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Manifold Pressure Gauge

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carl(at)flyers.freeserve.
Guest

Posted: Wed Sep 03, 2008 1:02 pm Post subject: Manifold Pressure Gauge

I am just filling in the LAA form to change our propeller (from a fixed 

pitch to a CS version - Woodcomp/ Smart Avionics controller). The engine is 

a Rotax 912 UL 80hp.



The LAA form says that the installation of a manifold pressure gauge is 

mandatory. Anyone know why?



 Its probably a dumb question but I dont understand the point of monitoring 

manifold pressure on a normal engine. I always thought it was more relevant 

to turbocharged engines.



Also where does one take the pressure takeoff on the engine - I would guess 

the balancing pipe between the carburettors - is there a mod required on the 

engine?



Thanks for the explanation in advance.



Carl Pattinson

G-LABS



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ptag.dev(at)tiscali.co.uk
Guest

Posted: Wed Sep 03, 2008 2:06 pm Post subject: Manifold Pressure Gauge

Hi! Carl

Don't know where you take it off on the 912 UL but the 914 has a sensor

already plumbed in .

You need the manifold pressure to know how much power you are applying (

you could be labouring the engine, since the prop is controlling the RPM

the throttle becomes the power applicator. I had this difficulty with

the 3300 Jabiru because they wouldn't give me MP/power/RPM/

ambient/altitude graphs I never knew where the engine was loaded until

many hours experimenting with fuel usage. Of course the Rotax is geared

so the RPM is still more complex.

Usually on a direct drive the rule of thumb is to run "squared" = 24" MP

to 2,400 Engine Rpm, at least in the initial stages of experimentation.

Regards

Bob Harrison G-PTAG.



--

frans(at)paardnatuurlijk.
Guest

Posted: Wed Sep 03, 2008 2:06 pm Post subject: Manifold Pressure Gauge

Carl Pattinson wrote:

 	  Quote: 	
		   

 <carl(at)flyers.freeserve.co.uk>

 

 I am just filling in the LAA form to change our propeller (from a fixed

 pitch to a CS version - Woodcomp/ Smart Avionics controller). The engine

 is a Rotax 912 UL 80hp.

 

 The LAA form says that the installation of a manifold pressure gauge is

 mandatory. Anyone know why?


	


A CS prop keeps the rotation speed constant (hence the name Constant

Speed prop). The RMP gauge doesn't tell you the engine power anymore, it

shows just the prop setting. If you fly with a certain rpm, and throttle

back, nothing will change on your rpm gauge as the prop will keep the

rpm constant. Hence you won't notice anything as the engine looses power

for whatever reason. However, engine power can be determined by looking

at the manifold pressure. It is close to ambient pressure if the

throttle is wide open, and it will be showing a vacuum at idle, and of

course anything in between.



Frans

terrys(at)cisco.com
Guest

Posted: Wed Sep 03, 2008 2:07 pm Post subject: Manifold Pressure Gauge

Hi Carl,



With a fixed pitch prop, you can get a relative indication of power

level from the engine rpm.  So on a Cessna 152, your standard procedure

might be to pull the power back to 1500 rpm abeam the numbers on down

wind.  With a constant speed prop, the rpm will be held constant over a

wide range of power settings, so the standard measure of power is

manifold pressure (although we also use fuel flow often).  So on our

Europa I would normally pull the power back to 15 inches abeam the

numbers.



Regards,

Terry Seaver

--

wooburnaviation(at)google
Guest

Posted: Wed Sep 03, 2008 2:38 pm Post subject: Manifold Pressure Gauge

If you have a constant speed controller, and there is a loss of power in the engine ( for example from carb ice), the RPM will remain constant ( within the limits of the prop/CS system) as the prop will fine off.

   

 The simple way to tell what power the engine is producing, if a power loss occours, is via manifold pressure gauge.



 

 On 03/09/2008, Carl Pattinson <carl(at)flyers.freeserve.co.uk (carl(at)flyers.freeserve.co.uk)> wrote: [quote]--> Europa-List message posted by: "Carl Pattinson" <carl(at)flyers.freeserve.co.uk (carl(at)flyers.freeserve.co.uk)>

 

I am just filling in the LAA form to change our propeller (from a fixed pitch to a CS version - Woodcomp/ Smart Avionics controller). The engine is a Rotax 912 UL 80hp.



The LAA form says that the installation of a manifold pressure gauge is mandatory. Anyone know why?

