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Who starts the APU near thunderstorms?

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Who starts the APU near thunderstorms?

Old 12th Jul 2018, 04:12
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Who starts the APU near thunderstorms?

According to this article, "experts" recommend FADEC equipped airplanes do so in "areas of electrical activity" after some CF-34 flameouts. Are CRJ guys required to do this? Not recommended on any Boeing FADEC airplane as far as I know......

FADECs programmed with surge-protection logic can respond to flow disruption temperature spikes by automatically shutting down the engines. This aircraft configuration has proven to be vulnerable to engine flameouts as a lightning strike charge travels longitudinally down the sides of the fuselage seeking an exit point. In the case of closely spaced fuselage-mounted engines, the strike’s “aero-thermal effects” can disrupt intake flows of both powerplants. FADECs programmed with surge-protection logic can respond to such disruption temperature spikes by automatically shutting down the engines. On the other hand, hydromechanically controlled engines, as an indirect result of lightning strikes, will tend to experience transient over-temperature conditions while continuing to operate, as shutdown protocols are manually controlled by the flight crew.

In 2001, an Embraer ERJ 145 regional airliner received a lightning strike while descending for an approach to Manchester International Airport in England, followed by the left Rolls-Royce AE3007 turbofan flaming out without a cockpit annunciation. The crew was on top of the situation and immediately transitioned to a successful single-engine landing. A post-incident investigation concluded that the failure of the FADEC-equipped engine was due to the aero-thermal effects of the strike characteristic of aircraft with small-diameter fuselages and aft-mounted engines. It further considered that a risk existed for loss of both engines, but investigators were unable to quantify that.

As for GE’s CF34 turbofan, aft-mounted on the Bombardier Challenger 601 through 604 business jets and CRJ series airliners, a company spokesman said such “rollbacks” due to lightning strikes have been minimal. “Since 2014, there have been four events determined significant,” he elaborated. “In three of the four cases, the engines relit without issue. In the fourth case, the engine was struck by lightning and the crew opted to shut down the engine as a precautionary measure [and] the aircraft landed without incident.”

As a precautionary measure when entering areas of electrical activity in aircraft with FADEC-equipped engines, experts recommend that, if within operating limits, flight crews fire up the APUs so that, in the event of a double engine failure, electrical power and hydraulics will be maintained while emergency relights of the engines can be attempted. (Note that it is possible that APUs can be affected by lightning strikes, too.) It’s also a good idea for flight crews to review memory items for a dual engine relight before venturing into areas of known lightning activity.

Lightning: Risks, Detection and Avoidance | Business Aviation content from Aviation Week
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Old 12th Jul 2018, 15:33
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Not recommended on any Boeing FADEC airplane as far as I know......
Under the Boeing 737 Classic Supplementary Procedures Adverse Weather heading: "Moderate to Heavy Rain, Hail or Sleet", it mentions "Consider starting the APU (if available)" . Presumably this is a wise precaution against the possibility of a double flame-out in severe weather. On a personal note, when departing or descending towards an area of severe thunderstorm activity, this writer would elect to leave the APU running for take off and climb, and start the APU on descent before entering such areas of weather activity. It was considered good airmanship in case of a dual flameout in heavy rain. After all, there have been several recorded cases of dual flame-outs in severe weather. .
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Old 12th Jul 2018, 19:20
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Not recommended on any Boeing FADEC airplane as far as I know......
I spent over 30 years working FADEC engines at Boeing - I don't recall that we ever had a flameout of a FADEC engine attributed to a lightning strike. Further, none of the Boeing FADEC installations have logic that would unilaterally shutdown a running engine for anything other than a detected overspeed condition. Many of the FADECs have surge recovery logic, but it doesn't shutdown the engine - it does stuff like open the compressor bleeds and turn on ignition to clear a surge/stall.
There have been cases where a lightning strike has caused an engine shutdown - but they were unrelated to the FADEC (in fact the ones I can think of were purely hydromechanical control engines). If there is a direct attachment to the engine inlet, the airflow disruption can cause a surge related flameout - although this was more of an issue with the smaller diameter low bypass engines (e.g. JT8D).
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Old 13th Jul 2018, 04:43
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This aircraft configuration has proven to be vulnerable to engine flameouts as a lightning strike charge travels longitudinally down the sides of the fuselage seeking an exit point. In the case of closely spaced fuselage-mounted engines, the strike’s “aero-thermal effects” can disrupt intake flows of both powerplants.
It would seem to be directed at rear mounted engines, rather than the under wing slung types.
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Old 13th Jul 2018, 07:42
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It would seem to be directed at rear mounted engines, rather than the under wing slung types.
A few years ago, 10 or more, we had 2 A330's with CF-6 engines dual flame out in rain on descent. As a result, we had to start the APU for descent, select high flow from the packs, to lower the chances of compressor stall. We did get rid of the A330 with CF-6 engines and stuck with the RR.
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Old 13th Jul 2018, 08:19
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Off topic pic a little but we used to start
the APU on a Cat 3 Autoland for extra redundancy


