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donjohnston

Joined: 13 Dec 2009
Posts: 231

Posted: Sat Dec 21, 2013 10:20 am Post subject: Solicitation for opinions on backups

I'm working on the electrical system for my Velocity XL-RG and would like to get some opinions on backup power. 



Here's the platform details:

Continental IO-550N

28v Electrical System

Single battery

Vertical Power VP-X Pro

Grand Rapids EIS 6000

Single screen Grand Rapids HXr

Dual AHRS

Dual Magnetometers

Dynon Pocket Panel (Backup EFIS)



If the VPX should have a catastrophic failure, between the Dynon (which should run for 4 hours on it's internal battery) and my iPad with foreflight, I should be able to get on the ground in one piece (albeit, hopefully VFR). 



Some other builders using the VPX are utilizing the multiple power inputs on the HX display and AHRS by running a separate supply through traditional fuses/circuit breakers. The only alternate power supply I currently have in the plans is for the fuel boost pump. My logic is that's the only electrical component that needs to run to keep the plane in the air. 



To utilize the additional power supply lines on the HX and AHRS wouldn't be a huge undertaking but it does add more work, more wires, one more thing that could fail, etc. 



Just wondering what others think.



Thanks,

Don

tim2542(at)sbcglobal.net
Guest

Posted: Sat Dec 21, 2013 11:22 am Post subject: Solicitation for opinions on backups

Id suggest a brownout / backup battery, for the GRT EFIS equipment, they will brown out and reboot if you crank the engine while they are on. I used a 7ah fire alarm battery, charged thru a Schottkey diode and feed thru a separate switch to one of the 3 diode isolated inputs on the GRT. You may want to use a resistor in the charge circuit to limit the current, but I have not had any problem without it. 

This allows me to boot one EFIS & the Garmin 430 to get my clearance and enter a flight plan before I start the engine, and provides enough basic flight instruments to get to the ground with if I lose the main bus. 

It also allows you to stuff that ugly EIS somewhere other than in the panel since you will have your screens up and running when you crank. I put mine in the battery compartment, and instantly dropped about 40 wires that otherwise would have had to be run to the panel. (You will seldom need to access the EIS, never in flight)

I used an E-bus also, but now think that and the Aux circuit are redundant. 

I would also suggest you revisit your decision to use a 28 volt system on a home built, it's your decision, but you almost certainly will want to add a 12 automotive gadget of some kind ( USB /phone charger etc), and will end up having to add a converter. 

I'm using the above on my Cozy, and would change nothing other than lose the E-bus.

My 2centavos

Tim



 	  Quote: 	
		   On Dec 21, 2013, at 10:20 AM, "donjohnston" <don(at)velocity-xl.com> wrote:

 

 

 

 I'm working on the electrical system for my Velocity XL-RG and would like to get some opinions on backup power. 

 

 Here's the platform details:

 Continental IO-550N

 28v Electrical System

 Single battery

 Vertical Power VP-X Pro

 Grand Rapids EIS 6000

 Single screen Grand Rapids HXr

 Dual AHRS

 Dual Magnetometers

 Dynon Pocket Panel (Backup EFIS)

 

 If the VPX should have a catastrophic failure, between the Dynon (which should run for 4 hours on it's internal battery) and my iPad with foreflight, I should be able to get on the ground in one piece (albeit, hopefully VFR). 

 

 Some other builders using the VPX are utilizing the multiple power inputs on the HX display and AHRS by running a separate supply through traditional fuses/circuit breakers. The only alternate power supply I currently have in the plans is for the fuel boost pump. My logic is that's the only electrical component that needs to run to keep the plane in the air. 

 

 To utilize the additional power supply lines on the HX and AHRS wouldn't be a huge undertaking but it does add more work, more wires, one more thing that could fail, etc. 

 

 Just wondering what others think.

 

 Thanks,

 Don

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=415997#415997

donjohnston

Joined: 13 Dec 2009
Posts: 231

Posted: Sat Dec 21, 2013 11:32 am Post subject: Re: Solicitation for opinions on backups

 	  tim2542(at)sbcglobal.net wrote: 	
		  Id suggest a brownout / backup battery, for the GRT EFIS equipment, they will brown out and reboot if you crank the engine while they are on. I used a 7ah fire alarm battery, charged thru a Schottkey diode and feed thru a separate switch to one of the 3 diode isolated inputs on the GRT. You may want to use a resistor in the charge circuit to limit the current, but I have not had any problem without it. 	




