King Air down at Essendon?
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Balanced Field Length takeoff - a note
Probably as a result of pilot theory training courses, which tend to get a bit preoccupied with BFL operations, many pilots appear to hold the view that BFL is a bit sacrosanct. Nothing could be further from the truth. BFL calculations have the one advantage that they are the simplest (and, when done by the pilot, the quickest) way to run field length limited calculations.
While it is noted that some aircraft AFMs only provide data for BFL calculations or may not provide much flexibility for unbalanced calculations, where the option exists, it usually will give a better weight outcome if the calculation is run for an unbalanced situation.
Considering A37575's post, a nasty obstacle runway is a common example where unbalancing TODR and ASDR may provide a useful weight advantage. Note, I am not familiar with the runway cited so I am not able to offer specific comment regarding the data cited.
Probably as a result of pilot theory training courses, which tend to get a bit preoccupied with BFL operations, many pilots appear to hold the view that BFL is a bit sacrosanct. Nothing could be further from the truth. BFL calculations have the one advantage that they are the simplest (and, when done by the pilot, the quickest) way to run field length limited calculations.
While it is noted that some aircraft AFMs only provide data for BFL calculations or may not provide much flexibility for unbalanced calculations, where the option exists, it usually will give a better weight outcome if the calculation is run for an unbalanced situation.
Considering A37575's post, a nasty obstacle runway is a common example where unbalancing TODR and ASDR may provide a useful weight advantage. Note, I am not familiar with the runway cited so I am not able to offer specific comment regarding the data cited.
Pending approval, here’s some of the report:
The airline transport pilot was departing for a repositioning flight. During the initial climb, the pilot declared an emergency and stated that the airplane "lost the left engine." The airplane climbed to about 120 ft above ground level, and witnesses reported seeing it in a left turn with the landing gear extended. The airplane continued turning left and descended into a building on the airfield. A postimpact fired ensued and consumed a majority of the airplane.
Postaccident examinations of the airplane, engines, and propellers did not reveal any anomalies that would have precluded normal operation. Neither propeller was feathered before impact. Both engines exhibited multiple internal damage signatures consistent with engine operation at impact. Engine performance calculations using the preimpact propeller blade angles (derived from witness marks on the preload plates) and sound spectrum analysis revealed that the left engine was likely producing low to moderate power and that the right engine was likely producing moderate to high power when the airplane struck the building. A sudden, uncommanded engine power loss without flameout can result from a fuel control unit failure or a loose compressor discharge pressure (P3) line; thermal damage prevented a full assessment of the fuel control units and P3 lines. Although the left engine was producing some power at the time of the accident, the investigation could not rule out the possibility that a sudden left engine power loss, consistent with the pilot's report, occurred.
A sideslip thrust and rudder study determined that, during the last second of the flight, the airplane had a nose-left sideslip angle of 29°. It is likely that the pilot applied substantial left rudder input at the end of the flight. Because the airplane's rudder boost system was destroyed, the investigation could not determine if the system was on or working properly during the accident flight. Based on the available evidence, it is likely that the pilot failed to maintain lateral control of the airplane after he reported a problem with the left engine. The evidence also indicates that the pilot did not follow the emergency procedures for an engine failure during takeoff, which included retracting the landing gear and feathering the propeller.
Postaccident examinations of the airplane, engines, and propellers did not reveal any anomalies that would have precluded normal operation. Neither propeller was feathered before impact. Both engines exhibited multiple internal damage signatures consistent with engine operation at impact. Engine performance calculations using the preimpact propeller blade angles (derived from witness marks on the preload plates) and sound spectrum analysis revealed that the left engine was likely producing low to moderate power and that the right engine was likely producing moderate to high power when the airplane struck the building. A sudden, uncommanded engine power loss without flameout can result from a fuel control unit failure or a loose compressor discharge pressure (P3) line; thermal damage prevented a full assessment of the fuel control units and P3 lines. Although the left engine was producing some power at the time of the accident, the investigation could not rule out the possibility that a sudden left engine power loss, consistent with the pilot's report, occurred.
