Today's Message Index:
----------------------
1. 01:09 AM - Re: europa list mod 74 (Carl Pattinson)
2. 01:14 AM - Re: Europa list mod 74 (Carl Pattinson)
3. 01:17 AM - Re: Mod 74 (Carl Pattinson)
4. 01:22 AM - Re: Dynon (Laptop JR)
5. 03:02 AM - Re: Pip pins (John Price)
6. 04:48 AM - ANR Headsets (TELEDYNMCS@aol.com)
7. 07:04 AM - Re: Europa Mod 74 (Roger Bull)
8. 07:52 AM - Re: Europa Mod 74 (Pete Lawless)
9. 09:12 AM - Re: Europa Mod 74 (Carl Pattinson)
10. 09:49 AM - Re: Europa accident G-HOFC - PFA comment (Simon Smith)
11. 10:03 AM - Europa Mod 74 (Fred Klein)
12. 11:12 AM - Re: Europa Mod 74 (Pete Lawless)
13. 01:42 PM - noise-cancelling mic [was: anr headsets] (Rowland & Wilma Carson)
14. 03:15 PM - Re: noise-cancelling mic [was: anr headsets] (Fred Klein)
15. 06:13 PM - Re: Europa accident G-HOFC - PFA comment (Finklea)
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Subject: | Re: europa list mod 74 |
Apologies for the misleading comment - I hadnt read the Europa Tech Talk
when I wrote that.
It seems events have overtaken me here.
>
>> One aspect of Mod 74 (yet to be decided) is that it may
>> incorporate a tie bar similar to the weight increase
>> mod - or the present weight increase mod may become
>> mandatory. There is a question mark over the effectiveness of the top hat
>> stiffeners currently
>> specified in the older Europas (without tie bars).
>
> I am sure it is decided as Mod 74 is now published with
> the need for a tie bar if you don't have Mod 52.
>
> The access hole in the Mod is 2 1/4 inches
>
> RH
>
>
>
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Subject: | Re: Europa list mod 74 |
Hi Tim,
I had the same thought - the answer is almost certainly NO !
Theres a lot more work/ parts involved in Mod 52 - unfortunately.
I think its probably better to do Mod 52 if possible first. We are intending
to fit a VP prop shortly so Mod 52 is a must for us anyway.
Probably wait till the winter (assuming that isnt NOW) and get all these
jobs out the way in one go).
Regards
Carl & Dot
----- Original Message -----
From: <houlihan@blueyonder.co.uk>
Sent: Saturday, July 28, 2007 12:06 AM
Subject: Re: Europa-List: Europa list mod 74
>
> My reading of the info on the Europa web site is that a Classic when
> fitted with mod 74 including the tie bar but not the rest of the mod 52
> will not have its weight increase to 1370 lbs.
> This seems odd to me but that is the way I read it.
>
> Any way to get the weight up 1370 lbs without doing first mod 52 and then
> mod 74 ?
>
> Tim Houlihan
> G-BZTH
>
>>
>>> I have seen the work on the only Europa which has
>>> undergone Mod 74 courtesy Andy Draper. We asked the
>>> same question and the feeling is there isnt enough room
>>> to get a spanner around the securing nut to tighten it
>>> - its a lot easier through the wing underside.
>>
>>> The access hole is about 1.5" diameter and the repair
>>> afterwards extends to about 9" square. As its on the
>>> underside it has little effect on the aerodynamics of
>>> the wing and is easy to conceal.
>>
>>> My understanding is the PFA will consider an
>>> alternative means of access and someone is looking into
>>> this.
>>
>>> One aspect of Mod 74 (yet to be decided) is that it may
>>> incorporate a tie bar similar to the weight increase
>>> mod - or the present weight increase mod may become
>>> mandatory. There is a question mark over the
>>> effectiveness of the top hat stiffeners currently
>>> specified in the older Europas (without tie bars).
>>
>> I am sure it is decided as Mod 74 is now published with
>> the need for a tie bar if you don't have Mod 52.
>>
>> The access hole in the Mod is 2 1/4 inches
>>
>> RH
>>
>>
>>
>>
>>
>>
>
>
>
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Looks like that just doubled (100) !
