Today's Message Index:
----------------------
1. 06:58 AM - Re: Switch source (Kevin Horton)
2. 09:00 AM - Re: Re: Tach pickup (Robert L. Nuckolls, III)
3. 09:03 AM - Re: Tach pickup (Robert L. Nuckolls, III)
4. 09:07 AM - Re: Re: Tach pickup (Robert L. Nuckolls, III)
5. 01:14 PM - Pitot Current Draw (Chuck Jensen)
6. 02:05 PM - Re: Pitot Current Draw (Richard E. Tasker)
7. 03:52 PM - Dumb questions (Gilles Thesee)
8. 04:05 PM - Re: Tach pickup (Bob White)
9. 04:31 PM - Re: Tach pickup (N777TY)
10. 05:59 PM - Re: Pitot Current Draw (Lynn Riggs)
11. 07:03 PM - Re: Pitot Current Draw (OldBob Siegfried)
12. 08:32 PM - Re: Pitot Current Draw (Robert L. Nuckolls, III)
13. 09:54 PM - Re: Pitot Current Draw (Robert Sultzbach)
Message 1
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| Subject: | Re: Switch source |
On 2 Dec 2006, at 08:23, Carlos Trigo wrote:
> <trigo@mail.telepac.pt>
>
> - You are in short final to any kind of airfield, with
> your flaps deployed at maximum, and suddenly some obstacle occupies
> your runway. If your FPS fails, how are you going to go-around?
>
> Although I'm aware these are low probability situations, they are
> nevertheless some reasons why I want to have back-up/emergency
> manual control of my flaps
As Pascal indicated, there are many possible reasons why flap systems
may fail. If it is not possible to safely do a go-around with the
flaps fully extended, this suggests that the maximum flap angle is
too great.
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://www.kilohotel.com/rv8
Message 2
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At 03:22 PM 12/2/2006 -0800, you wrote:
>
>Bob, many thanks for the suggestion. I like the simplicity of it very
>much! :) Wish I found this drawing before drilling a hole for the
>selector switch... but no biggie, the hole can be filled.
>
>I do have a quick follow-up question -- the drawing I was using (toggle
>mag switches with start button) call out for 20 AWG shielded wire for
>P-leads... This drawing calls out for 18AWG shielded... Any concerns with
>using 20, which I have on hand? Or should I be ordering 18?
No, the currents that flow in these wires
would be easily handled by 22AWG wire. There's
a kind of rule-of-thumb for wires under the cowl,
especially those that control the mags to make
them mechanically robust. This suggests the use
of 20 or even 18AWG wire. I've seen some drawings
call out 16AWG.
>As for size of the wire.. I got the 20AWG shielded from B&C... Found the
>numbers on it and they read: M27500-20 TG1T14 So I guess it is 20AWG..
>but again.. I gotta use 22 setting on the stripper to strip it..
Interesting. This probably speaks more to the
accuracy of the dies in your tool as opposed to
variabilities in the actual size of the wire.
Bob . . .
---------------------------------------------------------
< What is so wonderful about scientific truth...is that >
< the authority which determines whether there can be >
< debate or not does not reside in some fraternity of >
< scientists; nor is it divine. The authority rests >
< with experiment. >
< --Lawrence M. Krauss >
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At 06:30 PM 12/2/2006 -0500, you wrote:
>
>Ummm
>Is this a test ;) ?
>Why wouldn't 20 awg shielded wire have a 20awg center wire??
>Ken
>
Was just inquiring as to the pedigree of the wire.
I have a spool of perfectly good wire where the
wire itself is not marked but label on the spool is
incorrect. Just asking about the data he had to
KNOW that the wire was indeed 20AWG. The source
and markings suggest the wire is the size he believes
it to be . . . which leaves tool variabilities as the
probable cause for his observations.
Bob. . .
>snip
>
>>
>>>PS. Why does 20AWG shielded wire's inner conductor appear to be thinner
>>>than regular 20AWG tefzel wire (measured diameter including
>>>insulation)? It looks the same to me as 22AWG tefzel wrapped in
>>>shielding (and my stripper won't strip it at 20AWG setting).
