Inflight Entertainment => There I was... => Topic started by: Plthijnx on January 17, 2006, 06:46:53 PM
Title: WX and decision making
Post by: Plthijnx on January 17, 2006, 06:46:53 PM
I was called out yesterday to do some more relay work for an offshore helicopter company and with an approaching cold front due in that night around 9ish i was a little concerned but not really. mistake #1. around 5:30 i was released to fly back home, i had been stationed over the white lake VOR just southwest of laffayette louisiana and am based at la porte (east side of houston on the west bank of the bay). when i was about 40-50 miles east of beaumont the ceiling started coming down and the sun was setting so the visibility was deteriorating albeit still VFR. for those of you without an instrument rating, take what i'm fixing to say to heart. get one. i had my girlfriend with me and had been talking to her. well when i looked out the windscreen, what did i see?? nothing. i had flown into the clouds. no problem. immediately i called beaumont approach and told them my situation and got on a plan. my nav/coms were not very spiffy so i requested radar vectors through his airspace then on to la porte which he had no problem with. upon leaving his airspace to the west i cancelled the flight plan b/c i was VFR again. no problem i thought. we've got 25-30 miles to go and everything will be cool. uhh, nope. we get to the west side of the bay and i see a familiar ship yard on the left but no bridge on the right. the bridge i was looking for has high intensity lights on the top but to no avail. just inland there is a wall of clouds and rain from the surface up. i skirt around and decend to 500 over the water flying the shoreline to see if i could get in on a VOR approach but decided that since my com 2 was not up to par elected to go to another airport, baytown. with baytown in sight i get set up for landing. then on downwind, 1000agl the front hit and wham! once again i'm in the soup, low and slow. in your vfr training you practice hood work for a reason but in reality, an instrument rating will fair you much better in this situation. so anyway, i go throttle full and execute a climbing left turn to 180 degrees of course, (which actually happened to be heading 180). we broke out and when we did i turned and looked for the airport. it was totally obscured. the execution of the manuever took less time to do than to sit here and type this out. it was a fast moving front. now enter girlfriend and the infamous words "i'm going to be sick" she grabbed a bag from a burger joint we'd hit earlier and let it loose. Murphey's Law states here that there will be a hole in the bag so the floorboard of the warrior was painted some. we ended up flying back across the bay to an airport that i knew would be well clear of the front, landed and called my boss to come get us. about 10 minutes later the front hit the airport with wind so strong the rain was going sideways and shaking the building that we were in. weather, especially fronts are nothing to toy around with. if your not trained or not up to your own personal standards the results can be disasterous. i had called wxbrief to give them a pirep of what i'd just seen and been through and the briefer informed me that at Geo. Bush (IAH) they had had gusts of 45kts upon the passage of the front. it was an interesting night. oh, and one more thing. fly the airplane! don't turn a non emergency into an emergency. stay calm and fly the plane. there will be plenty of time later to be nervous. tune out what you have to and focus on the situation at hand.
Title: Re: WX and decision making
Post by: Gulfstream Driver on January 17, 2006, 09:15:25 PM
Good advice. Your instructor would be proud. Glad you made it down ok.
It's always better to be on the ground wishing you were in the air, then in the air wishing you were on the ground.
Title: Re: WX and decision making
Post by: Plthijnx on January 17, 2006, 09:47:40 PM
yeah, no doubt. and i told my g/f that saying today as a matter of fact....
as soon as i take care of a few things around the house i'm going to go back and complete my cfi/cfii/mei training even though i'm almost to the hiring minimums of the pro's.
Title: Re: WX and decision making
Post by: Mike on January 18, 2006, 02:12:30 AM
This is some very good advise Texas! I will pass this on to my former students.
I always tell them the IFR rating is the best rating you will ever get. Even if you don't use it much like me. But I did run into the clouds once flying offshore with the helicopter and the 180-climbing-turn came naturally I have to say. No sweat at all. But if I wouldn't have had the rating... who knows?!
Here is where it comes in handy flying a helicopter ;) Just land somewhere and wait it out! ;D
Title: Re: WX and decision making
Post by: Mike on January 18, 2006, 02:13:45 AM
PS: this would almost fit better in the "there I was" section, wouldn't it?
