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July 2015

FIXED WING 

Britten Norman BN2T: Allison 250: Lee-on Solent  - 29/06/2015 (201509389)

During the 300 hr inspection on the Port Engine, a crack was identified in the Trailing Edge of a vane on the Compressor Front Support. This was reported to engine manufacturer. The defective part is to be replaced. 

Cessna 406: P & W PT6: Blackpool - 16/07/2015  (201509604)

During scheduled maintenance a physical check of the fuel system was being carried out. The fuel firewall shut-off valves to both engines were tested with correct annunciations noted on the instrument display. However, fuel was still found to be pumping to the engines with both valves in the OFF position with the fuel boost pumps operating.  The right hand fuel shut-off valve was removed for visual/test inspection.  The valve mechanism appeared to operate in the correct manner though fuel was still allowed to by-pass the valve, thus appearing to be either physical wear of the internal valve mechanism, no full closure of the valve or a manufacturing defect.  The same test was carried out on the left-hand shut off valve with the same fuel by-pass occurring.  The Operator, and CAMO of the aircraft were immediately notified and requested to contact the TC holder for the aircraft, for clarification on the expected condition and operational requirements regarding the shut-off valves. Repeat tests on A/C were carried out with the fuel output pipe disconnected and functioning of the shut-off valves in a pressure "ON" state.  After several functions the fuel output decreased and then stopped.  The fuel shut-off valves then continued to function correctly at every function test.  The fuel system was reconnected, leak tested and certified as serviceable.   As the fuel firewall shut-off check is a function check of the cabin switch and display there is no fuel pressure application required. It has to be assumed that the valves had become partially "gummed up" allowing fuel to initially seep past the mechanism and that the function of fuel being passed through valve had then removed the deposits that had caused the valve to stick.  It has been recommended to the operator that the valves be functioned with the fuel pipe disconnected to allow fuel to pass through the valve on future schedule maintenance inputs.  This is a non-complex but safety critical task and will require a secondary leak test inspection by a competent person. 

The test was performed on a second aircraft revealed the same problem (Occurrence Number 201509608 dated 17/07/2015).   

Cessna 406: P & W PT6: East  Midlands: 18/07/2015  (201509912)

Right hand P1 rudder pedal became detached during flight.  Rudder out of trim, rudder pedal gave way and fell to the backstop. A/C returned safely to base. 

Grob 115: Lycoming O-360: St Athan 09/04/2015 (201508649)

During a training flight the instructor turned the fuel pump off and shortly after, both crew members heard a very unusual intermittent loud squeal from the engine compartment which got progressively louder. The Instructor turned the aircraft whilst trying to diagnose the problem. All of the engine indications were normal and there were no external indications of any problems either. The squeal stopped after approximately 5 mins. During this period the crew had declared a PAN and routed overhead for a precautionary, forced landing.  Upon selecting the electric fuel pump back on during the pre-landing checks, the squeal started again. The Instructor elected to leave the pump off during the precautionary forced landing.  The aircraft was landed safely.  An electric fuel pump failure was later found to be the cause of the issue 

Piper PA31: Lycoming O-540 family: Northolt - 08/07/2015 (201509290)

After an uneventful landing and aircraft had slowed to a walking pace, both throttle levers were advanced from idle to set 1000 Prop RPM.  However the RH Prop loitered at around 600 RPM even with increasing throttle before the engine eventually stopped after approx 5 -10 seconds.  It was noted that the RH propeller had feathered.  ATC where informed and the aircraft was taxied to the line.  Once on stand, ground crew indicated that liquid was "hosing" from the RH engine upon which the pilot expediently shutdown.  Fuel was observed pouring from the foremost drain of the RH engine cowl creating a large pool on the ground, all RH engine quick release cowl doors were opened to cool the engine and Fire Crew were called as a precautionary measure.  The propeller governor had just been replaced less than 1 flight hour before the incident with an overhauled (zero time) governor.  Due to the recent replacement the governor was suspected to be the cause for allowing the propeller to feather. The newly overhauled governor was subsequently replaced with a Serviceable "in service" unit removed from another type from the customers fleet.  Full ground runs including various idle to full power range checks, engine stop/start were carried out to try to replicate the incident.  As we were unable to replicate the incident during any of the ground runs, it was determined that the probable cause was the newly overhauled governor. The subject governor will be returned to the overhaul facility in the US for investigation and report on their findings. The excess fuel draining from the engine sump drain is explained by the electric fuel boost pump being selected during/after landing, then as the throttles were advanced the fuel would be pumped under high pressure into the cylinders causing fuel rich cylinders draining down into the induction and out through the sump drain. The fuel rich cylinders would be the probable cause for the engine stopping after the throttles were advanced. Whilst we feel that the Part145 has correctly identifies the root cause there are a number of issues we would like to investigate further. Therefore, we will keep this report open and update accordingly.  (GASCo Comment: has anyone else experienced a similar event?)  

