Multi Engine-Out Training Device
04-09-2007, 12:53 PM
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Multi Engine-Out Training Device
Hi Guys,
We were wondering what feedback you could give me about a new product we have developed. It's an engine out simulator and trainer for use in actual flight. We call it the ATT.
Preface:
We are an electronic accessory design team that is constantly seeking new and better ways to address the concerns of the aero modeling community. Our latest idea revolves around increasing the survivability of One Engine Out (OEO) conditions. In the past we have addressed this from the point of view of controlling the airplane after the unspeakable has occurred. We have developed a automatic yaw correction device that does not use gyros and is far more accurate than gyros using accelerometers (more on that latter). Lately we have turned our attentions towards heading off the problem much in the same way full scale pilots do - by practice and learning. We feel that skills offer better protection for failure than devices. So, the Advanced Twin Trainer (ATT) was conceived.
Idea:
In keeping with the idea that skills are necessary in all endeavors in RC modeling, we thought it would be a good idea if we could adopt the full scale principals in engine out training. Looking at what we've seen in videos and accountings of engine out failures on multi's, we almost always 'see' what goes wrong and most all the time the plane could have been saved if the proper procedures were employed. We think that most pilots simply 'hope' that an engine out situation on their twin doesn't happen at the wrong place and at the wrong time. Some can even log engine out time on their planes owing to better than the worse situations while others have really learned to fly on one engine out. The ATT will allow for a controlled OEO in a planned and learning environment, allowing for learning and practice to evolve into skills.
Physical:
The ATT uses a PCB mounted circuit that reads signals from the receiver about the mode of operation and throttle position and uses microcontroller. It weighs about 5 grams and mounts between the receiver and the throttle servos. It's powered by the receiver battery pack through the servo wire connections, utilizing 4 or 5 cells. Power consumption is less than 10 ma., usually less then 5 ma..
Operations:
The ATT is designed to give an idle throttle condition to one of two engines when a switch or knob, utilizing an auxiliary channel, is moved to one of two states. The operation will randomly select which of the two engines to reduce to an idle condition. Moving the switch or knob on the auxiliary channel again will restore full and normal operations to both engines. The engine that is selected for manipulation will be reduced over a 2 second period of time (assuming the initial throttle state was full power) and restored to full operations over a 1 second period of time (assuming the restored setting is full throttle). The idea about taking a bit of time is to avoid the actual killing of an ill adjusted engine.
On power up, the device reads the throttle settings and records the lowest setting seen from the receiver. It then adds about 10% (equal to a high idle using the trims on the transmitter) to this value and will use it for the base idle setting. The device also reads the state of the auxiliary channel and assumes that this is the position for ATT being off. When turning the receiver power on, it will be necessary to have the transmitter on and have normal idle stick and trim positions. Once both engines are running, advancing the throttle to high power and then exercising the auxiliary channel switch or knob will demonstrates the devices affect on one or the other engine. Each time this condition is entered, it's a matter of random selection as to which engine will be idled. Both engines should be checked that the idle is acceptable.
Now in normal flight and at a safe altitude and sky placement, the aux switch or knob can be moved to the opposite side and one of the two engines will be reduced to idle. At safe altitudes you can practice steep climbs, climbing turns, slow flight (strait and turns), flight with flaps and gear extended and unusual attitude recovery should a stall or spin be entered. The practice format would mirror much of what full scale pilots go though to learn multi engine aircraft. If at any time you wish to restore the engine that is idling to that of full and normal control you only need to move the auxiliary switch or knob back to its original position.
A switch on the ATT will block all attempts to enter an OEO mode from the auxiliary switch or knob (OFF switch), allowing an easy transition from a learning sessions to a normal 'let's have fun' session. There would be no need to remove or reinstall the device. The device also looks at the throttle input(s) and determines if there are two channels being sent out to two engines or if there is just one. One input is marked E1 (for engine input 1) and E2 (for engine input 2). If no E2 signal is present, then the device will also act as a selectable servo reverser for the second engine (if needed) by selecting a reverse switch (again, if needed). When both E1 and E2 signals are seen at startup, neither is reversible and reversing would be handled as normal in your setup of the transmitter. If you use an idle-cut switch or trim setting, they will continue to operate as normal in all modes of operation.
Conclusion:
We are currently testing the device and are only preparing to offer it for sale. Final price has not been set yet, but we expect and easy to accept pricing of about $30, give or take a bit. We would be very appreciative if this group would offer any feedback (positive or negative) about what's been addressed here or on topics not addressed.
Gary Warner
[link=http://www.york-electronics.com]York Electronics[/link]
We were wondering what feedback you could give me about a new product we have developed. It's an engine out simulator and trainer for use in actual flight. We call it the ATT.
Preface:
We are an electronic accessory design team that is constantly seeking new and better ways to address the concerns of the aero modeling community. Our latest idea revolves around increasing the survivability of One Engine Out (OEO) conditions. In the past we have addressed this from the point of view of controlling the airplane after the unspeakable has occurred. We have developed a automatic yaw correction device that does not use gyros and is far more accurate than gyros using accelerometers (more on that latter). Lately we have turned our attentions towards heading off the problem much in the same way full scale pilots do - by practice and learning. We feel that skills offer better protection for failure than devices. So, the Advanced Twin Trainer (ATT) was conceived.
Idea:
In keeping with the idea that skills are necessary in all endeavors in RC modeling, we thought it would be a good idea if we could adopt the full scale principals in engine out training. Looking at what we've seen in videos and accountings of engine out failures on multi's, we almost always 'see' what goes wrong and most all the time the plane could have been saved if the proper procedures were employed. We think that most pilots simply 'hope' that an engine out situation on their twin doesn't happen at the wrong place and at the wrong time. Some can even log engine out time on their planes owing to better than the worse situations while others have really learned to fly on one engine out. The ATT will allow for a controlled OEO in a planned and learning environment, allowing for learning and practice to evolve into skills.
Physical:
The ATT uses a PCB mounted circuit that reads signals from the receiver about the mode of operation and throttle position and uses microcontroller. It weighs about 5 grams and mounts between the receiver and the throttle servos. It's powered by the receiver battery pack through the servo wire connections, utilizing 4 or 5 cells. Power consumption is less than 10 ma., usually less then 5 ma..
Operations:
The ATT is designed to give an idle throttle condition to one of two engines when a switch or knob, utilizing an auxiliary channel, is moved to one of two states. The operation will randomly select which of the two engines to reduce to an idle condition. Moving the switch or knob on the auxiliary channel again will restore full and normal operations to both engines. The engine that is selected for manipulation will be reduced over a 2 second period of time (assuming the initial throttle state was full power) and restored to full operations over a 1 second period of time (assuming the restored setting is full throttle). The idea about taking a bit of time is to avoid the actual killing of an ill adjusted engine.