Title: Re: WX and decision making
Post by: Plthijnx on January 18, 2006, 02:53:26 AM
yeah, i had that as an afterthought......you can move it, ya know! in fact i was going to ask you to do that anyway..... :)
Title: Re: WX and decision making
Post by: Mike on January 18, 2006, 03:17:20 AM
wow, I did it. (brag)
I hope people don't get lost and keep responding to this one. It's very important to me I want to underline again....
Title: Re: WX and decision making
Post by: SkyKing on May 02, 2006, 07:54:51 PM
Some years back, there was a guy who took off with his family aboard and went overdue.
We talked to his flying buddies, each of whom swore that even though he was IFR rated, if there was a cloud in the sky, he would go back and land. It took three days to find the wreckage.
He spent the last 2-1/2 hours of his life in thunderstorms WITHOUT TALKING TO ANYONE ON THE RADIO. If he had, maybe he would have adjusted his altimeter and not run into a mountain 50 feet below the crest.
Okay, so maybe he was too stupid to live, but he took innocents with him, and that is INEXCUSABLE.
Sometimes we get pushed to show how we're great, brave, hotshot pilots. I show that by being brave enough to say "I don't like the weather and I'm staying on the ground."
It is much better for your plane to follow an ELT signal than for it to be the source of one.
Title: Re: WX and decision making
Post by: fireflyr on May 05, 2006, 01:47:49 AM
Some years back, there was a guy who took off with his family aboard and went overdue.
We talked to his flying buddies, each of whom swore that even though he was IFR rated, if there was a cloud in the sky, he would go back and land. It took three days to find the wreckage.
He spent the last 2-1/2 hours of his life in thunderstorms WITHOUT TALKING TO ANYONE ON THE RADIO. If he had, maybe he would have adjusted his altimeter and not run into a mountain 50 feet below the crest.
Good story and it points out a perception problem common among private aviators, that is, they get the rating but they "save it for emergencies" so they won't go out and do some flights in IMC to get proficient and then one day when they do need it----well, they just wander around for 2 1/2 hours in thunderstorms and hit that mountain 50 feet below the peak. I believe that if you have the rating you should be out there in the clag (with a senior pilot or instructor, if necessary) doing some actual flying. There is nothing wrong with flying single engine IFR on purpose, in properly calculated situations so there are adequate "outs" if needed. IFR flying is NOT magic, is Not dangerous, and is NOT just for super pilots ! I am always happy to ride along with any pilot who just wishes to get some experience, hell, I don't even charge them anything if they're budget aviators (broke like me). These people are not stupid, they are under-informed and it's up to those with experience to share that experience without being condescending. Just because we have the experience is why we should be the first one to give some insight to a neophyte without making him/her feel like they're talking to God's reason for pilot wings. If even the finest and the greatest (Scott Crossfield comes to mind--and I certainly mean no disrespect) can screw the pooch, I sure as hell am not going to ridicule someone like JFK JR, who was certainly a victim of poor decision making, caused perhaps by poor instruction or poor mentoring.
Title: Re: WX and decision making
Post by: fliboye on May 16, 2006, 08:56:35 AM
that which does not kill us makes us stronger and smarter. or say WOW I won't do that again ;) I always find it humbling when navigating in the not so nice weather to pop out the other side of a line of weather and then look back and say why did I just fly through that, Thats why we get paid the big bucks(LOL). hehehehehehe ;D
Title: Re: WX and decision making
Post by: SkyKing on May 16, 2006, 04:55:46 PM
Some years back, there was a guy who took off with his family aboard and went overdue.
We talked to his flying buddies, each of whom swore that even though he was IFR rated, if there was a cloud in the sky, he would go back and land. It took three days to find the wreckage.
He spent the last 2-1/2 hours of his life in thunderstorms WITHOUT TALKING TO ANYONE ON THE RADIO. If he had, maybe he would have adjusted his altimeter and not run into a mountain 50 feet below the crest.
