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#91
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[name removed, since this isn't personal] writes:
Without knowing for sure, one of the possible factos for the Kennedy accident [...] I think that we need to create a new variation of Godwin's Law, for aviation groups and lists, named in honour of John F. Kennedy Jr.: John Jr's Law ------------- As an aviation-related discussion grows longer, the probability of a cautionary reference to John F. Kennedy Jr.'s fatal crash off Martha's Vinyard on July 16, 1999 approaches one. All the best, David |
#92
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Roy,
Oops! I remembered wrongly. Sorry! -- Thomas Borchert (EDDH) |
#93
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"David Megginson" wrote in message ... John Jr's Law Gee, my corollary was "When someone famous crashes and non-aviation oriented people find out that you are a pilot, they're going to ask you about it." I flew up to my family reunion in Mass. a few weeks after the JFKJr crash. I got asked that every time I turned around. |
#94
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Dan Truesdell wrote: the few short forays into the clouds lead me to investigate an electric AI. Although we were only in the bumpy stuff for a few minutes at a time, Now that the FAA has finally relented and allowed you to throw away your turn coordinator and get a second AI I went and talked to my local avionics shop about the RC Allen electric AI that I see advertised for about $1800. They said don't bother as 90% of them come back because they are so horribly built. They told me to get the reliability of a vacuum AI it's gonna take about $4000. |
#95
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Thanks for the heads-up on those. I was figuring on about $2K, but $4K
would mean asking the other 4 owners to kick in $1000 for an item that they won't use. For a 172, it's probably just as good then to get a manifold-driven backup vacuum. Too bad the electronic AI's are not certified for IFR (the $1500 ones, not the $6000 ones.) Newps wrote: Dan Truesdell wrote: the few short forays into the clouds lead me to investigate an electric AI. Although we were only in the bumpy stuff for a few minutes at a time, Now that the FAA has finally relented and allowed you to throw away your turn coordinator and get a second AI I went and talked to my local avionics shop about the RC Allen electric AI that I see advertised for about $1800. They said don't bother as 90% of them come back because they are so horribly built. They told me to get the reliability of a vacuum AI it's gonna take about $4000. -- Remove "2PLANES" to reply. |
#96
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Dan Truesdell wrote:
Thanks for the heads-up on those. I was figuring on about $2K, but $4K would mean asking the other 4 owners to kick in $1000 for an item that they won't use. For a 172, it's probably just as good then to get a manifold-driven backup vacuum. Consider the dual-rotor vacuum pump from http://www.aeroadvantage.com instead. I've owned one of the manifold-driven backup vacuum systems, and it's marginally OK, but I wouldn't buy one again. The shuttle valve gets stuck. It requires pilot action to preflight test it, and to switch it on when you need it. The vacuum it provides is limited. There is no provision for practicing with it (you have to physically disconnect the vacuum pump), so you don't get proficient with flying with the reduced vacuum and altered operational requirements. Under most operational regimes, you will have to limit engine power in order to keep the vacuum sucking. By contrast, the dual-rotor pump failover is automatic, you get full vacuum without interruption, just a panel annunciator to check during preflight and to tell you one of the rotors has failed. The cost is only slightly more than the manifold-dirven system. Dave Remove SHIRT to reply directly. |
#97
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Dan Truesdell wrote:
Thanks for the heads-up on those. I was figuring on about $2K, but $4K would mean asking the other 4 owners to kick in $1000 for an item that they won't use. For a 172, it's probably just as good then to get a manifold-driven backup vacuum. Too bad the electronic AI's are not certified for IFR (the $1500 ones, not the $6000 ones.) One of our club airplanes has something like this. But someone told me that it works least well under full throttle...which means down low executing a missed approach. Was I told correctly? How serious is "least well"? - Andrew |
#98
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Roy Smith wrote in message ...
A friend of mine and me tried an experiement once. I put our Archer into some unusual attitudes, and he recovered using just the synthetic instruments on his handheld GPS (Garmin something-or-other, might have been the 295 but I'm not sure). Conditions were night VFR, no turbulence. I haven't tried this yet, and I really should. What I can say is that IME it's significantly easier to fly a full approach partial panel at night with either my panel moving map, or my handheld moving map, than it is with both failed, and that this is not because it's easier to navigate per se, but because it's easier to *keep the wings perfectly level* in TB or chop by using the track info on either GPS to hold a steady track. (Basically, I would hold that navigation at its most fundamental is simply the ability to hold heading, and that the ability to hold heading at its most fundamental is simply the ability to keep the wings level). Our CFI has absolutely no regard for the FAA's views on which instruments to fail or how many *g* and we did this very deliberatly as an emergency exercise, in order to learn exactly how much info we extract from the moving maps and the best setup to extract it from our particular equipment. If he ignored pitch (let the trim take care of it) and just used rudder to zero out rate of turn on the synthetic TC, he did pretty well. I don't have a "synthetic TC", but it sounds analogous to what I learned to do in the way of zeroing the change on the track. I'll have to see about trying it with unusual attitudes. Best, Sydney |
#99
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Andrew Gideon wrote:
Dan Truesdell wrote: For a 172, it's probably just as good then to get a manifold-driven backup vacuum. Too bad the electronic AI's are not certified for IFR (the $1500 ones, not the $6000 ones.) One of our club airplanes has something like this. But someone told me that it works least well under full throttle...which means down low executing a missed approach. Was I told correctly? How serious is "least well"? That's exactly right. (From memory) the STC recommends you maintain at least 3.5 inches of vacuum to the gyros. That means the intake manifold pressure has to be at least 3.5 inches less than the ambient pressure. At sea level on a standard day, you will have to adjust your power to have a manifold pressure no higher than (29.92 - 3.5) = 26.42 in Hg. If you have a fixed prop and no manifold pressure gauge, you have to figure out what that means for a throttle setting. There will be a calibration placard giving maximum RPM for different pressure altitudes. At high pressure-altitudes (low ambient pressure), you will need to reduce power correspondingly to maintain the required vacuum to keep the gyros spinning. Specifically, during a missed approach, you'll have to choose between keeping the gyros spinning and having full power available. My limited experience is that 3.5 inches is not enough for good reliable instrument indications. That may be a function of which models of instruments you have installed and how new the bearings are. Of course, as I pointed out elsewhere in this thread, you don't get to practice managing the vacuum under realistic conditions. Pulling out the knob on the panel doesn't activate the system if you have a working vacuum pump. There is a shuttle valve that selects the vacuum source that provides the most suck (manifold or pump) when the panel control is activated. Said shuttle valve is also a point of failure. You can check it on the ground with the engine idling. At idle, the manifold will pull more vacuum than the pump. I can count on the fingers of *no* hands the number of pilots I have ever seen perform this check routinely. At risk of beating a dead horse, get the dual-rotor pump from http://www.aeroadvantage.com instead. |
#100
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Seriously close to "not at all".
Your instruments want to see vacuum of about five inches Hg to operate. I'm guessing they'll still function OK down to four inches Hg. That means your manifold pressure would need to stay at least 4 inches below ambient atmospheric pressure to keep your gyros up to speed. That sacrifices a lot of climb power, for sure. ---JRC--- "Andrew Gideon" wrote in message = online.com... =20 One of our club airplanes has something like this. But someone told = me that=20 it works least well under full throttle...which means down low = executing a=20 missed approach. =20 Was I told correctly? How serious is "least well"? =20 - Andrew |
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