Question: At major airports, you will often see varied types of approach lights. Most burn steadily, some flash. On approach to some larger runways, you might see a rapidly moving sequence of lights, similar in effect to the optical illusion of an old fashioned movie marquee. The common term for this is the ‘rabbit’. And those lights move FAST! Just how fast ARE those sequenced flashing lights moving, anyway?
- about 400 knots
- faster than ANY airplane will ever travel, down this low! The speed is about 1600 knots.
- Faster still: anywhere between 1.4 and 2.4 nautical miles per SECOND!
- Warp 3
The answer is number 3. They fire based on a standard 60 Hz cycle. Anywhere from 5 to 21 lights are arranged in a row over a 2400 to (sometimes) 3000 foot distance, firing in sequence from the outer-most to the inner-most fixture. In the ALSF mode, they fire every at every cycle of the 60 Hz line–in the SSALR mode, every other flasher fires on every other cycle. The speed ranges between about 8500 to 9600 fps in the ALSF mode to 11,250 to 14,400 fps in SSALR mode. Though in general, the sequence occurs twice a second, there’s a ‘rest time’ for old Bugs in there, and the actual speed of the rabbit is much faster. (You can see some specs here: http://www.sas.siemens.com/images/manual%20pdf/96a0106.pdf. YOU do the math!) Note: This is for the USA only! Transport Canada systems differ from those in the US.
yes, more…
Subject: Spin History
Question: Who was the first person to ‘figure out’ how to get out of a spin?
- Wilbur Wright, 1912
- Lt. Wilfred Parke, Royal Navy, 1912
- Frederick A. Lindemann, 1914
- Waldo Pepper, 1923
The answer is number 2. Choice 3 is close, as Lindemann was more of a theoretician (and he was a scientific advisor to Winston Churchill in later years, as well as a viscount). However, Parke WAS first (see Curve Ball for the Kaiser: The Unsung Spin Doctor). He enjoyed this distinction for all of two months, however, before he died trying to return to the runway after a low-altitude engine failure. (See? Slay one dragon, get clobbered by another…)
Subject: Gee Whiz
Question: How can you make a turn in an airplane without increasing the vertical g-load beyond 1.0?
- The only way is to make a ‘great circle’ turn. That means straight and level flight, where the turn radius becomes one quarter of the earth’s circumference (though not as some books might say, ‘infinite’).
- using rudder inputs only (and enough opposite aileron to counter any induced roll)
- in a descending turn, where the rate of descent is slowly increasing
- It isn’t possible.
Allowable answers are number 1, 2, and 3. (I’ll be willing to bet that you know several more…)
