The Partenavia unexplained accident at Essendon in 1978
Thread Starter
Cutting the mixture in order to induce an instant failure was normal procedure among general aviation operators in those days and considered perfectly safe. Even to this day, the technique is still used by some instructors to simulate engine failures at low altitude in multi-engine aircraft despite CASA published material warning of the inherent dangers of student mishandling. The subject has previously been extensively covered in Pprune pages.
Surprisingly, the wisdom of mixture cutting an engine soon after take -off at Essendon that took place over the immediate built up area was not mentioned in the accident report. Maybe because in that era, the risk of mis-handling by a student was considered by many to be minimal.
However it was sheer bad luck in this case where the combination occurred of mixture cut engine failure happening simultaneously as flap retraction was occurring and the strong inference that the student froze on the trim switch due to stress of the moment at night. As the saying goes, "Sh*t happens." But it sure picked the wrong time to happen on that night..
Surprisingly, the wisdom of mixture cutting an engine soon after take -off at Essendon that took place over the immediate built up area was not mentioned in the accident report. Maybe because in that era, the risk of mis-handling by a student was considered by many to be minimal.
However it was sheer bad luck in this case where the combination occurred of mixture cut engine failure happening simultaneously as flap retraction was occurring and the strong inference that the student froze on the trim switch due to stress of the moment at night. As the saying goes, "Sh*t happens." But it sure picked the wrong time to happen on that night..
Last edited by Centaurus; 21st Aug 2017 at 14:40.
Thread Starter
Adding to the subject of an unexplained accident - in this case the suspicion that a trim tab was involved - was that of an RAAF MB 326 Aeromacchi jet trainer that in 1969 crashed under mysterious circumstances near the mouth of the Avon River close to RAAF Base East Sale.
https://www.google.com.au/search?sou...k1.7XrURbyK1XQ
The aircraft was on a low level cross-country exercise with an instructor and trainee instructor aboard. Some minutes after departing East Sale and close to the area of the Avon River the aircraft was seen by witnesses to suddenly pitch up almost vertically, then dive into the ground. Both pilots were killed. There was no radio calls.
Investigators discovered there had been a history of Macchi unexplained elevator electrical trim operation during previous months both at East Sale and RAAF Base Pearce in WA. One example at East Sale was where a trainee instructor flying from the back seat was in the climb shortly after lift off when the aircraft pitched up violently. He immediately let go of the controls because he thought the instructor in the front seat must have seen another aircraft or a bird and taken avoiding action. The instructor in the front seat felt the aircraft pitch up and instinctively took over control to avoid a stall. The cause of the pitch up was never determined.
On another occasion a Central Flying School instructor was testing a trainee instructor for his instrument rating. During a recovery from an unusual attitude on instruments the aircraft went into a steep dive from 15,000 feet. Both pilots stated the aircraft was vertical passing 10,000 ft with them joining to pull back hard on the control column to recover. Recovery was completed at 1500 feet agl. In each case the elevator trim tested normal on the ground
The Macchi trim control was a `witches hat` switch on top of the control column operating elevator and aileron trim tabs. A test flight was carried out to see how quickly a pilot could react to an uncommanded elevator trim change. During level flight at 200 knots and 5000 feet the Macchi was flown with the pilot in the front seat and the investigating officer in the back (instructor position) seat. The plan was the investigating officer was to operate full back elevator trim without notifying the pilot while the aircraft was in level flight. The purpose of the flight was to see how long it took for the elevator trim operation to take effect and the action of the pilot once he detected the change of trim.
Initially there was a slight pitch up followed within seconds a violent pitch up as the trim reached full rear stop. The recovery action from the steep nose up attitude required the pilot to quickly roll the aircraft to 90 degrees angle of bank towards the nearest horizon in order to get the nose to drop and then use ailerons to level the wings.
This recovery action mirrored witnesses reports when they saw the crash of the Macchi near the Avon River. That is to say the aircraft was seen to roll hard in one direction as it reached a vertical climb and had the wings level in the ensuing dive recovery but too late to avoid ground impact.
Until the cause of the Macchi trim defect could be established, steps were taken to disconnect the trim tab to one elevator on all RAAF Macchi trainers. In turn this would lessen the chances of loss of control if only one trim tab was operational and ran away. It was about two years later when an airman at Pearce was doing a walk-around inspection of a Macchi prior to a night flying exercise. He had switched on all external lights as part of the inspection and that included the anti-collision rotating light. To his astonishment he saw the elevator trim tab oscillating in tune with the rotation of the anti-collision light. Further investigation revealed a crushed electrical loom inside the fuselage adjacent to the tail-plane. The mystery of the uncommanded elevator electrical trim operation had been solved. Following rectification, all Macchi elevator trim tabs were later returned to service.
