Circuit Breaker Safety

[CD]

Circuit Breaker Safety

Business & Commercial Aviation Jul 01 , 2009 , p. 68
Richard N. Aarons

The one-push practice does not consider the cumulative nature of wiring damage and the removal of power only temporarily stops the progression of the damage.

The NTSB rarely undertakes a full “blue book” investigation into a light-twin accident, but the loss of NASCAR’s Cessna 310R on July 10, 2007, is an exception. The Safety Board was attracted by the facts that the piston twin was part of a large turbine fleet; that questions existed about the use of the airplane under NASCAR’s standard operating procedures; and that a critical maintenance issue may have slipped through the management cracks.

The airplane had departed Florida’s Daytona Beach Airport (DAB) at 0822 for Lakeland Linder Regional Airport. A NASCAR physician — holder of a commercial certificate — was the PIC and occupied the left seat. A NASCAR ATP-rated safety pilot was in the right. Ten minutes after departure, upon leveling off at 6,000 feet, the right-seat pilot contacted ATC and declared an emergency stating “smoke in the cockpit. We need . . . to land at [Orlando] Sanford [International Airport].” The controller cleared the flight to Sanford and to descend to 2,000 feet.

ATC radar records showed that the airplane turned toward Orlando and began to descend. At 0833:15, controllers heard a radio transmission that seemed to include the phrase, “shutoff all radios, electrical . . .” It was the last communication from the aircraft. Transponder returns ended at this time. The airplane was eight nm northwest of Sanford and descending rapidly.

Primary radar returns continued for another minute and a half showing the airplane continuing on a 150-degree heading to Sanford. The last return was recorded when the airplane was about three miles out at 1,200 feet agl. The aircraft crashed into a residential neighborhood about 0.7 nm west of the last primary return.

Witnesses told investigators the airplane was traveling “extremely fast,” was “very low” and its wings were “rocking” as it descended. Just before impact, the 310 entered a “steep bank” and made a sharp turn to the west. Witnesses reported seeing smoke trailing from the airplane, and one witness stated, “Smoke was trailing from the port side.”

Both pilots were killed, as were three persons on the ground. Four others on the ground suffered serious injuries. The airplane had struck a north-south line of trees in a right-wing-low attitude at a height of 65 feet agl. About 270 feet beyond the first tree strikes, the airplane struck a palm tree at 20 feet agl. The airplane then grazed the northeast corner of a house and subsequently impacted the next two houses along the street. A post-crash fire destroyed the airplane and the second and third homes.

Investigators found the wreckage fragmented and severely burned but uncovered no pre-impact structural, engine or control failures. They did find some parts of the cockpit outside of the post-impact fire zone and were helped by discolorations and/or soot deposits on those parts. For example, the instrument panel deck skin that was found outside the area where the post-crash fire occurred showed signs of thermal damage. Areas of the underside of this component exhibited discolored primer paint, patches of charred/bubbling paint and soot deposits, all of which were consistent with an inflight fire.

The instrument panel glareshield showed thermal damage at the attachment point. The cabin door — found about 60 feet away from the main wreckage — was unburned; its latching pins were undamaged. However, numerous soot deposits had accumulated on the interior side of this door. All of this was consistent with an inflight fire. The undamaged latching pins and the location and existence of the observed trailing soot deposit are consistent with the pilots having opened the cabin door to vent smoke.

Recovered flight instruments, cockpit avionics, controls, switches and circuit breakers exhibited severe post-impact fire damage and yielded no usable information regarding their precedent configuration or condition. A component of the weather radar antenna assembly and some attached electronic circuit boards exhibited severe impact and thermal damage; however, no evidence of arcing or other electrical faults was observed.

Investigators noted that most of the insulation on the aircraft’s wiring had burned off. Some of the insulation was polyvinyl chloride (PVC) material that can produce incapacitating fumes when burned. Neither Cessna nor other manufacturers have incorporated PVC-insulated wiring in new designs since the early 1970s. However, the FAA permitted the continued use of PVC-insulated wiring in airplanes — including Cessna 310s — in which it was already being installed. Because PVC-insulated wiring discovered in the wreckage had identifying numbers consistent with wiring commonly used by Cessna, it is likely that Cessna installed the PVC wiring in the accident airplane when it built it in 1977.

