Letters 02/01

Aviation Labs Is Tops
Regarding your article in the December issue on labs that perform oil analysis, I thought I’d pass this along. For several hundred hours I have been finding aluminum flakes in my oil filter and suction screen. Oil filter elements were sent to three of the labs mentioned in your article.

I even sent samples to Light Plane Maintenance, your sister publication. Two of the three labs and LPM diagnosed it as aluminum, probably from the piston pin plugs.

Both recommended flying the airplane another 25 hours, resampling, and borescoping the cylinders for telltale striping. The flakes came and went, reappeared and disappeared.

I did this for 200 hours thinking everything was basically okay, since the oil analysis was normal and the occasional filter element examination was deemed normal by two different labs. After all, Lycoming has a history of piston plug problems and all the experts said wait and see.

On a trip to Oshkosh this year, I got a free oil filter/particle analysis kit from Aviation Laboratories in Kenner, Louisiana. At my last oil change in December, I found about eight flakes in the suction screen and, since I had a free kit available, I sent the particles off for examination. Within 96 hours, I had a call from Chris at Aviation Labs warning me that the flakes I sent him were an alloy with a chemistry of 97 percent aluminum and 3 percent tin.

He said this was most likely bearing material and recommended I talk to Lycoming for advice. I called Lycoming and talked to Mike Caldera who agreed with Aviation Labs findings and recommended immediate grounding of the aircraft along with teardown and inspection of the engine. To make a long story short, I disassembled the engine over Christmas and found significant damage to the front main bearing. Luckily, the crankshaft looks okay. The bearing’s top layer of babbitt was peeling and approximately two square inches was already missing. One flake, approximately 3/8-inch square was just floating on the bearing’s surface.

I’d like to point out that only Aviation Laboratories was able to pinpoint my problem and immediately alert me to a potentially dangerous situation. In talking with Chris, I found that they, unlike other labs, use a scanning microscope to analyze particles.

This enables them to find the 3 percent tin in an aluminum flake that the other labs missed. In light of the fact that Aviation Labs didn’t rate high in your comparison, I wanted you to know that they did an excellent job for me and I will use them from now on.

-Mike Ferrer
Roanoke, Texas


LASIK Clarification
The article on LASIK in your January issue contains some misinformation regarding the requirements for climbing back in the cockpit following refractive surgery. Both Coyle Schwab—who braved the procedure-and my friend Ben Rosenberg, who opted out for well-thought-out reasons, incorrectly suggest that the FAA requires “formal approval” (Schwab) and/or “one to six months of eye stability” (Rosenberg).

Even Dr. Siepser gets this wrong, but he recovers by noting that the treating ophthalmologist, not the FAA, determines when the pilot is ready to resume flying.  In fact, the FAA merely requires that a pilot not resume flying until his own treating health-care professional determines: (a) the post-operative condition has stabilized; (b) there have been no significant adverse effects or complications, and (c) the pilot meets the appropriate FAA vision standards. 

If these determinations are favorable and he or she is otherwise qualified, the pilot may immediately resume flying. There is no FAA approval procedure, nor is there any minimum stabilization period. Typical stabilization periods, particularly in younger pilots, may be as little as two weeks and often significantly less than one month. I had LASIK on November 13th and was signed off by my own doc 15 days later. 

-Hilary Miller
Greenwich, Connecticut


We agree. We should have clarified the point that post surgery, the pilot and his eye doctor determine fitness to fly, not the FAA. However, the FAA does require that a written report of the eye exam be filed with the agency. No further approval is necessary.


Monroy and Ryan
The article on traffic avoidance gear in the November issue was we’ll researched and informative. I’ve been flying with the Monroy ATD-200 for the past year and a half in my Cessna 172. I think it’s an excellent value. 

Originally, I mounted the unit on the glare shield using Velcro, but recently installed it in the panel as part of a panel/avionics upgrade project.

Worth mentioning is the Mode-C altitude decoding circuitry in the ATD-200. If nearby traffic is responding to radar interrogation with altitude information (Mode-C), the ATD-200 will only alert if the traffic is within 1500 feet (above or below) the altitude of the airplane in which it’s installed.  This feature is helpful in areas where traffic density is high.  

In the December issue, the article comparing the Piper Archer and the Cessna Skyhawk contained a minor error. The article states that the first 172 was introduced with the Continental O-300-D. 

Actually, the 172 was equipped with the O-300-A until 1960, when there was a change to the O-300-C.  The O-300-D, which accommodates a vacuum pump for gyro instruments and has a “start” position on the magneto switch (starter solenoid instead of the T-handle starter contact arrangement), became available in 1961 on the upscale Skyhawk.  The basic 172 continued to use the O-300-C.  Airplanes equipped with the O-300-A and O-300-C typically use venturis mounted on the starboard side of the fuselage to provide vacuum for the gyros, or use electrically powered gyros.  

-Stan Cooper
San Francisco, California 


I just did Field Morey’s west coast adventure.  He’s got a Skywatch and given that I fly in the congested San Francisco bay area, the experience made me a believer. I was looking forward to your recent TCAD/TCAS article hoping you would have some insight on the Ryan 9900BX. 

Any updates on this?  Specific questions I have: Reliability?  Field’s Skywatch died south of Edwards Air Force Base. He said it did that on the previous trip also.  It came alive the next day in Sedona.

The dual antenna debate: Did Ryan really solve the shadow problem?  This should be something that can be determined from the 9900B.  I noticed on Field’s TR182 that there were momentary drop outs for traffic under the wings.  Not a problem in my opinion. Of greater concern is the tail shadow at the 6 o’clock low position. I can imagine that being a problem if a jet is chasing you out on departure.

Filtering software:  You mention that the Skywatch won’t alert you of near traffic unless there’s a collision threat.  Doesn’t the 9900BX do that too?

Also not mentioned in your article is the fact that Ryan gives you the squawk code from any target.  As far as I can tell, Skywatch won’t do that.  That seems like a useful feature, especially as you can get N-numbers from the airline transponders.

-Colyn Case
Via e-mail


The short answer is no, we don’t have any additional information available on Ryan’s 9900BX because, as we noted, no test unit has yet been made available for us to fly. We’ll examine the issue again in a few months.