Aviation Accident Report: Standard Airways Flight 388C
CIVIL AERONAUTICS BOARD
AIRCRAFT ACCIDENT REPORT
STANDARD AIRWAYS, INC. LOCKHEED CONSTELLATION, L-1049G
N 189S, MANHATTAN MUNICIPAL AIRPORT
MANHATTAN, KANSAS, MAY 28, 1963
On May 28, 1963, at 1746 c.s.t., a Standard Airways, Inc., Lockheed Constellation L-1049G, N 189S, operating as Civil Air Movement (CAM) Flight 388C, crashed and burned during the final stages of a VFR landing approach to runway 21 at Manhattan Municipal Airport, Manhattan, Kansas.
The aircraft was substantially damaged by impact and was destroyed in the resultant fire. None of the six crew members were injured and only one of the 64 military passengers sustained serious injury.
The Board determines the probable cause of this accident was the inflight reversal of the No. 3 propeller due to a propeller power unit malfunction resulting from improper maintenance practices and inspection procedures.
A Standard Airways Lockheed Constellation, L-1049G, N 189S operating under a military contract as Civil Air Movement (CAM} Flight 388C, crashed and burned during a Visual Flight Rules (VFR) landing approach to Manhattan Municipal Airport, Manhattan, Kansas, on May 28, 1963, at 1746 c.s.t. There were 64 military passengers and a crew of six. There were no fatalities and only one passenger was seriously injured.
Fllght 388C was scheduled nonstop from Daggett, California, to Manhattan, Kansas. The crew consisted of Captain David R Brown, First Officer Joseph A Merlo, Flight Engineer Peter H Raymen, Stewardesses Sandra R. Wise. and Ann H. Allen, and Pilot/Observer Penrod Rideout who was assigned to this flight to observe operating procedures preparatory to transitioning to L-1049 type aircraft.
The aircraft was serviced with fuel and oil at the company's maintenance base in Long Beach, California, and departed for Daggett at 1210. The only maintenance required prior to departure was the replacement of the Y-lead, high tension ignition leads, and spark plugs of cylinders Nos. 12 and 13 on the No. 3 engine.
Upon arrival at Daggett at 1245, Federal Aviation Agency (FAA) and Military Air Transport Service (MATS) inspectors conducted a visual ramp inspection of the aircraft and interrogation of the crew. The only discrepancy noted was a small area of corrosion on the underside of the aft fuselage in the vicinity of the lavatory service area.
Sixty-four U. S. Army personnel boarded at Daggett and were briefed by a stewardess regarding emergency exit locations, emergency equipment and procedure. The aircraft required no servicing or maintenance and there were no carry-over maintenance items reported. Takeoff gross weight was computed to be 116,520 lb. This weight and the center of gravity (c.g.) were both within prescribed limits.
Flight 3880 departed Daggett at 1345 under an Instrument Flight Rules (IFR) flight plan to Manhattan, Kansas, with an estimated time en route of 4 hours and 30 minutes. The flight proceeded without incident and at 1720, in the vicinity of Edina, Kansas, canceled its IFR flight plan with Kansas City Air Route Traffic Control Center The let-down was made in clear weather and the aircraft entered normal lefthand traffic pattern for a VFR approach to runway 21 at the Manhattan Municipal Airport. This runway is 5,500 feet long, 100 feet wide, and the final elevation is 1,060 feet m.s.l. The FAA Flight Service Station located on the airport reported the surface wind as west-northwest six knots and the altimeter settling 29.97 inches. The skies were clear and the visibility 15 miles.
According to the captain, who was flying the aircraft from the left pilot seat the flight entered an extended downwind leg at an altitude of 2,500 feet m.s.l. The aircraft was turned onto a left base leg for runway 21 at which time the before landing checklist was completed; landing gear extended, flaps set to 60 percent and 2400 r.p.m. selected for all propellers. A left turn onto the final approach was completed at an altitude of approximately 900 feet above ground level (a.g.l.) at an airspeed of 140 knots. During the final portion of the approach 100 percent flaps were extended, and the airspeed was reduced to 120 knots.
