NAR L3 WIRING - HELP!!

Zeus-cat said:

I know someone who just joined Tripoli just to get his L3 because of this switch requirement.

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Yup, I'm one of those.
And the club I fly with the most was a Tripoli club.
Adrian

Not to stir the pot, but TRA requires the rocket to stay within the waiver area, NAR doesn't. TRA requires full chute deployment, NAR doesn't. And my L3CC did not require any funky wiring or switches on the alts. Just saying....

Maybe NAR doesn't explicitly require remaining within the waiver, but that's what the waiver holder is agreeing to do.
As far as comparing NAR to TRA, I'm not going to engage in such. The are complementary with an overlap covering high power. Not only am I a NAR L3CC, but I'm also the Prefect of Tripoli Montana. I think nothing is gained by childish one upmanship by either organization's members.


[emoji1010] Steve Shannon, L3CC [emoji1010]

Steve Shannon said:

Maybe NAR doesn't explicitly require remaining within the waiver, but that's what the waiver holder is agreeing to do.
As far as comparing NAR to TRA, I'm not going to engage in such. The are complementary with an overlap covering high power. Not only am I a NAR L3CC, but I'm also the Prefect of Tripoli Montana. I think nothing is gained by childish one upmanship by either organization's members.


[emoji1010] Steve Shannon, L3CC [emoji1010]

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I agree but both groups should work at achieving a reasonable consistency of requirements amongst their respective L3CC and TAPs. Reverse polarity altimeters I believe are in the minority now if they're are any left flying. The problem there was connect the battery up backwards and any attached charges would blow when the device was turned on. Remedy? Make sure + goes to +, - to -. Simple, isn't it?
Now you get the Quantum altimeter and it doesn't matter how the battery is connected to the terminals!

TRA wasn't perfect either. Look at the cover of Extreme Rocketry issue number 52, 2006 and you'll see 6 plug switches on a TRA L3 attempt. (Was successful) Kurt

I think both do work at consistency. Unfortunately, writing requirements that allow personal design choices without being lent to inconsistent interpretation is difficult.


[emoji1010] Steve Shannon, P.E. [emoji1010]

Steve Shannon said:

I think both do work at consistency. Unfortunately, writing requirements that allow personal design choices without being lent to inconsistent interpretation is difficult.
[emoji1010] Steve Shannon, P.E. [emoji1010]

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Ahhhhhhh, It's simple. Don't require "safety switches" of any kind on any ematch circuit/channel that is for the
ACTIVATION of recovery devices. As long as there is a decent quality "on-off" switch at the battery side of the altimeter circuit and the manufacturers recommendations are followed, one is good to go. Put it in clear writing so all the L3CC/TAPs are aware and end this stupidness once and for all. (Staging/air-starting I don't profess to know the answer to the problem of safing those ignition circuits but that is not a certification issue.)

If the flier wants to have a "novel safety circuit" of their own doing, so be it as long as the TAP/L3CC doesn't see a problem with it.

Kurt Savegnago

^+1

Has there EVER been a documented or even anecdotal case in the recent history (last 10 years) of a recovery charge going off when an altimeter was disconnected from its battery? Ever? Even rumor of an instance?

Has there ever been an documented or anecdotal case of a switch failing that causes a recovery system failure?

Based on the above instance ratio you can draw your own conclusions on whether "adding" switches to a system increases real safety.

jderimig said:

^+1

Has there EVER been a documented or even anecdotal case in the recent history (last 10 years) of a recovery charge going off when an altimeter was disconnected from its battery? Ever? Even rumor of an instance?

Has there ever been an documented or anecdotal case of a switch failing that causes a recovery system failure?

Based on the above instance ratio you can draw your own conclusions on whether "adding" switches to a system increases real safety.

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This used to happen. I had a Transolve P6+ that was indeed sensitive to switch bounce (and let me know it by firing charges on the pad). But for any new altimeters, no.

jderimig said:

^+1

Has there EVER been a documented or even anecdotal case in the recent history (last 10 years) of a recovery charge going off when an altimeter was disconnected from its battery? Ever? Even rumor of an instance?

