If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Garmin GPSmap 496 False Terrain Alert
Do any of you fly into KADS with a Garmin GPSmap 496? I'm getting a false
terrain alert when flying the Rwy 15 ILS and am wondering if anyone else has this problem. I'm working with Garmin to resolve this, but so far what they have suggested has not solved the problem. When flying the approach the 496 makes the "500 feet" announcement just as expected. Next, an obstacle warning occurs which is OK, because of the upcoming Addison water tower that is just to the east of the runway. The 496 announces "Warning, Obstacle ahead." Notice that this is just a warning. Next, a Terrain warning occurs. The unit announces "Warning, Terrain ahead." Then it alerts "Pull up. Pull up!" This should not occur. We're exactly on the glide slope, with our normal approach speed of 120 MPH, and a 500 to 600 foot rate of descent. We're at an altitude of approximately 300 feet when the Terrain alert occurs. This is very disconcerting to the passengers, and if I was really flying the approach in IMC, you can be assured that this would be extremely disconcerting to me! At no time during the approach have we gone below the glide slope. Glide slope intercept at JERIT, the FAF at 2000 feet, confirms that our glide slope receiver is OK along with the proper VASI lights as we get closer to the runway during the approach. The 496 is fully updated with the latest software (V3.40 released Jan08) and with the current Jeppesen database and the current Obstacle database. The problem also occurred with the previous software version 3.30 and the prior terrain database. The "nearest airport" criteria is set to the default, "All airports" and the alert look ahead is set to 90 seconds. Everything else is set to the default. The unit does not give a Terrain alert when landing on the opposite runway, 33. Nor does it give a Terrain alert when landing at any other airport. This Terrain alert including the command "Pull up, Pull up" only occurs when flying the ILS 15 approach into KADS during short final. Thus far the support fellow at Garmin (Todd) has verified the pertinent options and settings in my unit, asked that I update to the latest software, and update to the latest terrain database. This hasn't helped, and after checking with the other support technicians, they are stumped. Unfortunately, neither Garmin nor I have been able to get the unit to give a terrain alert in simulator mode, but it does it 100% of the time in the air. Anyone have any ideas? Has anyone flown with the GPSmap 496 into KADS with audio alerts enabled and gotten the same terrain alert? Has anyone experienced a similar problem at any other airport? Thanks, -Ron Gordon Ron "at" GordonFamily.com 1968 V35A Bonanza N8485N |
#2
|
|||
|
|||
Garmin GPSmap 496 False Terrain Alert
In article ,
"Ron Gordon" wrote: Anyone have any ideas? Has anyone flown with the GPSmap 496 into KADS with audio alerts enabled and gotten the same terrain alert? Has anyone experienced a similar problem at any other airport? Have you been able to use a different 496 and see if it gives the same false alert? -- Bob Noel (goodness, please trim replies!!!) |
#3
|
|||
|
|||
Garmin GPSmap 496 False Terrain Alert
Ron,
This is very disconcerting to the passengers, and if I was really flying the approach in IMC, you can be assured that this would be extremely disconcerting to me! I wish you the best for resolving the problem, but as an aside, you're putting way more trust in a non-certified handheld device than I ever would. What you pay for is what you get. The ILS you're following down there IS certified, as is your receiver. I don't think the 496 nor its terrain database were ever designed to do close range avoidance. Trust it when avoind terrain by miles, not tens of feet. -- Thomas Borchert (EDDH) |
#4
|
|||
|
|||
Garmin GPSmap 496 False Terrain Alert
Thomas Borchert wrote:
Ron, This is very disconcerting to the passengers, and if I was really flying the approach in IMC, you can be assured that this would be extremely disconcerting to me! I wish you the best for resolving the problem, but as an aside, you're putting way more trust in a non-certified handheld device than I ever would. What you pay for is what you get. The ILS you're following down there IS certified, as is your receiver. I don't think the 496 nor its terrain database were ever designed to do close range avoidance. Trust it when avoind terrain by miles, not tens of feet. Very well stated. Garmin has two divisions in its product line: 1. IFR avionics 2. Consumer products. The 496 is made by the latter division. It is no different than an automobile navigator; i.e., a nice aid, a toy of sorts, but seriously not a certified IFR tool. |
