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Dan.Beadle(at)hq.inclines
Guest

Posted: Wed May 17, 2006 7:35 am Post subject: Antennas

I am building RV8. I am trying to figure out all the antenna placements

before closing up the wings.



Here is my current plan. I would appreciate feedback.



*	Com antenna on belly - poor reception on the ground, but only

have to go short distances.  Good in air because it is looking down at

station.  Needs to be vertical for a bit to match the polarization of

the ground station.

*	Nav antenna in one wing.  Combines GS antenna thru a spliter.

Compromise over a good external antenna, but no drag. (Bob Archer)

*	Marker beacon antenna in other wing tip.

*	Transponder - little short antenna coming out the belly.

*	ELT - should be on top - maybe just ahead of Vert Stab.

*	GPS - under canopy on panel eyebrow.



We are planning GNS430, Grand Rapids EFIS with GPS, Garmin XPndr and

Audio Panel.  Is this a good antenna match for this equipment?

rv8ch

Joined: 10 Jan 2006
Posts: 250
Location: Switzerland

Posted: Wed May 17, 2006 8:33 am Post subject: Antennas

 	  Quote: 	
		   *	Com antenna on belly - poor reception on the ground, but only

 have to go short distances.  Good in air because it is looking down at

 station.  Needs to be vertical for a bit to match the polarization of

 the ground station.

 *	Nav antenna in one wing.  Combines GS antenna thru a spliter.

 Compromise over a good external antenna, but no drag. (Bob Archer)

 *	Marker beacon antenna in other wing tip.

 *	Transponder - little short antenna coming out the belly.

 *	ELT - should be on top - maybe just ahead of Vert Stab.

 *	GPS - under canopy on panel eyebrow.


	


On my RV8 I didn't have room for the ELT antenna on top

of the fuselage in front of the VS.  The canopy slides

all the way back to the VS.  I put it just under the

VS like this:



  http://www.rv8.ch/article.php?story050226171858929



The rest of your locations are pretty much the same place I

have either put my antennas or plan to.



-- 

Mickey Coggins

http://www.rv8.ch/

#82007 finishing

_________________
Mickey Coggins
http://www.rv8.ch/

Hopperdhh(at)aol.com
Guest

Posted: Wed May 17, 2006 8:33 am Post subject: Antennas

Dan,

 

I have my comm and transponder antennas on the bottom of the airplane  as you 

say.  I am amazed at how well the comm antenna works.  My  runway is inside 

Grissom's class D, and I am always able to contact the tower  about 3 miles 

away before I take off.

 

I am having very good results with a VOR antenna under the canopy in my  

RV-7A.  Mine is a homemade dipole with white no. 22 wire fastened to the  canopy 

with 4 small suction cups -- a little cheesy, but free and it probably  

outperforms the wingtip mounted antennas.  Maybe you could mount a  commercial 

VOR/Glideslope antenna under the canopy also.

 

I also have the GPS antenna on the glare shield under the canopy and it  

works very well.  I am using a BNC bulkhead fitting (BNC to BNC)  with the 

portable antenna from the back of the Garmin 295 sitting on the  mounted fitting -- 

fitting vertical, antenna horizontal.  A short  (about 6 inch) piece of RG-400 

connects the bottom side of the fitting to the  panel mounted 295.  Perhaps a 

little cheesy, but again -- basically  free.

 

 

An external ELT antenna is best, but few RVs use them.  Quite a bit of  drag 

at 200 mph!  Putting the ELT antenna under the empennage fairing as  some are 

doing is basically no antenna at all.  I have mine in the baggage  compartment 

and aimed away from metal as much as possible -- definitely a  compromised 

location -- that wouldn't work on an 8.  It should be close to  the ELT, so 

wingtips are out.  This is a hard one!

 

I don't think it matters what antenna is used with what  equipment, except in 

the case of GPS where the antenna has an internal  amplifier.  In that case I 

think the antenna should be the same brand as  the receiver.  All the passive 

antennas will work as well with one brand of  equipment as with another brand.

 

All IMHO, of course.

 

Dan Hopper

Walton, IN 

RV-7A -- Flying about 170 hours now

 

 

In a message dated 5/17/2006 11:38:45 A.M. Eastern Daylight Time,  

Dan.Beadle(at)hq.inclinesoftworks.com writes:




<Dan.Beadle(at)hq.InclineSoftworks.com>



I am building RV8. I am  trying to figure out all the antenna placements

before closing up the  wings.

frank.hinde(at)hp.com
Guest

Posted: Wed May 17, 2006 8:56 am Post subject: Antennas

Just a thought but to avoid a long wiring run out to a wingtip why not

put the marker beacon glued to the lower cowl.