Good story and it points out a perception problem common among private aviators, that is, they get the rating but they "save it for emergencies" so they won't go out and do some flights in IMC to get proficient and then one day when they do need it----well, they just wander around for 2 1/2 hours in thunderstorms and hit that mountain 50 feet below the peak. I believe that if you have the rating you should be out there in the clag (with a senior pilot or instructor, if necessary) doing some actual flying. There is nothing wrong with flying single engine IFR on purpose, in properly calculated situations so there are adequate "outs" if needed. IFR flying is NOT magic, is Not dangerous, and is NOT just for super pilots ! I am always happy to ride along with any pilot who just wishes to get some experience, hell, I don't even charge them anything if they're budget aviators (broke like me). These people are not stupid, they are under-informed and it's up to those with experience to share that experience without being condescending. Just because we have the experience is why we should be the first one to give some insight to a neophyte without making him/her feel like they're talking to God's reason for pilot wings. If even the finest and the greatest (Scott Crossfield comes to mind--and I certainly mean no disrespect) can screw the pooch, I sure as hell am not going to ridicule someone like JFK JR, who was certainly a victim of poor decision making, caused perhaps by poor instruction or poor mentoring.
"If in trouble, or in doubt, fly triangles, scream and shout!"
My first lesson in instrument flying involved a max-performance climb to the plane's service ceiling. The lesson? "Most of the ratty wx is DOWN THERE. The rocks, towers, wires and buildings are DOWN THERE. And we're UP HERE, and from UP HERE we can make our way around the bad stuff and talk to a lot of people with radios and radar, who want nothing more than to see us land safely."
Title: Re: WX and decision making
Post by: fliboye on June 02, 2006, 04:53:23 PM
I once was jumpseating on a an AAirlines flight out of miami when the first officer said weather what weather, it is not whether or not your going but whether or not you are going to get in. ::)
Title: Re: WX and decision making
Post by: cj5_pilot on September 03, 2006, 02:01:32 AM
Dean Eicholtz, they check pilot that gave me my final checkride for my Private had an interesting theory on weather. It was simple: If the weather looks iffy, have a beer. No flying for eight hours after that! Never had to use it myself--I don't scud run. Still and all, an interesting theory.
Title: Re: WX and decision making
Post by: Baradium on September 03, 2006, 04:59:05 AM
Dean Eicholtz, they check pilot that gave me my final checkride for my Private had an interesting theory on weather. It was simple: If the weather looks iffy, have a beer. No flying for eight hours after that! Never had to use it myself--I don't scud run. Still and all, an interesting theory.
In Alaska, VFR weather isn't "iffy" until it's below 500 ft ceiling. 500 and 2 is VFR weather... ;)
Title: Re: WX and decision making
Post by: fireflyr on September 03, 2006, 03:31:18 PM
Dean Eicholtz, they check pilot that gave me my final checkride for my Private had an interesting theory on weather. It was simple: If the weather looks iffy, have a beer. No flying for eight hours after that! Never had to use it myself--I don't scud run. Still and all, an interesting theory.
"I don't scud run"---GOOD philosphy!!! Try never to compromise your limitations no matter how tempting it is. |:)\ We had a scud running RV6 try to move a mountain last week attempting to get into Petaluma, he ducked under a 500 fog layer but unfortuately there was a 600 foot hill between him and the airport---scratch 1 nice airplane and 2 nice people! :-\
Title: Re: WX and decision making
Post by: tundra_flier on September 09, 2006, 05:04:31 AM
I agree with CJ5, I only fly for fun. Scud running isn't any fun. :( Though I've been tempted a couple times by "get-home-itise". But I've always come to my senses and bought a ticket on Frontier. You guys have a lot more flashy things on your panels and a spare engine to boot. :)
Phil
Title: Re: WX and decision making
Post by: Baradium on September 09, 2006, 06:54:47 AM
I agree with CJ5, I only fly for fun. Scud running isn't any fun. :( Though I've been tempted a couple times by "get-home-itise". But I've always come to my senses and bought a ticket on Frontier. You guys have a lot more flashy things on your panels and a spare engine to boot. :)
Phil
I like flashy thingies! :D
If you were going to scud run, you'd want to be very familiar with the area, have an IFR aircraft and IFR training (very important because you don't have nearly as many outside clues), and an IFR GPS would be nice...