Tim,

The plan was to not power up the EFIS until the engine was running. My EIS is already at the rear of the cabin (out of sight).  But the alarm line will activate on low oil pressure.  I wanted to do a brownout/backup battery but I couldn't find an acceptable 24v battery.  Got any suggestions?



-Don

tim2542(at)sbcglobal.net
Guest

Posted: Sat Dec 21, 2013 1:14 pm Post subject: Solicitation for opinions on backups

Yep,  12 volt system. Sorry but I think you will run into one after another of these issues. 

Just one guys opinion. 

Also if the alarm is from the EIS drop it and use the EFIS alarm instead. You won't be able to reset the EIS alarms unless it's in the panel. So they can all be left deactivated when you set up the EIS. 

Tim



Tim



 	  Quote: 	
		   On Dec 21, 2013, at 11:32 AM, "donjohnston" <don(at)velocity-xl.com> wrote:

 

 

 

 

 tim2542(at)sbcglobal.net wrote:

> Id suggest a brownout / backup battery, for the GRT EFIS equipment, they will brown out and reboot if you crank the engine while they are on. I used a 7ah fire alarm battery, charged thru a Schottkey diode and feed thru a separate switch to one of the 3 diode isolated inputs on the GRT. You may want to use a resistor in the charge circuit to limit the current, but I have not had any problem without it.

 

 

 Tim,

 The plan was to not power up the EFIS until the engine was running. My EIS is already at the rear of the cabin (out of sight).  But the alarm line will activate on low oil pressure.  I wanted to do a brownout/backup battery but I couldn't find an acceptable 24v battery.  Got any suggestions?

 

 -Don

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=416005#416005

edpav8r(at)yahoo.com
Guest

Posted: Sat Dec 21, 2013 1:56 pm Post subject: Solicitation for opinions on backups

On Dec 21, 2013, at 1:32 PM, "donjohnston" <don(at)velocity-xl.com> wrote:

 	  Quote: 	
		   I wanted to do a brownout/backup battery but I couldn't find an acceptable 24v battery.  Got any suggestions?


	


Two 12V batteries, each with half your required capacity, wired in series.  There may be charge balancing issues with this configuration; perhaps someone smarter than me can address this.



If you just want brownout protection, it could be provided by Eric Jones' "de-slumpifier" super-capacitor device, rehashed for 28V operation.



Does the GRT power the AHRS and magnetometer boxes, or do they need separate backup power feeds?



Eric

donjohnston

Joined: 13 Dec 2009
Posts: 231

Posted: Sat Dec 21, 2013 2:37 pm Post subject: Re: Solicitation for opinions on backups

I thought about using two 12v batteries but I couldn't figure out a way around the unequal charging issue. 



The GRT display (HXr) and AHRS pull power directly. The magnetometers are powered by the AHRS.

raymondj(at)frontiernet.n
Guest

Posted: Sat Dec 21, 2013 3:43 pm Post subject: Solicitation for opinions on backups

Regarding the unequal         charging issue, as I recall from talking to Bob, it's only an         issue if the batteries are subjected to different states of         discharge and then coupled for recharging.  I believe as long as         the units are always together, the fact that they exist in 2         cases instead of 1 is not relevant.

        	  Quote: 	
		  Raymond Julian

Kettle River, MN.



"And you know that I could have me a million more friends,

and all I'd have to lose is my point of view." - John Prine 	
       On 12/21/2013 04:37 PM, donjohnston wrote:

     

     [quote]        	  Quote: 	
		  --> AeroElectric-List message posted by: "donjohnston" <don(at)velocity-xl.com> (don(at)velocity-xl.com)



I thought about using two 12v batteries but I couldn't figure out a way around the unequal charging issue. 



The GRT display (HXr) and AHRS pull power directly. The magnetometers are powered by the AHRS.





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=416013#416013



	
     [b]

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Dec 21, 2013 3:56 pm Post subject: Solicitation for opinions on backups

At 12:20 PM 12/21/2013, you wrote:

 	  Quote: 	
		  



I'm working on the electrical system for my Velocity XL-RG and would 

like to get some opinions on backup power.



