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Hpgrmln
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Username: Hpgrmln

Post Number: 340
Registered: 06-2007
Posted on Wednesday, January 16, 2008 - 7:37 pm:   Edit PostDelete Post   Move Post (Moderator/Admin Only)

I heard about this from a friend awhile back and just found it today. There is a small, windowless shack surrounded by a fence. It has an unusual antenna on the ground and a wire running overhead. The warning sign said the facility is used for air traffic control and any tampering or tresspassing can result in loss of life to pilots. I contacted 2 pilots in the family and they are unaware of what it is and could not find it on flight charts. Strangely, it is located out in the open behind an elementary school, in Rosies Park. It is rougly near 11 Mile and Dequindre. Does anyone know what this building is used for and if there are any others in the area?
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Gene
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Username: Gene

Post Number: 39
Registered: 10-2006
Posted on Wednesday, January 16, 2008 - 8:16 pm:   Edit PostDelete Post   Move Post (Moderator/Admin Only)

If its the building off Hales street in Mad Hgts it has something to do with sending a signal to planes landing at City and Metro, as was told to me by a fellow who used to live across the street from it.
If anyone cares an underground spring comes to the surface along the east border of Rosies Park by Park Court.
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Jimaz
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Username: Jimaz

Post Number: 4307
Registered: 12-2005
Posted on Wednesday, January 16, 2008 - 8:21 pm:   Edit PostDelete Post   Move Post (Moderator/Admin Only)

Possibly some kind of LORAN antenna?
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Jimaz
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Username: Jimaz

Post Number: 4311
Registered: 12-2005
Posted on Wednesday, January 16, 2008 - 9:47 pm:   Edit PostDelete Post   Move Post (Moderator/Admin Only)

Is this the shack?:


Antenna
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Mikem
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Username: Mikem

Post Number: 3555
Registered: 10-2003
Posted on Thursday, January 17, 2008 - 12:51 am:   Edit PostDelete Post   Move Post (Moderator/Admin Only)

That is a compass locator/outer marker beacon for the instrument approach to runway 15 at Detroit City Airport. These facilities are usually placed 4-7 miles from the end of runways which have precision approach procedures, and mark the spot where the final descent to the runway begins.

There are actually two facilities in one at this spot: a marker beacon and a compass locator. The marker beacon transmits a narrow signal vertically, and when an aircraft flies over it, a flashing blue light is triggered and a beeping sound can be heard over a radio speaker. The shack probably has what looks like a rooftop television antenna, Y-shaped, pointed upward - that would be the marker beacon transmitter. The compass locater is the wire; it probably stretches for a dozen feet or more to a nearby wooden pole. It transmits a low-powered unidirectional signal. A different receiver on the aircraft can be tuned to it and a compass-like needle will point to the facility.

This particular one is named "MADDS", short for Madison Heights. On the chart found at this link, MADDS is in the center, represented by the lenticular shaped symbol. 338 kHz is the frequency it transmits on. Morse code for the letters "DE" are what you would hear when tuned into it. (It used to be named "Detroit", hence the DE, but its name was changed in the past couple of years.)

On the shoreline of the Detroit River, you will see another one called CARLG, frequency 230 kHz, identifier VQ. It serves as the compass locator for the instrument approach to runway 33 (opposite direction of 15).

Most of these are being phased out across the country. They are relics from the 1940s or earlier. Instrument approaches like these usually had another marker beacon, called a middle marker) closer to the runway at the point of minimum descent where, if the runway were not in view, the approach would be abandoned and the aircraft would climb back up to either make another try, or go somewhere else. For this approach to runway 15, the middle marker was located on the east side of Van Dyke where the railroad tracks cross by Mt Olivet Cemetery. It has been phased out, but the shack is still there.
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Mrnittany
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Username: Mrnittany

Post Number: 5
Registered: 10-2007
Posted on Thursday, January 17, 2008 - 1:04 am:   Edit PostDelete Post   Move Post (Moderator/Admin Only)

Yep ... it sends signals to planes coming into land at CITY airport via ILS (Instrument Landing System). ILS is a ground-based instrument approach system which provides precise guidance, via radio signals, to planes approaching a runway, thereby allowing landing even in bad weather/low visibility. ILS consists of 3 different beacons that an aircraft aligns itself w/ to land: the outer beacon about 7 miles from the runway, a middle beacon within a mile of the runway, and an inner beacon at the runway.