GROAN
----- Original Message -----
From: "Carl Pattinson" <carl@flyers.freeserve.co.uk>
Sent: Friday, July 27, 2007 10:48 PM
Subject: Re: Europa-List: Mod 74
>
> No one likes having to shell out for mandatory mods but fifty quid for a
> safer aircraft sounds like a bargain to me.
>
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Dear Tony
Is this code going to be transferable to others fitting the D180 and other
Dynons please?
JR (Bob) Gowing UK Kit 327 in Oz
----- Original Message -----
From: "Tony Krzyzewski" <tonyk@kaon.co.nz>
Sent: Thursday, July 12, 2007 9:03 AM
Subject: RE: Europa-List: Dynon
>
>
>>>> Tony, it's out now, looks good too.....
>
> I've just downloaded it and now have to wait until the end of my day so
> I can go home and upload it to the D180!
>
> I'm just working on a code change which will permit my fuel gauge sender
> to be used as an input into the D180 - in effect making my sender
> emulate a capacitance probe. Dynon have been really helpful with getting
> me information on how their inputs are designed which has made my job
> much easier.
>
> Tony
>
>
>
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Thanks Richard,
Mine arrived today
John Price.
----- Original Message -----
From: "Richard Holder" <rholder@avnet.co.uk>
Sent: Friday, July 27, 2007 7:06 PM
Subject: Europa-List: Pip pins
>
> To all those who ordered pip pins and sent me envelopes
> - they are on their way to you ! Please let me know when
> they arrive.
>
> They fitted OK on mine !
>
> Richard Holder
> G-OWWW High Cross, ungrounded as of today (for 10 hours !)
>
>
>
>
>
>
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In a message dated 7/28/2007 2:58:40 AM Eastern Daylight Time,
europa-list@matronics.com writes:
I have a couple of Lightspeed 15xc's which work just fine. At $350 USD,
the price wasn't bad, either. Don't know if they are still available,
though...
Hey Jeff,
I will echo what you've said about Lightspeed. I have a set of 20XL's and
I've been using them almost daily for about 5 years now. They were under
$400/ea from Spruce. I've used them both with the Europa/Jabiru and the
Ximango/Rotax and they work equally well. I've also used them in a Pawnee, Citabria,
C-210, Navion and a T-6 excellent results. Battery life for the ANR seems to be
in excess of 40 hours on two AA batteries. I once broke part of the earpiece
after sitting on it and Lightspeed sent replacement parts at no charge.
My only gripe is the audio quality from my XM radio isn't the best, IOW, not
enough bass response. However, after looking at the schematic for my
Flightcom intercom, the lack of bass in the audio probably has more to do with
the
size of the capacitors they used in the intercom as opposed to a problem with
bass response in the the 20XL's. I would highly recommend Lightspeed headsets.
Regards,
John Lawton
Whitwell, TN (TN89)
N245E - Putting the pieces back together after annual inspection
************************************** Get a sneak peek of the all-new AOL at
http://discover.aol.com/memed/aolcom30tour
Message 7
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I think I should point out that Mod 74 does not call for Mod 52 to be
incorporated if not already done so; the requirement is to fit a tie bar to
the existing rear wing pin sockets, the tie bar being part of Mod 52 as
well. Builders can of course fit Mod 52 in its entirety, which, plus the
new pin arangement in the wing, will satisfy Mod 74.
We at Europa were unaware until earlier this week that the tie bar would be
required, so it has been a rush to get the parts as soon as possible. If
builders want to incorporate Mod 52 in its entirety the lead time will be
longer, proably about 3 weeks, as it will be necessary to get extra supplies
of the 3 part wing socket included in that Mod.
Getting out the Mod leaflet, sorting out the logistics, etc. has been a bit
of a nightmare, so I would be extremely grateful if Richard Holder would
come and take over the company - he would undoubtedly be able to offer a
better and cheaper service, and then John and I would be able to retire on
our (non-existent) ill gotten gains!
