Today's Message Index:
----------------------
1. 02:32 AM - Re: Water Coolant Sensor location? (Remi Guerner)
2. 08:49 AM - Re: Knowing the actual fuel level? (h&jeuropa)
3. 11:13 AM - David Joyce (goff)
4. 04:39 PM - Re: Re: Water Coolant Sensor location? (Timward)
5. 04:48 PM - Re: Re: Water Coolant Sensor location? (Martin Tuck)
Message 1
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| Subject: | Re: Water Coolant Sensor location? |
In spite of what Rotax say in their Manuals, I do not think that monitoring coolant
temperature is necessary. This is why:
1. The coolant is heated by the cylinder heads. So obviously coolant temperature
is always below cylinder head temperature.
2. Conventional water based coolant boils at 120C at the 1.2 bar pressure, at sea
level.
3. Anytime the hottest cylinder CHT exceeds 120C, there will be at least some local
boiling.
3.1. Then, if the engine is running at cruise RPM or more, the water pump insures
a good flow through the cylinder heads, the bubbles are pushed downstream to
the cooler and condense, so there is no boiling over.
3.2. If the engine is at idle on the ground, while you are waiting for your take
off clearance, then it will boil over. Moreover, as soon as CHT reaches 110C,
you must either shut down the engine or take off quickly. If you wait a few
more minutes and let the CHT reach 115C, then the only choice is to take off immediately.
Then the CHT will decrease instantly. If you shut down at this point,
then the heat transferred from the hot engine to the coolant will make it
to exceed its boiling point and you are facing a big mess.
So the only advantage of monitoring the coolant temperature would be to allow the
CHT to slightly exceed 120C, for example during a full power climb in very
hot conditions, while the coolant temp would stay slightly below 120C. It seems
to me this is a very marginal and risky advantage.
So in my opinion, monitoring the CHT of the hottest cylinder and considering the
redline is 110C on the ground and 120C in flight is good enough. This is especially
true on the Europa where cooling is very good in flight but very marginal
on the ground.
Remi Guerner
F-PGKL, XS Monowheel, 912ULS, 1195 hours
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=439699#439699
Message 2
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| Subject: | Re: Knowing the actual fuel level? |
We have a mono which means fuel quantity measuring devices will indicate differently
depending on whether the aircraft is in level flight attitude or ground
attitude. Adds a bit of complexity to the problem!
We rely most on the fuel computer built into our GRT EIS and EFIS. This has two
separate FlowScan transducers, one for in and one for return. It has proven
to be accurate, probably within 1/2 gallon. It's hard to know how accurate it
is, since it is difficult to measure fuel quantity accurately with a sight
gauge.
We have a sight gauge positioned on the rear wall of the cockpit module and connected
to the port side tank water drain. This is calibrated for ground attitude
and we use it when refueling. We compare it to the fuel computer. Due to
it's location, it is not visible in flight.
Andrew Sarangan suggested an alternative to a sight gauge. We don't know what the
current status of this novel idea is. Here is the thread:
http://forums.matronics.com/viewtopic.php?t=103987&highlight=fuel+level
In flight we use two differential pressure sensors, one on each tank drain. The
transducers are Freescale MPXV4006DP. They output 0-5 volts which our EIS accepts
as aux inputs. Our GRT EFIS has a tank calibration table so we account
for the shape of the tank there and we did that calibration in level flight attitude.
We have each sensor calibrated from 0 - 3 gal. So each will show the
amount of fuel in its 3 gal side. When both are at 3 gal, we then display both
sensors as having 6 gal and they change together. When we have less than
6 gal on board, we just add the amount each shows. We ignore the fuel quantity
indications from these sensors when on the ground!
This system works pretty well. We are confident enough to use fuel out of the
port tank until no more than 1 gallon remains. We then switch to the stbd tank
and complete the flight. Of course when low on fuel, we monitor the fuel computer
and the differential fuel pressure closely.
Ira, we found that with a forward facing tank vent on the belly of the aircraft,
there is enough ram air pressure that we had to use differential transducers
connected to the tank vent. We tried differential sensors vented to ambient
pressure and found large errors.
Jim & Heather
N241BW
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=439702#439702
Message 3
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David,
Could you give me a link to download your complete article on ditching?
Thanks in advance ,
Goff
Goff Moore
G-CHOX
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=439705#439705
Message 4
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| Subject: | Re: Water Coolant Sensor location? |
Absolutely agree with you Remi.