Investigators turned to the airplane’s operational and maintenance history and ultimately focused on a discrepancy reported with the weather radar system. On July 9 — the day before the accident — a NASCAR pilot wrote on a discrepancy form that the “radar went blank during cruise flight. Recycled — no response . . . smell of electrical components burning turned off unit — pulled radar breaker — smell went away. Radar inop.” The company pilot told investigators that he documented and reported the weather radar discrepancy to NASCAR personnel, leaving the white original page in the discrepancy binder in the airplane and providing the yellow copy to the director of maintenance (DOM), in accordance with the company’s SOPs. However, investigators found that no corrective action was recorded on the original white page of this discrepancy form. “Additionally,” says the Safety Board, “NASCAR Aviation Division personnel could not produce the yellow copy of this form or any other written documentation indicating that any troubleshooting or corrective maintenance actions had been taken to resolve the discrepancy before the accident flight.”

NASCAR’s corporate aviation division at that time operated a fleet of nine airplanes, including seven jets, one turboprop and the accident airplane. NASCAR employed 10 maintenance technicians and about 25 pilots. The department flew some 1,950 flights per year for a total fleet use of about 2,500 to 3,000 flight hours. NASCAR purchased the Cessna 310 in March 1995. It was based at Daytona and used primarily to transport parts, goods and documents rather than personnel. However, said investigators, the aircraft was used occasionally by the commercial pilot/physician for personal flights.

NASCAR’s policies did not permit any pilot who was not an ATP to act as PIC in a company airplane; therefore, the commercial pilot had to be accompanied by the ATP on personal flights. The commercial pilot was 53 years old and held single- and multiengine land and instrument ratings. He had 276 total flight hours, 106 hours of which were in multiengine airplanes, 26 hours of which were in Cessna 310s. The ATP-rated safety pilot was typed in the Cessna Citation (500, 550 and 600), Dassault Falcon (50 and 2000), British Aerospace HS-125, Beechcraft Premier IA, and Learjet 60. He had accumulated 10,580 total flight hours, 67 hours of which were in Cessna 310 airplanes. He had flown about 50 and 17 hours, respectively, in the 90 and 30 days before the accident flight. Both pilots had completed Cessna 310 proficiency training on Jan. 25, 2007.

NASCAR’s aviation department was operated under FAR Part 91 and, thus, was not required by the FAA to establish official SOPs. The department did develop an SOP manual containing its policies and procedural guidance. However, said the Safety Board, investigators found evidence that the SOP guidance was neither consistently updated nor adhered to by company personnel. Investigators gave as an example a NASCAR SOP that says company airplanes were for corporate use and that a pilot acting as PIC on a NASCAR airplane must hold an ATP certificate. Yet, the commercial pilot, who was not ATP rated, was permitted to fly the accident airplane for personal use. The guidance contained in the SOP manual was also not readily accessible to company personnel and, therefore, was not often referenced. When investigators asked NASCAR’s aviation director for a copy of the SOP manual, he could not immediately locate one.

The SOPs did not contain any specific information about the methods, procedures, or tools to be used for scheduling or tracking airplane maintenance, and evidence indicates that maintenance information was not accessible to all NASCAR aviation division personnel. The Safety Board gave these examples:

Although the DOM used maintenance tracking computer programs to track scheduled maintenance requirements on all the NASCAR airplanes, other NASCAR personnel did not have access to these programs. Maintenance technicians had to contact the DOM to get maintenance information for the airplanes on which they worked.

NASCAR did not have a communication procedure for providing flight operations personnel (pilots and schedulers) with airplane airworthiness information. The SOP indicated that the DOM was ultimately responsible for ensuring that all NASCAR airplanes were maintained in an airworthy condition at all times and for releasing airplanes for flight after maintenance; however, the SOP did not specify a means for the DOM to communicate the maintenance status of an airplane to anyone else within NASCAR.

NASCAR had no system through which any individual, including the DOM, could remove an airplane from the flight schedule because of airworthiness concerns. In practice, such a decision was made collaboratively by the aviation director, chief pilot and DOM. Planned and unplanned maintenance activities were finalized through a combination of verbal and e-mail coordination between those individuals.

As for the accident aircraft, the DOM, chief pilot and aviation director did discuss the weather radar discrepancy write-up, but none of these individuals took any actions to ensure that the discrepancy was addressed before agreeing that the airplane could be flown, said the Safety Board.