#5
|
|||
|
|||
Garmin GPSmap 496 False Terrain Alert
Nope. I'm not following the ILS using the 496. I'm following the glide slope
receiver and localizer. The 496 is sitting there as a toy, and complaining that we're about to hit terrain. Even as a non-IFR certified device, Garmin confirms that the unit should not do this. Nor does it do this at any other airport, nor on the flip side runway. This may be a software bug or an error in the terrain database. Will continue to troubleshoot. Thanks, -Ron "Thomas Borchert" wrote in message ... Ron, This is very disconcerting to the passengers, and if I was really flying the approach in IMC, you can be assured that this would be extremely disconcerting to me! I wish you the best for resolving the problem, but as an aside, you're putting way more trust in a non-certified handheld device than I ever would. What you pay for is what you get. The ILS you're following down there IS certified, as is your receiver. I don't think the 496 nor its terrain database were ever designed to do close range avoidance. Trust it when avoind terrain by miles, not tens of feet. -- Thomas Borchert (EDDH) |
#6
|
|||
|
|||
Garmin GPSmap 496 False Terrain Alert
"Ron Gordon" wrote in
. net: Do any of you fly into KADS with a Garmin GPSmap 496? I'm getting a false terrain alert when flying the Rwy 15 ILS and am wondering if anyone else has this problem. I'm working with Garmin to resolve this, but so far what they have suggested has not solved the problem. It might be the calculation used to determine the terrain. All it has is the distance from the satellite and formulae to determine terrain distance. |
#7
|
|||
|
|||
Garmin GPSmap 496 False Terrain Alert
Peter wrote:
If I got the terrain warning in IMC I would go missed immediately even if on an ILS. Anything is possible in terms of conventional instrument failure (I am an electronics engineer and know how avionics work) and would never bet my life on the warning coming from a software bug. Thus, you have created your own emergency based on a piece of consumer electronics. |
#8
|
|||
|
|||
Garmin GPSmap 496 False Terrain Alert
Do any of you fly into KADS with a Garmin GPSmap 496? I'm getting a
false terrain alert when flying the Rwy 15 ILS and am wondering if anyone else has this problem. I'm working with Garmin to resolve this, but so far what they have suggested has not solved the problem. It might be the calculation used to determine the terrain. All it has is the distance from the satellite and formulae to determine terrain distance. Actually the GPS receiver should have terrain (assume in MSL feet) in the database (unknown accuracy of data). The GPS receiver as part of its position determination can calculate the aircraft altitude in the same units and coordinate system and then compare using whatever method the receiver programmers decided upon. Ron Lee |
#9
|
|||
|
|||
Garmin GPSmap 496 False Terrain Alert
Peter wrote:
Think of all those airliners that flew into mountains, killing everybody on board. You can bet that - within the areas contained in the G496 terrain database - every one of those accidents would have been avoided. All of them involved a "very simple" case of loss of SA. Today they have EGPWS, which is a whole lot better than a Garmin handheld. Having said that, I know of at least one airline CFIT that would have been avoided with a Garmin 296/496, that is the TWA crash 21 miles NW of IAD in 1974. But, the bulk of airline CFITs were well inside the FAF and the 296/496 is just not nearly good enough for the resolution required close in. Keep in mind that EGPWS in airliners is augmented by radar altimetes, which become very important inside the FAF. |
#10
|
|||
|
|||
Garmin GPSmap 496 False Terrain Alert
Peter wrote:
But this is a recent development; more than 10-20 years ago "GPWS" was basically just a radar altimeter. I've read a fair few crash reports; the one on Mt Erebus comes to mind in this context, c. 1985. GPWS was mandated in 1975, shortly after the TWA 514 crash. It was installed within a couple of years, so it became common 30 years ago. EGPWS became effective about 10 years ago. |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Garmin Gpsmap 96 | chris | Piloting | 5 | February 9th 07 01:05 AM |
Garmin 296/396 Terrain Data | [email protected] | Instrument Flight Rules | 21 | December 14th 05 02:46 PM |
Garmin GPSMAP 195 | Jonathan Goodish | Aviation Marketplace | 0 | June 21st 05 01:00 AM |
Garmin 430 Terrain Avoidance | endre | Instrument Flight Rules | 5 | July 22nd 04 03:41 AM |
FS: Garmin GPSMAP-196 | Aircraft Mechanic in Tampa | Aviation Marketplace | 3 | March 6th 04 03:19 AM |