Because Owning And Flying Your Beechcraft Can Be Done Safely AND For Less Money!
  Step by Step Nav Blades Install & Pictures


So you want sexy, sleek Nav Blades on your Beechcraft instead of that pimp-mobile high drag Flying V?


Dorne & Margolin DM N4-17 Nav/Loc/GS Blades


Antenna Cross Reference File HERE



Here is some rough data captured by Beech Lister, Ward A. from his plane with and without the flying "V":


+9C, 2500ft, 30.7", 2500rpm

No Antenna 170.4 KIAS

Antenna 167.8 KIAS

Delta 2.6 KIAS

Calculated Flat Plate Area 0.087 ft^2

Fuel Flow FF 17.0gph, TIT 1480F


The antenna is not the old NARCO, but a replacement manufactured by Meriden Electronics Corp. Data was collected during an early calm morning. KIAS was recorded to the nearest 1 KIAS every 30 seconds for 15 minutes while on auto pilot. Data averaged to determine the most exact KIAS. There is some level of random error on the data, but not calculated.


Ward also cautions:

"....testing procedure is paramount. Some level of random and systematic errors exist for which I don't have any analysis. YMMV. No warranties expressed or implied."



Here is an Old School Lab Drag Demo that really brings home the point!




Can you appreciate the drag these antennas are capable of producing?


Here are Dr. Dave Rogers' verbatim comments to the Beech List regarding antenna drag:


There is a lot of misunderstanding about antenna drag especially of the Bonanza birdwing (V-antenna). To put antenna drag in perspective a number of years ago I did extensive wind tunnel tests on aircraft antennas. From those tests we can obtain some comparative results. Those results are:


A single rod type 1.84

comm antenna***


Bonanza V-antenna 1.7

Standard blade type 0.6 comm antenna with internal mounting hardware*


Standard blade type 1.0

comm antenna with external mounting hardware**


Single blade loc/gs 0.3

antenna mounted on the vertical fin or below the V-tail****


Garmin style GPS 0.1



* Internal mounting hardware means that the screw/bolt heads are inside the aircraft. The base of the antenna is smooth, i.e. similar to


** External mounting hardware means that the screw/bolt heads are external to the aircraft typically in recessed cylindrical holes, i.e. similar to


*** Similar to


**** Similar to



Click HERE for Bob Siegfried II's Bonanza Nav Blades install article, complete with his color pics and detailed instructions on how he installed them on his Bonanza. The bracing fabrication, I affectionately refer to as the "Brooklyn Bridge", in his install is incredible! You and your A&P decide whether or not that level of strength is needed in your install.


See the 337* Bob II filed for his Nav Blades install HERE


*Note: Bob II advises that  no FSDO approval was issued, as it was the opinion of their FSDO that none was needed at the time of their install. 


See another 337 filed for this type of Nav Blades install HERE


NEWS FLASH: Here is a verbatim note I received from Old Bob Siegfried yesterday, 8/11/2012:


Early this week. I received a call from our local FSDO. He had been contacted by a FED from the Atlanta office who feels that our method of installing blades on the tail of a Bonanza or Bonanza derivative should have been flight tested. I disagree with his (the Atlanta guy) analysis, but my FED did ask that we stop recommending mounting navigation blades in that manner until the issue is resolved.


I asked if he wanted us to remove the blades we have installed and was told that would not be required, but he thought we should recommend that no additional blades be installed until the matter of flight testing is resolved.


I have notified Tom Turner and he is going to contact all of  the ABS maintenance representatives.


Since you have a copy of our particular installation on your website, I believe we should add a note to the effect that the legality of such an installation is currently under investigation and that I do not recommend any such installation be undertaken unless the local FSDO is willing to take responsibility for approving the installation. I think the FAA guy in Atlanta is way off base on this one, but I do not intend to get in a fight about the installation.


I think we as IAs should be able to evaluate the blade positions and attachments based on historic Part 43 data. The FED in Atlanta does not seem to agree with my interpretation.<G> Pity, but that is what it looks like at this time. As I said, my supervising inspector was very pleasant, but did ask that I not install or recommend that anyone else install blades in that manner until the issue is resolved.


Happy Skies,

Old Bob


So, you are all hereby advised that blade mounting under the tail feathers of any Bonanza or Bonanza derivative aircraft is NOT recommended until the issue of "flight testing" is resolved within the FAA.


Email Bob Siegfried II a question about his install:   


I'm told that the inspiration for the Siegfried install came from the infamous Mike Smith (of Mike Smith Speed Mods* fame) and the Blade position advocated by Mike was to be below the tail and as far rearward as could be achieved. Mike Smith is also reported to have advocated a slight nose low attitude for the leading edges of the blades as the lowest drag configuration for the V-Tailed Bonanza from his drag investigations.


*Side Bar: BDS reportedly purchased all of Mike Smith's Speed Mod STCs. So, if you'd like to to know more about them you'll have to beat down their door as I've heard that they are not actively taking them to market. A shame IMHO.


