N8ML’s Annual Continued…

The 2013 inspection of N8ML continues. In this installment, I am including some insight and evidence to support my belief that customers need to be aware and informed when it comes to vehicle maintenance. Airplane ownership is, without a doubt, an expensive proposition; however, costs can be kept under control if a person is willing to do a little leg work and mental noodling. This principle applies to automobiles, too!

This past Saturday, we drained the left fuel tank and removed it completely from the airframe so we could replace the fuel tank sender seal. Although the seal was dry, there were signs that some fuel had seeped past the seal at some point. (This was identified in the pre-purchase inspection.) A new seal costs around $6, and we had the tanks pulled out already to do SB-1006 – replacing the seal seemed like a no-brainer. We also replaced a flexible fuel line because the old line was old and brittle. Fortunately, the right tank’s seal and fuel line were in great shape.

My mechanic informed me that pulling both tanks, changing the sender seals (both of them, if required) and the work for SB-1006 would take a total of around four hours for both tanks combined. Imagine my surprise when I compared his estimate with the estimate from the facility that conducted the pre-purchase inspection. They wanted six hours of labor just to change the seal on one tank!

Here’s a screen capture of the service entry from their estimate:

fuel_sender

It pays to shop around and get a second opinion!

Moving along… the new main tires have been installed, and most of the fairings have been put back in place. I think I installed around 200 new stainless steel screws along the way. (Wait – is this an annual, or a restoration?!)

IMG_1528

As I inspected the old main gear tires, I noticed something that piqued my interest. It turns out the main gear tires wear on the inside of the tire. I confirmed this behavior with the mechanic, and he explained that it is good idea to swap the tires periodically to maintain even wear. So why the interest? Well, during the pre-purchase inspection, the facility that conducted the inspection advised me that the nose gear fork (pictured below) was bent, and they further informed me that the technician doing the work had never before seen a nose tire wear so unevenly.

IMG_1529 fork1

As a result, they quoted me $1,927 for a new nose gear fork, plus some labor charges to install it. Oh, and there was a 30-day lead time on the part.

Rpt130225134357_29415

Now, I’m a skeptical individual. I didn’t buy their assessment of the nose gear problem because there were no log entries to indicate any sort of accident or damage to the aircraft, and any accident involving enough force to bend the 1/4-inch steel in the nose gear fork would have undoubtedly resulted in a prop strike and some serious damage to the firewall. This notion was confirmed through discussions with several mechanics. But still, the nose gear tire wear interested me. After seeing the wear on my old main tires, things started to click. I re-opened the aircraft log books and found an entry about the nose tire having been replaced around four years ago using a serviceable, used tire. It seems the replacement tire had been used as a main gear tire previously, and that explains the “unusual” wear pattern on the nose tire now. My mechanic confirmed this conclusion. Thankfully, uneven wear on an airplane tire has no impact to ground handling.

I suppose the mechanic that did the pre-buy inspection may need some more experience….?

The final area of interest with respect to expenses and shoddy estimates relates to the engine mount. The mixture control cable for the engine was allowed to flex a bit more than optimal. Over time, the cable chaffed a small groove into the engine mount. The groove isn’t a big deal, but it isn’t something you want, either. The fix requires a few minutes of work with a gas torch to add some additional material to the area. Once done, the area is filed to remove any jagged edges, then painted to prevent corrosion. The repair takes about an hour at the most.

enginemount1

While researching this issue, and the required repair, I learned the engine mount is made of un-tempered 4130 chromoly steel. Since the parts are not tempered, no post-weld tempering of the welded area is required. Piper Aircraft confirmed this to me over the phone. It seems manufacturers specifically avoid tempering engine mounts because the process significantly increases maintenance costs while providing a minimal strength gain. The preferred approach is to simply use slightly larger gauge 4130 steel for the mount tubes.

Now back to my pre-purchase experience… During a discussion with the inspector about the engine mount, I was informed the engine and the mount would have to be removed from the airplane. The mount would be sent out for repair, and they could not provide me with a cost estimate for the outside repair. They would then re-install the repaired mount and engine. The job would take at least twenty-four hours, and the labor charge alone would be $2,088.

Here’s their estimate (note: two images because the job spanned multiple pages of the PDF document):

engine_1engine_2

I asked about welding the mount on the airplane, and they told me the mounts were tempered and therefore removal was required so the mount could be re-tempered after repair. Um. Yeah. I suggested they might want to call Piper on that bit.

The pre-purchase repair estimates listed above tally to more than $4,700. My cost after doing some homework: ~$633 in labor and parts – a savings of over $4,000!

At this point, we’re almost done. Hopefully she will be all buttoned up, signed off, and ready to be back in the air in a few more days. The next stop will be the wash rack. Old girl needs a bath something fierce!

This entry was posted in Flying stuff. Bookmark the permalink.

Leave a Reply

Your email address will not be published. Required fields are marked *