Letters: 02/02

Sweet Relief
Ref your article on personal relief devices in the January issue, great review of perhaps the least-covered aviation products.

My experience with waste handling started in cross country soaring.Fuel stops were definitely not an option and in the early 1980s, I was surprised to find out how many competition sailplane pilots used various dehydration strategies to deal with the problem.

Part of the challenge was probably related to the difficulty of getting water to flow uphill while lying in a prone position.Some lessons learned:Never play with dehydration. It will diminish your skills and will catch up with you sooner or later.Drink normally.

Baggies and diaper stuffed baggies work butyou will spill one eventually.Dumping it overboard either through plumbing or vent is a bad idea if there is any chance of it being deposited somewhere in the aircraft. Ive seen the results of it being sucked back up into the tailcone through a pushrod exit. Its corrosive stuff and can cost you plenty later.

I wouldnt take the chance even if it is an STCd waste line. And if you tried to dump it through a vent or window you already know where it ended up.We kind of like the Little John. It seems well designed to me and is easier to use than a widemouth Gatorade bottle.The Lady J fitting works, too. Perhaps were not as afraid of bodily fluids and the containers that hold them. Its opaque and a lot less disgusting than walking around with a transparentbottle.

Its best feature is that its reusable and can be kept in the airplane. In tight cockpits or demanding situations-high performance sailplanes-an external male catheter and a bag (or well engineered vent) is an excellent solution.The best ones resemble a self adhesive condom with a tube attached.Cheap and available in at any hospital supply. Male only and somewhat inelegant but efficient. The Brief Relief worked pretty well for us but with all of the deficiencies mentioned in the article. The #1 Travel John sounds ideal and we will be stocking up. But the Little John is staying in the airplane.

-Bill Watson
Durham, North Carolina


Timely article on relief devices. Heres a side note on some recent purchases: Three weeks ago, I took a friend and my young son up for a quick flight to the Jersey Shore.

All of us used the facilities prior to the flight. My son removed his seatbelt to get some better views of the Atlantic City in the Club Seating of my A36. Just prior to entering the 45 for downwind, my son was moving all about the cabin and would not put on his seatbelt, seems he had to go. Now.

The large-mouth bottles had just been removed from the airplane and the Little John was still in a box at home. To make a long story short,we circled outside of the pattern once while a three-cell Mag-Lite was utilized. Works well in a crisis and the waterproof O-rings do hold, thankfully.It was much more expensive than a Little John. But it worked.

-Jim Rutkosky
Doylestown, Pennsylvania


Oximeter Warning
I didnt see the original article on pulse oximeters in your September 2001 issue but Id like to comment on subsequent letters youve published on the topic.

Ive been seeing a lot of mention of pulse oximeters and am very concerned about people becoming over confident in them or misusing them. While Dr. Lennons comments in the November issue were mostly correct, he works in a controlled environment with prepped patients. As a paramedic for 11 years, I have extensive experience with pulse oximeters in various environments and conditions other than the operating room.

The biggest concern I have is that over dependence will encourage people to forget to look for the physical signs of hypoxia. The pulse oximeter is an inaccurate device. Fortunately, most errors will show a lower-than-actual spO2%.

-Edward Barr
Pontiac, Illinois


Pre-heat Redux
I appreciated having our systemincluded in theMarch 2001article on aircraft pre-heaters. The sidebar on the effect of cover use is well done. I also like the graph presentation of the results. A picture is worth a thousand words.

However, knowing that heating ispurely a function of wattage-everything else being equal-I am compelled to question the test result. In the test, using two four-cylinder engines of approximately equal mass and under similar conditions, our 200-watt HotBand cylinder heat system was used with a competitors 300-watt oil sump pad heater, for a total of 500 watts.

The other aircraft had a competitors multipoint system totaling 250 watts. Thetest concludes thatthe 500-watt system raised the engine temp 50 degrees and the 250-watt system raised it 70 degrees. It seems counterintuitive anda violation of physical law that we canget more heat from half the wattage. Is there a possibility that the placement of the cylinder temp sensors unintentionally favoredthe 250-watt system?The article indicates that you measured the cylinder heads.

If you used the CHT gauge or another sensor on the aluminum head, they will give a better response to the 50-watt heater mounted in the headthan to our 50-watt heater mounted aroundthe steel cylinder, because the thermal conductivity of aluminum is 3.3 times better than steel.

In addition, aCHT sensormay be in closer proximity to the head heater than to our cylinder heater.

-Robert Reiff
Reiff Preheat Systems

Actually, what our tests showed-and what the published charts indicate-is that the oil temperature using the Reiff bands and Safe-Heet pad rose more rapidly than did the oil temperature heated by the Tanis system.

However, overall engine temperature-an average of cylinders, case and nosepiece temperatures-rose more quickly with the Tanis system. But hardly enough to consider important.

Our cylinder probes were placed about two thirds of the way up the steel cylinder barrel, closer to the head than the base. We think its critical to point out that we concluded that this slight difference in heating performance is immaterial to the goal at hand, which is raising the overall engine temperature to an acceptable value for starting.