MAINTENANCE AND OPERATIONAL ANALYSIS OF THE MI-4 HELICOPTER

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP80T00246A029700640001-2
• Release Decision: RIPPUB
• Original Classification: S
• Document Page Count: 21
• Document Creation Date: December 22, 2016
• Document Release Date: January 18, 2012
• Sequence Number: 1
• Publication Date: June 27, 1962
• Content Type: REPORT

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1. The purpose of this report is to present a users evaluation of
the maintenance and logistical requirements of this type helicopter
design with particular emphasis on those components, systems and
procedures that reduce these requirements. Support concepts that
increase the tactical capability are also included. In order to conduct
a controlled test, an H-34 helicopter was used for comparative
purposes; therefore, data concerning any aircraft manufacturers
products is factual and is not intended as derogatory.
2. It is not the intent of this publication to provide detailed data
about characteristics or performance of the aircraft discussed, as
these data are the subject of a separate technical report.
3. Line maintenance requirements include daily, periodic and
unscheduled maintenance necessary to maintain flight status of the
aircraft. Data obtained on the H-36 helicopter was under controlled
test conditions without trained maintenance personnel and without
manufacturer support. For this reason, inspections were conducted
more frequently to maintain a close observation of components and
systems. This was accomplished by subjecting the machine to 12. 5,
25, 50 and 100 hour periodic inspections and highly detailed daily
inspections.
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Page
INTRODUCTION
3
TEST HISTORY
5
MANUFACTURING AND DESIGN
7
MAINTENANCE TABLE
8
AVAILABILITY TABLE
9
POL CONSUMPTION TABLE
10
HANDBOOK CONCEPTS
11
SUPPORT PACKAGE CONCEPTS
12
MAJOR DEFICIENCIES
14
ENGINEERING FOR EASE OF MAINTENANCE
15
SPECIAL TOOLS AND EQUIPMENT
17
CONCLUSIONS
18
RECOMMENDATIONS
19
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INTRODUCTION
1. Maintenance data furnished in this report is considered
representative of controlled test conditions. One should not assume
that the same requirements exist for combat or service utilization
since greater utilization would result in reduced maintenance with
exception of dynamic component replacements. The test aircraft
H-36 is a 1954 production model.
2. An uninstrumented H-34A helicopter was used to chase the
test aircraft, to perform logistical and related flights and for a
comparative vehicle.
3. The test objectives were:
a. To determine maintenance requirements.
b. To determine design effects on maintenance in terms of
skills and time required.
c. To evaluate handbook provisions and concepts.
d. To evaluate the support package furnished with the
e. To determine ground support requirements.
4. The following equipment included on other models of this design
was not installed or received with the aircraft:
a. Radio command set, extreme range (classified) and
destruction control system equipment.
b. Parachute jump cable.
c. Ventral container for machine gun and electrical ejection
system equipment.
d. Electrical warning system for machine gun travel.
e. Truss lock bar for clam shell doors when aircraft is
flown with the doors partially open.
3
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f.:" Operational data for special warfare cartridges fired
through the flare system.
g. Flame dampeners for engine exhaust system.
h. Swing-type boom and winch for in-flight rescue of personnel
and equipment.
i. Litters for carrying patients.
j. Pneumatic system for recharging the machine gun.
k. Navigation table.
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TEST HISTORY
1. During the course of test, the engine oil cooler failed in flight
and a forced landing was made. Initial cause of the oil cooler failure
was attributed to failure of the oil cooler flap actuator thermo-sensing
unit. In automatic position, the flaps closed which caused excessive
heating, thereby melting the solder in the oil cooler. Six successive
failures resulted from stress concentrations built-Cup during the repair
process. The aircraft was modified to incorporate a C-124A aircraft
oil cooler designed for the P and W engine. The cooler operated
satisfactorily in this installation. Sixty (60) man-hours were required
to install the new cooler. The C-124 cooler weighed 77 pounds less
than the original.
2. The fuel injection pump was not adjusted properly when the
aircraft was received and adjusting procedures outlined in the manuals
did not prove adequate. Through a reiterative process, the fuel
injection pump was adjusted to an acceptable degree; however, it is
felt that a more desirable setting could be obtained if the necessary
equipment was available. Design of the injection nozzles appears good
since no cylinder barrel lubrication problems occurred. Engine
starting characteristics with the injection system were very good.
