This is great info, thanks for the idea "twin sync" i'll be reading up on it.....BILL

Hi Guys,

Well, it seems we are comming near to the core of discussion again: - What is more and what is less important, i.e. That was my question
to lot more experienced pilots = Please, create a short list of the important things, in order of priority, could be Top-10, or if that is too
short, then let it be Top-50 with some Weight-factor, i.e. number from 1-10 or 1-100 where we can see how much more important
or less important are the different items. I believe this list is of major importance and you could eventually pulbish it in some
model RC magazine too with lot of photos of successes and crashes - then lot of people will pareciate your effort and there will be
good trace left from your experience and you might get paid eventually too.

As for the gyro, I do not understand why is expensive, because one gyro cost only 35, USD (check on Tower hobbies GWS type, code LXHHS2).
Further more, with full respect to TwinSync, the gyros I use replace almost completely the need of TwinSync and they do not need any even
efforts to be installed compared to the instalation of a magnet to high-RPM, even two of them. Here is what I am doing and it works in a very
similar way: Gyros on each of the three axes, and the rudder gyro is also controlling differentially the engines throtles. I think that the
TwinSync is very good demonstration of good electro-mechanical knowledge and skills but there are too many moving parts while in
the gyro there aren't any, and also mounting is just possible by using an adhesive tape, i.e. for not very experienced in electro-mechanical
works person the gyro is lot more simple and easy, even might be cheaper. And the gyros are easily overrun by the pilot commands.

Another completely novel Direction is to use the Two-Way communication between the Airplane and Pilot based on the newest Futaba
Radio-system and also offered by the Australian Spektrum. Then you could be as "informed" as you were on board. Check at least
on Tower Hobbies LXPZT8 code, and it is comming on devastatingly lower price than the regual FM and ppm or whatever expensive
radios which belong to the Grand-father era of superheterodines. Here also you do not (!!!) have to think about Channel-Numbers
and more importantly - do not have to be afraid that someone will enter your frequency and cause you a crash. And then you
can see or hear or even mount a camera on board of your RC-plane and eveything comes with the same Radio system - the
data band-widht is good enough; of course this is just the beginning, thus lot more news will follow soon on this Modern Digital
Two-Way Communication Radios.

Well, in general we like nice mechanical solutions but if we can replace them with electronics without any(!) moving parts, that
is lot more secure, isn' it, and also if we can be "on-board" of the Ariplane that is lot better. Those are the reasons why I am
so much after gyros and Spread-spectrum system. Well, if you are wandering why then I do not fly electric, the reason is
that motor-sound which is a "music" to my ears, i.e. I can be not reasonable as well, beside that electric is ex*****ve from
the batteries point of view, but that is another topic for another forum.

Cheers,
Nick

Point well taken on cheap gyros. I fly heli's so when I think of a gyro I think $150 (good heading hold). I am a little confused by your comment on moving parts? There are no moving parts in the TwinSync? It is all solid state? It uses the existing throttle servos. If you have glow motors rather than GAS with EI you have to install a magnet on the crank. So maybe you were refering to the magnet as the moving part. I have an optical system for the Twinsync that I have not released yet that truely has no moving magnet/part.

The hardest thing the TwinSync solves is matching the engine RPM. That really difficult to do without it. Same engines, same props, etc. do not necessarily run at the same speed at the same carb settings. Engine out functions are just a side benefit.

If you don't fly electric because of the sound of the engine, I would think that you would want that harmonic sound on your twins when the engines are synchronized rather than them turning different RPMs.

Here I can start your list for you:
1. use known reliable engines
2. Fuel tank for each engine (if possible)
3. If glow engine try to aviod inverted mounting
4. If inverted glow have on board glow driver
5. servo per engine
6. Adujust each engine seperately on the ground
7. do not try to synchronize engines with needle valve settings
8. practice flying the plane on one engine (through radio or twinsync programming options)
9. fly 1 mistake high
10. get time on the plane initially while you are the only one flying (you can not hear the engines if multiple planes are in the air)

and finally - don't try to go arround on one engine unless you are high enough that you can dead stick it in after a snap roll. (I unsuccefully tried that with a P38 a couple of weeks ago.)

