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PostPosted: Wed Oct 19, 2011 8:20 pm 
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Anyone have any pros or cons on the use of carb heat in a Beaver? Have always been told to use a little and always keep the inlet temp in the green if the instrument is accurate. CP told me today not to use it unless there is a drop in MP and then only till MP is restored.


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PostPosted: Wed Oct 19, 2011 8:58 pm 
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Tell your Chief Pilot to read the manual on engine operation before he gives you advise on how to use the Carb heat

Beechnut



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PostPosted: Wed Oct 19, 2011 9:35 pm 
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Ya, well, I've read it too and chased the inlet temp with heat today and experienced the worst case of carb ice I ever had. Almost put me back on the water after loosing 800'. His reason was that on a day like today, I was making carb ice with heat causing it to run too rich. Have a fair bit of DHC-2 time but have never flown with the temps and conditions experienced today. It took alot of heat to keep the inlet temp up and caught it once earlier in the day and all was well. Watched it like a hawk on the next trip. MP started down and had almost all carb heat on by that time and lost power to 22". Loaded and down I went. Wouldn't clear till I was just about to touch the trees and it didn't clear totally but kept me level enough to make the water. CP has over 35K for hours which consists mostly of radial time. Says he never uses carb heat in a Beaver unless there is a drop in MP or in cold temps to develop take off power.


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PostPosted: Wed Oct 19, 2011 9:43 pm 
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Once again,read the manual


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PostPosted: Thu Oct 20, 2011 7:33 am 
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I was also always told to keep a little on all the time and keep it around 4deg on the guage. But then an AME with over 10k hrs flying on -2 told me that it should only be on when ice is detected and running rough. His thought was that the tradeoff in power vs. the gain in heat through the carb was simply not worth it in normal cruise. is this an old school vs. new school thought?


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PostPosted: Thu Oct 20, 2011 4:41 pm 
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What your describig is not normal with the use of carb heat.Sounds to me; that your plane has a major exhaust leak inside the carb heat shroud around the exhaust pipes. I always used full cold in the summer months , but as the temps got colder; the use of carb heat is as it says in the manual. I think it says to operate with the carb heat gauge between 0 deg C and +4 C.
Kind of an old school rule of thumb: if you don't trust the gauge, or if its US, apply carb heat to give you MP reduction of 1 inch.
in extreme cold: there is a chart for max TO MP. You can't use 36.5 " MP.
The engine is there to look after YOU. And you??????


BH



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PostPosted: Thu Oct 20, 2011 4:44 pm 
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WTF

Its not old school read the Manual Guys



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PostPosted: Fri Oct 21, 2011 7:20 am 
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The problem with clearing carb ice in a beaver, is that you throw chunks of ice through the super charger blades and wreck them after a while. It sounds like there is a problem with yours, probably the carb air guage is off. Mention it to the AME next time your in for an inspection. You may have thought the temp was above 0 but it probably wasn't if you were still getting carb ice.


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PostPosted: Fri Oct 21, 2011 9:00 pm 
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Very Simple:
1. The book.
Adjust carb heat to obtain a carb temp. of +4 on the gauge. Manifold pressure drops.
Reset manifold pressure and adjust mixture.

2 The rule of thumb.
If temp gauge hard to read. Adjust carb heat to cause a drop in man pressure of 1 inch.
Reset manifold pressure and adjust mixture.

Finally, a prudent pilot moniters the manifold pressure for any change, during all flight segments, for signs of possible ice.
Some employers forbid use of mixture at low altitudes. You will not obtain book fuel consumption without proper book settings of carb temps.
Bob

PS: This is from memory, so look it up and proove me right or wrong. Always do your own research as well as read Avcanada experts.



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PostPosted: Mon Oct 24, 2011 5:51 am 
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As I recall, the fuel burn ( per the chart) is based on a temp of +4. The desert scoop didn't seem to need carb heat but the chin scoop sure did especially on the coast. I also used the 1" drop on the man. press. as a starting point.

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PostPosted: Sun Nov 13, 2011 11:42 am 
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Be aware that while it does say in the book to keep the carb heat in the 0 to 4 degree C range, the carb that the manual refers to was the old auto-lean style. I haven't come across that carb on the 15+ different beavers I've flown. I can't say for sure if this would change the recommended operation of carb heat but it' something to consider. "Read the book" doesn't always apply in a beaver. Either way, what Bob suggests will work just fine.

