Flight inspection has long been a vital part of providing a safe airspace
system. The concept is almost as old as the airway system itself. The
first U.S. flight inspectors flew surplus open-cockpit biplanes, watching
over a steadily growing airway system predicated on airway light beacons
to provide navigational guidance. The advent of radio navigation brought
an increased importance to the flight inspector, as his was the only platform
that could evaluate the radio transmitters from where they were used:
in the air. With the development of the Instrument Landing System (ILS)
and the Very High Frequency Omni-Directional Range (VOR), flight inspection
became the essential element in guaranteeing the safety of the system.
Flight inspection developed through various government agencies charged
with air safety: the Aeronautics Branch, Bureau of Air Commerce, the Civil
Aeronautics Agency, and lastely, the current FAA.
Flight inspection in the U.S. began in function, if not yet in form, with
the development of an airway system in the late 1910s and early
1920s. The infant airways were created at the behest of the U.S.
Air Mail Service, then operated by the Post Office Department. The Post
Office developed the concept of the airway to provide a reliable means
of safely transporting the mail by airplanes on predetermined routes and
schedules. The term "airway" was very loosely construed, as
there was no actual route specified, nor were there any means of aerial
navigation provided. There were no aeronautical charts, no terrain or
obstruction information, and no radio capability for weather, communication,
or navigation, much less anything resembling air traffic control. There
was no civil aviation authority at either the state or federal level.
There were no flight rules nor, at that point, a real need for them. Airplanes
and pilots were unlicensed and anyone with a self-perceived skill could
build his own version of a flying machine and sell it to anyone who wanted
an airplane. With the lack of effective aeronautical navigation, operations
were limited to daytime flights in good weather, obviating most of the
advantages held by the airplane as a transportation medium. The mid-1920s
saw the beginning of federal navigational aids as efforts were made to
provide lighted airway beacons along the airways to allow safe nighttime
navigational assistance.
Drawing
upon the methods of marine navigation, airway beacons were developed by
the Post Office. The earliest lighting consisted both of rotating beacons
and fixed course lights. The beacons were placed 10 miles apart and the
1,000-watt lamps were amplified by 24-inch parabolic mirrors into a beam
exceeding one million candlepower. They were mounted onto 51-foot towers
anchored on 70-foot long concrete-slab arrows, painted black with yellow
outline for daytime identification and pointing along the airway. Course
lights were also mounted on the light towers, projecting a 100,000 candlepower
searchlight beam alng the airway course and flashing a Morse-code number
between one and nine that identified the individual beacon along a hundred
mile segment of airway. Intermediate landing fields were spaced every
30 miles along an airway. These fields were primarily used for emergencies
during poor weather or for mechanical difficulties. Pilots could locate
these intermediate fields at night by green flashing lights installed
on the nearest enroute airway beacon.
A transcontinental airway segment between Illinois and Wyoming was equipped
with the beacons and nighttime service was begun on July 1, 1924. Additional
segments were lit both east and west, and the entire route, from New York
to San Francisco, was completed in 1929. The passage of the Air Commerce
Act of 1926, transferred the airway system to the Department of Commerce,
which created an Aeronautics Branch with an Airways Division. The last
segment over the California Sierras, with the most difficult terrain was
completed by the new Aeronautics Branch.
With the installation of radio navigation aids, the Airways Division established
airborne flight inspection as a safety requirement and by 1932, six pilots
were employed by the branch as airway patrol pilots. These six pilots
and the operations they conducted were the real predecessors of flight
inspection as it is known in the U.S. today.
The first practical radio navigation aid, introduced in 1928, was the low frequency
Four Course Radio Range. The courses from several ranges could be aligned
to provide airway guidance. Pilots listened on their radio receivers to
the transmitted signals, a combination of a Morse Code "A" (dot-dash)
and "N" (dash-dot) letter, so that an on-course signal was a
steady tone. This new aid, rudimentary as it was, nonetheless created
the first all-weather airways. The four-course ranges required airborne
evaluation of the radiated signals, particularly in proper airway alignment
of the four courses (minor adjustments were made by imbalancing the power
output from the four antennas used to transmit the courses) and checking
for false courses.
An article in the Air Commerce Bulletin in 1933, explicitly outlined the
responsibilities of the new airway patrol pilot positions. In the description
can be seen the developing mission of flight inspection. It noted that
"their chief duties are concerned with such matters as checking relative
brightness and elevations of beacon light beams; orientation of radio
range courses and transmission of proper signals; correctness of speech
and transmission of weather broadcasts to planes in flight; operating
principles and procedure of airways radio stations in carrying on communications
with aircraft; reception of marker beacons and 2-way radio communication
service from the marker beacon stations; the functioning of the facilities
and condition of landing areas at Department of Commerce intermediate
landing fields, and investigation work pertaining to all phases of aeronautic
facilities on the Federal airways system."