P.S. Centaurus happened to be the DFS (Directorate of RAAF Flying Safety) investigating officer.
https://www.google.com.au/search?sou...k1.7XrURbyK1XQ
The aircraft was on a low level cross-country exercise with an instructor and trainee instructor aboard. Some minutes after departing East Sale and close to the area of the Avon River the aircraft was seen by witnesses to suddenly pitch up almost vertically, then dive into the ground. Both pilots were killed. There was no radio calls.
Investigators discovered there had been a history of Macchi unexplained elevator electrical trim operation during previous months both at East Sale and RAAF Base Pearce in WA. One example at East Sale was where a trainee instructor flying from the back seat was in the climb shortly after lift off when the aircraft pitched up violently. He immediately let go of the controls because he thought the instructor in the front seat must have seen another aircraft or a bird and taken avoiding action. The instructor in the front seat felt the aircraft pitch up and instinctively took over control to avoid a stall. The cause of the pitch up was never determined.
On another occasion a Central Flying School instructor was testing a trainee instructor for his instrument rating. During a recovery from an unusual attitude on instruments the aircraft went into a steep dive from 15,000 feet. Both pilots stated the aircraft was vertical passing 10,000 ft with them joining to pull back hard on the control column to recover. Recovery was completed at 1500 feet agl. In each case the elevator trim tested normal on the ground
The Macchi trim control was a `witches hat` switch on top of the control column operating elevator and aileron trim tabs. A test flight was carried out to see how quickly a pilot could react to an uncommanded elevator trim change. During level flight at 200 knots and 5000 feet the Macchi was flown with the pilot in the front seat and the investigating officer in the back (instructor position) seat. The plan was the investigating officer was to operate full back elevator trim without notifying the pilot while the aircraft was in level flight. The purpose of the flight was to see how long it took for the elevator trim operation to take effect and the action of the pilot once he detected the change of trim.
Initially there was a slight pitch up followed within seconds a violent pitch up as the trim reached full rear stop. The recovery action from the steep nose up attitude required the pilot to quickly roll the aircraft to 90 degrees angle of bank towards the nearest horizon in order to get the nose to drop and then use ailerons to level the wings.
This recovery action mirrored witnesses reports when they saw the crash of the Macchi near the Avon River. That is to say the aircraft was seen to roll hard in one direction as it reached a vertical climb and had the wings level in the ensuing dive recovery but too late to avoid ground impact.
Until the cause of the Macchi trim defect could be established, steps were taken to disconnect the trim tab to one elevator on all RAAF Macchi trainers. In turn this would lessen the chances of loss of control if only one trim tab was operational and ran away. It was about two years later when an airman at Pearce was doing a walk-around inspection of a Macchi prior to a night flying exercise. He had switched on all external lights as part of the inspection and that included the anti-collision rotating light. To his astonishment he saw the elevator trim tab oscillating in tune with the rotation of the anti-collision light. Further investigation revealed a crushed electrical loom inside the fuselage adjacent to the tail-plane. The mystery of the uncommanded elevator electrical trim operation had been solved. Following rectification, all Macchi elevator trim tabs were later returned to service.
P.S. Centaurus happened to be the DFS (Directorate of RAAF Flying Safety) investigating officer.
IIRC there was another contributor to Macchi longitudinal trim incidents.
A number of pilots experienced strong nose down trim change, with almost uncontrollable control forces, while accelerating in a dive just after spin recovery. The cause was found to be that, during a spin, the trim switch could contact the pilot's harness buckle and apply full nose down trim. The stick force used to hold pro-spin control inputs and the low "q" during the spin resulted in full nose down trim deflection with no noticeable stick force changes.
It became clear that the Macchi longitudinal trim system had far more authority than required to be able to trim the aircraft for the full flight envelope and weight/cg range.
The RAAF had previous experience with the runaway of electric trim system (with excessive authority) with the Canberra. Apparently the message of the risks of high authority electric trims combined with reversible control systems was forgotten.
