"Jerry Wass" wrote in message
news
To what standards are today's(and/or yesterdays) A/C engines corrected
to???

I find the older SAE J607--60°F---29.92" Hg 0% humidity
SAE J1349--77°F 29.234"Hg 0%
DIN 68°F 29.92
JIS 77°F 29.234 0%
?? J1995 77°F 29.53 0%
(29.53"Hg = 100KPa )


My guess is that it is the older J607--,but I'd like a 2nd opinion.

Thanks a Whole bunch--Jerry

To the best of my knowledge and recollection, they use International
Standard Atmosphere (ISA) and part of the definition, including 59°F and
29.92"Hg, can be seen at: http://www.pilotsweb.com/wx/w_sense.htm#isa
However, little is stated in the article with regard to humidity except that
the atmosphere can contain a lot of water--which displaces the other gasses.
The figure of 5% was shown somewhere one the page, but was not tied to a
particular temperature.

I was also able to find a an article in Wikipedia:
http://en.wikipedia.org/wiki/Standar...e_and_pressure which
includes a table, about a third of the way down the page. The table
suggests that ISA is based upon 0% humidity--which would not be achieved in
real life.

I do know that the effect of humidity, especially at high temperatures, is
considerable on the takeoff roll and dramatic on climb performance. IIRC,
the reduction in horsepower due to humidity can be around 10%, while the
same amount of humidity would have only a 1% reduction in air density with
regard to the wings.

Considering that climb performance is entirely based on reserve power, above
that required to fly the aircraft, the result can be downright scary!

I have seen articles on the subject, including real numbers usefull for
pre-takeoff planning, but can not find any at the moment.

Peter