Trivia Testers : En Route Altitudes

Question: What is a MOCA, and what is it for?

  1. It’s airline pilot slang for what the copilot has in his thermos. Maximum overdrive caffeine additive.
  2. Minimum Obstruction Clearance Altitude. It is lower than an MEA or Minimum En Route Altitude, often by hundreds of feet, but it does not assure navigation signal reception beyond 22 nm from a facility. Flying at a MOCA, you will clear any obstacles within the lateral limits of the airway, but if you’re more than 22 nmi away, you might not know what those are! Therefore, they’re for emergency use only.
  3. It stands for Military Oceanic Control Area. It is the extension of a MOA out beyond the 12-mile limit offshore. Military training activities are conducted within its boundaries according to international agreements.
  4. The Museum of Contemporary Art, in LA (definitely a cool place, but nothing whatsoever to do with aviation though)

The correct answer is number 2.

Subject: ‘Away, away with rum, by gum!’

Question: What is the significance of a ‘rhumb line’?

  1. It’s a great tavern in Newport, Rhode Island… also a nice lodge up in Kennebunkport! But seriously, a rhumb line was the straight line that inebriated sailors (or airmen) were challenged to walk after they’d had a few.
  2. A rhumb line between two places does not change true course. A Rhumb Line makes the same angle with all meridians it crosses and appears as a straight line on a sectional (while a great circle appears curved). On a gnomonic projection, it’s the reverse, incidentally.
  3. Also known as a loxodrome, or spherical helix, it intersects all meridians at a constant angle. On a Mercator projection, it appears as a straight line, but strictly speaking, NOT on a sectional. That’s because a sectional (and even a TAC chart) is a Lambert conformal conic projection, which is a cone whose apex is over a pole and which slices the earth at one (or two) chosen latitudes. The result is that the meridians on ‘our’ charts (as well as in reality) are not really exactly parallel!
  4. The ‘rhumb line’ (a bit of a play on words) was the route flown by pilots transporting alcoholic beverages during Prohibition–particularly in the Northeast. It actually wasn’t anything close to a straight line.

The answer is number 3. hic.

Subject: Inertial navigation systems

Question: Which is the most astoundingly correct statement with regard to inertial navigation systems?

  1. A freely mounted gyro-stabilized platform solves the problem of misinterpreting pitch changes (such as on rotation, at take-off) as rapid accelerations, but if it is correctly aligned with the earth’s surface at departure, it would effectively report an outside loop as the aircraft travels (possibly halfway around the world) to its destination. Therefore, although they are not ‘nailed down’, the gyros do require continual alignment with (or references to) the local vertical.
  2. Their sensitivity is so great that a freely mounted gyro platform (if left powered up) would appear to tilt over the space of a few hours, even if the aircraft remained motionless and parked on the ramp, due to the earth’s rotation alone.
  3. Initialization of an INS takes longer at higher latitudes because it takes the gyros longer to sense the earth’s rotation and find true North.
  4. all three

The answer is indeed number 4. (I’m sure you knew this, anyway.)