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PostPosted: Tue Nov 15, 2011 8:17 pm 
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Yes people, listen to Beaverbob he is right on the money. DHC


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PostPosted: Mon Nov 21, 2011 11:32 am 
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True that auto lean carbs are all gone. They would have a hard time with being too hot.
It is important that the system is tight and all working well. The airbox on the beaver seems to be prone to
falling apart. If you wait untill the ice has formed and you scare the customers you have also chewed up the
impeller blades. Ice is damaging to this. Bob is on the right track.



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PostPosted: Tue Nov 22, 2011 4:28 pm 
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Thank's for the two votes of confidence.
Bob



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PostPosted: Sat Nov 26, 2011 7:12 pm 
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I don't know what CP with 35K time and experienced on radials would tell you not to use carb heat in a DHC-2. If you're talking water then you must be on the coast and particularly at this time of year (and every time of year) you should be expecting carb ice ALL THE TIME. If you're not on the coast, the previous still applies. I hope it isn't the same CP that tells his pilots the DHC-2 burns 15gph and that you should plan your payload accordingly. If it is, that pilot has a history of running low on fuel, and the management of carb heat isn't going to be your only point of disagreement if you're even half a professional.

From the scenario you described, you are very lucky you didn't have an unfortunate incident or accident. Carb air gages are notoriously inaccurate, and even more so when the company considers them unimportant. The MP trick described above is one solution, bearing in mind that every engine and every installation is different. One thing is for sure, definitely apply (smoothly, and over suitable landing areas) bouts of full carb heat regularly in cruise on steamy/misty days, and check on final - check immediately before take-off too.

As an aside, there are no such thing as book fuel consumption anymore for the DHC-2. If you read the manual very carefully you will note that fuel consumption is based on cruise performance with an engine installation equipped with an autolean carburettor, and as previously stated you will be hard pressed to find such an animal anymore. Also, an engineer told me this summer that when 100LL became the norm, the overhaul shops jetted the 985 carburettors with larger jets to provide extra cooling for the higher octane fuel. The only way to verify this for sure is to check with an overhaul shop, but if you rely on book numbers for fuel, you WILL run out of gas. In a radial, the only time you can have too much fuel is when you're on fire.

In a radial, carb ice is your nemesis, is always with you, and is right up there on the list of critical engine handling parameters.

Good on you for asking, however the following is my advice to you: Read the flight manual, read the maintenance manual, and ask credible, experienced operators and mechanics - preferably any you can find on a non-anonymous basis (ie elsewhere than on this forum). On here, you just never know who you're talking to, and those that come across as the most experienced might not reflect reality. If you're ever in the vicinity of an overhaul shop, you can get good tips for engine handling there too.

Cheers,
Kirsten B.


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PostPosted: Sun Nov 27, 2011 5:03 am 
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beaverbob wrote:
Thank's for the two votes of confidence.
Bob

Three votes. You are bang on BB.



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PostPosted: Sun Nov 27, 2011 4:09 pm 
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Of the few beavers I've flown, they have all burned similarily fuel wise per hour. PVC (this summers steed) was dead on at 20 gal/hr. most hover just above this.. only one burning more and it was pretty loose/high time. The gauges across these machine however were never even remotely close.. nor were any of the other gauges. As it turns out, two MP gauges were over reading. One showing 36in when it was only actually making 33. No wonder that machine felt like a freakin dog! I've also seen the various (should that read erroneous) indications on the carb air gauges. Makes one wonder just how many people are not paying attention to them! I've also got some pics of an airbox that decided to rattle itself apart!


Lots of valuable info posted here! So many experienced and well educated individuals. I dig it. I also really enjoyed the previous beaver handling threads.



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PostPosted: Mon Nov 28, 2011 6:19 pm 
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Rowdy wrote:
As it turns out, two MP gauges were over reading. One showing 36in when it was only actually making 33. No wonder that machine felt like a freakin dog!



Field baro will give you a pretty good idea of the health of the MP guage.



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PostPosted: Wed Dec 21, 2011 2:55 pm 
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Brand New on the Beaver/Amphibs........50hrs!!!! new float rating and learning that i've got a lot more to learn. The one thing that i do know is that the guages are at best nice to have and not so accurate and carb ice is a constant companion. Not so much in my other job at 37000ft !
I appriciate all the posts and ............wish me luck



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