Am transmitter site – Page 17

American Airlines Flight 723

File under: Why we check the tower lights every day (or have an automated tower light reporting system):

56 years ago, on September 16, 1953 American Airlines flight 723 flew between the center and northeast towers of the WPTR antenna system while attempting to land at Albany County Airport. The plane crashed about 3/10 mile away near NY route 5 (Central Avenue) killing all 28 persons on board. To date, this is the worst aviation accident in the Albany, NY area.

Several years ago while cleaning out different AM transmitter site, I found a bunch of files about this accident in the trash bin. It seems that some engineer had moved a file cabinet during the great consolidation of the 1990’s to the wrong transmitter site. In any case, I rescued the file and for your reading pleasure, have scanned the following documents:

Original telegram to FCC in Washington DC regarding tower/aircraft colision

Retel WPTR north and center towers struck three hundred foot level 0930 morning 16 September by American Airlines Convair. Damage inspected afternoon 16 September by representative Zane Construction and afternoon 17 September by engineer Ideco tower used in array. Both report slight damage to center tower requiring straightening above 300 foot level. North tower has two legs bent result of wing passing through tower 18 inches above top guys at bolt intersection. Tower above bent and twisted but all right unless subject to high east wind. Impact sheered north beacon clevises and shattered glass. Replacement ordered and beacon restoration expected early next week. Measurements of directional pattern afternoon 16 September show pattern unchanged and mulls, base currents and loop currents within tolerances except center loop current which reads ten percent low. Indications are center pickup loop has been jarred and pattern unaffected. FCC representative Turnbull who arrived noon Wednesday concurred. No time lost. Operating at full power

George Wetmore, Assistant Genl Mgr, Radio Station WPTR

This is the statement of the transmitter engineer on duty at the time of the crash.

Statement from the Engineer on duty at the transmitter site

I, Robert S. Henry engineer for Patroon Broadcasting Co. would like to make this statement concerning the collision of an American Airlines Plane with our transmitting towers.

On Wednesday morning September 16, 1953 I was on duty alone at the WPTR transmitter when at approximately 9:30 A.M. a low flying plane was heard overhead. The carrier trip circuit which protects the transmitting apparatus from sudden overloads at the antenna almost instantly actuated and a low sound of explosion followed about 3 seconds later. I ran to the back door of the transmitter in time to see what proved later to be aluminum sheets fluttering down through the fog. I estimate the ceiling at the time to have been approximately 75 feet and not sharply defined. The centre (sic) tower of our three tower array swayed violently for approximately for approximately (sic) 1 minute. At the time I knew a plane had hit the tower but it was above the ceiling and invisable to me. I called W. R. David and George Wetmore and the incident was reported to the Albany airport.

Back in these days, the studios were located at the Hendrick Hudson Hotel in Troy, the transmitter site was manned by a licensed transmitter engineer when ever the station was on the air.

What is amazing is that the IDECO towers remained standing after being struck by Convair 240, a pretty good sized aircraft.

Official report by the International Civil Aviation Organization:

American Airlines’ Flight 723 was a scheduled flight between Boston, and Chicago, with intermediate stops among which were Hartford (BDL), and Albany (ALB). The CV-240 arrived at Bradley Field at 06:57. Weather at the next stop, Albany, at this time was below the company’s landing minimums, but was forecast to improve to within limits by the time the flight arrived there. Departure from Bradley Field was made at 07:14. Because of poor visibility at Albany, several aircraft were in a holding pattern. The special Albany weather report issued at 07:50 indicated thin obscurement, ceiling estimated 4,000, overcast, fog, visibility 3/4 miles. Two aircraft left the holding pattern, attempted to land, but both executed a missed approach procedure. A third airplane landed at 08:16 following an instrument approach to runway 19. Immediately following this landing, Flight 723 was cleared to make an instrument approach to runway 19. Three minutes later the flight advised the tower that its approach was being abandoned because the aircraft’s flaps could not be lowered.
At 08:30 Albany Tower reported:”All aircraft holding Albany. It now appears to be pretty good for a contact approach from the west. It looks much better than to the north.” Flight 723 was then cleared for a contact approach to runway 10. On finals for runway 10, the Convair descended too low. The right wing of the aircraft struck the center tower of three radio towers at a point 308 feet above the ground. The left wing then struck the east tower. Seven feet of the outer panel of the right wing including the right aileron and control mechanism from the center hinge outboard together with 15 feet of the left outer wing panel and aileron separated from the aircraft at this time. Following the collision with the towers, ground impact occurred a distance of 1,590 feet beyond the tower last struck. First ground contact was made simultaneously by the nose and the left wing with the aircraft partially inverted.
The weather reported at the time of the accident was thin scattered clouds at, 500 feet, ceiling estimated 4500 feet, broken clouds, visibility 1-1/2 miles, fog.

PROBABLE CAUSE: “During the execution of a contact approach, and while manoeuvring for alignment with the runway to be used, descent was made to an altitude below obstructions partially obscured by fog in a local area of restricted visibility.”

The above reports notes that the aircraft traveled 1590 feet and struck the ground partially inverted. I do not know what the flaps up landing speed of a Convair CV-240 is but the cruising speed is 280 MPH. It would be safe to say the aircraft was traveling in the 120 to 130 MPH range or about 220 feet per second. At that speed, it was likely airborne for about 7 seconds after it hit the tower. Enough time to look out the window, realize what was happening and say “Oh, Shit!”

IDECO towers WDCD antenna system, northeast tower is farthest

IDECO stood for the Internation Derrick Company, they build cranes, derricks and bridges as well as radio towers. Apparently they made pretty good stuff because those same towers are still standing today.