Has there ever been an documented or anecdotal case of a switch failing that causes a recovery system failure?

Based on the above instance ratio you can draw your own conclusions on whether "adding" switches to a system increases real safety.

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Amen!!! +1+1+1+1 It seems they shouldn't be trying to solve a problem that doesn't exist!

The ironic thing is, I can wire up my avionics as my schematic shows, put an “L” or “K” motor in it and fly it every month and nobody would bat an eye regarding pyro safety. This rocket will use the same size ejection charges regardless of motor size. Putting an “M” motor in it shouldn’t suddenly cause the ejection charges to become an unacceptable risk.

I think this is where the L3CC should have discretion in the matter, as all rockets are not built the same. Tripoli never had this requirement and left it up to the TAPs to decide if the design was safe. My uncomplicated design using a 5.5” airframe will only use about 2.5 grams of 4F to eject the laundry and a little more for the backup (I’ll ground test of course). Someone flying a monster rocket may be using 15 grams or more of 4F in multiple charges using more complicated electronics. This is where more oversight and precautions could be warranted. But once again, that is where the L3CC should have the discretion.

Altacc altimeters used to go off if the switch between the battery and the altimeter was noisy. It happened to me when a friend of mine (a TAP by the way) was prepping a rocket. We found we could duplicate it by turning it on three times. Outputs can come up in an unexpected state, although I think all commercial manufacturers prevent that now.
I see people every year who want to fly electronics that they have designed and built.
TAPs and L3CC members must continue to have the authority to reject unsafe designs, but flyers should feel comfortable having a direct conversation with their TAP or L3CC about their design. Not every L3CC is an electrical engineer.
I disagree though with the that safety switches added to the charge lines reduce reliability disproportionately to the added safety. A good quality switch, properly selected for the application has a failure rate of once in millions of uses and the most common failure mode is failed closed. Here's a Navy document that discusses such.
https://www.navsea.navy.mil/Portals...8/PDFs/Products/Archive/Switches/Switches.pdf
I just came back from the SLI where I worked with other L3CCs and TAPs to conduct safety checks and range operations. Out of 44 rockets, we had at least two occasions where the range personnel had to leave the range closed while someone from our group went out and had to disconnect live charges. That's a much greater incidence than the risk of switch failure. Every team uses a slightly different means of turning on their electronics, with most relying on inserting a screwdriver into a small hole on the airframe, finding the screw head, but missing any circuitry, and turning it. Having a common and easy means of making charges safe would be really nice. There are ways to do it without switches. I always considered using a fuse block with a solid copper slug in place of the fuse for each e-match circuit, but just being able to cut the wires would be great.


[emoji1010] Steve Shannon, P.E. [emoji1010]

Steve, I agree that adding a switch in the pyro circuit to compensate for inadequate electronics or poorly selected main power switches will result in a safer system. And the L3CC and/or TAP must have the discretion of judging the system to determine what is required for a conservative safety level.

But there is something to be said for encouraging a sound primary system. If a flyer certifies with inadequate switches and electronics that is "safe'd" by pyro switches but then all his future flights have the pyro switches removed from his inadequate primary system, what have we accomplished?

Fodder for discussion...

Instead of the L3 requirements being so specific about wiring, would it perhaps make more sense to have a requirement that the member has been able to successfully demonstrate flying with a particular altimeter over time as a Level 2?

As an example, my L3 flight was my first time doing redundant altimeters, but I had flown each of my altimeters with the same wiring configuration many times before. So for me, my L3 wiring diagram was just combining two single DD configs into one.

Specifically, I used a StratologgerCF and an RRC2+. I had used each before, but in different rockets and in a single alt. config. So, when I combined them into a redundant config, I just did what I always do. They had always worked like that, and I knew they would work like that. The only difference was to set the back-up alt's timing to apogee+1 and main -100.

