Honest representation of engine power
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Honest representation of engine power
This is all rather fascinating. I've been involved on a number of occasions in the approval of various small engines in permit-to-fly aeroplanes, and there seems little relationship sometimes between rated power and actual performance.
For example the Simonini Victor II engine quotes 92 hp but seems in an aeroplane to generate only slightly more power than a 65 hp Rotax 582. I found today the engine test data on Simonini's website, at http://www.simonini-flying.com/victor2_eng.htm . On inspection, the test results are stated to have been obtained at 1048mb and +2°C. No wonder the results are so good!
Another example is the 2.2 litre Jabiru, which is sold in the UK by ST Aviation. Their website at http://www.jabiru.co.uk/engndsc.html claims 80hp, yet I recently found the CASA data sheet for the engine at http://www.jabiru.co.uk/engndsc.html which clearly states that the power output is 55.5hp (okay not at the same RPM, but I don't believe that 55hp at 3,100 rpm = 80hp at 3,300 rpm). I can't quite see either how moving an engine from Australia to England increases it's power output by 24.5 hp.
There are plenty of other examples, albeit less obvious - the "60hp"HKS700E ( http://www.ultralight.ca/HKSengine.htm )which has never in an aircraft generated better performance than the "50hp" Rotax 503-2V (http://www.ultralight.ca/rotax.htm)
How on earth is a designer, TP, or certification engineer really supposed to know what they're dealing with in the little aeroplane business any more? Is there anybody I can trust to give me honest engine data? Why do Austrian horses seem so much bigger than Australian or Japanese ones?
Answers on a postcard please to the Isle of Wight rest home for confused certification engineers.
G
For example the Simonini Victor II engine quotes 92 hp but seems in an aeroplane to generate only slightly more power than a 65 hp Rotax 582. I found today the engine test data on Simonini's website, at http://www.simonini-flying.com/victor2_eng.htm . On inspection, the test results are stated to have been obtained at 1048mb and +2°C. No wonder the results are so good!
Another example is the 2.2 litre Jabiru, which is sold in the UK by ST Aviation. Their website at http://www.jabiru.co.uk/engndsc.html claims 80hp, yet I recently found the CASA data sheet for the engine at http://www.jabiru.co.uk/engndsc.html which clearly states that the power output is 55.5hp (okay not at the same RPM, but I don't believe that 55hp at 3,100 rpm = 80hp at 3,300 rpm). I can't quite see either how moving an engine from Australia to England increases it's power output by 24.5 hp.
There are plenty of other examples, albeit less obvious - the "60hp"HKS700E ( http://www.ultralight.ca/HKSengine.htm )which has never in an aircraft generated better performance than the "50hp" Rotax 503-2V (http://www.ultralight.ca/rotax.htm)
How on earth is a designer, TP, or certification engineer really supposed to know what they're dealing with in the little aeroplane business any more? Is there anybody I can trust to give me honest engine data? Why do Austrian horses seem so much bigger than Australian or Japanese ones?
Answers on a postcard please to the Isle of Wight rest home for confused certification engineers.
G
Join Date: Jan 1997
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Genuinely fascinating Genghis and I'm sure what many have 'felt in their water' for years.
I'd be immensely grateful if you could pop it on the Private Forum and, if at all possible, the PFA one.
rob
I'd be immensely grateful if you could pop it on the Private Forum and, if at all possible, the PFA one.
rob
Join Date: Oct 1998
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Gengis
I believe in the world of cars dynomometers (sp?) can be programed to compensate for variations in the temperature and pressure that the test is carried out under to give an equivalent to one taken under ISA conditions. So you could ask engine manufacturers to do the same (unlikely to be helpful) or you could possibly ask the man from you nearest engine tuning house if he has some tables that would give you the correction factors. Or possibly see if a dyno manufacturer would be prepared to let you have a bit of there software.
I believe in the world of cars dynomometers (sp?) can be programed to compensate for variations in the temperature and pressure that the test is carried out under to give an equivalent to one taken under ISA conditions. So you could ask engine manufacturers to do the same (unlikely to be helpful) or you could possibly ask the man from you nearest engine tuning house if he has some tables that would give you the correction factors. Or possibly see if a dyno manufacturer would be prepared to let you have a bit of there software.