Each of the airway patrol pilots were assigned 3,000-3,500 miles of Federal
airways to patrol. The pilots were assigned to a Lighthouse district and
patrol offices were established within that area. The Airways Patrol Headquarters
were scattered at offices spread across the country. A variety of aircraft
were initially assigned to the patrol pilots. The early patrol fleet apparently
consisted of five Bellanca Pacemakers, a Curtiss-Wright Sedan-15, several
Stearman C-3Bs, and three Stinson SM-8As. Three earlier Douglas M-4s were
phased out by the end of 1930. Most of the aircraft were utilized for
both airway survey work and airway flight inspection.
Patrol work continued in limited fashion through the balance of the 1930s,
constrained primarily by Depression-era budgets despite the mushrooming
air transport system and proliferation of radio navigation aids. The early
flight inspection fleet was nonetheless slowly supplanted by newer equipment
such as the Stinson SR-8B with an electrical system to handle required
radio equipment. In
1938, the Bureau of Air Commerce was reorganized as the Civil Aeronautics
Authority, with newly established administrative Regions given charge
of flight inspection within their own area. In 1940, the Civil Aeronautics
Authority gave way to the Civil Aeronautics Administration (CAA) establishing
an organizational framework that has carried forth to the current FAA.
With U.S. involvement in World War II looming, flight inspection remained
a relatively small organization within the framework of each of the regional
offices. Each of the eight regions was apparently allowed two patrol pilots.
The Flight Inspection sections, although administratively assigned to
the regions, continued to operate under the Office of Federal Airways.
The Chief Airways Inspector (Flight) was nominally in charge of establishing
flight inspection procedures and promoting standardized methods. Aircraft
assignment, dispatch and maintenance, however, was maintained by the Aircraft
Control Service that had jurisdiction over the entire CAA fleet, with
the exception of those at the Experimental Station.
Beginning in 1940, ten new twin-engine Cessna T-50 Bobcats were purchased
for use in the flight inspection fleet, and an additional five were purchased
in 1942. There is little information about how these aircraft were modified
for the flight inspection mission except that airway patrol pilots of
1944 found them woefully inadequate to perform the job. The
recorded minutes of a May 1944 Airway Patrol Pilot meeting termed the
assigned aircraft "entirely unsatisfactory, and in some cases, actually
extremely dangerous to use for this kind of work." It went on to
note that the aircraft created a "bad impression" among air
carrier pilots because the limitations of the Bobcats often precluded
facility checks in instrument weather or at night. The remainder of the
flight inspection fleet consisted of outdated Stinsons purchased in 1936
and 1937.
Other items of interest divulged in the minutes for that meeting was the
call for the hiring of a third airway patrol pilot in each region to help
relieve some of the workload. As of July 31, 1941 there were 30,913 miles
of airways with another 1,945 miles under construction. Since only 16
airway pilots were assigned to inspect the airway structure, and as the
radio ranges occupied most of their flight check time, there was little
attention given to the airway beacons or radio communication capability.
Also, newer inspection requirements for instrument approach and landing
procedures were seen as being neglected because of the lack of pilots.
Work had been progressing steadily since 1928 on the development of an
instrument landing system. In that year, the Bureau of Standards began
work on a system for the Aeronautics Branch, incorporating a low frequency
loop-type range localizer and position marker beacon. Lt. James Doolittle
then conducted a series of demonstration flights resulting in the first
successful blind landing on September 23, 1929. As the conversion to the
VHF frequency range was obviously desired, research continued at the Indianapolis
Experimental Station, Indiana, where the first modern VHF ILS installation
was demonstrated to the military and the airline industry in early 1940.
This system incorporated all the elements of the modern ILS, including
aircraft instrumentation, that remains in use today. The localizer signal
was standardized to use a VHF frequency in the range of 108 to 112 megahertz,
while the glide path transmitter utilized a range of 330 to 335 megahertz.
Two marker beacons, termed the outer and inner marker, each transmitted
on 75 megacycles and illuminated a purple and amber light, respectively,
in the cockpit. Also installed was a prototype runway approach lighting
system for demonstration.