Specifically, this particular signal is the outer beacon for planes set to land on runway 15 ... the larger of City's 2 runways.

ALL medium-sized and above airports are equipped with ILS. These types of buildings are all over the place, if one knows where to look.
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Mrnittany
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Username: Mrnittany

Post Number: 6
Registered: 10-2007
Posted on Thursday, January 17, 2008 - 1:06 am:   Edit PostDelete Post   Move Post (Moderator/Admin Only)

Well ... took 15 minutes typing my post and someone else beat me to the explaination!
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Hpgrmln
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Username: Hpgrmln

Post Number: 341
Registered: 06-2007
Posted on Thursday, January 17, 2008 - 7:53 am:   Edit PostDelete Post   Move Post (Moderator/Admin Only)

Thanks.
Everyone seems to be in agreement, so I think it's safe to say thats what it is.
I'll have to keep my eye out for the spring.
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Lowell
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Username: Lowell

Post Number: 4472
Registered: 10-2003
Posted on Thursday, January 17, 2008 - 10:55 am:   Edit PostDelete Post   Move Post (Moderator/Admin Only)

Fascinating! Welcome to the forum MrNittany. It is great to have another aviation expert to join our all star MikeM. Your post complemented his perfectly.

Both answered a lot of question for me and I will be thinking about those three beams the next time I descend into DTW out of a cloud bank anxiously awaiting the first appearance of earth.

Question: what would happen if one ILS beacons went out at that time.
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Tiorted
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Username: Tiorted

Post Number: 112
Registered: 02-2006
Posted on Thursday, January 17, 2008 - 12:41 pm:   Edit PostDelete Post   Move Post (Moderator/Admin Only)

is this what you are talking about?

http://maps.google.com/maps?q= &ie=UTF8&ll=42.49485,-83.09338 4&spn=0.001373,0.00339&t=h&z=1 9&om=0
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Mrnittany
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Username: Mrnittany

Post Number: 7
Registered: 10-2007
Posted on Thursday, January 17, 2008 - 5:31 pm:   Edit PostDelete Post   Move Post (Moderator/Admin Only)

"aviation expert" ..... HA! I only know some stuff because my brother has a small plane license and I've been up with him, and I play a lot of flight simulator!

FWIW ... here (I am 95% certain) is one of the ILS beacons for planes approaching Pontiac airport from the west:

http://maps.google.com/maps?f=q&hl=en&geocode=&time=&date=&ttype=&q=waterford,+mi&ie=UTF8&ll=42.662535,-83.547214&spn=0.001414,0.002494&t=h&z=19&om=0

(Message edited by Mrnittany on January 17, 2008)
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Mikem
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Username: Mikem

Post Number: 3556
Registered: 10-2003
Posted on Thursday, January 17, 2008 - 11:41 pm:   Edit PostDelete Post   Move Post (Moderator/Admin Only)

Tiorted, yes.

Lowell, the beacons which mark your progress along the approach path are not that important. They are leftovers from the days before air traffic control had extensive radar coverage. In some cases, the failure of one would mean an increase in the visibility and/or cloud ceiling required for landing. The other elements of the ILS are more important: the localizer and glide slope transmitters. These provide the lateral and vertical guidance for your descent. A failure of either of these during an approach would be cause to abandon the landing. You could then use a different approach from a different navigation aid to the same or different runway, or go land elsewhere.

