AIAA UFO Subcommittee — "UFO Encounter I" (the 1957 RB-47 case), Astronautics & Aeronautics, July 1971

Source: Astronautics & Aeronautics (AIAA), vol. 9 no. 7 (July 1971), pp. 66-71 — "UFO Encounter I: Sample Case Selected by the UFO Subcommittee of the AIAA," the July 17, 1957 RB-47 case (championed by atmospheric physicist James E. McDonald, on whose archived papers this scan resides). This is the PDF cited in the r/UFOs Grusch-NYC thread as the source of the "2.995-3 GHz" UAP-frequency figures.
URL: http://kirkmcd.princeton.edu/JEMcDonald/mcdonald_aa_9_7_66_71.pdf
Captured: 2026-07-04 via pdftotext (5-page two-column PDF; mechanical extraction, column reading order approximate).
Analysis: ../../sources/mcdonald-atmospheric-physicist

Astronautics & Aeronautics July 1971

UFO ENCOUNTER 1
Sample Case Selected by the UFO
Subcommittee of the AIAA
In its "Appraisal of the UFO Problem" A/A Nov.1970, pp. 4951, the Subcommittee pledged to give the members of this
society an opportunity to form their own opinions with
respect to the type of observations which form the core of
the UFO controversy.
The selected case, which occurred on July 17, 1957, is
treated in the Condon Report (Condon, E. U., 1969,
Scientific Study of Unidentified Flying Objects, Bantam
Books, N.Y., pp.56-58,136-139, 260-266, 750, 877-894).
During the study by the University of Colorado group, the
case files were not located due to an error in date. In
addition, radar and weather analyses were made for
September 19, 1957, rather than July 17, 1957. The
conclusions drawn by members of the Condon Committee,
based on available information are as follows:

If the report is accurate, it describes an unusual,
intriguing, and puzzling phenomenon, which, in the absence
ot additional information, must be listed as unidentified.
(Condon, p.57).
In view of... the fact that additional information on this
incident is not available, no tenable conclusions can be
reached. From a propagation [Based on a wrong date.]
standpoint, this sighting must be tentatively classified as an
unknown. (Thayer, p.139).
If a report of this incident, written either by the B-47

Air Force Observations
of an Unidentified Object
in the South-Central U.S.,
July 17,1957
Summary
An Air Force RB-47, equipped with
electronic countermeasures (ECM)
gear and manned by six officers, was
followed by an unidentified object for a
distance of well over 700 mi. and for a
time period of 1.5 hr., as it flew from
Mississippi, through Louisiana and
Texas and into Oklahoma. The object
was, at various times, seen visually by
the cockpit crew as an intensely
luminous light, followed by groundradar and detected on ECM monitoring
gear aboard the RB-47. Of special
interest in this case are several instances
of simultaneous appearances and
disappearances on all three of those
physically distinct "channels," and

crew or by Wing Intelligence personnel, was submitted in
1957, it apparently is no longer in existence. Moving pictures
of radar scope displays and other data said to have been
recorded during the incident apparently never existed.
Evaluation of the experience must, therefore, rest entirely
on the recollection of crew members ten years after the
event. These descriptions are not adequate to allow
identification of the phenomenon encountered. (Craig,
p.265).
4. After review the unanimous conclusion was that the
object was not a plasma or an electrical luminosity by the
atmosphere. (Altschuler, p.750).
Subsequently, James McDonald has been able to locate
the case files, to correct the date of the flight and to draw
additional information from the files as well as from personal
interviews with the crew. At the request of the UFO
Subcommittee, he describes the case in the following
article. It is left to the reader to draw his own conclusions.
The aircraft Commander, Lt. Colonel Lewis D. Chase,
USAF (Ret.), has confirmed the accuracy of this report in a
letter to the Subcommittee.
This sample case may serve to illuminate the difficulties
in deciding whether or not the UFO problem presents a
scientific problem.