The chief pilot told investigators that the DOM had told him that: “It will be OK. Just tell [the ATP] not to turn it on.”

To its credit, NASCAR addressed all these “procedural concerns” immediately after the accident by updating SOPs, maintenance tracing and scheduling procedures. Improvements include:

Using aircraft status boards that detail the planned maintenance activity and general status for each airplane in the maintenance department and the schedule and availability of the maintenance technicians;

Placing an aircraft status log in each airplane’s maintenance discrepancy logbook for pilots to review before flight;

Implementing an improved maintenance-tracking tool that provides a report of upcoming scheduled maintenance for each airplane in NASCAR’s fleet and is available on-demand to pilots and maintenance and other NASCAR personnel;

Developing new serialized maintenance discrepancy forms that include a number of additional entry categories and enable better tracking of maintenance issues.

The Accident

Exactly what went on in the cockpit immediately before the crash will never be known. However, Safety Board investigators believe that an electrical problem existed in the weather radar components or related wiring. When, on the day before the accident flight, the pilot pulled the radar circuit breaker he “stopped a symptom [the burning smell] of the problem by removing electrical power from the circuit; however, it did not correct the underlying problem.”

Part 91 allows individual and companies to operate non-turbine-powered airplanes with non-critical inoperative equipment if the inoperative item is not required for flight and is either (1) removed from the airplane, the cockpit control placarded and the maintenance recorded or (2) deactivated and placarded as inoperative. Additionally, an appropriately rated pilot or mechanic must determine that the inoperative equipment does not constitute a hazard to flight. In this case, no one examined the airplane to investigate the discrepancy; no maintenance personnel stated that they had been in the airplane since the discrepancy was reported; and no company personnel (1) removed the airplane from service, (2) reset the circuit breaker, (3) placed a placard in the cockpit regarding the discrepancy or (4) deactivated the weather radar system, collaring the associated circuit breaker and placing a placard in the cockpit indicating the system’s inoperative status.

The Safety Board concluded that without examining the weather radar system, and then either removing the airplane from service or placarding the airplane and collaring the circuit breaker, as well as making a maintenance records entry, it was not permissible to fly the airplane under federal regulations.

“The final safeguard against the operation of an airplane with an unresolved maintenance discrepancy is a thorough pilot preflight inspection,” said the NTSB. “In this case, the Safety Board’s investigation showed that both pilots had access to information that could have alerted them that the accident airplane had an unresolved maintenance discrepancy on the morning of the accident and could have led them to take appropriate actions to ensure that the discrepancy was addressed before flight.

“Post-accident interviews indicated that the ATP was specifically advised of the weather radar discrepancy by a telephone call from NASCAR’s chief pilot the night before and in person by the maintenance technician who was responsible for the accident airplane the morning of the accident flight. On both occasions, the ATP dismissed the issue as unimportant.” He had sufficient information and cause to reject the aircraft, said the Board.

In its analysis, the Safety Board pointed out that on the day before the accident, the airplane was flown uneventfully for at least one hour after the pilot pulled the weather radar circuit breaker. In contrast, on the accident flight, the airplane was only airborne for about 10 minutes before the pilots reported a problem. The airplane crashed about two minutes later.

“The most likely reason for the rapid onset of the problem,” said the Safety Board, “is that one of the pilots reset the radar circuit breaker, thus reinitiating the development of the problem encountered on the previous flight. The circuit breakers would have been difficult for the ATP to reach and were next to the left leg of the commercial pilot, but nothing was found to indicate which pilot reset the circuit breaker or when.”

Investigators noted that “general aviation pilots often reset circuit breakers during preflight preparations unless the circuit breakers are placarded or collared to show that the associated system is to remain unpowered.” The accident airplane’s “Before Starting Engines” checklist included an item stating “Circuit Breakers — IN.” Therefore, the Safety Board concluded that it is likely that one of the pilots, consistent with routine and/or the “Before Starting Engines” checklist, reset the weather radar circuit breaker, which restored electrical power to the weather radar system’s wiring and resulted in the inflight fire.