I agree that not scud running is the best idea.... better to get home late than not at all.
Title: Re: WX and decision making
Post by: fireflyr on September 09, 2006, 07:47:30 AM
I agree with CJ5, I only fly for fun. Scud running isn't any fun. :( Though I've been tempted a couple times by "get-home-itise". But I've always come to my senses and bought a ticket on Frontier. You guys have a lot more flashy things on your panels and a spare engine to boot. :)
Phil
I like flashy thingies! :D
If you were going to scud run, you'd want to be very familiar with the area, have an IFR aircraft and IFR training (very important because you don't have nearly as many outside clues), and an IFR GPS would be nice...
I agree that not scud running is the best idea.... better to get home late than not at all.
Ya'll don't NEED an IFR gps---Git yerself a Garmin 296 handheld and you'll have more information than a 1980s Boeing 747, then you'll be able to fly VFR (even at minimums) with confidence--got terrain awareness--but best of all get the IFR rating. 8)
Title: Re: WX and decision making
Post by: happylanding on September 09, 2006, 10:30:07 PM
I've a garmin GPSmap 295 and the only thing it doesn't do is coffee. if you get the extension with route charts also (I mean to drive) you will find all the restaurants, hotel and whatever comes to mind for a 100$ hamburger! btw, it keeps annoying you with alarms if you're flying slightly above minimums and if your route is near CTR, since it keeps telling you're near airspaces. but it's a nice toy! :D
Title: Re: WX and decision making
Post by: Baradium on September 10, 2006, 09:19:57 AM
I've a garmin GPSmap 295 and the only thing it doesn't do is coffee. if you get the extension with route charts also (I mean to drive) you will find all the restaurants, hotel and whatever comes to mind for a 100$ hamburger! btw, it keeps annoying you with alarms if you're flying slightly above minimums and if your route is near CTR, since it keeps telling you're near airspaces. but it's a nice toy! :D
Airspace alarms could be a good thing if you *weren't* paying attention. ;) Of course, it's generally good practice to know anyway.
A trap some pilots get into is relying so much on the GPS that they have no idea what is going on if it fails. You never want to be in a situation where a single instrument failure can result in your loss of situational awareness!
Speaking of food: In the US there is a resturant chain called Lamberts. They are located in Sikeston, Missouri (SIK) and Foley, Alabama. The founder was a pilot and they are very pilot friendly. They are a pretty popular resturant and a lot of tour buses like to stop there as part of trips (they can have an hour wait fairly easily). However, if you fly in you can radio in to the FBO as you're coming in for the "Lamberts Shuttle" and they will send a van to get you. As a pilot you and your passengers get taken to the back door, you bypass the line and get the first availible table. Makes you feel really special. ;) I've been to each location once. The first time to Sikeston in an airplane and the second time to Foley on the ground. I enjoyed both times but it was fun to get the VIP treatment the first time.
I'm sure there are other places like that around, lamberts is the only one I've been to personally.
I also know that Birmingham, AL has free otis spunkmeyer cookies at the FBO and Huntsville, AL's FBO has brand new ford focuses loaned by the local ford dealer for free courtesy cars for transient pilots. Definately worth looking into what's around when you are going somewhere. That's the big disadvantage of airline flying, I don't get to do a lot of that fun stuff...
Title: Re: WX and decision making
Post by: Frank N. O. on September 10, 2006, 10:05:46 AM
Wow! Lamberts sure sounds cool, everything right down to the choice of the loaner car! Now if only I could get a PPL and a plane....
At least I can get confirmed that there are nice places in the world here, that's always a great booster for my mood, although it's not fun know none of them are on this part of the planet. Frank
Title: Re: WX and decision making
Post by: cj5_pilot on September 10, 2006, 06:20:10 PM
I've a garmin GPSmap 295 and the only thing it doesn't do is coffee. if you get the extension with route charts also (I mean to drive) you will find all the restaurants, hotel and whatever comes to mind for a 100$ hamburger! btw, it keeps annoying you with alarms if you're flying slightly above minimums and if your route is near CTR, since it keeps telling you're near airspaces. but it's a nice toy! :D
Tundra has a Garmin handheld (don't recall what model) we took out 3 years ago Silver Salmon fishing....it kept showing the boat being about a 1/4 mile inland ???