 

Its probably a dumb question but I dont understand the point of monitoring manifold pressure on a normal engine. I always thought it was more relevant to turbocharged engines.



Also where does one take the pressure takeoff on the engine - I would guess the balancing pipe between the carburettors - is there a mod required on the engine?

 

Thanks for the explanation in advance.



Carl Pattinson

G-LABS



_______________________________________

No viruses found in this outgoing message

Scanned by iolo AntiVirus 1.5.4.5

 

[b]

r.collings(at)onetel.net
Guest

Posted: Thu Sep 04, 2008 1:56 am Post subject: Manifold Pressure Gauge

Carl Hi. Its not a dumb question at all, but one that you will have answered 

to when you have completed the PPL licence endorsement cause for complexes 

aircraft, i.e., those fitted with a variable pitch prop!You may already this 

because of the mono's retractable undercarriage, but a couple of hours spent 

under instruction in a complex single would be money well spent.

Regards Richard

---

raimo.toivio(at)rwm.fi
Guest

Posted: Thu Sep 04, 2008 11:50 am Post subject: Manifold Pressure Gauge

I am looking for a very small MAP gauge - digital or analogical.

Does anybody have a tip?



Ideal would be a CS prop controller WITH integrated gauge

but there obviously does not exist any. 



Raimo from Finland

OH-XRT

---

jeff(at)rmmm.net
Guest

Posted: Thu Sep 04, 2008 12:24 pm Post subject: Manifold Pressure Gauge

Raimo,

I don't know about the gauge but I couldn't help noticing your  

beautiful Europa in this months EAA Sport Aviation. Congratulations on  

a great looking plane and thanks for some fine recognition of our  

plane.

Jeff Roberts,

USA

A258 - N128LJ / Gold Rush 150 hours and climbing slowly.



On Sep 4, 2008, at 3:05 PM, Raimo Toivio wrote:



[quote] 



 I am looking for a very small MAP gauge - digital or analogical.

 Does anybody have a tip?



 Ideal would be a CS prop controller WITH integrated gauge

 but there obviously does not exist any.



 Raimo from Finland

 OH-XRT

 ---

kheindl(at)msn.com
Guest

Posted: Thu Sep 04, 2008 12:39 pm Post subject: Manifold Pressure Gauge

Raimo C

  

 The CS1 controller from Smart Avionics C displays the m. pressure C if you have the optional pressure switch . I believe it is 50 punds.

 Karl



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[quote] From: raimo.toivio(at)rwm.fi

 To: europa-list(at)matronics.com

 Subject: Re: Manifold Pressure Gauge

 Date: Thu C 4 Sep 2008 23:05:55 +0300

 

 --> Europa-List message posted by: "Raimo Toivio" <raimo.toivio(at)rwm.fi>

 

 I am looking for a very small MAP gauge - digital or analogical.

 Does anybody have a tip?

 

 Ideal would be a CS prop controller WITH integrated gauge

 but there obviously does not exist any. 

 

 Raimo from Finland

 OH-XRT

 ---

kheindl(at)msn.com
Guest

Posted: Thu Sep 04, 2008 12:39 pm Post subject: Manifold Pressure Gauge

Raimo C                     I meant POUNDS

  

 The CS1 controller from Smart Avionics C displays the m. pressure C if you have the optional pressure switch . I believe it is 50 punds.

 Karl



<html><div></div></html>



[quote] From: raimo.toivio(at)rwm.fi

 To: europa-list(at)matronics.com

 Subject: Re: Manifold Pressure Gauge

 Date: Thu C 4 Sep 2008 23:05:55 +0300

 

 --> Europa-List message posted by: "Raimo Toivio" <raimo.toivio(at)rwm.fi>

 

 I am looking for a very small MAP gauge - digital or analogical.

 Does anybody have a tip?

 

 Ideal would be a CS prop controller WITH integrated gauge

 but there obviously does not exist any. 

 

 Raimo from Finland

 OH-XRT

 ---

raimo.toivio(at)rwm.fi
Guest

Posted: Fri Sep 05, 2008 4:22 am Post subject: Manifold Pressure Gauge

Jeff,



thank you for your beautiful words - your statement made good for my hearth.



I will stop working just now, drive to the airport (EFTP), go airborne and finally

test my adjustable poor man´s wing leveller (Trio ap will be installed next winter).

That is a rubber string with a hook. One end is fitted to the stick and when flying

alone hooked end is in the gear slot (that must take off before landing!).



Raimo from Finland

OH-XRT



do not archive

---

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