Wingipedia, Part II

J
Jenny
Although it's also a pretty girl's name, in aviation, it applies to the 1917 Curtiss JN4D, the ex-military biplane trainer that carried barnstorming and aviation into the 1920s. Glenn Curtiss designed both the airplane and the OX-5 (a 90 hp, water-cooled, V-8 engine that lived on to power many new designs).

Jepp charts
The legacy of Elrey Jeppesen (1907--1996), an early mail and freight pioneer, was his concept of making maps (or "charts") that clearly show pilots helpful landmarks. His navigational aids have been aviation road maps for generations.

JetStar
Originally designed as a light military transport, the 10-place Lockheed JetStar was the first corporate jet placed in full production. The unique four-engine layout (two on each side of the fuselage) and wing-mount fuel tanks make it unique. It first flew in 1957 and was last produced in 1978.

Jet streams
These are high-altitude (around 20,000 feet) rivers of fast-moving air that form at the interfaces between two large air masses. Normally, we associate them with the line between northern and southern air masses. Their meandering path across the continent determines much of our weather.

K
KC-135
It's hard to believe that the old (1957) Boeing KC-135 Stratotanker tanker is still performing yeoman's duty fueling the newest aircraft the military has in inventory. It wasn't, contrary to popular belief, a direct adaptation of the 707 airliner, but was derived from the narrower, shorter prototype for that aircraft. The airplane is older than most of its flight crew members.

Knots
Much of aviation is a carryover from ocean travel, including the measurement of distance and speed. The "knot" is short for "nautical mile," which is 15% longer than a statute mile.

Kollsman window
Altimeters measure the change in air pressure as we ascend, but they have to be calibrated to take into account the changing local barometric pressure. That's done by setting the local pressure, e.g., 29.92, in the Kollsman window.

KTAS
Knots true airspeed. Most airspeed indicators are approximations, because temperature and altitude can cause air density (and the pressure it can generate with forward motion) to vary, so they need to be corrected for those effects to generate true airspeed (TAS).

L
L/D
The lift-over-drag ratio of an airplane is a measurement of its ability to glide, power-off. Ten-to-one (10 feet forward for every foot lost) isn't an uncommon general aviation glide ratio. Some sailplanes have a 40-to-one glide ratio.

Lindbergh, Charles
Lindbergh was to his generation, and those that followed, what Neil Armstrong was to later ones. The first to fly solo across the Atlantic, he ushered in a new era in which the airplane was viewed as having unlimited transportation possibilities. He tried to keep us out of WWII, but then became a strong supporter of the war effort and taught pilots long-range cruising techniques and other useful skills.

Localizer
The localizer is an electronic beam that defines the centerline of the runway and can be followed accurately by onboard avionics during an instrument approach.

Lomcevak
Supposedly an adaptation of the Czech word for "headache" or "hangover," the Lomcevak is the appropriate name for the first in an entire family of tumbling maneuvers in which the airplane does the impossible and tumbles end over end. Don't try this in the family Cherokee.

Luscombe
Don Luscombe was an aircraft designer and producer who, beginning in the early 1930s, was active for more than two decades. He developed a number of models, but today the word "Luscombe" refers to his Model 8, a spritely, two-place, high-wing machine with 65 to 90 hp that's still one of the cheapest ways to get into aviation.

M
Mach
The Mach number (named after its creator Ernst Mach) is the ratio of an airplane's speed compared to the speed of sound at that temperature and altitude. So Mach .92 is 92% of the speed of sound and Mach 1.1 is 110%. At sea level and 15 degrees C, Mach 1 is 761 mph.

METAR
Supposedly a contraction of météorologique ("weather") and aviation régulière ("routine")---the French first proposed the format in 1968---the acronym in pilot briefing language just means "aviation routine weather report."

Monocoque
Another French-derived term, monocoque literally translates as "single shell." A monocoque structure has few, if any, internal braces, and all of the load is carried by the skin. Most structures are semi-monocoque as they have stringers and bulkheads. A Cessna rear fuselage is semi-monocoque.

Mustang
The North American P-51 Mustang is considered by many to be the best fighter of WWII, although that's a controversial claim. Originally designed as a ground-attack machine, the addition of the British Merlin V-12 engine with its two-stage, intercooled, super charger gave it high-altitude performance and range few other fighters could match.

N
Nacelle
Where would we be without the French? Another French word, via Latin (navicella), for "little ship." It's a general term applied to streamlined enclosures for engines, landing gear, etc.

Nape of the earth
This term, most often heard in military circles, refers to flying low, in the "nape," as in our neck, of the topography so as to avoid detection.