rapidity of maneuvers beyond the prior
experience of the aircrew.
Introduction
In the early morning hours of July 17,
1957, an RB-47 was flying out of
Forbes Air Force Base, Topeka,
Kansas, on a composite mission that
included gunnery exercises over the
Texas-Gulf area, navigation exercises
over the open Gulf, and finally ECM
exercises scheduled for the return trip
across the south-central United States.
The RB-47 was carrying a six-man
crew, of whom three were electronic
warfare officers manning ECM gear in
the aft portion of the aircraft. Their
names are as follows: Lewis D. Chase,
pilot; James H. McCoid, co-pilot;
Thomas H. Hanley, navigator; John J.
Provenzano, No.1 monitor; Frank B.
McClure, No.2 monitor; Walter A.
Tuchscherer, No.3 monitor.
I shall draw upon my interview with the
crew as well as case files which I finally
located. The files consist of a three-

page TWX filed from the 745th
ACWRON, Duncanville, Texas, at
1557Z on July 17, 1957, and a fourpage case summary prepared by E. T.
Piwetz, Wing Intelligence Officer, 55th
Reconnaissance Wing, Forbes AFB,
and transmitted to ADC Hq., Ent AFB,
Colorado, in compliance with a request
of August 15, from Col. F. T. Jeep,
Director of Intelligence, ADC. That
summary, plus a 12-page Airborne
Observer's Data Sheet, was forwarded
on November 17 from ADC to Blue
Book, and was evidently the first
notification Project Blue Book received
concerning this case.
The 12-page Data Sheet (AISOP #2)
was prepared by Major Chase on
September 10, and contains a number
of points of relevance not covered in
other parts of the case file.
There is very relevant information in
the case file as to precise times,
locations, and other circumstances,
and the case file does have the great

Astronautics & Aeronautics

virtue of representing a summary
account prepared while all of the
details were fresh in the minds of the
crew.
Before describing the first ECM
contact, it is necessary to explain
briefly the nature of the ECM gear
involved in this case. (Details are no
longer classified, although all of the
basic case-file documents were
initially SECRET.) This RB-47 had
three passive direction-finding (DF)
radar-monitors for use in securing
coordinate information and pulse
characteristics on enemy groundbased radar. The #2 monitor, manned
by McClure, was an ALA-6 DFreceiver with back-to-back antennas
in a housing on the belly of the RB-47
near the tail spun at 150 or 300 rpm as
it scanned an azimuth. (Note that this
implies ability to scan at 10/sec past a
fixed ground radar in the distance.)
It's frequency range was 1000-7500
MHz. Inside the aircraft, the signals
from the ALA-6 were processed in an
APR-9 radar receiver and an ALA-5
pulse-analyzer. All subsequent
references to the #2 monitor imply
that system.
Number I Monitor
The #1 monitor, manned by
Provenzano, was an APD-4 DF
system, with a pair of antennas
permanently mounted on either wing
tip. It was working at a higher
frequency. The #3 monitor, with a
frequency range from 30-1000 MHz,
was manned by Tuchscherer. It was
not affected and will not be described
here. VHF communications were
likewise not affected.
For emphasis, it needs to be
stressed that the DF receivers are not
radars and do not emit a signal for
reflection off a distant target. They
only listen passively to incoming
radar signals and analyze signatures
and other characteristics. When
receiving a distant radar set's signal,
the scope displays a pip or strobe at an
azimuthal position corresponding to
the relative bearing in the aircraft
coordinate system. For the case of a
fixed ground radar, approached from
one side, the strobe is initially seen in
the upper part of the scope and moves
down-scope, a point to be carefully
noted in interpreting the following
discussion.
Having completed the
navigational exercises over the Gulf,
Chase headed across the Mississippi
coastline, flying at an altitude of
34,500 ft, at about Mach 0.75 (258 kt
IAS=500 mph TAS). The weather
was perfect and practically cloudless
July 1971