A number of pilots experienced strong nose down trim change, with almost uncontrollable control forces, while accelerating in a dive just after spin recovery. The cause was found to be that, during a spin, the trim switch could contact the pilot's harness buckle and apply full nose down trim. The stick force used to hold pro-spin control inputs and the low "q" during the spin resulted in full nose down trim deflection with no noticeable stick force changes.
It became clear that the Macchi longitudinal trim system had far more authority than required to be able to trim the aircraft for the full flight envelope and weight/cg range.
The RAAF had previous experience with the runaway of electric trim system (with excessive authority) with the Canberra. Apparently the message of the risks of high authority electric trims combined with reversible control systems was forgotten.
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"Centaurus" is missing the point completely by concentrating on the engine failure exercise! The aeroplane crashed with full power applied and full nose down Trim applied! Even if the trim system had run fully down the pilot should have been able to overcome a total force of only 75 lbs! The Department had not met their own
requirements for flight tests and certified an aeroplane that did not meet FAR23-143c
requirements for flight tests and certified an aeroplane that did not meet FAR23-143c
While I no longer recall the certification basis or FAR23 amendment status applicable to the Partenavia, I am unaware of any FAR23 handling or controllability standards, past or present, which are conducted at the trim travel limit. FAR 23.143 does not require this.
Reaching the trim limit in flight should only result from pilot action. The failure mode and effects analysis of the trim system should show that a trim runaway is highly unlikely and must not occur in case of a single failure.
The Australian regulator certificated FAR23 aircraft under bilateral agreements, it was rare to conduct any flight testing.
However, in the case of the Partenavia, the stalling speeds hence Cl max appeared optimistic cf similar aircraft. Tests were done to determine the accuracy of the pitot static pressure corrections. Further, the importer decided to re-run landing distance tests, possibly as a result of the pitot static tests.
It would have been a nonsense to do a completely new certification exercise on the dozens of new types / models arriving in Australia.
Reaching the trim limit in flight should only result from pilot action. The failure mode and effects analysis of the trim system should show that a trim runaway is highly unlikely and must not occur in case of a single failure.
The Australian regulator certificated FAR23 aircraft under bilateral agreements, it was rare to conduct any flight testing.
However, in the case of the Partenavia, the stalling speeds hence Cl max appeared optimistic cf similar aircraft. Tests were done to determine the accuracy of the pitot static pressure corrections. Further, the importer decided to re-run landing distance tests, possibly as a result of the pitot static tests.
It would have been a nonsense to do a completely new certification exercise on the dozens of new types / models arriving in Australia.
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The first PN68 was certified in Australia had no Autopilot fitted, the next 2 arrived had Autopilots fitted The Department asked for flight tests as required by ANO 101-22 this was bypassed! After a trim runaway at Moorabbin a Modified to SB41 aeroplane the Department then finally in 1989 carried out flight test CAA Document M131-515-4 which proved that technically even with the SB41 fitted the PN68 still does not meet FAR23-143c
If the Department had done their job 6 innocent lives would not have been lost
If the Department had done their job 6 innocent lives would not have been lost
Last edited by 6317alan; 22nd Aug 2017 at 07:57.
6317alan, it is now not clear to me, aka I don't recall, if the Partenavia electric trim system should have been tested for control forces over the operational speed/cg range at full trim deflections or by virtue of the trim operating cable diameter tested by runaway, recognition, reaction tests.
Not knowing the cert basis and not having access to FAR 23 and AC23 at the appropriate amendment status makes it difficult to follow all the investigatory work you did.
Not knowing the cert basis and not having access to FAR 23 and AC23 at the appropriate amendment status makes it difficult to follow all the investigatory work you did.
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Alan may correct me here but IIRC it was not a student but a three monthly check flight for a pilot qualified for night twin ops.
At the time student visual circuits could not be done at EN so ex EN usually done at MB
At the time student visual circuits could not be done at EN so ex EN usually done at MB
Last edited by Deaf; 22nd Aug 2017 at 14:18.
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Pilot Flying was rated NVMC and needed 3 take-off's and landings to remain current. EN required IFR for night circuits at that time so I acted PIC so P/F was AICUS. Essendon banned Night Circuits after the Partenavia went berserk. Geoff was a very responsible experienced PPL. I was there to save him from needing to fly to Mangalore to do his 3 circuits to remain current
"He did not operate the Trim Switch."
I believed him and so did the Coroner! I have no memory whatsoever of the Accident!
"He did not operate the Trim Switch."
I believed him and so did the Coroner! I have no memory whatsoever of the Accident!