Here's a picture of the middle marker for runway 15 at City Airport. The shack contains the electronics and the signal is (was) transmitted from the orange antenna behind it. I believe it's been decommissioned since it's not depicted on the chart. (Scrappers will probably have it cleaned out by this time tomorrow.)


KDET ILS15 MM
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Hpgrmln
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Username: Hpgrmln

Post Number: 344
Registered: 06-2007
Posted on Friday, January 18, 2008 - 7:51 pm:   Edit PostDelete Post   Move Post (Moderator/Admin Only)

That almost reminds me of a refrigerator!
The one on Hales is a little larger and it has a ground-mounted "Y" shaped antenna, but its definitely the same thing.
Does anyone know the locations of these for the Metro runways?
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Mikem
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Username: Mikem

Post Number: 3557
Registered: 10-2003
Posted on Friday, January 18, 2008 - 9:35 pm:   Edit PostDelete Post   Move Post (Moderator/Admin Only)

EMMIT OM 27L KDTW

HURON OM 03R KDTW

SCOFI OM 21L KDTW This has a street level view of the transmitter.

REVUP LOM 04R KDTW

ILPUT OM 22L KDTW

SPENC LOM 27R KDTW

OM = Outer Marker
LOM = compass Locator/Outer Marker

The CARGL compass locator for Detroit City's runway 33 is on the canal serving the Bayview Yacht Club, on the Detroit Edison side. You can its "top hat" antenna. In this installation, there is a compass locator only - no outer marker beacon:


CARGL



The top hat differs from the wire antenna such as the at MADDS, which stretches between these poles, but it functions in the same way:


MADDS


(Message edited by MikeM on January 18, 2008)
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Livernoisyard
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Username: Livernoisyard

Post Number: 4877
Registered: 10-2004
Posted on Friday, January 18, 2008 - 10:57 pm:   Edit PostDelete Post   Move Post (Moderator/Admin Only)

If somebody goes really far back--WWII to the 1950s--there were the Adcock ranges incorporated with the LF beacons.
quote:

ADCOCK RANGE - National radio navigation system replaced after World War 2 by the omnirange system. It consisted of segmented quadrants broadcasting Morse Code "A" (dot-dash) and "N" (dash-dot) signals in opposing quadrants so that pilots could orient their position relative to a "beam" broadcasting a steady tone, and a Morse Code station identifier. Using a "build-and-fade" technique, a pilot could (ideally) pinpoint his location by the strength or weakness of a signal.


If one was off course, the pilot would hear either an 'A' or an 'N'. I knew an old-time electrical engineer in Wisconsin who built some Adcock ranges. After he retired, he manufactured very expensive (richelieu banjo) banjos in Oregon WI--south of Madison--about a mile from the farm where I lived.
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Lowell
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Username: Lowell

Post Number: 4474
Registered: 10-2003
Posted on Friday, January 18, 2008 - 11:02 pm:   Edit PostDelete Post   Move Post (Moderator/Admin Only)

Great info MikeM. Thanks a lot. You are part of the reason why I always fly Northwest.
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Mikem
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Username: Mikem

Post Number: 3561
Registered: 10-2003
Posted on Friday, January 18, 2008 - 11:31 pm:   Edit PostDelete Post   Move Post (Moderator/Admin Only)

Yes, many of the old radio ranges were later converted to compass locators, using the same frequency and identifier. The purple swaths on this chart from 1946 depict radio range courses.







As LY's quote explains, the range broadcast the letter A in Morse Code (· - ) in two opposing quadrants such as northeast and southwest, and the letter N in Morse ( - · ) in the other two. Listening to the range you would hear both letters, but one would be stronger than the other depending on which quadrant you were in. Get on the center of one of the courses and you would hear neither, because the overlap of the dot-dash and the dash-dot would produce one continuous tone. Pilots/navigators had to fly along for hours constantly listening to beeping in their ears, making continuous heading adjustments to stay on course.





(Message edited by MikeM on January 19, 2008)