under the influence of a large highpressure area extending throughout
the troposphere. There were no
showers or thunderstorms anywhere
along the flight route. Shortly after
the coast near Gulfport was crossed at
a point marked A on the map in page
68, McClure detected on the #2
monitor a signal painting at their 5
o'clock position (aft of the starboard
beam). It looked to him as if he were
receiving a legitimate ground-radar
signal. Upon noting that the strobe
was moving up-scope, McClure
tentatively decided that it must be a
ground radar off to their northwest
painting with 180 deg ambiguity for
some electronic reason. But when the
strobe, after sweeping up-scope on
the starboard side, crossed the flight
path of the RB-47 and proceeded to
move down-scope on the port side
McClure said he gave up the
hypothesis of 180 deg ambiguity as
incapable of explaining such
behavior.
Fortunately, he had examined the
signal characteristics on his ALA-5
pulse-analyzer, before the signal left
his scope on the port side aft. In
discussing it with me, his recollection
was that the frequency was near 2800
mcs, and he recalled that what was
particularly odd was that it had a
pulse-width and pulse repetition
frequency (PRF) much like that of a
typical S-band, ground-based, search
radar. He even recalled that there was
a simulated scan rate that was normal.
Perhaps because of the strong
similarities to ground-based sets such
as the CPS-6B, widely used at that
time, McClure did not, at that
juncture, call this signal to the
attention of anyone else in the
aircraft. The #1 monitor was not
working the frequency in question, it
later developed. The #3 monitor was
incapable of working the frequency
in question, McClure and the others
indicated to me.
I next quote information transcribed
from the summary report prepared by
the Wing Intelligence Officer,
COMSTRATRECONWG 55, Forbes
Air Force Base, concerning this part
of the incident that involved this
aircraft (call sign "Lacy 17"):
ECM reconnaissance operator #2
of Lacy 17, RB-47H aircraft, intercepted at approximately Meridian,
Mississippi, a signal with the
following characteristics: frequency
2995 mc to 3000 mc; pulse width of
2.0 microseconds; pulse repetition
frequency of 600 cps; sweep rate of
4 rpm; vertical polarity. Signal
moved rapidly up the D/F scope

indicating a rapidly moving signal
source; i.e., an airborne source.
Signal was abandoned after
observation...

Initial Visual Contact
If nothing further had occurred on
that flight to suggest that some
unusual object was in the vicinity of
the RB-47, McClure's observations
undoubtedly would have gone
unmentioned and would have been
quickly forgotten even by him. He
was puzzled, but at that point still
inclined to think that it was some
electronic difficulty.
The flight plan called for a turn to the
west in the vicinity of Meridian and
Jackson, Mississippi (Point B), with
subsequent planned exercises
wherein the EWOs did simulated
ECM runs against known ground
radar units. The contemporary
records confirm what Chase and
McCoid described to me far more
vividly and in more detail concerning
the unusual events that soon ensued.
They turned into a true heading of
265 deg, still at Mach 0.75 at 34,500
ft. At 1010Z (0410 CST), Major
Chase, in the forward seat, spotted
what he first thought were the landing
lights of another jet coming in fast
from near his 11 o'clock position at, or
perhaps a bit above, the RB-47's
altitude. He called McCoid's
attention to it, noted absence of any
navigational lights, and as the single
intense bluish-white light continued
to close rapidly, he used the intercom
to alert the rest of the crew to be ready
for sudden evasive maneuvers.
But before he could attempt
evasion, he and McCoid saw the
brilliant light almost instantaneously
change direction and flash across
their flight path from port to starboard
at an angular velocity that Chase told
me he had never seen matched in all
of his 20 years of flying, before or
after that incident. The luminous
source had moved with great rapidity
from their 11 o'clock to about their 2
o'clock position and then blinked out.
The Airborne Observer's Data
Sheet filled out by Chase as part of the
post-interrogation gives the RB-47
position at the time of that 1010Z first
visual contact as 32-00N, 91-28W,
which puts it near Winnsboro in eastcentral Louisiana (Point C).
The descriptions obtained in the
1969 interviews with these officers
are closely supported by the original
intelligence report:
67