I went into my L3 flight with utter confidence that this config would work, and my L3CC and document reviewer agreed, and everyone was happy.

Steve Shannon said:

There are ways to do it without switches. I always considered using a fuse block with a solid copper slug in place of the fuse for each e-match circuit, but just being able to cut the wires would be great.


[emoji1010] Steve Shannon, P.E. [emoji1010]

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I considered doing something similar. I found some flush mount automotive blade fuse holders. You would need pliers to remove the fuses but it would give you a sleek, reasonably flush/aerodynamic method to disconnect charges and could possibly be used as a safety against ematch shorts damaging your altimeter.
The holder was the 'narva 54394' and would need to be mounted 3/16 - 1/4" in from the surface to sit flush.
If your altimeter has 8 Amp FETs, a 10 Amp fuse would offer a bit of protection as they can handle 150% overload for around 1 second and if you are drawing 15 Amps you have other issues. What are other people's thoughts on this idea? I would still use a single switch for each altimeter for convenience.
I think this would possibly work better for airstarts rather than deployment charges but it might be an option.

jderimig said:

Steve, I agree that adding a switch in the pyro circuit to compensate for inadequate electronics or poorly selected main power switches will result in a safer system. And the L3CC and/or TAP must have the discretion of judging the system to determine what is required for a conservative safety level.

But there is something to be said for encouraging a sound primary system. If a flyer certifies with inadequate switches and electronics that is "safe'd" by pyro switches but then all his future flights have the pyro switches removed from his inadequate primary system, what have we accomplished?

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I absolutely agree.

This is what I do. I take the "new" altimeter, wire bare contained ematch canisters to it at the bench, connect a representative switch and do all sorts of stuff to it like rapidly turning it on/off, turn in off and then back on again quickly, shake the switch,
securely shake the altimeter and I haven't had anything adverse happen to a variety of altimeters. I will say I had adverse events related to P6's which I won't attempt to fly anymore.
I've done a HiAlt, Marsa, MAWD, Stratologger Adept 22, Olsen-M2 and haven't experienced any problem with the bench stress test.

How did you know the charges were "live"? Just because they are connected to the altimeter, doesn't mean they are "live". Unless the electronic device is a crude magnetic anomaly detection device like the old Galejs MAD unit, is a nominally
functioning altimeter going to fire mysteriously? If one turns the power switch off, they stop beeping. If worried about "residual power", let sit for 10 minutes if you must. Kurt

That was my point too. If you can demonstrate that you can fly that configuration safely (or have in the recent past) why create a situation where the flyer has to deal with a new system on an already stressful day.

I've flown my Telemetrum and RRC2+ 2-3 times each individually and in combination 2-3 times in different rockets. I use the same screw switch for the power and direct wire the e-matches on every rocket.

neond7 said:

The ironic thing is, I can wire up my avionics as my schematic shows, put an “L” or “K” motor in it and fly it every month and nobody would bat an eye regarding pyro safety. This rocket will use the same size ejection charges regardless of motor size. Putting an “M” motor in it shouldn’t suddenly cause the ejection charges to become an unacceptable risk.

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ChrisAttebery said:

That was my point too. If you can demonstrate that you can fly that configuration safely (or have in the recent past) why create a situation where the flyer has to deal with a new system on an already stressful day.

I've flown my Telemetrum and RRC2+ 2-3 times each individually and in combination 2-3 times in different rockets. I use the same screw switch for the power and direct wire the e-matches on every rocket.

