[dsmith1055]

Recent posts on fire suppression systems mentioned possible fire detection systems. A Google search on Linear fire detection systems brought up the below listed link along with several others.
This type detection cable is used in at least one aviation application in the Cessna Caravan. How about a discussion on whether this or some other readily available technology could be used for a practical inexpensive system.?

http://www.lineardetection.com/

 

[John Clark]

The need for a fire detection system in the average RV is much different than a piston twin or turbine aircraft. In an RV the pilot is going to be aware of the problem very quickly, being a couple of feet and a sheet of stainless steel away from the action is much different than being unaware in an air conditioned pressure vessel.

My concern is not about detection, but rather supression in the case of an RV. The FAR mandated extinguishing systems in turboprops really aren't the answer to our situation. In the average turboprop cowling there isn't nearly the air movement that we see in a piston engine installation, making a halon or similar supression system viable.

John Clark ATP, CFI
FAAST Team Representative
EAA Flight Advisor
RV8 N18U "Sunshine"
KSBA

 

[dsmith1055]

Fire detection

Hey John,
I wondered if an insulated firewall RV with a fire in the Carb area where air movement might not be so great could benefit from early detection. I agree the need is not as great as in turboprops. As an aside, not all turboprops have fire suppresion. The Caravan has detection only. I had never thought about a detection system until it was mentioned in the fire suppresion thread.

 

[Bevan]

fire detection

Couldn't fire detection be as simple as a strategically placed temp probe(s) (such as FT-1827-02 from Grand Rapids) connected to the engine monitor and set to alarm at an upper limit of say 400-500 degrees?

Bevan

 

[John Clark]

Actually you don't even need the probe. The required detection systems in Part 25 aircraft (airliners) are a "loop" of wire that will short (or fail) at a given temperature and activate a warning. This way you can cover several areas within the cowl with one circuit. Building such a system would be an interesting exercise, but I still think you would be able to smell the heat/fire at about the same time the warning went off. The real issue is what to do about the fire.

John Clark ATP, CFI
FAAST Team Representative
EAA Flight Advisor
RV8 N18U "Sunshine"
KSBA

 

[RV8R999]

use a piece of solder wire to complete a ckt . When the fire starts it melts the solder opening the ckt and latching an alarm.

in fact the Dynon Skyview has several pins which are configured to sense a ground or an open ckt making this an easy project if so inclined. Probably need to double or triple up the strands just for reliability sake. I bet it would work provided it isn't too close to the exhaust.

 

[Wayne Gillispie]

I have one on my -10

Total cost $20. Everyone already has several in their house...hvac, dryer, coffeemaker. I installed an adjustable limit switch with temp initially at 250F. Switch is placed near cowl exit. No matter where the fire originates in my engine compartment, all air exits past the sensor. No need for multiple sensors.

And no we don't always know there is a fire until it burns through your bottom skin. If we have not calibrated our fuel flow sensor yet or have low time in the plane then a high fuel flow may not catch your attention.

If my limit switch opens, a five terminal relay deenergizes and closes a set of contacts illuminating a "High Exit Temp" LED.

Yes, in the UH-60's we had fire sensing eyes and two halon bottles. There is very little airflow in eng compartment, lots of money available and over 3200 shp to lift all of that extra weight.

My plan is to detect a possible fire, confirm by a circling descent to look for smoke silouetted against the sky, then take appropriate action.

I feel that a halon bottle will not do any good in our engine compartments as there is too much airflow. If I have a cabin fire I have a small halon extinguisher, smoke hood and a door that easily departs the plane(well proven). If your windscreen is smoked up and you choose to keep the door on and fire off a full 5 lbs of halon you may extinguish the fire and yourself. Then try landing with smoked up windows.

 

[John Clark]

Hey John,
I wondered if an insulated firewall RV with a fire in the Carb area where air movement might not be so great could benefit from early detection. I agree the need is not as great as in turboprops. As an aside, not all turboprops have fire suppresion. The Caravan has detection only. I had never thought about a detection system until it was mentioned in the fire suppresion thread.

Not at all scientific, but I have seen the aftermath of 3 engine fire events in the last 40+ years. Two were exhaust system failures blowing hot exhaust/flame at combustable items in the cowl and one cylinder head failure on a Lycoming that almost burned through the pushrod tubes. Might have made for a spectacular oil fire. No fuel fires though.

John Clark ATP, CFI
FAAST Team Representative
EAA Flight Advisor
RV8 N18U "Sunshine"
KSBA

 

[airguy]

Total cost $20. Everyone already has several in their house...hvac, dryer, coffeemaker. I installed an adjustable limit switch with temp initially at 250F. Switch is placed near cowl exit. No matter where the fire originates in my engine compartment, all air exits past the sensor. No need for multiple sensors.

+1 for that. I had already come to the same conclusion, and have an extra temp sensor that I have planned for that location with a temp alarm initially set to about 250F, to be finetuned during Phase 1.

 

[cfiidon]

Fire detection, suppression, reaction

This discussion of fire detection and suppression has me thinking (dangerous!) What follows is my 2 cents, and worth every penny.

I found this at Radio Shack: http://www.radioshack.com/product/index.jsp?productId=2102788

I'm thinking of connecting one to my Dynon D180 contact inputs. I would get a warning if it opened. I was thinking the best place to put it would be on the fuel line from firewall fuel pump (IO-360). Several could be placed around the engine compartment in series if desired.

First, I think the probability of an engine fire is relatively low if in construction we use the proper materials and techniques (steel fittings, fire sleeve, non-rigid lines, pre-flight and periodic inspections, etc) It would be an interesting exercise to determine through NTSB reports how many fires (engine or electrical) have occurred in both certified and experimental aircraft. Intuitively, I think electrical fires are probably more prevalent.

