Well, having now been flying my first multi engine airplane for six months or so, here is what I have learned:

There is absolutely no difference between singles and multis.... as long as the engines are synchronized and none of them stop.

Pretty simple really. The plane really files pretty well, almost like a trainer (as long as you are paying close attention and not getting in trouble). I have had multi engine related issues four times now. The first was on my initial taxi testing and it was the middle engine that died so it really had no effect. In fact, I accidentally took off and flew several hundred feet on two engines.

The second time was on my first real flight. The left engine died on landing at about two feet of altitude and at idle so there was no real effect.

The third time was a killer. I had finally gotten the plane well balanced and sorted out and it was flying great. I even looped it twice. My landing pass was too high so I decided to go around. I floored the throttle and the left engine died. From 15 feet, the plane snapped and went straight down. I managed to pull out but it popped up and did a stall turn and came in nose first. Much damage ensued. I had expected a flame out of the right or left engine to be of minimal import considering the presence of the center engine, and maybe if the engine died at cruise rather than full acceleration, it would not be too bad. I don't really want to find out though.

The fourth time was minor. The engines were not sync'd and the right engine was too strong. I thought it was the rudder so I kept trimming it until it flew relatively straight but it was squirrelly. When I landed, the rudder was about five degrees right. I didn't have my tach with me but I am sure that was the problem.



The plane is a 1918 Caproni ca.42 and the engines are Saito .30s. I have three throttle servos with the pusher on the throttle channel, left on gear and right on spoiler. The latter two are mixed to throttle.

A truly unique and beautiful plane. You should be very proud of her. Congrats.

Thanks. It is somewhat less beautiful now. I built the plane as a quick (six weeks) project for a wwi combat meet and am using it as a test bed to determine the feasability of a larger, detailed scale version (it is feasable!) The repairs from crashing were quick, strong and obvious! This one has a 72" span. The next will be 117.75" and have a scale (very thin undercambered) airfoil. It will probably take another six months to finish the plans.

hereare some short, videos:
[link=https://home.comcast.net/~jchumley/caproni_startup_1.mpg]Startup video clip[/link]
[link=http://home.comcast.net/~jchumley/caproni_takeoff.mpg]Takeoff[/link]
[link=http://home.comcast.net/~jchumley/caproni_flyby.mpg]fly by[/link]

OH, MY GOD!! Wow...uh hey...there is room for another engine in front!!
Really nice.
twinman

Hey...thats what I was going to say.
There's room for at least three more engines.

Hey chumley, check out this thread if you haven't already: http://www.rcscalebuilder.com/forum/...p?TID=603&PN=2
It's kind of long but very interesting and informative.

Jim

P.S. Great job and nice videos! How do you get video clips on here?

Hello Jim:

Thanks for the link. I have been corresponding and getting help from Donny for a while. I had not seen this thread though. It will take a while to get through it all. As for the videos, I uploaded them to my web space at comcast.net. I get 20 meg of space with my account. Then I just point a link to them. They do take up a lot of space though so I probably won't leave them there too long.

Jeff

BTW, My Nieuport 28 is still on the bench. I made some mistakes and have not wanted to take the time to address them although I feel the urge coming on soon. Need to redo one wing tip. If you get the shape wrong on one wing when they are all eliptical, there is no hiding it.! I also need to sand off the 1/64" ply sheeting on the forward fuse and reshape the top, bottom and side panels a bit and replace the ply. Bummer.

Jeff

Just info on multi' engine. I fly a 4 engine model. What is important is what is known for your plane is single engine out minimum control speed.

By definition this would probably be (for your plane),

SEMCS: the lowest airspeed your plane can maintain directional control at level flight with Full Rudder and Full Power on the remaining engine and banking into the good engine.

When you were making your go around from a too high approach you slowed down. In your note you mentioned had you been at cruise you might have not had a problem. I agree with you, because you were probably below your SEMCS and there was no way you could power out of the engine out condition. If you lose an engine while below your SEMCS the only way out is to lower the nose and pick up speed then add power to go above the SEMCS and only then fly out of the problem.

I mix rudder and aileron on my Herk. so that in an engine out condition the natural tendecy is to turn with ailerons and with engine out turning into the good engines automatically gives you rudder in the correct direction. Granted this is not full rudder, but it gives you time to think about what the left hand is for.

I also fly my final approach at a speed at idle power so in the event of an engine failure I make the runway.

I noticed you were using saito's. I am suprised that one quit. I also use saito's and the only engine out problems were due to bad fuel and a defective (did not tighten the screw) tank.

I am using Cool Power 15% w/ OS F plugs and get very reliable operation.

You have a nice twin. Hope this information helps you. Best of luck.. Jim (see the C130 thread for the Herk info.)

Thanks Jim:

I have little experience flying anything other than singles so when the engine quit and it snapped, all I did was throttle back. I didn't even try using the rudder to right the plane and I think you are right that it would not have worked. I think I will set it up so I can kill the outer engines (it has three, not two) and take it up to altitude and practice flying with one dead engine. I can always kill both outer engines if I get in trouble and fly it on the center engine only.