>>
>>
>> Maybe because it's not 20AWG wire but 22AWG.
>> How do you come to believe that it's actually
>> 20AWG wire. If there's a mil number on the wire
>> it will looke somethign like 22759/16-20-9 where
>> 22759 is the base spec. Slash 16 is the sub spec.
>> 20 is the AWG and 9 is color. If there's a third
>> dash number then it's the stripe color.
>>
>> Bob . . .
>
>
>--
>
>
>-- incoming mail is certified Virus Free.
>Checked by AVG Anti-Virus.
Bob . . .
---------------------------------------------------------
< What is so wonderful about scientific truth...is that >
< the authority which determines whether there can be >
< debate or not does not reside in some fraternity of >
< scientists; nor is it divine. The authority rests >
< with experiment. >
< --Lawrence M. Krauss >
---------------------------------------------------------
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At 03:39 PM 12/2/2006 -0800, you wrote:
>
>Hmm.. but this makes the start button "live" when both mags are off... Is
>this a big concern in "real life?" I did like the other drawing a bit
>better when the button was live only when left was on and right off.. I
>guess can't have it all? :)
Yeah, that was a problem but I ran out of poles on the
left mag switch. You could get a 3-pole switch for the left
mag and produce the functionality you're interested in.
Bob . . .
---------------------------------------------------------
< What is so wonderful about scientific truth...is that >
< the authority which determines whether there can be >
< debate or not does not reside in some fraternity of >
< scientists; nor is it divine. The authority rests >
< with experiment. >
< --Lawrence M. Krauss >
---------------------------------------------------------
Message 5
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| Subject: | Pitot Current Draw |
I have a pitot on an Exp. Aircraft that was designed for a heavier
aircraft. To accommodate the high speed and high altitude cold, the
pitot was configured to get very hot, with consumate amperage demand.
Given the lower demands of a GA aircraft, is there any way of reducing
the heating of the pitot (very warm to the touch would be fine...I don't
need to be able to brand someone!) with a consumate reduction in
amperage demand?
Chuck Jensen
Message 6
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| Subject: | Re: Pitot Current Draw |
There are ways, but what leads you to believe that the pitot is really
too hot? The whole purpose of the heater is to keep it clear in any
condition - rain, freezing rain, cold ambient, etc. Depending on what
plane you have, you will be flying at upwards of 200 mph through all
this (hopefully NOT freezing rain) and the last thing you want is for
the pitot to freeze up.
Dick Tasker
Chuck Jensen wrote:
>
>I have a pitot on an Exp. Aircraft that was designed for a heavier
>aircraft. To accommodate the high speed and high altitude cold, the
>pitot was configured to get very hot, with consumate amperage demand.
>Given the lower demands of a GA aircraft, is there any way of reducing
>the heating of the pitot (very warm to the touch would be fine...I don't
>need to be able to brand someone!) with a consumate reduction in
>amperage demand?
>
>Chuck Jensen
>
>
>
>
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that a significant number of electrons may have been temporarily inconvenienced.
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Message 7
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Hi Bob and all,
A buddy asked me to help him design his electrical circuit.
Here are some question for you experts :
- What size fuse or breaker for a facet (round) fuel pump : 5 amps, 7.5
amps, 10 amps ?
- What breaker size for a B&C Lycoming O-360 starter solenoid ?
Thanks in advance,
Regards,
Gilles Thesee
Grenoble, France
http://contrails.free.fr
Message 8
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On Sun, 03 Dec 2006 11:02:39 -0600
"Robert L. Nuckolls, III" <nuckollsr@cox.net> wrote:
>
> Was just inquiring as to the pedigree of the wire.
> I have a spool of perfectly good wire where the
> wire itself is not marked but label on the spool is
> incorrect. Just asking about the data he had to
> KNOW that the wire was indeed 20AWG. The source
> and markings suggest the wire is the size he believes
> it to be . . . which leaves tool variabilities as the
> probable cause for his observations.
>
> Bob. . .
>
>
> >snip
> >
Nope. I finally found a quick summary for the M27500 specification.