At an altitude estimated to approximately 170 feet a.g.l., the right wing down, the aircraft yawed to the right, and a higher than normal rate of descent was noticed. The captain stated that his first impression was that the aircraft had entered a down draft but would fly out of it momentarily. However, the descent continued and the control forces became greater. Realizing that this was an abnormally high rate of descent he added “. . . considerable . . ." power to all four engines. Immediately following the power application, control forces became stronger and the rate of descent increased alarmingly. Within seconds the aircraft struck the ground.
The flight engineer recalled that after increasing the r.p.m. to 2400 on all four propellers during the approach, the No. 3 propeller surged to about 2475 r.p.m. He thereupon placed the No. 3 propeller control switch in the manual position and increased r.p.m. to 2400, then repositioned the switch to automatic. The r.p.m. remained nearly steady with only slight fluctuations. His attention was next drawn towards other duties in preparation for landing. During this time he felt the aircraft sink, followed by an application of high engine power. He quickly returned his attention to the panel but could only remember seeing the engines manifold pressures at approximately 50 inches hg prior to ground impact.
The observer/pilot, who was standing between the captain's and first officer's seats, recalled that shortly after entering the final approach he observed the propeller r.p.m. increase approximately 100 r.p.m. and then return to the original setting of 2400 r.p.m. This fluctuation occurred three times. Then, following extension of full flaps, he observed the captain reduce power to approximately inches hg and almost immediately the rate of descent increased and the aircraft yawed to the right. The aircraft was at an altitude of approximately 75 feet a.g.l. when he observed the No. 3 propeller reverse indicating the light come on and shouted, "No. 3 is in reverse" This shouted warning was concurrent with the application of engine power and was not heard by the captain. None of the other flight crew members saw the reverse light illuminate.
Persons on the ground who witnessed the accident generally agreed that the approach appeared normal until the aircraft reached a point approximately 1/3 of a mile from the airport. It was then observed to settle abruptly and contact the ground several hundred feet short of the runway.
Initial impact occurred in a wheat field, 546 feet from the approach end of runway 21. At this point the aircraft was in a right bank of approximately 15 degrees and aligned slightly to the right of the runway centreline. The aircraft bounced once, then continued through the wheat field on all three landing gears until it struck an earth embankment. 3–1/2 feet high, located 176 feet from the end of the runway. This impact sheared the right main landing gear and the nose gear from the aircraft. The right wing separated from the fuselage when the aircraft contacted the end of the runway. The aircraft slid a distance of 774 feet down the runway, during which time the left main landing gear failed followed by separation of the left wing. The fuselage came to rest on a heading of approximately 270 degrees, 72 feet from the right side of the runway.
A rapid and orderly emergency evacuation was carried out by all passengers and flight crew members through emergency exits and the rear passenger door. Small fires were ignited in the wing and fuselage fuel tanks during the impact sequence but did not reach major proportions until after the aircraft was completely vacated. The fire increased in magnitude and destroyed the fuselage and both wings.
The entire flight control system and all associated hydraulic booster control units were examined; all were capable of normal operation prior to impact. All three landing gears were in the down and locked position; and the wing flaps were symmetrically extended to the full down position at impact. There was no evidence of any aircraft structural or system failure prior to impact.
Examination of the engines revealed no evidence of any operating distress prior to impact; however, a number of discrepancies affecting the airworthiness of the engines were disclosed and are listed as follows.
