Why would one need to know MAP while flying gyro with 915iS ?

Inquiring Mind

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Any reason to know a Manifold Air Pressure value while flying gyro with 915iS and fixed pitch prop ?
Thanks.
 

Greg Vos

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Any reason to know a Manifold Air Pressure value while flying gyro with 915iS and fixed pitch prop ?
Thanks.
On any turbo charged engine it’s good to know your MAP or boost
 

Inquiring Mind

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On any turbo charged engine it’s good to know your MAP or boost
What do I use it for? I can't control the mixture, I can't control the prop pitch, or boost, so what good does knowledge of MAP do to me? I have an indicator onboard, which I have no idea how to use, so do I really need it?
 
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hillberg

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What do I use it for? I can't control the mixture, I can't control the prop pitch, or boost, so what good does knowledge of MAP do to me? I have an indicator onboard, which I have no idea how to use, so do I really need it?
You better learn the limitations of your power plant and MAP or you can over boost the engine and shorten its TBO. or wreck it all together.
 

Greg Vos

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What do I use it for? I can't control the mixture, I can't control the prop pitch, or boost, so what good does knowledge of MAP do to me? I have an indicator onboard, which I have no idea how to use, so do I really need it?
Well if the waste gate or its controller gets stuck and you boost for a period beyond the engines specified times you will hurt the motor, bend the crank if your lucky, or you may find a rod through the piston with overboost.
in a rotax the egt can be left off because as you say you do not have control of mixture, that said it’s good to be mindful of the egt as it’s early warning if something is getting a bit hot....scanning the T’s &P’s is common place in any cockpit ....seeing a MAP going past 44 for even a few seconds will get my full attention ....rotax has specific time allocations for continuous boost and the TCU controls this ....may be in your interest to spend time with an instructor who is rotax schooled and just get some basic knowledge.

in the mean time Google You tube for videos on engines that have been over boosted to see how entertaining it is when it goes south .....and it happens so fast you will be surprised
 

Philbennett

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What do I use it for? I can't control the mixture, I can't control the prop pitch, or boost, so what good does knowledge of MAP do to me? I have an indicator onboard, which I have no idea how to use, so do I really need it?

Short answer given the basics of the aircraft is no you don't need it. Throttle position is all you can do to control the elements others have highlighted.
 

Greg Vos

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Short answer given the basics of the aircraft is no you don't need it. Throttle position is all you can do to control the elements others have highlighted.
Well this is a interesting topic, I teach a student who is working with say an M16 ...RAM.... this pre lift check is quick and informative R= rotor speed , A= airspeed as we run down the runway , M MAP = 35 ....before moving throttle right and to the turbo cos then I want to see it’s reflecting 40 ...this tells me the engine is making power and working
let’s not get confused with engine rpm and MAP, you can have 5550 rpm but no power this is why a MAP gauge is so handy and important
then if you wish to confirm the boost ( that extra 15%) you pull the lever right engage the turbo to max and you want to see the 40MAP ....
we also teach a student to check the gate as part of the preflight ....yet I have met no les than 6 gyropedia instructors who have no clue about this check and why it along with the spring on the gate is so important my last trip to Nepal I was exposed to instructor rated and recomended by the DTA facility he was clueless in this regard too ...but then he was also singing the song of the French gyroperfu a product I denounce with authority 😁....he went on and crashed scribbling a gyro soon afterwards 🙁🙁
 

Philbennett

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Yeah but to be fair you're over thinking it Greg. The 915 will alarm if there is a problem so your process is just cross checking something that A) the ECU is doing and B) you likely detect because the throttle setting isn't delivering the expected performance. As you know I'm not gyropedia apologist but in fairness to the guys that do they are likely to be UK based - and a territory that is in the main ISA conditions. The wider issue for me with the gyropedia is that very many blindly tick all the boxes and go through the motions thinking that is the very thing that keeps them safe, when as we recently discovered it does not.
 

Vance

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What do I use it for? I can't control the mixture, I can't control the prop pitch, or boost, so what good does knowledge of MAP do to me? I have an indicator onboard, which I have no idea how to use, so do I really need it?
I can affect manifold pressure with the throttle.

MAP is a quick way to check that everything is working correctly.

in my opinion based on my experience to assume the waste gate and electronic control systems on a turbocharged engine will work flawlessly is an unreasonable fantasy.
 

XXavier

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Perhaps I can now learn something about the importance of the manifold pressure in a turbocharged engine...
If I understand it correctly, in an 'aspirated' engine, the depression in the intake, at a given rpm, is proportional to the load. That depression is high (the intake pressure is much lower than the atmospheric) when the load is small, and it drops (the intake pressure gets closer to the atmospheric) as the load rises.
But with supercharging continually increasing the intake pressure, is still MAP a measure of the engine load...?
 

