I've been flying a [link=http://wintellect.com/weblogs//images/wintellect_com/wintellect/3/o_twinstar.jpg]beautiful little Twinstar[/link] for two weeks now. Performs great with two O.S. 25FXs and MA 3-blade 8x6 props. The engines are breaking in well and have been extremely reliable--until today.

A few seconds after take-off, the right engine quit. I reduced power, made a couple of wide, gentle turns to line up with the runway, and brought her in pretty much normally. My heart was beating out of my chest. I put the plane on the bench and ran the engines up and down, let them idle for a while, and ran them up and down again. Everything worked perfectly, so I decided to go again.

Second take-off, same result: right engine quit just as I banked away from the runway. I brought her around again and managed get the plane back in one piece, although the landing wasn't exactly a grease job.

All this is to say that I can verify that the Twinstar flies reasonably well on one engine. The controls are mushy; it's a lot like flying a plane with one aileron. But I never touched the rudder, and as long as I was gentle on the controls, the plane responded pretty well. You can even run the power up and down without snap-rolling the plane if you do it gently. (I didn't try running the power up quickly; didn't want to invite disaster.)

The Twinstar is my first glow-fuel twin (I have a KMP B-25 almost ready to go, but I thought flying the Twinstar first would be good experience), and today was my first engine-out experience on a twin. I hope it doesn't happen again, but if it does, at least I'll know that there's no need to panic. Hobbico did a terrific job designing this model.

Glad to hear you 'survived',, Jeff..

Now,, instead of using ailerons,, learn to use the RUDDER...

And as long as a motor has quit running, by using the
rudder you can keep right on flying if you want/have to..

The B-25 will NOT be as forgiving so the more practice
you get in using the Twinstar the better off you will be..

Hopefully I won't get any more practice. :-)

One of my pals at the field says STAY OFF THE RUDDER when an engine goes. He flew full-scale twins for years (and used the rudder), but he swears that using rudder with an engine out on a twin model is suicide. Right or wrong?

JPro:

Quote:

...but he swears that using rudder with an engine out on a twin model is suicide. Right or wrong?

He could not be any more wrong. Models have to answer to the same aerodynamic "Laws" that larger twins do, it's just the Reynolds' numbers that are different.

Remember the ailerons effectively change the AOA of the wing. When you try to correct for a dead engine with ailerons you go to "Negative" incidence on the side with the engine running, and the prop wash ensures continuing airflow over the wing. The up aileron pushes the wing down, that wing panel still works normally. But on the other side... that aileron goes down, in effect increasing the incidence and therefore the AOA. Along with this we've lost the prop wash on that side, and unless your air speed is 'way up the wing panel with the dead engine will stall. Immediate spin, and unless you're high you will not recover before you have an unplanned landing.

Proper use of the rudder has saved many a war bird twin with a dead engine. I have never heard of the ailerons doing the same, but some planes like the Twinstar fly so well on a single engine that the error wont kill your plane.

Rudder use will make the difference between a plane that will fly again and a pile of sticks, shattered fiberglass, and crushed foam.

Hope my aerodynamics lesson wasn't over the top, but I wanted you to understand WHY the aileron was the wrong control for an engine out.

Bill.

Huh, perhaps this gentlemans storys of flying full scale for years included mostly passenger time in multis. Ask him if he's ever heard the expression "Dead foot, Dead Engine" and what makes him think that models are any differant. That "Dead Foot" portion means he is already applying rudder in the proper direction, Always rudder into the good engine.

Chances are he does Know this but in RC multis has bought into the old advice to cut the good one and land where ever.

Fact is most RC multis can Fly to a safe landing on one engine (Yes even some types with horrible rep's such as the P-38). A few can even takeoff on one. The point is you need to learn the technique. Robbys post is dead on and you should heed his advice.

Now instead of hoping for no more practice instead pick your day nice conditions and short tank your right engine, as oppossed to the more critcal left. Take off and fly around at a reasonable altitude untill it quits. This is almost cheating, you see since now you known which engine is going to stop and which rudder needs to be applied, but thats cool. There is time actually see the yaw of the aircraft and how control imput effects each axis. In the landing approach you will be holding at least some rudder but it will be gradually released as the power reduction is made.

