TEST PILOT EVALUATION OF THE ANGEL

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP89B00487R000300460003-0
• Release Decision: RIPPUB
• Original Classification: T
• Document Page Count: 8
• Document Creation Date: December 22, 2016
• Document Release Date: August 9, 2011
• Sequence Number: 3
• Publication Date: November 14, 1955
• Content Type: REPORT

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Ile MOWN N1191M 11.11 hi*IiA alseHnh the natloaat defense of the United States
within 40 MMnial of the espenage laws, Title 19, ti:C, Secs. 798 and 794, the transmissimr TN #
or .evelation et which in any manner to an Brie;9raorirec. g:ers?a! is piAbi:ee by law.
111 November 1955
a. Objective: The purpose of these tests is to evaluate subject
airplane?for flight safety deficiencies and to recommend changes to increase
the potential of the airplane with the present and proposed articles.
b. Authority: The authority for these tests was given by the
Chief of Stan. f, HQ, USAF.
c. History: Four flights were made byl
on 8 and 9 _November 1955 consisting of 5+140 hours flying time. The first
two flights were made in #3113 (third article) at a gross weight of 15,725
lbs. at a C.G. of 27% MAC with 735 gal. of fuel. The third flight was
in #3113 also, at a gross weight of 1.11,L50 lbs. with only 535 gal. of fuel.
C.G. was also 27%. The fourth flight was made in #3111 (first article) at
a gross weight of 14,1125 lbs. with 535 gal. of fuel. C.G. for the fourth
flight was 25.6%.
The first flight was to check low speed and low altitude
(115,000 ft. max.) characteristics. Several touch and go landings were
made and general flight control tests were made. The second and third
flights were to maximum altitude (70,300 ft. was highest made) to check
flight characteristics at high altitude and high speed. The fourth
flight was in #311l which had been painted, stabilize/ angle of incidence
changed and modified fuel control. Maximum altitude obtained was 66,000-
at which time tbrWtCY5._nqt da resulting in aborting any further
attempts to climb higher.
d. Description of Test Aircraft:
(1) "The Angel" is designed only to fly at extreme altitudes
at low Mach No. (.8) and low indicated speed (260 kts. max.). Primary
mission is high altitude reconnaissance or "Ferret" type missions.
(2) The airplane consists of a single high wing, bicycle type
landing gear with two droppable wing ",Pogo" gears used only for the take-off
roll. The engine installed is a J-57/P 37 turbojet rated at 10500 thrust.
A unique feature incorporated which is not used in other military airplanes
is the "gust control". This control raises the flaps and ailerons to
relieve gust loading and will permit higher indicated speeds during turbu-
lent conditions.
(3) The single place cockpit is simple and straightforward with
little to complain about as pertains to arrangement of controls, switches,
instruments, etc.
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(14) The high altitude capability dictates a high aspect ratio
type design which this airplane has. The aspect ratio is 10.67.
Empty gross weight is 11,000 with a maximum take-off gross weight of
17,500 carrying 935 gallons of fuel. A maximum overload gross may be
used of 20,000 by carrying 1,335 gallons of fuel.
2. DISCUSSION OF RESULTS
a. Taxiing: The airplane is not taxied prior to take-off but is
towed to take-off position. After landing, the airplane may be taxied
if unrestricted area is available but airspeed should be kept at 1,0-50
kts. to maintain aileron control to prevent excessive wing tip drag.
Also, flaps should be retracted for taxiing as flaps greatly reduce
aileron effectiveness. The airplane cannot be turned around on a
runway because of the large turning radius required. The tail wheel
is steerable with the rudder pedals 6? either side of center.
b. Take-off and Climb: The take-off is quite simple and easily
performed. The airplane accelerates rapidly and is airborne before the
pilot realizes it. Until the pilot has become proficient in the take-off
characteristics some difficulty may be experienced during crosswind
conditions. The tail wheel steering and r..udd,er... ec-ness is very
Inlet. However, because of the short take-0, 1-and rapid acceleration,
crosswind take-offs are considered feasibl ac ter pilot has gained
experience. Proper technique for take-off is as follows. Run power up
to 65% and release brakes. After brake release, advance power to 85%.
As pilot experience is gained, full power take-offs may be made. At
50-60 kts. release "pogo" wing gear and at the same time gently ease
back on the control wheel. Airplane will become airborne between
70-80 kts. (depending upon gross weight) and immediately after becoming
airborne raise landing gear. Nose must be pulled up sharply to prevent
exceeding gear retraction speed of 130 kts. After gear is up and locked,
increase climb speed to 160 kts. The climb attitude to approximately
15,000 feet is quite steep and pilot is more or less "hanging on".