3. Difficulty experienced with the main transmission oil pressure
transmitter line was loss of fluid between the transmission diaphram
_and the transmitter. Compass fluid was used and failed. Regular 30W
grade oil was installed and the system operated satisfactorily.
4. During assembly of the tail cone to the fuselage, the original
bolts failed during the torqueing operation. NAS 3007-20 bolts were
obtained and installed as replacement items.
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S. The supercharger actuator motor failed. This was returned
to service with the parts kit furnished with the aircraft.
6. The rotor brake micro switch failed and clutch engagements
could not be accomplished. A like item available in military channels
was installed with only minor modifications.
7. The radio altimeter could not be aligned by radio technicians
since no handbook or schematic coverage was furnished. By process
of elimination, instrument adjustments were accomplished successfully
by adjustment of the vertical and horizontal screws an the back of the
receiver transmitter package. No in-flight adjustments are required
with proper ground adjustments.
8. The main rotor blade mechanical dampers required adjustment
due to temperature differential of fall and winter seasons.
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MANUFACTURING AND DESIGN
1. The fuselage design is comparable to the H-19 helicopter,
modified to incorporate rear loading clam shell doors. The helicopter
has an articulated main rotor which incorporates pitch cone and pitch
flap coupling. The blade attach lugs lead the mast by 60MM. In
addition, mechanical friction type blade dampers are provided. The
horizontal stabilizer is connected to the collective pitch system.
This, with contribution from the C.G. location and mass tilt, provides
a relatively level attitude of the fuselage in forward flight. The
main rotor blades are constructed of a steel tube spar covered with
plywood and fabric. The blades are very flexible; therefore, incorporate
split trailing edge stringers to allow for deformations when the blades
are bending.
2. The engine appears to be similar to the R-2600, except for the
fuel injection system. Failure of the supercharger oil seal ring in the
impeller section revealed that the R-2600 engine utilizes the same seal.
One was procured to return the engine to a serviceable condition.
3. Design specifications for the helicopter were apparently
directed toward simplicity and operational structural reliability.
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MAINTENANCE TABLE
(3 August 1960 - 17 February 1961)
H-36
0/0
H-34
0/0
Daily Maintenance
361:00
41.9
192:05
25.5
Periodic Maintenance
165:00
19.2
462:50
61. 5
Unscheduled Maintenance
335:15
38.9
97:45
13.0
861:15
752:40
Maintenance to Flight
Hour Ratio
5.9
- 1
3.3
- 1
NOTE:
H-36 unscheduled maintenance resulted from engine oil cooler
failures, fuel control adjustments and modification of the oil cooler
system. Daily maintenance man-hours were substantially increased
to assure safe and continuous operations throughout the test; therefore,
would compare favorably with the H-34 under normal operating conditions.
H-34 periodic maintenance resulted from component replacement.
H-36 Flight Time Accumulated During Test (Includes 24 hrs of
ground operation) . . . . . . . . . . . . . . . . . . . . . . . . . 147:40
H-34 Flight Time Accumulated During Test . . . . . . . . . . . 230:20
Maintenance hours were based on time to complete the job. (Includes
procurement of tools, parts, etc. )
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AVAILABILITY TABLE
(3 August 1960 - 17 February 1961)
In Commission
Out of Commission
Month
Days
H-36
H-34
H-36
H-34
Aug
28
23
26
5
2
Sep
30
15
30
*15
0
Oct
31
31
28
0
3
Nov
30
26
28
**4
2
Dec
31
13
31
***18
0
Jan
31
16
25
****15
6
Feb
17
17
17
0
0
198;
141
185
57
13
Percentage 71.2 93.4 28.8 6.6
First engine oil cooler failure including engine teardown and repair.
Second oil cooler failure requiring down time.
Third oil cooler failure requiring down time and modification to
C-124A aircraft oil cooler.
****Down time required to return original instruments to service
ope ration.
NOTE:
H-36 out-of-commission time would be reduced to 16 days if the
oil cooler had not failed.
H-34 out-of-commission time would be reduced to 6 days if dynamic
components had not reached their operating times between overhaul.
