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#61
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#63
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#64
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Mike
As they say, "Train for the worst. Hope for the best". Big John On Wed, 26 Nov 2003 02:38:51 GMT, "Mike Rapoport" wrote: I have also had a gyro fail (in a Turbo Lance that had only one AI) in IMC flight along with an partial electrical failure (lost the alternator) and managed to get to my destination after shooting a localizer approach to pretty much minimiums with a Garmin 12XL that I had to program the approach waypoints into while flying partial panel AND it was in freezing rain. No ****, this really happened. Every emergency I have ever had was on that one flight which happened to be my first serious IFR flight after getting the IR (accross the Sierra From Minden to San Jose in a major blizzard) That experience doesn't convince me that there are not plenty of senarios where it wouldn't have had a happy ending. Mike MU-2 "Michael" wrote in message . com... "Mike Rapoport" wrote True but I would assume that they thought that they had given the subject adequate consideration. It is arogant to believe that everyone else is a fool and you are not. My fovorite ezample are those pilots who are confident that they could handle an IMC gyro failure when the record shows that many (most?) cannot. Yeah, I've heard that song before. Even believed it. Then I had my AI tumble. At night. In IMC. On the climbout. While being rerouted. In spite of what everyone told me, it was a complete non-event. Used the copilot side AI for a while, but quickly decided it was too much hassle, and flying partial panel was easier. Since I still had the copilot side AI, I was legal to continue the flight - and I did. Shot the NDB at my destination, but the weather was crap and the runway lights were inop, so I couldn't get in. Wound up shooting the ILS to near mins in the rain at my alternate. No big deal. Gyro failure is not a big deal if you train properly. I could even argue that without the backup AI, I would have been safer that night because I would have had to turn back and land. On the other hand, an engine failure in a single engine airplane under the same conditions would have been very, very ugly. Michael |
#65
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750 hrs here (OK, 250 of them in gliders). One impending failure due
to broken shaft seal on the crankcase. The engine did not show oil pressure any more, but I made it back to the airport with the engine still running at near idle. It happened on the climbout, about 3000 AGL. Tobias |
#66
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Rich
Some other data to put in the pot. The Air Force paid some one (Rand Corporation or some other think tank) to do a study on accidents vs flying time. It basically came out that there were two spikes, one around 500 hours and the other around 1000 hours. The 500 hour accidents were attributed to cocky over confidence. Not sure right now what the 1000 spike was but it was caused by something we could train around or change procedures, etc. to reduce as I recall. Big John On 25 Nov 2003 07:57:26 -0800, (Rich Stowell) wrote: Sorry I can't point you to the "harder" data you're looking for, but here's perhaps a little perspective on the issue: According to one NTSB Study, pilots with fewer than either 500 hours total time, or 100 hours in type, are more likely to encounter an inadvertent stall/spin than to have a genuine engine failure (i.e.: a random-event engine failure, not one attributed to such pilot errors as fuel mismanagement). In my case, over 6,400 hours with 5,600+ hours of instruction given (mostly doing spin, emergency maneuver, aerobatic, and tailwheel training -- the type of flying that might be considered harder on an engine than more routine types of flying), I've had several non-critical engine anomalies that were successfully dealt with, including: Prop stoppages during spins due to a couple of students hanging on so tight to the throttle that it choked off the engine -- we call that "fright idle"; Clogged fuel injectors during take-off that only revealed themselves at full throttle; Primer controls that were not truly "in and locked" which has lead to prop stoppages during idle power landings. In addition, two legitimate engine failures as follows: The first, a fuel injector failure as we entered the traffic pattern (after practicing off field landings, no less!) -- landed without further incident; The second, carb ice in a Champ during a flight review choked off the engine during a touch and go -- touched down on the taxiway abeam the departure end of the runway, hit a parked Porshe, bent the airplane, walked away without so much as a scratch. Rich http://www.richstowell.com (Captain Wubba) wrote in message . com... Indeed. Interesting. But I'd still like to see some hard data. This is the kind of problem I run into...most of your pilot friends report that they have had a failure, but the majority of mine report none. And none of the 2000+ hour CFI types I asked (I asked 4 of them) have ever experienced an engine failure. My dad was a pilot with well over 12,000 hours and never had one. Another relative had fewer than 500 hours total in