Regards,
Roger
-----Original Message-----
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com]On Behalf Of David.Corbett
Sent: 27 July 2007 7:10 pm
To: Europa Forum ; Europa committee
Subject: Europa-List: Europa Mod 74
Europhiles everywhere - Francis Donaldson has asked me to advise you all
that Europa Mod 74 is now on the Europa 2004 Ltd website, under Technical
and then Modifications. There is a very strict time limit - within 10 hours
from 1 August 2007. Mod 74 affects classic aircraft with foam-filled wings;
those classic aircraft that do not already have Mod 52 (the weight increase
mod) will be required to fit Mod 52 as part of Mod 74.
As it is Friday evening here, I cannot check with Roger Bull to find out
what the lead time is going to be for the parts; but I am copying this to
him, and hope that, in order to save every one of us ringing him, he will
put a short statement on this forum to advise likely delivery availability.
I will also be forwarding to the forum, within a few minutes, a copy of an
e-mail written by Francis to Ted Gladstone setting out the PFA's view of the
accident sequence; this is not a definitive account - that can only be
issued by UK AAIB. However, Francis's e-mail does give the reasoning behind
the decisions to issue the MPD's and now the Mods.
David, on behalf of PFA EC and Europa Club
G-BZAM
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Hi Roger
You guys working on a Saturday - now that is what I call service and
should
qualify for at least double time! No complaints from me regarding the
costs
or the speed of response to our joint problems - and I am sure the
majority
of owners feel the same.
Just out of interest is there a lead time should I decide to do a full
mod
52 instead of the new tie bar arrangement in Mod 74.
Kind regards
Pete
-----Original Message-----
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com] On Behalf Of Roger Bull
Sent: 28 July 2007 15:11
Subject: RE: Europa-List: Europa Mod 74
I think I should point out that Mod 74 does not call for Mod 52 to be
incorporated if not already done so; the requirement is to fit a tie bar
to
the existing rear wing pin sockets, the tie bar being part of Mod 52 as
well. Builders can of course fit Mod 52 in its entirety, which, plus
the
new pin arangement in the wing, will satisfy Mod 74.
We at Europa were unaware until earlier this week that the tie bar would
be
required, so it has been a rush to get the parts as soon as possible.
If
builders want to incorporate Mod 52 in its entirety the lead time will
be
longer, proably about 3 weeks, as it will be necessary to get extra
supplies
of the 3 part wing socket included in that Mod.
Getting out the Mod leaflet, sorting out the logistics, etc. has been a
bit
of a nightmare, so I would be extremely grateful if Richard Holder would
come and take over the company - he would undoubtedly be able to offer
a
better and cheaper service, and then John and I would be able to retire
on
our (non-existent) ill gotten gains!
Regards,
Roger
-----Original Message-----
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com]On Behalf Of
David.Corbett
Sent: 27 July 2007 7:10 pm
Subject: Europa-List: Europa Mod 74
Europhiles everywhere - Francis Donaldson has asked me to advise you all
that Europa Mod 74 is now on the Europa 2004 Ltd website, under
Technical
and then Modifications. There is a very strict time limit - within 10
hours
from 1 August 2007. Mod 74 affects classic aircraft with foam-filled
wings;
those classic aircraft that do not already have Mod 52 (the weight
increase
mod) will be required to fit Mod 52 as part of Mod 74.
As it is Friday evening here, I cannot check with Roger Bull to find out
what the lead time is going to be for the parts; but I am copying this
to
him, and hope that, in order to save every one of us ringing him, he
will
put a short statement on this forum to advise likely delivery
availability.
I will also be forwarding to the forum, within a few minutes, a copy of
an
e-mail written by Francis to Ted Gladstone setting out the PFA's view of
the
accident sequence; this is not a definitive account - that can only be
issued by UK AAIB. However, Francis's e-mail does give the reasoning
behind
the decisions to issue the MPD's and now the Mods.
David, on behalf of PFA EC and Europa Club
G-BZAM
href="http://www.matronics.com/Navigator?Europa-List">http://www.matron
href
"http://forums.matronics.com">http://forums.matronics.com
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Subject: | Re: Europa Mod 74 |
14 Hantone HillHi Roger,
I second Petes response and I would be happy to come and run the company
but you would probably want me to work for free (just as RH expects you
to).
