Matronics Email Lists :: View topic - Electric dependent Engine

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Electric dependent Engine - Pucker Factor?

Matronics Email Lists Forum Index -> AeroElectric-List

View previous topic :: View next topic

Author Message

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Jun 29, 2009 7:30 am Post subject: Electric dependent Engine - Pucker Factor?

At 04:55 AM 6/29/2009, you wrote:

  	  Quote: 	
		  I have been following the posts on this list for a year or so and ‘Lectric Bob’s writings for maybe 10 years.  This has led to my understanding of failure tolerant design, so that if any part fails (as any part can and will) you go to plan”B” with out needing to raise a sweat.  Not considered as possible failures in this case are such things as prop bolts, wing struts, connecting rods and the like.

  

 I am considering the use of an Eggenfellner E6.0 Subaru Auto conversion.  The electrical system architecture will basically be Z-19.

  

 There are electrical system designs that are very failure tolerant even for electrically dependent engines.  And there are more and more of these electrically dependent engines being used all the time.  But usually you have 2 fuel pumps, 2 electrical paths to the fuel injection/electronic ignition, etc.

  

 The Egg has 1 ECU (Engine Control Unit) computer.  Without it functioning the fan out front does not rotate.  It is a computer whose heart is a microprocessor.

 Is a microprocessor in the same league as a prop bolt for reliability? 	


   Probably not . . . but they CAN be pretty good.

   How's that for a non-quantified answer? Reliability

   is an oft discussed topic here on the List. When

   we speak of reliability in the military or TC

   aircraft world, the discussion necessarily includes

   a study of failure rates for individual components

   (taken from a handbook written by folks who

   purport to know such things). The last reliability

   study I witnessed in my career involved the mathematical

   analysis of all the pieces and parts that went

   into the fabrication of a super-sonic target

   we were building for the Navy . . .



  http://www.ordnance.org/aqm37c.htm



   We expended perhaps 1000 man-hours compiling

   the data and publishing a report. I don't recall

   now what the numbers were. I don't put much

   credence in such activities. They are 

   exercises in bureaucratic process that make

   bureaucrats happy . . .. and they paid us

   for it!

   

   Bottom line is that most such systems, if they

   are crafted with legacy products by skilled

   workers and screened for defects at time

   of manufacture will perform as advertised

   with low risk of failure. There's that

   non-quantified "low" thing again.



   But suppose Eggenfellner spent $100,000 and

   produced a detailed reliability study of the

   system as installed per his instructions

   posted at:



  http://www.eggenfellneraircraft.com/electrical.htm



   Suppose further that he offered a number

   of 1.6 failures per million flight hours.

   How would you use that number? If you have

   competing suppliers and the other guy says

   his gizmo has only 0.8 failures per million

   flight hours, would you pay double the cost

   to get double the "reliability"?



   Further, the past week's discussion on a

   Subaru powered RV-10 crash vividly illustrates

   that a system with 1 failure per trillion

   flight hours isn't worth beans if you don't

   craft power sources with similarly impressive

   numbers.

  	  Quote: 	
		    

 What is the answer for this?  Simply accept it and increase the pucker factor? 	


   Being a diligent observer of demonstrated service

   history is a good place to start. I've been

   chastised soundly on this List for suggesting

   that my observations of B&C's return products

   was not a proper expression of "reliability".

   I was able to offer from first hand experience

   that with thousands of devices in service, his

   return rates were on the order of 1-2 units

   per month for repair of user induced damage.

   I observed no returns for failure of the

   product.



   Not being inclined to spend $100,000 on a formal

   reliability study, I suggested that those

   observations were encouraging . . . especially

   since we knew how to produce failure tolerant

   systems that did not depend on a functioning

   alternator for comfortable termination

   of flight.  



  	  Quote: 	
		    

 Also, I think that I have seen Bob mention that he might be publishing a Z-19 modification, specific to the Egg requirements and also some potential pre-flight checklist recommendations for Z-19 and perhaps other designs,  Has this been done and I have missed it? 	


   Some years ago I had some discussion with

   Eggenfellner about a product-specific Z-figure.

   I don't remember details of the conversation

   now except that the idea was not received with

   enough enthusiasm for the project to move 

   forward.