I like especially that HARMONIC SOUND !!! That is more than an attractive point !!! And for sure it is nice to have all possible security precausions taken
thus I am getting more and more behind the idea of the TwinSync. Since you seems very deep in the works on the synchronizations, have you tried to
use as sensor on the pressure from the chrankshaft case. It might be well combined with those cases when that pressure is used to drive the Perry pump
and on the pipe you could wrap a piezo-crystal from an old CD-ROM axes stabilizer or even buy some; they cost only few cents and driving voltage is very
good to trigger your system. Also single-chip micro-controller might be suitable and eventually cheaper; you might have been considering those options
in order to make the TwinSync in cost of less than 50 USD even, maybe. Anyway you were right to notice that I do not like to use moving parts even
optical ones; I think would be better to exhaust all other means and they are maybe few more. Please let me know your considerations on this. And
one technical detail question: - what is the comparator window of the RPM range, i.e. what precision of the RPM setting TwinSync is maintaining at
different RPM, +/- 5% or more or less, in fact this depends on the carburator, engine etc, i.e. what is "locking-range" of the RPM and how it varies
with the specific RPMs ? Regards, Nick.
P.S. I missed some point maybe in the past discussions: - On which WWW-page I can see more and also how to order the TwinSync and is there
any problmes to have that mailed to Finland ? How much the whole deal will cost and which way to forward the payment, PayPal for example ?

Good ideas on the pressure and piezo sensor. I may look into them down the road (too busy right now trying to get other new products out). As for the technicalities...

RPM is measured by timing each rotation in 10us increments. per rotation. This equates to 1.5 RPM acuracy at 5000 rpm and 66 rpm at 20K rpm. The "lock range" of the TwinSync is programmable (only by me though - not customers). I currrently have it set to declare sync if the engines are within 130 rpm. Most people and reviewers typically find the sync accuracy to be about 50 rpm with the lock range set to 130rpm. I can tighten it up but what happens typically when I tighten it up the throttle servos will ocsilate +/- about .5 deg back and forth and you get a blended rpm that is still about 50 rpm apart. I really think that 50 rpm is about the limit of most carborators in terms of acuracy when connected to a servo. 50 RPM is very impressive on a Walbro carb (that is super sensitive) or my OS40 FSRs that turn about 14K on the test bench videos. You definitely can not hear 50 RPM difference. They typically sound like one engine almost.

You can order from www.rcshowcase.com or me direct [email protected]. I don't think they take paypal but I do.

As for getting the price down. Not much savings left just not enough volume in the product to get it down. If you wanted to buy 1000 <$50 or even <$35 is no problem.

Bill is absolutely correct. The alert that an engine is down is the critical first step. Twinsync will let you know when an engine is down long before you can possibly recognize the condition any other way. Engines can and will quit.

What you do next depends on the airframe and your practice with a dead engine emergency. For most the next step should be to dead stick anywhere you can. Most will throttle up. Most will break the airplane. Not pretty but true.

I had literally hundreds of successful engine out landings before Twinsync was conceived. But yet I own a Twinsync. Often I fly as far as 600 feet away and the change in sound takes over a second to reach you. In addition a change in attitude of the airplane can be caused by many things other than engine out including but not limited to wind gusts, thermals, air across the treetops, etc. Recognizing engine out is the first and most critical step necessary to save the airplane.

