Originally Posted by Bell_ringer
(Post 9924723)
I did some analysis from the NTSB database for the date range chose by AA above. It does make some interesting reading.
My take on it is it's just trading one set of risks for another. Robinson risks: instructional environments, low time pilots, lower capability machine with smaller safety margins. Bell risks: more likely to be found working at more complex tasks. And, your point about comparing Part 91, the majority of Robinson op's, to the same for Bell, is a very good one. I did that for the same time period as before (1 Jan 2015 to 1 Apr 17), and the results were: Robinson: 70 accidents of which 6 involved fatalities Bell: 34 accidents of which 6 involved fatalities It's interesting that the ratio of fatalities to accidents remains approx. 2:1 with the Bell's higher, whether it be all operations or limited to only Part 91 op's. As for the beer bet ;-), if we restrict the hours to US civil (not military) hours only, I'll take that bet. I'd be willing to bet that Robinson hours actually exceed Bell hours in US civilian operations. At least in my neck of the woods Robinsons buzz around like honey bees all day long, but you rarely see a turbine helicopter of any type. And, according to the FAA civil aircraft registry, there are almost 3.5 times as many Robinsons as Bells registered: 2846 Robinsons of all types vs. 828 Bells of all types. Given the popularity in the US of Robinson helicopters for instruction, personal and light commercial use. could it be that the Bell fleet is working 3.5 times harder than the Robinson fleet? But...without any actual data on hours flown by helicopter types, it is admittedly difficult to come to a definitive conclusion. Nevertheless, when restricted to the US, all other data tends to suggests that the two fleets are roughly comparable, although the large number of Robinson aircraft registrations tends to tilt things a little in Robinson's favor. |
Originally Posted by gulliBell
(Post 9924733)
I'm not sure how many Bell helicopters breakup in flight with an experienced pilot/instructor at the controls. Probably zero would be my guess. The same can't be said for Robinson helicopters.
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Originally Posted by aa777888
(Post 9924922)
according to the FAA civil aircraft registry, there are almost 3.5 times as many Robinsons as Bells registered: 2846 Robinsons of all types vs. 828 Bells of all types. Given the popularity in the US of Robinson helicopters for instruction, personal and light commercial use. could it be that the Bell fleet is working 3.5 times harder than the Robinson fleet?
(assuming the same level of incorrectness in the database for both manufacturers) |
This is the search URL I am using for Robinson:
FAA Registry - Aircraft - Make / Model Inquiry That seems OK. But, damn, the initial search I used for Bell was not a good one :( In redoing this I tried to finesse the search, but the FAA website was not helpful. So I searched on each model number separately, added them all up, and got 3554 Bells of all types in the FAA registration database, which equates to a fleet strength of about 25% more than Robinson. I'm sure I missed one here or there, but close enough. So now the bet on total fleet hours is a much more interesting one! I'd happily pay for a beer if someone could trot out the annual hours for each fleet, bet or no bet. |
....breakup in flight with an experienced pilot/instructor at the controls..... |
Originally Posted by gulliBell
(Post 9924733)
I'm not sure how many Bell helicopters breakup in flight with an experienced pilot/instructor at the controls. Probably zero would be my guess. The same can't be said for Robinson helicopters.
https://app.ntsb.gov/pdfgenerator/Re...relim&IType=FA Bell 407 https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA Bell 407 https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA 206L1 https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA Bell 222 https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA 206L1 https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA 214 https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA Bell 222 https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA Bell 212 https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA Bell 212 https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA Bell 407 https://app.ntsb.gov/pdfgenerator/Re...Final&IType=GA Bell 206L1 https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA Bell UH-1B https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA Bell 206B https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA Bell 212 |
The first two have nothing to do with inflight breakup.
The first is a prelim report with no conclusion and indicates loss of control with an unknown cause. The second was poor maintenance resulting in loss of control on landing. Struggling to find the relevance. Stopped reading after that.. |
Originally Posted by Paul Cantrell
(Post 9925186)
https://app.ntsb.gov/pdfgenerator/Re...relim&IType=FA Bell 407
https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA Bell 407 https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA 206L1 https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA Bell 222 https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA 206L1 https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA 214 https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA Bell 222 https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA Bell 212 https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA Bell 212 https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA Bell 407 https://app.ntsb.gov/pdfgenerator/Re...Final&IType=GA Bell 206L1 https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA Bell UH-1B https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA Bell 206B https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA Bell 212 Looking through all these accidents there is almost none initiated by simple handling errors or turbulence or completely unexplicable. Almost in all cases there were either gross maintenance/ overlooked fatigue issues or other external factors (large Bird) preceding the Mast Bumping event. There is almost no straight forward low-g accident in there. Yes there were pilots in Vietnam who managed to do that with the fast and nimble Cobra but with the slower/bulkier Huey even in combat flight they were pretty rare (Tail shot off not counted in this category). All statistics aside that is the really discomforting thing about quite a number of the fatal Robinson accidents (I don't care about those aircraft dinged in training -that is to be expected) that they happened with totally serviceable and often rather new aircraft with often experienced pilots in best flying conditions. |
Originally Posted by Bell_ringer
(Post 9925469)
The first two have nothing to do with inflight breakup.
