Gentlemen (and Ladies) -
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Being an old fart, I have the privilege, and the right, to use a "whizzwheel". And my favorite is the Jeppesen CR-3 type. Yessssss. Actually, mine are "clones" of the Jeppesen originals. AeroProducts copied the CR in the 1970s. The only reason I prefer the AeroProduct model, is that they are white/yellow colors, unlike the original grey/white of the Jeppesen originals. The yellow/white makes them more "readable".
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I have two actually. One is the 6 inch (15 cm) diameter model, which is in my flight bag, the other, the smaller is the 4 inch (10 cm) diameter "pocket size", which fits my shirt pockets. Of course the large one is more accurate, and is better for my waning eyesight (don't worry, I retire in a few months).
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I think I bought them from some US$ 14 or 15.oo back then. A friend pilot in Europe told me that the "Aristo" whiizzwheels were superior. Well, the Aristo was maybe a better quality of material maybe, and certainly higher in price, about 4 or 5 times the price of the Jeppesen standard issue back then.
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I had the pleasure to meet Ray Lahr, back then a UAL DC-8 captain, at a meeting at Mount San Antonio College near Los Angeles, which has an aviation department of excellent reputation, and where he was occupying a position in the academic team. Ray Lahr designed the CR slide rules. He told me that in effect, the CR was "too accurate" to use for some problems in the FAA written tests (ATP and F/E), and that the FAA was then using the USAF E6B type (metal) issue for computations in their performance problems.
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The issue that has been mentioned about the "Ct" recovery coefficient of .8 is correct, but is extremely minor. Besides, my "Aeroproduct" clones, have a choice of .6 through 1.0 included. I fly a Classic 747, and the Ct of .8 seems to be accurate enough. Sorry if my TAS is 487 instead of 485 that I manage to read with my "confuser", but the ATCO of Dakar FIR don't mind if my estimate for the boundary is 04:32 and 17 seconds, rather than 04:32 and 23 seconds.
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Funny is, some of the F/O nerds and geeks who punch numbers (with their fat fingers) on the FMS cannot beat my dexterity and speed of solutions that I derive from my old CR. My US$ 14.98 technology is at least equal to their US$ 14,980.98 FMS contraptions. Sorry for the devaluation...
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So for me - my recommendation, is a large size CR-3 for your exams, and learn to use it, and study how they work. After all, I am sorry if you do confuse IAS and CAS. When I retire in November, I will still keep my little CR in my pocket when I travel, for exchange rates conversions of Pesos, to Dollar or Euros... darn convenient (and impressive) to use a CR to buy a bottle of 50 years old Courvoisier cognac in a store. Makes you almost look like an intellectual (or like there above mentioned, "geek or nerd").
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Sorry, I can't stop getting back at the new generation of future captains, who occasionally might find the destination airport, can even speak Level 6 ICAO jargon, but are sadly limited to Level 1 for spelling on Pprune...
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Happy contrails
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