Trivia Testers: Did You Know…

A second installment of Jeff Pardo’s Trivia Testers: When we’re talking “degrees” it’s not always about the weather…

Like a bat outta
The climb angles for most GA airplanes could hardly be described as spectacular. For most single-engine Cessnas out there, the actual climb path traveled is around 6 degrees up from the horizontal (though the deck angle would be a bit greater than this) — that’s not scalded ape territory. What would be climb angle associated with the best rate of climb (Vy) for an Extra 300L? Variables: Standard temperature and pressure (STP), and an ‘Acro 1’ weight — which is ‘light’ — at 1808 lb.

  1. 11 degrees
  2. just over 19 degrees
  3. exactly 45 degrees
  4. straight up

The answer is (2). In the 300, the best rate of climb (Vy) is 3,200 fpm, though it’s lower at Maximum Gross Weight. The associated airspeed is 96 kts. No present-day piston powered production airplane can reach 45 degrees, though there were some experimental military airplanes, the ‘tail-sitters” that actually could climb vertically, ‘on the prop’. (The landings were, shall we say, dicey.)

Runway Numbers: They’re NOT cast in concrete!
Under what circumstances might a runway number misrepresent its true magnetic direction?

  1. Almost always. Runway numbers are an approximation of their magnetic direction rounded to the nearest multiple of ten degrees. So nine out of ten times, the true magnetic direction will be at least a degree off from what you see painted on the runway — multiplied by ten, of course.
  2. Choice (1) is true, but there’s more! Whenever there are more than three parallel runways (such as at Dallas-Fort. Worth) at least two of them will be deliberately misnumbered. Rules allow for only three sub-designators: L (left), C (center) and R (right). Under these circumstances, they set up two pairs, one of which is ‘wrong’.
  3. Choices (1) and (2) are true, but on top of that, the earth’s magnetic field is always changing, and the magnetic variation would eventually render those painted numbers obsolete … if you waited long enough. Fortunately, this occurs over a time frame of decades in the US. (Just for the record, if you’re up near the magnetic North Pole in Canada — which is moving towards the northwest at about 10 Km per year and which also has a diurnal variation of up to 80 Km … that’s elliptical in shape … you don’t use a compass anyway.)
  4. Although there are specifications regarding every detail of airport signage and markings, there is actually no rule that says runway numbers must correspond to magnetic direction. If an airport operator wanted to number a runway to avoid the number ’13’ for example, he or she is entirely free to do so.

Choice (4) … is nonsense. As for (3), there aren’t any hard-surface runways that far up in northern Canada. Farther south, runways are marked to the nearest tenth of the magnetic azimuth corresponding to the runway centerline — if things change, so should the runway numbers… The answer is (2).

On dynamic rollover angle in R-22’s:
How precipitous a hill can a Robinson R-22 helicopter land on, sideways along the slope, without rolling over and balling up? What are those angles; first, with full opposite cyclic, AND second with no compensation at all?

  1. 35 degrees, 25 degrees
  2. 42 degrees, 29 degrees
  3. 22 degrees, 14 degrees
  4. 15 degrees, 6 degrees

It’s 4: 15 degrees, with opposite cyclic; a measly 6 without! But if it’s shut down and plunked on a hillside with a crane somehow, it is a whopping 42 degrees! (That’s independent of cyclic, of course. Being shut down, there’s no collective raising the effective center of gravity. It’s called the ‘static rollover’ angle.)