We just figured that 6 knots and sea level just made it lazy ;D
Title: Re: WX and decision making
Post by: Baradium on September 10, 2006, 08:19:38 PM
I've a garmin GPSmap 295 and the only thing it doesn't do is coffee. if you get the extension with route charts also (I mean to drive) you will find all the restaurants, hotel and whatever comes to mind for a 100$ hamburger! btw, it keeps annoying you with alarms if you're flying slightly above minimums and if your route is near CTR, since it keeps telling you're near airspaces. but it's a nice toy! :D
Tundra has a Garmin handheld (don't recall what model) we took out 3 years ago Silver Salmon fishing....it kept showing the boat being about a 1/4 mile inland ???
We just figured that 6 knots and sea level just made it lazy ;D
LOL! That's the problems with handhelds and one of the reasons you can't use them IFR... they can be a bit off. So can regular IFR GPSs, but they are supposed to be more accurate than that. IFR installations require a lot of study of how they pick up signal to make sure nothing distorts it. ;)
Title: Re: WX and decision making
Post by: Ted_Stryker on September 11, 2006, 04:51:34 PM
GPS units can vary in accuracy depending on the type of receiver, and how many satellites are "visible" to it. A GPS receiver really needs and unobstructed antenna outside for maximum reception (which is why such receivers are on top of aircraft, not under them, and why they say "DO NOT PAINT" on them too).
Remember too that if you get a RAIM warning, you're not good for IFR use on one.
AOPA has a couple of good seminars on their safety sub-site for both VFR and IFR use of GPS units.
The programs even count towards your FAA Wings Program as seminars! Check 'em out! ;D
Title: Re: WX and decision making
Post by: happylanding on September 12, 2006, 10:02:37 PM
Wow! Lamberts sure sounds cool, everything right down to the choice of the loaner car! Now if only I could get a PPL and a plane....
At least I can get confirmed that there are nice places in the world here, that's always a great booster for my mood, although it's not fun know none of them are on this part of the planet. Frank
Come on! I've only been to Denmark when I was a child, but I remember it as being a nice place....And we do have beautiful places here too, scattered around Europe! If you are looking for something breathtaking, try once Scotland, I assure you you will be amazed by it! it actually takes your breath awayyyyyyyy.....:) the first time I visited it - and I try to go whenever I can - I could not think such a place existed. I assure you the colours you find there... I've not seen anywhere yet. a green that's the idea you could have had of a fairy place when toddler, a blue sky that's sometimes patched by clouds that looks like soft ice cream and the brown, it has a "scent" of chocolate and violent together....and if I've not convinced you, gimme a sec and I'll post the pics, even if they were taken on ground! :)
Title: Re: WX and decision making
Post by: tundra_flier on September 20, 2006, 02:26:54 AM
Quote
Tundra has a Garmin handheld (don't recall what model) we took out 3 years ago Silver Salmon fishing....it kept showing the boat being about a 1/4 mile inland
We just figured that 6 knots and sea level just made it lazy
My little GPS III is perfectly accurate...the coast was just in the wrong location! ;) Seriously though, it has aiports mapped out very accurately. Anything else, roads, rivers, lakes etc tends to be a couple hundred feet off. But then, even at C-150 speeds, if you need to know the location of the coast line from your GPS to within 100ft, it's probably too late anyway. :-\
Phil
Title: Re: WX and decision making
Post by: TheSoccerMom on September 25, 2006, 01:52:47 AM
Just last winter I was using a 295 with the latest update, and it routinely and consistently put the airport in the harbor, almost a mile offshore. There was no budging it. And, we flew out of there for a month.
Using a VFR-only GPS in IFR conditions is asking for trouble, but then again, I guess I am a big scaredy-chicken.
Fortunately we also had the IFR panel-mount, but it was an eye-opener, just the same. (We had the VFR ones for survey reference only.) It was a stark difference....
Just my two cents' worth... pluck, pluck...
