If Only.......
Thread Starter
If Only.......
Below is a quote from an FAA AD (Superior Airparts - IO360 crankshafts) that, in my opinion, perfectly exemplifies how risk management principles should be applied to the maintenance and development of ALL aviation regulation. There is no room in this model for axe grinding, personal opinion, weasel words or rubbish. If only such a model was applied here...
Benefits
The FAA found that SAP, the manufacturer of the crankshaft assemblies, sold 192 SAP crankshaft assemblies to date: 115 of these crankshaft assemblies are estimated to be installed on type certificated airplanes and the remaining 77 crankshaft assemblies are estimated to be installed on experimental aircraft.
The FAA's risk analysis indicates that 100 percent of crankshaft assembly failures will destroy the engine. Using the historical incident data (2000-2014), the FAA assumes that 7 , 24.4 percent of crankshaft assembly failures will result in aircraft hull loss while 22 percent of crankshaft assembly failures will result in fatalities. There would be an average of 2.1 fatalities per each crankshaft assembly accident. Applying these probabilities to the estimated 115 crankshaft assemblies installed on type certificated airplanes, the FAA estimates that if these crankshaft assemblies are not replaced and continue to be used in these airplanes, this will result in 53 fatalities (2.1 fatalities per crankshaft accident x 22 percent probability of a crankshaft assembly failure resulting in fatalities x 115 crankshaft assemblies) and 28 aircraft losses (24.4 percent probability of a crankshaft assembly failure destroying the airplane). This AD will prevent all 53 fatalities and 28 aircraft losses.
Using an average price of $50,000 for a small single engine airplane, an average price of $30,000 for a 360-series engine and the Department of Transportation's $9.6 million estimate for the Value of Statistical Life (VSL) from the “Revised Departmental Guidance on Valuation of a Statistical Life in Economic Analysis,”6 the FAA estimated this AD final rule will result in monetized benefits of $512.8 million.7
Costs of Compliance The costs of compliance with this AD consist of the cost to remove and replace a crankshaft assembly.
The FAA estimates that this AD will affect 115 crankshaft assemblies installed on airplanes of U.S.registry. This cost estimate does not include 77 SAP crankshaft assemblies installed on experimental engines since this AD does not apply to these engines. The estimated compliance cost per crankshaft assembly is identified below. Labor cost = 61 hours per crankshaft assembly replacement x $85 Hourly Wage = $5,185.Equipment costs per crankshaft assembly replacement = $9,636(Source: Average of the two vendors).$5,185 labor per crankshaft assembly + $9,636 equipment costs per crankshaft assembly replacement = $14,821 compliance cost per engine.The total costs to U.S. operators is $1,704,415 ($14,821 x 115), or $119,309 in annualized costs in perpetuity using a 7 percent discount rate. There are no additional costs after removing and replacing the crankshaft assembly.
Therefore, the FAA estimates that the net benefit of this final rule will be $511.1 million ($512.8 million benefits -$1.7 million costs), or $35.77 million in annualized net benefits using a 7 percent discount rate in perpetuity
The FAA found that SAP, the manufacturer of the crankshaft assemblies, sold 192 SAP crankshaft assemblies to date: 115 of these crankshaft assemblies are estimated to be installed on type certificated airplanes and the remaining 77 crankshaft assemblies are estimated to be installed on experimental aircraft.
The FAA's risk analysis indicates that 100 percent of crankshaft assembly failures will destroy the engine. Using the historical incident data (2000-2014), the FAA assumes that 7 , 24.4 percent of crankshaft assembly failures will result in aircraft hull loss while 22 percent of crankshaft assembly failures will result in fatalities. There would be an average of 2.1 fatalities per each crankshaft assembly accident. Applying these probabilities to the estimated 115 crankshaft assemblies installed on type certificated airplanes, the FAA estimates that if these crankshaft assemblies are not replaced and continue to be used in these airplanes, this will result in 53 fatalities (2.1 fatalities per crankshaft accident x 22 percent probability of a crankshaft assembly failure resulting in fatalities x 115 crankshaft assemblies) and 28 aircraft losses (24.4 percent probability of a crankshaft assembly failure destroying the airplane). This AD will prevent all 53 fatalities and 28 aircraft losses.
Using an average price of $50,000 for a small single engine airplane, an average price of $30,000 for a 360-series engine and the Department of Transportation's $9.6 million estimate for the Value of Statistical Life (VSL) from the “Revised Departmental Guidance on Valuation of a Statistical Life in Economic Analysis,”6 the FAA estimated this AD final rule will result in monetized benefits of $512.8 million.7
Costs of Compliance The costs of compliance with this AD consist of the cost to remove and replace a crankshaft assembly.