Here's the platform details:

Continental IO-550N

28v Electrical System

Single battery

Vertical Power VP-X Pro

Grand Rapids EIS 6000

Single screen Grand Rapids HXr

Dual AHRS

Dual Magnetometers

Dynon Pocket Panel (Backup EFIS)



If the VPX should have a catastrophic failure, between the Dynon 

(which should run for 4 hours on it's internal battery) and my iPad 

with foreflight, I should be able to get on the ground in one piece 

(albeit, hopefully VFR).


	


   . . . . and a meteor through your crankcase would

   certainly stop the engine too . . .



   I'm not trying to be obtuse my friend but before

   you starting building a plan-b, it would be wise

   to assess the risks and the effects of those risks

   on plan-a first.



   At the same time, it's very useful to consider the

   planned missions in concert with your own skill

   set to craft a plan-b that will offer a 99.9%

   probability of sweat-free arrival with the

   earth when presented with ANY SINGLE FAILURE

   in the compliment of hardware you've listed above.



   You need an energy budget for plan-B along

   with a SUBSET list of the goodies cited above

   that will guide you to a comfortable termination

   of flight should the alternator quit. Then

   insure successful implementation of that plan

   with judicious preventative maintenance of

   the battery . . . which is how the BIG guys

   do it.



   You're contemplating a need for 'backup power'

   based on what catastrophic failure? Have you

   identified a failure that will put the whole

   VP-X system to sleep?  If so, you need to

   have some serious discussions with Marc who

   will either fill you in on where the analysis

   went wrong  -or-  give you good reason to

   remove the system in favor of a legacy design

   that doesn't propagate a single failure across

   system boundaries.



   Attempting to craft plan-c, d, e, and f for

   every imaginable failure invariably creates

   a system so complex that it is MORE likely

   to suffer a failure . . . while offering you

   too many options at a time when you need to

   be a pilot as opposed to a systems manager.



   Have you listed your design goals for this

   project? One-liners that speak to an objective

   based on demonstrable risk and equally demonstrable

   verification or testing.



   This is the process we go through to craft

   a plan-b based on understanding of the

   system's capabilities and limits after EVERY

   reason to fear it has be eliminated.



   Can you post a list of your design goals and the

   circumstances that drive them?



   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Dec 21, 2013 4:04 pm Post subject: Solicitation for opinions on backups

At 04:37 PM 12/21/2013, you wrote:

 	  Quote: 	
		  



I thought about using two 12v batteries but I couldn't figure out a 

way around the unequal charging issue.



The GRT display (HXr) and AHRS pull power directly. The 

magnetometers are powered by the AHRS.


	


   What 'unequal charging issue'  . . . are there plans for tapping

   the 12v terminal of the 24v string to power some device?



   A 24v battery is 12 cells in one box. Two 12v batteries

   are 12 cells in two boxes. They series up and behave

   just as if they were 12 cells in one box as long as you

   don't mess with the junction between the two batteries.



   Bob . . .

donjohnston

Joined: 13 Dec 2009
Posts: 231

Posted: Sat Dec 21, 2013 5:03 pm Post subject: Re: Solicitation for opinions on backups

 	  Quote: 	
		  . . . . and a meteor through your crankcase would certainly stop the engine too . . .



I'm not trying to be obtuse 	




And yet, here we are...



I didn't intend to discuss engine reliability. That is outside the purview of my post.  I humbly apologize if I somehow misstated my question. 



 	  Quote: 	
		  At the same time, it's very useful to consider the planned missions in concert with your own skill set to craft a plan-b that will offer a 99.9%

probability of sweat-free arrival with the earth when presented with ANY SINGLE FAILURE in the compliment of hardware you've listed above. 	




And I've done that.  Again, I didn't mean to imply that was my question. 



 	  Quote: 	
		  You're contemplating a need for 'backup power' based on what catastrophic failure? 	




And that brings us to what my post is actually about.  I hadn't planned on a catastrophic failure.  Alternator and battery was my plan. But when you're getting ready to jump in the water to go swimming and it looks like everyone else is in a shark cage, you have to question whether or not you've thought everything through. After looking at other builders using the VP-X and seeing almost a 100% adoption of an alternate power approach, I decided to post the "solicitation for opinions". 



