Unicom

December 2004 Issue




Unicom: 12/04

Touch And Goes?
I am in full agreement that touch-and-go landings (“Touch And Goes,” October 2004) are not that useful. Heck, they don’t even count for currency in a tailwheel aircraft. But mostly, they are very unrealistic and don’t teach that much. I would agree that if you need to do them, make sure you have lots of runway. But if you have lots of runway, think about a stop-and-go landing. Land, stop, reconfigure, perform whatever checklist items you need to do and then go. You get to practice a takeoff too!

Instead of practicing touch-and-goes, we ought to practice more go-arounds. Sometimes I think they are a lost art.

Vince Massimini
Via e-mail

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Mooney Fuel Capacity
With reference to Paul Bertorelli’s article on running fuel tanks dry (“Dry Tanking,” October 2004), we have owned a 1981 Mooney 231 for 13 years. During the first eight years running the TSIO 360, at 65% power, we used 11-12 gph, had a true airspeed at 12,000 feet of 160-165 knots, resulting in a range over 700 nm.

Five years ago, we purchased the Rocket conversion, which is a replacement TSIO 520 engine. This has two effects, with the obvious one being the increased fuel flow which measurably reduces range. The less-obvious change has to do with weight and balance.

With the larger engine, we usually still fly 65% power, but now burn 17-17.5 gph and true out at 185 knots. I usually file 4:10 (full tanks) endurance and plan to land in no more than 3:40, usually less. There is some comfort in that we can throttle back to 12 gph to extend our flight time and range if necessary.

Total fuel used has been no more than 61 gallons for 620 nm no-wind range. Using the factory numbers, I should have 14 gallons left, but I suspect that it is really closer to nine gallons, which is in agreement with your results.

The effect on weight and balance is a related problem. With full fuel, two 170-pound pilots and no bags, the CG is beyond of the forward limit. With less fuel, the CG is within limits. With just my wife (110 pounds) and myself (180 pounds), the aircraft is right at the forward limit with full tanks, except when full tanks is 69 gallons instead of 75, then we are well within limits. It is tempting to use the lower amount, particularly when I am flying with my instructor who weighs more than 200 pounds. Then I have to leave off some fuel and put 70-80 pounds of ballast in the baggage compartment to stay within the forward CG limit.

The extra six gallons of fuel would be very comforting. To be safe, I will continue to use 75 gallons for weight and balance and 69 gallons for endurance.

As an aside, at a MAPA meeting years ago, I attended a seminar by Bill Wheat. I thought that he said that full fuel was just to the flapper valve and that the empty space was required by the FAA for expansion. With the above problems in mind, I wrote Bill and asked if this was true. He replied that no, full tanks is as much as you can get in, right up to the brim.

It might be interesting to have his opinion as to the accuracy of the factory tank capacity. I have not tried to calculate the effect of temperature, but I am sure that it is considerable. The solution to all this is to install long-range tanks.

Thank you for your article. It was certainly most appropriate.

Ivar Lindstrom
Via E-mail

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Pulse-Ox Readings
Reading my hypoxia files, I came across an answer from you guys in “Unicom” from July 2003. It read in part, “pulse oximetric experience suggests that many pilots are hypoxic at 10,000 feet and make more errors at 10,000 feet.” I have a pulse oximeter and am alarmed at how low my sats are in the teens.

Drew Doorey
Via e-mail


Drew, the studies we have seen agree with the statement from July 2003, but the key point is that everyone tolerates altitude’s effects differently. Similarly, the same person may have a completely different pulse-ox reading from one day to the next. The best solution, as Brent Blue discussed in November’s issue (“Mid-Teens Physiology”), is to always use a pulse oximeter when flying at altitudes where oxygen is useful (not just where it’s required) and to maintain a reading within five points of your “sea level” value. Especially at night, 5000 MSL is not too low to strap on a tank.

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More Pattern Sins
I enjoy reading your articles and almost always agree with your suggestions. Thanks for your good work. In your article “Five Pattern Sins” (June 2004), I take issue with your “Tri-State Pattern” section. While I agree that huge patterns are not helpful, I am surprised that you would condone a 1/8-mile final. Assuming a 60 KIAS approach speed, that is asking for the pilot to turn final 750 feet from the threshold, about seven seconds from touchdown, and approximately 63 feet about the touchdown zone (on a 4 degree glideslope). In fact, it would be difficult for most aircraft to descend from pattern altitude abeam down to the touchdown zone in that short of a pattern unless power was completely off and drag was added.

I could possibly support the 1/2-mile final, but 1/4 or 1/8 is pushing it. While the AIM doesn’t give us much help on how to fly a pattern, it does suggest that 1/4-mile final is a minimum (4-3-3).

Brian Shepson
Redlands, Calif.


Actually, our view is that 1/8th mile isn’t too short but as with all things requiring judgment, do what’s comfortable for the situation at hand. We like the short final because it does two things: it makes the use of pattern airspace more efficient and it sharpens your skills for the day when you might actually have to fly such a pattern after an engine failure. However, to fly a pattern that tight, you may have to resort to an overhead pattern, as described in our December 2003 issue.

And yes, we are suggesting a power-off approach for normal landings in airplanes for which it’s practical, and that includes most singles. Again, you’re teaching yourself to fly a pattern accurately to a predictable touchdown without the crutch of power, which may not always be available. Perhaps the best strategy is a mix of power-on and power-off approaches for normal landings.