Circuit Breaker Reset Hazards

The Safety Board believes all pilots need better training on circuit breaker dos and don’ts. Breakers are installed on aircraft to protect wiring. When current flow in a system exceeds a predetermined value for a period of time, the circuit breaker activates, or “trips,” to stop current flow through that system by breaking the electrical circuit. To use the system after a circuit breaker trips, a pilot must reset that circuit breaker manually. Historically, it has been common practice to reset a circuit breaker on an airplane one time after the breaker trips. The rationale behind this one-time reset practice is that if the circuit breaker tripped because of anything other than a transient or nuisance event and if the triggering condition was still present, the circuit breaker would trip again shortly after being reset.

Is this one-push technique sound? The Safety Board doesn’t think so. The one-push practice does not consider the cumulative nature of wiring damage and that the removal of power only temporarily stops the progression of the damage. “The aviation industry has begun to recognize the potential hazards of resetting non-critical circuit breakers even once. On Jan. 8, 2004, the FAA issued AC 120-80, InFlight Fires, which stated, in part: Crewmembers may create a potentially hazardous situation if they reset a circuit breaker without knowing what caused it to trip. A tripped circuit breaker should not be reset in flight unless doing so is consistent with explicit procedures specified in the approved operating manual used by the flight crew or unless, in the judgment of the captain, resetting the circuit breaker is necessary for the safe completion of the flight. Although this AC was directed at air carrier pilots, it is not without value for all of us.

The Safety Board says general aviation pilots still receive information contrary to the guidance in the AC. “For example, a May 2007 article in Flight Training, a periodical published by the AOPA, provided pilots the following advice: ‘Circuit breakers can be reset simply by pushing in the black button. Wait a few moments to allow the breaker to cool before resetting. Also, don’t try to reset a breaker more than once. If it pops again after the first reset, it’s a good indication that a serious problem exists somewhere in the circuit that demands professional attention.’”

When all was said and done, the Safety Board concluded that existing guidance in manuals provided by general aviation airplane manufacturers regarding the resetting of circuit breakers often does not consider the cumulative nature of wiring damage and that the removal of power only temporarily stops the progression of such damage. “If general aviation pilots, maintenance personnel and operators had a more thorough understanding of the potential hazards of a reset circuit breaker [as outlined in AC 120-80], they would be less likely to reset a tripped circuit breaker without knowing what caused that circuit breaker to trip.” Therefore, the Safety Board believes that the FAA should develop a safety alert for operators (SAFO) informing general aviation pilots and maintenance personnel of the circuit breaker policy contained in AC 120-80. The Safety Board further believes that the FAA should require that the contents of the SAFO be included in initial and required biennial training for general aviation pilots and maintenance personnel. A good idea, I think.

Finally, the Safety Board would like to see all corporate operators employ some sort of safety monitoring system and points out that the NBAA is leading the way in helping members establish such systems. This too, in my opinion, is a good idea and the NBAA can be a terrific resource to any corporate flight department setting out to improve its SOPs and SMS program.

http://www.aviationweek.com

[Changes in Latitudes]

Circuit Breaker Reset Hazards

The Safety Board believes all pilots need better training on circuit breaker dos and don’ts. Breakers are installed on aircraft to protect wiring. When current flow in a system exceeds a predetermined value for a period of time, the circuit breaker activates, or “trips,” to stop current flow through that system by breaking the electrical circuit. To use the system after a circuit breaker trips, a pilot must reset that circuit breaker manually. Historically, it has been common practice to reset a circuit breaker on an airplane one time after the breaker trips. The rationale behind this one-time reset practice is that if the circuit breaker tripped because of anything other than a transient or nuisance event and if the triggering condition was still present, the circuit breaker would trip again shortly after being reset.

Is this one-push technique sound? The Safety Board doesn’t think so. The one-push practice does not consider the cumulative nature of wiring damage and that the removal of power only temporarily stops the progression of the damage. “The aviation industry has begun to recognize the potential hazards of resetting non-critical circuit breakers even once. On Jan. 8, 2004, the FAA issued AC 120-80, InFlight Fires, which stated, in part: Crewmembers may create a potentially hazardous situation if they reset a circuit breaker without knowing what caused it to trip. A tripped circuit breaker should not be reset in flight unless doing so is consistent with explicit procedures specified in the approved operating manual used by the flight crew or unless, in the judgment of the captain, resetting the circuit breaker is necessary for the safe completion of the flight. Although this AC was directed at air carrier pilots, it is not without value for all of us.

