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You are in IMC, when *everything* fails! Now what?
Hello All,
There has been much discussion here about the obvious benefits of redundant systems, engines, vacuum, electrical etc., when flying in IMC. We've also read NTSB reports of crashes of very well equipped planes where the pilot did not make use of redundant instruments. As for myself and perhaps others, I will most likely never have access to any aircraft with system redundancy beyond the simple electric TC/vacuum gyro combo. I fly singles such as the 172 and 182, all usually at least 25 years old. I did however, obtain my ratings for the purpose of going places and doing things, and I seem to be flying about 5% of my hours in actual IMC. Being a person that places a high value on my own ass, and the asses of the people who fly with me, like others here I carry some backup equipment. A Magellan 315 I have flown 24,000 miles with so far, a JHP-520 portable com, Palm VII/CBAV for weather, and spare batteries for all. For now I fly well maintained rentals. So far in my meager 400 hours I have experienced a total electrical failure, an AI failure, and a few VOR and ILS problems. All these were easy to work around. I'm satisfied that with a vacuum failure I can fly just fine on the TC, and vice versa. How about when you lose your vacuum instruments *and* your electrical system? No nav, no com, no gyros at all, just your engine and pito-static instruments. The essence of maintaining control in IMC is being able to determine if you are turning. I've long figured that even with a 1 second position update rate, the simplest GPS should give you enough turn data to stay in control in addition to guiding you to an airport and making a useable approach. I and iron-gut acro/safety pilot Doug found out yesterday. Conditions: Clear, 92 degrees, fairly rough thermal TB about 2000 agl. For warmup, we did 2 full hours of currency approaches and holds, building a "pyramid" of stress and fatigue. The task: "Fail" all gyros, AI, TC, DG, and all nav equipment. Trying this for the first time ever, now navigate 25nm to an airport and make a successful non-precision approach using only the handheld GPS, the "ball", and pito-static instruments. My strategy is to make good use of the inherent stability of the 172, keeping my hands off the yoke as much as possible and turning with the rudders. To keep things simple, I plan only 2 turns. The GPS is simply set for a "go-to" to our airport. Our destination was to the northwest, so fly due west a while, then 45 to the right to intercept a long final approach course. The GPS display mode was a simple numbers-only bearing/heading/distance/speed. Right off the bat it was very strange and we thought our test might be over in about 1 minute. The GPS, though updating every second, is still giving you "old" information. Now using the rudder to turn, the airplane takes a while to respond. With the constant upsetting influence of the thermals, the plane is always wanting to turn. You see it on the GPS, and by the time you get some rudder pressure on, you are maybe 10 to the right. Now you hold the rudder and wait for the plane to respond, and slowly you come back on course, but overshoot. I try to adjust my inputs to smooth things out but the TB makes it pointless. I resign myself to the fact that at best we will make constant small s-turns all the way. Every now and then a good thermal jolts us into a significant bank. My instinct was to get the ball centered, check our pitch with the airspeed etc, then check the GPS to see which way we were now going and slowly urge us back. Seems to work. Soon I realize we've gone several miles already, and all this actually seems to be working! Patience seems to be the rule- put a small amount of pressure on the rudder, hold and wait for results. Soon we are intercepting our 8 mile final approach course, using a published NDB approach as a template, and doing our altitude stepdowns based on GPS distance to the field. Closer to the ground thermal induced turns made it difficult to get down to MDA as soon as I would have liked, but we did arrive at MDA right over the field and a circle to land could have been easily done. In spite of the constant s-turning, we maintained our final approach course within +- 3 degrees, better than I could have done with the ADF and the full panel! We finish up with a partial panel ILS into our home field, and hot and tired, I manage an embarrasing multi-bounce landing. The conclusion of course, is that a battery powered GPS is an absolutely essential piece of backup equipment that can save you even with major system failures. We did a worse case scenario, but for example, you could use the GPS to simply hold a course to VFR conditions. At higher altitude you would have a smoother ride needing only occasional control input. We must, in an emergency, actually remember to use the backup info available whether from a portable device or a panel instrument. Anyone else tried this type of emergency procedure? Thoughts? Tips? Tom Pappano, PP-ASEL-IA ps: Howard Stark's 1-2-3 Method of Blind Flying was Needle-Ball-Airspeed. This could be the 4-5-6 method: GPS-Ball-Airspeed |
#2
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Thomas Pappano wrote:
