Message-ID: <19981009192550.3918.qmail@www05.netaddress.usa.net>
Date: Fri, 09 Oct 1998 19:25:50
From: Dan Schaefer <dfschaefer@usa.net>
To: lancair.list@olsusa.com
Subject: wire marking, fuel systems, bug squashing
Mime-Version: 1.0

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In reference to Jeff Chipestine's info about the Sharpie "permanent" pen fading
over time - Rats!! now I'm going to have to dig around behind my panel to see if
I can still read my labeling. Guess that's what I get for believing advertising
claims without checking. The comment by Jim Michaels about adding a clear shrink
tube over a mark sounds like a good idea as the ink probably oxidizes over time
- too late for me but a great idea for those who have yet to do their wiring. By
the way, we use the wire etching/marking machines here at the bomber factory but
the machines are hellishly expensive to set up and operate, let alone acquire.
And unless you know what you want marked on every wire segment, in advance,
(unlikely) you're going to have to resort to hand marking the odd renegade
segment anyway so you might as well hand mark 'em all. Further, if you're going
to use the little vinyl number tags that wrap around the wire, (used to be
called "Brady Markers" and some of the older guys at the electronics store will
know what you mean if you ask for them) you better put a shrink tube over those
too, or you'll find them all on the floor of your airplane in a year or two.
There's quite a number of brands now and I think the late-comers to the field
haven't bothered to use very good adhesives.

To continue the discussion on fuel systems. I, like most of the 235 and 3x0
builders/flyers, use two transfer pumps to get fuel from the wings to the
header. In the course of flying N235SP for over 450 hours, I have experienced
two failures of Facet electric pumps. At the time of the first failure, I had
only a single transfer pump plumbed in following the wing tank selector valve. Since
I always keep the header full (it holds approx. 11 gals), it was a
non-event, but I do not like single-point failures in critical systems so I
added a second pump in series with the first for redundancy. Note that I don't
use one pump for each wing, which would mean a pump failure would make that fuel
unavailable. I added the second unit in series with the first one, still
following the selector valve. They're wired in parallel to the same switch so
they're both powered at the same time. I did this because these pumps have a
"pump-thru" feature even if it fails or is turned off (as when used for the
boost pump). I'm still carrying two pumps, but the system has gained a measure
of redundancy (safety) and all fuel on board is still available following a
single failure. And the Reliability guru's around here base a lot on the premise
that two failures, in the same system, on the same flight, has a vanishingly
small probability. I guess it's why we automatically include a back-up pump for
the mechanical one on the engine and it's usually "on" near the ground, like for
takeoff and landing. Works for me!

The post about bug smashing brought to mind a very interesting ocurrence during a flight I made last June.  (It got my attention anyway, because I was flying alone, over some of the most desolate desert mountains in southwestern Neveda.) I had just taken off from the Tonopah, NV airport where I had stopped for fuel. As I climbed out on my way to 9500 ft, I flew through what looked like a very faint cloud. Actually looked like a puff of smoke, but I could see through it so didn't think much about it. When I reached my cruise altitude and went to reflex and set RPM, I quickly noticed that my indicated airspeed was down from what I was used to by around 15 MPH. The airplane felt "doggy" - hard to define, but suffice to say, I was not comfortable with the was things were going right then. Since early on, during the shake-down phase, my nose-gear door had occasionally closed before the wheel came up, trapping the wheel partially out in the slip-stream (since fully corrected) I thought that maybe it had happened again and it was slowing me down. I slowed to gear speed and recycled the gear a couple of times but had absolutely no indication of the hang-up or any improvement. Since all else was going OK, I elected to continue to home base. (Not really much choice, given where I was at the time). Anyway, the long and the short of it was that the problem came from that funny looking cloud I ran through - when I landed and took a close look at the wings, they were COVERED with tiny bugs. It looked and felt like someone had spread glue on the forward half of the wing and then taken a pepper shaker to it. The surface felt like about medium sandpaper. After a about 30 minutes of scrubbing with liberal spritzes of Formula 409 they all came off. A quick flight showed that the cruise speed was back to normal once N235SP was off it's high protein diet.  From this experience, I hereby acknowlege the efficacy of laminal flow airfoils and the consequences of getting kicked out of the drag bucket. I include this here so you'll know
Cheers,

Dan Schaefer


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