h&jeuropa
Joined: 07 Nov 2006
Posts: 645
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 Posted: Sat Jul 11, 2015 6:17 am Post subject: 914 High Altitude Performance |
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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
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