On power up, the device reads the throttle settings and records the lowest setting seen from the receiver. It then adds about 10% (equal to a high idle using the trims on the transmitter) to this value and will use it for the base idle setting. The device also reads the state of the auxiliary channel and assumes that this is the position for ATT being off. When turning the receiver power on, it will be necessary to have the transmitter on and have normal idle stick and trim positions. Once both engines are running, advancing the throttle to high power and then exercising the auxiliary channel switch or knob will demonstrates the devices affect on one or the other engine. Each time this condition is entered, it's a matter of random selection as to which engine will be idled. Both engines should be checked that the idle is acceptable.
Now in normal flight and at a safe altitude and sky placement, the aux switch or knob can be moved to the opposite side and one of the two engines will be reduced to idle. At safe altitudes you can practice steep climbs, climbing turns, slow flight (strait and turns), flight with flaps and gear extended and unusual attitude recovery should a stall or spin be entered. The practice format would mirror much of what full scale pilots go though to learn multi engine aircraft. If at any time you wish to restore the engine that is idling to that of full and normal control you only need to move the auxiliary switch or knob back to its original position.
A switch on the ATT will block all attempts to enter an OEO mode from the auxiliary switch or knob (OFF switch), allowing an easy transition from a learning sessions to a normal 'let's have fun' session. There would be no need to remove or reinstall the device. The device also looks at the throttle input(s) and determines if there are two channels being sent out to two engines or if there is just one. One input is marked E1 (for engine input 1) and E2 (for engine input 2). If no E2 signal is present, then the device will also act as a selectable servo reverser for the second engine (if needed) by selecting a reverse switch (again, if needed). When both E1 and E2 signals are seen at startup, neither is reversible and reversing would be handled as normal in your setup of the transmitter. If you use an idle-cut switch or trim setting, they will continue to operate as normal in all modes of operation.
Conclusion:
We are currently testing the device and are only preparing to offer it for sale. Final price has not been set yet, but we expect and easy to accept pricing of about $30, give or take a bit. We would be very appreciative if this group would offer any feedback (positive or negative) about what's been addressed here or on topics not addressed.
Gary Warner
[link=http://www.york-electronics.com]York Electronics[/link]
04-09-2007, 03:59 PM
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RE: Multi Engine-Out Training Device
Gary,
In reading your text I see you make mention of "automatic yaw correction device " ...
Yet, following that part the rest of text discusses a throttle management system..
Is that what your device is, a throttle management device?
There are devices currnetly on the market as such.. More recently
the Twin Sync which does as you describe plus has more features
which are desired by most modelers..
In reading your text I see you make mention of "automatic yaw correction device " ...
Yet, following that part the rest of text discusses a throttle management system..
Is that what your device is, a throttle management device?
There are devices currnetly on the market as such.. More recently
the Twin Sync which does as you describe plus has more features
which are desired by most modelers..
04-09-2007, 04:03 PM
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RE: Multi Engine-Out Training Device
The ATT will work on 4 engine systems, but only control two engines (one at a time, in random order like described in the text). As of now, we are not moving to a dedicated 4 engine system, though if the demand is there, we would consider making them.
04-09-2007, 04:41 PM
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RE: Multi Engine-Out Training Device
No, this isn't a throttle management system. It's a way of duplicating what full scale pilots use in training - that is the intentional idling of an engine to simulate the engine's failure. The step up that this system would offer from previous systems (mostly home-made) is in the not knowing which engine is going to be simulated as a dead engine. This calls for the pilot to read the airplane and take the corrective action to remain in control. Other advantages are that it's effectively plug-n-play and the system can stay in the plane by simply switching it off and all is back to normal, making training a flight by flight choice for the pilot.
For example, if you were to practice critical engine-out on climb out (left engine on most planes) you be conditioned to apply right rudder as needed. If your main clue than an engine failure had occurred was by a sound/pitch change and you "knew" it was the left engine, you will tend to react without 'reading' the plane's attitude. Learning to read which engine is out is critical to making the right control inputs. Since you won't know which engine has failed (but you will know when) you would be forced to read the airplane and determine which inputs to use. Practice at altitude is now possible allowing for a chance to make mistakes, recover and try again.
I understand this can look like adding something to an airplane that makes any pilot uncomfortable. Consider the alternative to not having the right experience at the right time on the $1000+ twin. You'll have control over when (but not which) engine is going to idle. Once you are satisfied you can handle an engine out situation, pass the ATT off to one of your friends (they probably need this training too).
BTW, the automatic yaw correction works so good, it was hard not to put it on the market. It's so fast AND it continues to correct for an indefinite period of time (unlike many gyro solutions) and at what ever degree is needed - totally hands-off the rudder if you want. If not for the engine tone/sound change and a loss in engine performance (climb and speed) you'd be hard pressed to know you had an engine out. It works on the same principle as the slip/skid indicator in a full scale airplane (ball in the tube). It simply 'looks' at the 'ball' and applies enough rudder to recenter the ball. Works for normal flight to stop yaw and is cool when an engine fails. The reason we haven't gone to market is that we are trying to come up with a failsafe way of addressing two adverse conditions. The first is inverted or negative G flight (even negative G's from a hard push-over). This is causing some problems in code and we think we will resolve the issue, but we are not grounded on one solution just yet. The other is ground operations where lateral forces don't necessarily involve a yawing motion. Both these issues could be overcome with the use of an axillary channel to control on/off, but this was not seen as a popular solution. Everyone we spoke to said they wanted it on and running (no fiddling with switches) or they wouldn't be interested in it. The Hamster (as it's known) has been used very well in sailplanes where yaw control pays big dividends in competitive environments. You can check another popular web site R C G (sorry, RCU will change its name if I use it) and search for Hamster Automatic Yaw Correction to see the development thread. Much of the thread revolves around debate of the logic and sensors, both of which are well addressed in real world tests.
For example, if you were to practice critical engine-out on climb out (left engine on most planes) you be conditioned to apply right rudder as needed. If your main clue than an engine failure had occurred was by a sound/pitch change and you "knew" it was the left engine, you will tend to react without 'reading' the plane's attitude. Learning to read which engine is out is critical to making the right control inputs. Since you won't know which engine has failed (but you will know when) you would be forced to read the airplane and determine which inputs to use. Practice at altitude is now possible allowing for a chance to make mistakes, recover and try again.
I understand this can look like adding something to an airplane that makes any pilot uncomfortable. Consider the alternative to not having the right experience at the right time on the $1000+ twin. You'll have control over when (but not which) engine is going to idle. Once you are satisfied you can handle an engine out situation, pass the ATT off to one of your friends (they probably need this training too).