I should be able to just get a 40" piece of stripped coax along there.



Frank

RV7a..almost painting 





 	  Quote: 	
		   *	Marker beacon antenna in other wing tip.

BobsV35B(at)aol.com
Guest

Posted: Wed May 17, 2006 10:25 am Post subject: Antennas

In a message dated 5/17/2006 10:38:45 A.M. Central Standard Time,  

Dan.Beadle(at)hq.inclinesoftworks.com writes:



*   GPS - under canopy on panel eyebrow.



We are planning  GNS430, Grand Rapids EFIS with GPS, Garmin XPndr and

Audio Panel.  Is  this a good antenna match for this equipment

Good Morning Dan,

 

I might look carefully at your GPS antenna location. It would probably work  

acceptably, but I am not sure it would meet the requirements for IFR  

certification without flight testing.

 

The guidance for antenna placement is located in an AC. I believe it is  

AC-138.  You may not have full 360 degree coverage. As long as you have  that high 

powered 430, it would be a shame to get less than optimum  performance.  

 

You might also consider that there will be an upgrade soon that will allow  

the 430 to receive WAAS signals. For WAAS reception, you have to have a good  

line of sight to the south as the WAAS satellites are located over the equator. 

 Heading north, that may be a problem.

 

Just something to think about.

 

Happy  Skies,



Old Bob

AKA

Bob Siegfried

Ancient Aviator

Stearman  N3977A

Brookeridge Air Park LL22

Downers Grove, IL 60516

630  985-8503

gmcjetpilot(at)yahoo.com
Guest

Posted: Thu May 18, 2006 2:27 am Post subject: Antennas

 	  Quote: 	
		  Subject: Antennas

From: "Dan Beadle" 

  >

 	  Quote: 	
		   *Com antenna on belly - poor reception on the ground, but 

  >only have to go short distances. Good in air because it is 

  >looking down at station. Needs to be vertical for a bit to match 

  >the polarization of the ground station.

  Dan I would disagree in that you are NOT guaranteed poor 

  reception (or transmission) on the ground. I had my COM on 

  the belly of my RV-4 and never had a big problem, even at 

  large towered airports. I do find buildings or hangers are the 

  biggest impediment. I fly large jets and only one airport (LGA) 

  do I have to switch to the #1 radio (antenna on top) to talk to 

  ground/clearance, and that is only when I am in alley way. One 

  of those scary alley ways that where made for piston planes 

  55 years ago not jets with larger wing spans.   

 	  Quote: 	
		  Subject: Re: Antennas

From: Hopperdhh(at)aol.com

An external ELT antenna is best, but few RVs use them. 

  >Quite a bit of drag at 200 mph! Putting the ELT antenna under 

  >the empennage fairing as some are doing is basically no 

  >antenna at all... Dan Hopper

  Dan: You have to qualify what you mean about quite a bit of 

  drag. I disagree that is quite a bit.

  From my calculations at 200 MPH the drag penalties are:

  ELT =  1/8 to 3/16 th mph MAX

  COM = 0.25 to 0.30 mph MAX

  Transponder = 0.06 to 0.10 mph MAX

  Total is less than 2/3 rds mph.

  The above are from my own calculations. I dusted off my 

  mechanical pencil and aerodynamics book (yes I was an 

  engineer for a large aircraft manufacture at one time.)

  To back up my numbers here is a quote:

  ***************************************

"There is a recent article in Plane & Pilot which 

features the Socata Trinidad. Interesting enough, 

the engineers at Socata actually quantified the 

cruise speed impact of each antenna:"

  ADF - .75 knots

G/S - .32 knots

VOR - .59 knots

ELT - .16 knots

  ***************************************

  This is for a Aerospatiale-Socata TB-20 with a listed 

  184 mph cruise and 192 mph top speed so these 

  drag penalties are equivalent for a fast amateur built 

  experimental aircraft.

  If you assume 1/2 of a VOR is about equal to a COM 

  than 0.25 to 0.30 mph drag at 200 mph is reasonable.  

  The ELT is almost exactly what I calculated. 

