kerrjohna(at)comcast.net
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 Posted: Fri Jul 14, 2006 6:50 am Post subject: Tachometers. was Rotax 532 a Boat Anchor |
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Dave, the tach that came with my 912/Classic IV as a tendancy to "drift". For the past year I have been concerned that I was loosing power with only 700+ hours. I could not get 5200 rpm on take off and was left with reducing pitch.
As part of the most recent condition inspection I check rpm against an optical tach, which is easily tested with an incandescent bulb, and found that the tach was reading about 400 rpm low. I recalibrated the tach with a small nylon screw driver from the rear and returned the pitch to the 17* used since the beginning flights.
Recent experience and posts on this list confirm that most of our problems with out equipment are pilot/maintenance induced:
1. incorrectly gapped plugs
2.wiring not protected from vibration
3.prop hubs over torqued.
4.starter attachment not per specs
5.after market component failure
6.carburator not adjusted per specs
7.redesigned fuel system
8.etc
Home builders are sometimes "cowboys" that are trying to avoid the "overbearing" regulatory confines of certified a/c operation. One reason there are fewer failures in certified airplanes is the regulator confines that provide an accurate check on our rides. But then there are the certified a/c owners who seek out soft a/ps to get there annual "paper-whipped" in case of a ramp check.
I guess my philosophy of "flying to support my building habit" might offer a page to everyone in experimental airplanes. If you don't love the process of checking all the adjustments/torques repeatedly your experience may not be as rewarding as hoped.
John Kerr
"I have been on a soap box in Hyde Park too"
[quote]-------------- Original message --------------
From: "Dave" <dave(at)cfisher.com>
[quote] --> Kitfox-List message posted by: "Dave"
Bradley,
Thank you for the explanation of events leading up to the incident.
Now am I reading this correctly ? The starter drive did not dis-engage?
First indication should have been after applying WOT that 5400 that
something was not right .
I would only guess that at 5400 instead of the proper 6200 rpm on a 582 that
you would have only been getting about 45 to 50 hp instead of the 64 hp that
a 582 is supposed to put out.
25% less power on take off would be critical at gross in most aircraft.
So the Rotax engine was in fact not the culprit but the denzo starter gear ?
Also I will add that on th e rear mounted starters on 582 it is imperative
that the starter be tightened to allow for a 1mm gap at starter housing (
about .040") as it is rubber mounted with a series of o-rings giving it the
shock absorption. Too tight and the read housing will fail and cost you over
300 $ for a new one. The Starter drive is also near 100$ .
Fortunately your fine piloting skills brought your plane back in one piece.
Another example of why it is important to make sure you are getting full
power on Takeoff.
Now let me throw in something else. Rotax Tachs. I recently put in a tiny
tach as I have heard that they are very accurate and perhaps more so than
the Rotax tach. Well Guess what, my tiny tach reads about 600 to 800 rpm
higher at WOT than does the Rotax tach. Could it be a problem in the gray
wire coil on the rotax or that Rotax tach or is the tiny tach accurate.? < BR>> ;
Dave
PS -- I do wish you great success on your GEO install and am anxiously
awaiting to see some performance numbers.
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