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recovery from inverted IMC (a propos of "backup gyros" thread)
Because I think this is a story worth hearing, I'm posting
this link here as well as in the original thread, where people who've stopped reading might miss it. http://makeashorterlink.com/?Z27312245 If you don't like makeashorterlink, go to groups.google.com and search rec.aviation.student in 1999 for "all the words" pet grumman This happened in Australia in the mid to late '90s -- '96 to '98, somewhere about there. It was originally posted on the Grumman Gang, and reposted to USENET with the author's written permission. I think it is well worth reading, especially for those who seem to feel the tach and the T/C are superfluous. The bottom line is: there are circumstances one might plausibly encounter where the only reliable instruments in the cockpit may be the tachometer, the turn coordinator, and the pilot's hearing. One might wish to consider this when determining whether to move the tach and TC outside the primary scan. Cheers, Sydney |
#2
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Sydney Hoeltzli wrote:
I think it is well worth reading, especially for those who seem to feel the tach and the T/C are superfluous. I read it. I don't really get anything from it which would apply to the turn coordinator versus AI discussion of late. The author uses some terminology rather loosely - referring to pressure instruments and including in the list (I think?) the DG and AI. It's not clear to me how or why he lost his vacuum driven gyros from the story as posted. I also think he might have derived some erroneous conclusions from his close encounter - for example he referred to engine noise as the 'best guide to inversion.' Sure, engine noise can be helpful for determining whether the airplane is in a dive or climb, but it might be doing either while inverted and the pilot may not know. (What an amazing coincidence that he appeared to have been hit by an R/C airplane - in a cloud! Pretty unbelievable.) Like others in the aforementioned thread, I take attitude information pretty seriously. I fly two vacuum pumps and two AIs. Both AIs are air-driven. My system vulnerability is my plumbing, which I accept as a reasonable risk. My secondary AI lives on the right side of the panel. Now, admittedly I fly my airplane a lot, and from both seats, and practice partial panel fairly regularly. (My idea of fun is plowing around partial panel, OEI, in a single-receiver VOR intersection hold.) As such, I just don't get the hubbub about the location of the damn thing. If it's on the right side of the panel and you need to look to the right to see it, then do so. If you're sitting in the right seat and need to look to the pilot's side of the panel for information, then do that. If one's scan is so weak that one can't handle looking across the panel for attitude indication, one should practice their partial panel skills more often. If one is more susceptible to spatial disorientation from looking at a wider swatch of panel real estate, one needs to fly with an instructor or safety pilot until they're able to handle it. I regard these things as basic requirements to fly instruments. In line with this thinking, my personal feeling is that the location of the indicator may not be the culprit. The problem more likely is the ability to modify one's actions to properly react in an emergency such as vacuum or attitude indicator failure in IMC. (And yes, I will always call that an emergency, regardless of how comfortable one may be flying partial panel.) I think people that lose their cool in recoverable emergencies will tend to break airplanes regardless of how their instrument panel was laid out. One other side note. You mentioned that the tach should be located where it can be part of the primary scan. In the Twin Comanche, almost all of the ships flying have MAP and RPM on the copilot side of the panel. That area of the panel simply has to be part of your scan if you wish to include those instruments. Personally, I think this is a good thing, because it tends to force the pilot to use the whole panel rather than fixating on the six-pack. Best, Ryan CFI-ASE-AME, CFI-RH, CP-ASMEL-IA, CP-RH, AGI |
#3
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Ryan Ferguson wrote:
Sydney Hoeltzli wrote: I think it is well worth reading, especially for those who seem to feel the tach and the T/C are superfluous. I read it. I don't really get anything from it which would apply to the turn coordinator versus AI discussion of late. Oh, well. The author uses some terminology rather loosely - referring to pressure instruments and including in the list (I think?) the DG and AI. No, I don't think so. He states seperately that his vacuum instruments tumbled, and gives the reason. Then he assumes the reader remembers this, later on. It's not clear to me how or why he lost his vacuum driven gyros from the story as posted. Really? It's clear to me. He was flipped inverted, and his gyros tumbled. Are you sure you read it? I also think he might have derived some erroneous conclusions from his close encounter - for example he referred to engine noise as the 'best guide to inversion.' Sure, engine noise can be helpful for determining whether the airplane is in a dive or climb, but it might be doing either while inverted and the pilot may not know. I think you missed the point, which is to correlate engine noise with yoke movement. If you pull back the yoke to climb, but engine noise increases, what does that tell you? If you push forward on the yoke but engine noise decreases, what does that tell you? (recall we're talking fixed pitch prop here) If your gyros tumbled because you flipped inverted and your pressure instruments were temporarily unreliable because of massive pressure changes, what would you suggest as the "best guide" to determining if you're inverted? Like others in the aforementioned thread, I take attitude information pretty seriously. I fly two vacuum pumps and two AIs. Both AIs are air-driven. My system vulnerability is my plumbing, which I accept as a reasonable risk. Have you tried what Big John suggested, taking the AIs loose from the panel and seeing if/when they tumble, and when (after how much banking and diving) they develop sufficient error to be problematic as guides? If one is more susceptible to spatial disorientation from looking at a wider swatch of panel real estate, one needs to fly with an instructor or safety pilot until they're able