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I wonder if this is the root of the matter- back when these codes were defined, L3 was a very expensive proposition (it arguably still is, but allow me to explain). 10-15 years ago, I have to imagine that flight computers were far more expensive than they are today, so was it less likely to encounter them in the L2 arena? L3 projects are massive, and simply are more likely to require electronics for safe recovery. Therefore, that is where the code-makers placed the electronic requirements. Nowdays I can afford to fly an amazingly feature-packed unit in a LPR bird if I wanted to, or I include Dual Deploy on relatively small L1/L2 flights because I don't want to walk. Point is, we're moving the learning curve of electronics and dual deploy earlier into the process than it was feasible to expect back when the codes were written. Maybe the whole argument is nullified by making the requirement for electronic proficiency be part of L2 cert?

soopirV said:

I wonder if this is the root of the matter- back when these codes were defined, L3 was a very expensive proposition (it arguably still is, but allow me to explain). 10-15 years ago, I have to imagine that flight computers were far more expensive than they are today, so was it less likely to encounter them in the L2 arena? L3 projects are massive, and simply are more likely to require electronics for safe recovery. Therefore, that is where the code-makers placed the electronic requirements. Nowdays I can afford to fly an amazingly feature-packed unit in a LPR bird if I wanted to, or I include Dual Deploy on relatively small L1/L2 flights because I don't want to walk. Point is, we're moving the learning curve of electronics and dual deploy earlier into the process than it was feasible to expect back when the codes were written. Maybe the whole argument is nullified by making the requirement for electronic proficiency be part of L2 cert?

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In the old days one could do the L3 with one deployment device as they were so pricey. In reality, 1 + 1 backup is so much better to ensure the success of the flight. One is supposed to be able to say they've flown with electronics before the L3 attempt.

Kurt

I am also building for a NAR L3 cert, so I've been struggling with the same questions. I've flown a lot of Dual Deploy, but with only two switched. My L3CC said if the altimeter does not use stored capacitance to fire the charges then a single switch on the battery + is ok. I've got one altimeter that uses a cap and one that only uses a cap for brown-out. I've got some Electrical Engineering background, so I understand the logic of requiring the additional switches, especially with a wide mix of altimeters on the market. That being said, safety when dealing with multiple dependent systems is requires weighting of probabilities and severity of outcome to the overall design. Reducing the risk of ground-based ejection charges firing with switches (low probability / moderate severity) increases the risk of in-flight deployment (low probability / high severity). Adding additional switches lowers risk around static electricity, CMOS failure, overheating failure, or metal shavings in the av bay accidentally firing at the wrong time, but additional switches introduce additional solder joints and mechanical connections that are subject to fail under the extreme g's and shaking of an M motor lift-off. IMHO the former does not outweigh the later, given simplicity of design principles and greater loss of life risk to in-flight issues vs. ground issues. I think a long-term resolution to this debate might be to build the capability into altimeters and have NAR approve the designs.

For my L3 I am considering using small rotary switches for the charges. Like these: https://tinyurl.com/jd7yjx2 I need to validate amperage and find some with proper specs, but these would allow for 1) flush mount - pinhole switching 2) can actually switch both legs to shunt (static prevention), while creating an open state on the altimeter. This achieves the same thing as twisting (shunting) your ignitor wires, while walking out to the pad and 100% disconnecting from the altimeter. So, if I need to add switches, I figure something like these are best, but will require some unique mounting hardware.

ksaves2 said:

This is what I do. I take the "new" altimeter, wire bare contained ematch canisters to it at the bench, connect a representative switch and do all sorts of stuff to it like rapidly turning it on/off, turn in off and then back on again quickly, shake the switch,
securely shake the altimeter and I haven't had anything adverse happen to a variety of altimeters. I will say I had adverse events related to P6's which I won't attempt to fly anymore.
I've done a HiAlt, Marsa, MAWD, Stratologger Adept 22, Olsen-M2 and haven't experienced any problem with the bench stress test.

How did you know the charges were "live"? Just because they are connected to the altimeter, doesn't mean they are "live". Unless the electronic device is a crude magnetic anomaly detection device like the old Galejs MAD unit, is a nominally
functioning altimeter going to fire mysteriously? If one turns the power switch off, they stop beeping. If worried about "residual power", let sit for 10 minutes if you must. Kurt

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Any charge that isn't known to be disconnected or expended is live. After a crash or some other expected event range personnel and flyers do not know what state the altimeter(s) are in. They may be damaged. In one case we had a charge go off while sitting on the pad waiting to be flown. The only reason that nobody was hurt is because nobody was there; it could just as easily have happened when the person armed it. The point is that things happen and we must make sure that we are safe when they do.
If the altimeter(s) can be easily disconnected from power that should be sufficient. Nobody has ever argued differently. On larger rockets with larger powder charges I personally will probably stick with a way to disconnect the charges as well.

