Cessna Aircraft Company 210M, VH-XAJ

Investigation number

199804715

Occurrence date

30/10/1998

Location

4 km S Gumadeer

Report release date

05/04/2001

Report status

Final

Investigation type

Occurrence Investigation

Investigation status

Completed

Occurrence category

Accident

Highest injury level

Serious

Safety Action Analysis Summary

Safety Action Statement

As a result of this occurrence, the Australian Transport Safety
Bureau issues the following safety advisory notice to the Civil
Aviation Safety Authority.

SAN20010046

The Civil Aviation Safety Authority should note the safety
deficiency identified during this investigation and consider
introducing methods to identify and record time in service of
piston engine cylinder heads particularly for those cylinder heads
utilised in passenger carrying operations.

The flight had progressed normally until the pilot reported the
rough-running engine and associated high-indicated cylinder head
temperature. The pilot could not determine the problem with the
engine and decided to conduct a forced landing. As the pilot was
seriously injured, the carriage of a portable ELT was ineffective
in that the able-bodied passengers could not locate it in the
aircraft.

The engine, while still within the overhaul period, had required
several previous cylinder changes due to cylinder head cracking.
The engine failure leading to the accident had also resulted from
cylinder head fatigue cracking due to overheating.

Overheating of the cylinder head could be attributed to several
factors.

The operation of the engine at a higher than normal operating
temperature. This is possible due to varying pilot engine operating
techniques over a number of flights. Only limited, and possibly
inaccurate, engine temperature information was available to any
pilot because of recorded defects with the cylinder head
temperature indicating system.
The ring-type cylinder head temperature sensor was fitted to
the number one cylinder head with the normal spark plug washer,
effectively reducing the spark plug length. This may have
contributed to a change in the normal combustion process, producing
localised overheating near the plug and altering the thermal
transfer within the cylinder. However, as this sensor was not
fitted to other cylinders, this would not have occurred on the
previous number four and number six cylinder failures.
The engine cooling baffles, being in poor condition, would have
been less efficient in providing cooling airflow to the cylinders.
The number one cylinder, being at the rear of the engine, would
have been more susceptible to overheating. The engine manufacturer
advises that poor baffling will have a significant effect on
cylinder lives.
The prior cracking and replacement of the number four and
number six cylinders indicates that the engine may have been
subjected to higher than normal operating temperatures or that the
cylinders had a reduced thermal cycle tolerance due to their age
and time in service. At the time of the accident, the failed number
one cylinder was seventeen years old.

CONCLUSIONS

The occurrence and subsequent occupant injuries were a result of
the failure of the number one cylinder through fatigue cracking and
the subsequent forced landing. Inaccurate cylinder head temperature
indications may have contributed to the failure of the
cylinder.

There are ongoing reported structural failures of piston engine
cylinders as documented in the CASA MDR and ATSB occurrence data.
Some of these failures have led to forced landings, which increases
the risk of injury to aircraft occupants.

Aircraft piston engines must be maintained in accordance with
CASA requirements and have their time in service history recorded
in the engine logbook. However, this is not the case for piston
engine cylinders, which are not required to have serial numbers for
maintenance history documentation.

This report also highlights the limitations of carrying a
portable ELT should the pilot become incapacitated and the need for
comprehensive passenger briefings on the location and use of
emergency equipment.

SAFETY DEFICIENCY

At present, there are no recommended or mandatory life
requirements for piston engine cylinders in Australia for aircraft
operated in any category of operation by either the piston engine
manufacturers or the Civil Aviation Safety Authority. There is also
no requirement for piston engine cylinders to be identified with
serial numbers to document their history and time in service.

The flight, using a Cessna 210 aircraft, had been arranged as a
charter after the scheduled regular public transport (RPT) service
aircraft had become unserviceable. Waiting passengers were advised
of the cancellation of the scheduled service and that limited
seating would be available on a charter flight. Five passengers
elected to take the charter flight using their previously purchased
tickets and the company agent briefed them on the changed status of
the flight.

Subsequently, while cruising at an altitude of 4,500 ft, the
pilot reported to Adelaide flight service that the engine was
running rough, that the engine cylinder head temperature (CHT)
indication had become very high and that she was attempting to
locate a clear area for a forced landing. The pilot landed the
aircraft in a cleared gravel pit. During the landing roll however,
the aircraft struck large mounds of gravel and was substantially
damaged. The pilot and several passengers sustained serious
injuries.

The aircraft came to rest upright, resting on the lower fuselage
and right wingtip, with the tricycle landing gear folded back under
the aircraft. The left wing was damaged with fuel escaping from the
wing fuel tank. The engine had separated from the airframe and came
to rest inverted in front of the wreckage.