Piper PA31: Lycoming O-540 family: Sywell - 21/07/2015 (201509911)
During the replacement of a propeller governor, it was noted that the current one fitted was a different part number. The one already fitted was incorrect.  Fleet check conducted. three out of 10 aircraft had incorrect Governors.  (GASCo Comment:  we do not know if there is any connection between the above two events).   

SOCATA Rallye 150: Lycoming O-320: Welshpool - 11/07/2015 (201509444)

Following a flight of 50 minutes the pilot was given a crosswind of SW 8 kts.   The approach was a little bumpy with the aircraft crabbing to the right.  As the pilot crossed over the numbers he straightened the aircraft with the rudder, flared, had a slight ballooning effect and touched down gently.  On touch down there was a vibration coming from the front which was much more than normal from the caster wheel so applied a little back pressure but the vibration continued and he thought he had a nose wheel puncture as it became spongy so applied more back pressure.  The vibration then turned to a metal sound on the runway and the aircraft started to pull to the right of the runway, so he pulled the stick as far back as possible. The aircraft came to rest in the grass approx 25m from the runway.   The pilot called Radio to say that I had come off the runway and shut the engine down,  and turned off all electrics. He opened the canopy and told my passengers to get out.  Upon inspection of the nose wheel, the split rim had broken near to where it bolts to the other half of the rim by the bolt's.  A small amount of corrosion can be seen where it has cracked, the tyre was found to the left of the aircraft with the inner tube still full and at pressure. No marks are on the side wall or the face of the tyre.  

SOCATA TB10  Tobago: Lycoming O-360: Rochester: 15/07/2015 (201510232)

The tail cone detached in flight.  The aircraft had undergone a six-monthly airworthiness check 11 flying hours before the incident.  The pilots had not noticed any defect in their pre-flight checks. The tail cone is secured with 7 self-tapping screws into brackets attached to the main fuselage. The part was recovered one week later from a garden in the area.  It is believed that one of the self-tapping screws may have worked loose, allowing airflow behind the panel. This would have caused vibration and stress to further securing screws. During the course of the flight, this caused a part of the tail cone to shear around one mounting point. The remainder of the securing crews were pulled from their retaining clips and the tail cone detached from the fuselage. The pilots remarked no change in the performance of the aircraft. The part has been inspected and a report is expected regarding the possible repair and replacement. It is expected that the mounting points will all need to be reinforced and the securing mechanism reviewed to ensure that the mounting screws do not work loose in the future.

SINGLE ENGINED ROTARY WING 

Bell 206: Allison 250: Mulberry House - 30/06/2015 (201508858)

During the post-flight walk round the stbd exhaust was inspected and found to be cracked with a triangular piece missing.  Engineering support was called and aircraft grounded till further inspection which did not reveal any debris.  Exhaust was replaced and flight continued next day. 

Robinson R22: Lycoming O-360: Rochester: 15/07/2015 (201509493)

During initial climb-out for a PPL (H) Skills Test, the Examiner noticed tacho indications as 104% ERPM, 107 -108% RRPM. (RRPM should match ERPM in powered flight).  Examiner took control, and confirmed it was not due to governor being over-ridden by candidate.  The Skills Test was suspended, ATC informed, and aircraft positioned to a close downwind leg prior to a short final approach and landing.  The abnormal RRPM indications persisted until landing and shutdown.  However, the RRPM sounded as 'normal'.  ERPM indications and governor function normal throughout.  During engine cool-down prior to shutdown, the RRPM indication failed completely.  RRPM Circuit breaker cycled and re-set: to no avail.



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