Visibility during this part of the climb is v'i rt, ~a_ l _, ni l ._beca7aa._of the
exaggerated nose-up climb angle, and the pilot generally refers to his
flight instruments to maintain attitude. After 15,000 feet the angle
of climb is less and pilot then has time to orient himself and start
mission planning. Climb speed of 160 should be held to an altitude
of 50,000 feet. At this altitude speed should be reduced to 150 kts. until
the Mach limit needle reaches 160 kts. At this time the climb speed
should be held 10 kts. under the Mach limit needle for the remainder of
the mission. Climb cruise condition will start at approximately
65,000 feet. Approximate time to climb from brake release is as follows.
Take-off attitude was approximately 14,000.
35,000
6 min.
55,000
12 min.
h0,000
7 min.
60,000
15 min.
145,000
8.5 min.
65,000
20 min.
50,000
10 min.
70,000
27 min.
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These climbs were at fairly light gross weights and should not be
construed as accurate for a profile mission. Also they were timed by
stop watch and not reduced to standard day conditions.
c. Cruise and Maneuvering Flight:
(1) Inasmuch as this airplane is very restricted, the cruise
and maneuvering flight envelope is small. For safety purposes the
following limitations are imposed.
Heavy weights
Light weights
Clean-smooth air
Clean-rough air
Gust control on smooth air
Gust control on rough air
Flaps down
Gear extension
Gear retraction
2.5 "g"
3.5 "g"
220 kts. or .8 Mach
150 kts. or .8 Mach
260 kts. or .8 Mach
220 kts. or .8 Mach
130 kts.
200 kts.
130 kts.
Cruise at high altitude (70,000) is fairly simple. Caution must be
exercised to prevent exceeding limit Mach No. but other than that the
airplane handles well. At altitude above 60,000 the pilot must use the
throttle vernier to manipulate power as fine adjustments are necessary
to prevent exceeding limit temperature and engine speed. The pilot must
use the pressure ratio gauge and exhaust temperature gauge to monitor
proper power. Also, again it should be noted that the speed must be
kept to 10 kts. under Mach limit as thrust and temperature will vary
with airspeed. Also, for interest, it should be noted that a 10 kt.
change in speed at high altitude results in a 110 kt. true speed loss.
Also at 70,000, when flying into the sun, the heat,_upon,_ Ile c very.,_u .ooortab .e. Curtains should be -provided for sun shades.
Cockpit temperature is adequate except when letting down, little
Imat_is provided because of low engine rpm. P.ia..ots may desire slowing
rate of descent at lower altitudes (110,000 and. below) by adding power
tQ_provide heat. In #3113 the oil.. and smoke expelled through the air-
is tem unacceptable. The filter installed in #311
eliminates the oil and smoke and should be installed in all airplanes.
Bank angles of 600 were made at 70,000 feet with no adverse character-
istics being encountered. Level flight turns may be made at approxi-
mately 20? bank angles with altitude loss increasing at bank angle
above 20?. At 60? bank angle rate of descent is approximately 1000 feet
per minute.
(2) The static stability, both stick free and stick fixed,
is positive about all three axes. Dynamic longitudinal stabilizer
is dead beat as is the lateral. The dihedral effect is non-existent..--
Dynamic directional does not fall within 1815 B spec. requirements;
however, the directional oscillation is of low frequency and is easily
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controllable with rudder. Also the moderate amount of adverse_,yaw
encountered is readily con _g_1,i.ed with rudder.
(3) Both elevator and rudder control forces are satisfactory.
Stick force per "g" is also acceptable; however, the aileron forces are,
atrocious. This is noticed immediately after take-off and the force
increases with speed. This condition causes pilot fatigue and it is
recommended that the aileron forces be greatly reduced if practicable.
(1a) During cruising flight airplane response to elevator and
aileron control is immediate and the controls are effective. Response
to rudder is slow and rudder effectivenessis notacceDtablg. However,
because of the non-existent dihedral effect and symmetrical flight
conditions, the rudder is very seldom used. Rate of roll is low and
dgcreasgs with speed increase. It is acceptable for the purpose for
which this airplane was designed, however*
d. High Speed Flight:
(1) Airplane #30 (3rd article). This airplane was flown to
260 kts. indicated and .8 Mach No. No adverse condition was noted at
the high "q" limit. Stick force per "g" is high and the rate of roll
is approximately 200 per second which is desirable, considering the
design limits and construction. At .8 Mach No, there is a light
aileron nibble followed by a slight nose-down pitching movement.