Bill


Incidentally I don’t know a thing about gyros, never do inverted engines, have never used glow heat, and have never used a pump or regulator. They are probably good devices and solutions but not for me.

bill very interisting on the optical senrors. When do you expect to launch the same

Regards

Ed Moorman, BillS, Jaka, yl5295, I agree with you all. Depending on the plane, the circumstances and pilot skills, you only have precious few seconds to analyze and react correctly to an "flameout", especially at low altitude. Because I know I make mistakes, I'm going to get a TwinSync just so I can get a engine out warning ASAP (not when I finally figure it out!). I think Ed is right, a few hundred RPM difference isn't nearly as important as a 10K RPM difference (flameout), but an early warning might save my plane. Thanks for designing the TwinSync, Bill!
-Les-

They are in the queue. I am hesitant about releasing optical. Dirt, oil, sun, lots of thing that can go wrong with optical. I don't want to ever crash a customers plane... So far no crashes due to operation of the twinsync. I want to keep it that way. Hall sensors are highly reliable compared with optical. Plus hall sensors are more permantely mounted.

Design of the aircraft makes a huge difference. I converted a Goldberg Protege to twin (MDS 40s, then Saito 56s) and really enjoy it. Left engine is set at 0 dehrees, right is 6 degrees right thrust. I've had several engine outs, each side, and it merely slows down. Once I had an engine off - the entire nacelle with engine, fuel tank and servo departed in flight. That time it rolled toward the heavy side, but was easily recovered with aileron.

When all else fails, FLY THE PLANE. It requires conscious effort to hold the sticks over to where the plane flies straight. Forget about trimming to compensate - just fly the plane. If all else fails, cut the power, push the nose down, and fly it to the ground.

One factor not mentioned so far is why a twin becomes hard to fly in a single engine configuration.

For every conventional twin, in a single engine configuration, there is one airspeed at which the combination of rudder and aileron cannot provide enough force to counteract the yaw forces caused by the remaining running engine. Below this airspeed the remaining engine will simply pull the plane in an out of control condition towards the dead engine. That airspeed is the minimal controllable airspeed or V mc in the full-scale world. Note that this airspeed is often higher than the normal stalling speed of the airplane.

Speed is life.
Contrary to previously made statements in this thread, if the airplane is in normal cruise, and you loose an engine the best possible course is to go to start a decent and slowly go to full throttle on the remaining engine to gain as much speed as possible. Then trim with rudder and aileron to maintain straight and level. With speed you have control and you are moving away from Vmc and toward safety. The wonderful little Hobbico Twin Star 25 behaves exactly in this manner when powered with .25’s. It can even do single engine touch and goes if you keep up the speed. The advice listed in this thread of going to a reduced power setting on the remaining engine only increases the probability of accidentally flying below Vmc. The other advice of treating it as a dead stick, going immediately to idle on both engines and pick a place to land guarantees avoiding Vmc but doesn’t do you any good if the dead stick is going to smash the plane in a bad off-field landing. So to extend flying time go to full throttle. BUT…for a given model that may still lead you to a Vmc condition. The single engine still isn’t strong enough to pull the airplane fast enough to maintain airspeed. This is where you have to learn what YOUR model will do in an engine out condition.

Don’t Panic!
If you’ve gone to full throttle on the remaining engine, and your plane has become a monster turning into the dead engine. Go to idle and glide. You eliminate the forces that are causing the out of control condition.

That just aint so
I have the UTMOST respect for TWINMAN and his series posted on the link but when a model looses an engine, it looses 50% of the power and about 55% of its thrust. The 90% issue he points to in his article is true of a 1:1 sale plane while the propeller of the dead engine is wind milling. The drag caused by the spinning prop does a lot to slow down a full-scale plane, that’s why you feather it as quickly as possible to eliminate the huge drag of that prop. Our model engines (IC at least) stop almost instantly so the small frontal area of the stopped prop is the drag. The bigger problem we have is not getting off the elevator. We think that height is life when it’s speed. Get the nose level or down if possible and accelerate and use all the energy you can get, and then fly home!

MTC, YMMV, Just another factor to consider.