BTW, the automatic yaw correction works so good, it was hard not to put it on the market. It's so fast AND it continues to correct for an indefinite period of time (unlike many gyro solutions) and at what ever degree is needed - totally hands-off the rudder if you want. If not for the engine tone/sound change and a loss in engine performance (climb and speed) you'd be hard pressed to know you had an engine out. It works on the same principle as the slip/skid indicator in a full scale airplane (ball in the tube). It simply 'looks' at the 'ball' and applies enough rudder to recenter the ball. Works for normal flight to stop yaw and is cool when an engine fails. The reason we haven't gone to market is that we are trying to come up with a failsafe way of addressing two adverse conditions. The first is inverted or negative G flight (even negative G's from a hard push-over). This is causing some problems in code and we think we will resolve the issue, but we are not grounded on one solution just yet. The other is ground operations where lateral forces don't necessarily involve a yawing motion. Both these issues could be overcome with the use of an axillary channel to control on/off, but this was not seen as a popular solution. Everyone we spoke to said they wanted it on and running (no fiddling with switches) or they wouldn't be interested in it. The Hamster (as it's known) has been used very well in sailplanes where yaw control pays big dividends in competitive environments. You can check another popular web site R C G (sorry, RCU will change its name if I use it) and search for Hamster Automatic Yaw Correction to see the development thread. Much of the thread revolves around debate of the logic and sensors, both of which are well addressed in real world tests.
04-09-2007, 04:52 PM
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RE: Multi Engine-Out Training Device
Gary,
Please explain what and how "automatic yaw correction " works..
All your explaination in above post describe just about throttle management
and not how the automatic yaw correction is attached or works.. Just that it does..
Please explain what and how "automatic yaw correction " works..
All your explaination in above post describe just about throttle management
and not how the automatic yaw correction is attached or works.. Just that it does..
Left_Seat :
continues to correct for an indefinite period of time (unlike many gyro solutions) and at what ever degree is needed - totally hands-off the rudder if you want. If not for the engine tone/sound change and a loss in engine performance (climb and speed) you'd be hard pressed to know you had an engine out.
continues to correct for an indefinite period of time (unlike many gyro solutions) and at what ever degree is needed - totally hands-off the rudder if you want. If not for the engine tone/sound change and a loss in engine performance (climb and speed) you'd be hard pressed to know you had an engine out.
04-09-2007, 05:07 PM
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RE: Multi Engine-Out Training Device
I think we crossed each other's posts, but I'll explain a bit more here. It uses a 2 axis accelerometer to read both lateral and vertical perceived gravity. It originally used only one axis (lateral) but the addition (or reduction) in perceived gravity (pulling G's with the elevator WHILE in a slip/skid) caused some errors. We found a way to incorporate vertical G forces to offset the effects of using lateral G's alone (simple geometry solution - not so simple in code).
In operation, when a slip or skid is sensed (lateral errors) the rudder is moved to correct for those forces. This is exactly what a slip/skid ball-in-the-tube does on full scale airplanes. As a full scale pilot does, in the even of a slip/skid condition he simply 'steps' on the ball with rudder input to recenter the ball, varying the amount as needed to keep the ball centered. The Hamster does just that. As an RC pilot, you still have full control over the rudder and it 'feels' like you have normal rudder control, but in reality, the rudder stick is simply setting the amount of slid/skid you want the airplane to fly at. The Hamster does what ever is necessary to maintain that slip/skid attitude, including no slip/skid settings (center stick rudder input). It's a real work-load reducer for sailplanes, regular planes (non-aerobatic in scale like flight) and twins with an engine out.
In operation, when a slip or skid is sensed (lateral errors) the rudder is moved to correct for those forces. This is exactly what a slip/skid ball-in-the-tube does on full scale airplanes. As a full scale pilot does, in the even of a slip/skid condition he simply 'steps' on the ball with rudder input to recenter the ball, varying the amount as needed to keep the ball centered. The Hamster does just that. As an RC pilot, you still have full control over the rudder and it 'feels' like you have normal rudder control, but in reality, the rudder stick is simply setting the amount of slid/skid you want the airplane to fly at. The Hamster does what ever is necessary to maintain that slip/skid attitude, including no slip/skid settings (center stick rudder input). It's a real work-load reducer for sailplanes, regular planes (non-aerobatic in scale like flight) and twins with an engine out.
04-09-2007, 05:17 PM
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RE: Multi Engine-Out Training Device
Ok..
So there would have to be one plug in to RX for throttle management,
then another plug in to the RX for the rudder accelerometer and yet
another plug in for the elevator accelerometer .... (?)
So there would have to be one plug in to RX for throttle management,
then another plug in to the RX for the rudder accelerometer and yet
another plug in for the elevator accelerometer .... (?)
04-09-2007, 05:25 PM
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RE: Multi Engine-Out Training Device
Whoops, no. Your mixing the explanations of two products.
The Hamster (automatic yaw correction) uses the Rudder channel and an Aux channel (Aux is for on/off). The 2 axis of the accelerometer are dealt with on the Hamster PCB and have no external connection. edit: The rudder itself is driven from the Hamster. In the off position the rudder just passes through the Hamster with no accelerometer correction.
The ATT (Advanced Twin Trainer) uses the Throttle channel(s) (1 or 2 inputs depending on if you drive the throttle servos with one channel or two) and an Aux channel (activates the ATT or shuts off the ATT).
The Hamster (automatic yaw correction) uses the Rudder channel and an Aux channel (Aux is for on/off). The 2 axis of the accelerometer are dealt with on the Hamster PCB and have no external connection. edit: The rudder itself is driven from the Hamster. In the off position the rudder just passes through the Hamster with no accelerometer correction.
The ATT (Advanced Twin Trainer) uses the Throttle channel(s) (1 or 2 inputs depending on if you drive the throttle servos with one channel or two) and an Aux channel (activates the ATT or shuts off the ATT).
04-09-2007, 06:18 PM
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RE: Multi Engine-Out Training Device
okkayyy..
Lets make a four channel plane..
1-aileron
2-elevator
3-rudder
4-throttle... L&R throttle servo..
Single servo per control, except throttle which has two, left and right..
7channel TX/ 7port RX as a 7C FUT with a 127D Reciever...
Where does what go and how many devices are being plugged in...............................................
Lets make a four channel plane..
1-aileron
2-elevator
3-rudder
4-throttle... L&R throttle servo..
Single servo per control, except throttle which has two, left and right..
7channel TX/ 7port RX as a 7C FUT with a 127D Reciever...
Where does what go and how many devices are being plugged in...............................................
04-09-2007, 06:35 PM
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RE: Multi Engine-Out Training Device
First, understand BOTH device would not be used on the same plane at the same time. ATT is for training you to handle one engine out conditions and the Hamster would automatically handle one engine out conditions. Both are an attempt to handle the pearls of an engine out conditions. The ATT teaches YOU to handle the engine out, the Hamster handles the engine out WITHOUT YOU.
The ATT and the Hamster requires only the addition of one unused channel space on the receiver - the channel used for Aux (gear, flaps, spoilers... any unused channel you can tie to a switch or knob). The ATT will use the engine throttle servo channels and then send those servo commands from the ATT to the throttle servos. The Hamster will use the rudder servo channel and then send those servo commands from the Hamster to the rudder servo.
So, the only additional connections (extra channel ports used) is to the AUX channel, used for on/off control.
BTW, as mentioned before, we are trying to come up with a Hamster that will run full-time and not need an AUX channel to turn it on or off - but that is still in the works. Using the ATT without an AUX channel input would not make any sense.