Do this a few times and then do it with the left engine. Your B-25 will love you for it.

John

One: As Bill States : He could not be any more wrong

And do as John suggested.. Run one tank short on fuel and fly
on one motor.. Then do same with other motor...
And to add to John's... After you get comfy doing what he says,,
do it again,, but this time come into power faster to see how plane reacts..
Make sure you are ten mistakes high of course..

Part of the demo I do on the Hobbico Twinstar is to fly
on one motor and then to do a fast throttle increase
while on one motor.. If Irelied only on aileron, the
plane would have only done it once.. And then it
would be as Bill says.. sticks..

Your B-25 will NOT be as forgiving... So use your
Twinstar to LEARN motor out rudder control..

W R O N G !! [&o]

Wrong and I would bet he has never flown a model twin.

You might suspect a fuel foaming issue. On ground and in air airframe harmonics are most often different.

Bill

He has flown a beautiful Top-Flite DC-3 for years, although the only time he's lost an engine is at low power on final approach.

The reason he's so adamant that you shouldn't use rudder when an engine goes out on a twin is the following statement in Top-Flite's manual for the DC-3:

The good news is, if you are flying at normal speed and you lose an engine, all you need to do is continue flying
your DC-3 using only elevator and aileron. In all situations refrain from using the rudder when an engine quits. Otherwise, you may induce a spin.

Is Top-Flite afraid that you'll overcompenstae with the rudder, or is there something unique about the DC-3 that means using rudder in an engine-out situation is ill-advised?

One other thing you can do is to fly level and pick up speed. The rudder was put on the plane as a flying surface. If you gain speed the rudder and other controls will be more effective. The minimum speed the rudder will hold the plane straight is known as (for a twin) single engine minimun control speed.

I fly the model herk and have over 1000 hrs in the full size. The rudder MUST be used on the full size to get the bird back to the runway. I demo/ed this to a student when I was an IP. He would have made a smoking hole without the rudder.

Now for the model,, cautious use of the rudder is helpful. Remember you can't feel all the back pressure the servo does. In the real bird you have direct feedback to your foot.

On my model herk I mix ail to rud. That way when I lose and engine (twice in 35 flights) and turn into the good engines I have rudder to help. (WARNING don't turn into the dead engine unless you are extremely high and have lots of airspeed)

Jim

In other words he is what I call a crippled multi pilot, with absolutely no idea of what his airplanes characteristics are. RC Multi flyers who will not go the trouble of learning proper engine out techniques are the chief reason for the bad reputation and old wives tales about multis.

I,am Sorry but the gentleman is simply wrong and perpetuating an old wives tale. Asymetric thrust is Asymetric thrust period that will always react about the vertical axis no matters who's name you put on the kit box. That statement you posted from the kit while very well may be there is simply marketing hype and about as beleveable as all the hype of a certain new P-51 'trainer' with no instruction or mentoring required.


Single engine techniques are not intuitive and must be learned. They actually are opposed to what is ingrained in most single engine pilots, makes no difference how much single engine experiance that person might have. On the other hand the technique is not brain surgery and you can even learn it on your own by not listening to old wives tales.

I just wanted to say your approach is very refreshing taking the time to get the 'Trainer Twin' first to learn with is something many refuse to do before diving into that fancy multi whatever. Its great you first flights were so enjoyable and there will be many more.

John

I'll bet TF is worried you'll input the WRONG side rudder and really start "a series of unfortunate events".

cheers
Pneuman

Thank you, John,,

Well put....

Sounds like a good approach to me. I have a very nice Jack Stafford Twin Comanche sitting in a box on a cupboard somewhere, but I think I'll get a Twinstar as well to learn, even though it's a yucky ARF

I don't think that I would want him flying my DC-3 on just the ailerons. The F-un 82 on the other hand will fly on aileron only with either engine out and is capable of single engine take offs and single engine aerobatics. Twin vertical fins an rudders in the propwash plus a light wing loading make this possible.
I have flown two of the topflite DC-3s for another fellow and have made single engine go arounds with both.
I use the rudder and also the old light twin axiom that you can climb or turn with a dead engine but you can't do both.
For reference the F-un 82 has 2 OS 25 FXs and weighs 7+ # the DC-3 has Saito 100s and weighs 34#.