Tom

All good information. Unfortunately for modelers, the only feedback we can count on when things are going sour is our visual feedback (audio is sometimes useless at a noisy model field). We don't get the seat of the pants info, the stall warning, airspeed, etc. Different situations and different airplanes require different solutions to an engine out scenario. If for example your plane is flying perpendicular to you and 500ft out, it may take the average modeler a few seconds to recognize there is an engine out and how to respond to it. With a high wing loaded P38, your plane may already be in trouble. Now the plane is turning toward you, yawing and rolling right. You inadvertently give it right rudder in the confusion and your plane spins in. With a slightly nose heavy plane, if you throttle back the good engine, the nose will drop and the plane will continue flying if you stay off the elevator. Assuming you still have some altitude, you can correct the plane's attitude, ease the throttle back on,add some rudder and aileron and fly the plane. Even though everything you said is true, the circumstances are different for a model airplane. Also remember most modelers have more than one plane, a twin is just one of them. It's probably safe to say most modelers will never have hundreds of hours flying twins; devices like the TwinSync could help save a plane for us part time pilots. (No, I don't know Bill!)

Hi Guys,
I have been reading all those nice advices and preferences and it is hard to accept that Gyros should be excluded and forgoten
and only engine synchronization is the solution ? - If that is the current status of mind, then I think it is heavily wrong because
as it is said "the butter does not replace the bread", meaning, when one engine stops, that "body" is out of use while the
Gyros do not depend on any engine rpm. Placing Gyros for the all axes of the Airplane and also for throtle of the engines
will increase the safety a lot - just consider those gyros to be your savier because they are onboard, while you are on the
ground, they "see and feel and react" about 100 times faster than the best pilot; wouldn't you agree ? And they cost just
so little (about 50USD per piece of GWS type in Tower hobbies). If you set them right, they will fly your plane for you.
Of course synchronising the rpm of the engines by other methods is nice, but still can't fly your plane as the Gyros will.
I have tried that, and it is so simple and easy to make it and it is so safe; you have to apply efforts to crash the plane.
Cheers,
Nick

Great question to ask before you lose an engine on a twin. I have about 2000 hrs on heavy turbo props and 10 hrs on model multi's.

Haven't lost a bird yet, but have had at least 5 model engine failures in flight.

I always mix rudder and aileron for cordinated turns and this will immediately help on engine out. The time between engine failure and crash is about 1.2 heart beats, so you must know how to recognize a engine failure without depending on hearing a change in the engines.

If you lose an engine low and have never had an engine failure I would go to idle and land immediately. I know this might be a hard landing but if you power up most probably depending on bird design, will just snap into the ground. If 500 ft high then try to fly level with full rudder (use mixing) and if you can't maintain direction go to lowest power setting you can steer and land.

Jim

p-47s are singles what plane did you mean

NikolayTT,

I never said gyros were a bad thing - I am actually developing one for airplane use. Gyros are good if you are going to fly with asymetrical thrust in a one engine situation. The twinsync prevents ever having asymetrical thrust (unless the pilot decides to override it).

I successfully landed my 95" p-38 6 times on one engine with a go arround each time. #7 resulted in a snap roll straight in from 20' at the end of the runway. A gyro would have not have saved it. Too low and too slow trying to get back to the field - too much rudder and aileron trying to hold it and I stalled the skinny wing on the up aileron side. Everyone on this thread is right. There is not a generic solution for all airframes and situations. If I had a $10K P-38 it would have gyros.

The problem with gyros are that they are designed for heli tail rotors or hovering a 3D plane. I haven't figured out the best gyro algorithms for a twin but I am working on it and would like input. A heading hold forces you to fly or mix the rudder. It is ok for scale flying but limits certain manuvers. A non-heading hold will drift and let the tail follow the nose but probably has other drawbacks from flying them in helis.

I do think that you would only want a gyro on yaw and not on roll or pitch. Roll might be nice. I would think that you would want heading hold on roll on and no heading hold on yaw. ideas?