The increased availability rate and reduced maintenance to flight
hour ratio is attributed to adequate parts on hand at the test site and
the capability and authority to conduct third and fourth echelon maintenance.
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POL CONSUMPTION TABLE
H-36
Flights . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
Flight Hours (Inc lude.s,24..h s ground.operating time) . . . . 147:40
Fuel Used . . . . . . . . . . . . . . . . . . . . . . . . . . . 9290 Gal
Oil Used (Engine) . . . . . . . . . . . . . . . . . . . . . . . 1395 Qts
Average fuel consumed per hour .. . . . . . . . . . . . . . 62. 9 Gal
Average oil consumed per hour . . . . . . . . . . . . . . . . 9. 4 Qts
Fuel tank capacity . . . . . . . . . . . . . . . . . . . . . . 258 Gal
Oil tank capacity . . . . . . . . . . . . . . . . . . . . . . . 14. 5 Gal
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HANDBOOK CONCEPTS
1. Manuals furnished with the aircraft were as follows:
a. Helicopter Description
b. Operation and Maintenance
c. Engine Description, Operation and Service Instruction
d. Operating and Piloting Instructions
e. Shipping Instructions by Sea
f. Electric Diagrams
Instructions for Computing Range and Endurance
h. Handbook of Device Operating Instructions and Illustrated
Catalogues.
i. l~au~s acturer. Gua~rs~ntee.:Ca.ftifirates
j. Log Books
2. The manuals contain general information only and detailed step
procedures are not included. A research of several manuals is
required when performing other than routine maintenance. From this
standpoint, the manuals are confusing and are considered inferior to
those utilized by the Military Services.
3. The warranty books issued on all components are considered
very desirable as this would require vendors and prime manufacturers
to work together on design applications. The booklets contain general
technical parameters for the equipment and set forth guarantee periods
and conditions for each component. Our manuals do not contain such data.
4. The Flight Operations Manual contains aircraft operational data
for over mountain, sand, snow and water flights, which is very desirable.
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SUPPORT PACKAGE CONCEPTS
1. The support package received with the aircraft (reported to
assure continuous operations in the field for a minimum Of one (1) 1
year) consisted of vendor and prime contractor parts kits and fast-
moving small items. The contents of these kits include high mortality
hard items such as: bolts, nuts, keys, spacers, screws, brushes,
springs, etc. "O" rings and gaskets were furnished in separate
packages. The following spare parts kits were received with the
aircraft:
a. Main Rotor Hub
b. Magneto
c. Swash Plate
d. Radio Tubes (VHF-ADF)
e. Booster Coil
f. Main Wheels
g. Tail Rotor Drive Shaft
h. Hydraulic Filters
i. Starter
j. Voltage Regulator
k. Main Rotor Drive Shaft
1. Hydraulic Pump
m. Main Gearbox
n. Nose Wheels
o. Fuel Injection Pump
p. Solenoid Priming Valve
q. Radio Altimeter
r. Hydraulic Booster
S. Intermediate Gearbox
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t. Electric Actuator
U. Tail Gearbox
v. Electric Motor
w, Main Gearbox Drive Shaft
X. Ignition Switch
y. Slipring Rotor Tip Lights
Z. Supercharger Actuator Motor
2. Two of the spare parts kits were used on the main rotor blade
tip light slipring and the supercharger actuator motor. Both systems
were returned to service. The support package concept is considered
sound and very desirable. This concept is believed to be of paramount
importance under current tactical requirements as delays resulting from
improper provisioning, procurement, lead times and shipping are
obviated.
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MAJOR DEFICIENCIES
1. The engine oil cooler is warranted for operation at 58 psi;
however, is installed in a system that operates at 71 - 90 psi. This is
believed to be a contributing factor in the aforementioned failure.
2. Time required to engage the rotor is excessive. External
preheating is required during winter operations to reduce engagement
time. The oil tank does not contain a hopper and is mounted behind
and above the engine cooling :fan. This is obviously a design deficiency.
Installation of a hopper and relocation of the oil tank would materially
reduce rotor engagement time.
3. Engagement of the rotor is critical above a 10 knot wind due to
main rotor blade flexibility. The internal and external noise level is
quite high and carbon monoxide content is at maximum.