Talking to another pilot about this thread, and he mentioned that some of the early Partenavias were a bit poor on quality control inspections in the factory. Didn't this one, have washers missing on the engine mount bolt's, and this was found during the accident investigation?
Wow what a thread. Certainly the first I have been in where one of the crew has posted about their experience.
6317alan, a question for you if I may - how hard was it to get back in the air after the accident? Have you ever felt vindicated? Can you remember anything at all from the flight?
6317alan, a question for you if I may - how hard was it to get back in the air after the accident? Have you ever felt vindicated? Can you remember anything at all from the flight?
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Magnum PI, Answers to your questions, I have absolutely No memory for a fortnight after the crash although I got all the questions correct on admission form at Royal Melbourne Hospital, so therefore I had no problems other than the Medical branch creating problems after I had repassed a Medical in getting back into the air. No memory has ever returned! "Natures way of looking after me I Guess"
I have been very much been vindicated after the accident by Geoff who was medically U/S a little longer than I, and he can remember it vividly, He got me to check him out after his medical clearance, however I have never felt vindicated by the Department. They still try to push the Party Line with ATSB Report 1-79 as can be seen in the first post. The only way to stop this is to separate the accident investigation from the Regulator completely!
Alan
I have been very much been vindicated after the accident by Geoff who was medically U/S a little longer than I, and he can remember it vividly, He got me to check him out after his medical clearance, however I have never felt vindicated by the Department. They still try to push the Party Line with ATSB Report 1-79 as can be seen in the first post. The only way to stop this is to separate the accident investigation from the Regulator completely!
Alan
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Keen to read your report but the link doesn't work
Try now .. the site, as of a while ago, requires the attachment to be given a tick. As a consequence it might be a few hours until someone spots it and does the deed.
Try now .. the site, as of a while ago, requires the attachment to be given a tick. As a consequence it might be a few hours until someone spots it and does the deed.
6317alan
1. What was the diameter of the trim operating cable?
2. What was said about the statement in AC 23 (23.689(f)) that the maximum prolonged forces of FAR 23.143 are not applicable in a failure case and would be considered too low?
3. Were runaway tests carried out or simply control forces at full tab deflection?
Unfortunately without documents at the appropriate amendment status any attempt at following the saga is problematic.
1. What was the diameter of the trim operating cable?
2. What was said about the statement in AC 23 (23.689(f)) that the maximum prolonged forces of FAR 23.143 are not applicable in a failure case and would be considered too low?
3. Were runaway tests carried out or simply control forces at full tab deflection?
Unfortunately without documents at the appropriate amendment status any attempt at following the saga is problematic.
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My Partenavia Report
Partenavia P68B aircraft autopilot
and trim systems
Prepared by Alan C Baskett
introduction On the 10th July 1978 the Partenavia P68B VH-PNW crashed at Essendon Airport. The Dept in their Special Investigation Report 79-1 of March 1979 list the cause as:
Cause The cause of the accident was that the aircraft became grossly out of trim at a height, which did not permit time for the crew to affect recovery. The manner in which the out–of–trim con- dition occurred has not been determined and the possibility of a trim system malfunction cannot be eliminated, however the more likely explanation is that the command trim switch was activated unknowingly.
The coroner at the inquest because of the evidence could not accept the DEPT’s more likely explanation. The DEPT’s simplistic assessment of the cause of this accident
is an easy way of minimizing the underlying design deficiencies, which allowed the aircraft to “become grossly out-of-trim” and the DEPT’s mismanagement of its certification responsibilities by attempting to shift the cause of the accident to “pilot error” This report attempts to detail the history and modifications made to the trim tab travel range of the trim system and the auto- pilot/trim system and of the certification and approval of these modifications.
summary of events
23-1-75 First of Type Certification in Australia of P68b Air- craft (no autopilot fitted)
April/May Two P68B arrive in Australia with 1975 Autopilots fitted and no certification
23-5-75 The Dept. formally requests certification justification for Autopilot installation
12-6-75 R.A.I. Autopilot Approval No 124-245-T
1-8-75 to Edo-Aire Flight tested Autopilot 12-9-75 installation.