(Available at http://www.awcwire.com/pdf/CT-G4-M27500.pdf.)
M27500 can be made with any M22759 wire. M22759 with
different /no. have different insulation thicknesses. I've been
buying M27500-22TG3T14 which turns out to have M22759/18 wire in it.
That's specified by the TG.
Here are some wire outer diameters per the M22759 spec.:
M22759/16 20 AWG 0.058 - 0.062
M22759/18 20 AWG 0.049 - 0.053
M22759/16 22 AWG 0.050 - 0.053
This data is from
http://www.jaguarind.com/products/teflon/teflonwire.html
So if you have the M27500-20TG wire, the OD of the wire is identical to
the OD of M22759/16 22 AWG.
If you want M22759/16 wire in your M27500 shielded cable, it has to be
M27500-xxTExxxx.
My experience stripping the 22 AWG M22759/18 wire with the 22 AWG
setting on my stripper is that sometimes it works and sometimes it
slips. Once it's slipped, the insulation has been thinned some more
and I have to complete the strip with my el cheepo stripper similar to
your picture http://www.aeroelectric.com/articles/strippers/mvc829.jpg
Bob W.
--
N93BD - Rotary Powered BD-4 - http://www.bob-white.com
First Flight: 11/23/2006 7:50AM - 0.4 Hours Total Time
Cables for your rotary installation - http://www.roblinphoto.com/shop/
Message 9
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Bob W. -- that's it. I mic'ed both tefzel 22 and this shielded 20 and they both
came out at 0.050... My stripper doesn't wanna strip it at 20.. but works at
22 fine.. so I'm good to go.
I decided to keep the selector switch, as I didn't like having a live starter button...
It does appear that using a 3 pole switch woudl be ideal. Since my left
mag switch is close to the rib, not sure if 3 pole switch would fit in there
(not sure about its size).. so this will work good.
Thanks to everyone!
Radomir
--------
RV-7A
N777TY (res)
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=78891#78891
Message 10
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| Subject: | Re: Pitot Current Draw |
I would like to add that the pitot tube should burn your hand if you grab it after
it has been on for more than 1 or 2 minutes.
There are ways, but what leads you to believe that the pitot is really
too hot? The whole purpose of the heater is to keep it clear in any
condition - rain, freezing rain, cold ambient, etc. Depending on what
plane you have, you will be flying at upwards of 200 mph through all
this (hopefully NOT freezing rain) and the last thing you want is for
the pitot to freeze up.
Dick Tasker
Chuck Jensen wrote:
>
>I have a pitot on an Exp. Aircraft that was designed for a heavier
>aircraft. To accommodate the high speed and high altitude cold, the
>pitot was configured to get very hot, with consumate amperage demand.
>Given the lower demands of a GA aircraft, is there any way of reducing
>the heating of the pitot (very warm to the touch would be fine...I don't
>need to be able to brand someone!) with a consumate reduction in
>amperage demand?
>
>Chuck Jensen
>
>
>
>
--
Please Note:
No trees were destroyed in the sending of this message. We do concede, however,
that a significant number of electrons may have been temporarily inconvenienced.
--
Lynn A. Riggs
riggs_la@yahoo.com
St. Paul, MN
BH #656 Kit #22
http://home.comcast.net/~lariggs/wsb/html/view.cgi-home.html-.html
---------------------------------
Message 11
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| Subject: | Re: Pitot Current Draw |
Good Evening Lynn, Dick and Chuck,
In a previous life, I flew quite a few airplanes that
had a high and a low heat for the pitot tubes. They
were on low for ground operations and on high heat for
airborne use.
I think it was controlled by a strut switch, but not
sure.
Worked well though.
Happy Skies,
Old Bob
--- Lynn Riggs <riggs_la@yahoo.com> wrote:
> I would like to add that the pitot tube should burn
> your hand if you grab it after it has been on for
> more than 1 or 2 minutes.
>
> "Richard E. Tasker" <retasker@optonline.net> wrote:
> Tasker"
>
> There are ways, but what leads you to believe that
> the pitot is really
> too hot? The whole purpose of the heater is to keep
> it clear in any
> condition - rain, freezing rain, cold ambient, etc.