Philbennett

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in my opinion based on my experience to assume the waste gate and electronic control systems on a turbocharged engine will work flawlessly is an unreasonable fantasy.
No doubt but the 915 will alarm when it isn't.
 

Vance

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In my opinion based on my experience to assume the all the electronic alarms on a turbocharged engine will work flawlessly is an unreasonable fantasy.

Many people prefer lights and alarms to instruments.

I prefer instruments so I can see a problem developing, have a sense of how urgent the problem is and I can see how a change affects things.

The 915 I flew had panels that I found confusing in an instrument sweep and they prolonged the sweep and reduced the value.

I am sure with more experience I would become more comfortable and less confused.

I would prefer having a MAP instrument on any turbocharged engine and prefer to have MAP on a normally asperated engine.
 
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Philbennett

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OK. In the end 915 generated alarm or MAP out of expected range on a gauge... what you going to do?
 

Philbennett

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Many people prefer lights and alarms to instruments.

I prefer instruments so I can see a problem developing, have a sense of how urgent the problem is and I can see how a change affects things.

The 915 I flew had panels that I found confusing in an instrument sweep and they prolonged the sweep and reduced the value.

I am sure with more experience I would become more comfortable and less confused.
.... and to my point about differences training.... beyond which an alarm is binary. Its on or off. It is an attention getter. As you may know from the POH the 915 pre flight check includes a function check of both lanes that ensure said attention getter is operational.
 

Vance

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Perhaps I can now learn something about the importance of the manifold pressure in a turbocharged engine...
If I understand it correctly, in an 'aspirated' engine, the depression in the intake, at a given rpm, is proportional to the load. That depression is high (the intake pressure is much lower than the atmospheric) when the load is small, and it drops (the intake pressure gets closer to the atmospheric) as the load rises.
But with supercharging continually increasing the intake pressure, is still MAP a measure of the engine load...?
MAP is representative of the power being made by the engine at a particular engine rpm and in my opinion is a better representation than engine rpm alone.

In other words if I was going somewhere I would be more inclined to use MAP and engine rpm than simply picking a particular engine rpm.

With power on landings I find using MAP more consistent than picking an engine rpm.
 

Vance

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OK. In the end 915 generated alarm or MAP out of expected range on a gauge... what you going to do?
Reduce throttle and work to discover the underlying problem if it was high and land if it was low.
 

XXavier

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MAP is representative of the power being made by the engine at a particular engine rpm and in my opinion is a better representation than engine rpm alone.

In other words if I was going somewhere I would be more inclined to use MAP and engine rpm than simply picking a particular engine rpm.

With power on landings I find using MAP more consistent than picking an engine rpm.

Engine load, measured in delivered torque multiplied by rpms = power, so –at the same rpms– torque and power (if in different units, of course...) are different only by a conversion factor.

But I repeat my question:

(...) with supercharging continually increasing the intake pressure, is still MAP a measure of the engine load...?

At a given rpm value, the volume of the air aspirated by the cylinders by unit time is always the same, irrespective of the delivered torque. If the load rises, the torque has to rise too in order to keep the revs under that higher load. The carb responds to the demand for more torque by increasing the rate of fuel flow, and at the same time opening the butterfly to keep the air/fuel ratio more or less constant, and the MAP goes up. That's how the aspirated engine works, or at least that's how I understand it. But in a turbocharged engine, there's an additional factor, with the intake pressure being artificially increased by the turbo...
 
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Inquiring Mind

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In my opinion based on my experience to assume the all the electronic alarms on a turbocharged engine will work flawlessly is an unreasonable fantasy.
Nobody said that. Who's fantasy is this?
With power on landings I find using MAP more consistent than picking an engine rpm.
Are you checking MAP while on final, really?
 

Philbennett

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In the meantime back in the real world. If you've done a proper pre-flight as per the POH then the alarm that monitors such SNAFU's is working. Therefore when the alarm illuminates you follow the appropriate procedure according to the Lane A and/or Lane B alarms.

Otherwise...as I said what you going to do? Apparently you are going to ignore the Lane A/B alarm and work it out manually? OR for some reason better known to the pilot suggesting it - you believe the MAP gauge over the Lane A/B alarms which you pre-flighted and were functional.

Did someone say snag? Now your not a instructor pilot with multi thousand hours, you're a student pilot on a solo and now you have a new opinion and you're over thinking things and the rate of descent is increasing and you pancake in and die.
 
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