Friday, July 1, 2011

Blue Stain Blues

Last Monday brought a sight no Cessna owner wants to see: a blue stain starting at the trailing edge of the left wing root, down the pilot's side door post and onto the fuselage. The classic signature of an AvGas leak - and probably a failed fuel cell.

So the airplane is in the shop. The left fuel cell has been drained (and the valuable 100LL is stored in drums (left) and will be returned to the new fuel cell using a filter-equipped pump).

N631S is a 1977 vintage Q-model Cessna 182. The adoption of the O-470U engine in 1977 triggered the change in model designation from 182P to 182Q. The '77s had 14 volt electrics and rubber fuel cells. The '78s went to 28 volt electrics and the '79s (last year for the Q's) went to a "wet wing" fuel system, eliminating the rubber fuel cells. There are two schools of thought on rubber fuel cells. On one hand, they inevitably require replacement. On the other hand, the "wet wing" design, if it ever does leak, can be very hard to fix. Also, in the event of a crash, it has been suggested that rubber bladders are less likely to burst than a wet-wing tank. (I am not aware of any definitive evidence supporting this.)

There on the table (left) sits N631S's removed fuel cell. The mechanics at Three Wing Flying Services opened up the wing, verified that none of the fittings or gaskets were causing the leak, and then extracted the old fuel cell. Once the cell was out of the bay, they cleaned out the gunk (a fuel leak makes a mess) and renewed the protective tape that covers all the pointy ends (rivets and such) that could put the new cell at hazard. Now we await the arrival of the replacement cell, due Tuesday.

After querying my knowledgeable friends at the Cessna Pilots Association about the best sources, I opted to purchase an overhauled fuel cell from Eagle Fuel Cells of Eagle River, WI. My options were: (1) have them overhaul my cell, for $395 to $425 and a three to four day turn-around; (2) purchase an overhauled cell outright for $550 with the option of selling them my failed cell for up to $100; (3) purchase a new cell for $950. Options 1 and 2 come with a 5 year warranty, while option 3 comes with a 10 year warranty. I chose option 2 for the quick turn-around and to keep the cost down.

Based on where the leaking fuel seemed to be collecting in the wing, the folks at Three Wing think there's a leak in the area of the "nipple" pictured at left. Nothing is visible - which is not, I'm told, uncommon.
The longevity of this fuel cell is a disappointment. The original cell installed by Cessna in the spring of 1977 lasted until late 1989 - 12 years 8 months. The second cell lasted 13 years 3 months, until February 2003. This one only lasted 8 years 4 months.

Other 182 owners have told me that the manufacturer of this cell had "quality issues" in the early years of the last decade and that I am far from alone in getting less than the expected life out of cells manufactured during that period. The unpleasant message is that I can probably anticipate a need to renew the cell on the right side before too much longer.

For those interested, I'll update this post when I get the bill so you'll know the number of shop hours needed for removal and re-installation. And, of course, this weekend's trip to the DC area and back will be courtesy of AMTRAK.

1 comment:

Royski said...

Bummer. Hope the repair goes smoothly. The wet wings in my 1983 Mooney have been good so far.