Title: Re: WX and decision making
Post by: cj5_pilot on September 25, 2006, 03:43:02 PM
Title: Re: WX and decision making
Post by: tundra_flier on September 25, 2006, 09:22:34 PM
Quote
Just last winter I was using a 295 with the latest update, and it routinely and consistently put the airport in the harbor, almost a mile offshore. There was no budging it. And, we flew out of there for a month.
Using a VFR-only GPS in IFR conditions is asking for trouble, but then again, I guess I am a big scaredy-chicken.
Fortunately we also had the IFR panel-mount, but it was an eye-opener, just the same. (We had the VFR ones for survey reference only.) It was a stark difference....
I've always heard that using 2 GPS's in close proximity will cause distortion errors, since they'll recieve false signals off each other. Did you try turining off the panel mount GPS? It did dawn on me after the fact that when using my GPS III on the boat, there was a dash mount GPS being used in the wheelhouse at the same time.
Phil
Title: Re: WX and decision making
Post by: Baradium on September 25, 2006, 10:08:01 PM
I've always heard that using 2 GPS's in close proximity will cause distortion errors, since they'll recieve false signals off each other. Did you try turining off the panel mount GPS? It did dawn on me after the fact that when using my GPS III on the boat, there was a dash mount GPS being used in the wheelhouse at the same time.
Phil
I've never heard of GPS units sending signals myself.
I've flown in multiple aircraft with dual GPS units installed. My multi was in a seminole with dual Garmin 430s and same was installed in the Arrows I finished my commercial in. The recievers are next to eachother and they are both IFR certified. For some operations there are actually requirements for dual installed GPS units, although I believe those all involve commercial operators (such as 121 carriers) in specific instances.
Title: Re: WX and decision making
Post by: Ted_Stryker on September 25, 2006, 10:15:21 PM
Just last winter I was using a 295 with the latest update, and it routinely and consistently put the airport in the harbor, almost a mile offshore. There was no budging it. And, we flew out of there for a month.
Using a VFR-only GPS in IFR conditions is asking for trouble, but then again, I guess I am a big scaredy-chicken.
Fortunately we also had the IFR panel-mount, but it was an eye-opener, just the same. (We had the VFR ones for survey reference only.) It was a stark difference....
I've always heard that using 2 GPS's in close proximity will cause distortion errors, since they'll recieve false signals off each other. Did you try turining off the panel mount GPS? It did dawn on me after the fact that when using my GPS III on the boat, there was a dash mount GPS being used in the wheelhouse at the same time.
Phil
I'd have to agree with Baradium on this one. GPS units are recievers. Unless there is a problem with a unit having RF interference with the nature of the electronics, there should be no problem with multiple in the aircraft. It is possible you had a faulty unit, or the antenna for one was in a poor location. The more satellites visible to a unit, the greater the accuracy. If the handheld unit was having a problem seeing satellites due to the metal structure of the plane and no external antenna, that would explain it's innaccuracy compared to the panel mounted one.
Title: Re: WX and decision making
Post by: tundra_flier on September 25, 2006, 11:41:54 PM
Quote
I'd have to agree with Baradium on this one. GPS units are recievers. Unless there is a problem with a unit having RF interference with the nature of the electronics, there should be no problem with multiple in the aircraft. It is possible you had a faulty unit, or the antenna for one was in a poor location. The more satellites visible to a unit, the greater the accuracy. If the handheld unit was having a problem seeing satellites due to the metal structure of the plane and no external antenna, that would explain it's innaccuracy compared to the panel mounted one.
Mine came with a warning about errors if too close to another GPS reciever. All antennas and recievers actually emmit the signal they're receiving. An antenna is a passive signal amplifying device, and part of the amplified signal is emmitted. Likewise the first stage of any RF reciever is an electronic signal amplifier. Some of the amplified signal is again emmitted. What can happen with two GPS recievers, or even FM radio for that matter, if close enough they will recieve not only the source signal (from the satelites) but also a second signal from the other receiver. The second signal is just slightly out of phase with the source so you get distorted information. This caused us all no end of frustrations when building amp circuits in the basic electronics labs, until the prof explained we were causing interference with each other. :P
When using dual GPS systems, they must have shielding from each other and use a common antenna, or have the antenna's carefully located to prevent interfering with each other. Hand held units aren't designed for that.