And now that we've gone through all that, can someone tell me how to delete a post?

Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Sat Dec 21, 2013 6:23 pm Post subject: Solicitation for opinions on backups

Don't assume that what you see on forums is a majority or even a plurality.

I wired up a VP-X for my project, where there is a single alternator, a 

single ship's battery, and one switch that turns off all non-essential 

avionics.

Each of my two EFIS screens has its own backup battery that takes over 

when ship's power drops below something like 12.3 volts.

Of course the VP-X lets me turn on or off individual items for the 

situation IF I have time to think about what is needed. I expect to get 

30 min backup from ship's battery and another 45 min of glass panel, 

which I can operate sequentially if need to get more time...but if I can 

find some place to land within an hour, I have other problems. Sticking 

with conventional Bendix 1200 mags to keep things simple and reliable. 

Maybe others need more backup, but I don't for my missions. If the VP-X 

should happen to fail catastrophically I would have to rely on my 

handheld navcom and handheld GPS. I don't judge that risk to be high 

enough to complicate things with wiring to bypass the VP-X.



On 12/21/2013 6:03 PM, donjohnston wrote:

 	  Quote: 	
		   

     Alternator and battery was my plan. But when you're getting ready to jump in the water to go swimming and it looks like everyone else is in a shark cage, you have to question whether or not you've thought everything through. After looking at other builders using the VP-X and seeing almost a 100% adoption of an alternate power approach, I decided to post the "solicitation for opinions".



 And now that we've gone through all that, can someone tell me how to delete a post?

   [Embarassed]





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=416021#416021

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

donjohnston

Joined: 13 Dec 2009
Posts: 231

Posted: Sat Dec 21, 2013 6:48 pm Post subject: Re: Solicitation for opinions on backups

That's what I was thinking. I was just looking for a little sanity check.   



I thought that I had a pretty good plan but then I kept seeing others (not for a second did I think that the builds I was seeing made up 100% of all the installs) that were building with belts, suspenders, staples, tape and backup belts.   



My philosophy was to be as simple and safe. I was just starting to think that I was overlooking something. 



Thanks for the opinion!

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Dec 21, 2013 6:59 pm Post subject: Solicitation for opinions on backups

Don,



Please forgive my tongue in cheek reference to over-worrying

a problem.



My intent was to highlight a common problem with plug-n-play

responses to incomplete questions.



You mentioned catastrophic failure of the Vertical Power

system as a concern. This suggests to me that your faith

in the VP-X system is weak . . . possibly because you lack

a comfortable handle on the likelihood of such an event

or a game plan for dealing with the kinds of failures

that might plague the VP-X.



This is a system design/integration problem when the

builder buys a REALLY neat box that sings, dances and

washes dishes . . . but doesn't offer a clear notion

of how one should deal with getting a few dishes washed

when the light bulb over the sheet music goes out.



You have purchased a system that would get a LOT

of scrutiny by the engineers tasked with first making

it work on a TC airplane and then qualifying it. Believe

me, there would be few if any stones left unturned.

Now the box is on your workbench . . . all you've

got are the wiring diagrams and operator's manual . . .

and you have some worries . . . but about what?



The booths at OSH are sprinkled with all manner of

'solutions' to over-worried and/or under-studied

problems.  I strolled those isles 13 years running

and marveled at the kinds of things sold onto OBAM

aircraft that were never offered on TC aircraft . . .

but didn't seem to make an observable difference

in accident rates. Nor did they offer a demonstrable return

on investment for cost of ownership and loss of payload

when the empty weight of your airplane went up.



All I was suggesting is that your quest for

recommendations on a 'backup power source'

was incomplete. Has the worried-about failure

been qualified and quantified for both probability

and an energy budget to deal with it?



You're going to get a number of suggestions. How

do you pick the best one? If you add a battery or

two, battery maintenance demands go up even though

you may not need to use that battery over the

lifetime of the airplane.



My fondest wish for the List is that it be

a forum for sifting the simple ideas based on

physics and lessons learned to arrive at a lower

cost, lighter weight, simpler solution. But it

does take some time, study and establishment

of design goals.