to handle it. I regard these things as basic requirements to fly instruments. Hmmmm...if the issue of having to turn one's head frequently is just a proficiency thing, Ryan, and any pilot ought to be able to handle it if he flies with a safety pilot enough -- why do some experienced pilots stress that the scan should involve just moving the eyes, not the head? Why do physiologists stress that rapid head movements are a good way to induce spatial disorientation? In line with this thinking, my personal feeling is that the location of the indicator may not be the culprit. The problem more likely is the ability to modify one's actions to properly react in an emergency such as vacuum or attitude indicator failure in IMC. (And yes, I will always call that an emergency, regardless of how comfortable one may be flying partial panel.) Can't argue here. Anything which bites so many pilots who "ought to be able to handle it" for reasons which are unclear at present, deserves to be handled like a live viper IMHO. Carefully, and with all available precautions. I think people that lose their cool in recoverable emergencies will tend to break airplanes regardless of how their instrument panel was laid out. Can't argue with that, either. OTOH, I do think that it's too simple to dismiss some of the problems supposedly good, experienced pilots have as entirely due to lack of proficiency, unless one has solid evidence that this is the case. One other side note. You mentioned that the tach should be located where it can be part of the primary scan. Um, not exactly. I say one should consider this experience when deciding whether one wishes to relocate the tach outside one's primary scan. In the Twin Comanche, almost all of the ships flying have MAP and RPM on the copilot side of the panel. If you'll pardon my pointing this out, I do think a plane with an adjustable pitch prop has different issues for power management. I notice this when I let pilots who are used to same take the controls of my plane. Cheers, Sydney |
#4
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On Tue, 15 Jul 2003 03:41:55 GMT, Sydney Hoeltzli wrote:
I think you missed the point, which is to correlate engine noise with yoke movement. If you pull back the yoke to climb, but engine noise increases, what does that tell you? If you push forward on the yoke but engine noise decreases, what does that tell you? (recall we're talking fixed pitch prop here) If you have long enough to do that test whilst inverted in an AA5, within a couple of seconds, you'll be greeted by silence. I don't know about the AA5, but the C140 would quit if you did a zero-g pushover slightly too vigorously! -- Dylan Smith, Castletown, Isle of Man Flying: http://www.dylansmith.net Frontier Elite Universe: http://www.alioth.net "Maintain thine airspeed, lest the ground come up and smite thee" |
#5
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Sydney Hoeltzli wrote:
No, I don't think so. He states seperately that his vacuum instruments tumbled, and gives the reason. Then he assumes the reader remembers this, later on. I'm afraid not! The word 'tumble' does not even appear in this story. But anyway, perhaps you read another account where the author was more specific. Really? It's clear to me. He was flipped inverted, and his gyros tumbled. Are you sure you read it? I'm sure. He says he 'flipped' (I guess he must mean 'rolled') and that 'just about every instrument [was] gone for the time being." That's it. Maybe you read another account with more detail. I do not make any assumption about why or when his gyros tumbled, or even that they tumbled. Guess I've become careful after reading accident synopses. Additionally, I've rolled airplanes with gyros - in my experience the gyros tumble, re-erect, and that's that. So there's definitely a lot missing from the story that the reader has to fill in for himself with guesses. I think you missed the point, which is to correlate engine noise with yoke movement. If you pull back the yoke to climb, but engine noise increases, what does that tell you? If you push forward on the yoke but engine noise decreases, what does that tell you? (recall we're talking fixed pitch prop here) Actually, I think I got it. Start the plane in level inverted flight, try your yoke exercise and see what it tells you. I'm not saying it can't be used when you know you're not inverted, but if the airplane's attitude is a true unknown to the pilot, such a method can only be used in the correlative sense. If your gyros tumbled because you flipped inverted and your pressure instruments were temporarily unreliable because of massive pressure changes, what would you suggest as the "best guide" to determining if you're inverted? Hmm. Maybe this is another area where we're not thinking about the same thing. Exactly where in this story does the author suffer a 'massive pressure change'? What caused the pressure instruments to 'become unusable?' There've been studies conducted in which the pilot, given instrument failures in a controlled environment (or simulator) thought that other instruments had failed and didn't believe the associated indications of the instruments that actually worked. Could it be possible that this is the case here? Again, why would the pressure instruments become unusable? Have you tried what Big John suggested, taking the AIs loose from the panel and seeing if/when they tumble, and when (after how much banking and diving) they develop sufficient error to be problematic as guides? Heck no. I pamper the gyros. Have replaced one already, don't want to replace any more any time soon! Hmmmm...if the issue of having to turn one's head frequently is just a proficiency thing, Ryan, and any pilot ought to be able to handle it if he flies with a safety pilot enough -- why do some experienced pilots stress that the scan should involve just moving the eyes, not the head? For those who more easily become disoriented, keeping the head 'still' does help. When you graduate to a twin with a panel full of instruments left to right, or a business jet... you simply have to be able to do it. Of course by the time many pilots fly jets their scan is quite good anyway. Why do physiologists stress that rapid head movements are a good way to induce spatial disorientation? There's a difference between breakdancing in the cockpit and making a full scan of all the instruments, Sydney. You do what you have to do. -Ryan CFI/MEI/CFI-H (testing new signature) |
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