A sideslip thrust and rudder study determined that, during the last second of the flight, the airplane had a nose-left sideslip angle of 29°. It is likely that the pilot applied substantial left rudder input at the end of the flight. Because the airplane's rudder boost system was destroyed, the investigation could not determine if the system was on or working properly during the accident flight. Based on the available evidence, it is likely that the pilot failed to maintain lateral control of the airplane after he reported a problem with the left engine. The evidence also indicates that the pilot did not follow the emergency procedures for an engine failure during takeoff, which included retracting the landing gear and feathering the propeller.
The ATSB report of ZCR's recent flights / maintenance is sketchy.
FlightAware shows ZCR returning to Essendon on Feb 4 at approx 2pm with a flight time of 1:24
But the ATSB does not show it flying on that day.
The ATSB lists ZCR as flying 6 hours on Feb 5, but flight aware has nothing on that day. ZCR has ADSB. I don't understand how a 6 hour flight could be unrecorded by FlightAware.
The RUMOUR I heard at the time was that it spent about 3 weeks in Adelaide unscheduled after a problem on the leg to Adelaide. The flight aware record supports this. The ATSB report does not mention this. although the flight it lists of Jan 13 when landing gear malfunction was reported may fit with this. At the time the 3rd hand rumour I had was that it was having work done on the FCU and that it was a repeat issue. I'll re-iterate that the rumour I had within days of the accident was 3rd hand. I cant vouch for it. But, it did spend time in Adelaide that corresponded with the rumour.
An FCU failure has precedent and in many ways fits the facts. But, the ATSB report doesn't acknowledge it.
and I don't understand why the 4 February flight in FlightAware returning from Adelaide does not appear in the list of recent flights in the report.
FlightAware shows ZCR returning to Essendon on Feb 4 at approx 2pm with a flight time of 1:24
But the ATSB does not show it flying on that day.
The ATSB lists ZCR as flying 6 hours on Feb 5, but flight aware has nothing on that day. ZCR has ADSB. I don't understand how a 6 hour flight could be unrecorded by FlightAware.
The RUMOUR I heard at the time was that it spent about 3 weeks in Adelaide unscheduled after a problem on the leg to Adelaide. The flight aware record supports this. The ATSB report does not mention this. although the flight it lists of Jan 13 when landing gear malfunction was reported may fit with this. At the time the 3rd hand rumour I had was that it was having work done on the FCU and that it was a repeat issue. I'll re-iterate that the rumour I had within days of the accident was 3rd hand. I cant vouch for it. But, it did spend time in Adelaide that corresponded with the rumour.
An FCU failure has precedent and in many ways fits the facts. But, the ATSB report doesn't acknowledge it.
and I don't understand why the 4 February flight in FlightAware returning from Adelaide does not appear in the list of recent flights in the report.
I think you're looking for something that is not there Old Akro, Presumably in order to produce the same outcome, we are talking about an FCU failure that produced an over torque on the left engine. I'm not sure that rudder boost would work in this condition but lets say it does and ques the pilot to apply left rudder. We would expect the flight path to veer to the right, we know by eye witnesses that it went left from rotation.The aircraft should still be quite controllable, accelerate quickly and climb away, unless he realised what was happening after applying left rudder trim, (I doubt you would need all of it) and pulled the left power lever back to flight idle, that would cause a huge yaw to the left, loss of performance and loss of control. It's more likely that the rudder trim was already in that position from the start of the takeoff run. I can't think of any other FCU fault that could cause the same outcome.
I would expect that the expert witnesses engaged by the families legal teams will go into more detail about this, so it will be interesting to see what happens. No doubt they will be picking the report apart right now.
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Here is a plausible theory as to how the rudder trim came to be in the full NL position. This is based on an experience I had whilst being on the King Air 200, many years ago:
The rudder trim position indicator is not a true indicator of the tab position. It is merely an indicator of where the wheel has been rotated to. The indicator is part of the wheel. It is all one assembly which connects to the drive shaft via a single (?) grub screw. Loosen the screw slightly and you can then remove the wheel/indicator assembly from the shaft.
Then, you can rotate the wheel, with the indicator moving in reduced proportion - despite now being completely separated from the shaft! As can be seen, the indicator is mechanically geared to the wheel. The indicator thus shows the rotational position of the wheel - not the position of the trim tab!