The ATT and the Hamster requires only the addition of one unused channel space on the receiver - the channel used for Aux (gear, flaps, spoilers... any unused channel you can tie to a switch or knob). The ATT will use the engine throttle servo channels and then send those servo commands from the ATT to the throttle servos. The Hamster will use the rudder servo channel and then send those servo commands from the Hamster to the rudder servo.
So, the only additional connections (extra channel ports used) is to the AUX channel, used for on/off control.
BTW, as mentioned before, we are trying to come up with a Hamster that will run full-time and not need an AUX channel to turn it on or off - but that is still in the works. Using the ATT without an AUX channel input would not make any sense.
04-09-2007, 07:14 PM
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RE: Multi Engine-Out Training Device
Interesting concept but seems to be very complicated based on the attempts to explain it. (Which I lost interest in reading after the first few sentences.)
I have "trained" for engine outs by just filling one of my tanks half or less full, then fly around and wait until the engine dies and go for it. That seems to be similarly predictable to being able to throw a switch and turn the engine on and off. Once you have the plane under control it can be managable it is the first few seconds after you lose the engine that make all the difference.
In my experience with twins there is nothing you can do to prepare for an engine out immediately after rotation. The best position to be in is lots of air speed and plenty of altitude to get back to the field. Without those two things you have the Reynolds numbers working against you and things happen so fast there is little you can do but grab a bag and go pick up the pieces.
I have "trained" for engine outs by just filling one of my tanks half or less full, then fly around and wait until the engine dies and go for it. That seems to be similarly predictable to being able to throw a switch and turn the engine on and off. Once you have the plane under control it can be managable it is the first few seconds after you lose the engine that make all the difference.
In my experience with twins there is nothing you can do to prepare for an engine out immediately after rotation. The best position to be in is lots of air speed and plenty of altitude to get back to the field. Without those two things you have the Reynolds numbers working against you and things happen so fast there is little you can do but grab a bag and go pick up the pieces.
04-09-2007, 08:02 PM
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RE: Multi Engine-Out Training Device
Left_Seat,
I understand what you mean, its hard to understand when you are only piloting model planes and have no knowledge of how its done on real planes. I am currently building Super Constellation's model and i like the idea of having Hamster device on board my model just in case i lose one of the outer engines #1 or #4 engines this device automatically kicks in and take over the "YAW" of the model and keep it in controlled flight manner. I have have smaller .25sz B-25 that actually is the base of going into multi engined model, i have flown it many times last year and had 1 engine out crash in which outer wings were damaged, since then i have learned how to control engine out situation on this model and what symptoms i get that tells me when one of the engine has dead sticked while in flight. Basically what i do when this happens i either keep the throttle in same throttle position or bring it to 1/4 throttle setting position of my TX's stick. this way i still have some power to keep the model flying while bit of rudder is inputted or not even while bringing in model to land.
I really like your ATT device idea also to train twin model pilots with out actually dead sticking both engine in engine out situations and this also leave them with power back option once they have learned how to handle engine out conditions.
When will your product be readily available and what type of costs are we looking at?.
I understand what you mean, its hard to understand when you are only piloting model planes and have no knowledge of how its done on real planes. I am currently building Super Constellation's model and i like the idea of having Hamster device on board my model just in case i lose one of the outer engines #1 or #4 engines this device automatically kicks in and take over the "YAW" of the model and keep it in controlled flight manner. I have have smaller .25sz B-25 that actually is the base of going into multi engined model, i have flown it many times last year and had 1 engine out crash in which outer wings were damaged, since then i have learned how to control engine out situation on this model and what symptoms i get that tells me when one of the engine has dead sticked while in flight. Basically what i do when this happens i either keep the throttle in same throttle position or bring it to 1/4 throttle setting position of my TX's stick. this way i still have some power to keep the model flying while bit of rudder is inputted or not even while bringing in model to land.
I really like your ATT device idea also to train twin model pilots with out actually dead sticking both engine in engine out situations and this also leave them with power back option once they have learned how to handle engine out conditions.
When will your product be readily available and what type of costs are we looking at?.
04-10-2007, 02:08 AM
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RE: Multi Engine-Out Training Device
The Hamster idea sounds like a great idea..
The throttle management idea is a good idea and is already being done as noted prior..
Minor 'however' here tho... The Hamster idea will not work in smaller sport planes....
In full scale this works by mass working to reduce yaw time... I suppose in a giant scale
it may be of a help as well... Mass being the weight and size of the plane in porportion to
the amount of power and thrust being produced...
In most sport planes there is not enough mass to allow the required time for the Hamster
to activate the control surface in time to prevent a radical yaw... As in:
70" w/s sport plane, two .60 size motors.. Approx power to weight ratio of three to one..
Upon take off to approx 25' at approx 50 degree climb out,, motor quits... The Hamster
will need to recognize the sudden adverse action, which by the time it has, it has made
the required control surface correction.. However,, TOO LATE... The plane being over
powered and the plane weight being light enough the plane has already rotated into
a bad position... Now without the throttle management to do auto reduce on running
motor has made this even less effective.. So plane rotates, operator fails to reduce the
power, hamster trys to correct, won't happen... Physics will not allow it..
This would apply to most sport plane operators, which is who would likely be the bulk
of consumer for the product, would fail to reduce power unless they have the known skills..
In model planes before venturing into multi engined planes, especially twins, one
should ingrain into their brain, Loose motor, Loose throttle (lower TX stick) .. This will
allow most people time to comprehend required corrective action..
And then, there is another 'however'... As in:
Plane DOES have Hamster device, and does remember to lower TX stick, the Hamster
device does correct, 'however', person has already started corrective measures there
by over riding the unit... So now control is still loss by over reaction of device and operator..
Gary.. Please understand.. I am not trying to squelch your idea.. More so to enlighten you
to the things to which you will need to address in going to market with these products..
What I might suggest is for you to get a 9 channel radio and channel each motor
seperately so that one can be killed at ANY time.. And get yourself a .40/.60 sport
plane and install a Hamster device to do some test with..
Even with the use of gyros on multiple control surfaces that only slows down the
radical rotate but STILL requires operator knowledge/skill.. And in a .40/60 sport
plane,, welll,, is about usueless as adverse yaw on an over powered plane happens
way too fast for any mechincal compensation to adequetly correct..
The throttle management idea is a good idea and is already being done as noted prior..
Minor 'however' here tho... The Hamster idea will not work in smaller sport planes....
In full scale this works by mass working to reduce yaw time... I suppose in a giant scale
it may be of a help as well... Mass being the weight and size of the plane in porportion to
the amount of power and thrust being produced...
In most sport planes there is not enough mass to allow the required time for the Hamster
to activate the control surface in time to prevent a radical yaw... As in:
70" w/s sport plane, two .60 size motors.. Approx power to weight ratio of three to one..
Upon take off to approx 25' at approx 50 degree climb out,, motor quits... The Hamster
will need to recognize the sudden adverse action, which by the time it has, it has made
the required control surface correction.. However,, TOO LATE... The plane being over
powered and the plane weight being light enough the plane has already rotated into
a bad position... Now without the throttle management to do auto reduce on running
motor has made this even less effective.. So plane rotates, operator fails to reduce the
power, hamster trys to correct, won't happen... Physics will not allow it..
