Did Forest fire Cause Double Engine Failure

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pelmet
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Did Forest fire Cause Double Engine Failure

Post by pelmet »

From TSB....

C-FDTH, an Air Spray Ltd. Lockheed L-188A was conducting aerial firefighting operations as
ASB498 locally from Manning Aerodrome (CFX4), AB, on Alberta wildfire #PWF037, (23 NM W of
CFX4). On the second flight of the day, while on short final for the second drop, the fire reached a
taller tree patch, which rapidly increased the intensity of the fire. This resulted in a rapid increase in
fire activity and temperatures on the left side of the aircraft. The captain called for an increase in
power. While power was being advanced, a temperature spike of 1040° F was noticed on the # 1
engine and was identified by the co-pilot. The flight crew observed the # 1 engine propeller speed
drop and the captain called for an engine failure drill on the # 1 engine (Allison 501D-13). While
securing the # 1 engine, the # 2 engine temperature spiked to 1040° F. The captain noticed the
decreased performance, confirmed with power lever application and observed no change. The
flight crew determined that the engine de-coupled and conducted the engine failure drill on the # 2
engine. Both engines were confirmed shutdown and propellers feathered. Once at a safe altitude,
the emergency checks were completed, and a 2-engine landing was briefed. An emergency was
declared and the aircraft returned to CFX4 where the aircraft landed without further issue.


It would be interesting if any firefighting pilots on the forum could tell us about precautions/possible issues with getting too close to fires.
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Dry Guy
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Re: Did Forest fire Cause Double Engine Failure

Post by Dry Guy »

I've never operated an Allison. What is the mechanism that allows the propeller to decouple from the engine?
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cdnavater
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Re: Did Forest fire Cause Double Engine Failure

Post by cdnavater »

Dry Guy wrote: Tue Sep 10, 2024 11:09 am I've never operated an Allison. What is the mechanism that allows the propeller to decouple from the engine?
I’ve never operated an Allison either but I believe it’s connected via a gear box, those typically have a spline shaft that can shear or retract!
So, curiosity got me and I searched the interweb, hers’s what I found, pretty interesting.

https://www.enginehistory.org/GasTurbin ... -188.shtml

“Engine Decoupler
This device is, in effect, a mechanical fuse that backed up the NTS if it failed to work at about minus 375 horsepower; when the negative horsepower magnitude reached around minus 1,500. The decoupler worked in a fashion similar to the NTS using a helical spline operating against Belleville spring washers as a negative torque sensing device. When decoupling took place, the two halves of the coupling separated and the engine power section was disconnected from the reduction gear box. After the failed engine had decoupled the propeller would continue to windmill at governing rpm because of its independent hydraulic oil system, but at a relatively high blade angle and with low drag. Such a double failure would be extremely rare, but the airframe structure was designed to withstand such a critical combination., The decoupler re-engaged in flight once the negative torque was removed but had to be inspected and possibly replaced before the next flight. The decoupler, illustrated schematically in Figure 6, was mounted within the reduction gear box at the drive shaft forward end”
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Dry Guy
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Re: Did Forest fire Cause Double Engine Failure

Post by Dry Guy »

Neat. Thanks for posting that. So the high intake air temperature cooked the engines. Pretty wild but makes sense. I'm surprised it doesn't happen more often over fires.
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digits_
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Re: Did Forest fire Cause Double Engine Failure

Post by digits_ »

Dry Guy wrote: Tue Sep 10, 2024 12:42 pm Neat. Thanks for posting that. So the high intake air temperature cooked the engines. Pretty wild but makes sense. I'm surprised it doesn't happen more often over fires.
Well you're generally not supposed to fly *through* the fire... Note that this CADORs is very likely based on the report of the crew. I'm fairly certain 'a rapid increase in fire activity' is SMS speak for 'we got roasted like a rotisserie chicken'.
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Swampdonk
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Re: Did Forest fire Cause Double Engine Failure

Post by Swampdonk »

I know absolutely nothing about the plane but shared a crew house with a guy who flew them for 20+ years. His reasoning for leaving the electra and the company was the frequency of multiple engine failures.
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TeePeeCreeper
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Re: Did Forest fire Cause Double Engine Failure

Post by TeePeeCreeper »

Yes, there are guidelines but they are just that guidelines.

Someone mentioned something about “not going though the fire”. -Although the general idea is to keep our asses safe sometimes, exactly what was mentioned in the report occurs. re: those pines are friggen jerry cans of raw fuel!
With that said, a dual over temp, both on the same side sounds suspect.

TPC
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