The Safety Board says general aviation pilots still receive information contrary to the guidance in the AC. “For example, a May 2007 article in Flight Training, a periodical published by the AOPA, provided pilots the following advice: ‘Circuit breakers can be reset simply by pushing in the black button. Wait a few moments to allow the breaker to cool before resetting. Also, don’t try to reset a breaker more than once. If it pops again after the first reset, it’s a good indication that a serious problem exists somewhere in the circuit that demands professional attention.’”

When all was said and done, the Safety Board concluded that existing guidance in manuals provided by general aviation airplane manufacturers regarding the resetting of circuit breakers often does not consider the cumulative nature of wiring damage and that the removal of power only temporarily stops the progression of such damage. “If general aviation pilots, maintenance personnel and operators had a more thorough understanding of the potential hazards of a reset circuit breaker [as outlined in AC 120-80], they would be less likely to reset a tripped circuit breaker without knowing what caused that circuit breaker to trip.” Therefore, the Safety Board believes that the FAA should develop a safety alert for operators (SAFO) informing general aviation pilots and maintenance personnel of the circuit breaker policy contained in AC 120-80. The Safety Board further believes that the FAA should require that the contents of the SAFO be included in initial and required biennial training for general aviation pilots and maintenance personnel. A good idea, I think.

Finally, the Safety Board would like to see all corporate operators employ some sort of safety monitoring system and points out that the NBAA is leading the way in helping members establish such systems. This too, in my opinion, is a good idea and the NBAA can be a terrific resource to any corporate flight department setting out to improve its SOPs and SMS program.

I caught that this morning. Glad you posted it up, as I have seen so many poor circuit breaker procedures in my travels as I am sure most have.
This is a must read!

[Dagwood]

Slightly off topic, but had a discussion with a CFI about electrical fires. The POH states something like Master Off, all electrics off, extinguish fire. If electrical power is required for flight, Master On, necessary switches on one at a time ect.

This sound good in theory, but you have to remember that the possibility of the fire restarting is there, as well as your fire extinguisher is now depleted from putting out the fire the first time.


I always carry a portable VHF and GPS so I never will have to turn on the Master again.
Something to think about....

[Hedley]

the Safety Board concluded that it is likely that one of the pilots, consistent with routine and/or the “Before Starting Engines” checklist, reset the weather radar circuit breaker, which restored electrical power to the weather radar system’s wiring and resulted in the inflight fire

So the accident was caused by the checklist?

[MUSKEG]

I think this is just another case of Pilots turning on everthing that they can whether needed or not. In this case the ATP did not communicate to the flying pilot the reason for the pulled CB. I exhaust every possible other way to get the job done before I reset a CB. They are usually blown for a very sinister reason. However this accident belongs to the ATP. He knew why the CB was pulled and because it wasn't important to him he shrugged it off.

[The Old Fogducker]

Clunkdriver ... way off topic, but do you recall the CF-100 crash at the London Airshow in roughly 1955?

On topic ... even though I have an electronics background, I hadn't considered the effects of multiple resets causing cumulative damage to wiring because I was thinking theoretically, the CB is sized to protect the wire from heating to the point of insulation damage.

Interesting stuff.

Fog

[The Old Fogducker]

Clunk:

I was in the crowd that day, and during the process of disintegration, the empenage landed on the ramp about 20 feet from me as I stood among a line of RCAF Mustangs on the north side of the ramp . My next door neighbour was only 10 feet away from the impact point ... and he fainted on the spot. That was to be the first time my life was almost cut short.

I can still recall that event like it happened an hour ago ... the AC loss of position in the formation on the downwind to base leg turn, the series of black puffs of smoke from the exhaust, the two lead AC crossing maybe 50 feet above the heads of the crowd on the ramp, the third AC crossing left to right and then noticing "things" coming off the airplane that at first I thought might be pictures of the airport taken by the recce boys the day before and were now being dropped to the crowd, the pitch up and then in-flight breakup of the airplane, ... seeing the canopy deploy and the ejection take place, another chute come out, with the crew member only partially getting out of the airplane, watching it tumble end over end and impact the ground west side of the airport and the huge black smoke plume and flame.

I remember how we ran from side to side trying to avoid that whole tail assembly as it came out of the sky into the crowd of spectators.