MAP OF THE
JULY 17, 1957,
UFO EPISODE

FORBES AFB
H

OKLAHOMA
CITY

WELLS
MINERAL
EL PASO
SALT FLATS

G
0540 C

DALLAS

JACKSON
MERIDIAN

0410 C

FT. WORTH

D
A

100

200

300
MILES

GULFPORT

400

500

KEY
PATH OF RB-47H DURING PERIOD OF CONTACT WITH UFO

OTHER PORTIONS OF RB-47H FLIGHT

A--FIRST ECM CONTACT OVER GULFPORT AREA
E--AREA NEAR WHICH AIRCRAFT OVERSHOOTS UFO
B--RB-47H TURNS TO WEST NEAR MERIDIAN
F--OBJECT APPEARS TO RAPIDLY DROP 5000 FT.,
C--FIRST VISUAL SIGHTING BY COCKPIT CREW
THEN BLINKS OUT AS RB-47H ATTEMPTS TO DIVE ON IT
D--RB-47H TURNS NORTHWESTWARD TO PURSUE
G--LAST ECM CONTACT NEAR OKLAHOMA CITY, 1.5 HR
AT FULL POWER
AFTER FIRST VISUAL CONTACT
H--RB-47H LANDS AT HOME BASE

At 1010Z aircraft cmdr first
observed a very intense white light
with light blue tint at 11 o'clock from
his aircraft, crossing in front to about
2:30 o'clock position, co-pilot also
observed passage of light to 2:30
o'clock where it apparently
disappeared.
Chase did not observe any
magnetic compass anomalies during
the flight.
Actions over Louisiana-Texas Area
Immediately after the luminous
source blinked out, Chase and
McCoid began talking about it on the
interphone, with the already alerted
crew listening in. McClure, recalling
the unusual signal he had received on
his ALA-6 back near Gulfport, now
mentioned for the first time that
peculiar incident and concurrently set
his #2 monitor to scan at about 3000
mcs, to see what might show up.
He found he was getting a strong
3000 mcs signal from about their 2
o'clock position, just the relative
bearing at which the unknown
luminous source had blinked out
moments earlier.
68

P rovenzano told me that
immediately after that they checked
out the #2 monitor on other known
ground-radar stations, to be sure that
it was not malfunctioning; it appeared
to be in perfect working order.
H e then tuned his own #1 monitor
to 3000 mcs and also got a signal from
the same bearing. There remained, of
course, the possibility that, just by
chance, this signal was from a real
radar down on the ground and off in
that relative direction. But as the
minutes went by and the RB-47
continued westward at about 500
mph, the relative bearing of the 3000
mcs source out in the dark did not
move down-scope on the monitors as
should have occurred with any
ground radar, but instead kept up with
the RB-47, holding a fixed relative
bearing.
I found these and ensuing portions
of the entire episode still vivid in the
minds of all the men, although their
recollections for various details
varied somewhat, depending on the
particular activities in which they
were then engaged.
Chase varied speed, going to
maximum allowed power, but

nothing seemed to change the relative
bearing of the 3000-mcs source. They
crossed Louisiana and headed into
eastern Texas, with the object still
maintaining station with them.
Eventually they got into the radarcoverage area of the 745th
ACWRON, Duncanville, Texas,
and Chase dropped his earlier
reluctance about calling attention to
these peculiar matters and contacted
that station (code name “Utah”). The
crew was becoming uneasy about the
incident by this time, several of them
remarked to me. That phase of the
incident is tersely described in the
following quotes from the report of
the Wing Intelligence Officer:
Aircraft comdr notified crew and
ECM operator Nr 2 searched for
signal described above, found same
approximately 1030Z at a relative
bearing of 070 degrees; 1035Z,
relative bearing of 068 degrees;
1038Z, relative bearing 040 degrees.
Note that the above time would
indicate that McClure did not
immediately think of making his
ALA-6 check, but rather that some 20
min went by before that was thought
of. Note also that by 1038Z the
Astronautics & Aeronautics

THE UFO SUBCOMMITTEE OF THE AIAA
Chairman
JOACHIM P. KUETTNER
Environmental Research Laboratories of the
National Oceanic and Atmospheric Administration
Boulder, Colorado
Members
JEROLD BIDWELL
Martin-Marietta
Denver, Colorado

MURRAY DRYER
Environmental Research
Laboratories of the National
Oceanic and Atmospheric
Administration
Boulder, Colorado