1. The fire extinguisher manifold to the No. 2 PRT on the No. 2 engine had a wear hole five inches from its outlet.
2. The magneto lead connector plug on the No. 2 engine was not safetied.
3. Connector plugs for the left and right cowl flap actuators on the No. 2 engine were safetied backwards.
4. The spark plugs in engines Nos. 3 and 4 were of a type not approved for use in the TC18DA series engines.
5. The timing ring lock nut of the left distributor of the No. 4 engine was not safetied.
6. The retaining nut of the No. 2 PRT on the No. 4 engine was not safetied.
Examination of the Curtiss Electric Propeller assemblies revealed extensive impact damage generally concentrated on the blades and slip ring assemblies. Other than the No. 3 propeller assembly, the remaining propellers showed no evidence of operating failure prior to impact. Propeller power unit settings indicated blade angles at impact at 27 degrees for propellers Nos. 1, 2, and 4. The No. 3 propeller was at a blade angle of plus one-degree; in the reverse pitch range. The specified low blade angle setting is 23.7 degrees.
Detailed examination of the No. 3 propeller power unit (S/N 165047, S/N 11819. S/N A-119) revealed the threaded brake cage of the pitch change motor was unscrewed three threads and that the two cage lock safety bolts were missing. The armature of the pitch change motor was free to rotate. A brake clearance measurement indicated the brake clearance to be .052 inches. Normal specified clearances; inspect .008 to .018, reset .008 to .012. Two of the brake cage locking bolt slots were worn excessively, with the wear pattern extending into the cage retaining threads. These worn areas were 5/16 and 21/64 of an inch in length and were diametrically opposed. The lower cage shoulder showed indication of wear by the locking bolts over a surface dimension of 13/32 and 17/32 of an inch. The outer diameter of the splined disc duplex brake plate assembly contained two areas of heavy battering. Two of the brake cage window struts showed indication of heavy battering in the unscrewed direction in the area above the normal position for the brake cage wrench. The brake facing was in place and its measured thickness was .214 to .216; (specified thickness .169 to .259). The power unit motor was energized and speed reducer operation was obtained. The limit switches functioned normally.
Inspection of the Nos. 1, 2, and 4 propeller power units revealed no evidence of operating distress prior to impact.
The last overhaul, subsequent inspection, and maintenance records pertaining to propeller power unit S/N 165047 were examined. It was determined that the last overhaul of this unit was accomplished on July 6, 1962, at which time a zero time since overhaul (TSO) was established. Cardex records for this unit indicate that following overhaul it was first installed in the No. 3 position on N 9742Z on January 14, 1963, with a TSO of 00 hours. The Cardex records further established that the unit was removed from N 9742Z on February 4, 1963, and was installed in the No. 3 position of N 189S with a TSO of 4.7 hours. There were no Cardex records entries for the unit from July 6, 1962 - January 14, 1963. However, an entry in the propeller logbook of aircraft N 9742Z indicates that the unit was installed in the No. 3 position of that aircraft on July 10, 1962. The records indicate that the TSO of this power unit from the date of installation on July 13, 1962, until its removal from N 9742Z on February 4, 1963, was 194.8 hours.
Additionally, the component overhaul time sheets in Standard's maintenance manual for N 9742Z, approved by the FAA on October 29, 1962, lists a power unit S/N 801 in the No. 3 position. TSO was shown as 411 hours, and approved overhaul time 2,500 hours.
Aircraft flight log entries relating to power unit S/N 165047 were examined and the following significant discrepancy write-ups on the unit were revealed:
The mechanic who reinstalled the power unit in the No. 3 position following the resetting of the propeller blade feather angle stated that both the external safeties and the brake cage locking bolts were checked, and were in place. According to the records this was the last time work was accomplished on this unit prior to the accident.
Civil Air Regulations (CAR‘s) require the carrier to prepare and maintain a maintenance manual which contains full information pertaining to the maintenance, repair, and inspection of aircraft and equipment, and that the content of this manual be acceptable to the Administrator of the FAA. Provisions within the regulation specify that the manual must contain a schedule of the aircraft's component parts which are subjected to maintenance functions along with the approved time limits at which such functions are to be conducted. All repairs, alterations, and maintenance are to be performed in accordance with procedures set forth in the manual.