Phil - Electrical Engineer
Title: Re: WX and decision making
Post by: Baradium on September 26, 2006, 12:48:31 AM
Mine came with a warning about errors if too close to another GPS reciever. All antennas and recievers actually emmit the signal they're receiving. An antenna is a passive signal amplifying device, and part of the amplified signal is emmitted. Likewise the first stage of any RF reciever is an electronic signal amplifier. Some of the amplified signal is again emmitted. What can happen with two GPS recievers, or even FM radio for that matter, if close enough they will recieve not only the source signal (from the satelites) but also a second signal from the other receiver. The second signal is just slightly out of phase with the source so you get distorted information. This caused us all no end of frustrations when building amp circuits in the basic electronics labs, until the prof explained we were causing interference with each other. :P
When using dual GPS systems, they must have shielding from each other and use a common antenna, or have the antenna's carefully located to prevent interfering with each other. Hand held units aren't designed for that.
Phil - Electrical Engineer
The dual units don't share any components, destroys the redundancy, the antennas are right next to eachother on all the dual installs I've seen as well. ;)
Don't know about the rest, I do know that one of the reasons IFR installs are so $$$ is they do so many checks for interference. However, this applies on single installs as well. Handheld units just don't have the ability for accuracy needed for IFR flight. They are helpful for VFR, but you have to watch them because of this.
I'm still a bit skeptical that merely the presences of another GPS unit automatically causes the descrepency....
Title: Re: WX and decision making
Post by: tundra_flier on September 26, 2006, 04:21:10 AM
Quote
I'm still a bit skeptical that merely the presences of another GPS unit automatically causes the descrepency....
CAN cause an error, not necessarily will. ;)
Phil
Title: Re: WX and decision making
Post by: Baradium on September 26, 2006, 04:54:25 AM
I'd have to agree with Baradium on this one. GPS units are receivers. Unless there is a problem with a unit having RF interference with the nature of the electronics, there should be no problem with multiple in the aircraft. It is possible you had a faulty unit, or the antenna for one was in a poor location. The more satellites visible to a unit, the greater the accuracy. If the handheld unit was having a problem seeing satellites due to the metal structure of the plane and no external antenna, that would explain it's innaccuracy compared to the panel mounted one.
Mine came with a warning about errors if too close to another GPS receiver. All antennas and receivers actually emit the signal they're receiving. An antenna is a passive signal amplifying device, and part of the amplified signal is emitted. Likewise the first stage of any RF receiver is an electronic signal amplifier. Some of the amplified signal is again emitted. What can happen with two GPS receivers, or even FM radio for that matter, if close enough they will receive not only the source signal (from the satelites) but also a second signal from the other receiver. The second signal is just slightly out of phase with the source so you get distorted information. This caused us all no end of frustrations when building amp circuits in the basic electronics labs, until the prof explained we were causing interference with each other. :P
When using dual GPS systems, they must have shielding from each other and use a common antenna, or have the antenna's carefully located to prevent interfering with each other. Hand held units aren't designed for that.
Phil - Electrical Engineer
I don't doubt your credentials or knowledge on the issue at all. I just suspect that since it seemed to be a consistent error that it was likely from a more stable interference factor such as the airframe shielding satellite visibility that from any local sources. Granted, on the antenna issue they do have the tendency to have some feedback potential, though I've only seen that in situations where higher power was involved, and proximity was extremely close.... unless there was a defect in the shielding or in the electronic circuit design or component failure that generated an RF wave harmonic allowing for distortion potential.
In any case, this would be a situation of debate in a vacuum since we have no direct ability to examine the plane, nor the unit. Can you hook up the handheld unit to the external antenna and get the distortion to disappear? How about with it outside of the aircraft? If the distortion remains, there may be an internal error.
As already noted, VFR units don't have the accuracy of IFR rated ones, and panel mount will, obviously, give the best results versus handheld units of either VFR or IFR types due to the magnetic anomaly and signal leak survey mapping required for a proper panel install.
If you go to AOPA's website, the Air Safety Foundation sub-site there has a series of presentations on GPS for VFR and GPS for IFR, describing the systems, accuracies, and other factoids that may be of assistance to clearing up this anomaly to an extent as well.
