Hand held GPS

Tom-D

Tom-D

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Tom-D
Do you believe the hand held GPS such as the Garmin 496 should be allowed to be used on IFR enroute and approach as the only means of nav?
 
Hmmm...

...enroute, perhaps yes, but maybe only in a radar environment.

Approach, no way no how.


Guess all that adds up to, regretfully, no.
 
I don't think any single source should be the only means of navigation once your out of sight of the home airport.
 
Interesting question.

I can certainly see a yoke mounted 496 with a secure antenna mount and good satellite reception being better (I'll leave that term undefined for the moment) than the panel mounted IFR certified GX55 in our club 172.

What I see as the problem is the lack of quality control on the installation. I would say a 696 on my lap with the antenna sliding around the glare shield as a big potential problem.

I believe we could come up with standards that would allow this to be safe and effective.

Joe

edit: I meant GX50, the 55 is the VFR version
 
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Tom-D said:
Do you believe the hand held GPS such as the Garmin 496 should be allowed to be used on IFR enroute and approach as the only means of nav?
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I have mixed feelings on this. The primary differences between a TSO'd panel mount and a handheld are that the latter hasn't demonstrated that it meets any standards plus AFaIK, the handhelds currently available don't have any capability to indicate to the user if and when there's a navigation error. If those two issues were addressed I'd have no problem allowing their use for enroute operations, especially with an external antenna (the only portion of the system where mounting location really matters).

But without some sort or certification, you'd be relying on the manufacturer to determine what level of reliability is adequate. Well known players would likely be fine, but who's to say that Mattel or Tyco might not develop a similar looking unit with inferior performance. The flip side is that certification would no doubt increase the cost of any handheld.
 
No, not as only means of NAV.
 
Areeda said:
What I see as the problem is the lack of quality control on the installation. I would say a 696 on my lap with the antenna sliding around the glare shield as a big potential problem.
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I would see this as the biggest hurdle to overcome.
 
RMCN172RG said:
I don't think any single source should be the only means of navigation once your out of sight of the home airport.
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It's legal to use a single VOR receiver for IFR. Whether or not you feel comfortable with this is another question.
 
Not unless I can see the handheld GPS meeting specific standards for accuracy, integrity, and availability.
 
No way :nono:

Must meet TSO C129a for supplemental IFR navigation or TSO C145a/C146a Sole means of IFR navigation and installed in compliance with AC 20-138a or equivalent. Doesn't come close, this is a pure pipe dream.
 
The real issue is whether one can obtain assurance that the movement of the unit and antenna with a handheld (be it from place to place inside one airplane or from airplane to airplane) will not compromise the operation and integrity of the system. So far, the technology for that isn't there. Should it ever arrive and the FAA be satisfied with its reliability, I'd be happy to use it.
 
Ron Levy said:
The real issue is whether one can obtain assurance that the movement of the unit and antenna with a handheld (be it from place to place inside one airplane or from airplane to airplane) will not compromise the operation and integrity of the system. So far, the technology for that isn't there. Should it ever arrive and the FAA be satisfied with its reliability, I'd be happy to use it.
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I don't understand why you would say that when they are made to be moved from aircraft to aircraft. I use my Lorance 2000C in three different aircraft it gives me the same position at the same spot in each aircraft.

It knows where the antenia is, that is all any GPS can know.

It has the same data base as any GPS.

MY only worry is the antenia would get knocked into the baggage compartment just when I need it most.
 
John Collins said:
No way :nono:

Must meet TSO C129a for supplemental IFR navigation or TSO C145a/C146a Sole means of IFR navigation and installed in compliance with AC 20-138a or equivalent. Doesn't come close, this is a pure pipe dream.
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My question asked, wouldn't you like to see those requirements removed?
 
What do you mean? There is no technical reason RAIM (and FDE) functions couldn't be implemented in a handheld GPS.
 
Tom-D said:
Do you believe the hand held GPS such as the Garmin 496 should be allowed to be used on IFR enroute and approach as the only means of nav?
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Enroute I could see but not approach but then I only have a 296
 
Tom-D said:
My question asked, wouldn't you like to see those requirements removed?
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No.

TSO C146a requires compliance with RTCA DO-229D which is a detailed 564 page specification of the requirements for IFR GPS operation. There are so many requirements that IMHO that a portable GPS can not comply with that it is a total waste of time to even wish for. It won't happen.
 
