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Terrence,
There should be a SS doghouse around the firewall opening and, when the
gear is retracted, a small door on the leg or other seal that keeps the
nose wheel well closed off from the engine compartment. Of course, if the
nose wheel door doesn't seal completely, there is the possibility of getting
engine compartment flames into the well that way.
If I were to land with an engine fire (unable to turn off the fuel or the
oil was still burning), I would do it gear up. "Why?" You might
ask. Well, extending the gear provides more air for any fire in the
cockpit, exposes the nose wheel well to engine compartment flames and, most
importantly, belly landings come to a stop more quickly (believe me, I know)
without any danger of catching the nose gear and flipping or worrying about
crosswinds, braking surface, etc. Since there is no control on a gear
up, the pilot could be opening the canopy, un-belting, climbing out on the wing
and all during the slide....................
Scott Krueger
In a message dated 7/3/2012 12:17:38 P.M. Central Daylight Time,
troneill@charter.net writes:
Any
comments on sealing the big hole in the 235 etc. firewall for the nosegear,
when extended or retracted?
Terrence
Colyn,
Note that 300 series Lancairs use aircraft plywood for the core of
the firewall, one layer of glass on each side and many layers of glass
in the engine mount and support gusset areas. That glass has not
been cured in an oven and will soften at a temperature well below
280F. The wood remains rigid until it chars.
Turbines aside, Engine compartment fires may be oil or gas or, possibly
both after a while. Oil from a significant "leak" will be blown
overboard rather quickly until the engine seizes. Fuel can be shut off
from reaching the engine compartment, thus one would want easy access to the
shutoff valve leading to the engine compartment (unfortunately, the 200/300
series puts the header tank shutoff deep into the passenger foot
well). A high speed dive has the possibility to snuff the fire by
screwing up the A/F ratio.
All flexible fluid lines in the engine compartment should be the best
(like auto racers, I believe that only steel-ended fire-sleeved
teflon-SS covered lines meet that requirement).
Engine fuel fittings should be steel.
It is common aviation practice to use aluminum fittings for oil
since they are beefier when larger than the -4 size.
Now, all that is left to worry about is that maintenance assembly
problem where a connection was left finger-tightened or a small exhaust
leak that becomes focused on some flammable fluid carrying part.
Crashes with the engine running are a different problem.
Cockpit fires are a different problem (open air vents and extending the
gear may allow more air to enter the cockpit and feed the fire).
Finally, Lancairs without cabin pressurization will have the cockpit
pressure less than the engine compartment pressure whilst joyfully operating
at high speed and at any elevation. There must be NO firewall openings
that would allow passage of any engine compartment gasses into the human
occupied cockpit, thus eliminating flames or flame by-products (like
CO) to pass. Review the security of the heating system for the same
reason.
Uh, in case of fire you may want to shut down air vents where the
intakes are located just aft of the cowling. Just saying.
Scott Krueger
PS No, I don't wear a smoke hood or a nomex fire suit. No
stinking parachute either. Risk is manageable. The perfect outcome may
not always be economically possible (think of Fed death panels).
The
data on the blanket may be available from HI-Temp INsulation Company in
Camarillo, CA.
...and it may be available from Lancair.
I remember that:
- it passed a 2000 dF/15 minute burner test to establish compliance
with AC 20-135
- backside temp after 4 minutes was over 300 dF
- backside temp after 9 minutes was over 500 dF and slowly rising
after that.
I would be interested in any data on the SS/Fiberfrax approach.
Things that concern me about the LIV-P firewall:
- I'm told that pre-preg loses structural integrity around 280 dF.
That would give you 3 minutes to get it on the ground by above
numbers.
- The engine mount will conduct heat directly into the firewall
- The cabin air valve includes plastic components
- The rubber grommet approach for through holes I'm told will convey
smoke into the cockpit.
- At 3000 fpm it takes 8 minutes to get down from FL240
It seems to me SS might to some degree mitigate the above issues. If
I had it to do over again maybe:
- Blanket over SS
- Fully SS air valve
- Improved through holes with connectors fastened to the SS
- What does FiberFrax do?
In the meantime I have temp sensors around the engine compartment and
a Halon canister in the back plumbed to the engine compartment. (To be
used after fuel shutoff, prop stopped-to stop pumping oil, electrical off,
airspeed reduced - to reduce Halon dilution)
It is true that vigilant maintenance is the most effective strategy.
On the other hand it got my attention when my "brand new" exhaust
system leaked enough to burn through a blanket near the gascolator.
(exhaust system since replaced).
On Jun 29, 2012, at 3:28 PM, Steve Colwell wrote:
Is there someone out
there that would like to make a comparison (cost, utility, performance et
al) between the blanket and the stainless/fiberfrax
installation?
Jim
I
was stressing out over the best possible fire protection by looking at
fire resistant: Paint, Firewall Penetrations, Sealants, etc.. My
conclusion was to do the best job I could on fire prevention (fuel lines,
anti-chafe, heat shielding, exhaust pipes, fire sleeves) and have a
procedure for getting it on the ground as quickly as possible with fuel
and ignition off.
Why?
A local Aerobatic Performer flying a Harmon Rocket had a FWF fire in the
pattern. He got it on the runway asap, but not before a hole was
burned in the belly. He died of smoke inhalation. The odds are
not good on a in-flight FWF fire, has anyone heard of a successful
conclusion?
Steve
Colwell Legacy
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