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Ram Air Turbine

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johngoodman

Joined: 18 Sep 2006
Posts: 530
Location: GA

Posted: Mon May 05, 2008 4:51 am Post subject: Ram Air Turbine

I've decided to install a pop-out ram air turbine alternator as my backup power supply. I'm looking for a good place to put it and the most likely place seems to be the starboard skin of the baggage compartment. The entire package can fit into a 7" by 7" by 8" cube to give you the approximate size. The pop-out door is smaller.

To get you up to speed, here is the web site:

http://www.basicaircraft.com/



Bring it on, flames and all...



John

_________________
#40572 Phase One complete in 2011

pitts_pilot(at)bellsouth.
Guest

Posted: Mon May 05, 2008 5:11 am Post subject: Ram Air Turbine

johngoodman wrote:



 	  Quote: 	
		  



I've decided to install a pop-out ram air turbine alternator as my backup power supply. I'm looking for a good place to put it and the most likely place seems to be the starboard skin of the baggage compartment. The entire package can fit into a 7" by 7" by 8" cube to give you the approximate size. The pop-out door is smaller.

To get you up to speed, here is the web site:

http://www.basicaircraft.com/



Bring it on, flames and all...



John



The complexity and installation plus the 6 amps (at 85 MPH) doesn't turn 
	


me on.  I haven't checked the price of the PlanePower vacuum pad 

alternator, but I'd lean toward that for a second alternator.  

Alternators are pretty bulletproof now, so my question is what caused 

the search for an alternative???  The biggest failure modes I hear about 

(I haven't suffered any) are loose (or missing!) case bolts and 'field' 

wires fracturing inside the insulation next to the alt lug ..... and 

these are in OLD airplanes!!!  No flames .... just curious.  Not knowing 

the thought process leaves a big hole in the available data.

Linn

do not archive

johngoodman

Joined: 18 Sep 2006
Posts: 530
Location: GA

Posted: Mon May 05, 2008 6:30 am Post subject: Re: Ram Air Turbine

Excellent question. I'm in the early stages of designing the electrical and panel. I've been reading Bob Nuckoll's book and other articles regarding dual alternators, dual batteries, etc., and I've found myself leaning towards the single battery/dual alternator path.

I have a lot of experience with drop-out ram air turbines in airplanes - not that I ever needed to use it except in simulators. I'm comfortable with the concept.

The B&C or PlanePower vacuum pad alternators are logical choices in my book. They are a little cheaper, as well. But I like the concept of a totally independent alternator outside the engine compartment. I also like the "pull the handle" logic. We all know that a pilot's IQ goes to about 40 when things suddenly stop, and that pulling tends to satisfy the inner beast.

I think it qualifies as a KISS. No cowling to pull, one less thing to do in the engine compartment, etc.



John

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#40572 Phase One complete in 2011

tsts4

Joined: 06 Aug 2007
Posts: 167
Location: Tampa, FL

Posted: Mon May 05, 2008 6:54 am Post subject: Re: Ram Air Turbine

The PlanePower vacuum pad unit is for Continentals, not Lycomings.  When I asked them if they were planning to come out with an SD-20 alternative, they said they weren't planning to.  I for one hope they change their minds.  Until then I'll stick to the SD-20.



I admire your interpretation of KISS -- for me throwing a SD-20 on the pad is way simpler than trying to design and install a ram turbine setup.  Not a flame as I like to see folks come up with different solutions to problems and am very interested in seeing what you finally come up with--good luck!

_________________
Todd Stovall
aka "Auburntsts" on EAA and VAF
RV-10 N728TT -- Flying

AV8ORJWC

Joined: 13 Jul 2006
Posts: 1149
Location: Aurora, Oregon "Home of VANS"

Posted: Mon May 05, 2008 8:55 am Post subject: Ram Air Turbine

The RATs on our air carrier fleet are one of the most maintenance

intensive accessories.  They often do not work and require tremendous

ongoing maintenance to keep them doing what the college kids in Ontario

computer screens designed in their heads.



Look to someone who has a functioning RAT or be prepared to report to us

"How is that working for you?" as Dr. Phil would phrase it.  All this

from a guy who will throw more features at an RV-10 than any one builder

would reasonably try.



For my acronym impaired buddies, that stands for Rotary (cause they have

to turn not just get air rammed through them) Air Turbines and it is

amazing how much air must pass through the blades to effect life

sustaining electron flow.