Steve Shannon said:

Any charge that isn't known to be disconnected or expended is live. After a crash or some other expected event range personnel and flyers do not know what state the altimeter(s) are in. They may be damaged. In one case we had a charge go off while sitting on the pad waiting to be flown. The only reason that nobody was hurt is because nobody was there; it could just as easily have happened when the person armed it. The point is that things happen and we must make sure that we are safe when they do.
If the altimeter(s) can be easily disconnected from power that should be sufficient. Nobody has ever argued differently. On larger rockets with larger powder charges I personally will probably stick with a way to disconnect the charges as well.

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Do you know what the root cause of the charge going off on the pad was? I was curious about that since my team used one of the same brand of altimeter.

Steve Shannon said:

Any charge that isn't known to be disconnected or expended is live. After a crash or some other expected event range personnel and flyers do not know what state the altimeter(s) are in. They may be damaged. In one case we had a charge go off while sitting on the pad waiting to be flown. The only reason that nobody was hurt is because nobody was there; it could just as easily have happened when the person armed it. The point is that things happen and we must make sure that we are safe when they do.
If the altimeter(s) can be easily disconnected from power that should be sufficient. Nobody has ever argued differently. On larger rockets with larger powder charges I personally will probably stick with a way to disconnect the charges as well.

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I've had charges blow on the pad and no safety switch could have helped it. Wind was blowing and altimeter blew cause is was an early design and thought it reached apogee. Everyone had stepped away cause we were getting ready to launch it. No one was around.

How would a safety switch helped for the project you witnessed go off on the pad? The key is nobody was nearby and it was waiting to be flown. Where's your logic there? You have none

How in the heck is a safety switch going to help in a crashed rocket? If the stupid power failed in the first place on the channel, it failed. A safety switch isn't going to make it any safer! If the rocket is splattered all over,
ain't no power going to get to an unused ematch. If the ematch failed in the first place how in the heck is the added safing switch adding "more" safety? The stupid match didn't work in the first place!!

If a person turns on an altimeter with the reverse polarity, unless they're attuned to the altimeter the second they turn on the safety switch, kaboom!

I had a Wildman Jr come in under drogue only. Reprogrammed a Raven 2 incorrectly and the main didn't fire. Whad' I do? I shut off the power switch when I picked it up, took it apart and disconnected the ematch/charge.
Did it blow in my face? No. Was the ematch defective? No, I blew it at home buried in the ground with launch electronics. I reset the Raven to the default settings, tested both channels and they were fine. Figured the main altitude settings were wrong. It has flown fine three times since.

Again, the safety switch issue had been put to rest and to have individual L3CC/TAPs insist on it anyways is absolutely assnine. Time to find one who is more enlightened or "TAP/L3CC shop". Kurt

Steve Shannon said:

Altacc altimeters used to go off if the switch between the battery and the altimeter was noisy. It happened to me when a friend of mine (a TAP by the way) was prepping a rocket. We found we could duplicate it by turning it on three times. Outputs can come up in an unexpected state, although I think all commercial manufacturers prevent that now.

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An AltAcc, you say. Was that with the safe/arm switch in the arm or the safe position?

I have looked at a lot of micro-controller data sheets and I have yet to read one that guarantees glitchless initialization of the GPIOs. They tell you how they end up after reset but never a word about what happens before then. While the addition of pulldown resistors on MOSFET gates has helped a lot, it hasn't eliminated all such power up problems.

It would be nice if the requirement, in writing, was to use switches per the manufacture's recommendations?

cbrarick said:

It would be nice if the requirement, in writing, was to use switches per the manufacture's recommendations?