   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Dec 21, 2013 7:01 pm Post subject: Solicitation for opinions on backups

At 05:42 PM 12/21/2013, you wrote:

  	  Quote: 	
		  Regarding the unequal charging issue, as I recall from talking to Bob, it's only an issue if the batteries are subjected to different states of discharge and then coupled for recharging.  I believe as long as the units are always together, the fact that they exist in 2 cases instead of 1 is not relevant. 	


   you remember rightly . . .



 

 

   Bob . . .    [quote][b]

donjohnston

Joined: 13 Dec 2009
Posts: 231

Posted: Sat Dec 21, 2013 7:43 pm Post subject: Re: Solicitation for opinions on backups

 	  Quote: 	
		  Please forgive my tongue in cheek reference to over-worrying

a problem. 	


Apologies. I was unable to discern the location of your tongue for that post.  



 	  Quote: 	
		  My intent was to highlight a common problem with plug-n-play

responses to incomplete questions.  	


And I wasn't really looking for an answer since I really didn't have a true question.  I was really just looking (fishing, if you will) for opinions as to how far is too far when dealing with putting in "backups".



My approach is fairly straightforward (at least for me). 



I'm running a standard, stock aircraft engine, mags (not an electronic ignition). My only deviation from what's been used in the foundation of GA aircraft for years is the VP-X.  If the stock alternator fails, I've got a B&C SD-20. If that fails, I've got the battery.  If the VP-X fails, the engine will continue producing power (the boost pump can pull power from the VP-X or directly from the battery).  I'll be able to keep the shiny side up with the Dynon D1 for up to four hours (much longer than the battery would probably  last). I've got a iPad with a GPS and a Garmin 396 to help me figure out where I'm going. 



So I think that I've got a good Plan B, C, D, E and F. 



I was just looking for opinions (not answers, opinions) on whether the additional wire, hardware, etc. required to keep the EFIS glowing happily running after the unlikely event of a VP-X failure was worth the trouble. And since I wasn't born yesterday, I know that opinions are like buttholes (everyone else's stink). 



We cool?

peter(at)sportingaero.com
Guest

Posted: Sun Dec 22, 2013 1:51 am Post subject: Solicitation for opinions on backups

Don,

My opinion is that I would provide power to your EFIS and main radios 

that does not involve the VPX.

You have 2 alternators, so if the engine is turning you will likely have 

a power supply.

When stuff goes wrong the work load goes through the roof very quickly, 

so keeping as much of your panel working as possible will minimise the 

rise in workload - and therefore your ability to continue to fly the 

airplane. I would suggest a D1 and an iPad are already plan f rather 

than plan b.

Plan b should make the failure of any one component (including the VPX) 

almost transparent to the pilot. That means providing power to the EFIS 

and main radio that does not involve the VPX. It would be daft to have 

power available but a dark panel because one component in your system 

went down.

Peter

On 22/12/2013 03:43, donjohnston wrote:

 	  Quote: 	

> Please forgive my tongue in cheek reference to over-worrying

> a problem.

 Apologies. I was unable to discern the location of your tongue for that post. [Laughing]

> My intent was to highlight a common problem with plug-n-play

> responses to incomplete questions.

 And I wasn't really looking for an answer since I really didn't have a true question.  I was really just looking (fishing, if you will) for opinions as to how far is too far when dealing with putting in "backups".

 My approach is fairly straightforward (at least for me).

 I'm running a standard, stock aircraft engine, mags (not an electronic ignition). My only deviation from what's been used in the foundation of GA aircraft for years is the VP-X.  If the stock alternator fails, I've got a B&C SD-20. If that fails, I've got the battery.  If the VP-X fails, the engine will continue producing power (the boost pump can pull power from the VP-X or directly from the battery).  I'll be able to keep the shiny side up with the Dynon D1 for up to four hours (much longer than the battery would probably  last). I've got a iPad with a GPS and a Garmin 396 to help me figure out where I'm going.

 So I think that I've got a good Plan B, C, D, E and F.

 I was just looking for opinions (not answers, opinions) on whether the additional wire, hardware, etc. required to keep the EFIS glowing happily running after the unlikely event of a VP-X failure was worth the trouble. And since I wasn't born yesterday, I know that opinions are like buttholes (everyone else's stink).

 We cool?  