This would apply to most sport plane operators, which is who would likely be the bulk
of consumer for the product, would fail to reduce power unless they have the known skills..
In model planes before venturing into multi engined planes, especially twins, one
should ingrain into their brain, Loose motor, Loose throttle (lower TX stick) .. This will
allow most people time to comprehend required corrective action..
And then, there is another 'however'... As in:
Plane DOES have Hamster device, and does remember to lower TX stick, the Hamster
device does correct, 'however', person has already started corrective measures there
by over riding the unit... So now control is still loss by over reaction of device and operator..
Gary.. Please understand.. I am not trying to squelch your idea.. More so to enlighten you
to the things to which you will need to address in going to market with these products..
What I might suggest is for you to get a 9 channel radio and channel each motor
seperately so that one can be killed at ANY time.. And get yourself a .40/.60 sport
plane and install a Hamster device to do some test with..
Even with the use of gyros on multiple control surfaces that only slows down the
radical rotate but STILL requires operator knowledge/skill.. And in a .40/60 sport
plane,, welll,, is about usueless as adverse yaw on an over powered plane happens
way too fast for any mechincal compensation to adequetly correct..
04-10-2007, 07:30 AM
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RE: Multi Engine-Out Training Device
It doesn't matter if it's a model or full scale twin, if the aircraft is operated below VMC (minimum single control speed), or the speed which the rudder can no longer maintain yaw control, the aircraft IS going to roll over and you WILL lose control. Below VMC, no electrical or mechanical device will save the aircraft. The only recourse you have is to reduce power immediately! Speed management is a must!
Full scale aircraft DO NOT operate below VMC...EVER! Some corperate twins may seem to have an exceptionally long take-off roll, but they forced to stay on the ground until VMC is attained. Only then will the aircraft rotate. It's the same with lading approach. You maintain VMC until over the threshold and the throttles are reduced, only then you can slow below VMC to flare for landing.
Models high power to weight ratio makes it even more difficult. There is also a lot less distance between the model and the ground. Things happen fast. I also fly helis and the gyros are fast enough to keep the heli's tail pointed into the wind during fast backward flight, but on a twin airplane, it will only work to the point it reaches VMC.
I think education is the best thing a pilot can do. Learn the physics of twin operation and why they do what they do and most important, what to do in an engine out situation. Practicing engine outs on a simulator helps to without risking a model.
BTW, I am multi-engine rated...since 1976.
Rod
Full scale aircraft DO NOT operate below VMC...EVER! Some corperate twins may seem to have an exceptionally long take-off roll, but they forced to stay on the ground until VMC is attained. Only then will the aircraft rotate. It's the same with lading approach. You maintain VMC until over the threshold and the throttles are reduced, only then you can slow below VMC to flare for landing.
Models high power to weight ratio makes it even more difficult. There is also a lot less distance between the model and the ground. Things happen fast. I also fly helis and the gyros are fast enough to keep the heli's tail pointed into the wind during fast backward flight, but on a twin airplane, it will only work to the point it reaches VMC.
I think education is the best thing a pilot can do. Learn the physics of twin operation and why they do what they do and most important, what to do in an engine out situation. Practicing engine outs on a simulator helps to without risking a model.
BTW, I am multi-engine rated...since 1976.
Rod
04-10-2007, 09:23 AM
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RE: Multi Engine-Out Training Device
Robby, I don't understand the:
"In full scale this works by mass working to reduce yaw time... I suppose in a giant scale
it may be of a help as well... Mass being the weight and size of the plane in proportion to
the amount of power and thrust being produced..."
A slip is a slip, a skid is a skid. It makes no mind what the size, mass or power is. It's easy to detect lateral acceleration in any airplane using accelerometers. I think you are assuming that the Hamster applies 'full rudder' to correct a slip or skid. It's much more involved than that. It's amount of correction is in direct correlation with the amount of slip/skid. It assess the error and applies correction 50 times a second. Now, the gain of the Hamster is adjustable to suit different airplanes. It comes programmed at gain "3" out of a possible 6 levels of gain (user programmable using their transmitter, in the field).
The Hamster is working quite well in a hand launch glider which weighs about 10 ounces and flies at about 12-14 MPH. The hamster has flown on a .40 powered Avistar trainer (I think that's the name). It's flown on a Turbo Porter (94" WS, E-powered) and on at Twin Star ARF (again, I think that's the name) twin on .40 engines. The Hamster has also flown in an Eraser, Falcon and a Physco (competition sailplanes). The Hamster works - sorry, but size and mass have little to do with it's operation other than gain, which is adjustable.
When I say the Hamster addresses the engine out situation, I don't mean you can put the transmitter down and go have have a Coke. Airspeed management and attitude control are required on the pilot's part. So is yaw and power. The Hamster allows for power to remain high and yaw to be corrected, reducing the workload for the pilot.
I often hear that the 'best' action with an engine out situation is to reduce power. Mr Heli_rod should know (multi pilot) that engine out conditions in anything other than descending flight dictate the application of additional power from the remaining engine. Reducing power is only acceptable if you don't have control of the yaw.
What is this product that does does what the ATT does?
"In full scale this works by mass working to reduce yaw time... I suppose in a giant scale
it may be of a help as well... Mass being the weight and size of the plane in proportion to
the amount of power and thrust being produced..."
A slip is a slip, a skid is a skid. It makes no mind what the size, mass or power is. It's easy to detect lateral acceleration in any airplane using accelerometers. I think you are assuming that the Hamster applies 'full rudder' to correct a slip or skid. It's much more involved than that. It's amount of correction is in direct correlation with the amount of slip/skid. It assess the error and applies correction 50 times a second. Now, the gain of the Hamster is adjustable to suit different airplanes. It comes programmed at gain "3" out of a possible 6 levels of gain (user programmable using their transmitter, in the field).
The Hamster is working quite well in a hand launch glider which weighs about 10 ounces and flies at about 12-14 MPH. The hamster has flown on a .40 powered Avistar trainer (I think that's the name). It's flown on a Turbo Porter (94" WS, E-powered) and on at Twin Star ARF (again, I think that's the name) twin on .40 engines. The Hamster has also flown in an Eraser, Falcon and a Physco (competition sailplanes). The Hamster works - sorry, but size and mass have little to do with it's operation other than gain, which is adjustable.
When I say the Hamster addresses the engine out situation, I don't mean you can put the transmitter down and go have have a Coke. Airspeed management and attitude control are required on the pilot's part. So is yaw and power. The Hamster allows for power to remain high and yaw to be corrected, reducing the workload for the pilot.
I often hear that the 'best' action with an engine out situation is to reduce power. Mr Heli_rod should know (multi pilot) that engine out conditions in anything other than descending flight dictate the application of additional power from the remaining engine. Reducing power is only acceptable if you don't have control of the yaw.
What is this product that does does what the ATT does?