Work had also progressed on converting the low frequency airway navigation
transmitters to the VHF band. The Visual-Aural Range (VAR) was the first
navigation range developed to utilize the higher frequency bands, but
even though the VAR system introduced both the VHF frequency band and
direct course read-outs to the airway navigational system, it was still
limited by the number of courses created by the transmissions. The VAR
system was installed on the New York-Chicago airway for demonstration
purposes beginning in 1941. However, the shortage of VHF equipment caused
by the war effort impeded the aircraft installations and minimized the
effect of VHF navigation through the war years.
The delay bode well for the development of the first truly versatile enroute
navigation system, that being the VOR, under steady development since
1937 but first deemed practical in late 1943. The creation of a rotating
radiation pattern transmitted simultaneously with a stable reference signal
created an unlimited number of possible courses and made true multi-course
VHF navigation a reality. A
frequency range of 112 to 118 megacycles was set aside for the new navaid.
The old four-course radio range was instantly made obsolete with the perfection
of the VOR, but continued difficulties in obtaining the electronic equipment
and industrial priority during World War II delayed equipment delivery
until 1944 and deferred the widespread installation of the VOR system
until the late 1940s and early 1950s. When the first VOR airway was established
in 1951, over 271 VOR units had been installed and commissioned. By June
1, 1952 over 45,000 miles of airways utilizing the VOR were in operation.
The advent of the ILS and VOR dramatically increased the importance of
flight inspection as each installation required extensive commissioning
checks and mandated regular rechecks of the transmitters. Instrument procedures
developed using the ILS and, particularly, the versatile VOR were such
that dependable instrument approaches would be possible at many smaller
airports not previously used for instrument flying. These procedures had
to be developed by the regions and flight checked by the regional flight
inspection sections, which only added to the potential workload. The regions,
however, remained saddled with inadequate aircraft without the electrical
systems, instrumentation, or radio equipment required to perform the job.
Both the installation of new navaids and the acquisition of suitable aircraft
to check them remained stymied by the mobilization required to fight World
War II.
With the end of the war in 1945, however, aircraft acquisition no longer
remained a problem. The U.S. military found themselves with over 75,000
usable aircraft at the end of the war, most of which were eventually scrapped
for their aluminum content. Before being released for disposal, surplus
aircraft were made available to other government agencies, and the CAA
obtained nearly thirty surplus Douglas C-47s and seventy-five surplus
Beech C-45s for agency use. At least one C-47 and several Beeches were
assigned to each of the regional aircraft fleets and utilized for flight
inspection. With the addition of these aircraft to the regional flight
inspection fleets, the airway flight inspectors finally had suitable aircraft
with which they could perform their jobs. Lack of standardization continued
to plague the fleet, though, as each regional office installed radio receivers
and other equipment to suit their individual needs. The development of
additional radio navigation aids also added to the demand for flight inspection
capability.
The installation of the VOR ranges went far to establish a reliable navigational
tool. However, without range information, which was not provided by the
VOR, accurate positioning was left to triangulating between two or more
VOR stations or using timed turns across several radials to approximate
range from the station. The CAA developed Distance Measuring Equipment
(DME) beginning in 1945 as the solution. Paired with the VOR ranges, the
pulsed signals from the DME station would provide a properly-equipped
aircraft with both azimuth and range information. The CAA planned widespread
installation of the DME beginning in 1948 and sought to establish the
VOR/DME combination as the international standard navaid for enroute navigation.
In 1950, the CAA placed 450 DME stations on order for pairing with the
VOR transmitters.
The U.S. military, while initially embracing the VOR ranges for navigation,
pursued the development of a purely military system operating in the higher
frequency range of 960 to 1215 megahertz. Termed Tactical Air Navigation
(TACAN), the system provided both the capability of the VORs azimuth
and the DME's distance information in a smaller package that was better
suited for shipboard installations and portable land-based operation.
The military and CAA could not agree on an installation standard, but
a 1957 presidential commission finally decided to favor the TACAN over
the DME, with VOR and TACAN transmitter co-located as VORTACs. The
TACAN component of the VORTACs would provided DME information to
civil aircraft. In 1959 the International Civil Aviation Organization
(ICAO) selected the VOR as the navigational-aid standard for the international
community.
Through the early 1950s, the CAA developed a series of ambitious plans
for the widespread installation of standardized navigational aids consisting
of VOR/DMEs for the airways, plus long-range and terminal radar
equipment and ILSs for airport approaches. The
continued growth of civil aviation and the advent of the jet airliner
soon pushed airspace problems into the headlines. Several major mid-air
collisions, including one over the Grand Canyon in June 1956, pressed
the Congress and federal government into making a dramatic new commitment
to funding air traffic and airspace improvements. By the end of 1956 an
overhaul of the system was begun, with a price tag in excess of $450 million.