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ENGINEERING FOR EASE OF MAINTENANCE
1. Efficiency of design in relation to maintenance is good in some
areas and poor in others. Examples are: Inspection panels mounted
with straight screws which increase maintenance hours. Although no
dynamic components required replacement, maintenance time would be
considerably higher than the H-34 due to the fact that the engine cowling
panel design requires excessive removal and replacement of sections to
replace the components. Access panels are incorporated for maintenance
of components; however, the engine package is restricted in work area
and increases normal maintenance hours; e. g., a spark plug change
required 16 man-hours. An engine cowling change is considered
equivalent to H-19 type helicopters (approximately 1/2 man-hour).
Replacement of the engine accessory cowling is almost impossible without
damage to the cowling. The engine does not hinge down from the top
for maintenance; however, it is furnished as a complete built-up
assembly for field change.
2. The aircraft is equipped with external systems charge connections.
Provisions of this type are considered desirable for fleet operations by
Department of Navy personnel participating in this program.
3. Dynamic component lubrication provisions are considered
superior in design and reliability when compared to domestic helicopters.
All oscillating and pre-loaded bearings are housed in an oil reservoir.
The main and tail rotor sleeve and spindle assemblies are lubricated with
90W oil. No addition of oil was required for these reservoirs throughout
the test.
4. No seal leakage problems were experienced with the gear boxes
or engine. The main transmission is lubricated with grade 1100 oil and
the intermediate and tail rotor gear boxes are lubricated with 90W oil.
By comparison, seal leakage is a constant problem with the H-34.
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5. Corrosion preventive measures are incorporated on the
fuselage and components.
6. A refueling panel is incorporated and can be used for refueling
from ground reservoirs, drums or can be used to refuel other aircraft.
This is considered a unique system and is believed to have definite
tactical applications.
7. The instrument panel is mounted in two sections on center
hinges which permits each side to be swung out for easy instrument
replacement, maintenance and trouble shooting. This is an extremely
good feature and considered worthy of adaptation.
8. The instrument mounting devices are unique, simple and
logical from a maintenance viewpoint. Wiring harness clamps are
simple and reliable from a maintenance standpoint.
9. The ice detection system appears to be reliable and easy to
maintain.
10. The cargo clam shell doors and portable vehicle loading enhance
the movement of vehicles and heavy cargo.
FOR OFFICIAL USE ONLY
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SPECIAL TOOLS AND EQUIPMENT
1. Special tools provided with the aircraft consisted of thirty-three
(33) items and are generally inferior in quality and design with the
exception of the inclinometer; however, from a logistical viewpoint,
the small number of special tools required is significant (33 items
compared to 62 items for the H-34).
NOTE: Special tools referred to for both H-34 and H-36 include those
required to perform first through fourth echelon maintenance.
2, One of th e common tools, a spark plug wrench, was used on
the H-34 successfully and is considered superior from a design and
logistical viewpoint (1 piece construction instead of 5),
3. Ground handling equipment provided is considered bulky,
cumbersome and inferior, with. the bee tion of the air ct ~,:+}>re ;o ,
4. Hangar facilities, storage space and camouflage requirements
are greater than for the H-34 primarily due to the fact that the H-36
does not incorporate provisions for main rotor blade and pylon folding.
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1. The overall maintenance characteristics incorporated in this
design are not as complex as comparable American helicopters. With
the exception of deficiencies listed, the equipment required only nominal
maintenance primarily composed of inspection and lubrication.
2. The systems and component designs are, in many cases,
considered an innovation of simplicity, which is a desirable feature.
The aircraft can be maintained with a relatively high availability
rate utilizing only average mechanics. Logistical and technical support
requirements are less When compared to the H-34.
3. Component design in relation to performance, manufacturing
costs, life expectancy and operating efficiency indicate that the items
were developed to obtain maximum mechanical reliability and
simplicity. It appears that sophistication was sacrificed to reduce
logistical and technical support requirements.
4. Design safety features incorporated on the aircraft are
questionable when compared to military and civil standards. However,
with adequate crew training, the helicopter can be operated with minimum
risk.
FOR OFFICIAL USE ONLY
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