Secondly, if an engine or electrical fire does occur we need to:

1) Detect
2) React
a. Confirm
b. Suppress (Remove fuel, oxygen, ignition source)
c. Land and get out

Time is our enemy here. So detection seems like a good first step. This would be followed by protection (firewall insulation, chemical suppression, smoke hood, parachute, transporter beam.....). Following protection, we have emergency procedures (fuel off, electrical off, airspeed, etc.)

To summarize we need to prevent, detect, react, and buy time. Although a firewall forward halon suppression certainly fits in here, methinks it is not the panacea. I noted in some of the installation photos that a halon fire suppression system was being fed by thin walled aluminum lines. How long would they last?

Time to stop rambling here and ramble out to the shop....

Don

 

[Vern]

RV Fire: from a previous post of mine

Yesterday was sobering experience for me!

I got a call from a local A&P/AI who needed advice about an RV-6 that he had been asked to rebuild. I went over to have a look at the RV-6 and was shocked by what I saw, which I share for your safety.

This older RV had just had an IO-360 and blended prop installed professionally at another airport. The owner had flown to our airport (KFFC) and was about to depart for his homedrome. He was in the runup area beside an avionics shop. While performing his runup, his RV engine area burst into flames. Several mechanics rushed out with extinguishers, put the fire out, and got the pilot out with some burns on his legs.

When I looked at the RV yesterday, the tip up canopy, cowl, seats, and all instruments and radios had been removed.

Another mechanic and I surmised that a small 1/8" copper tube from the rear-mounted mechanical fuel pump to a fuel pressure sending unit broke during the runup, allowing fuel from the 1/8" copper line to spray out above the exhaust. This fire only lasted a few minutes due to the quick response by the mechanics. In that short time, every wire and hose firewall forward was either melted or damaged. The entire panel wiring was a melted mess. The interior floorboard 1" black insulation was mostly melted.

Apparently, the fire was like a blow-torch as the windblast from the runup caused the lower firewall and lower cowl exit area to direct the fire down and underneath the RV.

Incredibly, the canopy and cowling are useable. The cowl will need some repairs, but it did not burn thru.

Even though the paint under the airplane did not burn off, and no rivets 'popped' I am concerned that the thick bottom skin in front of the wing spar may need replacing due to tempering from the heat. Certainly the mags, fuel pump, and prop gov need overhauling due to possible heat damage. The firewall seems OK.

My points: if this plane had taken off, the heat from the fire would have really burned the pilot, possibly incapacitating him quickly. His instruments and accessories would have failed shortly. An aluminum airbox would have soon allowed flames inside the cockpit. All this from the fuel spray from a 1/8" line! What would the main fuel line do? (I know-I've witnessed that also)

So, next time your cowl is off, take a critical look at your systems. Everything firesleeved? Have you got any stiff copper lines? Do lines have service loops/slack in them? Any 'stiff' lines used to join the shaking engine and the fixed firewall? All B-nuts tight? All openings in the firewall sealed? Any hidden chafing ready to wear through?

Another area we RV'ers might look at is at our brake lines and fittings which is another potential fire source for our RV design. What about leaking fuel tanks allowing fuel to seep in under our seats and ignite due to electrical devices under the floor boards?

In my AF days I survived a number of inflight fires and explosions. It's no fun when the smoke is so thick and pungent you can't see the fire handles glowing bright red!

We have a fun hobby and we all want to fly safe. Join me in taking another look at your RV to keep it that way!

Yesterday was sobering experience for me!

+++++++++++++++++++++++

Had a hangar fire on a new RV-7A last week at our airport. You'd be amazed at how much skin damage was done. Replace those Van's aluminum heater boxes on your firewalls with stainless!

 

[Walt]

Personally (and I've said it before) I think most folks would be much better off with an improved "Maintenance Program" rather than adding more stuff to the airplane like halon systems and fire detection loops.

I've seen this exact fuel pressure line setup before, and have always convinced the owner that it needs to be replaced ASAP (if you value your life). Many times the problem is the owners just don't know anything about maintenance and that's the way they bought the airplane, and some people (like the builder) will say "it's ok"

Everyone should find a good mechanic to do pre-first flight inspections and help/assist with condition inspections unless you have the qualifications to do them yourself (a repairmans certificate may give you the authority, but fails to give you the knowledge, sorry).

Like my daddy used to say "An ounce of prevention is worth a pound of cure".

 

[JonJay]

Personally (and I've said it before) I think most folks would be much better off with an improved "Maintenance Program" rather than adding more stuff to the airplane like halon systems and fire detection loops.

I've seen this exact fuel pressure line setup before, and have always convinced the owner that it needs to be replaced ASAP (if you value your life). Many times the problem is the owners just don't know anything about maintenance and that's the way they bought the airplane, and some people (like the builder) will say "it's ok"

Everyone should find a good mechanic to do pre-first flight inspections and help/assist with condition inspections unless you have the qualifications to do them yourself (a repairmans certificate give you the authority but fails to give you the knowledge, sorry).

Like my daddy used to say "An ounce of prevention is worth a pound of cure".

Agree 100%. My fire detection is my nose. I recently reworked my forward ramps and baffle seal. On my first test flight the front seal flipped over and the fly wheel rubbed on it. I could smell the rubber immediatley.
I think I killed the other post when I asked for anyone to give me an example of a fire suppression system actually saving a life outside of military or commercial airplane. Nobody responded. Also, there was a lot of discussion on whether the systems marketed would even work.