John-

 

I answered this question on the LML about five years ago and, of course, few (if any) 320/360 pilots listened to the solution.

So, I will offer it one more time...

I first encountered the 'failure to retract' problem in April 2000, three years after first flight in my 320. I also quickly discovered that releasing pressure by opening a high pressure fitting would enable gear retraction, but ONLY that one time; the problem quickly reoccured. After several years of attempting to alleviate the problem by opening the free-fall valve after flight, kicking the tires, etc, etc, etc,  it made NO DIFFERENCE - Summer or Winter, night or day, hot or cold, the high pressure build-up and 'failure to retract' reoccured. I even went to the aggravitation of removing and returning the pump to Oildyne three times; the first two, they 'bench checked' it and said they could find no problem. The third time, I told them not to 'bench check' it, just REBUILD it! That corrected the problem for about TEN cycles.

In 2002, I concluded that the problem was a result of an internal design defect in the 1990's-era hydraulic pump (Oildyne wasn't going to admit it and then have 1,000+ pilots come at them at say 'OK, now give me a new pump')

I made the (correct) assumption that Oildyne had since recognized and corrected the problem. I 'bit the bullet' (kissed Oildyne's A$$) and ordered a new pump from Lancair for $900. (They're about $1,300. now).  I mounted the new pump on the side of the elevator pushrod tunnel behind the pilot's seat (where it should have been in the first place, in spite of the early 320 manual which had it behind the baggage bulkhead).

I was correct! The new pump has functioned flawlessly the past five years. It is SWEET, retracts the gear in three to four seconds and symmetrically each time.

 

Bill Rumburg

N403WR (Sonic Boom)