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February 2015

FIXED WING 

Cessna T303: Continental O-520 - Cranfield - 18/02/2015 (201502059)

The aircraft was undergoing a prolonged Annual Inspection, which revealed the L/H Main Landing Gear retraction arm (P/N:2541080-1) was cracking at the point where it touches the lower retract arm linkage (P/N: 2541099-1). Investigation showed that the lower retract arm linkage had been assembled 180 deg. out during the last strip inspection. Further inspection of the R/H Main Landing Gear retraction system showed the same issue with the lower retract arm also installed incorrectly. The L/H Main Landing Gear shock strut was dismantled due to leakage. On inspection it was seen that the Cap Assy (P/N: 2541064-3) was not fully screwed into the Oleo Lower Strut Barrel (P/N: 2541059-1). This aircraft has previously undergone a full Supplemental Inspection Document (SID) in April 2013 by another Maintenance Organisation, at which time a full strip inspection of the landing gear was certified.

SINGLE ENGINED ROTARY WING  

Robinson R22: Lycoming O-320F - Blackpool  - 16/02/2015 (201501872)

During a scheduled 100 hour inspection, it was noted that the nut securing the Tail Rotor Gearbox to the Tail Cone was cracked.  Tail Rotor Gearbox mounting nut P/N MS21042L4 replaced. Tail rotor dynamic balance to be carried out. 

Robinson R44: Lycoming O-540 - Lashenden/Headcorn - 12/02/2015 (201501795)

The day before the incident a pilot reported odd behaviour of the Governor in that it was occasionally overly aggressive with the throttle and it was feared that this might lead to a Governor runaway resulting in an engine and rotor overspeed.  As the Head of Training the reporter elected to fly a test circuit with the pilot in question to experience the effect himself.  The initial start-up and lift into the hover was normal but it was only when they started the transition that he noticed the governor working rather harder and more aggressively than normal but he was closely monitoring it at the time so we continued the climb past about 100 feet when he decided that iut would be more comfortable switching off the governor and electing to control the throttle manually.  At this point he noticed that in order to climb at all he had to reduce the speed to about 50 knots and also had to manually open the throttle to maintain RPM which resulted in a Manifold Pressure reading close to 24.5 inches with a rate of climb of barely 100 feet per minute.  He felt there was a serious power problem and immediately turned the aircraft and commenced a descent back to the threshold of Runway 10 declaring to ATC that they had a problem requiring an immediate return to the field.  The descent required much more power than normal (about 22 inches of manifold pressure).  They managed to hover taxi back to the pad by pulling 25 inches of MP which resulted in an IGE hover taxi at about 6 inches to a foot.  The aircraft was shut down having checked both magnetos and discovered no drop beyond what is acceptable.  He then called their maintenance organisation British International Helicopters, having told them that they either had some sort of fuel problem or power problem.  It appears that the felt gasket had become unstuck from the air filter and was been ingested into the carburettor venture resulting ¡n an excessively rich mixture causing a massive loss in power. The reporter  was very glad that he made the early decision to turn back as he suspects the engine could well have stopped within a minute or two thereafter.  They find it incredible that these air filters have been approved when it appear that AVGAS attacks the glue that is used to stick the gaskets onto them.  Therefore as a matter of urgency all these aircraft types should be checked and the filters changed to the one’s made of moulded rubber gasket.  It is a useful check to squeeze the top and the bottom of the air boxes, if one feels movement then it is likely that a gasket has become dislodged and could well be about to be ingested.

Supplementary 23/02/15:
Aircraft arrived for the overhaul of the magnetos.  During the maintenance check flight post replacement of the magnetos, the pilot reported fluctuations in engine power, possibly governor issues.  They inspected the magnetos, replaced the magneto contact breaker.  On the subsequent check flight, and the flight back performed by the operator, all seemed well.  Further power loss/fluctuations came to light, a check of the airfilter was made in accordance with SB, and it was found that the air filter seal had detached itself from the airfilter and had migrated into the carburettor venturi area, which was clearly causing some kind of obstruction causing the power fluctuations.  They are currently checking other aircraft in the fleet which may have the subject air filter fitted.  The air filter was last replaced by Robinson at 1,258.7 hrs during the 2,200hr overhaul performed at the factory.  No maintenance has been performed in or around the air filter since then. 

Robinson R44: Lycoming O-540 - Blackpool  - 16/02/2015 (201501855)

Tail cone and Tail Rotor Drive Shaft removed for further investigation and to facilitate repair. The broken section of the plate was not present in the tail cone.  D072-3 plate replaced.  Tail rotor drive shaft damper bearing inspected iaw MM Fig 28. Following discussion with aircraft manufacturer, Rotor overspeed inspection to be carried out and Tail Rotor Drive Shaft damper bearing support arm friction to be checked and adjusted.

 

 



 

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