Parts of the Aircraft


You should be able to identify all the antennae on your airplane.

ELT and comm antennae

(I don't care if you call them antennas: I just like Latin plurals). They show up more clearly on a real airplane then they do at 75 dpi on a web page, just look for them on your next preflight inspection and ask your instructor to verify your identification.

You should see one or two metre-long antennae sticking up and back out of the roof of the cockpit. These are the antennae for your VHF communication radios, the ones you use to talk to traffic and to control towers. You'll have at least as many of these as you have radios. (If you have more, your airplane used to have more radios).

Another spindly antenna should stick out of you airplane above where your ELT is installed, assuming you fly an airplane with a fixed ELT. Flight training airplanes aren't required to have ELTs but most do. If you have your own airplane, it's a good idea to periodically check that your ELT is actually attached to this antenna by doing an ELT check in conjunction with someone parked at the other end of the field: sometimes corrosion damages the connection and ELT transmission range is drastically reduced. Remember that ELT checks are restricted to the first five minutes of an hour.

A USAF C130 pilot wrote to tell me that his aircraft uses the VHF antenna depicted above as an ELT antenna. That makes perfect sense, as an ELT transmits on a VHF frequency, and the comment serves as a reminder that your aircraft equipment may look different but do the same job.

If you have a VOR installed in your airplane, you should have two antenna extending back from the top of your tail. Together the two form a horizontal V, making it easy to remember that they form the VOR antenna.

VOR antenna on tail

The ADF sense antenna does not show up well in photographs, because it's a long skinny wire that goes from the top of the tail to the roof of the cabin. I have marked the picture below to show where the antenna is.

The sense antenna works in conjunction with an ADF loop antenna, a flat square box mounted on the belly of the airplane, shown below.

Belly antennae

If you wonder why it's called the loop antenna, look at the picture of the DC-3, with its loop antenna circled in red. I spotted this one hanging from the ceiling at the Air and Space Museum of the Smithsonian Institute in Washington DC, and spent quite a while hanging over a balcony trying to get a properly lit shot. You can see that the old style ADF  was clearly a loop. There's still a loop inside that flat belly box; the avionics engineers have just figured out how to make it more compact.

Loop antenna on a DC-3

The OAT probe marked on the Piper in the third picture above is not an antenna, but a temperature sensor (OAT stands for Outside Air Temperature). The OAT probe on a Cessna is located inside the wing root opening for the  right side overhead cabin air vent.

You can see a picture of one sort of transponder antenna on the vents page of this section. A transponder antenna can also look like a little shark fin sticking down out of the belly, about 4 inches long. If you have two shark fins, the other one is probably a DME antenna.

GPS antenna on Piper

A GPS antenna is usually a little pod, about the size of your hand, flat on the top of the aircraft. Other (portable) GPS units attach their antennae to the inside of the windscreen with suction cups.

Jim Weir posts some antenna physics for pilots that explain why some antennae are vertical and some are horizontal. He also has some better antenna pictures than I do.

I've done some editing to this page to stop the pictures and text from overlapping in some browsers. Please let me know if you have any problems viewing it.

This page written 11 November 2003 by Robyn Stewart. Last updated 20 February 2004.
Copyright 2003 Flying Start Initiatives

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