For CAA flight inspection, the planned installation of hundreds of VORs
and ILSs demanded a dramatic increase in flight inspection capability.
Toward that end, the U.S. Navy eventually transferred forty surplus R4Ds
(DC-3) to the CAA for modification into the new "Type II" DC-3
flight inspection aircraft. The Type II DC-3 became the standard flight
inspection aircraft system wide for nearly twenty years, with the CAA
eventually operating nearly sixty DC-3s in its fleet. The prime mission
of the DC-3 fleet was envisioned to be ILS and terminal approach inspection,
plus the detailed commissioning inspections of all new facilities. Each
DC-3 operated with two pilots and at least one airborne electronics technician,
a crew concept that has carried forth to modern flight inspection.
Also, to explore how VORs and other navaids performed at the altitudes
new jet aircraft were now routinely flying, the U.S. Air Force agreed
to loan two Martin B-57 Canberra bombers to the CAA for high-altitude
use. The Air Force pulled two Boeing KC-135s from the production line
for fitting as high-altitude flight inspection aircraft for loan to the
CAA.
The Semi-Automatic Flight Inspection (SAFI) program was developed in
the late 1950s to perform long-range airway-type inspection. Five U.S.
Air Force C-131 Convairs were obtained and modified with DME positioning
information and computerized recorders. All five Convairs were modified
with the installation of Allison turboprop engines before they joined
the flight inspection fleet. The
SAFI program flew predetermined grids across the country looking at each
of the enroute VORTACs as part of the entire airspace system.
Before most of this new equipment had been delivered, Congress passed
the Federal Aviation Act of 1958 to overcome differences between the CAA
and the military over aviation matters. This legislation created a new
independent agency, the Federal Aviation Agency (FAA). The
FAA was separated from the Department of Commerce, and assigned the final
jurisdiction over civil and military aviation as they participated in
the national airspace system.
The new FAA faced many problems with the expanding airspace system, but
quickly established itself as a technically-proficient, competent authority
on aviation matters. In 1959, the U.S. Army and Navy transferred their
flight inspection programs to the FAA. The U.S. Air Force, under the prodding
of a 1962 Presidential executive order, developed a new sense of cooperation
with the FAA and, with "Operation Friendship," transferred much
of its own flight inspection capability to the FAA. This
transfer included its fleet of Douglas AC-54s, Douglas AC-47s, and Convair
AT-29s for the FAA to perform routine Air Force flight inspection. The
combat flight inspection mission was retained by the Air Force for its
Lockheed C-140 Jetstar-eqiupped flight inspection squadron.
One important international aspect of FAA flight inspection operations
during the late 1950s and extending through the 1960s, was the particular
emphasis placed upon foreign aid. Under the auspices of the Agency for
International Development and other State Department-administered programs,
foreign flight inspection programs were developed utilizing the training
facilities at the Aeronautical Center. DC-3s,
including several drawn directly from the FAA fleet, were modified similarly
to the Type II configuration by the FAA and delivered to the foreign governments
for flight inspection. In 1965, for example, nine DC-3s and DC-4s, obtained
both from FAA and military sources, were provided to the governments of
Columbia, Kenya, Mexico, and Vietnam for use in flight inspection or transportation.
Other countries that received such assistance over the years included
Canada, Spain, Brazil, Greece, Somalia, Argentina, and Chile. The FAA
was also instrumental in developing a portable flight inspection package
that many nations found more practical to use than establishing a dedicated
flight inspection aircraft fleet.
The early 1960s were primarily devoted to standardization of the
flight inspection mission across the regions and solidifying the gains
made in the late 1950s. Installation of new navaids continued at a rapid
pace. By the mid-1960s, FAA flight inspection remained organized at the
regional office level but was performed from nearly twenty Flight Inspection
District Offices (FIDOs) spread across the country. The SAFI program was
based at three Flight Inspection Field Offices (FIFOs), with the entire
flight inspection program administered from Oklahoma City, Oklahoma, by
the Bureau of Flight Standards within the FAA. Other aircraft employed
in the FAA fleet included five Lockheed L-749 Constellations for Pacific
and Far East flight inspection and several Lockheed TV-2s (T-33) for high-altitude
work.