As for the Saitos, I have only had trouble with this one engine. It could be an air leak I guess but it does not idle as well as the other two and it tends to die suddenly when it dies. I am not an engine guy but I suspect I might not have the air bleed set properly. It is still having issues but I am careful not to throttle back all the way until I am just about on the ground. I sould swap it out as I have another on a dh2 that I have not been flying much and being a single, it is not so critical.

I will check out the c130 thread. It is one of my favorite planes (and my wife's too).

Jeff

My experience is that tank foaming is much more critical in a multiengine project and air bubbles will often shut an engine down. Packing foam as though it was a single simply does not work for me. Any tank adjustment or work is subject to replacement of the foam tighter or looser. When possible I prefer for the tank to be boxed in on all sides with an exact dimension from the tank (3/8 or 1/2�) so the foam will be the same before and after tank work.

I also prefer to have the capability to shut an engine back to idle with the radio to gain the experience that will inevitably be necessary. Sooner or later one will go out. Learning all there is to know about single engine flying in the few split seconds after an engine goes down is not considered possible. I let a friend experience simulated engine out on my airplane a few weeks ago. He had difficulty maintaining altitude, orientation and control although he knew when I flipped the engine to idle and back to power. After the flight he commented that the throttle was no value with an engine out.

Bill S

It could be foaming, the plane vibrates alot at certain speeds including low idle. I do have foam around the engines but not alot because of the tight fit. As for idling on engine, I have the gear and spoiler pots mixed out on the outer engines but I can mix them back in so I can control them independently of the center engine. Sounds like I need to do it. If I have altitude, I have no problem cutting everything down and making a deadstcik landing but engines don't always cut out at altitude!

Jeff

One sure way to eliminate the foaming problem is to use a bubbeless type tetra or Jett brand tank that has no clunk. No air is allowed in the fuel chamber thus no foaming or unporting. Another advantage these tanks are installed without foam, nice in a tight nacelle.

I recently installed these in my Quad Kadet before its last flyin. My chief reason was momentary unporting during some aerobatics of the outboard engines (possibly due to centrifical force out on the wings and the inability of the clunks to keep pace. Takes a little longer to fuel and not cheap tanks but the obvious added reliability is worth it to me. Although it was interesting always before in a big roll as the outboards unported just for a few seconds, hearing the crowd gasp and waiting for a crash only to be disappointed. This no longer occurs with the Bubbeless.


These have been pretty standard with the pylon crowd for years now and the fuel delivery performance is far better than a conventional muffler pressure system. So much better that CG mounting is possible on many aircraft. This could be of great benefit on some nacelle mounted multis also.

John

Jeff,

I have had the radio set up all sorts of ways but the best experience has been with two switches to shut left and right back to 15% throttle or between 5,000 and 6,000 RPM. Almost as much simulated engine out time as regular flight time has been accumulated. Still after about three circuits with simulated engine out disorientation starts to occur. In the process of fooling with the radio lots of real engine outs have occurred. In addition two other switches are used to completely shut left and right down. It is easy to forget and use the wrong switch.

One problem we encountered was an unknown shutdown at low throttle that turned disastrous when someone throttled up to go around. Jamming the stick to full created an abrupt right flat turn and no one knew why until the pieces were being picked up.

A sane man should not be having this much fun.

Good luck on your experiments. Have fun.

Bill S

JohnBuckner,
Who handles the Tetra and Jett fuel tanks?

The Tettra tanks and other accessories are available from Central Hobbies, the Jett tanks from Jett engineering.

Bill.

Thanks again.
Chuck

Thanks BIll, That is exactly what happend to me. I think. The plane was even with me when I throttled up and teh engine was on teh far side so I don't really know if the engine died because I throttled up or if it was already . Anyway, it dropped a wing and went down in a hurry.

Jeff, earlier I sent the following exert to my friend who crashed.

Three alternatives might be considered to sort of solve the unknown dead engine problem, prudent throttle management, high throttle limits programmed in the radio (too much power), and an engine out alert. None are good alternatives. In the learning stages the mental/emotional restraint associated with prudent throttle management (slooow) is overwhelmingly difficult. Another split second lapse is inevitable. … It goes against all known experience to throttle down to get out of trouble.

Bill S

Carlos here is a little tutorial on the Tetra at Darol Cadys site He has the Tetras up to Six ounce which is what I use. The larger sizes are at Central hobbies. To properly fill you will need the Jatt Tanker (a large syringe) that allows all air to vacated before the fuel is pushed into the bladder. Darrol Cady also has the Jett tankers and i will find the link for Dub Jett in a moment.

http://www.darrolcady.com/Tettra_Tan...tra_tanks.html

Here is Dub,s site where you will also find tutorials and a variety of his tanks for very slim installations. One of which is called the CG tank (this is because it is very slim) that will slide into a very small nacelle. I had great luck in running bubbless tanks as far back as eight inchs from the firewall in a variety of installations.


http://www.jettengineering.com/

John

Thanks for the help John, I'll check them out.
Don't some "baby bottles" use the same principal?
Chuck

Yes its the same idea I suppose, in fact I use baby bottle replacement liners in my crashed tanks. In crashs these tanks usually do not survive as the bladder is impalled on the pickup tube. Its a little tricky and a little less durable but on my pylon crash tanks that the hard outer shell is good I replace the bladder with baby bottle liners and use these tanks for some applications other than racing. In fact the four in the Quad are all baby liner crash tanks.

John