  The exaggerate rumors and urban legend of antenna 

  drag are probably spread by people who want you to 

  use wing tip antennas, which perform poorly. Not to 

  mention the long (heavy) coax runs that result in more 

  signal loss. The wing tip antennas also are more 

  troublesome to install.

  For all you racers and go fast guys, here is an idea that

  worked for me very well for years on my RV-4. I made it 

  so I could remove the belly COM and VOR antenna in a 

  matter of minutes. I would replace the COM with an 

  antenna in the cockpit for races and performance contest. 

  The VOR was also on the belly under the horizontal 

  stabilizer. With nut plates it came off with two screws 

  and the coax was secured inside the fuselage with a 

  lanyard and then the hole was taped over. To put them 

  back on took as long as it took to remove, a few minutes. 

  If you want to pick you the 2/3 rds to 3/4 MPH, its an idea.  

  Cheers George RV-4/RV-7

 __________________________________________________

Dan.Beadle(at)hq.inclines
Guest

Posted: Thu May 18, 2006 5:48 am Post subject: Antennas

Great information. I am convinced about using external Com antenna.

Where do you suggest I mount an externally mounted VOR antenna?

Vertical Stab seems obvious choice, but antenna cable length is about

the same as in wingtip.



Dan

--

brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Thu May 18, 2006 6:09 am Post subject: Antennas

On May 17, 2006, at 8:33 AM, Dan Beadle wrote:



 	  Quote: 	
		   We are planning GNS430, Grand Rapids EFIS with GPS, Garmin XPndr and

 Audio Panel.  Is this a good antenna match for this equipment?


	


Sounds fine to me.

Brian Lloyd                         361 Catterline Way

brian-yak AT lloyd DOT com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

 Antoine de Saint-Exupry

_________________
Brian Lloyd
brian-yak at lloyd dot com
+1.916.367.2131 (voice) +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery

BobsV35B(at)aol.com
Guest

Posted: Thu May 18, 2006 7:09 am Post subject: Antennas

In a message dated 5/18/2006 9:50:16 A.M. Central Standard Time,  

Dan.Beadle(at)hq.InclineSoftworks.com writes:



Great  information. I am convinced about using external Com antenna.

Where do you  suggest I mount an externally mounted VOR antenna?

Vertical Stab seems  obvious choice, but antenna cable length is about

the same as in  wingtip.



Dan



Good Morning Dan,

 

If you are going to use an external VHF Nav antenna, consider using a set  of 

blades. They have superior reception patterns and one set can be used to feed 

 two nav receivers and two glide slopes by using an appropriate splitter.

 

Nice looking, no wires to stick in folks eyes, handle icing conditions  well 

and have relatively low drag.

 

Happy  Skies,



Old Bob

AKA

Bob Siegfried

Ancient Aviator

Stearman  N3977A

Brookeridge Air Park LL22

Downers Grove, IL 60516

630  985-8503

Hopperdhh(at)aol.com
Guest

Posted: Thu May 18, 2006 9:41 am Post subject: Antennas

George,

 

I went thru the calculations a couple of years ago and came up with  somewhat 

larger numbers than that.  At least that's how I remembered  it.  I guess I 

was mistaken!

 

I do agree with OC that we don't know how the airplane will end up in a  

crash.  Its not that unlikely that an RV will be on its top  (again IMHO).  The 

convenience of an easy installation for the ELT in  the baggage compartment of 

my -7 is what drove my decision as much as  anything.  At the time, I was in a 

hurry to get it in the air, and figured  that it was a temporary location for 

the antenna until I figured out the best  place.  Still trying to figure that 

one out!

 

Regards,

Dan Hopper

RV-7A Flying since July 2004

 

 

 

In a message dated 5/18/2006 6:29:51 A.M. Eastern Daylight Time,  

gmcjetpilot(at)yahoo.com writes:

 	  Quote: 	
		  Subject: Re: Antennas

From:  Hopperdhh(at)aol.com



An external ELT antenna is best, but few RVs  use them. 

Quite a bit of drag at 200 mph! Putting the ELT  antenna under 

the empennage fairing as some are doing is  basically no 

antenna at all... Dan Hopper


	




Dan: You have to qualify what you mean about quite  a bit of 

drag. I disagree that is quite a bit.



 	  Quote: 	
		  From my calculations at 200 MPH the drag penalties  are:


	


ELT =  1/8 to 3/16 th mph MAX

COM = 0.25 to 0.30 mph MAX

Transponder = 0.06 to 0.10 mph  MAX



Total is less than 2/3 rds mph.