his flying carrer and lost one on his first solo XC. I asked another A&P I ran into at the airport tonight, and he said he thought it should be at least 40,000 hours per in-flight engine failure, but really wasn't sure. Since a big part of flying is risk management, it would be very helpful to *really* know the risks involved. If the odds of losing an engine are 1 in 50,000 hours, then night/hard-IFR single-engine flying becomes a great deal more appealing than if it is 1 in 10,000 hours. I'll try to go over the NTSB data more thoroughly, I think a reasonable extrapolation would be that at least 1 in 4 in-flight engine failures (probably more) would end up in the NTSB database. But the cursory review I made earlier made me think the numbers were much less negative than I had considered before. And the opinions of these A&Ps are very interesting, because while failure might not require a total overhaul, it will require *something* to be done by a mechanic...and if these guys are seeing 30-40 engines make it to TBO for every one needing repair due to an in-flight failure, that might well support the 40,000 to 50,000 hour hypothesis. Cheers, Cap (Michael) wrote in message om... (Captain Wubba) wrote Howdy. I was discussing with a friend of mine my concerns about flying single-engine planes at night or in hard IFR, due to the possibility of engine failure. My buddy is a CFI/CFII/ATP as well as an A&P, about 3500 hours, and been around airplanes for a long time, so I tend to give credence to his experiences. He asked me how often I thought a piston engine had an in-flight engine failure. I guestimated once every 10,000 hours or so. He said that was *dramatically* over-estimating the failure rate. He said that in his experience it is at least 40,000 to 50,000 hours per in-flight engine failure. The only vaguely official number that I've ever seen came from a UK accident report for a US-built twin. The UK investigators queried the FAA on engine failure rates for the relevant engine, and the only answer they got was that piston engines have failure rates on the order of 1 in 1000 to 1 in 10000 hours. This is consistent with my experience. I've had one non-fuel-related engine failure (partial, but engine could only produce 20-30% power) in 1600+ hrs. Most people I know with over 1500 GA hours have had an engine failure. 50,000 hours is not realistic. Excluding a few airline pilots (who have ALL had engine failures) all my pilot friends together don't have 50,000 hours, and quite a few of them have had engine failures. I've heard the maintenance shop thing before, but you need to realize that most engine failures do not result in a major overhaul. Stuck valves and cracked jugs mean that only a single jug is replaced; failure of the carb or fuel injection system (my problem) affects only that component. And oil loss will often seize an engine and make it not worth overhauling. There are no real stats on engine failures because engine manufacturers and the FAA don't want those stats to exist. The FAA could create those stats simply by requiring pilots to report engine failures for other than fuel exhaustion/contamination reasons, but will not. The truth is, FAA certification requirements have frozen aircraft piston engines in the past, and now they're less reliable than automotive engines (not to mention ridiculously expensive). Michael |
#67
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(Michael) wrote in message . com...
(Rich Stowell) wrote Sorry I can't point you to the "harder" data you're looking for, but here's perhaps a little perspective on the issue: According to one NTSB Study, pilots with fewer than either 500 hours total time, or 100 hours in type, are more likely to encounter an inadvertent stall/spin than to have a genuine engine failure (i.e.: a random-event engine failure, not one attributed to such pilot errors as fuel mismanagement). Really? If that were true, then there would be hard data. Yes, really -- see "A Study of Light Plane Stall Avoidance and Suppression." By D.R. Ellis, Report No. FAA-RD-77-25, 1977, p. 6. As for the "hard data" behind this finding, that's for you to follow up on since this is your research project What the NTSB study REALLY says is that these low time pilots are more likely to encounter an inadvertent stall/spin LEADING TO AN ACCIDENT than to have a genuine engine failure LEADING TO AN ACCIDENT. True, but that's stating the obvious since NTSB only gets involved in, and thus only reports on, those encounters that have led to actual accidents. This is because an engine failure rarely leads to an accident (at least if the ones known to me are any indication) but an inadvertent stall/spin usually leads to an accident. Define "rarely." From an industrial accident prevention standpoint, the theoretical ratio 1:30:300 is often applied wherein for every 331 hazardous encounters of a similar type, only one will progress as far as an actual accident (significant damage and/or injury). The rest fall under "incidents" and "hazards." In other words, typically 1 out of 331 encounters of a similar type results in an accident, whether it's precipitated by an engine failure or an inadvertent stall/spin. In the case of NTSB data, one could extrapolate to get a feel for the order of magnitude of problems pilots deal with in a particular