The first is a prelim report with no conclusion and indicates loss of control with an unknown cause. The second was poor maintenance resulting in loss of control on landing. Struggling to find the relevance. Stopped reading after that..
Originally Posted by gulliBell
(Post 9924733)
I'm not sure how many Bell helicopters breakup in flight with an experienced pilot/instructor at the controls. Probably zero would be my guess. The same can't be said for Robinson helicopters.
The first one indicates what looks like a tail boom chop including strikes from both the main and tail rotor, and which is consistent with the witness' reports of a spinning nose low approach to the ground. Not sure if you disagree with the fact that the tailboom got chopped, or maybe you don't consider that an "inflight breakup". We can ignore that one if you want. The third one says: They subsequently reported seeing components separate from the helicopter before it descended and impacted the ground. The helicopter came to rest in a corn field approximately 1.2 miles from the departure point. A postaccident examination of the helicopter revealed that an 8-foot section of one of the main rotor blades separated in-flight rendering the helicopter uncontrollable. The next one, the Bell 222 actually mentions in-flight breakup: The helicopter was on a postmaintenance flight when it experienced an in-flight breakup about 8 minutes after departure The one after that I think I pasted an incorrect link, but the the 214 accident after that says There was no evidence of abnormal engine operation at the time of the accident or a failure of the tail rotor system or a major airframe structural component before the in-flight breakup. The one after THAT, the 222 quote: The helicopter experienced an in-flight break-up when it was traveling at about 130 knots at 960 feet above the ground. A factor was the manufacturer's dissemination of the pin which did not meet dimensional standards. The one after that, the 212: They then observed the main rotor blades contact the tail area, and the aft tail boom and tail rotor separate. Shortly after this, the main rotor separated and the helicopter descended and crashed to the ground. Another 212: The main rotor mast displayed evidence of a mast bumping event, with indentations corresponding to the blade stops. the in-flight separation of the main rotor mast while in cruise flight following a mast bumping event. The reason for the mast bumping event was not determined. The 206L1 after that was a boom separation due to fatigue cracks in the attachment structure. The next, a UH-1B the probable cause finding: A fatigue fracture in the main rotor mast, which resulted in an in flight separation of the main rotor from the helicopter. THE AIRCRAFT HAD EXPERIENCED AN INFLIGHT SEPARATION OF THE VERTICAL FIN AND SUBSEQUENT MAST BUMPING The last one, a 212 THE INFLIGHT SEPARATION OF THE MAIN ROTOR SYSTEM AS RESULTS OF THE MAIN ROTOR STATIC STOP CONTACTING THE MAST FOR UNDETERMINED REASONS. |
While I agree that four of the citations were probably not applicable, the remaining citations are all the exact sort of thing that would send Robbie haters into paroxysms of Robbie bashing.
Catastrophic, unexplained failures happen to all sorts of helicopters, not just Robinsons, as do catastrophic failures due to design and quality assurance errors on the part of the manufacturer. Hence the old joke: a million parts whirling around an oil leak, waiting for metal fatigue to set in. Some might say all of the citations below are exceptions, not the rule. And Robinson's have a history, of that let there be no doubt. But at the current state of evolution of the designs, and SFAR 73, it would seem that, for the past two years anyway, performance and safety are comparable to other helicopters when operated in a manner consistent with lightweight, low inertia characteristics. At least based on US data. Outside of the US it would seem things are not so rosy. (Disclaimer: said conclusions admittedly based only on number of accidents and number of aircraft operating, no data on total fleet hours available.) https://app.ntsb.gov/pdfgenerator/Re...relim&IType=FA Bell 407 This accident is exactly the type of thing anyone would complain about with a Robinson. A sudden, unexplained, catastrophic failure. https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA 206L1 Blade spar failure and latent manufacturing defects in the blade, again, exactly the sort of thing complained about with Robinsons. https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA Bell 222 Catastrophic failure due to hydrogen embrittlement of an "unknown source". If this happened on a Robinson, there would be endless discussion about the usual suspects: Robinson quality control, etc. https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA 214 Another "mystery failure" of a critical flight control. https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA Bell 222 Poor manufacturing QA on the part of Bell. https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA Bell 212 Mast bumping due to unknown causes. https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA Bell 407 Loss of control for reasons undetermined, with evidence of tail boom blade strikes. https://app.ntsb.gov/pdfgenerator/Re...Final&IType=GA Bell 206L1 Bell's inadequate SB inspection interval with respect to detecting tail boom fatigue cracks. https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA Bell UH-1B Main rotor mast fatigue fracture, well within life limits. https://app.ntsb.gov/pdfgenerator/Re...Final&IType=FA Bell 212 Mast bumping for undetermined reasons. |
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