On Board Communications

On Board Communications

There are no regulations requiring a radio while flying an ultralight. It is prudent however to use a radio while taking off and landing from public airfields. It would be necessary to have a radio in order to ask for "permission" to land at an airport in "controlled" airspace--most likely at a Class D airfield. 

The weight of a hand held aircraft spectrum VHF radio is minimal and even with it's low 5 watts of power, it is adequate for the needs of an ultralight pilot. Here is a picture of the ICOM A24 I use. Actually, the transmit power for voice is much lower than 5 watts.

The next issue is the decision of the pilot "interface".  One common interface is a standard pilot's headset.  (I have a simple David Clark "mono-passive" one)  These require the use of ICOM's adaptor and an additional "PTT=Push to Talk button. Note the two pin connector for the radio and the dual GA plugs 0.25/0.206 dia. The small plug is for the PTT harness.

The traditional aviation headset requires a special type of helmet with clearance for the ear muffs. Another option is to use a full face motorcycle helmet with speakers and mic installed.

I prefer the full face helmet when flying in an open cockpit like an ultralight. It protects the face in an impact (accident or bird strike) and also better protects the nose and mouth from insects. In addition, the output impedance of the ICOM A24 is 8 Ohms vs general aviation’s 130. So the David Clark headset would have limited volume to the ears. 

I attempted to use the Midland radio "kit", but the two pin plug is wired differently and not compatible with the ICOM. I attempted to rewire it, but the 28Ga wires were so small and fragile, I abandoned the effort and will go with a "NASCAR" stereo single 1/4" jack (RJS 600080174) setup with an adaptor to the dual GA jacks. 

The "NASCAR" setup from RJS needs an adaptor cable to go from single 1/4" jack to the dual GA setup as mentioned. I ordered the one that converts the "ultralight" single jack to dual GA. The "ultralight" wiring is used by Comtronics in their headsets. The setup did not work! Lot's of research and I found a wiring diagram for the "NASCAR" wiring. 

Seems that the "NASCAR" wiring uses the center "band" for the speaker and the tip for the mic.  I figured this was opposite from aviation, so I disassembled the adaptor cable and re-soldered the wires reversing the green and the red wires, essentially making the center band of the NASCAR jack connect to the tip of the aviation wiring jack/plug.  It worked!  I tested the mic by increasing the side tone and speaking into the mic to hear myself on the speakers. I will install in my full face helmet. I will need a 1/4" extension, female on one end and male on the other to run from my helmet to the adaptor cable and radio. I may be able to reach the transmit button on the radio, but if not, I will add a PTT switch that plugs into the ICOM adaptor wiring.

In addition to radio communication with controllers and other aircraft, I found it potentially useful to also enable cell phone communication. Bluetooth technology and voice control makes this feasible.  I tested these over the neck J-Lab earphones that see to fill the bill. They have Active Noise Reduction.  I can actually wear them inside the speaker equipped helmet and/or the David Clark headset. 

Finally, another option for the radio use is to go with a handheld "speaker-microphone" used by police officers. Radio use is in an ultralight is usually much more limited than for general aviation. For years (headsets did not become popular for general aviation until the 1980's--I learned to fly in the 1970's using hand held mic and a panel mounted speaker in the cockpit.) pilots used a handheld mic for communication, And, even when wearing a helmet, the speaker is probably loud enough with proper placement in/next to the helmet. One issue is that you would probably not hear the speaker when "stowed" i.e. when not holding it, so it would be only useful when you intended to listen and talk rather than listen only. Could be an advantage in that you would not be distracted by non-applicable radio "traffic". We will see.

In flight testing will determine how these systems work while flying an Aerolite 103.

A third option is to use wireless Bluetooth technology from Sena. 

SR10-10 

SMH 10-11

Smart Helmet and Speakers/Mic from Sena

Navigation

Ultralights are required to obey FAA Regulations. One of the most important is the limits on airspace that require reasonably precise navigation. 

This can be achieved by using regular on line maps, including Google Maps with GPS and free VFR Sectionals at http://vfrmap.com or SkyVector.com/. SkyVector and vfrmap.com and Google Maps would only be available when connected to the internet via cellular or wifi,  In flight can be achieved without a cellular data plane by subscribing to ForeFlight or free apps AVARE for Android or FltPlan Go for Android or Apple. The free apps are a bit less capable in terms of all forms of flight info, but are very good for GPS navigation for any device where sectionals can be downloaded and stored. 

I carry a leg mounted device that holds an IPAD Mini equipped with GPS and FltPlan Go for this purpose. I carry an iPhone and I also have an android phone with Avare available. The phone's display is really too hard to read when flying. The leg mounted IPAD Mini works very well. 

Google Maps Satellite view provides another useful feature when flying an ultralight. You can identify clear farm fields along a route to insure you abide by regulations for avoiding populated areas and always having an appropriate contingent emergency landing site. Your GPS position will move on Google Maps and you can use the highlighted "favorite" dropped "pins" as a form of navigation for safety and to insure against flying into controlled space.