I think we will ultimately opt for Mod 52 but not until the rush is
over. I doubt we will get through the allowed 10hrs before the year is
over if the present weather continues (today excepted).
You dont offer a submarine conversion for the Europa by any chance.
Keep up the good work.
Regards,
Carl Pattinson.
----- Original Message -----
From: Pete Lawless
To: europa-list@matronics.com
Sent: Saturday, July 28, 2007 3:50 PM
Subject: RE: Europa-List: Europa Mod 74
Hi Roger
You guys working on a Saturday - now that is what I call service and
should qualify for at least double time! No complaints from me
regarding the costs or the speed of response to our joint problems - and
I am sure the majority of owners feel the same.
Just out of interest is there a lead time should I decide to do a full
mod 52 instead of the new tie bar arrangement in Mod 74.
Kind regards
Pete
-----Original Message-----
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com] On Behalf Of Roger Bull
Sent: 28 July 2007 15:11
To: europa-list@matronics.com
Subject: RE: Europa-List: Europa Mod 74
I think I should point out that Mod 74 does not call for Mod 52 to be
incorporated if not already done so; the requirement is to fit a tie bar
to the existing rear wing pin sockets, the tie bar being part of Mod 52
as well. Builders can of course fit Mod 52 in its entirety, which, plus
the new pin arangement in the wing, will satisfy Mod 74.
We at Europa were unaware until earlier this week that the tie bar
would be required, so it has been a rush to get the parts as soon as
possible. If builders want to incorporate Mod 52 in its entirety the
lead time will be longer, proably about 3 weeks, as it will be necessary
to get extra supplies of the 3 part wing socket included in that Mod.
Getting out the Mod leaflet, sorting out the logistics, etc. has been
a bit of a nightmare, so I would be extremely grateful if Richard Holder
would come and take over the company - he would undoubtedly be able to
offer a better and cheaper service, and then John and I would be able to
retire on our (non-existent) ill gotten gains!
Regards,
Roger
-----Original Message-----
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com]On Behalf Of
David.Corbett
Sent: 27 July 2007 7:10 pm
To: Europa Forum ; Europa committee
Subject: Europa-List: Europa Mod 74
Europhiles everywhere - Francis Donaldson has asked me to advise you
all that Europa Mod 74 is now on the Europa 2004 Ltd website, under
Technical and then Modifications. There is a very strict time limit -
within 10 hours from 1 August 2007. Mod 74 affects classic aircraft with
foam-filled wings; those classic aircraft that do not already have Mod
52 (the weight increase mod) will be required to fit Mod 52 as part of
Mod 74.
As it is Friday evening here, I cannot check with Roger Bull to find
out what the lead time is going to be for the parts; but I am copying
this to him, and hope that, in order to save every one of us ringing
him, he will put a short statement on this forum to advise likely
delivery availability.
I will also be forwarding to the forum, within a few minutes, a copy
of an e-mail written by Francis to Ted Gladstone setting out the PFA's
view of the accident sequence; this is not a definitive account - that
can only be issued by UK AAIB. However, Francis's e-mail does give the
reasoning behind the decisions to issue the MPD's and now the Mods.
David, on behalf of PFA EC and Europa Club
G-BZAM
href="http://www.matronics.com/Navigator?Europa-List">http://www.matron
href="http://forums.matronics.com">http://forums.matronics.com
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Subject: | Europa accident G-HOFC - PFA comment |
Francis's e-mail seems to suggest the opposite sequence of events to that
given by the AAIB in S3/2007.
If the tailplane moved as a result of the wing detachment is it known for
certain that the TP6 was already detached or did the wing cause that too?
Have we all just modified our aircraft for no reason?????
Simon
_____
From: Francis Donaldson [mailto:francis.donaldson@pfa.org.uk]
Sent: 27 July 2007 10:33
Cc: Andy Draper
Subject: RE: Europa statement
Dear Alan
Following our discussion I have decided not to issue a PFA statement about
the Europa accident, for the reasons you suggested. However instead I would
like your agreement to sending the e-mail below to individuals who e-mail us
speculating about the accident sequence. Is this OK ?
