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Trivia Testers

What was the origin of the now universally applied unit of measuring speed, the knot, in determinations both aeronautical as well as nautical?

An E-ticket ride you would want to miss
On April 4, 1979, TWA Flight 841, a Boeing 727-100, registered N840TW, prepared for departure from John F. Kennedy (JFK), New York, for a scheduled service to Minneapolis / St. Paul International Airport in Minnesota. During cruise, over Saginaw, Michigan at flight level 390, the 727 suddenly plunged towards the ground at an average descent speed of

  1. 10,000 feet per minute
  2. 15,000 feet per minute
  3. 20, 000 feet per minute
  4. more than 40,000 feet per minute

Class A airspace
True or False: It is illegal to fly VFR at or above 18,000 feet MSL.

All In Knots
What was the origin of the now universally applied unit of measuring speed, the knot, in determinations both aeronautical as well as nautical?

  1. The term comes from the word naught (also spelled as nought), a now anachronistic word which meant zero. From the nautical (ouch) terminology of the mid-eighteenth century, "naught" originally meant 1000 fathoms (which of course had three such digits) in an hour's time.
  2. piddle! A knot was a somewhat derisive term used to refer to a "chip log" which was actually a carved piece of wood that was also weighted so it floated low in the water somewhat like a buoy. A light line was attached to it, the chip log was heaved overboard, and the line was then played out as a ship was under way. It was literally knotted at regular intervals (in the case of the US Navy, 47 feet, three inches), and the number of knots that had run over the side during the interval after which a precisely timed sandglass was turned over and then run out (which in the Navy's case, was exactly 28 seconds) thus indicated the ship's speed. (471/4 feet in 28 seconds is darn close to 6080 feet in 3600 seconds.)
  3. The term comes from the age of steam power. Back in the days of coal bins and sweaty men with shovels, when the coal ran out, the next option to keep running was to tear out the internal planking of the crew's quarters, which was often made from knotty pine (hence the term). Although it originally had no fixed quantity, a ship's speed came to be associated with the number of revolutions per minute of the engines (originally determined when a ship was new, had a clean hull, and was running through calm seas).
  4. A knot was a term used to refer to a "pressure log", essentially a tube bent at a right angle so that its open end was submerged and faced forward into the water (in much the same way that a pitot tube is configured to register dynamic air pressure). The height of a column of water in the tube's vertical segment gave an indication of forward speed. The connection between this metal tube and a knot of wood (though somewhat tenuous) came from the fact that a cylinder of wood, usually made from a knot, was used as a "cork" (into which was affixed a calibrated wire) and indicated the top of the water level in the pipe.

The Answers...

An E-ticket ride you would want to miss
D. The 727 plunged earthward at an average vertical speed of 46,000 ft (14,020m) per minute, with the rate of descent at moments reaching 76,000 ft (23,165 m) per minute. At that speed the aircraft broke the sound barrier and sonic booms were heard on the ground. It was the first time in history that a commercial airliner (other than the Concorde or the Soviet Tupolev Tu-144) broke the sound barrier. The airplane landed safely, and everybody on board survived. The captain immediately became a hero. He was given a medal by ALPA, and the news media honored him. But the praise did not last long. The flight crew was later accused by the NTSB of having purposely manipulated the flap / slat controls during cruise to eke out a little extra speed, knowing well that such a maneuver in cruise was against company procedure. The NTSB released the following accident report:

"The safety Board determines that the probable cause of this accident was the isolation of the No 7 leading slat in the fully or partially extended position after an extension of the Nos 2, 3, 6 and 7 leading edge slats and the subsequent retraction of the Nos 2, 3 and 6 slats, and the captain's untimely flight control inputs to counter the roll resulting from the slat asymmetry. Contributing to the cause was a preexisting misalignment of the No 7 slat which, when combined with the cruise condition air loads, precluded retraction of that slat. After eliminating all probable individual or combined mechanical failures or malfunctions which could lead to slat extension, the Safety Board determined that the extension of the slats was the result of the flight crew's manipulation of the flap / slat controls. Contributing to the captain's untimely use of the flight controls was distraction due probably to his efforts to rectify the source of the control problem."

The NTSB blamed the accident on the crew. Within 24 hours, the crew, once praised as heroes, became the victims of an accusation they might have never committed. Till this day the NTSB maintains that the pilots were at fault. ALPA, on the other hand, still maintains their innocence. Urban legend has it that that captain's name was Hoot Gibson. Well, it wasn't. His last name was Gibson, but it was Harvey G. Gibson, not Robert L. "Hoot" Gibson, who later became a US astronaut (coincidentally, in that same year). You can read all the gory details in the NTSB report at http://amelia.db.erau.edu/reports/ntsb/aar/AAR81-08.pdf.

Class A airspace
Answer: Most places, yeah, but not everywhere. Check out CFR Title 14, Part 71, and you'll find the answer. For example, over Hawaii, would you like Flight Level 300? There is no Class A over Hawaii, so knock yourself out! Here's that FAR:

§ 71.33 Class A airspace areas.

(a) That airspace of the United States, including that airspace overlying the waters within 12 nautical miles of the coast of the 48 contiguous States, from 18,000 feet MSL to and including FL600 excluding the states of Alaska and Hawaii, Santa Barbara Island, Farallon Island, and the airspace south of latitude 25°04' 00" North.

(b) That airspace of the State of Alaska, including that airspace overlying the waters within 12 nautical miles of the coast, from 18,000 feet MSL to and including FL600 but not including the airspace less than 1,500 feet above the surface of the earth and the Alaska Peninsula west of longitude 160°00' 00" West.

(c) The airspace areas listed as offshore airspace areas in subpart A of FAA Order 7400.9K (incorporated by reference, see § 71.1) that are designated in international airspace within areas of domestic radio navigational signal or ATC radar coverage, and within which domestic ATC procedures are applied.

All In Knots
Answer: The "naught-ical" etymology given in choice A is entirely fictional. Choice B is the correct answer. Several different types of speed measuring devices were in use before the pitot tube became the world standard. There actually is some historical truth in the correlation between engine revolutions and forward speed made good mentioned in choice C, and the pressure log mentioned in choice D also really existed (although that stuff about floats fashioned from knots was just bilge water). Other early means of measuring speed included hinged pressure plates, and even airborne anemometers. The nautical precedent favoring knots as a unit of speed (metrification knotwithstanding) certainly would have been hard to ignore!

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