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"Sec. 45.29  Size of marks.
...   (iii) Marks at least 3 inches high may be displayed on an aircraft for
 which an experimental certificate has been issued under Sec. 21.191(d) or
 21.191(g) for operating as an exhibition aircraft or as an amateur-built
 aircraft when the maximum cruising speed of the aircraft does not exceed 180
 knots CAS; and..."

Rick,

Check with the EAA.  They have been trying to convince the FAA to allow all amateur-built aircraft to carry 3-inch numbers.

Additionally, note that the FAA does not define cruise, but my dictionary does:

...4. to fly, drive or sail at a constant speed that permits maximum operating efficiency for sustained travel.

What percent power produces max efficiency above the minimum enroute altitude (MEA)?  You do "cruise" above the MEA, don't you?  And, what is the constant CAS for that power setting?

In my 320, at say 25 squared, I regularly get 191Kts TAS at some reasonable altitude.  My IAS is in the low to mid 170s and I am not "cruising".  This is Pedal-to-the-Metal flying.

Max efficiency is maybe 55% power where the IAS will be significantly less than 180 Kts.

I have 3-inch numbers hidden under the horizontal stab (where does the vertical stab stop and the fuselage begin?), have been surrounded by FAA types, have been to EAA flyins attended by FAA, etc. and I have never been questioned about the placement or size.

Scott Krueger
N92EX

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