15-9-75 Edo-Aire issued S.T.C. no SA 3067SW-D for Auto- pilot/Electric Trim system installation
Sept. 75 Australian approval of Autopilot/Electric trim system installation
28-4-76 Partenavia produce Autopilot flight tests BM 82 and BM 83
20-7-76 VH-PNW registered in Australia with TTTR Number 2 fitted
23-11-76 TTTR Number 2 certified by FAA type data sheet A31 EU Revision 3
16-1-78 R.A.I. Certify TTTR Number 3 in RAI Type Data Sheet SO / A151 Revision 5
10-7-78 Date of the said Crash
October 78 S. B. 41 modification to TTTR Number 4
March 79 Special Investigation Report 79-1 published
17-2-89 The Dept. flight test P68B aircraft as per CAA docu- ment M131-515-4 and in doing so establish TTTR Number5
NOTE FAA is USA Federal Aviation Authority R.A.I. is the Italian Aviation Authority STC is an FAA Modification certification Meaning, Supplementary Type Certificate
Partenavia P68B aircraft and autopilot electric trim installation history
The original P68 aircraft and the P68B aircraft were both certified originally with a trim tab travel range of 36 degrees (TTTR No One) in fact this was the only trim tab travel range approved in Australia until the requirement for S.B. 41 became a mandatory modification late in 1978 after the said date. The first P68B aircraft arrived in Australia during 1974 after Forrestair entered into a distribution agreement with Partenavia. This aircraft received “First of Type” certification on 23-1-75 for Australian operation.
IT WAS NOT FITTED WITH AN AUTOPILOT/ELECTRIC TRIM SYSTEM!
During April/early May 1975 two aircraft arrived at Essendon after ferry flight from Italy, both these aircraft were fitted with Edo-Aire Century 111 Autopilot / Electric Trim Systems. During the regis- tration/certification process the Dept. noted the autopilot installa- tion and requested the Reg .27 justification for these non-approved modifications. This justification was first sought verbally and then in writing from the Dept. to Partenavia on the 23-5-75. In the mean- time Forrestair were required to disconnect and disable the autopilot installations in these aircraft, leaving Forrestair with two aircraft paid for by them but unable to deliver to their customer and receive payment for until completion of the autopilot installation. Partenavia obtained Italian certification from the R. A. I. for the Autopilot/Electric trim system installation, RAI approval No 124, 245 / T on the 12-6-75 more than a month after the two aircraft had arrived in Australia after the ferry flight from Italy.
I am unaware of any flight test data or any justification for the Italian certification of the Autopilot/Electric trim system being sub- mitted to the RAI for this certification. (None was produced during legal discovery for the litigation by Partenavia to me and this was the process where Partenavia were legally required to produce all documents that we had requested.) Italian certification of the Autopilot/ Electric trim system would have been a prerequisite for testing to obtain American S.T.C. approval of this modification. I suspect that Edo-Aire were probably mislead into a false sense of security when conducting the flight tests for the STC issue as the aircraft had already obtained Italian certification. Partenavia may have lead Edo-aire into believing that aft C of G may have been the critical condition to be tested as it appears that this is the only condition that results appear to be satisfactory can obtained. Edo-aire document A75-66SW-DAS is incomplete, inadequate, superficial and misleading for the following reasons:
1; The section of the FAA Flight Test Report Guide Form 8110- 18(6.75) dated June 1975 on pages 69 and 70 referring to Electric Trim System including flight tests have not been reported on.
2; The only flight tests conducted at forward C of G position were function tests only
3; Autopilot malfunction and trim runaway tests were all con- ducted at aft C of G position only (This is not a normal operating condition for the P68B aircraft as even at all up weight the C of G position is normally towards the forward limit. VH-PNW was oper- ating at a weight only 57 kg below the maximum allowable operating weight and at a C of G position only six percent aft of the forward position of the total allowable on the night of the accident.
