Fly The Wing

This is another in our continuing series of “Know Your Airplane” articles, designed to help you better understand the components and systems on your airplane. As a Private Pilot, you probably know what most antennas on your airplane are. If you’re working toward your Instrument or Commercial rating, you better know what they all are, and whether they are discrete or redundant.

Communication - There is one for each radio. Generally both are on top of the aircraft, but you might have one on top, one on the bottom. In this case, determine which goes to which radio (top would be better for ground comm; bottom better for tower/enroute communication).

Navigation - Cat whisker nav antennae (below) are poor at receiving signals from the side; they are generally for aircraft that fly low and track directly to/from a station.

Blade-type mounted (below) are found on many newer Cessnas . Unlike the Comm system,

where each radio has its own discrete antenna, both Nav receivers use the same antenna feed.

Transponder - Two types; always on the bottom of the aircraft. Keep them clean from oil/debris… it will affect range. The ‘stick

and ball’ type is more prone to rain and static degradation. The blade type (right, below) is more suitable for higher speed airplanes and bad weather (IMC).

DME Antenna - As DME operates in the 960 - 1220 MHz frequency range, and Transponders receive/transmit at 1030 and 1090 MHz, the same antenna can be used by either device. You may need an Avionics or Maintenance Technician to tell you which is which, if you really want to know.

Marker Beacon - Blade-like (below, top); some Cessnas use the protruding tube from a flat plate (below, bottom). They’re always mounted on the bottom of the fuselage.

GPS antenna - Mounted on top of the fuselage to minimize signal blocking from the airframe. Like all antennas, they should not be painted over, and should be kept clean.

When you see a GPS antenna inside the airplane (generally on the glareshield or in the rear window), that’s a good indication that the GPS unit connected to that antenna is not IFR approved. If the Garmin GPS (430/530) in your airplane does not have GA-35 antenna, then that is most likely a non-WAAS approved GPS. If it does have the GA-35 antenna, be sure to look in the aircraft records for a notation that the GPS is WAAS-enabled (and furthermore, that it may be approved for LPV approaches). This has nothing to do with whether the database in the GPS is

updated or not; it relates to the firmware version (3.30 or later, dated 07/09 or later) in the actual GPS, and the external antenna (and antenna cable) that is required to utilize WAAS signals for IFR approaches. Essentially your GPS must be TSO-145A or later to even be WAAS-enabled; TSO-129 is a sure sign that it is not WAAS-capable.

Sometimes in newer aircraft the GPS antenna is incorporated into the Com antenna (above).

ELT antenna - Almost always on top of fuselage; sometimes buried in tail or may look like a small com antenna.

ADF Antenna - ADF’s are few and far between these days. In the old days, if I had a choice between two airplanes to rent and

one had ADF, I would pick that one, as ADF allowed you to listen to the ballgame during your flight on the AM radio band. Modern airplanes with ADF will most likely have a loop antenna mounted on the belly of the plane (left).

You’ll still see some older airplanes with the old “clothesline” sense wire; a single wire strung between the tail and the top of the cockpit.

Newer loop antennas incorporate the sense mechanism as part of their design.

Stormscope - You’ll find a BF Goodrich Stormscope (lightning detection) on any Cessna with a Nav-II avionics package. The antenna (top, below) is mounted on the belly of the plane. L3 also makes a lightning detection product; their antenna (bottom, below) is very similar in appearance to the Stormscope antenna.

Onboard Weather Radar - If you have this on your airplane (lucky you), you would probably already know what this is!

Read more about general aviation antennae in this AOPA article: Click here.

4/14/14