* Yellow Arc
: Caution range, which typically can be entered only in a power-on descent.
When the train approaches the end of movement authority - approaching the terminus at Aberystwyth for example - the speedometer display shows a yellow arc
. The driver must brake to keep the needle in the shrinking yellow area, otherwise red will appear on the screen and the computer will take over the braking.
There are also signs of interactions between a central source and the surrounding gas, particularly the yellow arc
of H II emission located above and to the left of the black hole.
Descending out of 10,000 feet, at the bottom of the yellow arc
in a high-performance single or light twin, true airspeeds can be over 200 knots and every 1000-foot drop in altitude drops that number by roughly two percent.
If there is also a yellow arc
in that year, you could be living on a limited income as a student, but if you see a green arc following on in the next year, you might be saving all that money for a round-the-world trip.
IRIS: A white or yellow arc
around the outside of the iris is a sign of hardening of the arteries and a high cholesterol level.
Vaguely remembering the emergency descent procedure, I pushed the nose over, pulled the throttle, dropped the gear and controlled pitch to keep airspeed below the yellow arc
. I managed to notify ATC, who cleared me to descend.
The big Continental in front of me was rumbling along at about 25 squared, still leaned for cruise altitude, and airspeed was well into the indicator's yellow arc
, That's when it got bumpy.
And, as we know, the [V.sub.NE] red-line or never-exceed speed of the aircraft is depicted by a red line on the aircraft airspeed indicator at the top of the yellow arc
. However, it is very important to understand [V.sub.NE] is not an indicated airspeed.
For example, if you're cruising up in the yellow arc
, you should consider at least slowing to at or below [V.sub.a], your aircraft's design maneuvering speed.
I confess: There's a certain satisfaction from pushing the airplane hard, up into its yellow arc
. If you're lucky, you fly something capable of such speeds without much effort, even in the summer or at high altitude, when the air is thinner and indicated airspeeds lower.
You're descending at a relatively high speed in calm air and, since there was no forecast for and little chance of turbulence, you let the airspeed climb into the yellow arc
. Then you hear a buzzing noise.