GLENN A. CATO
TRW Systems
Redondo Beach, California

HOWARD D. EDWARDS
Georgia Institute of Technology
Atlanta, Georgia

BERNARD N. CHARLES
Hughes Aircraft
El Segundo, California

PAUL MacCREADY Jr.
Technical Consulting
Altadena, California

ANDREW J. MASLEY
McDonnell Douglas Missile &
Space Systems
Santa Monica, California
ROBERT RADOS
NASA Goddard Space Flight
Center
Greenbelt, Maryland
DONALD M. SWINGLE
U.S. Army Electronics Command
Fort Monmouth, New Jersey

Secretary
VERNON J. ZURICK
Environmental Research Laboratories of the
National Oceanic and Atmospheric Administration
Boulder, Colorado

unknown source of the 3000 mcs
radar-like signal was moving upscope relative to the 500 mph RB-47.
The Wing Intelligence Officer
continued:
At 1039Z aircraft comdr sighted
huge light which he estimated to be
5000 [ft] below aircraft at about 2
o'clock. Aircraft altitude was 34,500
ft, weather perfectly clear. Although
aircraft comdr could not determine
shape or size of object, he had a
definite impression light emanated
from top of object.
At about 1040Z ECM operator #2
reported he then had two signals at
relative bearings of 040 and 070 deg.
Aircraft comdr and co-pilot saw these
two objects at the same time with
same red color. Aircraft comdr
received permission to ignore flight
plan and pursue object. He notified
ADC site Utah and requested all
assistance possible. At 1042Z ECM
#2 had one object at 020 deg relative
bearing.
In my interviews with the aircrew, I
found differences between the
recollections of the various men as to
some of these points. McCoid
recalled that the luminous source
occasionally moved abruptly from
starboard to port side and back again.
Chase recalled that they had
contacted Utah (his recollection was
that it was Carswell GCI, however)
July 1971

prior to some of the above events and
that Utah was ground-painting the
target during the time it moved upscope and reappeared visually. As
will be seen below, the contemporary
account makes fairly clear that Utah
was not painting the unknown until a
bit later, after it had turned
northwestward and passed between
Dallas and Ft. Worth. Chase
explained to me that he got FAA
clearance to follow it in that offcourse turn (Point D) and indicated
that FAA got all jets out of the way to
permit him to maintain pursuit. The
Intelligence summary continues:
At 1042Z ECM #2 had one object
at 020 deg relative bearing. Aircraft
comdr increased speed to Mach 0.83,
turned to pursue, and object pulled
ahead. At 1042.5Z ECM #2 again
had two signals at relative bearings
of 040 and 070 deg. At 1044Z he had a
single signal at 050 deg relative
bearing. At 1048Z ECM #3 was
recording interphone and command
position conversations.
ADC site requested aircraft to go
IFF Mode III for positive
identification and then requested
position of object. Crew reported
position of object as 10 n. mi.
northwest of Ft. Worth, Texas, and
ADC site Utah immediately
confirmed presence of objects on
their scopes.
At approximately 1050Z object

appeared to stop, and aircraft
overshot. Utah reported they lost
object from scopes at this time, and
ECM #2 also lost signal.
Chase, in reply to my questions,
indicated that it was his recollection
that there was simultaneity between
the moment when he began to sense
that he was getting closure at
approximately the RB-47 speed, and
the moment when Utah indicated that
their target had stopped on their
scopes. He said he veered a bit to
avoid colliding with the object, not
then being sure what its altitude was
relative to the RB-47, and then found
that he was coming over the top of it
as he proceeded to close. At the
instant that it blinked out visually and
disappeared simultaneously from the
#2 monitor and from the radar scopes
at Site Utah, it was at a depression
angle relative to his position of
something like 45 deg.
Chase put the RB-47 into a port
turn in the vicinity of Mineral Wells,
Texas (Point E), and he and McCoid
looked over their shoulders to try to
spot the luminous source again. All of
the men recalled the near
simultaneity with which the object
blinked on again visually, appeared
on the #2 scope, and was again skinpainted by ground radar at Site Utah.
The 1957 report describes these
events as follows:
69