The pitching movement is controllable and it is felt that there is
plenty of warning to prevent exceeding limit Mach No. if caution is
properly exercised. It is recommended that a slight nose-up trim be
used at extreme altitudes requiring a slight push force on the wheel
on the part of the pilot to prevent inadvertently exceeding limit
Mach No. It would be desirable to have an automatic pilot on the
longitudinal control to relieve pilot concentration and permit him to
attend to other duties without concerning himself about maintaining
proper airspeed or worry about exceeding limit Mach No.
(2) Airplane #3141 (modified 1st article). Because of the
paint or the stabilizer modification of this airplane, or both, this
airplane felt better generally during all flight maneuvers. At high "q"
flight (260 kts.) less forward elevator is required and results in
less pilot effort when flying at these speeds. When checking the
high Mach No, characteristics, however, it was quite startling to find
that a high frequency, moderate.a t de,. rudder buffet peel red at
,82_ Maeh,_,No ,th o ~?arr , whatsoever. This had not been experienced
before by the contractor; thus any further testing was terminated until
engineering analysis could be made. The lack of any warning is not
considered ,acceptable and, the undersigned would prefer to, fly the
umodified..plane wkia.ch..has a defiz ite Mach limit warning.
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(3) It is recommended that descents from high altitude be
made as follows. Extend gear and dive brakes. By using throttle
vernier reduce thrust to pressure ratio reading recommended by
contractor. Power reduction is continued in this manner until reaching
50 000 at which time power may be reduced to idle. Put airplane-in
606 bank and hold speed 10 kts. below limit Mach. More caution is
needed during descents as dive brake buffet will tend to mask the Mach
b t. It takes a roximate 8 minutes to reach 50,0 1 00 f
y
uffeM pp ],y from 70,,000
feet. Divebrake effectiveness is.,,verlowand. should_be increased
by 200% or more. This is considered one of the main deficiencies of
the airplane.
e. Trim Controls and Trim Changes: The aileron and elevator have
electrical trim tabs actuated by switches. The rudder trim consists
only of a metal tab adjusted from the outside. The elevator switch is
on the right side of the wheel while the aileron switch is on the left
console. TYe eron switch should be incorporated with the elevator
43diterh,7-sw,tc Both aileron,
and elevator.. trim speeds are
f tQQ slow._and . s1io .d e, ...a ucr..eased at, least by 1QQ%. This is especially
true of the elevator. There is very little trim change with either gear
actuation or thrust changes. There is a nose-up trim change when
extending the dive brakes above 150 kts. that increases slightly with
speed increase but easily controllable with elevator. Very little trim
change is noticed when using dive brakes below 150 kts. There is a
fairly heavy tchange_When actuating,, the, gust contrgls ar the pilot
must concentrate to maintain same attitude when actuating the gust
control. The extension of gust control causes a nose-up pitching
movement and vice versa upon retraction. When extending the landing
flaps there is a nose-down trim change that also requires pilot attention
to maintain attitude. These trims changes are rapid enough that elevator
Il;? speed cannot keep up, thus the requirement for increased elevator trim
speed. Trim changes, in all cases, are in the proper direction and are
considered acceptable,
f. Stalls and Low Speed Handling:
(1) Accelerated stalls are mild and straightforward. There
is an airframe buffet approximately 5 kts. above stall and a nose-down
pitching movement at the stall. Stall recovery is easily made by
releasing back pressure on control wheel.
(2) Clean unaccelerated stalls are considered mild and stall
warning is evidenced by a slight airframe buffet approximately 5 kts,
above stall. Stall warning starts at approximately 83 kts. with
airplane stalling at 77 kts. There is a yawing oscillation of approxi-
mately_ 5? during the all that cannot he readily controlled by the
rudder. At the same time there is a slight lateral oscillation that
is controllable with ailerons.
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(3) As flaps are extended both stall warning and stall speed
is reduced approximately 2 kts. for every 100 of flap. A maximum of
30? of flaps is available. At the stall with 300 of flaps there is a
sudden right wing drop with a right yawing movement. Neither,of these
characteristics are controllable and the stalling characteristics or
lack ,._ of warning is not considered acceptable. Stall speed with flaps
is approximately 71 kts.
g. Approach and Landing: The approach and landing of this airplane
is the----most difficult maneuver of any to perform. The airplane is quite
difficult and unwilling to slow down to the proper approach speed of
90-100 kts. Flaps aid in reducing speed; however, the flaps reduce
aileron effectiveness approximately 7OO,.and increase aileron force
apAroximatel10. With the high aileron forces and low aileron effec-
tiveness, the pilot is quite unwilling to use flaps especially during
turbulent air and crosswind conditions. The base leg must be flown
low (200-300 ft.) and over the fence altitude is approximately 10-20 feet.