And when putting the wheel back onto the shaft, it is possible to put it on at any rotational position, thus rendering the indication completely invalid! So, for example, you could wind the trim to full NR, then remove the wheel/indicator assembly, then put it back on with the indicator centred. To a pilot, the rudder trim would then look to be set at neutral, when in reality the trim tab is fully to one side.
I experienced a situation where exactly this scenario may have played out. Myself and the other pilots noticed that the rudder trim position indicator was well to one side during the cruise when everything was perfectly trimmed out. This went on for several days. Incredibly, some pilots decided to manage the situation by centering the trim, then setting differential power in order to get the ball centered and wings level (!).
When I next flew the aircraft, and was manipulating the trim wheel, the assembly fell off the shaft and onto the floor. I simply picked it up and put it back on the shaft. The mystery was immediately revealed.
So, in the case of ZCR, could the wheel assembly have been dislodged, due the loose screw, then been put back on, but with the trim indicator now showing full NR trim? Did this operator use the same cleaners of the office to also give the aircraft interiors a vacuum and wipe?
The next pilot of the aircraft, whilst conducting his pretakeoff checks would have found the rudder trim to be indicating full NR. He would have been momentarily puzzled about this, but then wound the trim to centre the indicator. The indicator was then centered, but the trim tab was set to full nose-left.
The rudder trim position indicator is not a true indicator of the tab position. It is merely an indicator of where the wheel has been rotated to. The indicator is part of the wheel. It is all one assembly which connects to the drive shaft via a single (?) grub screw. Loosen the screw slightly and you can then remove the wheel/indicator assembly from the shaft.
Then, you can rotate the wheel, with the indicator moving in reduced proportion - despite now being completely separated from the shaft! As can be seen, the indicator is mechanically geared to the wheel. The indicator thus shows the rotational position of the wheel - not the position of the trim tab!
And when putting the wheel back onto the shaft, it is possible to put it on at any rotational position, thus rendering the indication completely invalid! So, for example, you could wind the trim to full NR, then remove the wheel/indicator assembly, then put it back on with the indicator centred. To a pilot, the rudder trim would then look to be set at neutral, when in reality the trim tab is fully to one side.
I experienced a situation where exactly this scenario may have played out. Myself and the other pilots noticed that the rudder trim position indicator was well to one side during the cruise when everything was perfectly trimmed out. This went on for several days. Incredibly, some pilots decided to manage the situation by centering the trim, then setting differential power in order to get the ball centered and wings level (!).
When I next flew the aircraft, and was manipulating the trim wheel, the assembly fell off the shaft and onto the floor. I simply picked it up and put it back on the shaft. The mystery was immediately revealed.
So, in the case of ZCR, could the wheel assembly have been dislodged, due the loose screw, then been put back on, but with the trim indicator now showing full NR trim? Did this operator use the same cleaners of the office to also give the aircraft interiors a vacuum and wipe?
The next pilot of the aircraft, whilst conducting his pretakeoff checks would have found the rudder trim to be indicating full NR. He would have been momentarily puzzled about this, but then wound the trim to centre the indicator. The indicator was then centered, but the trim tab was set to full nose-left.
Gosh. Maybe the PIC wasn’t the only slice of Swiss cheese.
The litigation will be very illuminating.
The litigation will be very illuminating.
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FGD, exactly why on preflight one would be wise to check the full travel of trim both directions. More likely to pick up oddities like you describe.
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And then, after having wound the trim back to centre, observing the position of the trim tab during the pre-flight walk around would have shown something was amiss.
And then, after having wound the trim back to centre, observing the position of the trim tab during the pre-flight walk around would have shown something was amiss.
Then removed all the inspection panels necessary to confirm that no control cable was fraying.
Then drained and replenished fuel to confirm that calculated and indicated equaled uploaded.
Then done an aircraft re-weigh to confirm that the loading and CofG data for the aircraft remained accurate.
Then...
If we didn’t and couldn’t make reasonable assumptions about the maintenance and operational history of the systems of the aircraft we fly, we’d never get off the ground.