Here is a screen shot below. Notice the substantial limitations on airspace from: 1) Mode C Veil; 2) York Airport Class E to Surface; Lancaster Class D and Harrisburg TRSA. Still, with a range of only 50-70 miles on a tank of fuel, the range is limited anyway. In addition, ultralights are prohibited from flying over "populated" areas. In general, minimum flight over areas of this map should be at 2000-2250 MSL which will generally be 900-1200 feet AGL. The glide ratio of the Aerolite 103 is in the range of 6-7:1. e.g. 1000 AGL would allow a little more than a mile of glide to an emergency landing site. So generally on routes I expect I might fly, I identity sites no more than 2 miles apart. Over some areas, I will be flying higher at 2000 AGL (3000 MSL) to allow up to 4 miles between sites. (2 miles from center)

Here is a screen shot. The "pin" provide a safe and "legal" flight path to various airports in the area within "range". Shoestring is my home base.

From user feedback, I have concluded that the handheld radio using the "rubber duckey" antenna is inadequate, particularly for transmission. And, because of the challenge of providing an adequate ground plane for a whip antenna, I decided a dipole type is the way to go, and there are good reports about the homemade one in this article:

https://peter-ftp.co.uk/aviation/misc-euroga/2018-InvVeeAntenna4ULs_rev3.pdf

Mounted on wing

This dipole while effective is quite large and I was uncomfortable with the size and the mounting to the wing strut plate that is a very thin 0.080” aluminum. In addition, in order to mount the radio on the right side of the plane I would need more than ten feet of coax. Finally, I was warned that the wing location could be subject to severe interference from the engine's high tension ignition. 

So, I begin my journey learning the "art" of antenna design!  First, I bought a simple SWR meter. The SureCom SW33.

The rubber duck antenna with the ICOM A24 has a very good SWR when held in the person's hand. Essentially the radio's battery "box" and the person holding the radio form a ground plane--the SWR was an excellent 1.05.

But, in the plane, the person is not holding the radio and there is no room for a proper 300 sq. in. ground plane, so some form of "dipole" hybrid would be necessary to use the rubber duck remotely mounted. I came upon this article about a "tiger tail" in my search.

https://paratusradio.com/2020/08/building-the-tiger-tail/

In essence, a dipole leg in combination with the rubber duck. I followed his suggested length calculation of about 5% longer than "theoretical" and decided on a 24.5" marine grade insulated wire. I added three 300 ohm snap on "chokes" to the coax. I securely mounted the rubber duck on the nose and extended the "tiger tail" next to one of the structural tubes. This did not work--the aluminum tube "detuned" or absorbed the antenna's output. But, the antenna came alive when I moved it upward away from the tube to the 120 degree angle used by the earlier dipole design. I reduced the angle to 115 degrees to compensate for the change in impedance with a 10 foot coax.  The SWR was an excellent 1.08. 

When testing on 121.50 "emergency channel" I spoke with two airline pilots--one more the 80 miles in front at 33000 feet (a 4 degree up angle) and another about 30 miles behind. So the radio is transmitting with good range in two directions. I was also hearing traffic from a airport 12 miles away, but transmission from ground level to planes only 500-1000 feet higher, 12 miles away (less than 1 degree up) was probably being absorbed by ground terrain interference.  

Here is a picture of the antenna, and the radio mounting that holds the radio and the adapters:

Note angle between rubber duck and tail is 115 degrees

Back to the drawing board!  Antenna that worked great with engine off, picked up so much engine ignition noise from the high tension wiring that radio was unusable. My guess was the "hybrid dipole" wire "tiger tail" was a perfect receptor for the noise--directly from engine and through wires in dash panel mounted EIS. 

I disconnected the "tiger tail" and theorized that a wire mesh in the nose could serve two purposes: 1) Block the transmission of RF from engine since it would be above the downward pointing rubber duck-sort of a "Faraday Shield" ; and 2) Serve as a ground plane for the rubber duck. My friend Ricardo, tested the SWR as acceptable--in the 1.5-1.8 range for airband VHF frequencies. It was better for slightly higher frequencies in the 135-145 mhz. (By the way, the Surecom meter's SWR was inaccurate--the hybrid dipole had a SWR of 1.8, not 1.08) I used 1/8" steel wire mesh, connected to antenna ground. I "insulated" it from airframe using a neoprene sheet and covered edges with tape to avoid cuts and inserted it underneath my "glove box bag" in the nose. The neoprene and tape also protected the clear nose poly from damage. 

It worked--Radio was usable with no noise using squelch of 18-19 of 24! Hearing transmission from 12 miles out. An in-flight test determined that my voice was not load enough when transmitting with my full face helmet (good with the David Clark headset)--assumed to be because the button mic in the helmet was too far from my mouth (David Clark boom mic has to touch mouth to work well)---modified helmet with a sculpted foam adaptor, attached with velcro moving the mic to just touch my lips which should correct this. 

Any additional noise reduction will have to come from shielding ignition related wiring. The NGK plugs are resistor type.

https://www.zippertubing.

https://www.ngk.com/ngk-2086-cr8hsa-nickel-spark-plug

At some point I may have a custom adapter cable set up made. Currently there are a lot of connections. The ICOM to GA .250/.200 dual; .250/.200 dual to single .250 female "ultralight"; 3 foot 1/4 male/male stereo jumper; 1/4 female/female adapter; NASCAR male 1/4 to speakers and mic in helmet. I may also consider using CEP "in the ear" speakers. 

Here is a picture of the push to talk mounted on the yoke, using tubing mounted to seat as a "conduit" for the wire. And the finished full face modular helmet with NASCAR speakers and mic installed. 

Here is a pic of the final modifications to the helmet. Speakers slid into pockets provided by helmet maker--wires tucked under padding. The green foam is the mod for the button mic to place it on the lips when modular helmet chin piece is lowered and locked.