Hi,

You are right, gyros are not universal "medication" for the troubles. I just wanted to underlign that having in parallel more
than one system and On-Board makes the things lot more safer than only one system indeed. Gyros are very light and the
only confusion here is what kind of gyros one is considering. Lets make it more clarified: - Head-lock gyros are too complicated
and too expensive. The one I use is cheapest one and has no-lock capabilites. Also it is very easily overrun by the comands
from the sticks - when stick is pushed, that type of gyro has almost no effect, of course on the ground one has to set the
gyro to min-sensitivity. Also, gyro is a panic-medication that way; just release the sticks and the plane gets stabilized by
those gyros, especially when the plane is too far for the pilot to see or listen what has gone on board.

Well, no to scare anybody but the equipment developers know that self-oscillations of gyros and in general for more
complicated systems are SECONDARY effects which can destroy the whole idea and that is why is better to use the
systems(here the gyro) at the lowest sensitivity level to avoid self-oscialtion of the combination of Airframe+Engines+Gyro.

Cheers,
Nick

Perhaps a P-47 is a C-47 on attack.

Practice, practice, practice.

Almost no one I know practices engine out. The skill of saving the airplane cannot be discovered in real time.

You can go over the methodology a thousand times in your mind and the fingers will not cooperate unless practiced. You don’t even know if your method is correct until you practice.

I set the radio to drop one engine to high idle, go high and practice. I fly until disorientated and bring the idle engine back up. It takes a few flights to teach the fingers and to discover the single engine characteristics of the airplane. In the event that the idle engine does not come back up I dead stick the airplane.

I have several hundred real engine outs and never a crash but have landed in some very strange places.

Bill

first step turn around. second step get on one knee and pray. thrid step walk away. [&:]

Just kidding. I managed to wreck my twin avenutura ELECTRIC on maiden. The stock props were push ons. I had just taken off and turned right when one engine's rpm wwent real high. She threw a prop. Not enough altidude to throttle down. sprirelled in. It flys today though. That was a sick sound as it hit the water. KAPUD

i have a 100" p-38 and have many engine outs, thank god i have a twin-sync in her. gyros, in my opinion is unnessary added weight, they will mask the problem of engine out, a twin sync will solve the thrust problem that causes so many twin wrecks.

Hi Guys,
I take my hat off to all you people who can fly I/C twins and cope with a sudden engine failure. I had it once on an IC powered Beaufighter and only just saved it. If you have lightining reactions and are ready for it then fine. I have seen so many twin stuffed and it is normally on a test flight.

Now my models are electric I really don't have to worry, HE111, Beaufort, Lancaster, Halifax, Beaufighter, JU88, Mosquito and Hornet all mostly around 100". They have become progressively heavier and are now more comparable to I/C planes, but the big advantage is engine reliability. The Beaufighter, and HE111 have had over 100 flights and the others range around half that and I have never had an engine failure... Gulp, it's probably going to happen tomorrow now that I opened my big mouth!

John

I have 7 flights on my Nitro 90" P-38. I put 2 new engines on it and broke them in for about 2 hours before the first flight. I had an engine out on my first flight but the GWS Piezo Gyro I had on the rudder saved me big time. It provides the quick rudder response needed to keep the model flying straight and it lets you know to cut the power asap. Someone mentioned engine tuning and he's right running the engines a little rich has helped me complete my flights without a problem.

For me, part of the facination with my twin is the possibility of engine out. If it was easy everybody would be doing it. No doubt I could just stick with single engine airplanes or go with electric but what would be the difference then.


http://youtube.com/watch?v=_OYwG5n6KZA

I agree, part of the thrill of flying twins is cheating "fate". Carefully tuning both motors will probably avoid most engine out problems in the first place and I think it puts you a notch above many modelers. Having an emergency plan is always a good idea. Simply put, flying IC twins puts you in a different league!