Completely ridiculous LB. By your logic, maybe he should have sat all his CPL subjects again, a CPL and MECIR flight test again, before he went flying!
Visually checking a trim tab on a walk around is very simple, normal thing to do.
But you knew that. And I've probably taken the bait and given you the response you want.
Visually checking a trim tab on a walk around is very simple, normal thing to do.
But you knew that. And I've probably taken the bait and given you the response you want.
Neither you nor I know that he didn’t visually check the trim tab on the walk around.
Much of the reasoning in support of the PIC being the only piece of Swiss cheese is called “confirmation bias”. That’s why one ostensibly similar incident in the USA was chosen by FGD but not another. The other supported the inconvenient possibility that the left engine lost power due to a particular failure mode of the FCU, thus providing a reasonable and alternative explanation for the main reason why the aircraft performed so poorly after take off. Doesn’t excuse the pilot from responding adequately to the situation, provided that was the only thing wrong with the aircraft, but does strongly suggest there was more than one piece of Swiss cheese.
Much of the reasoning in support of the PIC being the only piece of Swiss cheese is called “confirmation bias”. That’s why one ostensibly similar incident in the USA was chosen by FGD but not another. The other supported the inconvenient possibility that the left engine lost power due to a particular failure mode of the FCU, thus providing a reasonable and alternative explanation for the main reason why the aircraft performed so poorly after take off. Doesn’t excuse the pilot from responding adequately to the situation, provided that was the only thing wrong with the aircraft, but does strongly suggest there was more than one piece of Swiss cheese.
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Completely ridiculous LB. By your logic, maybe he should have sat all his CPL subjects again, a CPL and MECIR flight test again, before he went flying!
Visually checking a trim tab on a walk around is very simple, normal thing to do.
But you knew that. And I've probably taken the bait and given you the response you want.
Visually checking a trim tab on a walk around is very simple, normal thing to do.
But you knew that. And I've probably taken the bait and given you the response you want.
FWIW
LB, no we don't know whether or not the tab was visually checked. I never said he didn't; you've taken my general statement and incorrectly applied it to the accident flight. Though I am wondering how well the CCTV picked up if there was an obvious pre flight walkaround, or not.
I dont see a lot of the "confirmation bias" you mention; I see a lot of discussion and theorising about how and why certain things might be. The report still leaves many people with unanswered questions because it seems many don't buy the sole cause rudder trim finding.
I predict a lawsuit, and an out of court settlement, over this accident.
Eddie, I did not intend there to be any irony. I was just adding to the ridiculousness, completely forgetting that the report mentioned previous extra training recommendations.
I dont see a lot of the "confirmation bias" you mention; I see a lot of discussion and theorising about how and why certain things might be. The report still leaves many people with unanswered questions because it seems many don't buy the sole cause rudder trim finding.
I predict a lawsuit, and an out of court settlement, over this accident.
Eddie, I did not intend there to be any irony. I was just adding to the ridiculousness, completely forgetting that the report mentioned previous extra training recommendations.
By that logic he should have run up the engines and operated all of the engine and propellor controls through their full range, then shut down and inspected the engines and propellers.
Then removed all the inspection panels necessary to confirm that no control cable was fraying.
Then drained and replenished fuel to confirm that calculated and indicated equaled uploaded.
Then done an aircraft re-weigh to confirm that the loading and CofG data for the aircraft remained accurate.
Then removed all the inspection panels necessary to confirm that no control cable was fraying.
Then drained and replenished fuel to confirm that calculated and indicated equaled uploaded.
Then done an aircraft re-weigh to confirm that the loading and CofG data for the aircraft remained accurate.
Control cable inspection is a maintenance function, not part of a diligent walk-around.
Fuel logs and delivery dockets, properly managed, would assure the correct fuel was on board.
If there is a configuration change, equipment added etc etc, only then is a re-weigh is needed.
Engine controls etc would be as you want them as part of the start up procedure and, if not, you'd soon correct it before it's an issue. Their functionality check was on the previous flight assuming no intervening maintenance on them.
Trim tab position, however, is part of a thorough walk-round. Doesn't sound as though you check them properly.