Ron Levy said:
The real issue is whether one can obtain assurance that the movement of the unit and antenna with a handheld (be it from place to place inside one airplane or from airplane to airplane) will not compromise the operation and integrity of the system. So far, the technology for that isn't there. Should it ever arrive and the FAA be satisfied with its reliability, I'd be happy to use it.
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This is a gross understatement.
 
Quote:
Originally Posted by Ron Levy
The real issue is whether one can obtain assurance that the movement of the unit and antenna with a handheld (be it from place to place inside one airplane or from airplane to airplane) will not compromise the operation and integrity of the system. So far, the technology for that isn't there. Should it ever arrive and the FAA be satisfied with its reliability, I'd be happy to use it.

This is a gross understatement.
__________________
Regards,

John D. Collins
CFI, CFII, MEI



John Collins said:
This is a gross understatement.
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Please explane how the system is compromised by moving it? as long as it can see the sky it will know where it is.
 
All the requirements mean nothing if the signal gets jammed or spoofed. That is a far bigger risk than anything addressed in the RTCA or TSO specs. Jamming is easier than most GPS users think... and it doesn't take the military to do so. And WAAS can't overcome the jamming.

Do you practice flying IFR without GPS? What would you do if the system went down?

Under the right conditions, I would be in favor of allowing portable units under IFR for lateral guidance.... those conditions would include an appropriate certification program and system operating requirements. I temper that with the knowledge that some pilots would "cheat" the system and use equipment that was not appropriately certified.
 
Please explane how the system is compromised by moving it? as long as it can see the sky it will know where it is.[/quote]

My comment regarding gross understatement is the claim that the antenna position is the real issue. It is an issue, but only one of dozens.

With respect to the TSO C146a GPS antenna, it must comply with a 5 degree above the horizon mask angle requirement around 360 degrees of direction and even the original GNS530 and GNS480 antenna's did not comply with this requirement and had to be replaced. The installation must be tested to assure that there isn't a loss of signal of any portion of the sky except when maneuvering. The VHF transmitters have to be tested on about 8 frequencies to assure that signal is not lost due to interference by harmonics. The installation needs to be configured with the antenna location measured from the ground when the aircraft is on the ground to the nearest foot so that the glidepath is in a predictable location. The antenna needs to have a higher gain than the standard antenna and a better signal to noise ratio.

I use a GPSMAP 696 in my airplane and it is great, but it wasn't ever intended to be an IFR unit, even though it has many great features. For IFR, I use my GNS530W.
 
wsuffa said:
All the requirements mean nothing if the signal gets jammed or spoofed. That is a far bigger risk than anything addressed in the RTCA or TSO specs. Jamming is easier than most GPS users think... and it doesn't take the military to do so. And WAAS can't overcome the jamming.

Do you practice flying IFR without GPS? What would you do if the system went down?

Under the right conditions, I would be in favor of allowing portable units under IFR for lateral guidance.... those conditions would include an appropriate certification program and system operating requirements. I temper that with the knowledge that some pilots would "cheat" the system and use equipment that was not appropriately certified.
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The jamming can come from your own VHF Com.

Yes, I practice flying with VOR and my trusty KNS80 for RNAV routing.

Wishful thinking, it will never happen. Hand held radios with a built in VOR have been around for decades, when do you think they will be approved for IFR flight?
 
Tom-D said:
I don't understand why you would say that when they are made to be moved from aircraft to aircraft. I use my Lorance 2000C in three different aircraft it gives me the same position at the same spot in each aircraft.

It knows where the antenia is, that is all any GPS can know.

It has the same data base as any GPS.

MY only worry is the antenia would get knocked into the baggage compartment just when I need it most.
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The effects of nearby conductive surfaces on the signals reaching your handheld's antenna is very significant and also very complicated to analyze. You might think that the GPS position is always accurate because it generally is, but there are errors and the errors can grow dramatically when the signals from the SVs compete with reflections from nearby objects. This is especially true when there's precipitiation that attenuates the signals and/or when there are noise sources to cope with as well (p-static, emissions from the aircraft, etc). Using a patch antenna and putting the antenna on top of the cabin minimizes these issues to a very great extent, the typical helical antenna on a handheld located inside the cabin is far worse.

In addition as has been mentioned, the current crop of handhelds has no self check ability (RAIM, etc). There's no technical reason why this couldn't be added although it's likely that you'd get a lot of warnings using the built in antenna (I suspect that this is the main reason why this feature doesn't exist on the handhelds as there's no additional production cost associated with it). Finally, while you might expect that the DB for a handheld is identical to their IFR approved counterparts, I think it's likely that there's less checking and certainly less FAA mandated process associated with it's generation and distribution.