Gilles.Thesee(at)ac-greno
Guest

Posted: Thu May 18, 2006 9:56 am Post subject: Antennas

Hi gmcjetpilot and all,



 	  Quote: 	
		      

   ***************************************

 "There is a recent article in Plane & Pilot which 

 features the Socata Trinidad. Interesting enough, 

 the engineers at Socata actually quantified the 

 cruise speed impact of each antenna:"



   ADF - .75 knots

 G/S - .32 knots

 VOR - .59 knots

 ELT - .16 knots

   ***************************************

    

   This is for a Aerospatiale-Socata TB-20 with a listed 

   184 mph cruise and 192 mph top speed so these 

   drag penalties are equivalent for a fast amateur built 

   experimental aircraft.

    

   If you assume 1/2 of a VOR is about equal to a COM 

   than 0.25 to 0.30 mph drag at 200 mph is reasonable.  

   The ELT is almost exactly what I calculated. 

    

   The exaggerate rumors and urban legend of antenna 

   drag are probably spread by people who want you to 

   use wing tip antennas, which perform poorly.

Glad you took the Socata TB-20 Trinidad as an example. It is a French 
	


airplane and its performance is very well known.



It takes a Trinidad a 250 hp engine to cruise at 155 knots TAS (75 % power).

Your 1.82 knot cruise speed impact on this large draggy spam can amounts 

to more than 3 % of the Trinidad total drag. That means about 6.5 hp 

just to carry your antennas in the breeze.



Our MCR-4S four seater has a 100 hp engine and cruises at 140 knots TAS. 

(75 % power).

Total drag is much lower. Those same antennas would spend 4.8 hp on our 

MCR. Much more significant when compared to the 75 hp cruise setting.



I'd say something on the order of 2 to 3 knots for an MCR. 3 knots or 5 

km/h is something we can easily see on the ASI or when flying formation. 

That is the difference we currently measure between clean and dirty MCRs.



Of course there is no point in hiding antennas on a Pitts or a Cessna, 

but small and sleek airplanes will really benefit.

And it is so easy to do, so why not try ?



Regards,

Gilles Thesee

Grenoble, France

http://contrails.free.fr

brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Thu May 18, 2006 9:46 pm Post subject: Antennas

On May 18, 2006, at 6:40 AM, Dan Beadle wrote:



 	  Quote: 	
		   

 <Dan.Beadle(at)hq.InclineSoftworks.com>



 Great information. I am convinced about using external Com antenna.

 Where do you suggest I mount an externally mounted VOR antenna?

 Vertical Stab seems obvious choice, but antenna cable length is about

 the same as in wingtip.


	


Antenna cable length at 108 MHz is really not an issue.

Brian Lloyd                         361 Catterline Way

brian-yak AT lloyd DOT com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

 Antoine de Saint-Exupry

gmcjetpilot(at)yahoo.com
Guest

Posted: Fri May 19, 2006 6:38 am Post subject: Antennas

 	  Quote: 	
		  From: Gilles Thesee <Gilles.Thesee(at)ac-grenoble.fr>

Hi gmcjetpilot and all,



It takes a Trinidad a 250 hp engine to cruise at 155 knots 

TAS (75 % power). Your 1.82 knot cruise speed impact on 

this large draggy spam can amounts to more than 3 % of 

the Trinidad total drag. That means about 6.5 hp just to 

carry your antennas in the breeze.

   
	


  cher monsieur

   

  Your HP values are way off, and I'll prove my point with 

analytical values and flight test data, beg your attention.

   

  Here is the calculations for one COM at 200 mph:

   

  Area: 2.88 in-sq (.04 ft-sq)(assume 20"x3/16" bent-whip w/ base)

Cd: 0.50 ( Fluid Dynamic Drag, by Hoerner, fig 13, pg 3-9)

Drag: 1.02 lbs

HP req: 0.54

HP act: 0.68 (assume prop efficency 0.80)

Speed penalty: 0.25 mph (0.22 kts)

   

  0.68 HP not 3 HP. This is what I am talking about. 



  If I used 3.75 in-sq the drag would be 0.89 HP/ 0.33 mph lost. 

These numbers are WAY conservative.

