One day in the late 1990s a
corporate jet was talking to the enroute air traffic control center.
Center said, "Cleared GPS approach to Cambridge. Report on the
ground by telephone or missed approach this frequency."
CAMBRIDGE DORCHESTER AIRPORT
One day in the late 1990s a
corporate jet was talking to the enroute air traffic control center.
Center said, "Cleared GPS approach to Cambridge. Report on the
ground by telephone or missed approach this frequency."
GPS is the Global Positioning System. It is a space-based radio positioning, navigation, and time-transfer system. The system provides highly accurate position and velocity information, and precise time, on a continuous global basis, to an unlimited number of properly equipped users.
This was a new and simple navigation system, but not understood very well. Hunters and hikers bought little hand- held, battery powered devices for less than two hundred dollars. Ordinary people used them to blaze a trail back to where they left the station wagon. Finding the runway in a corporate jet was just as easy.
To understand GPS navigation you must think three-dimensionally. Consider the earth, the airplane and those GPS satellites as a cluster of things in space. Only the airplane needs guidance to the runway.
Three or more satellites determine where this object called an airplane is in relation to a larger object, the earth. Take the Cambridge Airport runway and place it in orbit. GPS guidance can give sufficient information for your airplane to dock with it, right out there in space.
That is exactly what the airplane is doing when it performs the approach. It is docking with a very large object called planet Earth, placing its wheels on a paved surface. Trees and crops do not accommodate that maneuver very well.
When you want an airport certified for GPS approaches, National Geodetic Survey people determine exactly where your airport is in space. They even drive down the runway with sophisticated instruments and create a three dimensional profile of the runway, undulations, bumps and all.
Since the GPS satellites are controlled by the United States military, accuracy can be degraded. When the system is working perfectly, your airplane thinks it is within a space 60 feet wide and 90 feet tall. The actual figures are 58.4 and 90.9, but can be degraded by the military to an accuracy of 328 feet wide and 512 feet vertical.
A very clever way to overcome this is having a black box on the ground that knows where it is located, at all times. Whenever the GPS satellites begin telling it something else, the misinformation is broadcast to aircraft through a different satellite uplink. Corporate jets and other airplanes keep hurtling toward runways, making happy approaches.
That day at Cambridge our corporate jet's crew acknowledged Air Traffic Control's clearance for GPS approach and performed a routine landing.
"Nice airport," remarked the co-pilot.
The Captain added, "This airport was built to accommodate corporate aviation."
"How long ago?"
Good question. The airport now has a four thousand feet by seventy five feet runway, lengthened and paved since its humble beginnings in 1952.
The Captain answered, "The Korean War was going on and a specialized electronics company wanted to build a factory here."
"Nice idea. Good reason to build an airport."
I got curious about the airport one day when I discovered Mr. Stephen Randall from the National Geodetic Survey doing a GPS Approach Survey.
"What are you doing?" I asked and snapped a photograph of him. He had a yellow tripod set up with a disc antenna on top. Beneath dangled a plumb bob dead center over a bench mark.
Mr Randall answered, "Surveying Cambridge Airport for a GPS approach."
Then and there I decided to research and write a story about Cambridge Dorchester County Airport. I was told to contact Mr. Elvin Thomas, head of the Airport Commission.
Mr. Thomas very kindly invited me to the next Airport Commission meeting, held in the conference room at the airport. Two other visitors received special invitations, Mr. Russell Smith and Donald Holdt, the two men responsible for Cambridge having an airport.
I was introduced at the meeting by Mr. Thomas as someone researching the airport story for Maryland Aviation Historical Task Force. He allowed me to ask my questions before the start of regular airport business.
I had only two, "Who was responsible for building the airport and when?"
Russell Smith said, "I was the mayor of the city of Cambridge 1952-1960. Donald Holdt of Airpax Corporation came to me and said he wanted to move his factory to Cambridge."
They did it on a handshake. The city owned a waste disposal area near some farm land. The original runway was a 2800 foot grass strip.
Donald Holdt said, "In 1952 Airpax electronics was at Martin airport building something that converted DC to AC and back to DC. Micro-voltages. Martin 202 airliner had an outlet in bathroom where you could plug in an electric razor, using our devices."
The Korean War was going on and they were making a critical product. The Department of Defense got upset, because Martin plant was a primary target area. Holdt was told to move 50 air miles away from Martin.
At that time Holdt's company had about two hundred employees. He drew a 50 mile circle around Martin. Cambridge fell just outside the circle. He decided in August 1952 to relocate Airpax Products to Cambridge.
Airpax now is a division of Phillips Electronics, on Woods Road. When transistors came along, the price of the product dropped from ninety-five dollars apiece to something like ninety cents. It was time to sell the company.
As a hedge against that, Airpax got into the circuit breaker business for the United States Army Signal Corps. They built ten thousand, delivered a thousand, put all the rest in stock along with the tools, so the government will have it off-the shelf if it is ever needed in a war.
There was a travel problem getting from Martin Airport to Cambridge. You could only travel by ferry boat way back then. It took about two hours to get across the Bay.
Holdt decided the only way to solve the travel restriction was to fly. He owned a Piper Pacer and learned at Rutherford field. That is where he went solo.
After relocating to Cambridge, he taught Mayor Russell Smith how to fly.
Mayor Smith said, "It was just a farm. Near the city dump. Holdt said they would move the business here if we had an airport."
Smith and Holdt shook hands on it and airplanes started using twenty-eight hundred feet of land that had been growing tomatoes and beans. Cambridge owned the city dump and there was a paved road going by that area. The mayor and city council agreed to buy the farm land.
Elvin Thomas said, "Around twenty-five years ago the runway was paved to its present dimensions, four thousand feet long and seventy-five feet wide." Then he provided a list of capital improvements listed below.
Cambridge Airport was originally built to accommodate corporate and business needs. Corporate and private airplanes visiting Cambridge Airport will continue to have the most modern of instrument approaches.
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History
1.) Property surveyed in February 1981. Total of 183.69 acres. Last purchased 13 1/2 acres from Leo J. Cormier in 1974, North end of property.
2.) Name was changed when County took over airport in January 1979.
3.) Amp-Air is an FBO, also Skytech, Aircraft Refinishers.
4.) Improvements
a.) 1974 - Hangar (Jet America) constructed $250,000.
b.) September 1980 - Constructed 2300 linear feet of taxiway, north end, 30 feet wide, 5 inches asphalt pavement section, $251,000
c.) June 1981 - Constructed 1700 linear feet of taxiway, south end, 30 feet wide, 5 inches asphalt pavement section, $160,000.
d.) 1983 - Poured concrete floors in old T-Hangars, $10,000.
e.) December 1983 - Installed new lights/wiring, VASI, REILS, runway edge lights, $80,000.
f.) June 1984 - Apron extension to the north, $115,000.
g.) September 1984 - Constructed maintenance hangar, $270,000.
h.) 1984 - Blacktop apron in front of old T-hangars, $60,000.
i.) August 1986 - New 12 unit T-hangar constructed, $135,000.
j.) December 1986 - Apron expansion (south) $123,000.
k.) 1986 - Chesapeake College opened aircraft mechanics school.
l.) 1987 - Obstruction removal, $80,000.
m.) July 1988 - Opened restaurant, Charles Powell, owner/operator.
n.) September 1988 - Parking lot for restaurant $15,000.
o.) Past 8 - 10 years on-going drainage improvements and leveling of old dump site.
p.) 1993 - Constructed 12 T-hangars (2 large).
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