But the bottom line IMO is that because the FAA hasn't tested and approved the hardware, software, DB, antenna, and installation of your handheld, they will NOT ever consider approving it's use for IFR navigation. This doesn't mean that they'd never approve a portable for IFR, just that there would need to be standards and testing to ensure compliance with those standards.

This isn't a lot different than the requirements for modifications to certified a aircraft. If it was legal to replace the standard engine in a 172 with something from Mazda or Kia sans a STC (and the required testing to obtain the STC) someone might come up with an engine swap that would scare anyone with any common sense. The upgrade from Mazda might be well engineered and capable of passing the certification testing but what about an engine thrown together at Joe's garage and biker bar?
 
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You mean like the one point in the track that's 200 miles off or the instant climb and descent of 1000 feet are not accurate?

I've seen those using the built in antenna and the yoke mount, plus drops in reception lasting a few minutes.

I've thought about using the external antenna on top of the instrument panel and the 12v adaptor but have not bothered with routing the wires, etc. It's just easier to slip it into the yoke mount as is with good batteries.

I'm considering panel mounting the unit, current 196 but eventually 496, with an external antenna which should improve performance and reliability. Has anyone done that who can provide a PIREP?
 
gismo said:
But the bottom line IMO is that because the FAA hasn't tested and approved the hardware, software, DB, antenna, and installation of your handheld, they will NOT ever consider approving it's use for IFR navigation. This doesn't mean that they'd never approve a portable for IFR, just that there would need to be standards and testing to ensure compliance with those standards.
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And that is the crux of the matter.

Because of the regulatory structure, and the long-standing (and getting worse, IMHO) governmental process of "holding someone accountable", there can never be a system that authorizes something for use unless there is some kind of "accountable approval" prior to use.

By that, I mean, that Government needs someone to be held as a responsible/accountable/scapegoat party should anything go wrong.

It's the reason we have 337 requirements, inspections, check-rides, BFRs, lack of electronic engine performance advancements (ala cars) etc. etc. etc. It's also the reason that TSA has created their oppressive requirements for passenger ID and SecureFright.

The issue is more "government accountability requirements" than it is technical capabilities. And that aspect will not change anytime soon.
 
John Collins said:
The jamming can come from your own VHF Com.
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Potentially, yes. Though that would be a blocking type of interference as opposed to spoofing (blocking causes GPS to essentially stop working, spoofing puts up false position info... and yes, it is an issue).

On the other hand, I think most pilots are capable enough to make the determination that there is interference. Just like they are allowed to make the determination regarding PEDs in the plane (for GA flights). For example, I got a "NAV" flag yesterday and was able to troubleshoot and determine that the flag appears to be a wiring issue, not actual nav issue... I was able to continue the flight by referencing and comparing the "flagged" unit to a second panel mount/approved NAVCOM. Yes, I will address the matter before flying IFR.

Yes, I practice flying with VOR and my trusty KNS80 for RNAV routing.

Wishful thinking, it will never happen. Hand held radios with a built in VOR have been around for decades, when do you think they will be approved for IFR flight?
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I submit that handheld VOR receivers are a different matter technically. Why? Wavelength (requires larger antenna and more susceptible to amplitude variations) and display (handheld displays are much smaller than most GPS displays, making them harder to read). That said, I suppose someone could create a portable VOR that's large enough and suitable, but you'll still have the antenna wavelength and faraday shielding issue to overcome. GPS, on the other hand, relies on signals from several satellites (several sources), and the constellation is constantly moving. Even if you lose a couple of satellites, you will usually (and I stress usually) have enough to give valid positioning even at degraded accuracy.

As noted in another post, I don't think that portable GPS will ever be permitted for IFR, but I think it becomes technically possible to have units that would provide sufficient accuracy for lateral guidance. I'd be far less trusting of vertical guidance.
 
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Areeda said:
edit: I meant GX50, the 55 is the VFR version
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Unbeliever said:
Drat! You beat me to it. Curses for sleeping in on a Saturday! :D
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GX55 isn't VFR only - We have a GX55 in one of the club Archers and our installation is certified for IFR Enroute and Terminal (not Approach, obviously.)

Garmin said:
The Apollo GX55 has advanced GPS, sports a high resolution moving map display, and is TSO certified for enroute and terminal operations.
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https://buy.garmin.com/shop/shop.do?pID=6429
 
Tom-D said:
My question asked, wouldn't you like to see those requirements removed?
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You're thinking about this wrong. Moving the unit around in the airplane could cause different undesirable characteristics such as loss of signal, degraded signal, or errors such as Lance describes.