Navaid
A navaid is any navigational aid, on the ground (VORs) or in the cockpit (VOR receiver). A compass is a navaid, although the term is generally attached to something that's electronic.

NDB
Nondirectional beacon, like a low-frequency (or MF or UHF) beacon that's generating a signal an aircraft can follow. When part of the ILS system, it's called the compass locator.

O
OAT
Outside air temperature is a highly technical av-term that refers to the air temperature outside. One of aviation's harder-to-understand concepts (not!), but one that's needed when calculating true airspeed, etc.

Octane rating
This is a number that gives a gasoline's relative resistance to detonating (autoignition). The higher the number, the more resistant it is. Although we only see 80 and 100 octane today, it used to go as high as 145 for fuel used in high-horsepower fighters and transports. The number you're most used to seeing is derived from the equation, R+M/2. It's an average of the motor octane number and the research octane number.

Ornithopter
One of Leonardo da Vinci's favorite concepts: a machine that flies by flapping its wings. Don't look for one on the back tiedown line at your local airport.

Oshkosh
A city in Wisconsin. An event (the world's largest, annual outdoor happening). A state of mind. A philosophical and psychological destination. Oshkosh is shorthand for the EAA's annual aero-bash, which they insist on calling AirVenture, but is known worldwide simply as Oshkosh.

P
P-factor
P-factor is the yawing tendency caused by the difference in lift on the ascending and descending blades of the propeller. The yaw will be full power on the left, and power at idle on the right, assuming "normal" clockwise propeller rotation.

Piper
When Pennsylvania oilman William T. Piper bought the assets of the bankrupt Taylor Aircraft Company for $761 in 1930 and took control, he started the dynasty that would last for nearly half a century and, in the public's mind, made every light airplane a "Piper Cub."

Pitot
Named after its inventor, Henri Pitot (yes, another Frenchman), the pitot tube allows oncoming air to rush inside where it's resisted by static air within the tube. The difference between this pressure and the static pressure can be calibrated in any speed units desired, e.g., knots, mph, furlongs per eon, whatever.

Propeller
The propeller is actually a clever way to transform the rotary action of an engine and the horsepower it's generating into thrust. Essentially, the propeller is a rotating wing, and the lift being generated drags the airplane ahead.

Q
"Q"
When pilots or engineers refer to "q," they're using a coefficient that relates to the efficiency of the air going over a surface. Part of what affects that efficiency is speed (it's a squared function) and the relative air density. So fast-moving, denser air gives a higher-efficiency surface.

Q-Star (Lockheed, Vietnam)
The Lockheed YO-3 Q-Star program was an effort to produce an extremely quiet aircraft for night reconnaissance in Vietnam. Starting with Schweitzer 2-32 gliders, a bizarre series of airplanes turning huge, slow-turning propellers were developed. According to witnesses, you couldn't hear them overhead at pattern altitude.

Q-tip propeller
The tips look as if you've done a gear-up landing because they're bent 90 degrees. They reduce the propeller diameter, thereby decreasing prop noise, while moving the tip vortices out in such a way that efficiency is supposedly increased.

Queen Air
The Queen Air was the cabin-class step up from the Beech Twin Bonanza and used essentially the same wing. Powered by IGSO-480 and IGSO-540 Lycomings (geared, supercharged), the engines didn't win any popularity contests, but the airframe led to the King Air when turbines were installed, and a legendary aircraft was born.

R
Raptor
The first quantum leap in U.S. fighter design in several decades, it may well be the last, given changing world-combat requirements. The airplane is practically invisible to prying electronic eyes, can maneuver like a humming bird, packs a lethal punch and costs as much as the gross national product of many small countries.

Relative bearing
The relative bearing is a direction as measured off the nose of the aircraft. For instance, a 30-degree bearing is 30 degrees to the right of the nose. Relative bearing relates only to the airplane itself and has no relationship to any other form of heading (magnetic, compass heading, etc.).

Risk
Risk is what we try to manage throughout every aspect of a flight. Just being off the ground in a machine is a risk, but through skill and planning, all aspects of that risk can be managed.

Roll (aerobatic)
A complete 360 maneuver around the longitudinal axis, the primary variations on the roll are the aileron roll (1 G, nose descending); slow roll (-1 G, nose on a given reference); barrel roll (1.5 to 2 G's, nose going around a point 45 degrees off-axis); and snap roll (high-speed stall into a horizontal spin). They're all fun!

Wingipedia, Part I ("acrobatics" through "induced drag")

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