Because of the thrust being produced at idle power combined with low
airplane drag, it isvirtually impossible to "spot" a landing. Also
ground effect very definitely will cause the airplane to float
considerably. Because of the B-1.7 type arrangement of the gear, a
two-point or rear wheel landing must be made to prevent porpoising which
could become dangerous if the pilot overcontrols or bounces too high
after permitting the front truck to hit first. Further, because of
the low rudder effectiveness difficulty will be encountered, when
attempting crosswind landings, in maintaining runway alignment. As the
airplane must virtually be stalled to land, the heretofore mentioned
stalling characteristics are not compatible with airplane longevity.
Thus the requirement for a drag chute or increased dive brake effective-
ness is again necessary to shorten floating and landing distance after
touchdown. The low rudder and tail wheel steering effectiveness
dictates a requirement for nose wheel steering in order that pilots
-_man_Lan_,drect .onal, control.
The recommended landing and approach procedures are as
follows: Enter initial overhead pattern 700 feet above runway at
approximately 130 kts. Turn onto base leg at 200-300 feet and lower
10% flaps. Turn on the final 1-2 miles from end of runway at 200 feet.
Adjust power to permit descent at 85-90 kts. If wind conditions permit
extend 300 of flaps one mile from end of runway. Cross end of runway
at 80 kts., 2-3 feet high and reduce power to idle if not having already
done so. Attempt to hold airplane 1-2 feet off runway until it stalls and
lands at which time place power lever to idle cut off. If flaps are
used, retract as soon as possible to realize more aileron effectiveness
for lateral control. Use moderate to heavy wheel braking after airspeed
reaches to kts. still attempting to maintain wing level attitude with
ailerons. Dive brakes should be used throughout the approach and
landing for what little drag they offer. It will be noticed that the
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ground effect reduces stalling speed approximately 5-10 kts.; however,
caution must be exercised in that the airplane will stall at a higher
speed if levelled off out of ground effect. With an adequate drag
device it is felt that flaps would not be used thus increasing the
aileron effectiveness and also realizing the better clear stalling
characteristics. Further an adequate drag device would permit steeper
approach angles, and possibly higher touchdown speeds with much shorter
ground roll. As Uilot experience is gained the. engine may be cut on
_re uce._ .t e_ 1Q .. 1Q. t ing . di stance.
3. CONCLUSIONS
It is concluded that the number 3 article (#3L3) or any other
article employing the same fuel control schedule employed by #343, could
perform the basic mission. Further, it is concluded that this airplane
could not be adapted to the role of an interceptor because of its
lim'ng Mach No, and maneuvering flight restrictions.
)4. RECOMMENDATIONS
The first two recommendations are considered mandatory before
releasing any of these airplanes to conduct missions,
a. It is recommended that:
(1) A much greater effective drag device be installed to
decrease the letdown time from altitude and to permit steeper approach
angles and shorter landing distances. This device will also delete
the need of landing flaps.
steering.
(2) Nose wheel steering be installed replacing the tail wheel
b. The following recommendations should be made as soon as possible
without delaying the program:
(1) A Mach No. limit warning device be installed. This is
especially necessary if the modifications made on #3111 are to be
incorporated on subsequent airplanes.
(2) Provide adequate stall warning in the approach configuration
and improve the stalling characteristics.
(3) Install auto pilot so pilot may devote time to other duties.
(4) Install sun shades.
(5) Install filters in airconditioning system to prevent
oil and smoke from entering cockpit.
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(6) Reduce aileron forces by 200%.
(7) Ihcrease elevator trim speed by 100%.
(8) Increase aileron trim speed 50%.
(9) Incorporate aileron trim switch with elevator switch
as a single four-way switch.
(10) Increase rudder effectiveness for take-off and landing
under crosswind conditions.
(11) Exchange the present oil pressure and temperature gauges
with the instrument light and instrument panel lights for more ease
of readability.
(12) Provide cover for periscope when not in use.
(13) Reduce the flap and dive brake buffet by 100%.
(1)4) Add mike button to left side of control wheel or relocate
from throttle to left side of control wheel.
(15) Provide a better cover for the aft fuel tank empty
warning light.
(16) Mark 150 kts. clean limit speed on airspeed indicator.
(17) Install large type sensitive "g" meter in place of small
standard "g" meter.
(18) Improve automatic operation of heat control so pilot
will not have to divert attention fr an other duties to continually
operate heat control manually.
(19) Provide a more sensitive and accurate pressure ratio
Prepared bb
Chief, Flight Test
rations Division
Maj. Gen., USAF
Chief, Weapons Test
Evaluation Division
ARDC
IS 1)260
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