The procedures used by Standard Airways for component identification and time control were implemented through the use of the Cardex system in conjunction with the manual and aircraft flight log.
A review of these records revealed numerous instances of erroneous identification and inaccurate accounting of the time controlled components installed on aircraft N 189S. Principal examples of these discrepancies are listed below:
1. The No. 3 engine on aircraft N 189S was identified in the records as S/N 547255 rather than S/N 547253.
2. Engine component records did not agree entirely with respect to serial numbers, date of installation, replacement times, and adjusted TSO's.
The aforementioned discrepancies were documented in various factual reports. At the public hearing, Standard Airways volunteered an admission that the factual statements accurately portrayed the discrepancies.
Civil Air Regulations also require that the maintenance manual clearly outline the duties and responsibilities of maintenance personnel and that they be acceptable to the Administrator. Standard's Maintenance Organization as set forth in the maintenance manual, was comprised of a Maintenance Coordinator, Maintenance Representative, and a Chief Inspector.
The duties of the Chief Inspector as specified in the manual were that, "The Chief Inspector shall be responsible for all company aircraft and engine records, for compliance with All Civil Air Regulations as regards maintenance, AD notes, and other regulations . . . he shall be responsible for the acceptance or rejection of all work done on company equipment by maintenance contractors, and shall have the authority to accept or reject such work . . . ."
In a letter dated March 27, 1963, the designated Chief Inspector, informed the CAB by letter that as of March 3, 1963, he had been relieved of these duties. From that date until the time of the accident the records do not indicate that a replacement was appointed.
According to the maintenance records the aircraft was certificated by the FAA on August 3, 1962, and the portion of the manual concerning the maintenance organization was approved on December 14, 1962.
On February 18-19, 1963, a MATS inspection team conducted an inspection of Standard's Maintenance Facility at Long Beach, California. FAA inspectors were present during this inspection and the FAA report states in part ". . . Briefly the results of the inspection were satisfactory. Standard's rapid expansion was discussed, as was the carrier‘s expected acquisition of Las Vegas Hacienda, Inc., Air Station Facilities. The problem of monitoring maintenance when the aircraft are physically located throughout the United States was also discussed. However, all these were mentioned in the light of what might result if close monitoring of their operation were not maintained, and changes in their maintenance adopted when it became apparent that these changes were needed . . . The only discrepancy that was noted, . . . was that the component time control cards were not being kept up to date . . ."
On April 9, 1963, the FAA held a meeting with Standard in order to rectify deficiencies in the company's maintenance program. Items for discussion in the category of maintenance records included component serial numbers, TSO times, and missing cards for aircraft components. It was agreed at this meeting that a closer monitoring of logbooks and maintenance records was needed. It was also agreed that the FAA would continue with the inspection of Standard‘s records and maintenance manuals and that the company would make the necessary revisions and corrections as soon as possible. The completion date of this project was not to exceed May 27, 1963; however, as of the date of the accident it had not been completed. It may be well to note that following the accident and during the period the accident investigation was in process, six additional aircraft were certificated by the FAA and were incorporated into Standard‘s aircraft fleet.
On June 3, 1963, six days after the Manhattan, Kansas, accident, another Standard Airways, L-1049G, N 9742Z, experienced a propeller malfunction in flight. The captain of the flight stated that while cruising at 9,000 feet in the vicinity of Elkins, West Virginia, the No. 2 propeller surged twice from 2300 to 2800 r.p.m. Attempts to control the propeller through the use of the manual propeller control switch were unsuccessful. The propeller was then feathered and the flight continued to Philadelphia and landed without further difficulty. After landing, the No. 2 propeller was unfeathered and during ground run-up the propeller inadvertently went into reverse pitch.
