Piston Engine Questions
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Piston Engine Questions
Some questions from a few discussions I've overheard in the hangar recently:
1. Idle Fuel Flow
What idle fuel flow do you estimate on your particular aircraft? (I'm talking typical GA aircrafts here). What difference would you say that maximum leaning give you during idle. Please state what engine you are referring to as I assume there will be big differences depending on whether carburated, fuel injected, engine size etc as well as individual differences.
2. Dirty prop static run up RPM, (fixed pitch)
If your prop is extremely dirty from smashed bugs on the leading edge. During a static run up, would you see a rpm that is:
a) lower, due to increased drag caused by the rough leading edge.
b) higher, due to less thrust (lift) being produced from the airfoil and thus less induced drag.
c) no difference
(Sounds like some exam question
)
3. RPM vs Manifold Pressure during Take-Off roll.
I'm currently flying three different constant speed prop aircrafts. Upon power application for take-off and in the subsequent take-off roll they all behave significantly different from each other (and in fact, they are significantly different).
Aircraft A: a normal aspirated 180hp Lycoming AEIO360 (i.e aerobatic engine,). During the static run-up the rpm reaches the red line value at a Manifold Pressure of about 20". The remaining power increase up to 30ish only causes the pitch to go from fine to medium. RPM stays at red line during acceleration.
Aircraft B: a normal aspirated Rotax 912. During the static run up the rpm reaches approximately 2100rpm (red line 2385) at full thottle. During acceleration the rpm increases to reach red line approximately at rotation speed from where it remains constant.
Aircraft C: a turbocharged Rotax 914. The rpm and MP follow each other and reaches their respective max values at more or less the same time. (i.e full thottle and red line rpm).
I do realise what kind of technical differences that causes these differences but that's not my question. I just want a comparison between different aircrafts and to have an idea of what to expect from different kinds of aircrafts/engines.
If those of you flying whith constant speed props would like to submit how your aircraft responds including what kind of engine, prop etc I would be delighted.
1. Idle Fuel Flow
What idle fuel flow do you estimate on your particular aircraft? (I'm talking typical GA aircrafts here). What difference would you say that maximum leaning give you during idle. Please state what engine you are referring to as I assume there will be big differences depending on whether carburated, fuel injected, engine size etc as well as individual differences.
2. Dirty prop static run up RPM, (fixed pitch)
If your prop is extremely dirty from smashed bugs on the leading edge. During a static run up, would you see a rpm that is:
a) lower, due to increased drag caused by the rough leading edge.
b) higher, due to less thrust (lift) being produced from the airfoil and thus less induced drag.
c) no difference
(Sounds like some exam question
)3. RPM vs Manifold Pressure during Take-Off roll.
I'm currently flying three different constant speed prop aircrafts. Upon power application for take-off and in the subsequent take-off roll they all behave significantly different from each other (and in fact, they are significantly different).
Aircraft A: a normal aspirated 180hp Lycoming AEIO360 (i.e aerobatic engine,). During the static run-up the rpm reaches the red line value at a Manifold Pressure of about 20". The remaining power increase up to 30ish only causes the pitch to go from fine to medium. RPM stays at red line during acceleration.
Aircraft B: a normal aspirated Rotax 912. During the static run up the rpm reaches approximately 2100rpm (red line 2385) at full thottle. During acceleration the rpm increases to reach red line approximately at rotation speed from where it remains constant.
Aircraft C: a turbocharged Rotax 914. The rpm and MP follow each other and reaches their respective max values at more or less the same time. (i.e full thottle and red line rpm).
I do realise what kind of technical differences that causes these differences but that's not my question. I just want a comparison between different aircrafts and to have an idea of what to expect from different kinds of aircrafts/engines.
If those of you flying whith constant speed props would like to submit how your aircraft responds including what kind of engine, prop etc I would be delighted.
a normal aspirated Rotax 912. During the static run up the rpm reaches approximately 2100rpm (red line 2385) at full thottle
As for the manifold pressure: I can't remember ever seeing such a gauge in a Rotax-powered plane, though of course it is not impossible to install.
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Idle Fuel Flow on my 912ULS is about 3lph.
In B I assume you are using prop RPM which is very unusual. A Rotax 912 has a red line at 5800 RPM. If you have a prop controller similar to a SCS1 this will keep constant engine RPM my adjusting the prop. You will probably get around 5300 max static with the prop full fine which will rise rapidly to 5750 which will then remain constant until you take the prop out of T/O mode.
Rod1
In B I assume you are using prop RPM which is very unusual. A Rotax 912 has a red line at 5800 RPM. If you have a prop controller similar to a SCS1 this will keep constant engine RPM my adjusting the prop. You will probably get around 5300 max static with the prop full fine which will rise rapidly to 5750 which will then remain constant until you take the prop out of T/O mode.
Rod1
Last edited by Rod1; 26th Oct 2011 at 16:56.
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C172R with IO-360L2A, about 2 USG per hour on 1000 RPM idle leaned in accordance with POH.
Not sure (don't think) a contaminated prop will show much difference at full power on a static run-up.
Not sure (don't think) a contaminated prop will show much difference at full power on a static run-up.