Jeffpro,

Regarding ailerons verses rudder for flying a twin with an engine out, here is the deal.

Airspeed is the main factor for control and pitch controls airspeed, so elevator control is the most important. If sufficient airspeed is maintained, aileron alone will work for engine out control. Bank it sideways and it sideslips. Sufficient side slip allows directional stability alone to keep it straight. This is not very aerodynamically clean though. Rudder is more directly effective at checking the crooked pull of an engine-out. But unless the design has positive roll coupling with yaw, rudder alone will not control roll and at least some aileron must also be used.

Although a twin with an engine out will just about go straight on its own at very high airspeed, most must dive aggressively to maintain that high speed. Using the proper combination of rudder and aileron allows safe directional control down to slower airspeeds closer to the speed for best vertical (climb) performance. All the stuff about proper single engine control technique from full size piloting has to do with preserving climb capability and reducing drag. Maintaining control has to do with airspeed alone.

The big danger flying on one engine is the stall. A stall with one engine running will produce the fastest snap rolls you ever saw. Including rudder allows directional control to be maintained at lower airspeeds than with aileron alone, and therefore reduces the airspeed margin above stall speed. Top-Flight recommends aileron only for their DC3 because higher speed is needed to maintain directional control. If you get their DC3 to slow using aileron only, it will turn gradually towards the dead engine. Using rudder also, you will be able to slow it enough for it to finally lose control by snapping.

Flying with and engine out is not hard but it is different and like any new maneuver it must be learned and practiced. The Twinstar is great for that. Use seperate channels and programmable mixing of a computer radio for throttle control. Then practice by throttling one back in flight, not by running one out of fuel.

Hope this clears things up.

Multiflyer

Excellent info, Multiflyer. Thanks!

I found out today why the right engine quit twice. The engine would run fine when it was the only engine running. But with both engines running at full throttle, vibration induced bubbles in the fuel line going to the right engine. A buddy and I fixed the problem by removing a bit of the padding from around the right fuel tank, making sure the tank was secure in the nacelle but not wedged in too tight.

I learned a great lesson today about some of the problems that are unique to twins.

BTW, I like your idea of putting the throttle servos on different channels so you can practice engine-out scenarios. The great thing about that method (as opposed to shorting one tank) is that you can run the second engine back up if you get in a real jam. Better than losing a plane...

How would you suggest doing the radio setup? Mix the two throttle channels and use a toggle switch to transfer control of the second throttle to one of the knobs on the radio? (I have a Futaba 9C.)

Everyone who has flown my triple with simulated engine out has become disorientated within two circuits. Practice in non-emergency time is the key to learning engine out flight.

I slaved the channels together, desensitized the pots for independent synchronization and put each engine shut back on a switch. I shut down the engine to a fixed 5000 RPM for reliability. Too much time at idle and the engine will not comeback up reliability and you will have a real emergency. It takes me about two hours on the bench including running the engines to set up the radio and verify that everything is operating as expected.

I have a Futaba and will dig up the details if you need or have difficulty.

At our field everyone stops to watch the crash when an engine goes out. A normal landing with one still turning is an ego trip.

Have fun.

Bill

Jeffpro,

As Bill touched on, if you are going to fly multiengine, then you should learn to fly with an engine out. There is no such thing as an engine that won’t quit eventually. If someone says there is, they haven’t flown it enough yet! When one fails, you can always just throttle the remaining engine(s) back and dead-stick in, but learning engine out flying is fun. It’s another challenging skill and aspect of aircraft performance to keep the hobby interesting.

There are many different ways to set up dual throttle channels. Some radios have dual throttle mixing already made up. The 9C has a "throttle needle" mix intended for in flight mixture control. This is basically a second channel moving with the throttle stick, so it can also be used for dual throttles as the 9C manual mentions. Set the needle channel menu adjustments to give standard servo throw for the needle channel (second throttle). I think the default settings are already there. Then this menu never needs to be revisited. Make all throw adjustments for each engine the normal way using sub-trim and end-point menus for each channel. Alternately you could slave up the second throttle channel by using a programmable-mixer, but then you would have to set up the second throttle travel using the p-mix adjustments. This gets a little more complicated because of the different things they can do.