 Read this topic online here:

 http://forums.matronics.com/viewtopic.php?p=416032#416032

Mauledriver(at)nc.rr.com
Guest

Posted: Sun Dec 22, 2013 6:00 am Post subject: Solicitation for opinions on backups

After reading this comment, I finally decided to actually read the 

Vertical Power overview.  When I was designing my electrical system and 

panel 5 or 6 years ago, VP-X wasn't on my scope and I never looked back.



If a recommendation is that I need to backup wire around the VP-X, I had 

to go "huh?"



I can see that it can simplify the electrical system design task and 

adds some functionality.   I can see the appeal.



do not archive



 	  Quote: 	
		   My opinion is that I would provide power to your EFIS and main radios 

 that does not involve the VPX.



 You have 2 alternators, so if the engine is turning you will likely 

 have a power supply.



 When stuff goes wrong the work load goes through the roof very 

 quickly, so keeping as much of your panel working as possible will 

 minimise the rise in workload - and therefore your ability to continue 

 to fly the airplane. I would suggest a D1 and an iPad are already plan 

 f rather than plan b.



 Plan b should make the failure of any one component (including the 

 VPX) almost transparent to the pilot. That means providing power to 

 the EFIS and main radio that does not involve the VPX. It would be 

 daft to have power available but a dark panel because one component in 

 your system went down.

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Dec 22, 2013 8:58 am Post subject: Solicitation for opinions on backups

At 07:58 AM 12/22/2013, you wrote:




After reading this comment, I finally decided to actually read the 

Vertical Power overview.  When I was designing my electrical system 

and panel 5 or 6 years ago, VP-X wasn't on my scope and I never looked back.



   GOOD FOR YOU! It pays to be informed  . . .



If a recommendation is that I need to backup wire around the VP-X, I 

had to go "huh?"



I can see that it can simplify the electrical system design task and 

adds some functionality.   I can see the appeal.



   I don't think anyone has recommended any such thing

   yet. The phrase "catastrophic failure" was used as a

   worry-topic for the VP-X. I stretched the premise

   past the absurd by suggesting that 'meteors

   through the crankcase' might also be considered.

   The knowledgeable and skilled retorts might be

   something like this:



   "well considered chances of meteors through the

   crankcase is Z.F x 10 to the minus gazillion

   events per flight hour and the chances of a failure

   that cripples multiple systems in a VP-X system is

   G.C x 10 to the minus 6, 7 or 8 events per flight

   hour, hence there are NO practical worry points for

   either event.



   Given that nobody has come forth with a skilled

   MTBF study on VP-X (and none is expected), then

   we are left with the kinds of analysis that can

   be accomplished by judicious consideration of

   design features . . . or failure modes effects

   analysis.



   This is an activity that I encouraged Marc to

   conduct throughout the evolutionary advances

   to his design. We met in the pilot's lounge

   of KAAO about ten years ago when the VP-X system

   was but a gleam in his eye.



   Unlike some other products offered onto the OBAM

   and even TC aviation markets, there has been no

   hue and cry of customer dissatisfaction nor flurry

   of ADs against VP-X products so I am hopeful that

   Marc took my advice to heart and had conducted

   due diligence in the design, manufacturing and

   marketing of his products.



   At the same time, all of you as mney paying

   consumers of those products have every right

   to make detailed inquiry as to his design and

   verification processes. If you value your

   aluminum AND bones, then you have a DUTY to

   make such inquiry.



   The VP-X system is capable of taking on task

   criticality on a par with say an engine. We cannot

   carry back-up engines. Unless we have a

   confidence level in the VP-X system that is

   within a few orders of magnitude of that

   which we assign to engines, then the question

   of "back up" becomes more problematic.



   The difference here is whether we add a back-up

   because we DON'T know or because we DO KNOW.



   My bosses have paid me to find out such things

   for 50 years. . . . and yes, I'm reasonably certain

   that meteor shields built into the cowl will only

   add cost, weight and no value. You are your own

   boss. Okay boss, what's the drill going to be

   for assessing the necessity and/or value of

   adding a backup feature YOUR implementation

   of the VP-X system?



   Further, arriving at some useful conclusion will

   be much easier if it's crafted and sifted here

   on the List. GOOD information for doing . . .

   or NOT doing things is worth sharing.

   Bob . . .

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