04-10-2007, 10:03 AM
#18
Senior Member
RE: Multi Engine-Out Training Device
Your efforts to make twin flying safer and less damaging to the airplane are applauded. Engine out practice is mandatory and cannot be learned in real-time. No one I know practices engine out. Also there is an entire group of people discussing the Cessna 310 who apparently believe that engines don’t shut down.
However except for random engine dropping the same techniques can be programmed into a computer radio and it is the method that I use to practice.
Those without a computer radio might benefit and some may prefer the convenience of purchase rather than programming.
I would prefer to see a system of engine out alert, which probably requires transmission from the airplane. The small delay in recognizing an engine out is where the crash begins.
Bill
However except for random engine dropping the same techniques can be programmed into a computer radio and it is the method that I use to practice.
Those without a computer radio might benefit and some may prefer the convenience of purchase rather than programming.
I would prefer to see a system of engine out alert, which probably requires transmission from the airplane. The small delay in recognizing an engine out is where the crash begins.
Bill
04-10-2007, 01:11 PM
#19
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RE: Multi Engine-Out Training Device
Where Rod is correct that all full scale and even SOME models require VMC to be attained, not all models
do.. Again.. an over powered plane will be capable of going into the air and not attain control speed..
Control is attained by motor thrust..
Now, if weight and mass are not a consideration then look up what VMC is:
http://selair.selkirk.bc.ca/aerodyna...lti/Page4.html
And again, most models have more than a 1:1 power to weight ratio..
If VMC were required then 3D would not exist..
All of the planes you mentioned including the Twinstar would probably react decent with your product..
However, if I were to use something as pictured, which is capable of going into the air without obtaining
full control flight speed and a motor quits, that plane IS going to rotate and your device is not going
to save it.. Period... Your use of a sailplane even at a slow speed and even if sailplane is underweight
the mass of that plane will inhibit a fast enough rotate<yaw> to loose control...
So, sorry to you, your examples aren't the best choice for testing your product.. The Twinstar is the
closest plane to be a decent choice of your product but the design of the plane itself is helping the
device to work..
I will again suggest.. Use any sport plane, not a trainer plane or sailplane, overpower it, then see
how your device works...
For me to make a purchase of your product I would want a FULL replacement guarantee and I know
you nor anyone else would be foolish enough to do such, so I would decline to make the purchase
because I know it will not work as described in most sport planes, or most smaller twin warbirds..
And there is currently already a product on the market that does do throttle management and
makes it known to the TX operator that a motor has quit and can operate faster than then equipment
we use in our model airplanes called the Twin Sync :
http://www.rcshowcase.com/html/acces.../twinsync.html
And as mentioned prior the Twin Sync offers additional usefull options to our models..
Given my example of a 70" sport plane with a couple .60 size motors doing about a
50 degree takeoff having a motor quit at about 25' altitude your device would fail to
be able to make required corrective measures to save plane... In this example the
closest viable thing is to greatly reduce other motor, point nose down, not trying to
make a turn, and manually correct as best as operator can.. I will however concede
that the probability of decent functionality of your product to a scale plane being flown
in a scale manner.. But still, if the running motor is not reduced then there is no, zero,
chance of corrective control..
(edit)
BTW, Gary, again, don't take this as me trying to burst your bubble on this project
as I do appluad you on trying to produce a product to enhance multi model flying..
As noted by another in this thread, "education is the best thing a pilot can do.
Learn the physics of twin operation " More explicitly, learn the physics of
your own twin as there are wayy toooo many varables in design within the
R/C model hobby..
do.. Again.. an over powered plane will be capable of going into the air and not attain control speed..
Control is attained by motor thrust..
Now, if weight and mass are not a consideration then look up what VMC is:
http://selair.selkirk.bc.ca/aerodyna...lti/Page4.html
And again, most models have more than a 1:1 power to weight ratio..
If VMC were required then 3D would not exist..
All of the planes you mentioned including the Twinstar would probably react decent with your product..
However, if I were to use something as pictured, which is capable of going into the air without obtaining
full control flight speed and a motor quits, that plane IS going to rotate and your device is not going
to save it.. Period... Your use of a sailplane even at a slow speed and even if sailplane is underweight
the mass of that plane will inhibit a fast enough rotate<yaw> to loose control...
So, sorry to you, your examples aren't the best choice for testing your product.. The Twinstar is the
closest plane to be a decent choice of your product but the design of the plane itself is helping the
device to work..
I will again suggest.. Use any sport plane, not a trainer plane or sailplane, overpower it, then see
how your device works...
For me to make a purchase of your product I would want a FULL replacement guarantee and I know
you nor anyone else would be foolish enough to do such, so I would decline to make the purchase
because I know it will not work as described in most sport planes, or most smaller twin warbirds..
And there is currently already a product on the market that does do throttle management and
makes it known to the TX operator that a motor has quit and can operate faster than then equipment
we use in our model airplanes called the Twin Sync :
http://www.rcshowcase.com/html/acces.../twinsync.html
And as mentioned prior the Twin Sync offers additional usefull options to our models..
Given my example of a 70" sport plane with a couple .60 size motors doing about a
50 degree takeoff having a motor quit at about 25' altitude your device would fail to
be able to make required corrective measures to save plane... In this example the
closest viable thing is to greatly reduce other motor, point nose down, not trying to
make a turn, and manually correct as best as operator can.. I will however concede
that the probability of decent functionality of your product to a scale plane being flown
in a scale manner.. But still, if the running motor is not reduced then there is no, zero,
chance of corrective control..
(edit)
BTW, Gary, again, don't take this as me trying to burst your bubble on this project
as I do appluad you on trying to produce a product to enhance multi model flying..
As noted by another in this thread, "education is the best thing a pilot can do.
Learn the physics of twin operation " More explicitly, learn the physics of
your own twin as there are wayy toooo many varables in design within the
R/C model hobby..
04-10-2007, 02:00 PM
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RE: Multi Engine-Out Training Device
These are Quotes from the manual that I used for my Multi-engine rating. "MULTIENGINE AIRPLANE RATING" by: T.M. Smith, 3rd. revision A Zweng Manual.
VMC as relating to mulit-engine aricraft has NOTHING to do with 3-D flying!
Sign me up for one of those , Left_Seat, I'd like to give it a try!
Rod
--------------------------------------------------------------------------------
heli_Rod
(edit)
I accedently wrote over his post by hitting wrong button,, Sorry, Rod, didn't mean to..
Has been put back to original..
Robby
VMC as related to multi-engine aircraft refers to "Minimum SINGLE engine control" speed. That is the engine out minimum control speed which your aircraft: The airspeed below which the airplane cannot be controlled in flight with one engine operating at full power.
A multi-engine pilot must know and observe this minimum control speed. Any attempt to continue flight on one engine at a lower speed will result in a loss of control and probable crash.
In the event of a sudden engine failure at an airspeed below the engine-out minimum control speed, the operating engine must be throttled immediately to a point at which flight control can be maintained.
Sign me up for one of those , Left_Seat, I'd like to give it a try!