After you have dual throttle channels working, add any additional features by employing more p-mixers. Basically you build the additional features you want using the generic programmable mixers (P-mix). All depends on your imagination. Also the p-mixes can be switched on/off allowing you to activate/deactivate whatever you dream up.

For engine-out training I recommend a setup similar to Bill’s, but including fingertip adjustment and eliminating the “hard” switching. Make it so either engine can be throttled back individually from the full throttle position only. I like to use each side slider lever as the master for this. Then use the throttle stick “soft” switch to activate these mixes only when at full throttle. This way you can fly up high at full throttle, then slide either engine power back only as much as you can handle. If you get into any trouble, just push the slider forward again or simply throttle back (the main throttle stick) a bit to disengage. A setup like this directly teaches the 2 most important things - how to fly with imbalanced thrust, and that throttling back removes the problem.

It is lots of fun, and the Twinstar is a great trainer for this, but CG it a little farther forward than the instructions recommend. The stock position makes it a bit pitch sensitive for easy engine out training. Let us know how it works out?

Multiflyer

Ok. I am currently building a Top Flite DC-3 hopfully ready for spring 2006. Top Flite designed the DC-3 differnt from the Twinstar and other twins. Both engine mounts have opposing thrust built in. Basically the left engine points a few degrees left and the right points a few degrees right. What this does is when running both engines there thrust is balanced so the opposition in thrust angles cancels out, but if an engine dies the good engine is pulling the A/C in the opposite direction. It's like stepping on the rudder to compensate for the dead engine. If you do use rudder and slam it 100% toward the good engine then you can have too much correction. Of course I haven't flown my DC-3 yet so I can't speak from experiance but the design of this model helps with engine out situations.

The TwinStar has plenty of opposing thrust. This is a common way to make twins a little easier to deal with in engine-out situations.

Good flying,
desmobob

Will do. The good flying weather is over for the year here in East Tennessee, but we'll get occasional flying opportunities as warm fronts move through. Number 1 on my list of things to do during cold weather is separate the throttle servo channels. First chance I get, I'll practice engine-outs and let you know how it goes.

Here are 3 thoughts to guide you while practicing engine out flying.

Control is all about airspeed, and pitch controls airspeed.

The natural reaction when control feels weird is to slow down and gain altitude for safety. For a multiengine plane you must train yourself to do the opposite. If the plane starts turning on its own, and you are correcting, and it is not responding, you must lower the nose to gain airspeed. The first reaction is to keep applying more and more correction. The proper reaction is to lower the nose until correcting becomes easy.

Here is a simple exercise from full size pilot training. In level flight, throttle one engine back. Speed will deteriorate and the plane will pull towards the weak engine. Apply correction to keep it going straight. After applying only a modest amount of correction stop applying any more and freeze the sticks right where they are at. Next, moving the elevator only, lower the nose enough to increase airspeed again. When sufficient airspeed has returned, the plane will turn towards the strong engine (towards your modest correction being held). Then raise the nose a bit to slowdown again and it will turn back towards the weak engine. Lower nose, speed increases, plane turns towards the strong engine. Raise nose, speed slows, plane turns towards weak engine. And so on… Continue flying the plane all around the sky using only elevator for turn control until the importance of airspeed sinks into your head (and thumbs) loud and clear.

Multiflyer

Ok,, lots of discussion,, Now a pic of how to do it,, Jim

I fly a Uravitch OV-10 with twin OS 25 FXs. It's a fast airplane, and always comes in for a landing in a "carrier landing mode" unless I use flaps to slow it down some. Both engines are a bit far out on the wing, somewhat similar to the P-38, so asymmetric thrust can be a problem with one engine out. I have experienced engine out, and with proper use of rudder, staying off the ailerons, I have no trouble flying a landing pattern to a normal landing. As you have read, keep up the airspeed, correct with rudder, and fly it down. By the way, I have mine set up for 0-0-0 and no out thrust. Flies great with that setup. This is a practice ship for me, as I am building a Ziroli B-25 and my experience with the OV-10 has been very valuable. Probably have 50 or so flights on it so far.

I think that all of you who are building twins will enjoy them. There's nothing like those two engines in synch in the air.

Keep us up to date on your B-25 results.

Lee