Letters: 09/04

Tire Talk
While I do not have anything to dispute your tire testing (see The Aviation Consumer, June 2004), let me relate some anecdotal information about our experience with several of your test subjects.

A friend and I were running a flight school in Indiana in the late 1970s and early 1980s. We started with one Cessna 150 and grew to nine. We also had several Cessna 172s, a Cardinal, a 177RG and several Cherokees.

We decided to do an informal study on tire wear to try to determine which tire made the most landings for the least money. We asked each user of our fleet to note the number of landings on each sortie in the aircraft time log.

We had access to the Goodyear Flight Custom and Flight Special and the McCreary AirHawk and AirTrac. Michelin tires were not easily available and they were costly. We did not explore the use of re-treads because of the shipping of a core to the re-treader seemed to negate any savings.

We found that the four tires we tested came in exactly the opposite from your tests. The AirHawk was our best, the AirTrac was second, the Flight Special was third and the Flight Custom was fourth.

We did nothing except look at the cost of the tire versus the number of landings made before a change was made. We did not do the skid test. I must say that we could make a cost decision with reasonable confidence. I just thought it might be interesting to compare.

-Robert B. Fox
via e-mail

Actually, your findings are similar to ours. Heres why: The latest version of the Flight Custom has considerably more tread that the model sold during the 1980s; about a third more.

If you eliminate the top three tires in our tests-not available to you 20 years ago-the McCrearys dont do badly. In fact, the SuperHawk finishes at the top. Had Dessers Monster retread been available, were certain it would have topped your list.


Reference your article on turbonormalizing in the April, 2004 issue: I have had a FlightCraft TN package on my 1987 A-36 since 1997. The system is great. I do not have the improved TAT upgrades. I do not generally run the system lean of peak. I have experienced a loss of takeoff power at low altitudes.

Heres how it all works out: I run at 25 squared everywhere but in the pattern or in turbulence to keep it under the 141-knot Va speed. I flow about 21 GPH at this setting with EGTs in the mid-1300 degree range. I get close to book speeds down low and up to about 215 knots at altitude.

When I bought the conversion, I was told the airplane would have sluggish roll control at high altitudes but this is remedied with gap seals. I had them installed and can say that it does not seem affected by high altitudes in roll input but you definitely recognize a higher pitch attitude at heavy weights above 15,000 feet.

I have BDS tip tanks with an advertised volume of 15 gallons. They hold 17 gallons. Total usable in my airplane works out to about 108 gallons. The tip tanks are not very noticeable in terms of yaw or roll control. The tips use transfer pumps located in the wheel wells. They transfer at a rate less than 17 gallons per hour. I burn to 3/4 indicated on the mains before initiating the pumps to prevent pumping fuel overboard out the vents.

If I am taking a long trip, I run the system at 25 squared for two hours. By then I am at my max altitude and have burned off enough weight to realize close to max cruise speed. Then I pull back to decreasing numbers squared depending on the range I need. I can usually make to Sarasota from Pontiac, Michigan without a fuel stop. Short of something with a refueling probe, what else will do this? My engine was replaced two years after the addition of the TN package because it had 1550 hours on it, had two low compressions and a crack was discovered in two cylinders with evidence of exhaust soot between cooling fins. The new engine has about 600 hours on it and compressions have remained in the mid 70s. I expect to do jugs at 1000 hours just like the stock IO-550s of this vintage. You can get them to the 1700-hour TBO but not typically running them hard.

I lean the engine to peak EGT when below 24 squared in descents to keep it warm. I also have speed brakes if I need them. I try to minimize the thermal shock by changing temperature output of the engine as little as possible. When will we get water cooled replacements for these dinosaurs?

-Kirk Goodell
via e-mail


TCM Cylinders
Great article on large-bore cylinders in your May, 2004 edition. My experience with TCM new cylinders has been abysmal. I purchased a 1973 210L last August with a factory new IO-520. The engine had 350 hours on it and at pre-buy, we noticed low compressions on the number 2 cylinder. TCM replaced the cylinder under warranty without hesitation.

Six months later, at annual, we had compressions on the number 1 and number 3 cylinders of 42 to 45 PSI. My mechanic suggested staking the valves, because he had noticed some carbon buildup on the exhaust valves. Compressions continued to erode in those cylinders until, in June 2004, they showed 35 PSI each. The cylinders were pulled at this time, with an engine time of 550 hours and they showed valve guide wear, burned exhaust valves and excessive valve wear. The cylinders seemed to be at or out of the minimum tolerances as published in the 2000 manual.

When I contacted the warranty department at TCM, I initially received a lukewarm response, since the engine was six months out of warranty. I was told that new cylinder bore tolerances had been published. When my mechanic rechecked the bores using the new tolerances, he found them to be within limits.

This engine has always been maintained under the Top Care program and flown weekly at an annual rate of between 150 to 200 hours per year. I think consumers should have a reasonable expectation of better performance from TCM new engines and cylinders. TCM definitely, in my opinion, has a quality control problem. Ill go with ECI.

-Charles G. Sewall
via e-mail


Garmin Says No
In the article Satellite Radio For the Cockpit in your June issue, theres there is an incorrect assertion regarding the Garmin iQue 3600. A reader said he is running NavAirWX moving map software.

The iQue 3600 cannot run NavAirWx software as it is a Palm device and the NavAirWx software runs on PocketPCs. I do not wish your readers to be under the mistaken impression that an iQue will run this software.

-Sean Kelley
Garmin International