Tim
Tim Ward
12 Waiwetu Street
Fendalton,
Christchurch, 8052
New Zealand.
ward.t@xtra.co.nz
Ph 64 3 3515166
Mob 0210640221
> On 21/03/2015, at 10:31 pm, Remi Guerner <air.guerner@orange.fr> wrote:
>
>
> In spite of what Rotax say in their Manuals, I do not think that monitoring coolant
temperature is necessary. This is why:
> 1. The coolant is heated by the cylinder heads. So obviously coolant temperature
is always below cylinder head temperature.
> 2. Conventional water based coolant boils at 120C at the 1.2 bar pressure, at
sea level.
> 3. Anytime the hottest cylinder CHT exceeds 120C, there will be at least some
local boiling.
> 3.1. Then, if the engine is running at cruise RPM or more, the water pump insures
a good flow through the cylinder heads, the bubbles are pushed downstream
to the cooler and condense, so there is no boiling over.
> 3.2. If the engine is at idle on the ground, while you are waiting for your take
off clearance, then it will boil over. Moreover, as soon as CHT reaches 110C,
you must either shut down the engine or take off quickly. If you wait a few
more minutes and let the CHT reach 115C, then the only choice is to take off
immediately. Then the CHT will decrease instantly. If you shut down at this point,
then the heat transferred from the hot engine to the coolant will make it
to exceed its boiling point and you are facing a big mess.
> So the only advantage of monitoring the coolant temperature would be to allow
the CHT to slightly exceed 120C, for example during a full power climb in very
hot conditions, while the coolant temp would stay slightly below 120C. It seems
to me this is a very marginal and risky advantage.
> So in my opinion, monitoring the CHT of the hottest cylinder and considering
the redline is 110C on the ground and 120C in flight is good enough. This is especially
true on the Europa where cooling is very good in flight but very marginal
on the ground.
> Remi Guerner
> F-PGKL, XS Monowheel, 912ULS, 1195 hours
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=439699#439699
>
>
>
>
>
>
>
>
>
>
Message 5
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| Subject: | Re: Water Coolant Sensor location? |
I have done without a coolant temp for years so I'm inclined to agree. I'm also
tired of looking at at a row of blanks for coolant temp on my EIS. Just looking
to get a reading on the display.
Martin
Sent from my iPad
> On Mar 21, 2015, at 6:38 PM, Timward <ward.t@xtra.co.nz> wrote:
>
>
> Absolutely agree with you Remi.
> Tim
>
> Tim Ward
> 12 Waiwetu Street
> Fendalton,
> Christchurch, 8052
> New Zealand.
>
> ward.t@xtra.co.nz
>
> Ph 64 3 3515166
> Mob 0210640221
>
>
>> On 21/03/2015, at 10:31 pm, Remi Guerner <air.guerner@orange.fr> wrote:
>>
>>
>> In spite of what Rotax say in their Manuals, I do not think that monitoring
coolant temperature is necessary. This is why:
>> 1. The coolant is heated by the cylinder heads. So obviously coolant temperature
is always below cylinder head temperature.
>> 2. Conventional water based coolant boils at 120C at the 1.2 bar pressure, at
sea level.
>> 3. Anytime the hottest cylinder CHT exceeds 120C, there will be at least some
local boiling.
>> 3.1. Then, if the engine is running at cruise RPM or more, the water pump insures
a good flow through the cylinder heads, the bubbles are pushed downstream
to the cooler and condense, so there is no boiling over.
>> 3.2. If the engine is at idle on the ground, while you are waiting for your
take off clearance, then it will boil over. Moreover, as soon as CHT reaches 110C,
you must either shut down the engine or take off quickly. If you wait a few
more minutes and let the CHT reach 115C, then the only choice is to take off
immediately. Then the CHT will decrease instantly. If you shut down at this
point, then the heat transferred from the hot engine to the coolant will make
it to exceed its boiling point and you are facing a big mess.
>> So the only advantage of monitoring the coolant temperature would be to allow
the CHT to slightly exceed 120C, for example during a full power climb in very
hot conditions, while the coolant temp would stay slightly below 120C. It seems
to me this is a very marginal and risky advantage.
>> So in my opinion, monitoring the CHT of the hottest cylinder and considering
the redline is 110C on the ground and 120C in flight is good enough. This is
especially true on the Europa where cooling is very good in flight but very marginal
on the ground.
>> Remi Guerner
>> F-PGKL, XS Monowheel, 912ULS, 1195 hours
>>
>>
>>
>>
>> Read this topic online here:
>>
>> http://forums.matronics.com/viewtopic.php?p=439699#439699
>
>
>
>
>
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