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
antenna
* Internal mounting hardware means that the screw/bolt heads
are inside the aircraft. The base of the antenna is smooth, i.e. 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."
Doug
C35
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!
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.
Step by Step Nav Blades Install & Pictures
Dorne & Margolin DM N4-17
Nav/Loc/GS Blades
