View Full Version : 737-800 roof antennae
Hi all,
I'm not sure if this is the correct forum, but please could somebody explain to me what the large (maybe 12 inch ish) slightly raised white antenna on the roof of all -800s is for? (its situated above approx the 2nd row of windows), and if there are two variants of this antenna? some appear round and raised,others more elongated and raised?
thanks!
sb_sfo
24th Oct 2010, 15:45
It's a SATCOM antenna, you'll see it on most newer aircraft, particularly if they offer DirecTV or similar to pax.
Thanks...I'm not sure if thats the one I'm referring to-the SATCOM is usually lager (a few feet long?) and located further aft? I know on the 744s its halfway down the spine of the a/c.I'm talking about a smaller antenna, possibly dinner plate size, located on the roof just aft of the front pax door.
190
grounded27
24th Oct 2010, 16:27
that would be TCAS "size of a dinner plate"
iflytb20
24th Oct 2010, 16:37
http://farm2.static.flickr.com/1417/5111170318_ca737352f6_z.jpg
Do you mean this one??? IIRC that is the TCAS antenna
EDIT: Sorry grounded27. Did'nt see your post :}
Yes, THATS it! Now are there two different makes of this antenna? Two different shapes?
ampclamp
25th Oct 2010, 11:07
You could make it any shape you like as long as the little antennas inside are configured in the correct way and it is aerodynamic.
Just for the info of readers not in the game TCAS has an upper and lower antenna.
Yes, THATS it! Now are there two different makes of this antenna? Two different shapes?
As far as I know, these days, they only come in this shape. I presume they need to be circular to provide the 4 quadrant radiation pattern.
The Concorde may have been different, however, due to drag/heat considerations(?)
Do you have any photos of the kind you saw?
grounded27
26th Oct 2010, 01:27
The most common, recently the only in my experience is the dish shape. 4 lobes for 4 directions, 1 ea coax connected to each, makes interesting if connected incorrectly as it displays traffic in reference to the connection. Think the round ant is absolutely most common.
The uppers are of course the most troublesome.
Capt. Inop
26th Oct 2010, 04:07
It's a SATCOM antenna, you'll see it on most newer aircraft, particularly if they offer DirecTV or similar to pax.
Nah, it's the TCAS antenna, the SATCOM antenna is larger and located further back, just about above the wings.
Thai Pom
26th Oct 2010, 04:31
The round design is the Old Honeywell (now L3) design. The square-ish one is used is used by the Allied Signal and Collins installations.
Just to confuse you more AlliedSignal is now Honeywell :) This means that on newer installations the Honeywell one is now square-ish too.
Cheers, TP
minstermineman
26th Oct 2010, 15:01
What in that Photo is marked by the red 90 degree corners above RW in airways ? No opening there - is it a cutting point for emergency service use - something like that ?
Gulfstreamaviator
26th Oct 2010, 15:44
in case of emergency services, they cut here.....
glf
demomonkey
26th Oct 2010, 15:49
The red corners denote the cut in panels. These are designed for emergency access by the emergency services and allow rapid access to the interior clear of obstructions such as structural or service elements (ribs), electrics, hydraulics, flight controls etc. Although in this instance it seems like it is the fast way to gain access to the overhead lockers?!?!? That will be a surprise for the firemen.
Maybe someone will dig out the official wording but essential 'in case of emergency, cut here'.