After the crash, I got swept up in the crowd running to the crash site and ghouls were picking up pieces of the airframe for souvenirs. I wanted something "special" to take home and saw a helmet and parachute lying near a fence post on the western boundary of the airport. Just as I was reaching down to pick the helmet up to take home, I realized it still had the Nav's head in it. Took maybe 3 weeks before I got a full night's sleep without nightmares after seeing that.

I've tried to locate some film footage of that day for decades, but have not been successful. Even some BFSOs have made enquiries to no avail.

I now return you to the topic of circuit breaker resets ...

Fog

[HS-748 2A]

That's some pretty heavy duty stuff Fog.

Wow.

[pelmet]

[quote="clunckdriver"]I find after the third reset they tend to get too hot to hold in with a finger, a pencil will do a great job in holding the CB in and avoiding burnt finger tips! {sorry, just couldnt contain myself, this is based on something that took place years ago in the RCAF on a CF 100 outfit, belive it or not!} This particular GIB rose to senior rank and then joined DOT/TC, actually a good guy apart from this one SNAFU.[/quote]


The AC DC-9 was not much different, although the fire may have happened anyways, they reset the breakers several times.

[Hedley]

Start reading here:

http://en.wikipedia.org/wiki/Air_Canada_Flight_797

The flight crew, whom I think did a fantastic job, were
crapped upon by a great height by the non-flying
bureaucrats.

When Captain Cameron was interviewed on Mayday 'Fire Flight' he says "all I know was that I did the best I could."

I sincerely doubt that any of the non-flying chairborne
bureaucrats who so severely criticized Don could have
done half as good a job as he did.

You might recall a similar incident, with a fire
on-board an airliner:

http://en.wikipedia.org/wiki/Swissair_Flight_111

Compare the number of survivors of the two flights.

[Hedley]

Here's an interesting accident:

http://en.wikipedia.org/wiki/EgyptAir_Flight_990

The exact cause of the crash is disputed. Egyptian investigators concluded that the aircraft crashed as a result of mechanical failure, while U.S. investigators concluded the aircraft was deliberately crashed in an apparent suicide.

The NTSB's final report:

“ The National Transportation Safety Board determines that the probable cause of the EgyptAir flight 990 accident is the airplane's departure from normal cruise flight and subsequent impact with the Atlantic Ocean as a result of the relief first officer's flight control inputs. The reason for the relief first officer's actions was not determined. ”


The ECAA's final report, based largely on the NTSB's, came to different conclusions:

“ 1. The Relief First Officer (RFO) did not deliberately dive the airplane into the ocean.

The investigation and its results drew criticism from the Egyptian Government, which advanced several alternative theories about mechanical malfunction of the aircraft. In Western countries, the Egyptian rejection of the NTSB report was attributed to a strong Egyptian cultural aversion to suicide.

Obviously, accident investigations are never politically influenced

[ahramin]

As a friend of mine put it back at the time "They had two more pilots on board. Axe the door, axe both pilots, and figure it out later."

[RFlyer]

Interesting thread. For us renters out there, take care if you ever rent a plane with a popped breaker. Who knows whether it tripped bcs it was doing its job, because someone pulled it for some reason, etc. The checklist normally says check circuit breakers, which I've always interpreted to mean "make sure they are all pushed in". Obviously that could be a fatal mistake and the correct course of action if checking a breaker reveals it is in the OFF position should perhaps be to discuss with CFI first. In my experience people are discouraged from writing snags down in the journey log because it can needlessly ground the plane if the report is unfounded. Instead, post-its are placed into the log with a message indicating what the previous pilot is reporting.

Anyway, I'm going to be more careful as a result of reading this thread.

Thanks for posting.

RF

[Cat Driver]

should perhaps be to discuss with CFI first.

The best person to discuss it with would be one of the maintenance people as they will usually have a better understanding of the subject.

[pelmet]

The DC-9 fire may have happened anyways, but they were resetting CB's over and over for a motor. Not something I would suggest doing.

[SeptRepair]

Just last year we had a good scare all because of a CB.

