.
installation of improved engine oil seals; and

.
changed Auxiliary Power Unit air switching procedures.57

4.58 Captain John Siebert of NJS told the Committee on 1 February 2000:
To update the committee on the progress of our efforts to improve the quality of the cabin air in the 146, I can report that all of the engines have now been modified with new and improved bearing oil seals. Modifications are being incorporated into the distribution pipes, which will improve the cabin air circulation patterns. Those are the pipes that I understand the senators had a look at in Brisbane. They are exactly the same as the ones going into our fleet. These modifications are part of an ongoing process that applies to all areas of the aircraft. Operating procedures have been adjusted so that descents are flown with engine thrust levels at above flight idle. In addition, the APU air supply is selected at a late stage during the approach to landing. Both of these measures have proved to be quite beneficial.
A major leap forward in the reliability of the engine oil seals can be identified as a result of the Allied Signal, which is now Honeywell, XRP extended reliability program for the engines, and the decision by NJS to send the engines back to the manufacturer’s Phoenix Arizona facility for all the overhauls. During the overhauls all of the bearing oil seals are replaced by new parts rather than being reinstalled after the existing seals have been inspected.58
4.59 On 13 March 2000 during a public hearing in Canberra Mr Toller of CASA advised the inquiry:
National Jet Systems have a total of 21 aircraft. I think they probably had 20 before. … Only four of those aircraft have been modified for the aircraft modifications (sic). However, our information on the engine modifications is that they only have four engines that remain to be modified. I think there is only one APU in National Jet that is outstanding. That is the latest information that we have been given. National Jet are talking about the aircraft modification being complete by mid-2001, so they appear to be about nine months behind Ansett on the completion of modification.59
56  Ansett Pilots Association, Evidence, 2 February 2000, p 165 
57  Submission 23, NJS, p 1; see also Qantas, Evidence, 1 February 2000, pp 126 - 130 
58  NJS, Evidence, 1 February 2000, p 134 

4.60 On 10 April 2000 Captain Siebert told the inquiry, “NJS modifications to the auxiliary power units and the engines are substantially complete and, indeed, they are well ahead of other operators of this type of air craft.”60
4.61 On 2 February 2000, Captain Frank Kolver, a First Officer with National Jet Systems became the first pilot to give evidence publicly on the fumes issue. Captain Kolver told the Committee:
… I was certainly pleased to see that each time we reported oil fumes our company went to considerable lengths to rectify the problem. As I said before, many engine changes had been done at considerable cost to the company. I know they are trying to improve the quality of the oil seal.61
　
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