Anyone else tried this type of emergency procedure? Thoughts? Tips? My only suggestion would be to try this at night under the hood. I am not convinced that you can adequately simulate IMC in daytime VMC conditions. I find it *much* easier to keep wings level under a hood (or foggles) in daytime VMC than in actual. So if you can pull this off at night under a hood, I'd believe this would work for you. Also, if this is to work, you would need to have the GPS powered up and running at the moment of the failure. It's not like you'd be able to hold wings level while taking three minutes for the GPS to power up and acquire satellites.... -- David Rind |
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David Rind writes:
Also, if this is to work, you would need to have the GPS powered up and running at the moment of the failure. It's not like you'd be able to hold wings level while taking three minutes for the GPS to power up and acquire satellites.... Another option would be the old whiskey compass, as long as you can get to an east or west heading. All the best, David -- David Megginson, , http://www.megginson.com/ |
#4
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"Thomas Pappano" wrote in message
. .. I've long figured that even with a 1 second position update rate, the simplest GPS should give you enough turn data to stay in control in addition to guiding you to an airport and making a useable approach. I and iron-gut acro/safety pilot Doug found out yesterday. I've often wondered if a pendulum, in lieu of a GPS or compass, would provide sufficient yaw information to keep the wings. But I've never tried the experiment. --Gary |
#5
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"Gary L. Drescher" wrote in message
. net... provide sufficient yaw information to keep the wings. Er, meant to say "to keep the wings level". Though I guess it sort of made sense the way I typed it, too. |
#6
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"Gary L. Drescher"wrote
Er, meant to say "to keep the wings level". Though I guess it sort of made sense the way I typed it, too. Great idea Gary! You just may have saved me a lot of money on that new gyro based Attitude Indicator that I need. Bob Moore |
#7
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My advise, Definately find out where VFR conditions exist in relationship
to your route PRIOR to taking off and highlighting the area on the LE chart. At least you'll which way to turn. I put together a backup electrical system. Small 12 volt battery..16.00 Small padded bag.........3.00 Lighter jack parts, female, male, fuses etc... I can power up a hand held GPS, handheld radio etc... You still have to fly the plane first, but you can talk, ya know where you are, and you can get the hell out of the situation. The battery will power both for hours. I have a male to male that could backfeed power to the xponder is some AC to at least squawk the 7600,7700 or what ever the case may be. Chris Grotewohl -- http://irish5string.homestead.com/chrisG.html http://home.kc.rr.com/grotewohl/CFI.html |
#8
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"chris grotewohl" wrote in message ... My advise, Definately find out where VFR conditions exist in relationship to your route PRIOR to taking off and highlighting the area on the LE chart. At least you'll which way to turn. I put together a backup electrical system. Small 12 volt battery..16.00 Small padded bag.........3.00 Lighter jack parts, female, male, fuses etc... I can power up a hand held GPS, handheld radio etc... You still have to fly the plane first, but you can talk, ya know where you are, and you can get the hell out of the situation. The battery will power both for hours. I have a male to male that could backfeed power to the xponder is some AC to at least squawk the 7600,7700 or what ever the case may be. Chris Grotewohl -- http://irish5string.homestead.com/chrisG.html http://home.kc.rr.com/grotewohl/CFI.html Hi Chris, This is something I have planned, have not yet tested, but should work great. Carry a small gel-cell equipped with a fuse and male lighter plug. When electrical is lost, turn off master switch, turn off non-critical equipment, lights, etc. Plug in the battery, which will then backfeed the bus. This should power the electric TC, radios, and transponder long enough to get down with a more or less "normal" instrument approach. A pair of 7 amp/hr 12 volt gel-cells total about 10 lbs & $40. Tom Pappano, PP-ASEL-IA |
#9
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"Gary L. Drescher" writes:
I've often wondered if a pendulum, in lieu of a GPS or compass, would provide sufficient yaw information to keep the wings. But I've never tried the experiment. Here's an easier experiment: take a carpenter's level and duct-tape it to your bicycle's handlebars. Now, go around a few turns fairly fast (i.e. the bicycle is at a good bank). Does the level show that the handlebars are tilted during the turn, or is the bubble still in the centre? The answer will help show why you need gyroscopic instruments (or newer expensive equivalents) to fly in IMC. All the best, David -- David Megginson, , http://www.megginson.com/ |
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