CADORS Number: 2008P1057 Reporting Region: Pacific

Occurrence InformationOccurrence Type: Incident Occurrence Date: 2008/06/28
Occurrence Time: 1800 Z Day Or Night: day-time
Fatalities: 0 Injuries: 0

Canadian Aerodrome ID: Aerodrome Name:
Occurrence Location: 18 NM WSW of Victoria Province: British Columbia
Country: CANADA World Area: North America

Reported By: NAV CANADA AOR Number: 95695-V1
TSB Class Of Investigation: 5 TSB Occurrence No.: A08P0198
Event InformationDiversion
Electrical problem
Smoke - cockpit
Aircraft InformationFlight #:
Aircraft Category: Aeroplane Country of Registration: CANADA
Make: MARTIN Model: JRM 3
Year Built: 1945 Amateur Built: No
Engine Make: CURTISS WRIGHT Engine Model: R3350-24WA
Engine Type: Reciprocating Gear Type:
Phase of Flight: Cruise Damage: No Damage
Owner: COULSON AIRCRANE LTD Operator: COULSON AIRCRANE LTD. (4912)
Operator Type: Commercial

Detail InformationUser Name: Matthews, Meghan
Date: 2008/06/30
Further Action Required: No
O.P.I.: Maintenance & Manufacturing
Narrative: COULSON AIRCRANE LTD Martin Mars JRM3, VFR flight plan from Sproat Lake to Redding, California, returned to base due to possible fire in cockpit. Aircraft landed safely and closed flight plan.

User Name: Matthews, Meghan
Date: 2008/07/04
Further Action Required: No
O.P.I.: Maintenance & Manufacturing
Narrative: UPDATE from Maintance & Manufacturing: COULSON AIRCRANE LTD Martin Mars JRM3, VFR flight plan from Sproat Lake to Redding, California, returned to base due to propeller booster circuit breaker failure with smoke present in cockpit. Circuit breaker failure occurred during feather selection of #4 engine. Feather selection test was required after removal and installation of #4 propeller. Follow up maintenance investigation revealed pitted propeller booster breaker contacts which resulted in high resistance overheating. Propeller booster circuit wiring and component inspection carried out with no defects found. Circuit Breaker replaced with serviceable unit and all 4 engine propeller feather circuits were functionally checked serviceable. A test flight was carried out and #4 propeller feather circuit checked normal. The propeller booster circuit breaker is common to all four propeller circuits, and failure was not related to any maintenance performed

User Name: Samson, Donna
Date: 2008/07/10
Further Action Required: No
O.P.I.: Maintenance & Manufacturing
Narrative: UPDATE / Add Info from TSB: The Coulson Flying Tankers Martin MARS MJRM-3 aircraft took off from Sproat Lake for Lake Shasta. En route the crew attempted to feather the No. 4 engine (Curtiss Wright R3350-24WA Cyclone) as part of a maintenance flight check. A circuit breaker failed during the feathering and smoke appeared in the cockpit. The crew shut down the affected circuit and the smoke cleared. The feathering of the No. 4 engine was completed manually and the aircraft returned to Sproat Lake, where it landed without further event. The circuit breaker was replaced, and the prop circuits, component lines and prop motor circuits were inspected, and the aircraft was returned to service.

Please note that for the most part, CADORS reports contain preliminary, unconfirmed data which can be subject to change

[Big Pistons Forever]

I have a problem with one size fits all generalizations, like never push a popped CB in. I had a CB on the fuel flow meter pop a few weeks ago, on a light twin I fly. It was a 2 amp CB and a carefull look at the electrical load meter showed normal voltage and draw and no other electrical equipment was acting abnormally. So I pushed it back in and the fuel meter came back to life. I continued to carefully monitor the electrical system and there was no issues. The CB never popped again. Sometimes 30 yr old CB's will get weak and pop on their own. I will however get it replaced at the next 100 hr. The day of the event I was flying day VFR and returning the aircraft to maintainance would have lost 6 hrs of revenue flying, plus the non rev back to the home airport. Now if it was a high amp CB or there was any indication of high draw or other electrical malfunctions than, or I was IFR it would have been another story and I would not have resest the CB even once. The key is knowing your systems and informed risk management.

[Hedley]

Sometimes 30 yr old CB's will get weak and pop on their own

They surely can. However, what pilots need to know is that
resetting circuit breakers - even once - is a very high risk
activity, which may result in an inflight fire and the deaths
of all the people on board, plus casualties on the ground.

And the question pilots need to ask themselves:

"Is getting that system working again worth dying for?"

