"John Ross" wrote in message
...
As I understand it, in order to fly (legally) above 17,500 feet, the
pilot must be instrument-rated and file an IFR flight plan.

In sunny, cloudless conditions can you file an IFR flight plan and go
over 17,500 if your plane (like my Pitts 12) is not equipped to fly at
night or in bad weather, i.e. no lights or gyros?

Class A airspace is that airspace over 18,000 feet. Several pertinent
regulations are quoted below:

§ 61.3 Requirement for certificates, ratings, and authorizations.

(e) Instrument rating. No person may act as pilot in command of a civil
aircraft under IFR or in weather conditions less than the minimums
prescribed for VFR flight unless that person holds:
(1) The appropriate aircraft category, class, type (if required), and
instrument rating on that person's pilot certificate for any airplane,
helicopter, or powered-lift being flown;

(2) An airline transport pilot certificate with the appropriate aircraft
category, class, and type rating (if required) for the aircraft being flown;

(3) For a glider, a pilot certificate with a glider category rating and an
airplane instrument rating; or

(4) For an airship, a commercial pilot certificate with a lighter-than-air
category rating and airship class rating.

§ 71.31 Class A airspace.
The airspace descriptions contained in §71.33 and the routes contained in
subpart A of FAA Order 7400.9L (incorporated by reference, see §71.1) are
designated as Class A airspace within which all pilots and aircraft are
subject to the rating requirements, operating rules, and equipment
requirements of part 91 of this chapter.

§ 71.33 Class A airspace areas.
(a) That airspace of the United States, including that airspace overlying
the waters within 12 nautical miles of the coast of the 48 contiguous
States, from 18,000 feet MSL to and including FL600 excluding the states of
Alaska and Hawaii, Santa Barbara Island, Farallon Island, and the airspace
south of latitude 25°04'00" North.

(b) That airspace of the State of Alaska, including that airspace overlying
the waters within 12 nautical miles of the coast, from 18,000 feet MSL to
and including FL600 but not including the airspace less than 1,500 feet
above the surface of the earth and the Alaska Peninsula west of longitude
160°00'00" West.

(c) The airspace areas listed as offshore airspace areas in subpart A of FAA
Order 7400.9L (incorporated by reference, see §71.1) that are designated in
international airspace within areas of domestic radio navigational signal or
ATC radar coverage, and within which domestic ATC procedures are applied.

§ 91.135 Operations in Class A airspace.
Except as provided in paragraph (d) of this section, each person operating
an aircraft in Class A airspace must conduct that operation under instrument
flight rules (IFR) and in compliance with the following:

(a) Clearance. Operations may be conducted only under an ATC clearance
received prior to entering the airspace.

(b) Communications. Unless otherwise authorized by ATC, each aircraft
operating in Class A airspace must be equipped with a two-way radio capable
of communicating with ATC on a frequency assigned by ATC. Each pilot must
maintain two-way radio communications with ATC while operating in Class A
airspace.

(c) Transponder requirement. Unless otherwise authorized by ATC, no person
may operate an aircraft within Class A airspace unless that aircraft is
equipped with the applicable equipment specified in §91.215.

(d) ATC authorizations. An operator may deviate from any provision of this
section under the provisions of an ATC authorization issued by the ATC
facility having jurisdiction of the airspace concerned. In the case of an
inoperative transponder, ATC may immediately approve an operation within a
Class A airspace area allowing flight to continue, if desired, to the
airport of ultimate destination, including any intermediate stops, or to
proceed to a place where suitable repairs can be made, or both. Requests for
deviation from any provision of this section must be submitted in writing,
at least 4 days before the proposed operation. ATC may authorize a deviation
on a continuing basis or for an individual flight.

[Doc. No. 24458, 56 FR 65659, Dec. 17, 1991]

§ 91.205 Powered civil aircraft with standard category U.S. airworthiness
certificates: Instrument and equipment requirements.

(d) Instrument flight rules. For IFR flight, the following instruments and
equipment are required:

(1) Instruments and equipment specified in paragraph (b) of this section,
and, for night flight, instruments and equipment specified in paragraph (c)
of this section.

(2) Two-way radio communications system and navigational equipment
appropriate to the ground facilities to be used.

(3) Gyroscopic rate-of-turn indicator, except on the following aircraft:

(i) Airplanes with a third attitude instrument system usable through flight
attitudes of 360 degrees of pitch and roll and installed in accordance with
the instrument requirements prescribed in §121.305(j) of this chapter; and

(ii) Rotorcraft with a third attitude instrument system usable through
flight attitudes of ±80 degrees of pitch and ±120 degrees of roll and
installed in accordance with §29.1303(g) of this chapter.

(4) Slip-skid indicator.

(5) Sensitive altimeter adjustable for barometric pressure.

(6) A clock displaying hours, minutes, and seconds with a sweep-second
pointer or digital presentation.

(7) Generator or alternator of adequate capacity.

(8) Gyroscopic pitch and bank indicator (artificial horizon).

(9) Gyroscopic direction indicator (directional gyro or equivalent).

(e) Flight at and above 24,000 ft. MSL (FL 240). If VOR navigational
equipment is required under paragraph (d)(2) of this section, no person may
operate a U.S.-registered civil aircraft within the 50 states and the
District of Columbia at or above FL 240 unless that aircraft is equipped
with approved distance measuring equipment (DME). When DME required by this
paragraph fails at and above FL 240, the pilot in command of the aircraft
shall notify ATC immediately, and then may continue operations at and above
FL 240 to the next airport of intended landing at which repairs or
replacement of the equipment can be made.

(f) Category II operations. The requirements for Category II operations are
the instruments and equipment specified in-

(1) Paragraph (d) of this section; and

(2) Appendix A to this part.

(g) Category III operations. The instruments and equipment required for
Category III operations are specified in paragraph (d) of this section.

(h) Exclusions. Paragraphs (f) and (g) of this section do not apply to
operations conducted by a holder of a certificate issued under part 121 or
part 135 of this chapter.

§ 91.215 ATC transponder and altitude reporting equipment and use.

(a) All airspace: U.S.-registered civil aircraft. For operations not
conducted under part 121 or 135 of this chapter, ATC transponder equipment
installed must meet the performance and environmental requirements of any
class of TSO-C74b (Mode A) or any class of TSO-C74c (Mode A with altitude
reporting capability) as appropriate, or the appropriate class of TSO-C112
(Mode S).

(b) All airspace. Unless otherwise authorized or directed by ATC, no person
may operate an aircraft in the airspace described in paragraphs (b)(1)
through (b)(5) of this section, unless that aircraft is equipped with an
operable coded radar beacon transponder having either Mode 3/A 4096 code
capability, replying to Mode 3/A interrogations with the code specified by
ATC, or a Mode S capability, replying to Mode 3/A interrogations with the
code specified by ATC and intermode and Mode S interrogations in accordance
with the applicable provisions specified in TSO C-112, and that aircraft is
equipped with automatic pressure altitude reporting equipment having a Mode
C capability that automatically replies to Mode C interrogations by
transmitting pressure altitude information in 100-foot increments. This
requirement applies-

(1) All aircraft. In Class A, Class B, and Class C airspace areas;

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OK, so what does all this mean? In the United States, unless you have
special permission or meet certain exceptions, you and your aircraft have to
be certified for IFR and on an IFR flight plan in order to fly above 18,000
feet MSL (not FL 180). Only one transponder is required. You must have DME
if you are flying using VOR radio beacons above FL 240. There are no
exceptions for sunny, cloudless days.