In April 1967, another government reorganization occurred, with the independent
Federal Aviation Agency transferring to the new Department of Transportation
and becoming the Federal Aviation Administration. Beginning in the late
1960s an effort was made to consolidate the flight inspection fleet
organization with a smaller, more efficient fleet. The DC-3s, though still
reliable, were deemed too slow for the modern airspace system. Also, new
technology using inertial navigation with DME updating and computer analysis
was available that made the DC-3 installations obsolete. The FAA purchased
a fleet of fifteen Sabreliner 80s to replace the DC-3s, with an additional
fleet of five Sabreliner 40s for international work and five Aero Commander
AC-1121 Jet Commanders to supplement the Sabreliner fleet. The Sabreliner
80s were equipped with the new Automated Flight Inspection System (AFIS)
that utilized modern positioning technology with automated flight inspection
analysis. The AFIS eliminated the need for a ground based Radio Theodolite
Transmitter (RTT) operator.
In 1972, the entire flight inspection program was reorganized into the
Flight Inspection National Field Office (FINFO) and removed from most
of the regional organizations. With the delivery of the new jet fleet,
a dozen of the FIDOs were closed and consolidated to nine FIFOs, seven
located domestically with two overseas offices at Tokyo and Frankfurt.
In 1975, the FINFO was reorganized as the Flight Standards National Field
Office (FSNFO). By 1982, the last regional flight inspection program,
long fought-for and retained by the Alaskan Region, was brought into the
FSNFO. Shortly afterwards, in the flight inspection program was removed
from Flight Standards and incorporated into the new Aviation Standards
National Field Office (AVN). AVN later incorporated other elements of
Flight Standards including the Airmen and Aircraft Registry.
In 1978, the Microwave Landing System (MLS) was selected by ICAO as the
eventual replacement for the ILS. The FAA began MLS installations in the
early 1980s with flight check Sabreliners performing the initial commissioning
inspections of the new navaids. Industry resistance and the advent of
new satellite navigation technology has slowed the transition to the MLS,
but nearly two-dozen installations remain in service and require regular
flight inspection.
During the mid-1980s, in an effort to address fuel conservation
and the structural condition of the Sabreliner 80 fleet, a decision was
made to purchase a new flight inspection aircraft to replace the Sabre
80. Beechcraft offered a modified version of its Beechcraft BE-300 Super
King Air turboprop-powered corporate transport. In 1986 the FAA ordered
19 of the Super King with an upgraded AFIS system, with deliveries commencing
in 1988.
In 1991, the FAA assumed all of the U.S. Air Force flight inspection
mission and accepted the transfer of the six Hawker C-29s (BAe-800) Air
Force flight inspection aircraft into its fleet. The BAe-800s are utilized
primarily for international flight inspection, supplanting the last of
the FAA Sabreliners. Also, in 1991, the Aviation Standards National Field
Office became the Office of Aviation System Standards (AVN). Further consolidations
resulted in a structure of four Flight Inspection Area Offices (FIAOs)
located at Sacramento, California; Battle Creek, Michigan; Atlanta, Georgia;
and Oklahoma City, Oklahoma. Satellite offices are located at Atlantic
City, New Jersey and Anchorage, Alaska. An International Flight Inspection
Office (IFIO) was established at Oklahoma City to perform the world-ranging
FAA flight inspection mission.
With the 1990s came also the development of Global Positioning System
(GPS) technology, promising a new satellite-based positioning navigation
source now slated to replace many of the ground-based navigation systems
in the next decade. Hundreds of new non-precision instrument approaches
based on the new GPS technology are being developed and flight checked
each year, with work underway to add the capability of precision GPS approaches
with ILS-type approach minimums in coming years.
In the mid-1990s, the FAA flight inspection fleet was supplemented by
the purchase of a number of new Lear 60s and Challenger 601s,
bringing the total FAA flight inspection fleet today to eighteen Beech
BE-300Fs, six British Aerospace BAe-800s, six Bombardier Lear
60s, and three Bombardier Challenger 601s, each equipped with
an updated AFIS system utilizing GPS-positioning. Additionally, a number
of Beechcraft Barons are being employed for regional engineering test
programs for new navaid installations with portable flight inspection
packages installed as required.
Today, FAA flight inspection routinely inspects thousands of navaids and
instrument procedures, including ILS, MLS, VOR, DME, TACAN, GPS, NDB,
various radars, and airport lighting. Continued advancements in avionics
with Flight Management Systems (FMS) combined with GPS positioning and
other, new high-tech possibilities for aerospace navigational and landing
aids suggest an increasing role for flight inspection in the future. Despite
the relentless march of technology, there remains the same need for an
airborne evaluation of aviation navigation aids and procedures as was
established by the original air mail pilots over seventy-five years ago.
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