   

  Remeber the TB-20 Airplane Flight Manual (AFM) placed the 

penalty of the VOR (about twice a COM antenna in frontal area) 

at 0.59 kts (.68 mph). Half is .34 MPH. This is what I got. This 

is equal to less then 1 HP not 6.5 HP. If you had a VOR and COM

(like 3 COM's) we have about 2.1 to 2.7 HP MAX. 

   

  I agree IF you can get rid of this drag great, but we need 

antennas. A metal plane is limited in where the antennas can go. 

   

   

  

 	  Quote: 	
		  Our MCR-4S four seater has a 100 hp engine and cruises at 140 

knots TAS. (75 % power). Total drag is much lower. Those same 

antennas would spend 4.8 hp on our MCR. Much more significant 

when compared to the 75 hp cruise setting.

   
	


  I don't know what a MCR-4S. It does not matter drag is drag, but 

if it is fiberglass than by all means hide your antenna's. However 

I only fly metal airplanes, fiberglass is for hot tubs and boats. 

(I am kidding, joke, ha ha). 

   

  Clearly a metal plane like a RV can not hide antennas like a 

composite plane. It is just not a big deal, (read on).

   

   

  

 	  Quote: 	
		  I'd say something on the order of 2 to 3 knots for an MCR. 3 knots 

or 5 km/h is something we can easily see on the ASI or when flying 

formation. That is the difference we currently measure between clean 

and dirty MCRs.

   
	


   When I took off my COM and VOR whiskers the speed differnce was 

NIL or negligible. However from flight test it did appear I picked up a 

some speed.  Of course measuring such a small change is hard with 

flight test that has errors. Analytically I know its good for about 1/3rd 

mph. Flight test back up the calculations. Drag is not that large.

   

  An antenna is just not that big of a deal. Now 5 or 10 antennas 

would get your attention, but one antenna or two antenna, no. 

   

  YOUR MCR-4S:

   

  Drag is a function of airspeed. With your 140 kt cruise, your speed 

loss is about 1/8th MPH for one COM. With  frontal area, coefficient 

of drag conservatively assumed, calculated drag is very straight 

forward. Your 2 to 3 kts is off by a factor of  16 to 24 too high. 

   

   

  For your 140 kt (160 mph plane) one COM the calculations:

   

  Area: 2.88 in sq (0.04 ft sq) (assume 20"x3/16" bent whip w/base)

Cd: 0.50 ( Fluid Dynamic Drag, by Hoerner, fig 13, pg 3-9)

Drag: 0.66 lbs

HP req: 0.28

HP act: 0.36 (assume prop efficency 0.80)

Speed penalty: 0.11 mph (0.095 kts)

   

  That is hard to read on the IAS. IT IS NOT THAT BAD 

  

Even if I assumed a large frontal areal say 3.75 in-sq, 

  speed lost = .14 mph, it is no big deal.

   

  Even with 2 or 3 antennas we are talking about small losses. 

  Losses yes, but not the huge amounts that people assume.

  ce n'est pas une affaire, un problme

   

   

   

  >Of course there is no point in hiding antennas on a Pitts or a Cessna, 

 	  Quote: 	
		  but small and sleek airplanes will really benefit.

And it is so easy to do, so why not try ?

  
	


I appreciate your opinion and I guess any plane can benefit from less 

drag. However in a metal plane antenna placement it pretty limited 

to external locations. Again the drag from on COM, Tpx or VOR is 

about 3/4 - 1 mph tops on a 200 mph plane, or I should say a 199 mph 

plane.



   

  It does not matter if it is a RV-7, MCR-4S, Cessna or Pitts, DRAG is 

DRAG. However if fiberglass HIDE AWAY. However if it is good to 

bury the antennas why does the Lancair Columbia and Cirrus aircraft 

sprout external antennas? http://www.cirrusdesign.com/

  

I suggest you can experiment and temporarily mount antennas on the 

airframe and fly. I have done this. It just is not a big deal.

  

Cheers George

  

 



 __________________________________________________

robh(at)hyperion-ef.us
Guest

Posted: Fri May 19, 2006 7:10 am Post subject: Antennas

In order to gain certification something must be done to make the composite

structure electrically conductive in order to deal with a lightning strike.

So, unlike experimental composite aircraft, the certificated variety have a

metallic mesh, Al or Cu, imbedded in the laminate.  This precludes mounting

antennas internally.