On examination of the No. 2 propeller assembly the spinner was removed and the power unit (S/N 168011) brake cage was found completely unscrewed lying loose inside. The two cage lock safety bolts were missing from the unit and two of the brake cage locking bolt slots were worn excessively. The outer periphery of the splined disc duplex brake plate assembly was peened for approximately 180 degrees. The brake lining was well within limits. A part of a bolt, similar in appearance to the specified brake cage locking bolt (P/N 106024), was found on the ground under the engine. This portion of the bolt was examined and found to be within the manufacturer's metallurgical design specification tolerances. The threaded brake cage was reinstalled to the locked position and the brake clearance was found to be .011 inches. The power unit was energized and normal propeller operation was obtained.
It is to be noted that on May 29, 1963, both the CAB and the FAA contacted Standard Airways, and requested that the propeller power units on N 9742Z be inspected "as soon as possible" regarding the possibilities of a similar propeller malfunction. The crew of N 9742Z stated they had been advised by the company of the accident at Manhattan but did not receive specific information as to the nature of the propeller malfunction. Moreover, it was stated that no instructions were received from the company to inspect the propellers or power units on N 9742Z prior to the incident on June 3, 1963.
Examination of the No. 3 propeller assembly revealed an impact blade angle of plus one-degree, this is 22.7 degrees below the specified low blade angle setting and in the reverse pitch range. The threaded brake cage locking bolts were missing and the cage had unscrewed three threads. This resulted in an excessive brake clearance of ·052 which rendered the brake incapable of propeller control.
It was evident from examination of the brake cage that it had not been tightened properly at the time it was last installed and had been subjected to repeated cycles of loosening and tightening over a prolonged period of time. If the cage is not properly tightened during installation it will tend to work loose even with the safety bolts in place due to the high torque of the pitch change motor and the drag by the brake. As the pitch change motor calls for a lower blade angle the cage will tend to unscrew and, conversely, a higher blade angle selection will produce a tightening effect.
The wear patterns on the cage safety bolt slots were indicative of repeated cycling predominantly in the loosening direction. These repeated cycles of loosening and tightening eventually caused failure of the safety lock bolts. This was evidenced by the battered condition of the splined disc duplex brake as well as the wear patterns on the top and lower surfaces of the inboard brake cage ring. After the failure of the safety lock bolts, the cage would tend to unscrew to whatever extent would be provided by the cycling action of the pitch change motor ln addition to normal vibration effect.
It was learned from the crew of N 189S that the No. 3 propeller r.p.m. surged when approach power was being established for the landing at Manhattan. This surging was due to the lack of adequate propeller brake action. As the airspeed and power were reduced for landing the synchronizer continued to maintain the selected 2400 r.p.m. However, with the brake inoperative on the No. 3 power unit, the blades of that propeller continued to move to a lower blade angle in order to maintain the selected r.p.m. as the airspeed was reduced. Eventually, the blades went beyond the low limit switch and into the reverse pitch range. The fact that this propeller had moved into the reverse range was confirmed by the observer/pilot who saw the No. 3 reverse light come on when the aircraft was approximately 75 feet above the ground.
With the No. 3 propeller in the reverse pitch range, the increased drag would tend to yaw the aircraft to the right, the right wing would drop due to loss of lift behind the propeller disc, and an increased rate of descent would result. Addition of engine power at the airspeed involved (115 knots or less) resulted in forward thrust from engines Nos. 1, 2, and 4, and negative thrust with high drag forces from engine No. 3. The combination of these forces at the airspeed and altitude at which N 189S was operating, resulted in an accelerated descent that could not be overcome prior to contact with the ground.
Descent rate calculations using known factors of weight, airspeed, engine power, and aircraft configuration were made by the Lockheed Aircraft Corporation. A descent rate of approximately 730 feet per minute prior to the propeller malfunction was calculated using the above factors. Since absolute values for loss of wing lift and drag, due to reversal of the No. 3 propeller, were not available, assumed values of 15 percent loss of lift over the right wing and 6,000 pounds increase drag were used. It was found that with all engines developing approach power, the No. 3 propeller in reverse thrust, and the Nos. 1, 2, and 4 propellers in forward thrust, the descent rate would increase to about 1,845 feet per minute. Then, with approximately 50 inches of engine power applied to this combination it was indicated that the descent rate would eventually decrease to about 535 feet per minute.