Francis Donaldson
Dear Ted
Thanks for the copy e-mail. The reason why the rear wing pin pulled out of
the right wing was almost certainly because the construction of the hard
point in the root rib was defective, the laminations of the plate were
staggered so that the threaded hole was not through the middle of the metal
plates as designed. It was near the edge of the first one and penetrating
the edge of the underneath ones, ie only the first laminate would have been
able to carry significant load. This is why the outer laminate ripped out.
I think that release of the rear wing attachment allowed the right wing to
swing forward and split the right wing spar, causing the right wing to break
up and tearing the pins out retaining the other wing in the process. The
massive jerk caused by the wing failure would explain what moved the right
tailplane off its pitch pins and allow it to flutter and depart, and the
left tailplane could have fluttered and then departed because in moving
outboard, the right tailplane had dragged the anti-balance tab operating
tee-bar off the pin on the left tailplane's anti-balance tab.
Had the main wing pins failed, there would not have been the massive damage
to the right wing which occurred, as failure of the pin would immediately
off-load the wings.
Both crew were found with the cockpit wreckage, there was no question of
either falling out of the aircraft in flight.
We are taking what we see as appropriate steps to allow the Europa fleet to
carry on flying, with a acceptable level of safety. If we wait for the AAIB
report to be published in full, we would have to ground the fleet meanwhile,
which could last many months.
The work on the root pin attachment does not involve a huge amount of work
or a massive hole in the skin, Andy has managed to devise a keyhole surgery
approach. It has been tried on a sample Europa and went OK.
Please note that the above is our present line of thought about the accident
sequence but is not yet definitive, that will be the prerogative of the AAIB
and their final report. There is further testing to be done to test the
theory, which we are helping AAIB to prepare. Please do not broadcast the
above on the Europa net or elsewhere as it would not be appropriate to
promulgate the present theory in advance of the AAIB report.
Best regards
Francis Donaldson
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I appreciate the gentile restraint of Roger Bull's post almost as much
as I appreciate the value of Mod 74 as a measure of the analysis and
clear documentation prepared by the folks at E04 to enhance the
integrity of our fleet and the Europa brand rather than simply the
measure of the cost of bagging and shipping a few pieces of hardware.
Fred
A194
do not archive
On Saturday, July 28, 2007, at 07:11 AM, Roger Bull wrote:
> I think I should point out that Mod 74 does not call for Mod 52 to be
> incorporated if not already done so; the requirement is to fit a tie
> bar to the existing rear wing pin sockets, the tie bar being part of
> Mod 52 as well.- Builders can of course fit Mod 52 in its entirety,
> which, plus the new pin arangement in the wing, will satisfy Mod 74.
> -
> We at Europa were unaware until earlier this week that the tie bar
> would be required, so it has been a rush to get the parts as soon as
> possible.- If builders want to incorporate Mod 52 in its entirety the
> lead time will be longer, proably about 3 weeks, as it will be
> necessary to get extra supplies of the 3 part wing socket included in
> that Mod.
> -
> Getting out the Mod leaflet, sorting out the logistics, etc. has been
> a bit of a nightmare, so I would be extremely grateful if Richard
> Holder would come and take over the company - he would undoubtedly be-
> able to offer a better and cheaper service, and then John and I would
> be able to retire on our (non-existent) ill gotten gains!
> -
> Regards,
> -
> Roger
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Roger
Having answered my own question re lead times by properly reading your
original email another question; is there any reason why Mod 74 could
not be
done straight away and then at a latter date the remaining work to fully
implement Mod 52 be completed. My concern would be that having
installed
the new wing pin for the existing fuselage sockets, will that then work
with
the new sockets required by Mod 52? Obviously if the adjustment of the
new
wing pin is required to subsequently implement Mod 52 then doing Mod 74
first would be a non starter.