When the power goes out or the engine stops or the blade won't pull, The

aircraft belongs to the insurance company.  Land immediately and walk

away to answer Dr. Phil.  Do not follow in the footsteps of Mr.

Knoeplein (OSH '05) and try a backup system to correct an in-flight

failure.



John Cox

N49CX



--

carl.froehlich(at)cox.net
Guest

Posted: Mon May 05, 2008 3:54 pm Post subject: Ram Air Turbine

Starting with Bob Nuckoll's book (good reference for any builder), I

considered various designs with dual alternators and a single battery when

building my 8A.  Most however had at least one way where a single fault

would end up with no electrical power.  As I have dual electronic ignitions,

this was not acceptable.



Considering there is nothing as reliable as a maintained, modern battery, I

designed a dual Odyssey PC625 battery, single alternator power distribution

for the 8A.  One battery has enough power to run the panel and ignition for

at least two hours - that is if you dump the heavy, non-vital loads like

landing lights and pitot heat.  Both batteries in parallel (normal

operation) provides superior cranking power.  While a single battery starts

my IO-360 just fine, I would not take off with a known battery problem.

I'll have a similar install in the RV-10.



I replace one battery every other annual, or if I do something stupid like

leave one of the master solenoids on and run a battery down to the ground (I

now have a light to remind me).  This makes sure that neither battery is

over four years old.  The first battery I pulled out is still in service on

a Pulsar.



I did a 2 hour test discharge using one battery.  It keep one ignition and

panel up with continuous transponder and radio comms with air traffic

control (the other battery and alternator where available if needed during

this test).



Carl



--

dlm46007(at)cox.net
Guest

Posted: Mon May 05, 2008 4:31 pm Post subject: Ram Air Turbine

--

robin1(at)mrmoisture.com
Guest

Posted: Mon May 05, 2008 4:36 pm Post subject: Ram Air Turbine

John,

	Again no expert here and not flying yet but I like the dual

battery set up as Carl describes and have configured our -10 exactly

that way. Battery 1 trickle charges Battery 2 and both batteries are

available for extra cranking power on cold days etc... #2 battery

energizes the Essential Buss only. Additionally our back up to the G900X

is a Dynon 100 with its own internal battery. So that is three, count

them three batteries. I think this is a belts, suspenders and another

set of suspenders approach. 



Robin

Do Not Archive

johngoodman

Joined: 18 Sep 2006
Posts: 530
Location: GA

Posted: Mon May 05, 2008 4:38 pm Post subject: Re: Ram Air Turbine

Ahhh...

Just the kind of response I was looking for - strong opinions. Keep firing, I want to hear all the negatives. One thing I need to point out is that the RAT is a ready to install device. All I have to to is mount a square bracket, cut a smaller hole in the skin, and bolt in the device. Wiring to the bus and the pull handle are additional, but minor.

RATs are labor intensive to airliners because nobody ever uses them and maintenance has to "maintain them." In our environment, an easy matter. A simple airborne test and a write-up would solve all the part 135/121 problems, but would create a lot of MEL stickers. However, we can pull it anytime we want and get it fixed with no problems, just don't make it a part of your POH IFR requirements. In fairness to the airline maintenance folks, pushing it back in is no easy job on an Airbus.

Keep the comments coming....



John

John

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#40572 Phase One complete in 2011

carl.froehlich(at)cox.net
Guest

Posted: Mon May 05, 2008 6:33 pm Post subject: Ram Air Turbine

Just to repeat the key point, you want to preclude a single point failure

taking out your power distribution system.  Having a second (or more)

alternator, regardless of type, but retaining typical production type buss

wiring does little to prevent many common failure modes.  There was a

article a few years ago about a twin (two alternators) losing all electrical

power by a common buss connection failure.  It provides a good case study on

this issue.  I'll see if I can dig it up.



Another consideration is the reliability of the backup power.  A second

battery that is routinely used and monitored during normal operations, or a

stand by mechanical device that REALLY needs to work when you pull the cord?



Carl

RV-8A (400 hrs)

RV-10 (wings) 



--

johngoodman

Joined: 18 Sep 2006
Posts: 530
Location: GA

Posted: Mon May 05, 2008 6:52 pm Post subject: Re: Ram Air Turbine

or a stand by mechanical device that REALLY needs to work when you pull the cord? 

Hmmm,

Maybe a vacuum system?

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#40572 Phase One complete in 2011

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