Graeme Duckworth is the managing director of Execujet Maintenance at Lanseria Airport in South Africa
Test Kits used
ALS Chemex – WearCheck Australia
WearCheck Canada Inc.
WearCheck South Africa.
Aviation maintenance recommends filter analysis
Execujet Maintenance based at Lanseria Airport strongly recommends that oil and filter analysis forms part of every aircraft’s maintenance programme. SOAP (Spectrometric Oil Analysis Programme) tests, although required by the manufacturer on TFE731 engines, are not compulsory for TPE331 engines.
‘Because 331 engines tend to fret more than 731 engines, we encourage operators to conduct SOAP tests every 100 hours on these engines. This can be extended to every 150 hours on a 731,’ says Graeme Duckworth, managing director of Execujet Maintenance which services jets for a number of major corporates, airlines and government departments in South Africa and further afield. The company is the accredited agent for Garrett jet engines in Africa.
Since Wearcheck was appointed as the official oil analysis company for Garrett jet engines in Africa, filters and samples processed by Execujet are now sent to Wearcheck instead of to Garrett field service offices in Germany or to Allied Signal headquarters in the USA as they were in the past.
‘This ensures a far quicker turnaround and is much more convenient for us,’ says Graeme. ‘Being close by, Wearcheck is also able to offer a more personalised service and go out of their way to speed up urgent samples. There have been a number of occasions when they have gone that extra mile in critical situations.’
After Execujet repairs an engine, they test it, then send the filter and oil samples to Wearcheck for analysis. Execujet then recommends that the aircraft owner repeats the sampling process after 25 – 50 hours.
‘When one considers that it costs between $200 000 and $300 000 to replace an engine, any preventive maintenance measures must be cost-effective,’ says Graeme. ‘In our opinion, filter analysis is a necessity rather than a luxury.’
Graeme cites a number of instances where filter analysis has helped save thousands of rands in replacement costs.
Case study 1
- SOAP samples detect wear on torque load arms. Regular SOAP samples saved the day when filter analysis revealed that torque load arms were wearing on a twin turbo prop engine in a 35-seater commercial aircraft in central Africa. WearCheck had been detecting a gradual increase in the number and size of abnormal wear particles in the filters over a four month period.
‘Although the oil samples were clean initially, we were concerned by the increasing weight and mass of the debris in the filter as well as by the size and shape of the particles,’ says Wearcheck technical director, Gary Brown.
Then, when major fine wear from carbon steel was found in the oil sample along with minor amounts of stainless steel, magnesium, carbon, grit and fibre in the filter, Wearcheck, in conjunction with the Garrett representative, recommended a thorough investigation.
With Garrett’s backing the aircraft was grounded and the engine was air freighted to Execujet who stripped the gearbox and aft turbine bearing to replace the torque load arms.
‘This procedure cost the owner about R 120 000 in repairs,’ says Graeme. ‘ The cost could have doubled if the problem had not been detected early and further damage had occurred. The worst case scenario – a failure in flight – would have had dire consequences.’
Case study 2
- Early treatment of corrosion saves money.On a TP331 engine Wearcheck’s filter analysis showed magnesium corrosion, highlighting a problem in the gearbox as the input housing is made of magnesium. On inspection it was found that moisture was getting into the gearbox, probably when the aircraft was standing, and a small corroded patch was cleaned and treated for under R 10 000. If the problem had not been identified timeously and left for any length of time, it could have resulted in corroded bearings which would have meant repair costs of up to R 200 000.