   The Eggenfellner website gives us lip-service

   for a resource on technique but includes a

   statement, "Avoid being lured into thinking that

   you can create your own alternative to the EXPBUS

   and save time and money."



   I've studied the EXPBUS (and similar products)

   and written about them extensively. It's easy

   to demonstrate that they DO NOT save money.

   You can search aeroelectric.com for those

   discussions.



   At the same time, Eggenfellner's instructions are

   painstakingly crafted and well illustrated. I have no

   first hand knowledge as to how many of these

   systems are flying nor do I know the history

   of field service problems. Queries to the various

   Lists have to be your most useful places to

   put a dipstick into tribal knowledge. But

   be aware that while dark-n-stormy night stories

   abound in aviation, few tellers of such stories

   understand the simple ideas nor do they always

   have access to the facts of reported failures.



   While there are things in the Eggenfellner

   design I would not embrace, it's his kitchen,

   his recipe for success, and his reputation

   on the line. If you want to go the Z-19 route,

   then let's talk about it here on the list

   and tap the grey matter and experience of the

   membership. 

   

   So what ever stories you uncover, bring them

   to the AeroElectric List for the assistance

   of many minds who are skilled at sifting 

   significance out of the noise.



   Given the demonstrated service history of 

   automotive engine controllers (in environments

   much more stressful than under your cowl)

   I'll suggest that concerns for the hardware

   are probably not well founded. These pieces

   of hardware perform long and hard for 

   thousands of hours over the lifetime of

   the vehicle. It is more likely that your

   unhappy day in the cockpit will arise from

   failure to exercise due diligence in the

   crafting or maintaining your electrical system . . .

   or still more likely from venturing into

   a flight situation beyond the abilities

   of you or your airplane.



   There are plenty of nice ol' Lycomings out

   there with a huge history of demonstrated 

   performance that doesn't seem to discourage

   many of our ranks from launching into the blue

   behind them.



   Bottom line is that the risks are never

   zero. We can only do our best to mitigate

   those risks to acceptable levels. If you're

   really worried about it . . . then don't do it.

   A worried pilot with a good system is probably

   at greater risk than a skilled and thoughtful

   pilot with a mediocre system. Your likelihood

   of walking away from an unplanned arrival

   with the earth has little to do with reliability

   numbers and a lot to do with how you approach

   duties as pilot, designer and maintainer of

   the airplane.  This fact has been demonstrated

   countless times throughout the history of aviation.



   This is why accident rates for OBAM aircraft

   are pretty much in step with accident rates in

   TC aircraft. Both sets of pilots run off the same

   runways, fly into the same mountains, run the

   same batteries to destruction . . .  or fail to

   tighten the same oil drain plug.



   Bob . . .    [quote][b]

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

deej(at)deej.net
Guest

Posted: Mon Jun 29, 2009 7:52 am Post subject: Electric dependent Engine - Pucker Factor?

On 6/29/2009 11:26 AM, Robert L. Nuckolls, III wrote:



 	  Quote: 	
		     But suppose Eggenfellner spent $100,000 and

   produced a detailed reliability study of the

   system as installed per his instructions

   posted at:

 

 http://www.eggenfellneraircraft.com/electrical.htm


	




	Just fyi, those are an older set of wiring instructions for the

Eggenfellner package.  The latest instructions can be found at



<http://www.eggenfellneraircraft.com/ESeriesInstallationGuide.pdf>



starting on page 45 with other references for the package at

<http://www.eggenfellneraircraft.com/iindex.htm>



 	  Quote: 	
		     The Eggenfellner website gives us lip-service

   for a resource on technique but includes a

   statement, "Avoid being lured into thinking that

   you can create your own alternative to the EXPBUS

   and save time and money."


	




	Please note that the current wiring instructions are quite different

from the old, and do not include the EXPBUS.  Refer to page 51 for a

schematic.



fyi



-Dj



-- 

Dj Merrill - N1JOV

Sportsman 2+2 Builder #7118 N421DJ

http://deej.net/sportsman/



"Many things that are unexplainable happen during the construction of an

airplane."  --Dave Prizio, 30 Aug 2005

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

Display posts from previous:

	Matronics Email Lists Forum Index -> AeroElectric-List	All times are GMT - 8 Hours
Page 1 of 1

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum