Received-SPF: none
 receiver=logan.com; client-ip=68.230.241.27; envelope-from=dale.r@cox.net
From: Dale Rogers <dale.r@cox.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: [FlyRotary] Re: Rotary risks
Date: Sat, 4 Jun 2005 11:37:50 -0400
MIME-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Message-Id: <20050604153750.ENNN550.fed1rmmtao12.cox.net@smtp.west.cox.net>

Al Wick <alwick@juno.com> wrote:

> Sorry for being so long winded, I have the impression that stuff like
> this haven't been discussed before.

   Actually, most of the application related part has - at 
various times.  A couple of weeks ago, Leon posted pictures 
of a 12A front cover designed for two distributors - "Twin 
Dizzies" (apparently also suitable for twin CAS units).  
There's been discussion of ways to "stack" dual pickups on 
a single shaft; and some other on adding a CPS/CAS on either 
the flexplate or on the crank pulley.  We've long acknowledged 
that an *ideal* system would have true redundancy.

   Then again, is this where our inventive efforts would 
yield the most value, at this time?  So far, it seems that 
the Mazda CAS is one of the _least_ vulnerable of the engine 
management components.  

   So far, the most fragile parts of the system have turned 
out to be the intake and fuel systems.  So that is where a 
lot of attention has been, of late.

My $.002 (.02, after 35 years of inflation)

Dale R.                              (___
COZY MkIV-R13B #1254          |----==(___)==----|     
Ch's 4, 5, 16 & 23 in progress      o/ | \o


> From: al p wick <alwick@juno.com>
> Date: 2005/06/04 Sat AM 10:43:11 EDT
> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
> Subject: [FlyRotary] Re: Rotary risks
> 
> First, let's try to get a perspective. 
> There is no job as creative as that of Design Engineer. This guy is
> making hundreds of decisions. How many inputs do I need, what size
> resistor, how wide should that track be, how do I isolate that from
> vibration, etc etc. It's a very very high risk activity. So easy to
> overlook something. Many of the decisions are arbitrary. You are just
> making your best guess. 
> 
> The Japanese produce superior products. When we analyzed their success 30
> years ago, we found they used certain tools in the design and validation
> phase that U.S. designers didn't. One of these is the FMEA (see web
> site). They get a group of engineers together and say" Ok, this is our
> best guess on how it should be designed, what's going to fail?". They go
> thru each characteristic and rate them for risk. Then they find a way to
> prove how far from failure each of those items are.
> For example, they'll say"Ok, the alternator is going to fail. This will
> produce an ac voltage." So then they measure how large the ac voltage can
> get before the device dies. Then they take action if there is not a large
> safety margin, retest. They end up with numbers that measure their safety
> margin.
> 
> So I would encourage reviewing all the various failure modes of the ECM.
> Deliberately subject it to experiences beyond what it will normally see.
> Unplug each sensor, see how it handles it. Apply heat way beyond normal,
> apply vibrations beyond normal. There are very simple ways to do this. It
> doesn't have to be some long drawn out thing. 
> 
> However, statistically, we know if you have true redundancy in this
> particular device, then you get to multiply the probability of failure.
> So if the probability of shut down is 1 time in 1000 hours, since we have
> two with independent probabilities, our odds plummet to 1 time in 1
> million hours. So all you need are two independent circuits. 
> When in doubt, just take a look at what the auto designers have done.
> They use more than one sensor to measure each characteristic. They
> compare the sensor results to historical data. They instantly recognize
> the sensor is providing false data, then warn you, and use tables or
> other sensor to keep you plugging along. That's why you don't see
> vehicles sitting on the side of the road.
> 
> Sorry for being so long winded, I have the impression that stuff like
> this haven't been discussed before.
> 
> 
> -al wick
> Artificial intelligence in cockpit, Cozy IV powered by stock Subaru 2.5
> N9032U 200+ hours on engine/airframe from Portland, Oregon
> Prop construct, Subaru install, Risk assessment, Glass panel design info:
> http://www.maddyhome.com/canardpages/pages/alwick/index.html
>