Rod
--------------------------------------------------------------------------------
heli_Rod
(edit)
I accedently wrote over his post by hitting wrong button,, Sorry, Rod, didn't mean to..
Has been put back to original..
Robby
04-10-2007, 02:45 PM
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RE: Multi Engine-Out Training Device
Uhm,, yeah,,, ok.. you go ahead and throttle up a VQ P-38 after takeoff when a motor dies..
I wanna watch...
You are correct,, VMC does not apply to 3D flying.. But then,, we all know,, NO one flys any
type of model, not even a twin, on the props...
Trying to equate full scale planes to model planes has never worked,, never will..
If it did,, then a full scale Extra 300 weight scaled down to a quater scale would mean
that a quarter scale Extra 300 would weigh 500# ... And again,, I wanna watch...
Rod,, your statement would be correct if you had stated:
VMC as relating to FULL SCALE mulit-engine aricraft has NOTHING to do with 3-D flying!
Trying to equate full scale flying to model plane flying is,, well, like the proverbial comparsion
of oranges and apples...
Gyros, accleometers, and other devices have been tryed and have never work as of yet
on model airplanes,, especially sport planes... Knowledge and skill have always won this
debate..
I wanna watch...
You are correct,, VMC does not apply to 3D flying.. But then,, we all know,, NO one flys any
type of model, not even a twin, on the props...
Trying to equate full scale planes to model planes has never worked,, never will..
If it did,, then a full scale Extra 300 weight scaled down to a quater scale would mean
that a quarter scale Extra 300 would weigh 500# ... And again,, I wanna watch...
Rod,, your statement would be correct if you had stated:
VMC as relating to FULL SCALE mulit-engine aricraft has NOTHING to do with 3-D flying!
Trying to equate full scale flying to model plane flying is,, well, like the proverbial comparsion
of oranges and apples...
Gyros, accleometers, and other devices have been tryed and have never work as of yet
on model airplanes,, especially sport planes... Knowledge and skill have always won this
debate..
:
In the event of a sudden engine failure at an airspeed below the engine-out minimum control speed, the operating engine must be throttled immediately to a point at which flight control can be maintained.
In the event of a sudden engine failure at an airspeed below the engine-out minimum control speed, the operating engine must be throttled immediately to a point at which flight control can be maintained.
VMC as relating to mulit-engine aricraft has NOTHING to do with 3-D flying!
04-10-2007, 07:33 PM
#22
RE: Multi Engine-Out Training Device
I just posted a short clip of a Duellist losing an engine in flight. Sorry for the poor quality but it was a VHS clip from '99.
Duayne P from the Guam Aeromodelers, taught me how to fly and got me hooked on twins!!
Check it out in the Members Videos section titled "Duellist Engine Out."
The plane is powered by a pair of TT Pro 46, I don't remember how much it weighed.
Other than a momentary wiggle the pilot kept the plane under control. You will notice that he did not immediately throttle back and land...not an option going near full speed and just crossing the runway threshold about 20' off the ground. He maintains full throttle and flies twice around the pattern before landing.
Duayne P from the Guam Aeromodelers, taught me how to fly and got me hooked on twins!!
Check it out in the Members Videos section titled "Duellist Engine Out."
The plane is powered by a pair of TT Pro 46, I don't remember how much it weighed.
Other than a momentary wiggle the pilot kept the plane under control. You will notice that he did not immediately throttle back and land...not an option going near full speed and just crossing the runway threshold about 20' off the ground. He maintains full throttle and flies twice around the pattern before landing.
04-10-2007, 08:45 PM
#23
RE: Multi Engine-Out Training Device
Duayne, Guam, Duellist... been there done that, I had a Duellist on Guam back in the late '80's. Duayne was a kid then, guess it left an impression. Last I saw him was here in NC when he was in the Army... that was in the late '90's, 98 or so.
Small world...
Small world...
04-11-2007, 11:54 AM
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RE: Multi Engine-Out Training Device
Hi guys,
Sorry about my absence yesterday. I had a full day of in-home repairs (TV repair pays the 'real' bills).
While I've got the attention of a few interested fliers about the Hamster (accelerometer yaw correction) I'd like to share with you the problems we have in getting this in the twin (or even single) engine powered market.
First, you have to understand what it does and I think I explained it quite well in earlier posts in this thread. To recap, it simply takes a look at the lateral acceleration forces (forces aligned in the direction of the wingspan - aligned wing tip to wing tip) and attempts to keep those forces as close to neutral as possible. Though yaw acceleration forces and air stream yaw are not exactly the same thing, they are very close cousins and it's the yaw acceleration forces that 90% of full scale airplanes use to make sure the airplane is aligned strait into the relative air stream. With a OEO (one engine out) on a twin, yaw is introduced for a number of reasons if nothing is done to stop it. Yaw in itself is not that detrimental to successful flight, but it does setup an unsafe condition in the even of a stall. A stall entered in a slip/skid condition usually evolves into a spin if the stall condition is maintained. It's this stall-to-spin flight attitude that causes biggest concern of twin RC pilots. Most of us can 'see' or 'feel' if an RC plane is flying too slow and know to reduce the angle of attack to avoid entering a stall. In a OEO condition we can very easily allow airspeed to come dangerously close to a stall because of our wanting to maintain a given pitch attitude (normal pitch attitude) for any given maneuver. Seems that RC pilots use pitch attitude more than the speed of the model to account for air speed performance - that's natural since sight is our only feedback we get for performance standards.
Now with that little bit out of the way, here's what's causing problems for us: It's the action/reaction of the Hamster on the ground and in negative G maneuvers. We would like the Hamster to be installed between the rudder channel on the receiver and the rudder servo and left to do it's job without any other input or interaction. But in both of the examples given the Hamster would cause undesirable effects.
On the ground, lateral forces happen every time the nose moves along the yaw axis. This in itself would not be a big issue if it were not true that most of us build our planes using the rudder channel to drive both the nose wheels in trikes, and of course, the same it true for a tail dragger. When we first tried using the Hamster on the ground we were not in agreement as to what the reaction of the Hamster would be. I predicted a smooth dampened effect at low speeds, but that as speed increased it would oscillate uncontrollably. Others had their opinions too. I was right. Many of the takeoffs had to be aborted due to not tracking strait down the runway and any attempt to correct the heading would result in overshooting control. So, all tests were done using the remote arming switch and keeping the Hamster off for ground operations. This causes us to turn it on after liftoff. Not such a big problem if you are used to reaching for a gear switch, but as we found out this is a learned action to do smoothly, not to mention that an engine could have died before the Hamster was turned on.