Since it is difficult to predict or determine the exact blade angles and engine power that may have existed during each of these flight regimes, the calculations are intended only as a rough approximation of the relative magnitudes of the sudden increase in descent rate with which the pilot was suddenly confronted. Moreover, the value for drag used in the calculations is considered conservative in that no attempt was made to account for the increase in drag due to presumed large control surface deflections during the maneuver.
In addition, a series of L-1049G flight simulator runs were conducted in order to obtain more refined information concerning aircraft controllability under essentially the same conditions as used in the calculations. Data supplied to the simulator produced a 15 percent lift loss over the right wing due to propeller reversal and a less conservative drag value of approximately 9,000 pounds. The result of these tests, although qualitative, produced an initial descent rate of approximately 1,800 feet per minute and indicated that under these prescribed conditions of flight, Successful recovery could not be effected.
Examination of the four engines revealed no evidence of operating distress prior to impact; however, all of the engines did exhibit discrepancies the nature of which did adversely affect the airworthiness qualification of the aircraft. Although these discrepancies did not in themselves directly relate to the cause of the accident, they are indicative of inadequate maintenance practices and inspection procedures on the part of the carrier.
Moreover, a comprehensive review of all maintenance records pertaining to aircraft N 189S revealed that these records both in terms of quantity and quality were not sufficient to present an accurate history of the aircraft and engine components. Many instances of inaccurate, erroneous, and incomplete data were found including evidence of time controlled components remaining on the aircraft beyond replacement times.
Similarly, maintenance records for the failed propeller power unit (S/N 165047), were conflicting, incomplete, and from them, accurate component time control information could not be obtained. However, on the basis of all investigative data, it can logically be concluded that the unit was installed in the No. 3 position of aircraft N 9742Z on July 10, 1962, following the overhaul on July 6, 1962. It remained in this position until February 4, 1963, at which time it was removed from N 9742Z and installed in the No. 3 position of aircraft N 189S. It remained in this position until the time of the accident. Consequently, the unit was in the No. 3 positlon of N 9742Z on January 6, 1963, when, according to the aircraft flight logs all propeller power units were adjusted.  This is the last record of any adjustment to this unit which would have involved removal and reinstallation of the brake cage.
As previously stated, the failure of the safety lock bolts and the unscrewing of the brake cage resulted from improper tightening of the cage during installation. The recommended procedures for installing the cage specify that a cage wrench be utilized for this function. However, testimony of maintenance personnel indicates Standard Airways' Maintenance Base did not possess a cage wrench, but used a strap wrench for this purpose. Because of the tapered surface of the cage, it is considered highly unlikely that proper tightening of the cage would be obtained through the use of a strap wrench. This may well account for two different cage assemblies wearing through the safety bolts and becoming unscrewed at nearly the same time. These were the No. 3 cage (Power Unit 165047) on N 189S which failed on May 28, 1963, and the No. 2 cage (Power Unit 168011) on N 9742Z which failed on June 3, 1963.