> Depending on what
> plane you have, you will be flying at upwards of 200
> mph through all
> this (hopefully NOT freezing rain) and the last
> thing you want is for
> the pitot to freeze up.
>
> Dick Tasker
>
> Chuck Jensen wrote:
>
> Jensen"
> >
> >I have a pitot on an Exp. Aircraft that was
> designed for a heavier
> >aircraft. To accommodate the high speed and high
> altitude cold, the
> >pitot was configured to get very hot, with
> consumate amperage demand.
> >Given the lower demands of a GA aircraft, is there
> any way of reducing
> >the heating of the pitot (very warm to the touch
> would be fine...I don't
> >need to be able to brand someone!) with a consumate
> reduction in
> >amperage demand?
> >
> >Chuck Jensen
> >
> >
> >
> >
> >
> >
> >
> >
>
> --
> Please Note:
> No trees were destroyed in the sending of this
> message. We do concede, however,
> that a significant number of electrons may have been
> temporarily inconvenienced.
> --
>
>
>
>
>
>
>
>
> Lynn A. Riggs
> riggs_la@yahoo.com
> St. Paul, MN
> BH #656 Kit #22
>
http://home.comcast.net/~lariggs/wsb/html/view.cgi-home.html-.html
>
> ---------------------------------
Message 12
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| Subject: | Re: Pitot Current Draw |
At 04:13 PM 12/3/2006 -0500, you wrote:
>
>I have a pitot on an Exp. Aircraft that was designed for a heavier
>aircraft. To accommodate the high speed and high altitude cold, the
>pitot was configured to get very hot, with consumate amperage demand.
>Given the lower demands of a GA aircraft, is there any way of reducing
>the heating of the pitot (very warm to the touch would be fine...I don't
>need to be able to brand someone!) with a consumate reduction in
>amperage demand?
Altitude and speed have little to do with a pitot tube's
need to transfer heat to the surface. The kind of ice that
a pitot tube is expected to handle happens at lower altitudes
and relatively slow speeds. It's the super-cooled water droplets
that freeze instantly on contact that represent the largest
challenge to the pitot tube's ability to shed ice.
If you've ever witnessed an ice-tunnel test on a piece
of aviation de-ice equipment, you'd realize that if your
pitot tube is being seriously challenged, then knowing
altitude and airspeed are probably the least of your concerns.
Icing conditions you're likely to survive can probably be
shed by a relatively whimpy pitot tube deice heater but these
are exceedingly difficult things to quantify. Pitot tubes
we THOUGHT were adequate 30 years ago are scoffed at today.
Intuitively, your assertion is not in error, ANY amount of
heat will shed SOME ice. SOME ice is survivable while OTHER
ice is not. Given the changes in de-ice certification protocols
over the years, it becomes difficult to put numbers on "any",
"some" and "other". So difficult that for anyone to offer you
advice advocating "this many watts as opposed to that many
watts" may be blowing smoke you-know-where.
When that stuff starts appearing anywhere on your airplane
is not the time to be experimenting with the adequacy of
your pitot heater decisions. The best rule of thumb is put
on the biggest heater you can find/afford but plan on the
expeditious 180 no matter how robust you belive your heater
to be.
Bob . . .
Message 13
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| Subject: | Re: Pitot Current Draw |
Hi Bob,
Staying out of icing if possible is good advice. I
lost pitot static instruments 2 or 3 times in a full
deicing equipped Navy jet over a 3 year period. It
gives you quite a chill in the spinal area to see your
airspeed dropping off so quickly to zero. I happened
to be level at the time of loss. Icing of the pitot
tube turns your airspeed indicator into an altimeter
for all intents and purposes. The higher you go the
higher the airspeed you'll see. The lower you go the
lower the airspeed. You can see how hazardous that is
since you'll climb and show higher airspeed with the
nose way up, right to the stall and spin. Another
sound piece of advice is to know what airspeed a given
attitude and power setting will give you and don't
mess with your configuration any more than necessary
to land.
Safe flying,
Bob Sultzbach
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