Not that checking the tower lights would have averted disaster in this case, it appears to be pilot error compounded by bad weather that caused this incident. But there have been more recent aircraft/radio tower accidents, some of which have involved possible faulty tower lights. I wouldn’t want that on my conscience.

General Electric BT-25-A

This is one of my favorite old transmitter memories. Back when I landed my first Chief job, I was working for an AM/FM combo. The AM station was a 50,000 watt flame thrower that first went on the air in 1947. The original transmitter, a General Electric BT-25-A was still in service as a backup unit. These pictures are from the last night it operated, December 16, 1993. The bank made us remove all of the PCB transformers and capacitors before they would refinance their loan. Of course that was most of the transmitter, the rest of it was scraped or sold for parts.

This is a long transmitter, GE BT-25-A looking from the control cabinet

The transmitter takes up the entire span of the room. There were eight large cabinets, each with its own stage or section. The stages were connected to each other by a wiring trough in the floor. The transmitter used lead jacketed cable within and between sections.

The IPA section had been modified to use 833A tubes. This is where the RF was developed and amplified for the final section. It is in the middle cabinets of the transmitter, the audio and control section being to the left, the PA and PA power supply being to the right.

PA section. Those WL 5891 tubes. — PA section. Those are WL 5891 tubes.

Final section. There were three tubes, only two where in use at any given time. The third tube was a spare which could be quickly placed in service by throwing a knife switch and moving those bars on the back wall around. This picture was taken with filament voltage only, we had to close the door to turn on the PA voltage.

The transmitter was cooled by this blower which faces down into the floor. A concrete duct work carried the air to the various stages of the transmitter. The blower is powered by a 2 1/2 HP motor. There were two blowers, one in use and one is standby. Behind this is an air mixing room and filter room. During the winter time, the transmitter waste heat was used to heat the building by closing a series of ducts and opening other ones.

Modulation transformer and modulation reactor

This is in the transformer vault. The unit to the left is a modulation transformer, it was 7 feet tall. Directly in front is the modulation reactor and just out of the picture to the right is the plate transformers. The plate supply was 480 volts 3 phase. The other piece of green equipment is a hydraulic tube jack, to get the 5891 final and PA tubes out of their sockets.

The transformers where what contained most of the PCBs. The modulation transformer contained about 150 gallons of Pyranol, the GE trade name for their transformer oil. Pyranol contained greater than 750,000 parts per million PCB.

It is a shame we had to kill this transmitter, is sounded wonderful on the air. The day we signed it off, there was nothing like it, not the Mw-50B that replaced it, nor the Nautel ND-50 that replaced the MW-50, nor the DX-50 at the competing station across town.

What a shame.

Underground Electrical feeder burn out

In the never ending saga of things I have not yet seen, we had a 350 kcml 3 phase underground feeder burn out yesterday at our AM transmitter site.

Actually, it happened the day before, around noon. I received a call from the remote control that we were on the backup generator. Upon arriving at the site, I found several trees down on the three phase primary down the street. I figured that was the cause. After checking the generator fuel supply, oil pressure, temperature, phase volts/amps, I decided that everything was okay and the power company would be along shortly to restore power. I then continued up the road to our FM site to do weekly maintenance.

Upon returning to the office several hours later, I looked at the utility company website. They have a pretty cool interactive map application that shows all outages and give restoration times. The area around our transmitter site showed no outages, therefore I figured it had been cleared.

I committed two errors here:

Not calling the utility company myself to ensure that the outage was reported. I assumed that the tree across the three phase primary was the cause, it was not.
Not calling the transmitter site remote control to check the generator status after I checked the website.

To be honest, I don’t know if I am coming or going these days. With seven radio stations, each with it’s own transmitter site, three of them Directional AM stations, and three studio locations spread out over a 75 mile stretch, it is difficult to keep up with the small details. Did I mention that I am solo, the engineering assistant position was cut two years ago. But, I am not here to make excuses…

The net result is the generator ran all night long. The next day, when I checked the transmitter in the morning, I was surprised to find the generator still running. Unfortunately, I had an FM station on low power (see post below) that needed to be taken care of first. When I finished replacing the RF module in the FM transmitter, I made my way to the AM site.

I called the power company then checked the generator fuel, the propane tank was down to 10%. Yikes, better get this taken care of fast. I will say the power company showed up pretty quickly. After some measurements with a hand held meter, it was determined that the under ground feeder was open between the pole and the transmitter building.

The line man was not at all surprized, in fact, he called it before he even went up in the bucket truck. After some back and forth with his supervisor, who came out in a pick up truck, it was decided that they would run a temporary overhead feed to the meter can.

They also did some research in there records and discovered that they (the utility company) own the underground cable and therefore they would dig it up and fix it. That’s nice because otherwise it seems like it would be an expensive repair job. On a station that makes not a lot of money.

Tower down

You know it is going to be a bad day when:

a farmer mowing grass took a wrong turn on June 16, KFEQ AM lost a guy wire and eventually one of its four towers came toppling down

From Above Ground Level magazine.

Is hiring the farmer down the road to come and mow the AM field a smart thing to do? It depends, I suppose, on whether or not your towers will be standing afterward. Hopefully the guy had some insurance, if not then the station is basically screwed. The article did not mention that, although it did state that “The station is wieghing it’s options,” Which does not sound good.

The good news is at least they were doing the maintenance. Most AM stations these days don’t even bother to mow the fields. Look at this picture:

Tall grass at an AM transmitter site. Owner says don't cut it.

It is not that I don’t want the grass cut, I do. However, I am not going to pay for it out of my own pocket, that is ridiculous. So, it grows.