Question: A ‘haboob’ is
- a Saudi sidewinder
- a dust or sand storm
- the aeronautical equivalent of a scupper hole for drainage of water from the edge of a deck, but in the case of aircraft it is from the lowest point in a fuselage
- a garlic-flavored dip made from eggplant and tahini
Answer: B. (Honest.) From the Arabic habb, meaning ‘to blow’, it was originally a term for a penetrating sandstorm or duststorm in the deserts of Arabia, North Africa, and India, typically occurring late in the day during summer. However, they also occur in less exotic places like, say, Kansas, or Phoenix! They generally take a lens shape, appearing from a single point in their path as an advancing (and very intimidating) wall of sand or dust, generated from the surface outflow portion of a mature thunderstorm cell. They can move at speeds approaching 100 knots, and can last for several hours and rise to heights exceeding half a mile. In the US, they can occur from May through September, and most frequently in June. (Choice D is actually baba ganouj, in case you’re a pita fan…)
There are many more of these weird-sounding kinds of words used to name winds that originate in other parts of the world. In South Africa, the name for the hot, dusty winds that blow toward the coast is “berg” (though it conjures up a different image, at least for me). In the Mediterranean, the name “borasco” is used for strong thunderstorm winds. Another perhaps more familiar term is “sirocco” (no, not the Volkswagen). It’s the name for the hot, dusty wind that blows in from the Sahara Desert, to the north or northwest across North Africa. It can pick up moisture in traversing the Mediterranean, arriving on the other side (southern Italy and Sicily) as a warm, humid breeze.
Subject: Clocking Raindrops
Question: How fast does the average raindrop actually fall?
- six knots
- 10 knots
- 16 knots
- 32 knots
Answer: B. The vertical velocity of an average raindrop is about 10 knots (or 11 mph) without any wind. Larger drops can fall faster (about 16 knots), and very light mist can almost hover, falling at only about 1/10 knot.
Subject: Murphy’s Corollary: Headwinds
Question: True of False: On almost any given round-trip cross-country of one or two hundred miles done on the same day, for all practical purposes, any wind is a headwind.
Answer: True. This would probably not apply with a frontal passage or a significant shift in wind velocity between the initial and the return trip, but for a simple scenario, any tailwind during one half is going to be more than cancelled out by the headwind during the other, because of the greater time that headwinds act on the airplane overriding what I call the ‘shorter tailwind time’. If you do the math for some ‘standard’ empirical winds as a fraction of true air speed (TAS), the general formula would be, solving for time from the relationship of Distance = Rate * Time (where D = one-way distance, and 2D = round-trip distance):
- 2D / TAS < ( (D / (TAS – wind) ) + (D / (TAS + wind) ) )
Regardless of whether you’re flying a Lear or a Cub, whether the winds aloft are halacious or just a gentle breeze, and whatever the relative angles are between you and the wind, the following examples will hold true, in regard to how it will lengthen your trip (compared to no wind at all, which is an extreme rarity):
- wind = 1/100 * TAS = only 1/9999 longer
- wind = 1/20 * TAS = only 1/399 longer
- wind = 1/10 * TAS = only 1/99 longer
- wind = 1/8 * TAS = only 1/63 longer
- wind = 1/5 * TAS = only 1/24 longer
- wind = 1/4 * TAS = still only 1/15th longer
- wind = 1/2 * TAS = hmmm… 1/3 longer
- wind = 70.7% of TAS = yipes! TWICE as long!
- wind = 3/4 of TAS = whoa! 2 & 2/7th times as long!
The disadvantages in terms of increased trip times start out small, but in the extreme case of the wind equal to your TAS of course, the disadvantage is infinite.