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1. 07:18 AM - 914 High Altitude Performance (h&jeuropa)
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| Subject: | 914 High Altitude Performance |
We recently did a flight at a Density Altitude of 15000 ft. We were unable to
maintain 30 in manifold pressure, the fuel flow was about 6.4 gph and the throttle
position was 100%. We subsequently adjusted the wastegate cable less than
1 turn and replaced all the spring style clamps on our airbox pressure and manifold
pressure instrumentation hoses with wraps of safety wire and now we easily
get 30 in manifold pressure with fuel flow of 5.5 gph and throttle position
around 70%.
When looking into this, we referred to the 914 performance charts found in chapter
5 of the Operators Manual and the critical flying altitude in chapter 2.
Chapter 2 states that continuous performance manifold pressure is available up
to 16000 feet when operated at ISA temperature and pressure. Yet the Performance
graph for non-standard conditions, shows when the temperature difference
from standard condition is 0 (so standard ISA conditions) the power drops from
74kw at SL to 66 kw at 16000 ft. This seems to conflict with the critical altitude
statement.
And we have a copy of an early 914 Operators Manual (1996 05 10) where the same
chart shows constant power at 0 deg difference up to 16000 ft. It also shows
the same example as the current chart, Max continuous power at 10000ft, and the
result is 74.9 kw versus the current chart that results in 72 kw.
Just looking for an explanation of the charts and definition of critical altitude.
Thanks
Jim & Heather
Europa XS
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=444658#444658
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