The Straight Dope | The Straight Dope | Chicago Reader

The Straight Dope 

Sign up for our newsletters Subscribe

THE TEEMING MILLIONS SPEAK

I wish to comment on your column concerning AIDS transmission between women [January 27]. Avoiding sex toys is not enough to eliminate the risk of AIDS during female/female sex. Tears or open sores in the mucous membranes of the vagina or the mouth, including the tongue, cheeks, and lips, are potential points of entry for AIDS or any other infection. Although female-to-female AIDS transmission is rare, the possibility should not be ignored. Don't give your readers a false sense of security. --Gail Iwatiw, RN, Weiss Memorial Hospital, Chicago

Technically you're correct. However, the use of sex toys and rough sex in general undoubtedly increase the risk of AIDS transmission considerably. In the one case of female-to-female AIDS transmission on record (Annals of Internal Medicine, December 1986), "both women had vaginal bleeding as a result of traumatic sexual activities." Admittedly they had other dangerous habits as well. The woman who had AIDS to start with injected drugs with a needle; the second woman had "digital and oral contact with [the drug user's] vagina" during the latter's menstrual period. Cecil would therefore restate his advice to lesbians as follows: avoid rough sex, avoid sex during menstruation, avoid sex when either partner has open sores or tears in the skin, and above all avoid sex with junkies.

Incidentally, I have found mention of an earlier lesbian AIDS victim for whom apparently no cause of transmission could be determined, so it's possible there have been not one but two cases of female-to-female AIDS. I also note that the first case of female-to-male AIDS transmission via oral sex alone (i.e., no visible skin breaks, no sex during menstruation, etc) has now been reported (New England Journal of Medicine, January 26). But let's have a little perspective. We're talking two or three cases out of 88,096 confirmed AIDS victims, as of February 28, and an estimated 1 to 1.5 million persons who are HIV-positive. There have been three cases of AIDS transmission involving acupuncture, for Jah's sake. My point is that AIDS transmission between lesbians isn't impossible, it's just not very likely.

FLASH TO HELICOPTER PILOTS: DON'T STRAIGHTEN UP TO FLY RIGHT

I just finished reading your explanation of how a helicopter operates [January 13], and I think maybe you should stick with figuring out the directions on cracker boxes. You state that for forward flight the pitch of the blades is increased at the rear of the helicopter and decreased at the front. This is inaccurate. Due to a phenomenon called "gyroscopic precession," a force applied in a rotating system takes effect 90 degrees forward of the point at which the force was applied. Thus when the blades are at maximum pitch on the left side of the helicopter, maximum upward "flap" occurs at the rear. When there is minimum pitch on the right side, the blade flaps lowest in front. This tilts the rotor system (although not necessarily the fuselage) forward, resulting in forward flight.

As for turning, you gave the correct method for turning a hovering helicopter. [Cecil said you use the tail rotor, which is controlled by the pedals, to point the helicopter in the right direction.] Turning while in forward flight, however, is quite similar to turning an airplane--move the stick left and you will bank to the left. Unlike an airplane, the pedals aren't used when making a turn. You see, it is easy when you know how. --Nolan Beck, 11th Special Forces Group, Fort Meade, Maryland

Cecil knows all about gyroscopic precession. It is not the most obvious concept in the world, however, and I felt I had to choose between an explanation that was oversimplified but comprehensible or complete but totally opaque. In retrospect this may not have been the smartest move--I mean, cripes, I even had a guy from NASA giving me flak on the subject. Regarding turning . . . well, I always did wonder why all the other pilots in Nam used to stare when I stopped the helicopter before changing direction. Thanks for the tip.

Art accompanying story in printed newspaper (not available in this archive): illustration/Slug Signorino.

Comments

Subscribe to this thread:

Add a comment

More by Cecil Adams

Popular Stories