Project “Phyllis Ann” was a Top Secret classified program during the Vietnam War.
It consisted of three Squadrons of highly restored and modified C-47 aircraft.
These original 45 C-47 aircraft were predominantly 1940 to 1942 vintage C-47D
aircraft that were first taken down to an contractor overhaul facility in Miami
where they were essentially “zero-timed” through extensive overhaul and renovation
activities. Skins were removed from frames and stringers; corrosion was repaired or treated,
engines and propellers were overhauled, landing gear was removed and overhauled,
the entire electrical system was gutted and replaced, wings were rebuilt, control surfaces
were recovered, the nose cone was deleted and replaced with a radome,
and the aircraft given a new coat of camouflage paint.
In preparation for the upcoming trans-Pacific ferry flight,
two temporary 500 gallon ferry tanks were installed with appropriate venting,
servicing and fuel routing plumbing.
These were located along the right side of the fuselage
in the main cabin just aft of the cockpit bulkhead.
In addition to the basic total refurbishment, the cockpit systems were
extensively modified in preparation for their special mission equipment
for Project Phyllis Ann.
The antiquated and unreliable vacuum-hydraulic auto-pilot was removed and deleted.
In its place in the center instrument panel, a monochrome
Bendix weather-avoidance radar was added.
Secondly, all of the vacuum driven gyro instruments were removed and
replaced with AC electrical gyro instruments.
A duplicate set of primary instruments was installed in the co-pilot position.
The original gyro-horizons were replaced with units in both left and right panels
that were the same or similar to the gyro-horizon found in the T-33 jet trainer.
The original vacuum directional gyro (DG) in the pilot’s panel
was replaced with a six-inch diameter magnetic heading instrument,
reference gyro and fluxgate magnetic reference system adopted from the
B-52 bomber. (I believe it was identified as a C-12 Compass System).
The aircraft was also equipped with a Doppler Navigation System (DNS),
a Loran-C navigation system and computer, plus a gyro-stabilized optical
drift meter at the Nav station (similar to a simple bomb sight cross-hairs).
The drift meter would allow the navigator to optically verify when we passed directly
over a ground map reference and thus could periodically update the Doppler position
error in order to maintain absolute accuracy in our ground mapping location.
Also included were upgraded UHF, VHF, FM and HF radio transceivers as well as dual
needle RMI indicators that were linked to the back-end mission equipment,
as-well-as an advanced intercom system that permitted hot-mike inter-cockpit communications
(a luxury almost never seen on the DC-3/C-47)
and an isolated intercom system for the back-end operator crew members.
Electrical power was provided by main and alternate AC converters
located in the tail lavatory. These converters were basically 12 volt
DC powered motors that drove 120 volt AC single-phase alternators.

[As a note of technical interest, the design engineers equipped the
aircraft with a Loran-C system which never became operational because,
in the haste of the project development, they failed to recognize that
the Loran-C system selected was designed for aircraft with 115 volt AC
three phase power, but the installed AC converters could supply only
single phase power.]
After the aircraft refurbishment was completed
— at a refurbishment contract cost averaging $1 million per aircraft —
the aircraft were then flown to the Sanders Electronics facility at Lanier Field
in New Hampshire where the Phyllis Ann mission equipment was installed,
flight tested and calibrated before the aircraft was released for ferry to Vietnam.
This mission equipment included several operator consoles and
a navigator station located in the aft passenger cabin, along with some
sophisticated radio receivers and inflight recorders. Also included was
a series of whip antennas that were mounted in a phased array pattern
above and below the wings and forward fuselage of the aircraft.
With this (sophisticated for its time) antenna system, the aircraft could
take highly accurate bearings to any selected radio frequency, allowing
the aircrew to fly an orbit around an enemy transmitter and triangulate
its location, all the while other crewmembers were identifying,
listening-to, decoding and recording the enemy message traffic.
With the sophisticated navigational equipment of the EC-47 Phyllis Ann
aircraft, we could be constantly aware of our exact position over the
ground (within the accuracy of the current state-of-the-art maps) and
our navigator could then translate the triangulation plots from the
mission equipment into an enemy transmitter site location within a few
meters of accuracy.