Letters 05/98

Firefly Debate
Good article on the T3A debacle in the February issue. A question that came to mind was why not just buy new 172s to replace the aging fleet of T41s? Instead of spending $10 million just to investigate the T3A engine stoppage problem, an entire fleet of 110 C-172s would have cost around $14 million. Our tax dollars in action. Your article and the above question is going to my Congressman and senators.

Your Mooney Predator article repeats a bit of mis-information that Ive seen before whenever you write about Mooneys. That is, roll is especially stiff due to the use of push-pull tubes rather than cables. I would be very interested to learn more about this. Please explain why this is true.

Actually, tubes have nothing to do with it. The control force is a function of the control systems geometry, moment arms of bellcranks, hinges, etc. and the type of aileron used. If you think about it, why would it make any difference if you actuate a given bellcrank under given loading conditions with a cable or with a tube?

Either way, the same force would be required to move the bellcrank, and it doesnt make any difference whether that force is applied by a cable or by a tube.

If you continue to doubt the above, then please explain why the RV homebuilts have probably the lightest aileron forces of any kitplane and are tube actuated? Id guess that the worlds top aerobatic aircraft also use tube actuated controls. Im not defending Mooneys and Im not saying they dont have heavy roll forces. Im just defending push-pull tubes and encouraging accurate reporting.

-Bob Reiff
via e-mail

There are two reasons why the Air Force wasnt interested in Cessna 172s. For one, they werent being made when the Firefly contract was awarded and, second, the 172 isnt fully aerobatic. Although Air Force instructors felt that an aerobatic airframe was neither necessary nor desirable in a screener, political considerations dictated otherwise.

As for Mooney control friction, your comment sent us back to Tom Bowen, Mooneys chief engineer. While it is true that push-pull tubes in general dont introduce much additional friction, the Mooney design uses fiber rub blocks in the wing stations to prevent tube crimping under airloads. When the tubes are loaded, they rub against the blocks, thus producing additional friction.

Three-Bladed Props
I enjoyed the February, 1998 article on the three-bladed props. Generally, it mirrors our experience. In April, 1991, we had DorAviation of Sedalia, Missouri, install a McCauley three-blade BlackMac prop on our 1966 Cessna 182J. We had not owned the aircraft very long.

The propeller on the plane was original and from the logbooks we could not tell that it had ever been touched. It was sent to a shop for a complete checkout. To make a long story short, we decided to install a new prop. After some research (prop theory 101), this electrical engineer pilot decided to install a three-bladed prop.

We were the first in our area to do so. Our mechanic encouraged the selection (probably for the looks) although my wife and I were more interested in reducing noise and vibration. If memory serves me correctly, the cost differential was about $1500 above the new two-blade at the time. We expected to lose a couple of knots at top speed and probably did, although we never operate there so I cant honestly say that we know for sure.

The airplane is quieter. Probably not the one third reduction in noise that others thought, but perhaps a perceived 20 to 25 percent reduction. As far as climb rate, it feels stronger. Acceleration on takeoff seems better, although I have no numbers to confirm before and after perceptions.

I did note that the glove box started coming open on takeoff run after installation of the prop. The magnet on the latch needed adjustment to stay shut with the perceived added acceleration.

The bottom line is this: We have had no problems and the airplane is quieter. Would I do it again? Yes. One other thought was and still is: What has this done to our glide in an engine-out scenario with an extra blade of drag? We would be interested if anyone out there has data on this.

-Ron Bowman
via e-mail

VGs for Navajos
In your Used Aircraft Guide on the Navajo, you were surprised to find that nobody lists vortex generators for the Navajo. Boundary Layer Research, Inc. does in their Trade-A-Plane ads. The Navajo 310, 325, Chieftan/T1020 and Colemill Panthers are all covered.

-Gary Miedema
via fax

Aerox Kudos
I have been reading your Aviation Consumer for several years and have always enjoyed your articles. As a follow up on your coverage of portable oxygen system, let me share my experience with Aerox.

I have been using the Aerox system with cannulas in my Mooney Ovation since May of 1995. The systems has delivered excellent service.

Recently, one of the nozzles broke and I called Aerox. They shipped to me (in France) free of charge a new one. When I replaced the nozzle, it appeared that the regulator was not operating. I called back Aerox who offered to repair it.

The part was repaired and shipped back to France at no cost once again.Aerox to me not only ranks very high as far as customer support is concerned, they also do it with a nice style.

-Francois Duliege
Le Perreux, France

Progressives? Bah!
Heres my experience with progressive lenses. They were to be my first pair of glasses. I had been told that they are supposed to be the best thing since sliced bread. Hogwash!

What nobody tells prospective wearers about these lenses is that they intentionally distort approximately half of the available lens area. The upper half is usable as only a slender piece, like a golf tee down the middle; the rest is unusable. On my glasses, when I looked at the panel, the top of the gauges appeared to tilt about an inch to the right.

When I looked at the gauges on the left side of the panel, they again took an oval shape only now they tilted about an inch toward the left. Can you imagine trying to fly IFR in turbulence with glasses like that? I went back to the shop where I had gotten them and they said Youll get used to them . Excuse me! These things are supposed to assist me. I shouldnt have to adjust to them.

I tried flying with them and found them to be totally unacceptable, even dangerous. When I tried to land, the runway edge lines were distorted and curved. Altitude information during the flare was just totally distorted. I went around, tossed the glasses over my shoulder into the back seat and then made a normal landing.

In the article you ran about this type of lens in your October 1997 issue, the author wrote that if they dont function properly at first, you may have to go back several times to try and work out the problems.

I ask you, would you keep bringing your airplane back to a mechanic who tells you right up front that hes so incompetent or the parts he uses are so poorly made that he may not get it right, but just keep on bringing your plane back and maybe eventually he will? I dont think that too many pilots would. Why bring something so precious as your eyesight to that environment?

Also, in the article, the author made a big deal about the appearance of these glasses with no bifocal line. I suspect that most of us who have reached the age when we start to need bifocals have long ago gotten over the adolescent insecurities about appearance. I did. So my bifocals have a line, big deal. My kids tease me and call me six eyes.

My advice is to get a standard bifocal with the bifocal part as wide as possible-its called the executive cut-so you can see the entire instrument panel by moving your eyes only and get the line positioned so it lines up vertically with the top edge of the panel.

This way you have both distance vision and near vision without bobbing your head left and right or up and down. Your gauges stay round and you are not intentionally distorting a major portion of your eyes viewing area.

Anybody out there remember reading about vertigo?

-Rod Dykhouse
Templeton, California