When panel-mounted it is all tested in a fixed position. When it is not fixed in the airplane there are a hell of a lot of variables you have to account for ranging from signal issues, to the quality of the install, to the GPS's location with respect to the pilot, etc. It would be a hell of a feat to convince the FAA that you've developed a system that over-comes all of the above.

I personally would not be comfortable with hand-held, user installed, GPS's being used for approaches. Nor would I be comfortable with hand-held GPS's being used for enroute navigiation unless appropriate certification requirements were developed. I'm not saying the Garmin's we use are inaccurate -- but you never know who will make a ****ty GPS.
 
You may not be comfortable using a hand held for en route nav but care to guess how many are being used that way? I do believe they are not the only method of nav being used since unless your lying about your capabilities when you file your on a V airway and can use the VOR for that but I do believe from what I've seen with various pilots I've talked to they all have hand held GPSs and use them for IFR flights. Now if it gives them a wacky anwser they will look to the other instraments but bottom line the hand held gives you a much better location then a VOR signal. Using them along side other methods is a prudent method of determinng your posotion.
 
jesse said:
You're thinking about this wrong. Moving the unit around in the airplane could cause different undesirable characteristics such as loss of signal, degraded signal, or errors such as Lance describes.

When panel-mounted it is all tested in a fixed position. When it is not fixed in the airplane there are a hell of a lot of variables you have to account for ranging from signal issues, to the quality of the install, to the GPS's location with respect to the pilot, etc. It would be a hell of a feat to convince the FAA that you've developed a system that over-comes all of the above.

I personally would not be comfortable with hand-held, user installed, GPS's being used for approaches. Nor would I be comfortable with hand-held GPS's being used for enroute navigiation unless appropriate certification requirements were developed. I'm not saying the Garmin's we use are inaccurate -- but you never know who will make a ****ty GPS.
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In general I'm in agreement that the performance of a portable GPS isn't good enough for approaches. From what I've seen, the average portable GPS is good enough for enroute and terminal navigation.

I've got a system that feeds WAAS-GPS coordinates to a tablet with moving maps and approach plates. I watch the GPS along with the needles and can see that the GPS position and altitude is always darn close. Not perfect, but close.

We check NAVs every 30 days, why can't we check a GPS? I'm thinkin' the resistance isn't based on current performance but on perceptions of possible problems.
 
Tom-D said:
Do you believe the hand held GPS such as the Garmin 496 should be allowed to be used on IFR enroute and approach as the only means of nav?
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Approach, no we are not ready.
Enroute; maybe. A big maybe. Right now what are folks doing? Getting vectors for 100+ mile legs. "abc center, N123 would like radar vectors direct XYZ, showing a heading of 034 and 1/2 degrees will work" "N123 approved as requested"

If atc can live with the 5 miles deviations a vector can result in, I be they can live with the much less deviation a hhgps will result in.

WILL it happen? Snowball's chance in hell.
 
flyingcheesehead said:
GX55 isn't VFR only - We have a GX55 in one of the club Archers and our installation is certified for IFR Enroute and Terminal (not Approach, obviously.)
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I was giving Joe a gentle poke in the ribs. We're in the same club, and the 172 he was talking about is the one I'm maintenance director of. It's got an IFR GX-50, and not a '55. We kept the database up to date until about March this year, when pilots stopped trying to be proficient in the GX-50 with the proliferation of Garmins in the other club planes, with more Garmins to come.

We have 3 airplanes with Garmins, with a 4th coming soon, one with an IFR GX-50, and one with a VFR GX-55 that was never signed off for IFR and never had a current database.

--Carlos V.
 
I've had hand held GPSs lie to me. In one case it wasn't obvious, except that I was in a car on a highway and knew where I was and that I was not where it insisted that I was. There was no indication of a problem on the unit. In another case, unrealistic speed readiings and changes in readings indicated that the GPS was not happy. I want a ground based reference cross check or at least two GPSs from different manufacturerers to minimize the possibility of a systematic or common mode failure.
 
Graueradler said:
I've had hand held GPSs lie to me.
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I've had an IFR certified panel mount lie to me. The GX50 Carlos mentioned above in fact.

I was doing VFR airwork with a new student pilot, at the altitude we were we would get within a few miles of Burbank Class C and Los Angeles Class B so I like to keep the GPS on the map page.

I look up and it's got me 20 or 30 miles to the south lined up with LAX approaches. A few minutes later we displayed a ground speed of 500 kts or so as it put us back where we were.

Joe
 
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