Here are pics of a Bonanza owner J.D. Morris' install using the Siegfried "Brooklyn Bridge" <vbg> approach. Note the angle of the dangle of the blades in the side view. This angle is reportedly consistent with the Mike Smith speed mods mounting methodology:






Another Beech owner has done a little oil wind flow test and found a similarly slight angle downward at the nose of the blade was in line with the airflow in flight.


Here is Beech Lister and Bo Owner, Doug G's account of the air flow he observed on his C35 Bonanza tail section after flying through a fair amount of rain.



"I flew through a fair amount of rain the other day and yesterday happened to notice that some streaks under the tail of my C35 right in the area where blade antennae are often mounted.  I couldn't get a good picture to show the streaks, but I put some masking tape on the fuselage to show the pattern they made.  It looks like Old Bob was right (what a surprise!<g>) about placing them with the leading edge down a bit.  I seem to recall this was a Mike Smith idea, but could be wrong. I just figured I would share for any non-believers out there."






Tufted Airflow under V-tail Bonanza @ 2k 162KTAS during cruise.







There have been reports of a Nav blade antenna manufacturer that has drawings showing the mounting of the blades on the fuselage AHEAD of the tail surfaces. This installation has been reported to create tail buffeting at low speeds. As with all things aviation, you and your mechanic decide your course of action regarding any installation, antenna or otherwise.


See my B55 blades install pics HERE, a total of 14 pictures. My install used 0.060" aluminum doublers for what my mechanic and I felt provided the reinforcement needed. You'll also see a nice roof patch plate that becomes the base for the replacement Com antenna.



The finished product. A less "draggy" roof line and a better COM antenna for Com #1.


Yes, my blades are below the horizontal stabilizer AND they function quite well in that position, giving me solid VOR signals from over 90 miles at 8,000' and excellent Localizer and Glideslope signal to both my Narco MK12Ds. Also, my blade install is parallel to the water line of the aircraft (I did not have the benefit of the nose down info at the time of my install). Why install there you ask? Installation simplicity! When we thought about the complexities of install in the vertical fin there was no comparison. V-Tails get their blades mounted under their stabilators, right?


Here are some comments from Old Bob to the Beech List on 4/21/2009 regarding the use of blades vs. the old Beechcraft Flying V antenna:


Beauty is in the eye of the Beholder.


Ever since I learned from Mike Smith that the blades on the tail were lower drag than the Flying V, learned from one of the electronics gurus that the closer the VHF navigation antenna was to the windshield, the worse the antenna was affected by precipitation static, from another electronic guru that the now ancient electronic RNAV units worked much better with a towel bar or blade antenna than they did with a V, from Dennis Wolters, that the Flying V generated considerable audio noise, from Dennis Wolters (again) that the sunshields inside the windows reduced the life of the windows and that I should use a cabin cover any time the aircraft was parked in the sun, the look of the Flying V has become much less appealing.


Beech used that antenna to save manufacturing time and cost. It is relatively heavy and placed in the worst possible spot on the airplane from a drag standpoint. I would love to see doctor Dave's (Dave Rogers of aeronautical engineering fame) precise measurements of drag at the angles of attack and speeds that I normally fly. Chances are that I would not be able to understand anything more complicated than a statement that one configuration has more drag than another and that data he has given us.


I am sure he will comment further if he does see this message, but I do believe he will also affirm that the airflow above the cabin is about as fast a stream as will be found flowing over the aircraft and that the faster the flow, the higher the drag.


Mike Smith took everything off the top of the airplane. Not only the antennas, but the airscoop as well. His horizontal VHF communication antenna mounted in his plastic tail cone with a woefully undersized ground plane actually worked for some folks. Others found they needed a higher efficiency antenna. He proved the efficacy of his modifications by guaranteeing a speed increase when his speed mods were applied. Ask anyone who owns one that he has modified. They just plain go faster. How much is very hard to say because of the variable conditions under which we all fly.


I tend to fly at relatively low indicated airspeeds because I enjoy the longer range and lower fuel consumption per mile available at those speeds. Others put a higher value on their time than do I. Not only that, I like to fly and going slower allows me to build more flying time!


Happy Skies,

Old Bob


Bob Siegfried



See the Comant CI-120 Nav Blades pdf HERE


For a Dual G/S install you will need something like the 


Comant CI-1125 Diplexer


Finding a CSOB set of Nav Blades can be the most challenging part of this project. Since I already have my set of blades from eBay, I suggest you camp out on eBay and wait for a nice set to come along. From what I've seen, you should be able to score a decent set for something under $500.


Be sure you get the antenna "Combiner" with your blades, otherwise you'll be on another eBay hunt for that key item. The Combiner takes the signal from each blade and provides a single point for a single coax cable connection to run up to your Diplexer, then from the Diplexer to your Nav radio antenna connections.



Try these EBay Searches: SEARCH #1 Dorne Margolin or SEARCH #2 Comant or Search #3 Diplexer


or call Dodson (785) 878-4000 Ext. #1103 and tell him you want the CSOB Special!


Good Luck!


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