4; Trim runaway tests were not conducted hands free but “Stick force observations were made without allowing an aircraft or air- speed change to occur”
5; Trim runaway tests were not conducted in takeoff or climb configurations
6; Trim runaway tests were not conducted to determine if a temporary force of 50 pounds (22.65kg) on the elevator control was exceeded when corrective action is not initiated until the mal- function is detected by the pilot for the following time delays and conditions of flight:
Takeoff, climb, approach & landing 2 seconds Cruise 4 seconds
7; The most critical weight and C of G condition was not deter- mined and used for trim runaway tests. However the FAA- STC No SA 3067 SW-D was issued by Edo-aire on the 15-9-75. The Australian Dept. then approved the Autopilot / Electric trim system modification to the P68B for use in Australia even though they did not then or even now receive any flight test data from Partenavia to justify this Australian certification as required by ANO 101-22-7.3(6) They do not even have a copy of the S.T.C. The Dept. did not require Partenavia to submit any evidence “relating to the design to which the application relates including evidence of the effect of the design on safety of an aircraft” as
required by A.N.R. 40 ( 1 ) ( 2 ) The Dept. had previously recognized that the possibilities of problems occurring with aircraft designed and manufactured in counties other than the USA or the UK as they had included in ANO 101-22.1.2 “The Director-General may specify additional design stand- ards, documents and other evidence for aircraft types other than those designed in the United Stares of America or the United Kingdom.” I have not been able to discover any such additional require- ments being made for the certification of the P68B or its modification by installing the Autopilot / Electric trim system. In fact when one departmental officer suggested additional flight tests for the first of type certification, he was informed that under no circumstances would this be required (copy of departmental memo held) nor was any additional requirement made for the certification of the Autopilot / Electric trim system. In fact the reverse is the case as the Autopilot /Electric trim system was certified with the requirements being less than that required by the statuary standards. So the Autopilot /Electric trim system was certified in Australia. Partenavia produced flight tests numbered BM82 and BM83. These tests are dated 28-4-76 and are similar in nature to Edo-Aire flight tests. BM 82 and BM 83 and Edo-Aire document A75-66SW-DAS are all documents applicable to the Autopilot / Electric system installation certification none of which are in possession of the department. During April 1976 Forrestair took delivery of VH PNW. This aircraft Partenavia claim and the wreckage reconstruction would support this claim, was fitted with trim tab travel range number two of 28° This TTTR not certified in Australia and the change was not noticed during the certification process by the department and nor was it noted during subsequent maintenance by Forrestair or Phil White (Aircraft Maintenance Engineer). The only certification details of this change to TTTR 2 is included in. FAA types certifi- cate Data Sheet A31EU Revision 3 dated 23/11/76 more than six months after installation in VH-PNW. No justification have been discovered to myself or to the depart- ment and for this modification. A further modification of the trim tab travel range (TTTR number three) was approved by the R.A.I. on the 16th of the first 1978 in R.A.I. type certification data sheet SO/A151 revision five. This reduced trim tab travel range to 24° Again this modification has no design justification or flight tests discovered by Partenavia to myself, nor were any submitted to the Department Partenavia were either unaware, and, are unable or unwilling to notify certification authorities of changes to the P68 b design status and obtaining approval before incorporation into production aircraft. These modifications to the Trim Tab Travel range from 36° to 28° indicate that Partenavia were aware that a problems existed in the trim system Perhaps the events of the 10th of July 78, may have been averted at the modifications to 24° total travel had been incorporated into Australian aircraft as this reduced the nose-down trim capability by 54% from a total excess on over 140% to only 86% of excess capabilities. After the crash of VH-PNW on the 10th July 1978, Partenavia issued Service Bulletin 41 during October 1978, which changed trim tab travel range (TTTR number four) to 14° and again Partenavia have not discovered to me any design justification or flight tests to support this modification. Neither have they provided any design justification or flight tests to the Department The departments CAA report M131-515-4, I submit is the only fight test report that is available even though it would not produced until early 1989, that one is able to establish the actual trim tab travel required for the Partenavia. Even though its purpose was to determine the P 68.B’s compliance with F.A.A.23-689 (f) In doing this the Department has established the trim tab travel requirements for the P68B. By logical conversion as detailed in TTTR number 5, it can be determined that only 7 ½ degrees of total trim travel is required for the aircrafts safe operation.
MTF AB
Partenavia P68B aircraft autopilot
and trim systems
Prepared by Alan C Baskett
introduction On the 10th July 1978 the Partenavia P68B VH-PNW crashed at Essendon Airport. The Dept in their Special Investigation Report 79-1 of March 1979 list the cause as:
Cause The cause of the accident was that the aircraft became grossly out of trim at a height, which did not permit time for the crew to affect recovery. The manner in which the out–of–trim con- dition occurred has not been determined and the possibility of a trim system malfunction cannot be eliminated, however the more likely explanation is that the command trim switch was activated unknowingly.