Best regards,



Rob Housman

A070

Airframe complete

Irvine, CA



--

Gilles.Thesee(at)ac-greno
Guest

Posted: Fri May 19, 2006 7:17 am Post subject: Antennas

Rob Housman a crit :

 	  Quote: 	
		   



 In order to gain certification something must be done to make the composite

 structure electrically conductive in order to deal with a lightning strike.

 So, unlike experimental composite aircraft, the certificated variety have a

 metallic mesh, Al or Cu, imbedded in the laminate.  This precludes mounting

 antennas internally.



   

Hi Rob,
	




Aren't we talking about experimental aircraft ?

By the way, why should aluminum RVs be able to hide antennas and not 

compsite airplanes ? Wingtips, fin cap, etc...



Regards,

Gilles Thesee

Grenoble, France

http://contrails.free.fr

Gilles.Thesee(at)ac-greno
Guest

Posted: Fri May 19, 2006 7:42 am Post subject: Antennas

Dear Monsieur gmcjetpilot,

 	  Quote: 	
		      

   Your HP values are way off, and I'll prove my point with 

 analytical values and flight test data, beg your attention.

   


	


Thank you for your message.

I was quoting your numbers :



  ***************************************

"There is a recent article in Plane & Pilot which 

features the Socata Trinidad. Interesting enough, 

the engineers at Socata actually quantified the 

cruise speed impact of each antenna:"



  ADF - .75 knots

G/S - .32 knots

VOR - .59 knots

ELT - .16 knots

  ***************************************



The total speed reduction is indeed in the vicinity of 1.82 knot. We 

ought to include one COM antenna.



 	  Quote: 	
		       

   I don't know what a MCR-4S. 


	


Oh, you really should check



http://contrails.free.fr/index_en.php



 	  Quote: 	
		     Clearly a metal plane like a RV can not hide antennas like a 

 composite plane. It is just not a big deal, (read on).

   


	


They do have plastic wingtips and fin tops.

 	  Quote: 	
		  

    When I took off my COM and VOR whiskers the speed differnce was 

 NIL or negligible. 


	


What type airplane ? No wonder if it is some aluminum box with short 

wings and a big engine 



 	  Quote: 	
		    With your 140 kt cruise, your speed 

 loss is about 1/8th MPH for one COM.


	


How come ? With a speed loss of 0.3 kt at 155 kt,  the same antenna 

would lose only 0.1 kt at 140 ?



 	  Quote: 	
		      

   Even with 2 or 3 antennas we are talking about small losses. 

   Losses yes, but not the huge amounts that people assume.

   ce n'est pas une affaire, un problme



   

Just like weight reduction, small gains add to small gains, and in the 
	


end it makes quite a difference. That's how Michel Colomban's two seater 

and the MCR01 need only an 80 hp engine to CRUISE at 155 kt TAS.

Those who indulge in the "ce n'est pas une affaire" attitude are 

achieving  much lower speeds.



 	  Quote: 	
		   However if it is good to 

 bury the antennas why does the Lancair Columbia and Cirrus aircraft 

 sprout external antennas? http://www.cirrusdesign.com/

   

They are designed by, ahem, aircraft engineers. Many of them have the 
	


same "pas une affaire" background.

The industry doesn't believe in the existence of drag. Especially in the 

land of cheap gas and big engines.



 	  Quote: 	
		     

 I suggest you can experiment and temporarily mount antennas on the 

 airframe and fly.

   

No need. I just have to watch similar airplanes with their antennas 
	


sticking out, and receding in my slipstream 

Oh, and by the way, do you really count the Cirrus in the sleek airplane 

category ?



Regards,

Gilles Thesee

Grenoble, France

http://contrails.free.fr

robh(at)hyperion-ef.us
Guest

Posted: Fri May 19, 2006 7:51 am Post subject: Antennas

Gilles, see the bottom of my reply to George's message - he is asking why

Cirrus and Columbia have external antennas..

Best regards,



Rob Housman

A070

Airframe complete

Irvine, CA



--

endspeed(at)yahoo.com
Guest

Posted: Fri May 19, 2006 8:40 am Post subject: Antennas

Monsieur:  



I noticed you live in Grenoble.  Ah, I remember the

great Jean-Claud Killy and the 1968 Winter Olympic

Games.  Is that correct?  Il y a quarante annee's?

C'est impossible!  How is the skiing there these days?

 Magnificent, n'est pas?



