu2 and never touched anything but elevator trim. The takeoff trim settings often work well from takeoff to touchdown for me. Part of that is that as mentioned the AP moves it around, but I have found as I have gotten more time in the plane, I am trimming it less. Can’t describe why other than maybe I am just better at exactly matching power levers? My solitaire is definitely sensitive to power lever mismatch, even a tiny bit.

400ish hours in the plane and I have to say, I find the trimming quite intuitive and effective. It’s still the only plane I have flown that will fly a single engine ILS hands off when trimmed right or can fly straight and level for minutes at fl280, hands off, ap off. It can be incredibly stable.


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 Post subject: Re: Well the MU2 is a nice ride, especially the Crossno expr
PostPosted: 06 Jul 2018, 21:36 
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Torque is a twisting action to cause rotation, but it's not the cause of yaw in an aircraft to be countered by the rudder or rudder trim. Using the amount of torque applied to a propeller shaft is a common way of measuring power output in a turbo prop.[/quote]


On these engines "torque" is used to define power. Lose an engine and tell me that it's not a factor that needs rudder.[/quote]

_______________________________________________________________________

Sandy,

Yes, torque is used as a measurement of power, but with the loss of an engine it's asymmetrical thrust that creates a yaw requiring rudder, not torque, just to be clear. :cheers:


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 Post subject: Re: Well the MU2 is a nice ride, especially the Crossno expr
PostPosted: 07 Jul 2018, 17:22 
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____________________________________

Sandy,

Yes, torque is used as a measurement of power, but with the loss of an engine it's asymmetrical thrust that creates a yaw requiring rudder, not torque, just to be clear. :cheers:


Ahem. What's the T in PAST? :)


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 Post subject: Re: Well the MU2 is a nice ride, especially the Crossno expr
PostPosted: 07 Jul 2018, 20:37 
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Quote:
Ahem. What's the T in PAST? :)


Ya got me...(?)

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