category by multiplying the number of accidents by 331. While it is true that one accident classification may be more prevalent than another (e.g.: more stall/spin fatalities than ground loop fatalities), the ratio of accidents-to-total encounters may very well be equal. In that case, 1 out of 331 would be the same for engine failures leading to accidents as for stall/spins leading to accidents, or any other accident type. I guess one could argue that 1 accident out of every 331 hazardous encounters is "rare" regardless of the cause. In that context, one could then argue that compared to the total number of stall/spin encounters, stall/spin accidents are equally as "rare" as engine failure accidents. For that matter, most engine failure fatalities in light singles are not the result of collision with terrain (which is usually survivable) but of failure to maintain flying speed (which usually isn't). That's basically a stall/spin anyway. Two things: First, approximately 19 percent of stall/spin accidents are preceded by an engine failure. But the primary accident cause is still listed as "stall/spin." See "General Aviation Pilot Stall Awareness Training Study," by William C. Hoffman and Walter M. Hollister, Report No. FAA-RD-77-26, 1976, p. 6. Second, the contention that "failure to maintain flying speed" is "basically a stall/spin anyway" is pure myth. Spins are the result of two ingredients that must coexist: yaw and stall. And neither yaw nor stall is a function of airspeed. Up to the point where the wings decide to bend or break, stalls and spins can and do occur at any airspeed, and in any attitude. For example, stall while at 1-g and Vso and give it some yaw = spin; stall at 1.95 times Vso with +3.8-g's (that's the same as saying "Va and the design limit in the Normal Category") and give it some yaw = spin; give any airplane the right amount of g's at a given airspeed and give it some yaw = spin. In my experience, and based on the research I've read, I'd postulate that the majority of stall/spin accidents occur with the airplane operating somewhere between 1.07 to 1.20 times Vso and 1.15 to 1.41-g. In other words, with pilots pulling into an uncoordinated, accelerated stall while turning at bank angles between 30 and 45 degrees. Rich http://www.richstowell.com |
#68
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#69
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"Kyler Laird" wrote in message
... Don't forget that you're safest with a single-cylinder engine. If you have a six-cylinder, you're *six* times as likely to have a failure. If the only thing that could go wrong with an engine was some sort of failure of the cylinder, then that would actually be a pretty close approximation of the truth. And in fact, if you have a six-cylinder engine, you ARE (about) six times as likely to have a failure *of a cylinder* as you would with a single-cylinder engine. In the single vs. twin analysis, you have nearly double the chance of an engine failure as with a single, all else being equal. If X (a number between 0 and 1) is the chance of an engine failure for a single engine, it's not that you have 2 * X chance of an engine failure for two engines. You actually have 1 - ((1-X) * (1-X)) chance of an engine failure. But when X is small (as it is in this case), the square of 1-X is pretty close to 1 - (2 * X). If all that could fail on an engine was a cylinder, or component related to a cylinder, then a six-cylinder engine would be 1 - ((1-X) ^ 6) likely to fail, where X is the chance of failure for a single-cylinder engine. But just as 1 - ((1-X) ^ 2) is very close to 2 * X for small X, so too 1 - ((1-X) ^ 6) *is* actually very close to 6 * X for small X. Now, with that essay out of the way, the real reason that six cylinder engines aren't six times as likely to fail is that a number of failure modes have nothing to do with the cylinder. They involve one or more other parts, parts which exist in the same number regardless of the number of cylinders. Note also that just as having two engines provides a benefit to offset the very real increased opportunity for failure, having four, six, or more cylinders provides a benefit to offset the very real increased opportunity for *cylinder failure*. That is, with a six cylinder engine, if something that IS specific to a cylinder fails, often the result is simply reduced power, not a complete power failure. ...or at least that's what I've learned from some of the geniuses who talk about twins vs. singles. Sounds like you've got some good geniuses advising you. Stick with them. Pete |
#70
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"Mike Rapoport" writes:
Knowing *NOTHING* about turbocharged engines, I was wondering. Would a loss of the turbocharger still allow the engine to produce the same power as a non-turbo engine of the same size at the same altitude? From the It depends on the type of turbo failure. The typical failure is the bearing in which case the engine will not make much, if any power. It apparently depends on the system too. For my plane, it's recommended to shut off the turbos for takeoff below 1000'. I've also flown quite a few hours with blown turbo bearings, so I think it's safe to say it does not cause a huge decrease in power. --kyler |
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