The passengers evacuated the aircraft and assisted the
unconscious pilot from the cabin. Adelaide flight service arranged
for overflying aircraft to locate the accident aircraft and
coordinated a rescue team to be dispatched from Darwin. A
search-and-rescue (SAR) helicopter attended the scene and took the
occupants to Darwin for medical attention.

The aircraft carried a manually operated GME Electrophone MT310
portable emergency locator transmitter (ELT), however the
passengers were not aware of its location. Although the injured
pilot attempted to direct the passengers to the ELT in the
aircraft, the passengers were unable to locate it and as a result
the ELT was not activated.

Aircraft engine

The aircraft was fitted with a Teledyne-Continental IO-520-L
engine, serial number 567962, that had completed 734.5 hours since
being overhauled. The engine was removed to a suitable engine
maintenance facility for examination which revealed that the number
one cylinder head had cracked, resulting in the observed high
cylinder head temperature and rough running reported by the pilot.
The cylinder head, part number TM642320F, had 10/81 stamped on the
rocker boss, indicating that the cylinder head had been
manufactured in October 1981. The history of the cylinder head,
including the total time in service, could not be determined.

A detailed metallurgical examination of the cracked cylinder
head determined that the cylinder head had failed as a result of
fatigue cracking due to overheating (See Technical Analysis
Report).

The engine was fitted with a six-point cylinder head temperature
sensing system with a temperature sensor probe in the head of each
cylinder. However, this system was inoperative at the time of the
occurrence. A single, ring-type temperature sensor was fitted to
the number one cylinder lower spark plug, in addition to a standard
spark plug washer. Normally, a ring-type temperature sensor
replaces the spark plug washer. This sensor provided cylinder head
temperature information to the aircraft cylinder head temperature
gauge. A maintenance release entry, dated 27 September 1998, stated
"CHT guage drops to zero periodically".

The engine baffles, used to direct cooling airflow over the
engine cylinders, were in a generally poor condition with several
cracks, broken mounting rings and worn areas. In one place, a
baffle had been worn through by contact with an engine hose.

The engine had been overhauled on 18 August 1997 and fitted with
six overhauled cylinders. On 11 August 1998, the number four
cylinder head had failed because of cracking and was replaced. On
28 August 1998, the number six cylinder head had similarly failed
because of cracking and was replaced. On 14 October 1998, 16.4
flying hours before the accident, the engine had passed a cylinder
pressure leak check during routine maintenance.

Piston engine maintenance requirements

The Australian Civil Aviation Safety Authority (CASA)
airworthiness directive, AD/ENG/4 (Amdt 7), details continuing
airworthiness requirements for piston engines. That directive
requires piston engines, operated in charter operations, to be
overhauled in accordance with the engine manufacturer's
requirements or in accordance with an approved system of
maintenance. The directive also requires that the engine service
history be recorded in the engine logbook. The engine manufacturer,
Teledyne Continental Motors (TCM), does not specify retirement
lives for engine cylinders but advises that "at some point in
operating hours, generally very high, the aluminium cylinder head
will fatigue due to the cylinder pressure loads and temperatures."
TCM also advise that for cylinders in excess of two overhaul cycles
"past that, duty cycle and the nature of field repairs make it
difficult to project future life."

TCM also report that cylinder head life can be affected by any
detonation/preignition event during the cylinder life, and that hot
cylinder operation due to poor baffles or fuel mismanagement has a
significant effect. CASA's information brochure titled "Piston
Engine Cylinders" also recognises that those components have a
limited life and suggests that cylinders be replaced every second
or third engine overhaul. However, piston engine cylinders are not
required to have serial numbers and recorded life history in the
same manner as their parent engine.

Data review

A review of ATSB data covering the 10-year period January 1990
to December 1999 revealed that there had been over 60 reported
occurrences, including a number of forced landings, involving
piston engine cylinder head structural failures. Only one other
reported cylinder head failure during this period resulted in
occupant injuries. A review of the CASA major defect reporting
(MDR) system for the same period revealed that there had been about
250 reported piston engine cylinder head structural failures, an
average of approximately one failure every 2 weeks. The data only
records the proportion of cylinder failures that have been reported
through formal reporting procedures. Other cylinder head failures,
such as those detected during routine maintenance, are possibly not
represented.

Aircraft Details

Manufacturer

Cessna Aircraft Company

Model

210

Registration

VH-XAJ

Serial number

21062846

Operation type

Charter

Departure point

Maningrida, NT

Departure time

1300 hours CSuT

Destination

Darwin, NT

Damage

Substantial