The coroner at the inquest because of the evidence could not accept the DEPT’s more likely explanation. The DEPT’s simplistic assessment of the cause of this accident
is an easy way of minimizing the underlying design deficiencies, which allowed the aircraft to “become grossly out-of-trim” and the DEPT’s mismanagement of its certification responsibilities by attempting to shift the cause of the accident to “pilot error” This report attempts to detail the history and modifications made to the trim tab travel range of the trim system and the auto- pilot/trim system and of the certification and approval of these modifications.
summary of events
23-1-75 First of Type Certification in Australia of P68b Air- craft (no autopilot fitted)
April/May Two P68B arrive in Australia with 1975 Autopilots fitted and no certification
23-5-75 The Dept. formally requests certification justification for Autopilot installation
12-6-75 R.A.I. Autopilot Approval No 124-245-T
1-8-75 to Edo-Aire Flight tested Autopilot 12-9-75 installation.
15-9-75 Edo-Aire issued S.T.C. no SA 3067SW-D for Auto- pilot/Electric Trim system installation
Sept. 75 Australian approval of Autopilot/Electric trim system installation
28-4-76 Partenavia produce Autopilot flight tests BM 82 and BM 83
20-7-76 VH-PNW registered in Australia with TTTR Number 2 fitted
23-11-76 TTTR Number 2 certified by FAA type data sheet A31 EU Revision 3
16-1-78 R.A.I. Certify TTTR Number 3 in RAI Type Data Sheet SO / A151 Revision 5
10-7-78 Date of the said Crash
October 78 S. B. 41 modification to TTTR Number 4
March 79 Special Investigation Report 79-1 published
17-2-89 The Dept. flight test P68B aircraft as per CAA docu- ment M131-515-4 and in doing so establish TTTR Number5
NOTE FAA is USA Federal Aviation Authority R.A.I. is the Italian Aviation Authority STC is an FAA Modification certification Meaning, Supplementary Type Certificate
Partenavia P68B aircraft and autopilot electric trim installation history
The original P68 aircraft and the P68B aircraft were both certified originally with a trim tab travel range of 36 degrees (TTTR No One) in fact this was the only trim tab travel range approved in Australia until the requirement for S.B. 41 became a mandatory modification late in 1978 after the said date. The first P68B aircraft arrived in Australia during 1974 after Forrestair entered into a distribution agreement with Partenavia. This aircraft received “First of Type” certification on 23-1-75 for Australian operation.
IT WAS NOT FITTED WITH AN AUTOPILOT/ELECTRIC TRIM SYSTEM!
During April/early May 1975 two aircraft arrived at Essendon after ferry flight from Italy, both these aircraft were fitted with Edo-Aire Century 111 Autopilot / Electric Trim Systems. During the regis- tration/certification process the Dept. noted the autopilot installa- tion and requested the Reg .27 justification for these non-approved modifications. This justification was first sought verbally and then in writing from the Dept. to Partenavia on the 23-5-75. In the mean- time Forrestair were required to disconnect and disable the autopilot installations in these aircraft, leaving Forrestair with two aircraft paid for by them but unable to deliver to their customer and receive payment for until completion of the autopilot installation. Partenavia obtained Italian certification from the R. A. I. for the Autopilot/Electric trim system installation, RAI approval No 124, 245 / T on the 12-6-75 more than a month after the two aircraft had arrived in Australia after the ferry flight from Italy.
I am unaware of any flight test data or any justification for the Italian certification of the Autopilot/Electric trim system being sub- mitted to the RAI for this certification. (None was produced during legal discovery for the litigation by Partenavia to me and this was the process where Partenavia were legally required to produce all documents that we had requested.) Italian certification of the Autopilot/ Electric trim system would have been a prerequisite for testing to obtain American S.T.C. approval of this modification. I suspect that Edo-Aire were probably mislead into a false sense of security when conducting the flight tests for the STC issue as the aircraft had already obtained Italian certification. Partenavia may have lead Edo-aire into believing that aft C of G may have been the critical condition to be tested as it appears that this is the only condition that results appear to be satisfactory can obtained. Edo-aire document A75-66SW-DAS is incomplete, inadequate, superficial and misleading for the following reasons:
1; The section of the FAA Flight Test Report Guide Form 8110- 18(6.75) dated June 1975 on pages 69 and 70 referring to Electric Trim System including flight tests have not been reported on.
2; The only flight tests conducted at forward C of G position were function tests only
3; Autopilot malfunction and trim runaway tests were all con- ducted at aft C of G position only (This is not a normal operating condition for the P68B aircraft as even at all up weight the C of G position is normally towards the forward limit. VH-PNW was oper- ating at a weight only 57 kg below the maximum allowable operating weight and at a C of G position only six percent aft of the forward position of the total allowable on the night of the accident.