The FAA estimates that this AD will affect 115 crankshaft assemblies installed on airplanes of U.S.registry. This cost estimate does not include 77 SAP crankshaft assemblies installed on experimental engines since this AD does not apply to these engines. The estimated compliance cost per crankshaft assembly is identified below. Labor cost = 61 hours per crankshaft assembly replacement x $85 Hourly Wage = $5,185.Equipment costs per crankshaft assembly replacement = $9,636(Source: Average of the two vendors).$5,185 labor per crankshaft assembly + $9,636 equipment costs per crankshaft assembly replacement = $14,821 compliance cost per engine.The total costs to U.S. operators is $1,704,415 ($14,821 x 115), or $119,309 in annualized costs in perpetuity using a 7 percent discount rate. There are no additional costs after removing and replacing the crankshaft assembly.
Therefore, the FAA estimates that the net benefit of this final rule will be $511.1 million ($512.8 million benefits -$1.7 million costs), or $35.77 million in annualized net benefits using a 7 percent discount rate in perpetuity
Some 257 four-cylinder Superior and Lycoming engines are now subject to a new airworthiness directive requiring crankshaft replacement within 25 hours. A Notice of Proposed Rulemaking was published in February but the new AD goes into effect on Jan. 15, 2021. The engines include Superior’s own IO-360 and O-360s as well as certain Lycoming 360-series models that may have had the crankshaft installed as a replacement part. The AD lists specific serial numbers for the parts, which were delivered between 2012 and 2014.According to the FAA, the AD “was prompted by three crankshaft assembly failures that resulted in the loss of engine power and immediate or emergency landings. The FAA is issuing this AD to prevent failure of the crankshaft assembly. The unsafe condition, if not addressed, could result in failure of the engine, in-flight shutdown, and loss of the airplane.” The accidents happened between March 2017 and October 2018, and all were in training aircraft.
The FAA says that crankshaft failures resulted from “residual white layer formation, also known as a compound layer, on certain crankshaft assemblies as a result of improper manufacturing by a third-party vendor.” Superior, however, disputed the FAA’s findings, saying that the cranks had proper material and heat treatment, and that the fatigue fractures noted in the three broken cranks were not consistent with a too-thick “white layer.”
“As supported by the reports, the FAA finds that white layer contributed to the early crack initiation and, on all failed crankshaft assemblies, exceeded OEM specifications,” the agency said. Superior also contended that the engines had been subjected to “misuse, abuse, or lack of lubrication,” but the FAA also rejected that argument.
Superior has not said what it will do for owners of the affected engines, nor is it clear that replacement crankshafts will be immediately available. In general, engine shops are reporting shortages of certain critical parts due to COVID-19 slowdowns. It’s also worth noting that the AD applies to certified aircraft and not, explicitly, experimental/amateur-built aircraft, which have been touched by the issue. However, most builders are expected to abide by the terms of the AD and seek replacement crankshafts even if they aren’t legally required to
The FAA says that crankshaft failures resulted from “residual white layer formation, also known as a compound layer, on certain crankshaft assemblies as a result of improper manufacturing by a third-party vendor.” Superior, however, disputed the FAA’s findings, saying that the cranks had proper material and heat treatment, and that the fatigue fractures noted in the three broken cranks were not consistent with a too-thick “white layer.”
“As supported by the reports, the FAA finds that white layer contributed to the early crack initiation and, on all failed crankshaft assemblies, exceeded OEM specifications,” the agency said. Superior also contended that the engines had been subjected to “misuse, abuse, or lack of lubrication,” but the FAA also rejected that argument.
Superior has not said what it will do for owners of the affected engines, nor is it clear that replacement crankshafts will be immediately available. In general, engine shops are reporting shortages of certain critical parts due to COVID-19 slowdowns. It’s also worth noting that the AD applies to certified aircraft and not, explicitly, experimental/amateur-built aircraft, which have been touched by the issue. However, most builders are expected to abide by the terms of the AD and seek replacement crankshafts even if they aren’t legally required to
What is the "white layer" to which they refer?
Thread Starter
White layer is a hard but brittle iron nitride intermetallic compound that forms as a surface layer during nitriding. Being brittle, if the layer is thick enough, it can crack and thus form the start of a fatigue crack. Hence nitridng specs allow a maximum thickness - and at University I sucked at metallurgy, so thats all I know.
FAA says SAPs cranks have too much white layer.
FAA says SAPs cranks have too much white layer.