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:y: Now wouldn't that be novel!

dixontj93060 said:

:y: Now wouldn't that be novel!

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Especially with the newer designs, like the eggtimer quantum- it's designed so the deployment channels are electrically off on both legs (pos and neg), without having any switches required. The channels aren't energized until just before apogee. I think it's going to be very tricky to explain this (as I just experienced, I'm sure I muffed some detail up) to some folks when all they want to see are x numbers of switches.

dixontj93060 said:

:y: Now wouldn't that be novel!

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I've got 11 different ones available and I don't see the instructions of any one of them recommending switches on the ematch circuits! I do have one that recommends directly/explicitly in the manual not to fly it with Rf trackers or do so with care.

One word of caution with altimeters that allow a separate pyro battery. If one "doesn't" switch the pyro battery, all the altimeters that are of that configuration I've seen will be drawing a low level current through the ematch circuit for
the continuity test even though the power side of the computer on the second battery is "turned off"! What this means is if one is in the habit of pre-prepping the rocket with charges and you have this altimeter configuration,
you'll be sucking juice from the pyro battery if the rocket is sitting for any length of time (spell that a few days). In that case, if you want to use this device, you'll have to make arrangements for two switches, one for the computer side and one for the pyro battery.
The original EggTimer is of this configuration and I believe my ARTS II does it too. Gotta have two switches not for a safety reason but to save the pyro battery. I found this out with bench testing with LEDs. I'd see unexplained low level glowing.

Yeah, I took bare ematches and shoved them in and out of the terminals on the altimeters to see if they would "pop" on me with a pyro battery connected up and the computer side shut off. Again, no spurious unexpected popping seen.

The only time I've ever had a premature charge go off was due to an Rf tracker interference ( which BTW can cause charges to blow or simply shutdown the altimeter resulting in a ballistic flight. No "safety switch" is going to help you there either) or the wind blowing across a static port causing a premature firing of a charge on the pad with an early generation deployment device with a simple filtering algorithm. Again no "safety switch" is going to help that either.

So Jeff, you're in good shape. With the Perfect Flights, when they're off they're off, when they're on they're on. No juice going out to test continuity until the switch is turned on. I'm surprised another mis-informed party didn't
insist you use "two different" deployment devices. That's another freaking wives tale. You put an apogee delay of 1 second and a different, slightly lower main deployment on the backup one and that's it.
This balderdash of using devices of two different manufacturers is a farce. The only reason to do that in this day and age is simply one has two different altimeters lying around on hand. No particular reason to go out and buy another one! Even in the day when apogee delays could not be set, it was highly unlikely the two charges would blow at the same exact time due to subtle differences in the components on the boards!
Kurt Savegnago

soopirV said:

Especially with the newer designs, like the eggtimer quantum- it's designed so the deployment channels are electrically off on both legs (pos and neg), without having any switches required. The channels aren't energized until just before apogee. I think it's going to be very tricky to explain this (as I just experienced, I'm sure I muffed some detail up) to some folks when all they want to see are x numbers of switches.

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This device I am really excited about. "Screw the switches" We don't need no steekn'in switches!! I think this will lead to devices being able to activate/arm stuff more dicey like airstarting/staging circuits from a safe distance away .
Take your shunts and shove 'em! (Sorry about the hijack but I'm not going "off" on shunts here.):wink:

Best of luck Jeff on your L3 attempt. Hope you can keep your wiring simple. Kurt

dixontj93060 said:

:y: Now wouldn't that be novel!

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Woah! There cowboy, that's just plain lunacy....it makes way to much sense.

ksaves2 said:

This device I am really excited about. "Screw the switches" We don't need no steakn'in switches!! I think this will lead to devices being able to activate/arm stuff more dicey like airstarting/staging circuits from a safe distance away .
Take your shunts and shove 'em! (Sorry about the hijack but I'm not going "off" on shunts here.):wink:

Best of luck Jeff on your L3 attempt. Hope you can keep your wiring simple. Kurt

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Steak and Switches and interesting dinner combo....