In the air, the Hamster can stay on full-time so long as the airplane was flown in positive G scale-like maneuvers. The plane not only gets the benefit of OEO protection, but it also tracks in flight with complete coordination and doesn't need any input from transmitter mixing or rudder stick movement to do so. Scale planes look so much more real when they stay in coordinated flight. Now enter a pushover, outside loop or any maneuver that generates negative G's. The Hamster will respond in a way that is exactly backwards from the desired response. If things are done that result in negative G's without slip/skid things go well, but add any slip/skid acceleration and things become yaw unstable. We have come up with a code theory that would reverse the Hamster's response logic when the vertical axis reduces to less than 0 G's, but that has not been put into real code just yet. The reason the code hasn't been written yet is because of a lack in confidence that it would work as desired. It has to do with the fact that, in order to remove the vertical acceleration component of the lateral acceleration, we square the values of both vertical and lateral acceleration and use the square root of the sum of the two, to find a value that is to be adjusted to the lateral acceleration to remove the vertical component. In reversing the logic of the Hamster we are unsure and debating over which other math and data sets need to be reversed and/or adjusted. For example, the LUT (Look Up Table) used for the non-linear responce curve - does it need to have it's values corrected to intergrate into the math used to remove vertical acceleration? This is one of many such questions that we have.
Some solutions to the negative G flight condition are being entertained before moving into such mind numbing computer code. One solution that seems to be at the top of the list is to simply kill the Hamster automatically when negative G's are seen. It would work and it's easy to implement, but it's less then eloquent. I could see a turbulant, rough-air day with a lot of vertical movement on final approach - it's on, it's off, it's on, it's off...
Other solutions to the negative G's is to remove the vertical G math equation entirely when going negative and simply reverse the Hamster's output based on lateral acceleration alone, since processing the vertical acceleration causes the mathematical model to 'crash'. This brought up an interesting theory about the Hamster. If vertical acceleration is at 0G's, so would the lateral acceleration, even if the air stream was at a slip/skid presentation. This would allow for a slip/skid to go undetected and uncorrected.
In conclusion, the Hamster works as advertised in normal positive G's environments and fails otherwise, and for this reason we won't release it for sale. At the current time, it's only being sold for sailplanes on a limited bases to pilots who are truly interested in it's function and with full knowledge of it's shortcomings, like the negative G's and the winch launch phase of flight.
Ok, with all of that now explained, I'd be interested in hearing from anyone who has ideas on how to address these issues.
Sorry about my absence yesterday. I had a full day of in-home repairs (TV repair pays the 'real' bills).
While I've got the attention of a few interested fliers about the Hamster (accelerometer yaw correction) I'd like to share with you the problems we have in getting this in the twin (or even single) engine powered market.
First, you have to understand what it does and I think I explained it quite well in earlier posts in this thread. To recap, it simply takes a look at the lateral acceleration forces (forces aligned in the direction of the wingspan - aligned wing tip to wing tip) and attempts to keep those forces as close to neutral as possible. Though yaw acceleration forces and air stream yaw are not exactly the same thing, they are very close cousins and it's the yaw acceleration forces that 90% of full scale airplanes use to make sure the airplane is aligned strait into the relative air stream. With a OEO (one engine out) on a twin, yaw is introduced for a number of reasons if nothing is done to stop it. Yaw in itself is not that detrimental to successful flight, but it does setup an unsafe condition in the even of a stall. A stall entered in a slip/skid condition usually evolves into a spin if the stall condition is maintained. It's this stall-to-spin flight attitude that causes biggest concern of twin RC pilots. Most of us can 'see' or 'feel' if an RC plane is flying too slow and know to reduce the angle of attack to avoid entering a stall. In a OEO condition we can very easily allow airspeed to come dangerously close to a stall because of our wanting to maintain a given pitch attitude (normal pitch attitude) for any given maneuver. Seems that RC pilots use pitch attitude more than the speed of the model to account for air speed performance - that's natural since sight is our only feedback we get for performance standards.
Now with that little bit out of the way, here's what's causing problems for us: It's the action/reaction of the Hamster on the ground and in negative G maneuvers. We would like the Hamster to be installed between the rudder channel on the receiver and the rudder servo and left to do it's job without any other input or interaction. But in both of the examples given the Hamster would cause undesirable effects.
On the ground, lateral forces happen every time the nose moves along the yaw axis. This in itself would not be a big issue if it were not true that most of us build our planes using the rudder channel to drive both the nose wheels in trikes, and of course, the same it true for a tail dragger. When we first tried using the Hamster on the ground we were not in agreement as to what the reaction of the Hamster would be. I predicted a smooth dampened effect at low speeds, but that as speed increased it would oscillate uncontrollably. Others had their opinions too. I was right. Many of the takeoffs had to be aborted due to not tracking strait down the runway and any attempt to correct the heading would result in overshooting control. So, all tests were done using the remote arming switch and keeping the Hamster off for ground operations. This causes us to turn it on after liftoff. Not such a big problem if you are used to reaching for a gear switch, but as we found out this is a learned action to do smoothly, not to mention that an engine could have died before the Hamster was turned on.
In the air, the Hamster can stay on full-time so long as the airplane was flown in positive G scale-like maneuvers. The plane not only gets the benefit of OEO protection, but it also tracks in flight with complete coordination and doesn't need any input from transmitter mixing or rudder stick movement to do so. Scale planes look so much more real when they stay in coordinated flight. Now enter a pushover, outside loop or any maneuver that generates negative G's. The Hamster will respond in a way that is exactly backwards from the desired response. If things are done that result in negative G's without slip/skid things go well, but add any slip/skid acceleration and things become yaw unstable. We have come up with a code theory that would reverse the Hamster's response logic when the vertical axis reduces to less than 0 G's, but that has not been put into real code just yet. The reason the code hasn't been written yet is because of a lack in confidence that it would work as desired. It has to do with the fact that, in order to remove the vertical acceleration component of the lateral acceleration, we square the values of both vertical and lateral acceleration and use the square root of the sum of the two, to find a value that is to be adjusted to the lateral acceleration to remove the vertical component. In reversing the logic of the Hamster we are unsure and debating over which other math and data sets need to be reversed and/or adjusted. For example, the LUT (Look Up Table) used for the non-linear responce curve - does it need to have it's values corrected to intergrate into the math used to remove vertical acceleration? This is one of many such questions that we have.
Some solutions to the negative G flight condition are being entertained before moving into such mind numbing computer code. One solution that seems to be at the top of the list is to simply kill the Hamster automatically when negative G's are seen. It would work and it's easy to implement, but it's less then eloquent. I could see a turbulant, rough-air day with a lot of vertical movement on final approach - it's on, it's off, it's on, it's off...
Other solutions to the negative G's is to remove the vertical G math equation entirely when going negative and simply reverse the Hamster's output based on lateral acceleration alone, since processing the vertical acceleration causes the mathematical model to 'crash'. This brought up an interesting theory about the Hamster. If vertical acceleration is at 0G's, so would the lateral acceleration, even if the air stream was at a slip/skid presentation. This would allow for a slip/skid to go undetected and uncorrected.
In conclusion, the Hamster works as advertised in normal positive G's environments and fails otherwise, and for this reason we won't release it for sale. At the current time, it's only being sold for sailplanes on a limited bases to pilots who are truly interested in it's function and with full knowledge of it's shortcomings, like the negative G's and the winch launch phase of flight.
Ok, with all of that now explained, I'd be interested in hearing from anyone who has ideas on how to address these issues.