4; Trim runaway tests were not conducted hands free but “Stick force observations were made without allowing an aircraft or air- speed change to occur”
5; Trim runaway tests were not conducted in takeoff or climb configurations
6; Trim runaway tests were not conducted to determine if a temporary force of 50 pounds (22.65kg) on the elevator control was exceeded when corrective action is not initiated until the mal- function is detected by the pilot for the following time delays and conditions of flight:
Takeoff, climb, approach & landing 2 seconds Cruise 4 seconds
7; The most critical weight and C of G condition was not deter- mined and used for trim runaway tests. However the FAA- STC No SA 3067 SW-D was issued by Edo-aire on the 15-9-75. The Australian Dept. then approved the Autopilot / Electric trim system modification to the P68B for use in Australia even though they did not then or even now receive any flight test data from Partenavia to justify this Australian certification as required by ANO 101-22-7.3(6) They do not even have a copy of the S.T.C. The Dept. did not require Partenavia to submit any evidence “relating to the design to which the application relates including evidence of the effect of the design on safety of an aircraft” as
required by A.N.R. 40 ( 1 ) ( 2 ) The Dept. had previously recognized that the possibilities of problems occurring with aircraft designed and manufactured in counties other than the USA or the UK as they had included in ANO 101-22.1.2 “The Director-General may specify additional design stand- ards, documents and other evidence for aircraft types other than those designed in the United Stares of America or the United Kingdom.” I have not been able to discover any such additional require- ments being made for the certification of the P68B or its modification by installing the Autopilot / Electric trim system. In fact when one departmental officer suggested additional flight tests for the first of type certification, he was informed that under no circumstances would this be required (copy of departmental memo held) nor was any additional requirement made for the certification of the Autopilot / Electric trim system. In fact the reverse is the case as the Autopilot /Electric trim system was certified with the requirements being less than that required by the statuary standards. So the Autopilot /Electric trim system was certified in Australia. Partenavia produced flight tests numbered BM82 and BM83. These tests are dated 28-4-76 and are similar in nature to Edo-Aire flight tests. BM 82 and BM 83 and Edo-Aire document A75-66SW-DAS are all documents applicable to the Autopilot / Electric system installation certification none of which are in possession of the department. During April 1976 Forrestair took delivery of VH PNW. This aircraft Partenavia claim and the wreckage reconstruction would support this claim, was fitted with trim tab travel range number two of 28° This TTTR not certified in Australia and the change was not noticed during the certification process by the department and nor was it noted during subsequent maintenance by Forrestair or Phil White (Aircraft Maintenance Engineer). The only certification details of this change to TTTR 2 is included in. FAA types certifi- cate Data Sheet A31EU Revision 3 dated 23/11/76 more than six months after installation in VH-PNW. No justification have been discovered to myself or to the depart- ment and for this modification. A further modification of the trim tab travel range (TTTR number three) was approved by the R.A.I. on the 16th of the first 1978 in R.A.I. type certification data sheet SO/A151 revision five. This reduced trim tab travel range to 24° Again this modification has no design justification or flight tests discovered by Partenavia to myself, nor were any submitted to the Department Partenavia were either unaware, and, are unable or unwilling to notify certification authorities of changes to the P68 b design status and obtaining approval before incorporation into production aircraft. These modifications to the Trim Tab Travel range from 36° to 28° indicate that Partenavia were aware that a problems existed in the trim system Perhaps the events of the 10th of July 78, may have been averted at the modifications to 24° total travel had been incorporated into Australian aircraft as this reduced the nose-down trim capability by 54% from a total excess on over 140% to only 86% of excess capabilities. After the crash of VH-PNW on the 10th July 1978, Partenavia issued Service Bulletin 41 during October 1978, which changed trim tab travel range (TTTR number four) to 14° and again Partenavia have not discovered to me any design justification or flight tests to support this modification. Neither have they provided any design justification or flight tests to the Department The departments CAA report M131-515-4, I submit is the only fight test report that is available even though it would not produced until early 1989, that one is able to establish the actual trim tab travel required for the Partenavia. Even though its purpose was to determine the P 68.B’s compliance with F.A.A.23-689 (f) In doing this the Department has established the trim tab travel requirements for the P68B. By logical conversion as detailed in TTTR number 5, it can be determined that only 7 ½ degrees of total trim travel is required for the aircrafts safe operation.
MTF AB