If the answer is yes, heck yeah, push it in.

What makes me nervous is when I see people indulging
in high risk activities, and they DON'T KNOW that they
are in fact taking big risks, often for very marginal
returns.

[Big Pistons Forever]

Hedly

All of flying is a constant exercise in risk management. I am comfortable with my decision because of the particular circumstances of that event and because I have a full understanding of how the affected system works. There are probably many pilots who push in CB's without any real understanding of the aircraft electrical system. That is IMO an example of uninformed risk takeing. But at the end of the day the type and kind of risks any particular pilot is willing to take is a personal decision. I for example, will no longer fly single engine aircraft at night under any circumstances, yet I know numerous very able pilots who will.

[Hedley]

There is something called a cost/benefit ratio - a concept
which can be applied here.

It's not just about the risk - it's about the return, too.
Specifically, the relationship (eg ratio) between the risk
and the return.

eg: high risk activity, low return: don't do that (obvious)

eg: low risk activity, high return: do that (obvious)

Inbetween are the shades of grey that you never
know when you are going to be post-humously
judged upon.

Remember the definition of an accident investigation
board: six guys spend six months deciding what
two guys should have done in 20 seconds.

[oldtimer]

I wonder how many pilots say they will never reset a popped c/b and then go and reset one if it pops?.
In the King Air 350, I usually attempt a rectification and then a reset of the landing gear control c/b, a small 2 amp one, because it is designed to be "popped" to limit the time the landing gear motor runs, again to limit heat buildup. After 15 seconds of operation, if the landing gear motor has not stopped, bus voltage is sent to the c/b to pop it. Reselect gear down, reset the breaker and then let things cool down.
How many 'Ho pilots pop the boost pump c/b's to stop them from operating after landing. I mean the small pumps designed to eliminate fuel vapor locks, not the main boost pumps.

[pelmet]

Of course you are going to push a landing gear C/B back in. It is the unnecessary ones that are questionable. Repeated toilet flush motor resets seem unnecessary.

Someone said they reset a fuel flow C/B in flight after looking at the loadmeter and voltage indications. I'm not an electrical expert but one would think that if there HAD BEEN a large draw, it would be before the fuel flow CB popped and would happen again when the breaker was reset.

And 99 times out of 100, pushing the breaker back in won't cause a problem so you get lulled into thinking it is O.K.

[Dagwood]

Of course you are going to push a landing gear C/B back in.

Actually, all retractable aircraft are required to have a secondary method to lower the gear for situations like this.

Is avoiding the gear crank really a good reason to risk an inflight fire? Not in my books...

[Big Pistons Forever]

Someone said they reset a fuel flow C/B in flight after looking at the loadmeter and voltage indications. I'm not an electrical expert but one would think that if there HAD BEEN a large draw, it would be before the fuel flow CB popped and would happen again when the breaker was reset.
.

If any CB pops the first question I ask myself is "is this a isolated event or the first indication of a larger electrical problem" That is why I check the volt/load meters right away. IF I elect to reset the CB then I will very carefully monitor the volt/load meter and bbe prepared to immediately pull the CB and/or turn off the generator and battery master swithches at the first sign of an abnormal draw. However it should be noted that most CB's are not the pullable type and so there is a possibilty of the CB frying in the circuit on (in) position and therefore not being able to pop. This could obviously lead to overheating and a possible fire. The only way to address this is to immediately shut down all aircraft power. Note the above comments concern a typical light piston twin electrical system. Large aircraft have more/different considerations.

[pelmet]

[/quote]
If any CB pops the first question I ask myself is "is this a isolated event or the first indication of a larger electrical problem" That is why I check the volt/load meters right away. IF I elect to reset the CB then I will very carefully monitor the volt/load meter and be prepared to immediately pull the CB and/or turn off the generator and battery master swithches at the first sign of an abnormal draw. However it should be noted that most CB's are not the pullable type and so there is a possibilty of the CB frying in the circuit on (in) position and therefore not being able to pop. [/quote]

Most of the CB's in a larger plane are pullable. On top of that much flying is done in pitch black or all white outside. Suggest you leave the fuel flow CB out in flight as it may not be the best time to be turning off a generator or master switch. Or even if it is a nice day. The fuel flow guage isn't really much of a loss anyway.