helinut wrote:Harvard ll were also made in Canada the IV was post war and I believe it has to do with the tail wheel strut.
per the TCDS
Prior to civil certification,
it must be ascertained that Harvard aircraft manufactured in the United States conform to the type design. Some of the known deviations from the original configuration are discussed as
follows:
(a) The mixture control must be reworked to standard American system, that is "lean-aft, Rich-forward".
A conversion to exact AT-6 system would be acceptable. Any other system would have to be evaluated.
(b) The long exhaust stack configuration should be modified to the AT-6 system.
Utilization of winterized stack would require evaluation with respect to:
(1) Carbon monoxide content in the cockpit from both the fresh air system, heat exchanger within the
stack and the stack proper.
(2) Detrimental temperature effects on the fuselage skin due to the proximity of the stack to the fuselage
as well as possible adverse exhaust back pressure.
(3) Determination that system was United States manufactured inasmuch as a foreign built unit would not
be eligible for approval.
(c) The use of Pratt & Whitney S3H1 engine is acceptable with Item 1 propeller.
(d) The acceptability of engine accessories must be determined. In this regard, Technical Order 00-25-29
"Maintenance Interchangeability Cross Reference Charts" may be utilized as a guide.
(e) The use of a foreign manufactured landing gear is not considered acceptable, and therefore must be
replaced by an acceptable gear manufactured in the United States.
(f) The landing gear fairing and associated attachment hardware must be installed.
(g) The forward control stick has a four inch hand grip which differs from the standard straight stick
installation. If clearance from the structure appears adequate this may be considered acceptable.
(h) Electrical system deviations from the approved type design data must be appropriately changed and adjusted
satisfactorily.
(i) Airspeed flap speed and cylinder head gage limits must be incorporated as in the AT-6 aircraft.
Other existing difference must be satisfactorily resolved with the local FAA Engineering Office prior to
certification.