Aircraft began turning, ECM #2
picked up signal at 160 deg relative
bearing, Utah regained scope
contact, and aircraft comdr regained
visual contact. At 1052Z ECM #2 had
signal at 200 deg relative bearing,
moving up his D/F scope. Aircraft
began closing on object until the
estimated range was 5 n. mi. At this
time object appeared to drop to
approximately 15,000 ft altitude, and
aircraft comdr lost visual contact.
Utah also lost object from scopes.
At 1055Z in the area of Mineral
Wells, Texas, crew notified Utah they
must depart for home station because
of fuel supply. Crew queried Utah
whether a CIRVIS Report had been
submitted, and Utah replied the
report had been transmitted. At
1057Z ECM#2 had signal at 300 deg
relative bearing, but Utah had no
scope contact. At 1058Z aircraft
comdr regained visual contact of
object approximately 20 n. mi.
northwest of Ft. Worth, Texas,
estimated altitude 20,000 ft at 2
o'clock from aircraft.
Case added further details on this
portion of the events, stating that he
requested and secured permission
from Utah to dive on the object when
it was at lower altitude. He did not
recall the sudden descent that is
specified in the contemporary
account, and there are a number of
other minor points in the Intelligence
Report that were not recollected by
any of the crew. He told me that when
he dove from 35,000 ft to
approximately 20,000 ft the object
blinked out, disappeared from the
Utah ground-radar scopes, and
disappeared from the #2 monitor, all
at the same time. McClure recalled
that simultaneous disappearance, too.
It should be mentioned that the
occasional appearance of a second
visual and radar-emitting source was
not recalled by any of the officers
when I interviewed them in 1969.
Actions over Texas-Oklahoma Area
McCoid recalled that, at about this
stage of the activities, he was
becoming a bit worried about excess
fuel consumption resulting from use
of maximum allowed power, plus a
marked departure from the initial
flight plan. He advised Chase that
fuel limitations would necessitate a
return to the home base at Forbes
AFB, so they soon headed north from
the Ft. Worth area (Point F).
McClure and Chase recalled that
the ALA-6 system again picked up a
70

3000 mcs signal on their tail, once
they were northbound from Ft.
Worth, but there was some variance in
their recollections as to whether the
ground radar concurrently painted
the object. McCoid was unable to fill
in any of those details. Fortunately
the 1957 Intelligence Report
summarized further events in this part
of the flight, as they moved
northward into Oklahoma:
At 1120Z aircraft took up heading
for home station. This placed area of
object off the tail of aircraft. ECM #2
continued to [get] D/F signal of
object between 180 and 190 deg
relative bearing until I140Z, when
aircraft was approximately abeam
Oklahoma City, Oklahoma. At this
time, signal faded rather abruptly. 55
SRW DOI [55th Strategic
Reconnaissance Wing, Director of
Intelligence] has no doubt the
electronic D/F's coincided exactly
with visual observations by aircraft
comdr numerous times, thus
indicating positively the object being
the signal source.
It was Chase's recollection that the
object was with them only into
southern Oklahoma; Hanley recalled
that it was with them all the way to
Oklahoma City area (Point G); the
others remembered only that it was
there for some indefinite distance on
the northbound leg between Ft. Worth
and Topeka, their home base.
Blue Book
The records indicate that Project
Blue Book received summary
information on this incident from
ADC on Oct.25, 1957 (over two
months after occurrence of the event).
A “Brief Summary” ends with the
following paragraph:
In joint review with the CAA of the
data from the incident, it was
definitely established by the CAA that
object observed in the vicinity of
Dallas and Ft. Worth was an airliner.
This refers to a near-collision of
two DC-6 American Airliners near
Salt Flats, Texas, 50 mi. from El Paso
at 14,000 ft at 3:30 a.m. of this day.
(See the map on page 68.) The case is
now carried in the official Blue Book
files as “Identified as American
Airlines Flight 655.”

MacDonald Dies
On June 13, James E. MacDonald
was found dead in the desert near
Tuscon. He was 51 years old.
Astronautics & Aeronautics