Regards
Pete
-----Original Message-----
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com] On Behalf Of Roger Bull
Sent: 28 July 2007 15:11
Subject: RE: Europa-List: Europa Mod 74
I think I should point out that Mod 74 does not call for Mod 52 to be
incorporated if not already done so; the requirement is to fit a tie bar
to
the existing rear wing pin sockets, the tie bar being part of Mod 52 as
well. Builders can of course fit Mod 52 in its entirety, which, plus
the
new pin arangement in the wing, will satisfy Mod 74.
We at Europa were unaware until earlier this week that the tie bar would
be
required, so it has been a rush to get the parts as soon as possible.
If
builders want to incorporate Mod 52 in its entirety the lead time will
be
longer, proably about 3 weeks, as it will be necessary to get extra
supplies
of the 3 part wing socket included in that Mod.
Getting out the Mod leaflet, sorting out the logistics, etc. has been a
bit
of a nightmare, so I would be extremely grateful if Richard Holder would
come and take over the company - he would undoubtedly be able to offer
a
better and cheaper service, and then John and I would be able to retire
on
our (non-existent) ill gotten gains!
Regards,
Roger
-----Original Message-----
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com]On Behalf Of
David.Corbett
Sent: 27 July 2007 7:10 pm
Subject: Europa-List: Europa Mod 74
Europhiles everywhere - Francis Donaldson has asked me to advise you all
that Europa Mod 74 is now on the Europa 2004 Ltd website, under
Technical
and then Modifications. There is a very strict time limit - within 10
hours
from 1 August 2007. Mod 74 affects classic aircraft with foam-filled
wings;
those classic aircraft that do not already have Mod 52 (the weight
increase
mod) will be required to fit Mod 52 as part of Mod 74.
As it is Friday evening here, I cannot check with Roger Bull to find out
what the lead time is going to be for the parts; but I am copying this
to
him, and hope that, in order to save every one of us ringing him, he
will
put a short statement on this forum to advise likely delivery
availability.
I will also be forwarding to the forum, within a few minutes, a copy of
an
e-mail written by Francis to Ted Gladstone setting out the PFA's view of
the
accident sequence; this is not a definitive account - that can only be
issued by UK AAIB. However, Francis's e-mail does give the reasoning
behind
the decisions to issue the MPD's and now the Mods.
David, on behalf of PFA EC and Europa Club
G-BZAM
href="http://www.matronics.com/Navigator?Europa-List">http://www.matron
href
"http://forums.matronics.com">http://forums.matronics.com
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Subject: | noise-cancelling mic [was: anr headsets] |
At 2007-07-27 20:07 +0100 Carl Pattinson wrote:
>IMHO noise cancelling microphones dont seem to cancel out very much
>noise - maybe someone with a superior technical understanding might
>volunteer an explanation
Carl - they certainly don't work perfectly, but if you compared a
recording made with the usual aviation-type noise-cancelling mic
side-by-side with one made using a conventional microphone, I think
you would notice the difference! I know they do work; I use a
Sennheiser MD430 "close-talking" mic to record speech (for
announcements, etc) in normal domestic locations, and that frees me
from having to worry much about intrusion of external noises.
{As an aside, I recently swapped headsets with my instructor to try
out his ANR set. At first it didn't seem dramatically quieter than my
own Sennheiser HME 100, but switching the NC off & on again soon
convinced me that there was a big difference, particularly in the low
frequencies. Just being exposed to the engine noise while swapping
headsets had disturbed my own threshold enough to make the comparison
difficult to make. (Incidentally, we did this on the ground!) The
moral is that a direct comparison with a NON noise-cancelling mic
would be needed to judge the effectivenes of the noise-cancelling
mic.}
Many "noise-cancelling" microphones work on the principle of
accepting spherical pressure wave-fronts and rejecting planar
wave-fronts.
The idea is that a sound source very near the mic will produce a
spherical wave, expanding in all directions from the source. The
wave-front from a distant sound source will be much closer to a plane.
Designers take advantage of this in various ways, often involving
labyrinth construction, so that the pressure variations from plane
waves arrive at the transducer out of phase, and thus tend to cancel
out, whereas pressure variations from wavefronts differing
significantly from planar do not cancel and may actually achieve a
reinforcing effect. Of course the effectiveness of this will be quite
frequency-dependent.