Bob Sultzbach



--- Gilles Thesee <Gilles.Thesee(at)ac-grenoble.fr>

wrote:



 	  Quote: 	
		   

 Thesee <Gilles.Thesee(at)ac-grenoble.fr>

 

 Dear Monsieur gmcjetpilot,

 

 

 >    

 >   Your HP values are way off, and I'll prove my

 point with 

 > analytical values and flight test data, beg your

 attention.

 >   

 

 Thank you for your message.

 I was quoting your numbers :

 

   ***************************************

 "There is a recent article in Plane & Pilot which 

 features the Socata Trinidad. Interesting enough, 

 the engineers at Socata actually quantified the 

 cruise speed impact of each antenna:"

 

   ADF - .75 knots

 G/S - .32 knots

 VOR - .59 knots

 ELT - .16 knots

   ***************************************

 

 The total speed reduction is indeed in the vicinity

 of 1.82 knot. We 

 ought to include one COM antenna.

 

 >     

 >   I don't know what a MCR-4S. 

 

 Oh, you really should check

 

 http://contrails.free.fr/index_en.php

 

 >   Clearly a metal plane like a RV can not hide

 antennas like a 

 > composite plane. It is just not a big deal, (read

 on).

 >   

 

 They do have plastic wingtips and fin tops.

 >

 >    When I took off my COM and VOR whiskers the

 speed differnce was 

 > NIL or negligible. 

 

 What type airplane ? No wonder if it is some

 aluminum box with short 

 wings and a big engine 

 

 >  With your 140 kt cruise, your speed 

 > loss is about 1/8th MPH for one COM.

 

 How come ? With a speed loss of 0.3 kt at 155 kt, 

 the same antenna 

 would lose only 0.1 kt at 140 ?

 

 >    

 >   Even with 2 or 3 antennas we are talking about

 small losses. 

 >   Losses yes, but not the huge amounts that people

 assume.

 >   ce n'est pas une affaire, un problme

 >

 >   

 Just like weight reduction, small gains add to small

 gains, and in the 

 end it makes quite a difference. That's how Michel

 Colomban's two seater 

 and the MCR01 need only an 80 hp engine to CRUISE at

 155 kt TAS.

 Those who indulge in the "ce n'est pas une affaire"

 attitude are 

 achieving  much lower speeds.

 

 > However if it is good to 

 > bury the antennas why does the Lancair Columbia

 and Cirrus aircraft 

 > sprout external antennas?

 http://www.cirrusdesign.com/

 >   

 They are designed by, ahem, aircraft engineers. Many

 of them have the 

 same "pas une affaire" background.

 The industry doesn't believe in the existence of

 drag. Especially in the 

 land of cheap gas and big engines.

 

 >   

 > I suggest you can experiment and temporarily mount

 antennas on the 

 > airframe and fly.

 >   

 No need. I just have to watch similar airplanes with

 their antennas 

 sticking out, and receding in my slipstream 

 Oh, and by the way, do you really count the Cirrus

 in the sleek airplane 

 category ?

 

 Regards,

 Gilles Thesee

 Grenoble, France

 http://contrails.free.fr

 

 

 

 

 



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 FAQ,

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 Admin.



 

 

 

  

  

  

 

 

 

 


	




__________________________________________________

Gilles.Thesee(at)ac-greno
Guest

Posted: Fri May 19, 2006 11:37 am Post subject: Antennas

 	  Quote: 	
		   



 Gilles, see the bottom of my reply to George's message - he is asking why

 Cirrus and Columbia have external antennas..

   


	


Rob,



Understand.



Regards,

Gilles Thesee

Grenoble, France

http://contrails.free.fr

Gilles.Thesee(at)ac-greno
Guest

Posted: Fri May 19, 2006 12:17 pm Post subject: Antennas

 	  Quote: 	
		   Monsieur:  



 I noticed you live in Grenoble.  Ah, I remember the

 great Jean-Claud Killy and the 1968 Winter Olympic

 Games.  Is that correct?  Il y a quarante annee's?

 C'est impossible!  How is the skiing there these days?

  Magnificent, n'est pas?



   

Hi Bob,
	




You're correct. Were you there during those golden days of French skiing ?

I wasn't in Grenoble at the time, but I followed Jean-Claude Killy's 

downhill at a TV store before going to school.

Killy is still around, he is a member of the International Olympic 

Committee.



Skiing is great here, but building took sooo much time !



Amicalement,

Gilles

http://contrails.free.fr

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