B757 / 67
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Old 13th Jul 2018, 21:15
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[QUOTE][- I don't recall that we ever had a flameout of a FADEC engine attributed to a lightning strike./QUOTE]

About 10 years ago I flew B737NG’s for an Asian carrier, and during that time we had two incidents of lightning strikes that resulted in engines shutting down. One was on finals and the crew managed to continue to a successful landing. Getting further information about both incidents was problematic, (what happened to the auto-relight for instance), but I do recall a bulletin from Boeing that said they had addressed an issue resulting in the engines being more tolerant of lightning strikes, and the attendant airflow disruption.
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Old 14th Jul 2018, 16:32
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Wow, 4 modern aircraft with total engine failures in the last 10 years and we haven’t heard about it?
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Old 16th Jul 2018, 14:58
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Thunderstorms?

Originally Posted by JammedStab View Post
According to this article, "experts" recommend FADEC equipped airplanes do so in "areas of electrical activity" after some CF-34 flameouts. Are CRJ guys required to do this? Not recommended on any Boeing FADEC airplane as far as I know......

FADECs programmed with surge-protection logic can respond to flow disruption temperature spikes by automatically shutting down the engines. This aircraft configuration has proven to be vulnerable to engine flameouts as a lightning strike charge travels longitudinally down the sides of the fuselage seeking an exit point. In the case of closely spaced fuselage-mounted engines, the strike’s “aero-thermal effects” can disrupt intake flows of both powerplants. FADECs programmed with surge-protection logic can respond to such disruption temperature spikes by automatically shutting down the engines. On the other hand, hydromechanically controlled engines, as an indirect result of lightning strikes, will tend to experience transient over-temperature conditions while continuing to operate, as shutdown protocols are manually controlled by the flight crew.

In 2001, an Embraer ERJ 145 regional airliner received a lightning strike while descending for an approach to Manchester International Airport in England, followed by the left Rolls-Royce AE3007 turbofan flaming out without a cockpit annunciation. The crew was on top of the situation and immediately transitioned to a successful single-engine landing. A post-incident investigation concluded that the failure of the FADEC-equipped engine was due to the aero-thermal effects of the strike characteristic of aircraft with small-diameter fuselages and aft-mounted engines. It further considered that a risk existed for loss of both engines, but investigators were unable to quantify that.

As for GE’s CF34 turbofan, aft-mounted on the Bombardier Challenger 601 through 604 business jets and CRJ series airliners, a company spokesman said such “rollbacks” due to lightning strikes have been minimal. “Since 2014, there have been four events determined significant,” he elaborated. “In three of the four cases, the engines relit without issue. In the fourth case, the engine was struck by lightning and the crew opted to shut down the engine as a precautionary measure [and] the aircraft landed without incident.”

As a precautionary measure when entering areas of electrical activity in aircraft with FADEC-equipped engines, experts recommend that, if within operating limits, flight crews fire up the APUs so that, in the event of a double engine failure, electrical power and hydraulics will be maintained while emergency relights of the engines can be attempted. (Note that it is possible that APUs can be affected by lightning strikes, too.) It’s also a good idea for flight crews to review memory items for a dual engine relight before venturing into areas of known lightning activity.

Lightning: Risks, Detection and Avoidance Business Aviation content from Aviation Week
I work for the worlds largest operator of -900s, and we have a couple of ex Bombardier program test pilots flying the line. I have never heard it discussed here.
Our fleet manager is extremely knowledgeable and obviously has great connections to the OEM, so I'm gonna call B on this.
As an aside; we do start the APU for Cat II approaches to have an extra generator available...
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Old 16th Jul 2018, 16:45
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Originally Posted by Centaurus View Post
Under the Boeing 737 Classic Supplementary Procedures Adverse Weather heading: "Moderate to Heavy Rain, Hail or Sleet", it mentions "Consider starting the APU (if available)" . Presumably this is a wise precaution against the possibility of a double flame-out in severe weather. On a personal note, when departing or descending towards an area of severe thunderstorm activity, this writer would elect to leave the APU running for take off and climb, and start the APU on descent before entering such areas of weather activity. It was considered good airmanship in case of a dual flameout in heavy rain. After all, there have been several recorded cases of dual flame-outs in severe weather. .
Thanks,

But based on subsequent replies that this procedure is due to reasons other than FADEC issues from lightning strikes which is what I meant.

Interesting to know about it though.
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