MIcrophones of this type are uusually referred to as
pressure-gradient types; those which respond equally to sounds from
all directions and distances are called pressure (or omnidirectional)
types. The most common ype of pressure-gradient mic is the cardiod
(or unidirectional) type, typically seen on stage for singers or
announcers, which responds much more sensitively to sounds from the
front than from the back or sides. However, the standard cardiod is
not noise-cancelling; it will respond equally to all sounds arriving
along its axis of sensitivity. The true noise-cancelling mic is
rarer, and (apart from the ones in aviation headsets) the most likely
place to see one is on a PA system where the announcer is in the room
served by the sound system (eg at airports). It does require the
talker to be very close to the mic inn order to work properly. That's
why you need to get your headset mic as close to your mouth as
possible, but without putting it in the direct path of the breath
puffs from plosive sounds (words with syllables starting with P, B,
T, D etc). Hence the advice often seen to position the mic at the
corner of your mouth.
One of the finest examples of the noise-cancelling mic technique was
the STC 4104, sometimes referred to as the "Raymond Glendenning"
model because he was seldom pictured without one. It had a small pad
which was placed against the upper lip (or moustache as the case may
be) in use, thus ensuring accurate positioning of the lips in the
location intended by the designer. It was designed for radio use,
before the days of sound-insulated commentary boxes, but was latterly
also used by TV commentators on Saturday afternoons for reading the
football results live from a (very noisy) teleprinter. Very
occasionally one can be seen still, typically with a reporter wearing
ear-muffs and standing beside a running jet engine or other very
noisy artifact.
My own Telex 66C aviation mic (acquired way back before the universal
use of headsets, when I couldn't be sure the mic in the flying school
aircraft would always be working, and carried until recently as an
emergency backup) is very similar in principle, having a protruding
ridge that you can rest on your top lip for accurate positioning. It
also benefits from the slight non-linear sensitivity of the
carbon-granule transducer. (That's why old-fashioned phones with
carbon mics tended to discriminate in favour of the speech from the
user and somewhat attenuate lower-level sound, whether speech or
other; of course the carbon granules introduced lots of noise of
their own, but that's a different issue!)
I think the common approach for aviation headset boom mics now is to
have matching orifices front and rear, each communicating with
opposite sides of the transducer diaphragm. Thus plane pressure waves
(ie those from relatively far away) will tend to be displacing the
diaphragm both forwards and backwards at the same time, so cancelling
out. The distance from the talkers lips to the nearest orifice should
be of a similar scale to the air-path round to the orifice on the
other side of the mic. Thus (over a restricted frequency range) the
user's speech can generate positive pressure on the front of the
diaphragm, accompanied by a reduction in pressure at the back of the
diaphragm (and vice versa).
Sorry, this is probably much more info than anybody wanted, but hope
it helps to understand the principles.
regards
Rowland
--
| Wilma & Rowland Carson http://home.clara.net/rowil/
| <rowil@clara.net> ... that's Rowland with a 'w' ...
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Subject: | Re: noise-cancelling mic [was: anr headsets] |
...ah...the special joys of "matching orifices front and rear"...
do not archive
On Saturday, July 28, 2007, at 09:17 AM, Rowland & Wilma Carson wrote:
>
> I think the common approach for aviation headset boom mics now is to
> have matching orifices front and rear, each communicating with
> opposite sides of the transducer diaphragm. Thus plane pressure waves
> (ie those from relatively far away) will tend to be displacing the
> diaphragm both forwards and backwards at the same time, so cancelling
> out. The distance from the talkers lips to the nearest orifice should
> be of a similar scale to the air-path round to the orifice on the
> other side of the mic. Thus (over a restricted frequency range) the
> user's speech can generate positive pressure on the front of the
> diaphragm, accompanied by a reduction in pressure at the back of the
> diaphragm (and vice versa).
--
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Subject: | Re: Europa accident G-HOFC - PFA comment |
How many Europa deaths in how many months? 8 in 18 mos... I am concerned!!
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=126081#126081
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