Letters 09/99

Autopilot Feedback
As the owner of a 1980 Beechcraft V-35B equipped with an S-Tec 60-2 autopilot, I was interested in your July issue because you featured both my airplane and autopilot.

Most writers fail to realize the most important advantage of the rate-based autopilot: The added margin of safety. Attitude-based systems (Century and Bendix/King) fail when the attitude gyro fails due to vacuum pump or mechanical failure.

A fully-coupled S-TEC autopilot will fly the en route leg, descent, and ILS with a failed artificial horizon. In your features we can live without comment, you stated that altitude pre-select tops the list-no argument, when youre talking the climb mode. But I think its most useful in the descent mode (particularly with a failed attitude gyro).

In addition, there’s no need for a back-up vacuum system for your attitude gyro, since the autopilot will pinch hit and similarly, no need for a second attitude gyro.

-Hal Waggoner
via e-mail

We think that the safety argument is a stretch. Admittedly, the attitude gyro is vulnerable to both a mechanical and a vacuum failure and its true that a rate-based autopilot will soldier through a vacuum or AI failure. But the same autopilot is a goner if the turn coordinator fails. Take your pick on which one is more likely.

Hangar Analysis
I read the hangar envy article in the June issue. I have had extensive experience with aircraft both tied down outside in Washington D.C., and later, my own aircraft hangared in the same area.

I think your analysis of the costs and other advantages/disadvantages of hangaring the aircraft was short of the mark. The article talked about the costs of the hangar versus the costs of redoing paint and interior and came to the conclusion that somewhere between $200 to $300 per month was the break even point.

If paint and interior were the only considerations, then your analysis would be acceptable. However, there are other aspects of what happens when the airplane is hangared or not. These were only mentioned briefly.

Start with corrosion. How many times have you had the starter motor hang up due to the constant spray of rain it receives tied down outside? Or how about the water that collected in the spinner, froze, and thus canceled the flight due to the imbalance.

And then there’s the screws on all the access plates that are rusted in place when you try to remove them at annual time. The extra hours the mechanic spends removing them sure shows up on the bill. Or small water leaks around windows that become major problems because of the hours of rain during certain periods of the year. And, don’t you love doing even simple maintenance on the ramp with the temperature in the 30s and a 15 MPH wind?

During the time my aircraft was hangared, I found that owner maintenance was a breeze (pun intended). The hangar was lighted enough so that an oil change could be completed after dark. Other minor maintenance could be completed without the requirement to button up everything before I left. Even in that drafty hangar the cold was bearable as I had a small electric heater.

Annuals were less traumatic. I could remove wheel pants and inspection covers, the mechanic could do the inspection, repair what was needed, then I could do skut work, like lubrication, at my own pace, replace inspection covers and wheel pants, and it was done for the year.

I recognize that some of the above are difficult to put a price tag on. But they sure made aircraft ownership much more enjoyable; and thats what its all about.

-Marty Ditmore
Las Cruces, New Mexico

Youve just quantified what we call the cost of convenience. And we agree, you cant put a hard number to it, which is why we stuck with the paint and upholstery issues.

Lax QC
I enjoyed your article about cylinders and bearings in the July issue very much but it left me with a very sick feeling. Havent your readers and especially ECI, Superior, and other manufacturers of engine parts heard of the ISO 9000 system for quality control?

This system came about because of the problems all manufactures face,specifically not being able to consistently reproduce a widget the same way to the same specs over and over. It appears that the FAA/PMA certification process is not working here.

There is no magic to producing widgets or cylinders repeatedly to the same specs. The secret to doing it relies in a QC system that works and is adhered to. The ISO 9000 system-I have no personal interest in it other than my company being certified to its various standards-is an internationally recognized system that enables a purchaser of a product to be assured of the quality of the widget he is purchasing. In other words, the widget meets the specs you require.

In your article you recommend performing a 10-minute CylinderInspection. This is necessary but hardly the thing that will get partsmanufacturers to change their ways. Its like taking an aspirin to curethe pain caused by syphilis. Why not cure the problem not the pain?

Why would companies want to switch to this quality control system? First, they would not get parts returned. This saves lots of money. You can imagine the system set up to deal with all these returned parts is very expensive. Not to mention the time required to reman or produce a new, hopefully correct part.

Second, it really helps the image of the company. This is hard to quantify but you’ll be talked about at cocktail parties (or in Aviation Consumer) in a good rather than a bad light.

Some day my engine will need new cylinders. When that day comes, will I have to take them over to my mechanic and say, here will you please mic these parts to see if they meet specs? The parts people Ibought these from didnt care enough about their products so I need to pay you extra to find out if I have to return them.

I guess there is an alternative. Take the part to the FAA and tell themwhere you got it. Then tell them it doesnt meet spec. Eight monthslater they might get around to reminding the company you bought it from that their PMA certification is in jeopardy.

Other industries have adapted these internationally recognized standards why not aviation in the U.S?

-Carter Boswell
via e-mail