The carrier's maintenance manual states that the Chief Inspector is responsible for compliance with all CAR's as regards maintenance, and that he shall be responsible for the acceptance or rejection of all work performed on company equipment by maintenance contractors. Additionally, the last designated Chief Inspector prior to the accident testified that it was his responsibility to, ". . .observe techniques, proper tools, proper equipment, proper parts," and when the Job was completed to, ". . . go out and go over the Job and see that it was properly done." Yet, the records indicate that the position of Chief Inspector was unoccupied from March 3, 1963, until after the accident occurred. Testimony by officials of the carrier was to the effect that acquisition of the Long Beach Maintenance Facility resulted in unnecessary duplications in the maintenance organization and that verbal instructions had been given as to who was the Chief Inspector during this period. This is pointed out only to illustrate that: Improper tools and procedures and inadequate inspection procedures were employed in the maintenance of two propeller power units that failed in flight, and that; within the framework of the carrier's maintenance system it is the Chief Inspector who is responsible for the detection of improper equipment and procedures, and that; although there was a designated Chief Inspector at the time the involved power unit brakes were adjusted, the records indicate this position was not filled for a period of time in which aircraft maintenance was continually performed. Although it may or may not have been understood by maintenance personnel who the Chief Inspector was during this period, the lack of a well organized maintenance structure is apparent.
It is evident that as early as February 18, 1963, both Standard and the FAA were aware of discrepancies in Standard's maintenance organization and in the maintenance records of Standard's L-1049 aircraft. In this regard a meeting was held on April 19, 1963, by FAA with company maintenance representatives in which the record status and maintenance organization were discussed in detail. In fact, a project completion date of May 27, 1963, was fixed wherein these discrepancies were to be corrected.
In summation, a review of all evidence indicates that the carrier's maintenance organization did not provide adequate maintenance records for N 189S, nor did it insure the performance of proper maintenance practices or inspection procedures necessary for adequate standards of airworthiness. These practices resulted in the failure of a propeller power unit directly linked to the cause of this accident.
The Board determines the probable cause of this accident was the inflight reversal of the No. 3 propeller due to a propeller power unit malfunction resulting from improper maintenance practices and inspection procedures.
The Board submitted recommendations to the Administrator during the investigation of this accident. These recommendations directly related to the cause of this accident are set out in attachments A and B.
BY THE CIVIL AERONAUTICS BOARD.
/s/ ALAN S. BOYD
/s/ ROBERT T. MURPHY
/s/ CHAN GURNEY
/s/ G. JOSEPH MINETTI
/s/ WHITNEY GILLILLAND
- All times herein are central standard based on the 24-hour clock
- There ls no airport traffic control tower at Manhattan Municipal Airport.
- The L-1049 propeller system contains individual early warning reverse lights which illuminate when the appropriate propeller blade angle is 6 to 8 degrees below the low pitch setting. The reverse lights on N 189S were located in the lower left-hand corner of the center instrument panel.
- The propeller power unit consists of three components; pitch change motor, speed reducer, and brake assembly. These units function electrically and mechanically to change and maintain selected blade angles.
- The propeller brake assembly is the component of the power unit which prevents the propeller blade angle from moving beyond the Selected value called for by the synchronizer. Specified clearances must be maintained in the brake assembly in order to perform this function. The is a part of the brake assembly which assists in maintaining the specified brake clearances.
- All decimal measurements are denoted in inches.
- The Cardex System was used as part of the Standard Airways Maintenance Records to control the operation and replacement of time controlled aircraft components and parts. Specifically, a card was kept for each component to show, identification, replacement time, time on, time off, and time since new or overhaul.
- The recommended procedure for installing the cage is detailed in the manufacturer's Maintenance Manual. It calls for tightening the brake cage by using a cage wrench (ST-1299) and a two-pound hammer until a specified clearance of .001 is obtained between the five segment shoulders and the outer brake cowl housing. The cage is then further tightened 1/2 inch plus whatever distance is necessary to align the safety lock bolt holes.
- CAR Sec. 42.32(d}(1)
- The specified brake clearances range from .008 to .018. When these clearances are exceeded propeller surging can occur and a critical loss of propeller control can be encountered.
- This same type of failure was evidenced on the No. 2 power unit brake assembly of aircraft N 9742Z at Philadelphia June 3, 1963.
- Ref: Page 3
- All four propeller power units including (S/N 168011), the failed unit on N 9742Z, were adjusted at this time.