Please understand, we are simply offering advice for the sake of assistance. Not challenging you. :)
Title: Re: WX and decision making
Post by: tundra_flier on September 26, 2006, 03:20:36 PM
Quote
So CAN having a comm radio.
Comm radio is a very different frequency from GPS, so not likely.
Quote
Please understand, we are simply offering advice for the sake of assistance. Not challenging you.
Understood. Thanks for the web site info too, I'll have to read through that tonight.
I just found it very odd that their hand held was that far off regarding an airport location. Mine is frequently off regarding rivers, roads and that sort of thing. But I can zoom in and it'll accurately show me where on the airport I'm at with the map tracks describing the taxiways perfectly. If it was simply a poor signal, due to aircraft structure in the way of their GPS or something blocking the satelites, I'd have expected the error to be more random. That's what got my curiousity up. And being an engineer, I just gotta find the solution. ;D
Phil
Title: Re: WX and decision making
Post by: Ted_Stryker on September 26, 2006, 03:44:36 PM
Comm radio is a very different frequency from GPS, so not likely.
Quote
Please understand, we are simply offering advice for the sake of assistance. Not challenging you.
Understood. Thanks for the web site info too, I'll have to read through that tonight.
I just found it very odd that their hand held was that far off regarding an airport location. Mine is frequently off regarding rivers, roads and that sort of thing. But I can zoom in and it'll accurately show me where on the airport I'm at with the map tracks describing the taxiways perfectly. If it was simply a poor signal, due to aircraft structure in the way of their GPS or something blocking the satelites, I'd have expected the error to be more random. That's what got my curiousity up. And being an engineer, I just gotta find the solution. ;D
Phil
As an engineer myself, I can relate to that |:)\
I've had a handheld GPS system for my Pocket PC that works pretty well, even gets fair reception from inside my car without resorting to an external antenna. I can see it change accurracy though from when it's inside the car and outside if moving, such as walking from my car to a plane or something. I exprimented with it a bit and found that if it's outside, my particular unit can be accurate within about 20 feet dependably. Inside my car I found that the error increased to about 75 feet or so. The error drift is, for some reason, consistent in terms of how it plots. I suspect the reason behind that is more of a software driver with the way the unit does math, perhaps with floating point error correction, than any other factor. I have nothing to back that up with just yet, but the predictability of which direction the error falls on seems to indicate the error is algorithmic in nature.
Just my thoughts. I may be a bit biased on that due to my engineering background being one of software.
Title: Re: WX and decision making
Post by: fireflyr on September 27, 2006, 11:58:08 PM
WOW, BOTH you guys are engineers!!! |:)\ |:)\ I've always wanted to drive a locomotive---Can you give me a ride? HUHUHUH? pleaseoplease!!!! :-*
Title: Re: WX and decision making
Post by: Ted_Stryker on September 28, 2006, 12:13:17 AM
You know how you tell an extroverted engineer? They stare at YOUR shoes when the talk to you.
Tundra knows LOTS of engineer jokes ;)
HEHE--that's good Ok Tundra, let's hear some more----just tell'em slow (I'm Polish)
Title: Re: WX and decision making
Post by: tundra_flier on October 02, 2006, 10:02:52 PM
An Engineer, Physisist and mathmatition were all told that the first one to cross the room would get a kiss from the beautiful woman on the other side. But they each could only cross half the remaining distance on each of their turns.
The mathmatition gave up immediatly because it was impossible to ever reach the other side.
The physisist tried 3 turns to confirm his hypothesis and then gave up.
The engineer keep going - he knew he could get close enough. ;)
Title: Re: WX and decision making
Post by: TheSoccerMom on October 03, 2006, 03:06:10 AM
I've never heard of units interfering with each other; most of the aircraft on survey jobs have 3 units installed at all times.
I just figured it was the inaccuracy inherent with a cheaper, VFR-only unit.
It just made me even more of a believer in the IFR unit, though.... Cheers!! ???
Title: Re: WX and decision making
Post by: cj5_pilot on October 03, 2006, 05:06:16 AM
